/* ** 2004 May 22 ** ** The author disclaims copyright to this source code. In place of ** a legal notice, here is a blessing: ** ** May you do good and not evil. ** May you find forgiveness for yourself and forgive others. ** May you share freely, never taking more than you give. ** ****************************************************************************** ** ** This file contains the VFS implementation for unix-like operating systems ** include Linux, MacOSX, *BSD, QNX, VxWorks, AIX, HPUX, and others. ** ** There are actually several different VFS implementations in this file. ** The differences are in the way that file locking is done. The default ** implementation uses Posix Advisory Locks. Alternative implementations ** use flock(), dot-files, various proprietary locking schemas, or simply ** skip locking all together. ** ** This source file is organized into divisions where the logic for various ** subfunctions is contained within the appropriate division. PLEASE ** KEEP THE STRUCTURE OF THIS FILE INTACT. New code should be placed ** in the correct division and should be clearly labeled. ** ** The layout of divisions is as follows: ** ** * General-purpose declarations and utility functions. ** * Unique file ID logic used by VxWorks. ** * Various locking primitive implementations (all except proxy locking): ** + for Posix Advisory Locks ** + for no-op locks ** + for dot-file locks ** + for flock() locking ** + for named semaphore locks (VxWorks only) ** + for AFP filesystem locks (MacOSX only) ** * sqlite3_file methods not associated with locking. ** * Definitions of sqlite3_io_methods objects for all locking ** methods plus "finder" functions for each locking method. ** * sqlite3_vfs method implementations. ** * Locking primitives for the proxy uber-locking-method. (MacOSX only) ** * Definitions of sqlite3_vfs objects for all locking methods ** plus implementations of sqlite3_os_init() and sqlite3_os_end(). */ #include "sqliteInt.h" #if SQLITE_OS_UNIX /* This file is used on unix only */ /* ** There are various methods for file locking used for concurrency ** control: ** ** 1. POSIX locking (the default), ** 2. No locking, ** 3. Dot-file locking, ** 4. flock() locking, ** 5. AFP locking (OSX only), ** 6. Named POSIX semaphores (VXWorks only), ** 7. proxy locking. (OSX only) ** ** Styles 4, 5, and 7 are only available of SQLITE_ENABLE_LOCKING_STYLE ** is defined to 1. The SQLITE_ENABLE_LOCKING_STYLE also enables automatic ** selection of the appropriate locking style based on the filesystem ** where the database is located. */ #if !defined(SQLITE_ENABLE_LOCKING_STYLE) # if defined(__APPLE__) # define SQLITE_ENABLE_LOCKING_STYLE 1 # else # define SQLITE_ENABLE_LOCKING_STYLE 0 # endif #endif /* ** Define the OS_VXWORKS pre-processor macro to 1 if building on ** vxworks, or 0 otherwise. */ #ifndef OS_VXWORKS # if defined(__RTP__) || defined(_WRS_KERNEL) # define OS_VXWORKS 1 # else # define OS_VXWORKS 0 # endif #endif /* ** These #defines should enable >2GB file support on Posix if the ** underlying operating system supports it. If the OS lacks ** large file support, these should be no-ops. ** ** Large file support can be disabled using the -DSQLITE_DISABLE_LFS switch ** on the compiler command line. This is necessary if you are compiling ** on a recent machine (ex: RedHat 7.2) but you want your code to work ** on an older machine (ex: RedHat 6.0). If you compile on RedHat 7.2 ** without this option, LFS is enable. But LFS does not exist in the kernel ** in RedHat 6.0, so the code won't work. Hence, for maximum binary ** portability you should omit LFS. ** ** The previous paragraph was written in 2005. (This paragraph is written ** on 2008-11-28.) These days, all Linux kernels support large files, so ** you should probably leave LFS enabled. But some embedded platforms might ** lack LFS in which case the SQLITE_DISABLE_LFS macro might still be useful. */ #ifndef SQLITE_DISABLE_LFS # define _LARGE_FILE 1 # ifndef _FILE_OFFSET_BITS # define _FILE_OFFSET_BITS 64 # endif # define _LARGEFILE_SOURCE 1 #endif /* ** standard include files. */ #include #include #include #include #include #include #include #if SQLITE_ENABLE_LOCKING_STYLE # include # if OS_VXWORKS # include # include # else # include # include # include # endif #endif /* SQLITE_ENABLE_LOCKING_STYLE */ /* ** Allowed values of unixFile.fsFlags */ #define SQLITE_FSFLAGS_IS_MSDOS 0x1 /* ** If we are to be thread-safe, include the pthreads header and define ** the SQLITE_UNIX_THREADS macro. */ #if SQLITE_THREADSAFE # include # define SQLITE_UNIX_THREADS 1 #endif /* ** Default permissions when creating a new file */ #ifndef SQLITE_DEFAULT_FILE_PERMISSIONS # define SQLITE_DEFAULT_FILE_PERMISSIONS 0644 #endif /* ** Default permissions when creating auto proxy dir */ #ifndef SQLITE_DEFAULT_PROXYDIR_PERMISSIONS # define SQLITE_DEFAULT_PROXYDIR_PERMISSIONS 0755 #endif /* ** Maximum supported path-length. */ #define MAX_PATHNAME 512 /* ** Only set the lastErrno if the error code is a real error and not ** a normal expected return code of SQLITE_BUSY or SQLITE_OK */ #define IS_LOCK_ERROR(x) ((x != SQLITE_OK) && (x != SQLITE_BUSY)) /* ** Sometimes, after a file handle is closed by SQLite, the file descriptor ** cannot be closed immediately. In these cases, instances of the following ** structure are used to store the file descriptor while waiting for an ** opportunity to either close or reuse it. */ typedef struct UnixUnusedFd UnixUnusedFd; struct UnixUnusedFd { int fd; /* File descriptor to close */ int flags; /* Flags this file descriptor was opened with */ UnixUnusedFd *pNext; /* Next unused file descriptor on same file */ }; /* ** The unixFile structure is subclass of sqlite3_file specific to the unix ** VFS implementations. */ typedef struct unixFile unixFile; struct unixFile { sqlite3_io_methods const *pMethod; /* Always the first entry */ struct unixOpenCnt *pOpen; /* Info about all open fd's on this inode */ struct unixLockInfo *pLock; /* Info about locks on this inode */ int h; /* The file descriptor */ int dirfd; /* File descriptor for the directory */ unsigned char locktype; /* The type of lock held on this fd */ int lastErrno; /* The unix errno from the last I/O error */ void *lockingContext; /* Locking style specific state */ UnixUnusedFd *pUnused; /* Pre-allocated UnixUnusedFd */ int fileFlags; /* Miscellanous flags */ #if SQLITE_ENABLE_LOCKING_STYLE int openFlags; /* The flags specified at open() */ #endif #if SQLITE_ENABLE_LOCKING_STYLE || defined(__APPLE__) unsigned fsFlags; /* cached details from statfs() */ #endif #if SQLITE_THREADSAFE && defined(__linux__) pthread_t tid; /* The thread that "owns" this unixFile */ #endif #if OS_VXWORKS int isDelete; /* Delete on close if true */ struct vxworksFileId *pId; /* Unique file ID */ #endif #ifndef NDEBUG /* The next group of variables are used to track whether or not the ** transaction counter in bytes 24-27 of database files are updated ** whenever any part of the database changes. An assertion fault will ** occur if a file is updated without also updating the transaction ** counter. This test is made to avoid new problems similar to the ** one described by ticket #3584. */ unsigned char transCntrChng; /* True if the transaction counter changed */ unsigned char dbUpdate; /* True if any part of database file changed */ unsigned char inNormalWrite; /* True if in a normal write operation */ #endif #ifdef SQLITE_TEST /* In test mode, increase the size of this structure a bit so that ** it is larger than the struct CrashFile defined in test6.c. */ char aPadding[32]; #endif }; /* ** The following macros define bits in unixFile.fileFlags */ #define SQLITE_WHOLE_FILE_LOCKING 0x0001 /* Use whole-file locking */ /* ** Include code that is common to all os_*.c files */ #include "os_common.h" /* ** Define various macros that are missing from some systems. */ #ifndef O_LARGEFILE # define O_LARGEFILE 0 #endif #ifdef SQLITE_DISABLE_LFS # undef O_LARGEFILE # define O_LARGEFILE 0 #endif #ifndef O_NOFOLLOW # define O_NOFOLLOW 0 #endif #ifndef O_BINARY # define O_BINARY 0 #endif /* ** The DJGPP compiler environment looks mostly like Unix, but it ** lacks the fcntl() system call. So redefine fcntl() to be something ** that always succeeds. This means that locking does not occur under ** DJGPP. But it is DOS - what did you expect? */ #ifdef __DJGPP__ # define fcntl(A,B,C) 0 #endif /* ** The threadid macro resolves to the thread-id or to 0. Used for ** testing and debugging only. */ #if SQLITE_THREADSAFE #define threadid pthread_self() #else #define threadid 0 #endif /* ** Helper functions to obtain and relinquish the global mutex. The ** global mutex is used to protect the unixOpenCnt, unixLockInfo and ** vxworksFileId objects used by this file, all of which may be ** shared by multiple threads. ** ** Function unixMutexHeld() is used to assert() that the global mutex ** is held when required. This function is only used as part of assert() ** statements. e.g. ** ** unixEnterMutex() ** assert( unixMutexHeld() ); ** unixEnterLeave() */ static void unixEnterMutex(void){ sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER)); } static void unixLeaveMutex(void){ sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER)); } #ifdef SQLITE_DEBUG static int unixMutexHeld(void) { return sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER)); } #endif #ifdef SQLITE_DEBUG /* ** Helper function for printing out trace information from debugging ** binaries. This returns the string represetation of the supplied ** integer lock-type. */ static const char *locktypeName(int locktype){ switch( locktype ){ case NO_LOCK: return "NONE"; case SHARED_LOCK: return "SHARED"; case RESERVED_LOCK: return "RESERVED"; case PENDING_LOCK: return "PENDING"; case EXCLUSIVE_LOCK: return "EXCLUSIVE"; } return "ERROR"; } #endif #ifdef SQLITE_LOCK_TRACE /* ** Print out information about all locking operations. ** ** This routine is used for troubleshooting locks on multithreaded ** platforms. Enable by compiling with the -DSQLITE_LOCK_TRACE ** command-line option on the compiler. This code is normally ** turned off. */ static int lockTrace(int fd, int op, struct flock *p){ char *zOpName, *zType; int s; int savedErrno; if( op==F_GETLK ){ zOpName = "GETLK"; }else if( op==F_SETLK ){ zOpName = "SETLK"; }else{ s = fcntl(fd, op, p); sqlite3DebugPrintf("fcntl unknown %d %d %d\n", fd, op, s); return s; } if( p->l_type==F_RDLCK ){ zType = "RDLCK"; }else if( p->l_type==F_WRLCK ){ zType = "WRLCK"; }else if( p->l_type==F_UNLCK ){ zType = "UNLCK"; }else{ assert( 0 ); } assert( p->l_whence==SEEK_SET ); s = fcntl(fd, op, p); savedErrno = errno; sqlite3DebugPrintf("fcntl %d %d %s %s %d %d %d %d\n", threadid, fd, zOpName, zType, (int)p->l_start, (int)p->l_len, (int)p->l_pid, s); if( s==(-1) && op==F_SETLK && (p->l_type==F_RDLCK || p->l_type==F_WRLCK) ){ struct flock l2; l2 = *p; fcntl(fd, F_GETLK, &l2); if( l2.l_type==F_RDLCK ){ zType = "RDLCK"; }else if( l2.l_type==F_WRLCK ){ zType = "WRLCK"; }else if( l2.l_type==F_UNLCK ){ zType = "UNLCK"; }else{ assert( 0 ); } sqlite3DebugPrintf("fcntl-failure-reason: %s %d %d %d\n", zType, (int)l2.l_start, (int)l2.l_len, (int)l2.l_pid); } errno = savedErrno; return s; } #define fcntl lockTrace #endif /* SQLITE_LOCK_TRACE */ /* ** This routine translates a standard POSIX errno code into something ** useful to the clients of the sqlite3 functions. Specifically, it is ** intended to translate a variety of "try again" errors into SQLITE_BUSY ** and a variety of "please close the file descriptor NOW" errors into ** SQLITE_IOERR ** ** Errors during initialization of locks, or file system support for locks, ** should handle ENOLCK, ENOTSUP, EOPNOTSUPP separately. */ static int sqliteErrorFromPosixError(int posixError, int sqliteIOErr) { switch (posixError) { case 0: return SQLITE_OK; case EAGAIN: case ETIMEDOUT: case EBUSY: case EINTR: case ENOLCK: /* random NFS retry error, unless during file system support * introspection, in which it actually means what it says */ return SQLITE_BUSY; case EACCES: /* EACCES is like EAGAIN during locking operations, but not any other time*/ if( (sqliteIOErr == SQLITE_IOERR_LOCK) || (sqliteIOErr == SQLITE_IOERR_UNLOCK) || (sqliteIOErr == SQLITE_IOERR_RDLOCK) || (sqliteIOErr == SQLITE_IOERR_CHECKRESERVEDLOCK) ){ return SQLITE_BUSY; } /* else fall through */ case EPERM: return SQLITE_PERM; case EDEADLK: return SQLITE_IOERR_BLOCKED; #if EOPNOTSUPP!=ENOTSUP case EOPNOTSUPP: /* something went terribly awry, unless during file system support * introspection, in which it actually means what it says */ #endif #ifdef ENOTSUP case ENOTSUP: /* invalid fd, unless during file system support introspection, in which * it actually means what it says */ #endif case EIO: case EBADF: case EINVAL: case ENOTCONN: case ENODEV: case ENXIO: case ENOENT: case ESTALE: case ENOSYS: /* these should force the client to close the file and reconnect */ default: return sqliteIOErr; } } /****************************************************************************** ****************** Begin Unique File ID Utility Used By VxWorks *************** ** ** On most versions of unix, we can get a unique ID for a file by concatenating ** the device number and the inode number. But this does not work on VxWorks. ** On VxWorks, a unique file id must be based on the canonical filename. ** ** A pointer to an instance of the following structure can be used as a ** unique file ID in VxWorks. Each instance of this structure contains ** a copy of the canonical filename. There is also a reference count. ** The structure is reclaimed when the number of pointers to it drops to ** zero. ** ** There are never very many files open at one time and lookups are not ** a performance-critical path, so it is sufficient to put these ** structures on a linked list. */ struct vxworksFileId { struct vxworksFileId *pNext; /* Next in a list of them all */ int nRef; /* Number of references to this one */ int nName; /* Length of the zCanonicalName[] string */ char *zCanonicalName; /* Canonical filename */ }; #if OS_VXWORKS /* ** All unique filenames are held on a linked list headed by this ** variable: */ static struct vxworksFileId *vxworksFileList = 0; /* ** Simplify a filename into its canonical form ** by making the following changes: ** ** * removing any trailing and duplicate / ** * convert /./ into just / ** * convert /A/../ where A is any simple name into just / ** ** Changes are made in-place. Return the new name length. ** ** The original filename is in z[0..n-1]. Return the number of ** characters in the simplified name. */ static int vxworksSimplifyName(char *z, int n){ int i, j; while( n>1 && z[n-1]=='/' ){ n--; } for(i=j=0; i0 && z[j-1]!='/' ){ j--; } if( j>0 ){ j--; } i += 2; continue; } } z[j++] = z[i]; } z[j] = 0; return j; } /* ** Find a unique file ID for the given absolute pathname. Return ** a pointer to the vxworksFileId object. This pointer is the unique ** file ID. ** ** The nRef field of the vxworksFileId object is incremented before ** the object is returned. A new vxworksFileId object is created ** and added to the global list if necessary. ** ** If a memory allocation error occurs, return NULL. */ static struct vxworksFileId *vxworksFindFileId(const char *zAbsoluteName){ struct vxworksFileId *pNew; /* search key and new file ID */ struct vxworksFileId *pCandidate; /* For looping over existing file IDs */ int n; /* Length of zAbsoluteName string */ assert( zAbsoluteName[0]=='/' ); n = (int)strlen(zAbsoluteName); pNew = sqlite3_malloc( sizeof(*pNew) + (n+1) ); if( pNew==0 ) return 0; pNew->zCanonicalName = (char*)&pNew[1]; memcpy(pNew->zCanonicalName, zAbsoluteName, n+1); n = vxworksSimplifyName(pNew->zCanonicalName, n); /* Search for an existing entry that matching the canonical name. ** If found, increment the reference count and return a pointer to ** the existing file ID. */ unixEnterMutex(); for(pCandidate=vxworksFileList; pCandidate; pCandidate=pCandidate->pNext){ if( pCandidate->nName==n && memcmp(pCandidate->zCanonicalName, pNew->zCanonicalName, n)==0 ){ sqlite3_free(pNew); pCandidate->nRef++; unixLeaveMutex(); return pCandidate; } } /* No match was found. We will make a new file ID */ pNew->nRef = 1; pNew->nName = n; pNew->pNext = vxworksFileList; vxworksFileList = pNew; unixLeaveMutex(); return pNew; } /* ** Decrement the reference count on a vxworksFileId object. Free ** the object when the reference count reaches zero. */ static void vxworksReleaseFileId(struct vxworksFileId *pId){ unixEnterMutex(); assert( pId->nRef>0 ); pId->nRef--; if( pId->nRef==0 ){ struct vxworksFileId **pp; for(pp=&vxworksFileList; *pp && *pp!=pId; pp = &((*pp)->pNext)){} assert( *pp==pId ); *pp = pId->pNext; sqlite3_free(pId); } unixLeaveMutex(); } #endif /* OS_VXWORKS */ /*************** End of Unique File ID Utility Used By VxWorks **************** ******************************************************************************/ /****************************************************************************** *************************** Posix Advisory Locking **************************** ** ** POSIX advisory locks are broken by design. ANSI STD 1003.1 (1996) ** section 6.5.2.2 lines 483 through 490 specify that when a process ** sets or clears a lock, that operation overrides any prior locks set ** by the same process. It does not explicitly say so, but this implies ** that it overrides locks set by the same process using a different ** file descriptor. Consider this test case: ** ** int fd1 = open("./file1", O_RDWR|O_CREAT, 0644); ** int fd2 = open("./file2", O_RDWR|O_CREAT, 0644); ** ** Suppose ./file1 and ./file2 are really the same file (because ** one is a hard or symbolic link to the other) then if you set ** an exclusive lock on fd1, then try to get an exclusive lock ** on fd2, it works. I would have expected the second lock to ** fail since there was already a lock on the file due to fd1. ** But not so. Since both locks came from the same process, the ** second overrides the first, even though they were on different ** file descriptors opened on different file names. ** ** This means that we cannot use POSIX locks to synchronize file access ** among competing threads of the same process. POSIX locks will work fine ** to synchronize access for threads in separate processes, but not ** threads within the same process. ** ** To work around the problem, SQLite has to manage file locks internally ** on its own. Whenever a new database is opened, we have to find the ** specific inode of the database file (the inode is determined by the ** st_dev and st_ino fields of the stat structure that fstat() fills in) ** and check for locks already existing on that inode. When locks are ** created or removed, we have to look at our own internal record of the ** locks to see if another thread has previously set a lock on that same ** inode. ** ** (Aside: The use of inode numbers as unique IDs does not work on VxWorks. ** For VxWorks, we have to use the alternative unique ID system based on ** canonical filename and implemented in the previous division.) ** ** The sqlite3_file structure for POSIX is no longer just an integer file ** descriptor. It is now a structure that holds the integer file ** descriptor and a pointer to a structure that describes the internal ** locks on the corresponding inode. There is one locking structure ** per inode, so if the same inode is opened twice, both unixFile structures ** point to the same locking structure. The locking structure keeps ** a reference count (so we will know when to delete it) and a "cnt" ** field that tells us its internal lock status. cnt==0 means the ** file is unlocked. cnt==-1 means the file has an exclusive lock. ** cnt>0 means there are cnt shared locks on the file. ** ** Any attempt to lock or unlock a file first checks the locking ** structure. The fcntl() system call is only invoked to set a ** POSIX lock if the internal lock structure transitions between ** a locked and an unlocked state. ** ** But wait: there are yet more problems with POSIX advisory locks. ** ** If you close a file descriptor that points to a file that has locks, ** all locks on that file that are owned by the current process are ** released. To work around this problem, each unixFile structure contains ** a pointer to an unixOpenCnt structure. There is one unixOpenCnt structure ** per open inode, which means that multiple unixFile can point to a single ** unixOpenCnt. When an attempt is made to close an unixFile, if there are ** other unixFile open on the same inode that are holding locks, the call ** to close() the file descriptor is deferred until all of the locks clear. ** The unixOpenCnt structure keeps a list of file descriptors that need to ** be closed and that list is walked (and cleared) when the last lock ** clears. ** ** Yet another problem: LinuxThreads do not play well with posix locks. ** ** Many older versions of linux use the LinuxThreads library which is ** not posix compliant. Under LinuxThreads, a lock created by thread ** A cannot be modified or overridden by a different thread B. ** Only thread A can modify the lock. Locking behavior is correct ** if the appliation uses the newer Native Posix Thread Library (NPTL) ** on linux - with NPTL a lock created by thread A can override locks ** in thread B. But there is no way to know at compile-time which ** threading library is being used. So there is no way to know at ** compile-time whether or not thread A can override locks on thread B. ** We have to do a run-time check to discover the behavior of the ** current process. ** ** On systems where thread A is unable to modify locks created by ** thread B, we have to keep track of which thread created each ** lock. Hence there is an extra field in the key to the unixLockInfo ** structure to record this information. And on those systems it ** is illegal to begin a transaction in one thread and finish it ** in another. For this latter restriction, there is no work-around. ** It is a limitation of LinuxThreads. */ /* ** Set or check the unixFile.tid field. This field is set when an unixFile ** is first opened. All subsequent uses of the unixFile verify that the ** same thread is operating on the unixFile. Some operating systems do ** not allow locks to be overridden by other threads and that restriction ** means that sqlite3* database handles cannot be moved from one thread ** to another while locks are held. ** ** Version 3.3.1 (2006-01-15): unixFile can be moved from one thread to ** another as long as we are running on a system that supports threads ** overriding each others locks (which is now the most common behavior) ** or if no locks are held. But the unixFile.pLock field needs to be ** recomputed because its key includes the thread-id. See the ** transferOwnership() function below for additional information */ #if SQLITE_THREADSAFE && defined(__linux__) # define SET_THREADID(X) (X)->tid = pthread_self() # define CHECK_THREADID(X) (threadsOverrideEachOthersLocks==0 && \ !pthread_equal((X)->tid, pthread_self())) #else # define SET_THREADID(X) # define CHECK_THREADID(X) 0 #endif /* ** An instance of the following structure serves as the key used ** to locate a particular unixOpenCnt structure given its inode. This ** is the same as the unixLockKey except that the thread ID is omitted. */ struct unixFileId { dev_t dev; /* Device number */ #if OS_VXWORKS struct vxworksFileId *pId; /* Unique file ID for vxworks. */ #else ino_t ino; /* Inode number */ #endif }; /* ** An instance of the following structure serves as the key used ** to locate a particular unixLockInfo structure given its inode. ** ** If threads cannot override each others locks (LinuxThreads), then we ** set the unixLockKey.tid field to the thread ID. If threads can override ** each others locks (Posix and NPTL) then tid is always set to zero. ** tid is omitted if we compile without threading support or on an OS ** other than linux. */ struct unixLockKey { struct unixFileId fid; /* Unique identifier for the file */ #if SQLITE_THREADSAFE && defined(__linux__) pthread_t tid; /* Thread ID of lock owner. Zero if not using LinuxThreads */ #endif }; /* ** An instance of the following structure is allocated for each open ** inode. Or, on LinuxThreads, there is one of these structures for ** each inode opened by each thread. ** ** A single inode can have multiple file descriptors, so each unixFile ** structure contains a pointer to an instance of this object and this ** object keeps a count of the number of unixFile pointing to it. */ struct unixLockInfo { struct unixLockKey lockKey; /* The lookup key */ int cnt; /* Number of SHARED locks held */ int locktype; /* One of SHARED_LOCK, RESERVED_LOCK etc. */ int nRef; /* Number of pointers to this structure */ #if defined(SQLITE_ENABLE_LOCKING_STYLE) unsigned long long sharedByte; /* for AFP simulated shared lock */ #endif struct unixLockInfo *pNext; /* List of all unixLockInfo objects */ struct unixLockInfo *pPrev; /* .... doubly linked */ }; /* ** An instance of the following structure is allocated for each open ** inode. This structure keeps track of the number of locks on that ** inode. If a close is attempted against an inode that is holding ** locks, the close is deferred until all locks clear by adding the ** file descriptor to be closed to the pending list. ** ** TODO: Consider changing this so that there is only a single file ** descriptor for each open file, even when it is opened multiple times. ** The close() system call would only occur when the last database ** using the file closes. */ struct unixOpenCnt { struct unixFileId fileId; /* The lookup key */ int nRef; /* Number of pointers to this structure */ int nLock; /* Number of outstanding locks */ UnixUnusedFd *pUnused; /* Unused file descriptors to close */ #if OS_VXWORKS sem_t *pSem; /* Named POSIX semaphore */ char aSemName[MAX_PATHNAME+2]; /* Name of that semaphore */ #endif struct unixOpenCnt *pNext, *pPrev; /* List of all unixOpenCnt objects */ }; /* ** Lists of all unixLockInfo and unixOpenCnt objects. These used to be hash ** tables. But the number of objects is rarely more than a dozen and ** never exceeds a few thousand. And lookup is not on a critical ** path so a simple linked list will suffice. */ static struct unixLockInfo *lockList = 0; static struct unixOpenCnt *openList = 0; /* ** This variable remembers whether or not threads can override each others ** locks. ** ** 0: No. Threads cannot override each others locks. (LinuxThreads) ** 1: Yes. Threads can override each others locks. (Posix & NLPT) ** -1: We don't know yet. ** ** On some systems, we know at compile-time if threads can override each ** others locks. On those systems, the SQLITE_THREAD_OVERRIDE_LOCK macro ** will be set appropriately. On other systems, we have to check at ** runtime. On these latter systems, SQLTIE_THREAD_OVERRIDE_LOCK is ** undefined. ** ** This variable normally has file scope only. But during testing, we make ** it a global so that the test code can change its value in order to verify ** that the right stuff happens in either case. */ #if SQLITE_THREADSAFE && defined(__linux__) # ifndef SQLITE_THREAD_OVERRIDE_LOCK # define SQLITE_THREAD_OVERRIDE_LOCK -1 # endif # ifdef SQLITE_TEST int threadsOverrideEachOthersLocks = SQLITE_THREAD_OVERRIDE_LOCK; # else static int threadsOverrideEachOthersLocks = SQLITE_THREAD_OVERRIDE_LOCK; # endif #endif /* ** This structure holds information passed into individual test ** threads by the testThreadLockingBehavior() routine. */ struct threadTestData { int fd; /* File to be locked */ struct flock lock; /* The locking operation */ int result; /* Result of the locking operation */ }; #if SQLITE_THREADSAFE && defined(__linux__) /* ** This function is used as the main routine for a thread launched by ** testThreadLockingBehavior(). It tests whether the shared-lock obtained ** by the main thread in testThreadLockingBehavior() conflicts with a ** hypothetical write-lock obtained by this thread on the same file. ** ** The write-lock is not actually acquired, as this is not possible if ** the file is open in read-only mode (see ticket #3472). */ static void *threadLockingTest(void *pArg){ struct threadTestData *pData = (struct threadTestData*)pArg; pData->result = fcntl(pData->fd, F_GETLK, &pData->lock); return pArg; } #endif /* SQLITE_THREADSAFE && defined(__linux__) */ #if SQLITE_THREADSAFE && defined(__linux__) /* ** This procedure attempts to determine whether or not threads ** can override each others locks then sets the ** threadsOverrideEachOthersLocks variable appropriately. */ static void testThreadLockingBehavior(int fd_orig){ int fd; int rc; struct threadTestData d; struct flock l; pthread_t t; fd = dup(fd_orig); if( fd<0 ) return; memset(&l, 0, sizeof(l)); l.l_type = F_RDLCK; l.l_len = 1; l.l_start = 0; l.l_whence = SEEK_SET; rc = fcntl(fd_orig, F_SETLK, &l); if( rc!=0 ) return; memset(&d, 0, sizeof(d)); d.fd = fd; d.lock = l; d.lock.l_type = F_WRLCK; if( pthread_create(&t, 0, threadLockingTest, &d)==0 ){ pthread_join(t, 0); } close(fd); if( d.result!=0 ) return; threadsOverrideEachOthersLocks = (d.lock.l_type==F_UNLCK); } #endif /* SQLITE_THREADSAFE && defined(__linux__) */ /* ** Release a unixLockInfo structure previously allocated by findLockInfo(). ** ** The mutex entered using the unixEnterMutex() function must be held ** when this function is called. */ static void releaseLockInfo(struct unixLockInfo *pLock){ assert( unixMutexHeld() ); if( pLock ){ pLock->nRef--; if( pLock->nRef==0 ){ if( pLock->pPrev ){ assert( pLock->pPrev->pNext==pLock ); pLock->pPrev->pNext = pLock->pNext; }else{ assert( lockList==pLock ); lockList = pLock->pNext; } if( pLock->pNext ){ assert( pLock->pNext->pPrev==pLock ); pLock->pNext->pPrev = pLock->pPrev; } sqlite3_free(pLock); } } } /* ** Release a unixOpenCnt structure previously allocated by findLockInfo(). ** ** The mutex entered using the unixEnterMutex() function must be held ** when this function is called. */ static void releaseOpenCnt(struct unixOpenCnt *pOpen){ assert( unixMutexHeld() ); if( pOpen ){ pOpen->nRef--; if( pOpen->nRef==0 ){ if( pOpen->pPrev ){ assert( pOpen->pPrev->pNext==pOpen ); pOpen->pPrev->pNext = pOpen->pNext; }else{ assert( openList==pOpen ); openList = pOpen->pNext; } if( pOpen->pNext ){ assert( pOpen->pNext->pPrev==pOpen ); pOpen->pNext->pPrev = pOpen->pPrev; } #if SQLITE_THREADSAFE && defined(__linux__) assert( !pOpen->pUnused || threadsOverrideEachOthersLocks==0 ); #endif /* If pOpen->pUnused is not null, then memory and file-descriptors ** are leaked. ** ** This will only happen if, under Linuxthreads, the user has opened ** a transaction in one thread, then attempts to close the database ** handle from another thread (without first unlocking the db file). ** This is a misuse. */ sqlite3_free(pOpen); } } } /* ** Given a file descriptor, locate unixLockInfo and unixOpenCnt structures that ** describes that file descriptor. Create new ones if necessary. The ** return values might be uninitialized if an error occurs. ** ** The mutex entered using the unixEnterMutex() function must be held ** when this function is called. ** ** Return an appropriate error code. */ static int findLockInfo( unixFile *pFile, /* Unix file with file desc used in the key */ struct unixLockInfo **ppLock, /* Return the unixLockInfo structure here */ struct unixOpenCnt **ppOpen /* Return the unixOpenCnt structure here */ ){ int rc; /* System call return code */ int fd; /* The file descriptor for pFile */ struct unixLockKey lockKey; /* Lookup key for the unixLockInfo structure */ struct unixFileId fileId; /* Lookup key for the unixOpenCnt struct */ struct stat statbuf; /* Low-level file information */ struct unixLockInfo *pLock = 0;/* Candidate unixLockInfo object */ struct unixOpenCnt *pOpen; /* Candidate unixOpenCnt object */ assert( unixMutexHeld() ); /* Get low-level information about the file that we can used to ** create a unique name for the file. */ fd = pFile->h; rc = fstat(fd, &statbuf); if( rc!=0 ){ pFile->lastErrno = errno; #ifdef EOVERFLOW if( pFile->lastErrno==EOVERFLOW ) return SQLITE_NOLFS; #endif return SQLITE_IOERR; } #ifdef __APPLE__ /* On OS X on an msdos filesystem, the inode number is reported ** incorrectly for zero-size files. See ticket #3260. To work ** around this problem (we consider it a bug in OS X, not SQLite) ** we always increase the file size to 1 by writing a single byte ** prior to accessing the inode number. The one byte written is ** an ASCII 'S' character which also happens to be the first byte ** in the header of every SQLite database. In this way, if there ** is a race condition such that another thread has already populated ** the first page of the database, no damage is done. */ if( statbuf.st_size==0 && (pFile->fsFlags & SQLITE_FSFLAGS_IS_MSDOS)!=0 ){ rc = write(fd, "S", 1); if( rc!=1 ){ pFile->lastErrno = errno; return SQLITE_IOERR; } rc = fstat(fd, &statbuf); if( rc!=0 ){ pFile->lastErrno = errno; return SQLITE_IOERR; } } #endif memset(&lockKey, 0, sizeof(lockKey)); lockKey.fid.dev = statbuf.st_dev; #if OS_VXWORKS lockKey.fid.pId = pFile->pId; #else lockKey.fid.ino = statbuf.st_ino; #endif #if SQLITE_THREADSAFE && defined(__linux__) if( threadsOverrideEachOthersLocks<0 ){ testThreadLockingBehavior(fd); } lockKey.tid = threadsOverrideEachOthersLocks ? 0 : pthread_self(); #endif fileId = lockKey.fid; if( ppLock!=0 ){ pLock = lockList; while( pLock && memcmp(&lockKey, &pLock->lockKey, sizeof(lockKey)) ){ pLock = pLock->pNext; } if( pLock==0 ){ pLock = sqlite3_malloc( sizeof(*pLock) ); if( pLock==0 ){ rc = SQLITE_NOMEM; goto exit_findlockinfo; } memcpy(&pLock->lockKey,&lockKey,sizeof(lockKey)); pLock->nRef = 1; pLock->cnt = 0; pLock->locktype = 0; #if defined(SQLITE_ENABLE_LOCKING_STYLE) pLock->sharedByte = 0; #endif pLock->pNext = lockList; pLock->pPrev = 0; if( lockList ) lockList->pPrev = pLock; lockList = pLock; }else{ pLock->nRef++; } *ppLock = pLock; } if( ppOpen!=0 ){ pOpen = openList; while( pOpen && memcmp(&fileId, &pOpen->fileId, sizeof(fileId)) ){ pOpen = pOpen->pNext; } if( pOpen==0 ){ pOpen = sqlite3_malloc( sizeof(*pOpen) ); if( pOpen==0 ){ releaseLockInfo(pLock); rc = SQLITE_NOMEM; goto exit_findlockinfo; } memset(pOpen, 0, sizeof(*pOpen)); pOpen->fileId = fileId; pOpen->nRef = 1; pOpen->pNext = openList; if( openList ) openList->pPrev = pOpen; openList = pOpen; }else{ pOpen->nRef++; } *ppOpen = pOpen; } exit_findlockinfo: return rc; } /* ** If we are currently in a different thread than the thread that the ** unixFile argument belongs to, then transfer ownership of the unixFile ** over to the current thread. ** ** A unixFile is only owned by a thread on systems that use LinuxThreads. ** ** Ownership transfer is only allowed if the unixFile is currently unlocked. ** If the unixFile is locked and an ownership is wrong, then return ** SQLITE_MISUSE. SQLITE_OK is returned if everything works. */ #if SQLITE_THREADSAFE && defined(__linux__) static int transferOwnership(unixFile *pFile){ int rc; pthread_t hSelf; if( threadsOverrideEachOthersLocks ){ /* Ownership transfers not needed on this system */ return SQLITE_OK; } hSelf = pthread_self(); if( pthread_equal(pFile->tid, hSelf) ){ /* We are still in the same thread */ OSTRACE1("No-transfer, same thread\n"); return SQLITE_OK; } if( pFile->locktype!=NO_LOCK ){ /* We cannot change ownership while we are holding a lock! */ return SQLITE_MISUSE; } OSTRACE4("Transfer ownership of %d from %d to %d\n", pFile->h, pFile->tid, hSelf); pFile->tid = hSelf; if (pFile->pLock != NULL) { releaseLockInfo(pFile->pLock); rc = findLockInfo(pFile, &pFile->pLock, 0); OSTRACE5("LOCK %d is now %s(%s,%d)\n", pFile->h, locktypeName(pFile->locktype), locktypeName(pFile->pLock->locktype), pFile->pLock->cnt); return rc; } else { return SQLITE_OK; } } #else /* if not SQLITE_THREADSAFE */ /* On single-threaded builds, ownership transfer is a no-op */ # define transferOwnership(X) SQLITE_OK #endif /* SQLITE_THREADSAFE */ /* ** This routine checks if there is a RESERVED lock held on the specified ** file by this or any other process. If such a lock is held, set *pResOut ** to a non-zero value otherwise *pResOut is set to zero. The return value ** is set to SQLITE_OK unless an I/O error occurs during lock checking. */ static int unixCheckReservedLock(sqlite3_file *id, int *pResOut){ int rc = SQLITE_OK; int reserved = 0; unixFile *pFile = (unixFile*)id; SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; ); assert( pFile ); unixEnterMutex(); /* Because pFile->pLock is shared across threads */ /* Check if a thread in this process holds such a lock */ if( pFile->pLock->locktype>SHARED_LOCK ){ reserved = 1; } /* Otherwise see if some other process holds it. */ #ifndef __DJGPP__ if( !reserved ){ struct flock lock; lock.l_whence = SEEK_SET; lock.l_start = RESERVED_BYTE; lock.l_len = 1; lock.l_type = F_WRLCK; if (-1 == fcntl(pFile->h, F_GETLK, &lock)) { int tErrno = errno; rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_CHECKRESERVEDLOCK); pFile->lastErrno = tErrno; } else if( lock.l_type!=F_UNLCK ){ reserved = 1; } } #endif unixLeaveMutex(); OSTRACE4("TEST WR-LOCK %d %d %d (unix)\n", pFile->h, rc, reserved); *pResOut = reserved; return rc; } /* ** Lock the file with the lock specified by parameter locktype - one ** of the following: ** ** (1) SHARED_LOCK ** (2) RESERVED_LOCK ** (3) PENDING_LOCK ** (4) EXCLUSIVE_LOCK ** ** Sometimes when requesting one lock state, additional lock states ** are inserted in between. The locking might fail on one of the later ** transitions leaving the lock state different from what it started but ** still short of its goal. The following chart shows the allowed ** transitions and the inserted intermediate states: ** ** UNLOCKED -> SHARED ** SHARED -> RESERVED ** SHARED -> (PENDING) -> EXCLUSIVE ** RESERVED -> (PENDING) -> EXCLUSIVE ** PENDING -> EXCLUSIVE ** ** This routine will only increase a lock. Use the sqlite3OsUnlock() ** routine to lower a locking level. */ static int unixLock(sqlite3_file *id, int locktype){ /* The following describes the implementation of the various locks and ** lock transitions in terms of the POSIX advisory shared and exclusive ** lock primitives (called read-locks and write-locks below, to avoid ** confusion with SQLite lock names). The algorithms are complicated ** slightly in order to be compatible with windows systems simultaneously ** accessing the same database file, in case that is ever required. ** ** Symbols defined in os.h indentify the 'pending byte' and the 'reserved ** byte', each single bytes at well known offsets, and the 'shared byte ** range', a range of 510 bytes at a well known offset. ** ** To obtain a SHARED lock, a read-lock is obtained on the 'pending ** byte'. If this is successful, a random byte from the 'shared byte ** range' is read-locked and the lock on the 'pending byte' released. ** ** A process may only obtain a RESERVED lock after it has a SHARED lock. ** A RESERVED lock is implemented by grabbing a write-lock on the ** 'reserved byte'. ** ** A process may only obtain a PENDING lock after it has obtained a ** SHARED lock. A PENDING lock is implemented by obtaining a write-lock ** on the 'pending byte'. This ensures that no new SHARED locks can be ** obtained, but existing SHARED locks are allowed to persist. A process ** does not have to obtain a RESERVED lock on the way to a PENDING lock. ** This property is used by the algorithm for rolling back a journal file ** after a crash. ** ** An EXCLUSIVE lock, obtained after a PENDING lock is held, is ** implemented by obtaining a write-lock on the entire 'shared byte ** range'. Since all other locks require a read-lock on one of the bytes ** within this range, this ensures that no other locks are held on the ** database. ** ** The reason a single byte cannot be used instead of the 'shared byte ** range' is that some versions of windows do not support read-locks. By ** locking a random byte from a range, concurrent SHARED locks may exist ** even if the locking primitive used is always a write-lock. */ int rc = SQLITE_OK; unixFile *pFile = (unixFile*)id; struct unixLockInfo *pLock = pFile->pLock; struct flock lock; int s = 0; int tErrno; assert( pFile ); OSTRACE7("LOCK %d %s was %s(%s,%d) pid=%d (unix)\n", pFile->h, locktypeName(locktype), locktypeName(pFile->locktype), locktypeName(pLock->locktype), pLock->cnt , getpid()); /* If there is already a lock of this type or more restrictive on the ** unixFile, do nothing. Don't use the end_lock: exit path, as ** unixEnterMutex() hasn't been called yet. */ if( pFile->locktype>=locktype ){ OSTRACE3("LOCK %d %s ok (already held) (unix)\n", pFile->h, locktypeName(locktype)); return SQLITE_OK; } /* Make sure the locking sequence is correct. ** (1) We never move from unlocked to anything higher than shared lock. ** (2) SQLite never explicitly requests a pendig lock. ** (3) A shared lock is always held when a reserve lock is requested. */ assert( pFile->locktype!=NO_LOCK || locktype==SHARED_LOCK ); assert( locktype!=PENDING_LOCK ); assert( locktype!=RESERVED_LOCK || pFile->locktype==SHARED_LOCK ); /* This mutex is needed because pFile->pLock is shared across threads */ unixEnterMutex(); /* Make sure the current thread owns the pFile. */ rc = transferOwnership(pFile); if( rc!=SQLITE_OK ){ unixLeaveMutex(); return rc; } pLock = pFile->pLock; /* If some thread using this PID has a lock via a different unixFile* ** handle that precludes the requested lock, return BUSY. */ if( (pFile->locktype!=pLock->locktype && (pLock->locktype>=PENDING_LOCK || locktype>SHARED_LOCK)) ){ rc = SQLITE_BUSY; goto end_lock; } /* If a SHARED lock is requested, and some thread using this PID already ** has a SHARED or RESERVED lock, then increment reference counts and ** return SQLITE_OK. */ if( locktype==SHARED_LOCK && (pLock->locktype==SHARED_LOCK || pLock->locktype==RESERVED_LOCK) ){ assert( locktype==SHARED_LOCK ); assert( pFile->locktype==0 ); assert( pLock->cnt>0 ); pFile->locktype = SHARED_LOCK; pLock->cnt++; pFile->pOpen->nLock++; goto end_lock; } /* A PENDING lock is needed before acquiring a SHARED lock and before ** acquiring an EXCLUSIVE lock. For the SHARED lock, the PENDING will ** be released. */ lock.l_len = 1L; lock.l_whence = SEEK_SET; if( locktype==SHARED_LOCK || (locktype==EXCLUSIVE_LOCK && pFile->locktypeh, F_SETLK, &lock); if( s==(-1) ){ tErrno = errno; rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK); if( IS_LOCK_ERROR(rc) ){ pFile->lastErrno = tErrno; } goto end_lock; } } /* If control gets to this point, then actually go ahead and make ** operating system calls for the specified lock. */ if( locktype==SHARED_LOCK ){ assert( pLock->cnt==0 ); assert( pLock->locktype==0 ); /* Now get the read-lock */ lock.l_start = SHARED_FIRST; lock.l_len = SHARED_SIZE; if( (s = fcntl(pFile->h, F_SETLK, &lock))==(-1) ){ tErrno = errno; } /* Drop the temporary PENDING lock */ lock.l_start = PENDING_BYTE; lock.l_len = 1L; lock.l_type = F_UNLCK; if( fcntl(pFile->h, F_SETLK, &lock)!=0 ){ if( s != -1 ){ /* This could happen with a network mount */ tErrno = errno; rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK); if( IS_LOCK_ERROR(rc) ){ pFile->lastErrno = tErrno; } goto end_lock; } } if( s==(-1) ){ rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK); if( IS_LOCK_ERROR(rc) ){ pFile->lastErrno = tErrno; } }else{ pFile->locktype = SHARED_LOCK; pFile->pOpen->nLock++; pLock->cnt = 1; } }else if( locktype==EXCLUSIVE_LOCK && pLock->cnt>1 ){ /* We are trying for an exclusive lock but another thread in this ** same process is still holding a shared lock. */ rc = SQLITE_BUSY; }else{ /* The request was for a RESERVED or EXCLUSIVE lock. It is ** assumed that there is a SHARED or greater lock on the file ** already. */ assert( 0!=pFile->locktype ); lock.l_type = F_WRLCK; switch( locktype ){ case RESERVED_LOCK: lock.l_start = RESERVED_BYTE; break; case EXCLUSIVE_LOCK: lock.l_start = SHARED_FIRST; lock.l_len = SHARED_SIZE; break; default: assert(0); } s = fcntl(pFile->h, F_SETLK, &lock); if( s==(-1) ){ tErrno = errno; rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK); if( IS_LOCK_ERROR(rc) ){ pFile->lastErrno = tErrno; } } } #ifndef NDEBUG /* Set up the transaction-counter change checking flags when ** transitioning from a SHARED to a RESERVED lock. The change ** from SHARED to RESERVED marks the beginning of a normal ** write operation (not a hot journal rollback). */ if( rc==SQLITE_OK && pFile->locktype<=SHARED_LOCK && locktype==RESERVED_LOCK ){ pFile->transCntrChng = 0; pFile->dbUpdate = 0; pFile->inNormalWrite = 1; } #endif if( rc==SQLITE_OK ){ pFile->locktype = locktype; pLock->locktype = locktype; }else if( locktype==EXCLUSIVE_LOCK ){ pFile->locktype = PENDING_LOCK; pLock->locktype = PENDING_LOCK; } end_lock: unixLeaveMutex(); OSTRACE4("LOCK %d %s %s (unix)\n", pFile->h, locktypeName(locktype), rc==SQLITE_OK ? "ok" : "failed"); return rc; } /* ** Close all file descriptors accumuated in the unixOpenCnt->pUnused list. ** If all such file descriptors are closed without error, the list is ** cleared and SQLITE_OK returned. ** ** Otherwise, if an error occurs, then successfully closed file descriptor ** entries are removed from the list, and SQLITE_IOERR_CLOSE returned. ** not deleted and SQLITE_IOERR_CLOSE returned. */ static int closePendingFds(unixFile *pFile){ int rc = SQLITE_OK; struct unixOpenCnt *pOpen = pFile->pOpen; UnixUnusedFd *pError = 0; UnixUnusedFd *p; UnixUnusedFd *pNext; for(p=pOpen->pUnused; p; p=pNext){ pNext = p->pNext; if( close(p->fd) ){ pFile->lastErrno = errno; rc = SQLITE_IOERR_CLOSE; p->pNext = pError; pError = p; }else{ sqlite3_free(p); } } pOpen->pUnused = pError; return rc; } /* ** Add the file descriptor used by file handle pFile to the corresponding ** pUnused list. */ static void setPendingFd(unixFile *pFile){ struct unixOpenCnt *pOpen = pFile->pOpen; UnixUnusedFd *p = pFile->pUnused; p->pNext = pOpen->pUnused; pOpen->pUnused = p; pFile->h = -1; pFile->pUnused = 0; } /* ** Lower the locking level on file descriptor pFile to locktype. locktype ** must be either NO_LOCK or SHARED_LOCK. ** ** If the locking level of the file descriptor is already at or below ** the requested locking level, this routine is a no-op. ** ** If handleNFSUnlock is true, then on downgrading an EXCLUSIVE_LOCK to SHARED ** the byte range is divided into 2 parts and the first part is unlocked then ** set to a read lock, then the other part is simply unlocked. This works ** around a bug in BSD NFS lockd (also seen on MacOSX 10.3+) that fails to ** remove the write lock on a region when a read lock is set. */ static int _posixUnlock(sqlite3_file *id, int locktype, int handleNFSUnlock){ unixFile *pFile = (unixFile*)id; struct unixLockInfo *pLock; struct flock lock; int rc = SQLITE_OK; int h; int tErrno; /* Error code from system call errors */ assert( pFile ); OSTRACE7("UNLOCK %d %d was %d(%d,%d) pid=%d (unix)\n", pFile->h, locktype, pFile->locktype, pFile->pLock->locktype, pFile->pLock->cnt, getpid()); assert( locktype<=SHARED_LOCK ); if( pFile->locktype<=locktype ){ return SQLITE_OK; } if( CHECK_THREADID(pFile) ){ return SQLITE_MISUSE; } unixEnterMutex(); h = pFile->h; pLock = pFile->pLock; assert( pLock->cnt!=0 ); if( pFile->locktype>SHARED_LOCK ){ assert( pLock->locktype==pFile->locktype ); SimulateIOErrorBenign(1); SimulateIOError( h=(-1) ) SimulateIOErrorBenign(0); #ifndef NDEBUG /* When reducing a lock such that other processes can start ** reading the database file again, make sure that the ** transaction counter was updated if any part of the database ** file changed. If the transaction counter is not updated, ** other connections to the same file might not realize that ** the file has changed and hence might not know to flush their ** cache. The use of a stale cache can lead to database corruption. */ assert( pFile->inNormalWrite==0 || pFile->dbUpdate==0 || pFile->transCntrChng==1 ); pFile->inNormalWrite = 0; #endif /* downgrading to a shared lock on NFS involves clearing the write lock ** before establishing the readlock - to avoid a race condition we downgrade ** the lock in 2 blocks, so that part of the range will be covered by a ** write lock until the rest is covered by a read lock: ** 1: [WWWWW] ** 2: [....W] ** 3: [RRRRW] ** 4: [RRRR.] */ if( locktype==SHARED_LOCK ){ if( handleNFSUnlock ){ off_t divSize = SHARED_SIZE - 1; lock.l_type = F_UNLCK; lock.l_whence = SEEK_SET; lock.l_start = SHARED_FIRST; lock.l_len = divSize; if( fcntl(h, F_SETLK, &lock)==(-1) ){ int tErrno = errno; rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK); if( IS_LOCK_ERROR(rc) ){ pFile->lastErrno = tErrno; } goto end_unlock; } lock.l_type = F_RDLCK; lock.l_whence = SEEK_SET; lock.l_start = SHARED_FIRST; lock.l_len = divSize; if( fcntl(h, F_SETLK, &lock)==(-1) ){ int tErrno = errno; rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_RDLOCK); if( IS_LOCK_ERROR(rc) ){ pFile->lastErrno = tErrno; } goto end_unlock; } lock.l_type = F_UNLCK; lock.l_whence = SEEK_SET; lock.l_start = SHARED_FIRST+divSize; lock.l_len = SHARED_SIZE-divSize; if( fcntl(h, F_SETLK, &lock)==(-1) ){ int tErrno = errno; rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK); if( IS_LOCK_ERROR(rc) ){ pFile->lastErrno = tErrno; } goto end_unlock; } }else{ lock.l_type = F_RDLCK; lock.l_whence = SEEK_SET; lock.l_start = SHARED_FIRST; lock.l_len = SHARED_SIZE; if( fcntl(h, F_SETLK, &lock)==(-1) ){ int tErrno = errno; rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_RDLOCK); if( IS_LOCK_ERROR(rc) ){ pFile->lastErrno = tErrno; } goto end_unlock; } } } lock.l_type = F_UNLCK; lock.l_whence = SEEK_SET; lock.l_start = PENDING_BYTE; lock.l_len = 2L; assert( PENDING_BYTE+1==RESERVED_BYTE ); if( fcntl(h, F_SETLK, &lock)!=(-1) ){ pLock->locktype = SHARED_LOCK; }else{ tErrno = errno; rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK); if( IS_LOCK_ERROR(rc) ){ pFile->lastErrno = tErrno; } goto end_unlock; } } if( locktype==NO_LOCK ){ struct unixOpenCnt *pOpen; /* Decrement the shared lock counter. Release the lock using an ** OS call only when all threads in this same process have released ** the lock. */ pLock->cnt--; if( pLock->cnt==0 ){ lock.l_type = F_UNLCK; lock.l_whence = SEEK_SET; lock.l_start = lock.l_len = 0L; SimulateIOErrorBenign(1); SimulateIOError( h=(-1) ) SimulateIOErrorBenign(0); if( fcntl(h, F_SETLK, &lock)!=(-1) ){ pLock->locktype = NO_LOCK; }else{ tErrno = errno; rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK); if( IS_LOCK_ERROR(rc) ){ pFile->lastErrno = tErrno; } pLock->locktype = NO_LOCK; pFile->locktype = NO_LOCK; } } /* Decrement the count of locks against this same file. When the ** count reaches zero, close any other file descriptors whose close ** was deferred because of outstanding locks. */ pOpen = pFile->pOpen; pOpen->nLock--; assert( pOpen->nLock>=0 ); if( pOpen->nLock==0 ){ int rc2 = closePendingFds(pFile); if( rc==SQLITE_OK ){ rc = rc2; } } } end_unlock: unixLeaveMutex(); if( rc==SQLITE_OK ) pFile->locktype = locktype; return rc; } /* ** Lower the locking level on file descriptor pFile to locktype. locktype ** must be either NO_LOCK or SHARED_LOCK. ** ** If the locking level of the file descriptor is already at or below ** the requested locking level, this routine is a no-op. */ static int unixUnlock(sqlite3_file *id, int locktype){ return _posixUnlock(id, locktype, 0); } /* ** This function performs the parts of the "close file" operation ** common to all locking schemes. It closes the directory and file ** handles, if they are valid, and sets all fields of the unixFile ** structure to 0. ** ** It is *not* necessary to hold the mutex when this routine is called, ** even on VxWorks. A mutex will be acquired on VxWorks by the ** vxworksReleaseFileId() routine. */ static int closeUnixFile(sqlite3_file *id){ unixFile *pFile = (unixFile*)id; if( pFile ){ if( pFile->dirfd>=0 ){ int err = close(pFile->dirfd); if( err ){ pFile->lastErrno = errno; return SQLITE_IOERR_DIR_CLOSE; }else{ pFile->dirfd=-1; } } if( pFile->h>=0 ){ int err = close(pFile->h); if( err ){ pFile->lastErrno = errno; return SQLITE_IOERR_CLOSE; } } #if OS_VXWORKS if( pFile->pId ){ if( pFile->isDelete ){ unlink(pFile->pId->zCanonicalName); } vxworksReleaseFileId(pFile->pId); pFile->pId = 0; } #endif OSTRACE2("CLOSE %-3d\n", pFile->h); OpenCounter(-1); sqlite3_free(pFile->pUnused); memset(pFile, 0, sizeof(unixFile)); } return SQLITE_OK; } /* ** Close a file. */ static int unixClose(sqlite3_file *id){ int rc = SQLITE_OK; if( id ){ unixFile *pFile = (unixFile *)id; unixUnlock(id, NO_LOCK); unixEnterMutex(); if( pFile->pOpen && pFile->pOpen->nLock ){ /* If there are outstanding locks, do not actually close the file just ** yet because that would clear those locks. Instead, add the file ** descriptor to pOpen->pUnused list. It will be automatically closed ** when the last lock is cleared. */ setPendingFd(pFile); } releaseLockInfo(pFile->pLock); releaseOpenCnt(pFile->pOpen); rc = closeUnixFile(id); unixLeaveMutex(); } return rc; } /************** End of the posix advisory lock implementation ***************** ******************************************************************************/ /****************************************************************************** ****************************** No-op Locking ********************************** ** ** Of the various locking implementations available, this is by far the ** simplest: locking is ignored. No attempt is made to lock the database ** file for reading or writing. ** ** This locking mode is appropriate for use on read-only databases ** (ex: databases that are burned into CD-ROM, for example.) It can ** also be used if the application employs some external mechanism to ** prevent simultaneous access of the same database by two or more ** database connections. But there is a serious risk of database ** corruption if this locking mode is used in situations where multiple ** database connections are accessing the same database file at the same ** time and one or more of those connections are writing. */ static int nolockCheckReservedLock(sqlite3_file *NotUsed, int *pResOut){ UNUSED_PARAMETER(NotUsed); *pResOut = 0; return SQLITE_OK; } static int nolockLock(sqlite3_file *NotUsed, int NotUsed2){ UNUSED_PARAMETER2(NotUsed, NotUsed2); return SQLITE_OK; } static int nolockUnlock(sqlite3_file *NotUsed, int NotUsed2){ UNUSED_PARAMETER2(NotUsed, NotUsed2); return SQLITE_OK; } /* ** Close the file. */ static int nolockClose(sqlite3_file *id) { return closeUnixFile(id); } /******************* End of the no-op lock implementation ********************* ******************************************************************************/ /****************************************************************************** ************************* Begin dot-file Locking ****************************** ** ** The dotfile locking implementation uses the existance of separate lock ** files in order to control access to the database. This works on just ** about every filesystem imaginable. But there are serious downsides: ** ** (1) There is zero concurrency. A single reader blocks all other ** connections from reading or writing the database. ** ** (2) An application crash or power loss can leave stale lock files ** sitting around that need to be cleared manually. ** ** Nevertheless, a dotlock is an appropriate locking mode for use if no ** other locking strategy is available. ** ** Dotfile locking works by creating a file in the same directory as the ** database and with the same name but with a ".lock" extension added. ** The existance of a lock file implies an EXCLUSIVE lock. All other lock ** types (SHARED, RESERVED, PENDING) are mapped into EXCLUSIVE. */ /* ** The file suffix added to the data base filename in order to create the ** lock file. */ #define DOTLOCK_SUFFIX ".lock" /* ** This routine checks if there is a RESERVED lock held on the specified ** file by this or any other process. If such a lock is held, set *pResOut ** to a non-zero value otherwise *pResOut is set to zero. The return value ** is set to SQLITE_OK unless an I/O error occurs during lock checking. ** ** In dotfile locking, either a lock exists or it does not. So in this ** variation of CheckReservedLock(), *pResOut is set to true if any lock ** is held on the file and false if the file is unlocked. */ static int dotlockCheckReservedLock(sqlite3_file *id, int *pResOut) { int rc = SQLITE_OK; int reserved = 0; unixFile *pFile = (unixFile*)id; SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; ); assert( pFile ); /* Check if a thread in this process holds such a lock */ if( pFile->locktype>SHARED_LOCK ){ /* Either this connection or some other connection in the same process ** holds a lock on the file. No need to check further. */ reserved = 1; }else{ /* The lock is held if and only if the lockfile exists */ const char *zLockFile = (const char*)pFile->lockingContext; reserved = access(zLockFile, 0)==0; } OSTRACE4("TEST WR-LOCK %d %d %d (dotlock)\n", pFile->h, rc, reserved); *pResOut = reserved; return rc; } /* ** Lock the file with the lock specified by parameter locktype - one ** of the following: ** ** (1) SHARED_LOCK ** (2) RESERVED_LOCK ** (3) PENDING_LOCK ** (4) EXCLUSIVE_LOCK ** ** Sometimes when requesting one lock state, additional lock states ** are inserted in between. The locking might fail on one of the later ** transitions leaving the lock state different from what it started but ** still short of its goal. The following chart shows the allowed ** transitions and the inserted intermediate states: ** ** UNLOCKED -> SHARED ** SHARED -> RESERVED ** SHARED -> (PENDING) -> EXCLUSIVE ** RESERVED -> (PENDING) -> EXCLUSIVE ** PENDING -> EXCLUSIVE ** ** This routine will only increase a lock. Use the sqlite3OsUnlock() ** routine to lower a locking level. ** ** With dotfile locking, we really only support state (4): EXCLUSIVE. ** But we track the other locking levels internally. */ static int dotlockLock(sqlite3_file *id, int locktype) { unixFile *pFile = (unixFile*)id; int fd; char *zLockFile = (char *)pFile->lockingContext; int rc = SQLITE_OK; /* If we have any lock, then the lock file already exists. All we have ** to do is adjust our internal record of the lock level. */ if( pFile->locktype > NO_LOCK ){ pFile->locktype = locktype; #if !OS_VXWORKS /* Always update the timestamp on the old file */ utimes(zLockFile, NULL); #endif return SQLITE_OK; } /* grab an exclusive lock */ fd = open(zLockFile,O_RDONLY|O_CREAT|O_EXCL,0600); if( fd<0 ){ /* failed to open/create the file, someone else may have stolen the lock */ int tErrno = errno; if( EEXIST == tErrno ){ rc = SQLITE_BUSY; } else { rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK); if( IS_LOCK_ERROR(rc) ){ pFile->lastErrno = tErrno; } } return rc; } if( close(fd) ){ pFile->lastErrno = errno; rc = SQLITE_IOERR_CLOSE; } /* got it, set the type and return ok */ pFile->locktype = locktype; return rc; } /* ** Lower the locking level on file descriptor pFile to locktype. locktype ** must be either NO_LOCK or SHARED_LOCK. ** ** If the locking level of the file descriptor is already at or below ** the requested locking level, this routine is a no-op. ** ** When the locking level reaches NO_LOCK, delete the lock file. */ static int dotlockUnlock(sqlite3_file *id, int locktype) { unixFile *pFile = (unixFile*)id; char *zLockFile = (char *)pFile->lockingContext; assert( pFile ); OSTRACE5("UNLOCK %d %d was %d pid=%d (dotlock)\n", pFile->h, locktype, pFile->locktype, getpid()); assert( locktype<=SHARED_LOCK ); /* no-op if possible */ if( pFile->locktype==locktype ){ return SQLITE_OK; } /* To downgrade to shared, simply update our internal notion of the ** lock state. No need to mess with the file on disk. */ if( locktype==SHARED_LOCK ){ pFile->locktype = SHARED_LOCK; return SQLITE_OK; } /* To fully unlock the database, delete the lock file */ assert( locktype==NO_LOCK ); if( unlink(zLockFile) ){ int rc = 0; int tErrno = errno; if( ENOENT != tErrno ){ rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK); } if( IS_LOCK_ERROR(rc) ){ pFile->lastErrno = tErrno; } return rc; } pFile->locktype = NO_LOCK; return SQLITE_OK; } /* ** Close a file. Make sure the lock has been released before closing. */ static int dotlockClose(sqlite3_file *id) { int rc; if( id ){ unixFile *pFile = (unixFile*)id; dotlockUnlock(id, NO_LOCK); sqlite3_free(pFile->lockingContext); } rc = closeUnixFile(id); return rc; } /****************** End of the dot-file lock implementation ******************* ******************************************************************************/ /****************************************************************************** ************************** Begin flock Locking ******************************** ** ** Use the flock() system call to do file locking. ** ** flock() locking is like dot-file locking in that the various ** fine-grain locking levels supported by SQLite are collapsed into ** a single exclusive lock. In other words, SHARED, RESERVED, and ** PENDING locks are the same thing as an EXCLUSIVE lock. SQLite ** still works when you do this, but concurrency is reduced since ** only a single process can be reading the database at a time. ** ** Omit this section if SQLITE_ENABLE_LOCKING_STYLE is turned off or if ** compiling for VXWORKS. */ #if SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORKS /* ** This routine checks if there is a RESERVED lock held on the specified ** file by this or any other process. If such a lock is held, set *pResOut ** to a non-zero value otherwise *pResOut is set to zero. The return value ** is set to SQLITE_OK unless an I/O error occurs during lock checking. */ static int flockCheckReservedLock(sqlite3_file *id, int *pResOut){ int rc = SQLITE_OK; int reserved = 0; unixFile *pFile = (unixFile*)id; SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; ); assert( pFile ); /* Check if a thread in this process holds such a lock */ if( pFile->locktype>SHARED_LOCK ){ reserved = 1; } /* Otherwise see if some other process holds it. */ if( !reserved ){ /* attempt to get the lock */ int lrc = flock(pFile->h, LOCK_EX | LOCK_NB); if( !lrc ){ /* got the lock, unlock it */ lrc = flock(pFile->h, LOCK_UN); if ( lrc ) { int tErrno = errno; /* unlock failed with an error */ lrc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK); if( IS_LOCK_ERROR(lrc) ){ pFile->lastErrno = tErrno; rc = lrc; } } } else { int tErrno = errno; reserved = 1; /* someone else might have it reserved */ lrc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK); if( IS_LOCK_ERROR(lrc) ){ pFile->lastErrno = tErrno; rc = lrc; } } } OSTRACE4("TEST WR-LOCK %d %d %d (flock)\n", pFile->h, rc, reserved); #ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS if( (rc & SQLITE_IOERR) == SQLITE_IOERR ){ rc = SQLITE_OK; reserved=1; } #endif /* SQLITE_IGNORE_FLOCK_LOCK_ERRORS */ *pResOut = reserved; return rc; } /* ** Lock the file with the lock specified by parameter locktype - one ** of the following: ** ** (1) SHARED_LOCK ** (2) RESERVED_LOCK ** (3) PENDING_LOCK ** (4) EXCLUSIVE_LOCK ** ** Sometimes when requesting one lock state, additional lock states ** are inserted in between. The locking might fail on one of the later ** transitions leaving the lock state different from what it started but ** still short of its goal. The following chart shows the allowed ** transitions and the inserted intermediate states: ** ** UNLOCKED -> SHARED ** SHARED -> RESERVED ** SHARED -> (PENDING) -> EXCLUSIVE ** RESERVED -> (PENDING) -> EXCLUSIVE ** PENDING -> EXCLUSIVE ** ** flock() only really support EXCLUSIVE locks. We track intermediate ** lock states in the sqlite3_file structure, but all locks SHARED or ** above are really EXCLUSIVE locks and exclude all other processes from ** access the file. ** ** This routine will only increase a lock. Use the sqlite3OsUnlock() ** routine to lower a locking level. */ static int flockLock(sqlite3_file *id, int locktype) { int rc = SQLITE_OK; unixFile *pFile = (unixFile*)id; assert( pFile ); /* if we already have a lock, it is exclusive. ** Just adjust level and punt on outta here. */ if (pFile->locktype > NO_LOCK) { pFile->locktype = locktype; return SQLITE_OK; } /* grab an exclusive lock */ if (flock(pFile->h, LOCK_EX | LOCK_NB)) { int tErrno = errno; /* didn't get, must be busy */ rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK); if( IS_LOCK_ERROR(rc) ){ pFile->lastErrno = tErrno; } } else { /* got it, set the type and return ok */ pFile->locktype = locktype; } OSTRACE4("LOCK %d %s %s (flock)\n", pFile->h, locktypeName(locktype), rc==SQLITE_OK ? "ok" : "failed"); #ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS if( (rc & SQLITE_IOERR) == SQLITE_IOERR ){ rc = SQLITE_BUSY; } #endif /* SQLITE_IGNORE_FLOCK_LOCK_ERRORS */ return rc; } /* ** Lower the locking level on file descriptor pFile to locktype. locktype ** must be either NO_LOCK or SHARED_LOCK. ** ** If the locking level of the file descriptor is already at or below ** the requested locking level, this routine is a no-op. */ static int flockUnlock(sqlite3_file *id, int locktype) { unixFile *pFile = (unixFile*)id; assert( pFile ); OSTRACE5("UNLOCK %d %d was %d pid=%d (flock)\n", pFile->h, locktype, pFile->locktype, getpid()); assert( locktype<=SHARED_LOCK ); /* no-op if possible */ if( pFile->locktype==locktype ){ return SQLITE_OK; } /* shared can just be set because we always have an exclusive */ if (locktype==SHARED_LOCK) { pFile->locktype = locktype; return SQLITE_OK; } /* no, really, unlock. */ int rc = flock(pFile->h, LOCK_UN); if (rc) { int r, tErrno = errno; r = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK); if( IS_LOCK_ERROR(r) ){ pFile->lastErrno = tErrno; } #ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS if( (r & SQLITE_IOERR) == SQLITE_IOERR ){ r = SQLITE_BUSY; } #endif /* SQLITE_IGNORE_FLOCK_LOCK_ERRORS */ return r; } else { pFile->locktype = NO_LOCK; return SQLITE_OK; } } /* ** Close a file. */ static int flockClose(sqlite3_file *id) { if( id ){ flockUnlock(id, NO_LOCK); } return closeUnixFile(id); } #endif /* SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORK */ /******************* End of the flock lock implementation ********************* ******************************************************************************/ /****************************************************************************** ************************ Begin Named Semaphore Locking ************************ ** ** Named semaphore locking is only supported on VxWorks. ** ** Semaphore locking is like dot-lock and flock in that it really only ** supports EXCLUSIVE locking. Only a single process can read or write ** the database file at a time. This reduces potential concurrency, but ** makes the lock implementation much easier. */ #if OS_VXWORKS /* ** This routine checks if there is a RESERVED lock held on the specified ** file by this or any other process. If such a lock is held, set *pResOut ** to a non-zero value otherwise *pResOut is set to zero. The return value ** is set to SQLITE_OK unless an I/O error occurs during lock checking. */ static int semCheckReservedLock(sqlite3_file *id, int *pResOut) { int rc = SQLITE_OK; int reserved = 0; unixFile *pFile = (unixFile*)id; SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; ); assert( pFile ); /* Check if a thread in this process holds such a lock */ if( pFile->locktype>SHARED_LOCK ){ reserved = 1; } /* Otherwise see if some other process holds it. */ if( !reserved ){ sem_t *pSem = pFile->pOpen->pSem; struct stat statBuf; if( sem_trywait(pSem)==-1 ){ int tErrno = errno; if( EAGAIN != tErrno ){ rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_CHECKRESERVEDLOCK); pFile->lastErrno = tErrno; } else { /* someone else has the lock when we are in NO_LOCK */ reserved = (pFile->locktype < SHARED_LOCK); } }else{ /* we could have it if we want it */ sem_post(pSem); } } OSTRACE4("TEST WR-LOCK %d %d %d (sem)\n", pFile->h, rc, reserved); *pResOut = reserved; return rc; } /* ** Lock the file with the lock specified by parameter locktype - one ** of the following: ** ** (1) SHARED_LOCK ** (2) RESERVED_LOCK ** (3) PENDING_LOCK ** (4) EXCLUSIVE_LOCK ** ** Sometimes when requesting one lock state, additional lock states ** are inserted in between. The locking might fail on one of the later ** transitions leaving the lock state different from what it started but ** still short of its goal. The following chart shows the allowed ** transitions and the inserted intermediate states: ** ** UNLOCKED -> SHARED ** SHARED -> RESERVED ** SHARED -> (PENDING) -> EXCLUSIVE ** RESERVED -> (PENDING) -> EXCLUSIVE ** PENDING -> EXCLUSIVE ** ** Semaphore locks only really support EXCLUSIVE locks. We track intermediate ** lock states in the sqlite3_file structure, but all locks SHARED or ** above are really EXCLUSIVE locks and exclude all other processes from ** access the file. ** ** This routine will only increase a lock. Use the sqlite3OsUnlock() ** routine to lower a locking level. */ static int semLock(sqlite3_file *id, int locktype) { unixFile *pFile = (unixFile*)id; int fd; sem_t *pSem = pFile->pOpen->pSem; int rc = SQLITE_OK; /* if we already have a lock, it is exclusive. ** Just adjust level and punt on outta here. */ if (pFile->locktype > NO_LOCK) { pFile->locktype = locktype; rc = SQLITE_OK; goto sem_end_lock; } /* lock semaphore now but bail out when already locked. */ if( sem_trywait(pSem)==-1 ){ rc = SQLITE_BUSY; goto sem_end_lock; } /* got it, set the type and return ok */ pFile->locktype = locktype; sem_end_lock: return rc; } /* ** Lower the locking level on file descriptor pFile to locktype. locktype ** must be either NO_LOCK or SHARED_LOCK. ** ** If the locking level of the file descriptor is already at or below ** the requested locking level, this routine is a no-op. */ static int semUnlock(sqlite3_file *id, int locktype) { unixFile *pFile = (unixFile*)id; sem_t *pSem = pFile->pOpen->pSem; assert( pFile ); assert( pSem ); OSTRACE5("UNLOCK %d %d was %d pid=%d (sem)\n", pFile->h, locktype, pFile->locktype, getpid()); assert( locktype<=SHARED_LOCK ); /* no-op if possible */ if( pFile->locktype==locktype ){ return SQLITE_OK; } /* shared can just be set because we always have an exclusive */ if (locktype==SHARED_LOCK) { pFile->locktype = locktype; return SQLITE_OK; } /* no, really unlock. */ if ( sem_post(pSem)==-1 ) { int rc, tErrno = errno; rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK); if( IS_LOCK_ERROR(rc) ){ pFile->lastErrno = tErrno; } return rc; } pFile->locktype = NO_LOCK; return SQLITE_OK; } /* ** Close a file. */ static int semClose(sqlite3_file *id) { if( id ){ unixFile *pFile = (unixFile*)id; semUnlock(id, NO_LOCK); assert( pFile ); unixEnterMutex(); releaseLockInfo(pFile->pLock); releaseOpenCnt(pFile->pOpen); unixLeaveMutex(); closeUnixFile(id); } return SQLITE_OK; } #endif /* OS_VXWORKS */ /* ** Named semaphore locking is only available on VxWorks. ** *************** End of the named semaphore lock implementation **************** ******************************************************************************/ /****************************************************************************** *************************** Begin AFP Locking ********************************* ** ** AFP is the Apple Filing Protocol. AFP is a network filesystem found ** on Apple Macintosh computers - both OS9 and OSX. ** ** Third-party implementations of AFP are available. But this code here ** only works on OSX. */ #if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE /* ** The afpLockingContext structure contains all afp lock specific state */ typedef struct afpLockingContext afpLockingContext; struct afpLockingContext { int reserved; const char *dbPath; /* Name of the open file */ }; struct ByteRangeLockPB2 { unsigned long long offset; /* offset to first byte to lock */ unsigned long long length; /* nbr of bytes to lock */ unsigned long long retRangeStart; /* nbr of 1st byte locked if successful */ unsigned char unLockFlag; /* 1 = unlock, 0 = lock */ unsigned char startEndFlag; /* 1=rel to end of fork, 0=rel to start */ int fd; /* file desc to assoc this lock with */ }; #define afpfsByteRangeLock2FSCTL _IOWR('z', 23, struct ByteRangeLockPB2) /* ** This is a utility for setting or clearing a bit-range lock on an ** AFP filesystem. ** ** Return SQLITE_OK on success, SQLITE_BUSY on failure. */ static int afpSetLock( const char *path, /* Name of the file to be locked or unlocked */ unixFile *pFile, /* Open file descriptor on path */ unsigned long long offset, /* First byte to be locked */ unsigned long long length, /* Number of bytes to lock */ int setLockFlag /* True to set lock. False to clear lock */ ){ struct ByteRangeLockPB2 pb; int err; pb.unLockFlag = setLockFlag ? 0 : 1; pb.startEndFlag = 0; pb.offset = offset; pb.length = length; pb.fd = pFile->h; OSTRACE6("AFPSETLOCK [%s] for %d%s in range %llx:%llx\n", (setLockFlag?"ON":"OFF"), pFile->h, (pb.fd==-1?"[testval-1]":""), offset, length); err = fsctl(path, afpfsByteRangeLock2FSCTL, &pb, 0); if ( err==-1 ) { int rc; int tErrno = errno; OSTRACE4("AFPSETLOCK failed to fsctl() '%s' %d %s\n", path, tErrno, strerror(tErrno)); #ifdef SQLITE_IGNORE_AFP_LOCK_ERRORS rc = SQLITE_BUSY; #else rc = sqliteErrorFromPosixError(tErrno, setLockFlag ? SQLITE_IOERR_LOCK : SQLITE_IOERR_UNLOCK); #endif /* SQLITE_IGNORE_AFP_LOCK_ERRORS */ if( IS_LOCK_ERROR(rc) ){ pFile->lastErrno = tErrno; } return rc; } else { return SQLITE_OK; } } /* ** This routine checks if there is a RESERVED lock held on the specified ** file by this or any other process. If such a lock is held, set *pResOut ** to a non-zero value otherwise *pResOut is set to zero. The return value ** is set to SQLITE_OK unless an I/O error occurs during lock checking. */ static int afpCheckReservedLock(sqlite3_file *id, int *pResOut){ int rc = SQLITE_OK; int reserved = 0; unixFile *pFile = (unixFile*)id; SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; ); assert( pFile ); afpLockingContext *context = (afpLockingContext *) pFile->lockingContext; if( context->reserved ){ *pResOut = 1; return SQLITE_OK; } unixEnterMutex(); /* Because pFile->pLock is shared across threads */ /* Check if a thread in this process holds such a lock */ if( pFile->pLock->locktype>SHARED_LOCK ){ reserved = 1; } /* Otherwise see if some other process holds it. */ if( !reserved ){ /* lock the RESERVED byte */ int lrc = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1,1); if( SQLITE_OK==lrc ){ /* if we succeeded in taking the reserved lock, unlock it to restore ** the original state */ lrc = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1, 0); } else { /* if we failed to get the lock then someone else must have it */ reserved = 1; } if( IS_LOCK_ERROR(lrc) ){ rc=lrc; } } unixLeaveMutex(); OSTRACE4("TEST WR-LOCK %d %d %d (afp)\n", pFile->h, rc, reserved); *pResOut = reserved; return rc; } /* ** Lock the file with the lock specified by parameter locktype - one ** of the following: ** ** (1) SHARED_LOCK ** (2) RESERVED_LOCK ** (3) PENDING_LOCK ** (4) EXCLUSIVE_LOCK ** ** Sometimes when requesting one lock state, additional lock states ** are inserted in between. The locking might fail on one of the later ** transitions leaving the lock state different from what it started but ** still short of its goal. The following chart shows the allowed ** transitions and the inserted intermediate states: ** ** UNLOCKED -> SHARED ** SHARED -> RESERVED ** SHARED -> (PENDING) -> EXCLUSIVE ** RESERVED -> (PENDING) -> EXCLUSIVE ** PENDING -> EXCLUSIVE ** ** This routine will only increase a lock. Use the sqlite3OsUnlock() ** routine to lower a locking level. */ static int afpLock(sqlite3_file *id, int locktype){ int rc = SQLITE_OK; unixFile *pFile = (unixFile*)id; struct unixLockInfo *pLock = pFile->pLock; afpLockingContext *context = (afpLockingContext *) pFile->lockingContext; assert( pFile ); OSTRACE7("LOCK %d %s was %s(%s,%d) pid=%d (afp)\n", pFile->h, locktypeName(locktype), locktypeName(pFile->locktype), locktypeName(pLock->locktype), pLock->cnt , getpid()); /* If there is already a lock of this type or more restrictive on the ** unixFile, do nothing. Don't use the afp_end_lock: exit path, as ** unixEnterMutex() hasn't been called yet. */ if( pFile->locktype>=locktype ){ OSTRACE3("LOCK %d %s ok (already held) (afp)\n", pFile->h, locktypeName(locktype)); return SQLITE_OK; } /* Make sure the locking sequence is correct ** (1) We never move from unlocked to anything higher than shared lock. ** (2) SQLite never explicitly requests a pendig lock. ** (3) A shared lock is always held when a reserve lock is requested. */ assert( pFile->locktype!=NO_LOCK || locktype==SHARED_LOCK ); assert( locktype!=PENDING_LOCK ); assert( locktype!=RESERVED_LOCK || pFile->locktype==SHARED_LOCK ); /* This mutex is needed because pFile->pLock is shared across threads */ unixEnterMutex(); /* Make sure the current thread owns the pFile. */ rc = transferOwnership(pFile); if( rc!=SQLITE_OK ){ unixLeaveMutex(); return rc; } pLock = pFile->pLock; /* If some thread using this PID has a lock via a different unixFile* ** handle that precludes the requested lock, return BUSY. */ if( (pFile->locktype!=pLock->locktype && (pLock->locktype>=PENDING_LOCK || locktype>SHARED_LOCK)) ){ rc = SQLITE_BUSY; goto afp_end_lock; } /* If a SHARED lock is requested, and some thread using this PID already ** has a SHARED or RESERVED lock, then increment reference counts and ** return SQLITE_OK. */ if( locktype==SHARED_LOCK && (pLock->locktype==SHARED_LOCK || pLock->locktype==RESERVED_LOCK) ){ assert( locktype==SHARED_LOCK ); assert( pFile->locktype==0 ); assert( pLock->cnt>0 ); pFile->locktype = SHARED_LOCK; pLock->cnt++; pFile->pOpen->nLock++; goto afp_end_lock; } /* A PENDING lock is needed before acquiring a SHARED lock and before ** acquiring an EXCLUSIVE lock. For the SHARED lock, the PENDING will ** be released. */ if( locktype==SHARED_LOCK || (locktype==EXCLUSIVE_LOCK && pFile->locktypedbPath, pFile, PENDING_BYTE, 1, 1); if (failed) { rc = failed; goto afp_end_lock; } } /* If control gets to this point, then actually go ahead and make ** operating system calls for the specified lock. */ if( locktype==SHARED_LOCK ){ int lrc1, lrc2, lrc1Errno; long lk, mask; assert( pLock->cnt==0 ); assert( pLock->locktype==0 ); mask = (sizeof(long)==8) ? LARGEST_INT64 : 0x7fffffff; /* Now get the read-lock SHARED_LOCK */ /* note that the quality of the randomness doesn't matter that much */ lk = random(); pLock->sharedByte = (lk & mask)%(SHARED_SIZE - 1); lrc1 = afpSetLock(context->dbPath, pFile, SHARED_FIRST+pLock->sharedByte, 1, 1); if( IS_LOCK_ERROR(lrc1) ){ lrc1Errno = pFile->lastErrno; } /* Drop the temporary PENDING lock */ lrc2 = afpSetLock(context->dbPath, pFile, PENDING_BYTE, 1, 0); if( IS_LOCK_ERROR(lrc1) ) { pFile->lastErrno = lrc1Errno; rc = lrc1; goto afp_end_lock; } else if( IS_LOCK_ERROR(lrc2) ){ rc = lrc2; goto afp_end_lock; } else if( lrc1 != SQLITE_OK ) { rc = lrc1; } else { pFile->locktype = SHARED_LOCK; pFile->pOpen->nLock++; pLock->cnt = 1; } }else if( locktype==EXCLUSIVE_LOCK && pLock->cnt>1 ){ /* We are trying for an exclusive lock but another thread in this ** same process is still holding a shared lock. */ rc = SQLITE_BUSY; }else{ /* The request was for a RESERVED or EXCLUSIVE lock. It is ** assumed that there is a SHARED or greater lock on the file ** already. */ int failed = 0; assert( 0!=pFile->locktype ); if (locktype >= RESERVED_LOCK && pFile->locktype < RESERVED_LOCK) { /* Acquire a RESERVED lock */ failed = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1,1); if( !failed ){ context->reserved = 1; } } if (!failed && locktype == EXCLUSIVE_LOCK) { /* Acquire an EXCLUSIVE lock */ /* Remove the shared lock before trying the range. we'll need to ** reestablish the shared lock if we can't get the afpUnlock */ if( !(failed = afpSetLock(context->dbPath, pFile, SHARED_FIRST + pLock->sharedByte, 1, 0)) ){ int failed2 = SQLITE_OK; /* now attemmpt to get the exclusive lock range */ failed = afpSetLock(context->dbPath, pFile, SHARED_FIRST, SHARED_SIZE, 1); if( failed && (failed2 = afpSetLock(context->dbPath, pFile, SHARED_FIRST + pLock->sharedByte, 1, 1)) ){ /* Can't reestablish the shared lock. Sqlite can't deal, this is ** a critical I/O error */ rc = ((failed & SQLITE_IOERR) == SQLITE_IOERR) ? failed2 : SQLITE_IOERR_LOCK; goto afp_end_lock; } }else{ rc = failed; } } if( failed ){ rc = failed; } } if( rc==SQLITE_OK ){ pFile->locktype = locktype; pLock->locktype = locktype; }else if( locktype==EXCLUSIVE_LOCK ){ pFile->locktype = PENDING_LOCK; pLock->locktype = PENDING_LOCK; } afp_end_lock: unixLeaveMutex(); OSTRACE4("LOCK %d %s %s (afp)\n", pFile->h, locktypeName(locktype), rc==SQLITE_OK ? "ok" : "failed"); return rc; } /* ** Lower the locking level on file descriptor pFile to locktype. locktype ** must be either NO_LOCK or SHARED_LOCK. ** ** If the locking level of the file descriptor is already at or below ** the requested locking level, this routine is a no-op. */ static int afpUnlock(sqlite3_file *id, int locktype) { int rc = SQLITE_OK; unixFile *pFile = (unixFile*)id; struct unixLockInfo *pLock; afpLockingContext *context = (afpLockingContext *) pFile->lockingContext; int skipShared = 0; #ifdef SQLITE_TEST int h = pFile->h; #endif assert( pFile ); OSTRACE7("UNLOCK %d %d was %d(%d,%d) pid=%d (afp)\n", pFile->h, locktype, pFile->locktype, pFile->pLock->locktype, pFile->pLock->cnt, getpid()); assert( locktype<=SHARED_LOCK ); if( pFile->locktype<=locktype ){ return SQLITE_OK; } if( CHECK_THREADID(pFile) ){ return SQLITE_MISUSE; } unixEnterMutex(); pLock = pFile->pLock; assert( pLock->cnt!=0 ); if( pFile->locktype>SHARED_LOCK ){ assert( pLock->locktype==pFile->locktype ); SimulateIOErrorBenign(1); SimulateIOError( h=(-1) ) SimulateIOErrorBenign(0); #ifndef NDEBUG /* When reducing a lock such that other processes can start ** reading the database file again, make sure that the ** transaction counter was updated if any part of the database ** file changed. If the transaction counter is not updated, ** other connections to the same file might not realize that ** the file has changed and hence might not know to flush their ** cache. The use of a stale cache can lead to database corruption. */ assert( pFile->inNormalWrite==0 || pFile->dbUpdate==0 || pFile->transCntrChng==1 ); pFile->inNormalWrite = 0; #endif if( pFile->locktype==EXCLUSIVE_LOCK ){ rc = afpSetLock(context->dbPath, pFile, SHARED_FIRST, SHARED_SIZE, 0); if( rc==SQLITE_OK && (locktype==SHARED_LOCK || pLock->cnt>1) ){ /* only re-establish the shared lock if necessary */ int sharedLockByte = SHARED_FIRST+pLock->sharedByte; rc = afpSetLock(context->dbPath, pFile, sharedLockByte, 1, 1); } else { skipShared = 1; } } if( rc==SQLITE_OK && pFile->locktype>=PENDING_LOCK ){ rc = afpSetLock(context->dbPath, pFile, PENDING_BYTE, 1, 0); } if( rc==SQLITE_OK && pFile->locktype>=RESERVED_LOCK && context->reserved ){ rc = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1, 0); if( !rc ){ context->reserved = 0; } } if( rc==SQLITE_OK && (locktype==SHARED_LOCK || pLock->cnt>1)){ pLock->locktype = SHARED_LOCK; } } if( rc==SQLITE_OK && locktype==NO_LOCK ){ /* Decrement the shared lock counter. Release the lock using an ** OS call only when all threads in this same process have released ** the lock. */ unsigned long long sharedLockByte = SHARED_FIRST+pLock->sharedByte; pLock->cnt--; if( pLock->cnt==0 ){ SimulateIOErrorBenign(1); SimulateIOError( h=(-1) ) SimulateIOErrorBenign(0); if( !skipShared ){ rc = afpSetLock(context->dbPath, pFile, sharedLockByte, 1, 0); } if( !rc ){ pLock->locktype = NO_LOCK; pFile->locktype = NO_LOCK; } } if( rc==SQLITE_OK ){ struct unixOpenCnt *pOpen = pFile->pOpen; pOpen->nLock--; assert( pOpen->nLock>=0 ); if( pOpen->nLock==0 ){ rc = closePendingFds(pFile); } } } unixLeaveMutex(); if( rc==SQLITE_OK ) pFile->locktype = locktype; return rc; } /* ** Close a file & cleanup AFP specific locking context */ static int afpClose(sqlite3_file *id) { int rc = SQLITE_OK; if( id ){ unixFile *pFile = (unixFile*)id; afpUnlock(id, NO_LOCK); unixEnterMutex(); if( pFile->pOpen && pFile->pOpen->nLock ){ /* If there are outstanding locks, do not actually close the file just ** yet because that would clear those locks. Instead, add the file ** descriptor to pOpen->aPending. It will be automatically closed when ** the last lock is cleared. */ setPendingFd(pFile); } releaseLockInfo(pFile->pLock); releaseOpenCnt(pFile->pOpen); sqlite3_free(pFile->lockingContext); rc = closeUnixFile(id); unixLeaveMutex(); } return rc; } #endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */ /* ** The code above is the AFP lock implementation. The code is specific ** to MacOSX and does not work on other unix platforms. No alternative ** is available. If you don't compile for a mac, then the "unix-afp" ** VFS is not available. ** ********************* End of the AFP lock implementation ********************** ******************************************************************************/ /****************************************************************************** *************************** Begin NFS Locking ********************************/ #if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE /* ** Lower the locking level on file descriptor pFile to locktype. locktype ** must be either NO_LOCK or SHARED_LOCK. ** ** If the locking level of the file descriptor is already at or below ** the requested locking level, this routine is a no-op. */ static int nfsUnlock(sqlite3_file *id, int locktype){ return _posixUnlock(id, locktype, 1); } #endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */ /* ** The code above is the NFS lock implementation. The code is specific ** to MacOSX and does not work on other unix platforms. No alternative ** is available. ** ********************* End of the NFS lock implementation ********************** ******************************************************************************/ /****************************************************************************** **************** Non-locking sqlite3_file methods ***************************** ** ** The next division contains implementations for all methods of the ** sqlite3_file object other than the locking methods. The locking ** methods were defined in divisions above (one locking method per ** division). Those methods that are common to all locking modes ** are gather together into this division. */ /* ** Seek to the offset passed as the second argument, then read cnt ** bytes into pBuf. Return the number of bytes actually read. ** ** NB: If you define USE_PREAD or USE_PREAD64, then it might also ** be necessary to define _XOPEN_SOURCE to be 500. This varies from ** one system to another. Since SQLite does not define USE_PREAD ** any any form by default, we will not attempt to define _XOPEN_SOURCE. ** See tickets #2741 and #2681. ** ** To avoid stomping the errno value on a failed read the lastErrno value ** is set before returning. */ static int seekAndRead(unixFile *id, sqlite3_int64 offset, void *pBuf, int cnt){ int got; #if (!defined(USE_PREAD) && !defined(USE_PREAD64)) i64 newOffset; #endif TIMER_START; #if defined(USE_PREAD) got = pread(id->h, pBuf, cnt, offset); SimulateIOError( got = -1 ); #elif defined(USE_PREAD64) got = pread64(id->h, pBuf, cnt, offset); SimulateIOError( got = -1 ); #else newOffset = lseek(id->h, offset, SEEK_SET); SimulateIOError( newOffset-- ); if( newOffset!=offset ){ if( newOffset == -1 ){ ((unixFile*)id)->lastErrno = errno; }else{ ((unixFile*)id)->lastErrno = 0; } return -1; } got = read(id->h, pBuf, cnt); #endif TIMER_END; if( got<0 ){ ((unixFile*)id)->lastErrno = errno; } OSTRACE5("READ %-3d %5d %7lld %llu\n", id->h, got, offset, TIMER_ELAPSED); return got; } /* ** Read data from a file into a buffer. Return SQLITE_OK if all ** bytes were read successfully and SQLITE_IOERR if anything goes ** wrong. */ static int unixRead( sqlite3_file *id, void *pBuf, int amt, sqlite3_int64 offset ){ unixFile *pFile = (unixFile *)id; int got; assert( id ); /* If this is a database file (not a journal, master-journal or temp ** file), the bytes in the locking range should never be read or written. */ assert( pFile->pUnused==0 || offset>=PENDING_BYTE+512 || offset+amt<=PENDING_BYTE ); got = seekAndRead(pFile, offset, pBuf, amt); if( got==amt ){ return SQLITE_OK; }else if( got<0 ){ /* lastErrno set by seekAndRead */ return SQLITE_IOERR_READ; }else{ pFile->lastErrno = 0; /* not a system error */ /* Unread parts of the buffer must be zero-filled */ memset(&((char*)pBuf)[got], 0, amt-got); return SQLITE_IOERR_SHORT_READ; } } /* ** Seek to the offset in id->offset then read cnt bytes into pBuf. ** Return the number of bytes actually read. Update the offset. ** ** To avoid stomping the errno value on a failed write the lastErrno value ** is set before returning. */ static int seekAndWrite(unixFile *id, i64 offset, const void *pBuf, int cnt){ int got; #if (!defined(USE_PREAD) && !defined(USE_PREAD64)) i64 newOffset; #endif TIMER_START; #if defined(USE_PREAD) got = pwrite(id->h, pBuf, cnt, offset); #elif defined(USE_PREAD64) got = pwrite64(id->h, pBuf, cnt, offset); #else newOffset = lseek(id->h, offset, SEEK_SET); if( newOffset!=offset ){ if( newOffset == -1 ){ ((unixFile*)id)->lastErrno = errno; }else{ ((unixFile*)id)->lastErrno = 0; } return -1; } got = write(id->h, pBuf, cnt); #endif TIMER_END; if( got<0 ){ ((unixFile*)id)->lastErrno = errno; } OSTRACE5("WRITE %-3d %5d %7lld %llu\n", id->h, got, offset, TIMER_ELAPSED); return got; } /* ** Write data from a buffer into a file. Return SQLITE_OK on success ** or some other error code on failure. */ static int unixWrite( sqlite3_file *id, const void *pBuf, int amt, sqlite3_int64 offset ){ unixFile *pFile = (unixFile*)id; int wrote = 0; assert( id ); assert( amt>0 ); /* If this is a database file (not a journal, master-journal or temp ** file), the bytes in the locking range should never be read or written. */ assert( pFile->pUnused==0 || offset>=PENDING_BYTE+512 || offset+amt<=PENDING_BYTE ); #ifndef NDEBUG /* If we are doing a normal write to a database file (as opposed to ** doing a hot-journal rollback or a write to some file other than a ** normal database file) then record the fact that the database ** has changed. If the transaction counter is modified, record that ** fact too. */ if( pFile->inNormalWrite ){ pFile->dbUpdate = 1; /* The database has been modified */ if( offset<=24 && offset+amt>=27 ){ int rc; char oldCntr[4]; SimulateIOErrorBenign(1); rc = seekAndRead(pFile, 24, oldCntr, 4); SimulateIOErrorBenign(0); if( rc!=4 || memcmp(oldCntr, &((char*)pBuf)[24-offset], 4)!=0 ){ pFile->transCntrChng = 1; /* The transaction counter has changed */ } } } #endif while( amt>0 && (wrote = seekAndWrite(pFile, offset, pBuf, amt))>0 ){ amt -= wrote; offset += wrote; pBuf = &((char*)pBuf)[wrote]; } SimulateIOError(( wrote=(-1), amt=1 )); SimulateDiskfullError(( wrote=0, amt=1 )); if( amt>0 ){ if( wrote<0 ){ /* lastErrno set by seekAndWrite */ return SQLITE_IOERR_WRITE; }else{ pFile->lastErrno = 0; /* not a system error */ return SQLITE_FULL; } } return SQLITE_OK; } #ifdef SQLITE_TEST /* ** Count the number of fullsyncs and normal syncs. This is used to test ** that syncs and fullsyncs are occurring at the right times. */ int sqlite3_sync_count = 0; int sqlite3_fullsync_count = 0; #endif /* ** We do not trust systems to provide a working fdatasync(). Some do. ** Others do no. To be safe, we will stick with the (slower) fsync(). ** If you know that your system does support fdatasync() correctly, ** then simply compile with -Dfdatasync=fdatasync */ #if !defined(fdatasync) && !defined(__linux__) # define fdatasync fsync #endif /* ** Define HAVE_FULLFSYNC to 0 or 1 depending on whether or not ** the F_FULLFSYNC macro is defined. F_FULLFSYNC is currently ** only available on Mac OS X. But that could change. */ #ifdef F_FULLFSYNC # define HAVE_FULLFSYNC 1 #else # define HAVE_FULLFSYNC 0 #endif /* ** The fsync() system call does not work as advertised on many ** unix systems. The following procedure is an attempt to make ** it work better. ** ** The SQLITE_NO_SYNC macro disables all fsync()s. This is useful ** for testing when we want to run through the test suite quickly. ** You are strongly advised *not* to deploy with SQLITE_NO_SYNC ** enabled, however, since with SQLITE_NO_SYNC enabled, an OS crash ** or power failure will likely corrupt the database file. ** ** SQLite sets the dataOnly flag if the size of the file is unchanged. ** The idea behind dataOnly is that it should only write the file content ** to disk, not the inode. We only set dataOnly if the file size is ** unchanged since the file size is part of the inode. However, ** Ted Ts'o tells us that fdatasync() will also write the inode if the ** file size has changed. The only real difference between fdatasync() ** and fsync(), Ted tells us, is that fdatasync() will not flush the ** inode if the mtime or owner or other inode attributes have changed. ** We only care about the file size, not the other file attributes, so ** as far as SQLite is concerned, an fdatasync() is always adequate. ** So, we always use fdatasync() if it is available, regardless of ** the value of the dataOnly flag. */ static int full_fsync(int fd, int fullSync, int dataOnly){ int rc; /* The following "ifdef/elif/else/" block has the same structure as ** the one below. It is replicated here solely to avoid cluttering ** up the real code with the UNUSED_PARAMETER() macros. */ #ifdef SQLITE_NO_SYNC UNUSED_PARAMETER(fd); UNUSED_PARAMETER(fullSync); UNUSED_PARAMETER(dataOnly); #elif HAVE_FULLFSYNC UNUSED_PARAMETER(dataOnly); #else UNUSED_PARAMETER(fullSync); UNUSED_PARAMETER(dataOnly); #endif /* Record the number of times that we do a normal fsync() and ** FULLSYNC. This is used during testing to verify that this procedure ** gets called with the correct arguments. */ #ifdef SQLITE_TEST if( fullSync ) sqlite3_fullsync_count++; sqlite3_sync_count++; #endif /* If we compiled with the SQLITE_NO_SYNC flag, then syncing is a ** no-op */ #ifdef SQLITE_NO_SYNC rc = SQLITE_OK; #elif HAVE_FULLFSYNC if( fullSync ){ rc = fcntl(fd, F_FULLFSYNC, 0); }else{ rc = 1; } /* If the FULLFSYNC failed, fall back to attempting an fsync(). ** It shouldn't be possible for fullfsync to fail on the local ** file system (on OSX), so failure indicates that FULLFSYNC ** isn't supported for this file system. So, attempt an fsync ** and (for now) ignore the overhead of a superfluous fcntl call. ** It'd be better to detect fullfsync support once and avoid ** the fcntl call every time sync is called. */ if( rc ) rc = fsync(fd); #elif defined(__APPLE__) /* fdatasync() on HFS+ doesn't yet flush the file size if it changed correctly ** so currently we default to the macro that redefines fdatasync to fsync */ rc = fsync(fd); #else rc = fdatasync(fd); #if OS_VXWORKS if( rc==-1 && errno==ENOTSUP ){ rc = fsync(fd); } #endif /* OS_VXWORKS */ #endif /* ifdef SQLITE_NO_SYNC elif HAVE_FULLFSYNC */ if( OS_VXWORKS && rc!= -1 ){ rc = 0; } return rc; } /* ** Make sure all writes to a particular file are committed to disk. ** ** If dataOnly==0 then both the file itself and its metadata (file ** size, access time, etc) are synced. If dataOnly!=0 then only the ** file data is synced. ** ** Under Unix, also make sure that the directory entry for the file ** has been created by fsync-ing the directory that contains the file. ** If we do not do this and we encounter a power failure, the directory ** entry for the journal might not exist after we reboot. The next ** SQLite to access the file will not know that the journal exists (because ** the directory entry for the journal was never created) and the transaction ** will not roll back - possibly leading to database corruption. */ static int unixSync(sqlite3_file *id, int flags){ int rc; unixFile *pFile = (unixFile*)id; int isDataOnly = (flags&SQLITE_SYNC_DATAONLY); int isFullsync = (flags&0x0F)==SQLITE_SYNC_FULL; /* Check that one of SQLITE_SYNC_NORMAL or FULL was passed */ assert((flags&0x0F)==SQLITE_SYNC_NORMAL || (flags&0x0F)==SQLITE_SYNC_FULL ); /* Unix cannot, but some systems may return SQLITE_FULL from here. This ** line is to test that doing so does not cause any problems. */ SimulateDiskfullError( return SQLITE_FULL ); assert( pFile ); OSTRACE2("SYNC %-3d\n", pFile->h); rc = full_fsync(pFile->h, isFullsync, isDataOnly); SimulateIOError( rc=1 ); if( rc ){ pFile->lastErrno = errno; return SQLITE_IOERR_FSYNC; } if( pFile->dirfd>=0 ){ int err; OSTRACE4("DIRSYNC %-3d (have_fullfsync=%d fullsync=%d)\n", pFile->dirfd, HAVE_FULLFSYNC, isFullsync); #ifndef SQLITE_DISABLE_DIRSYNC /* The directory sync is only attempted if full_fsync is ** turned off or unavailable. If a full_fsync occurred above, ** then the directory sync is superfluous. */ if( (!HAVE_FULLFSYNC || !isFullsync) && full_fsync(pFile->dirfd,0,0) ){ /* ** We have received multiple reports of fsync() returning ** errors when applied to directories on certain file systems. ** A failed directory sync is not a big deal. So it seems ** better to ignore the error. Ticket #1657 */ /* pFile->lastErrno = errno; */ /* return SQLITE_IOERR; */ } #endif err = close(pFile->dirfd); /* Only need to sync once, so close the */ if( err==0 ){ /* directory when we are done */ pFile->dirfd = -1; }else{ pFile->lastErrno = errno; rc = SQLITE_IOERR_DIR_CLOSE; } } return rc; } /* ** Truncate an open file to a specified size */ static int unixTruncate(sqlite3_file *id, i64 nByte){ int rc; assert( id ); SimulateIOError( return SQLITE_IOERR_TRUNCATE ); rc = ftruncate(((unixFile*)id)->h, (off_t)nByte); if( rc ){ ((unixFile*)id)->lastErrno = errno; return SQLITE_IOERR_TRUNCATE; }else{ #ifndef NDEBUG /* If we are doing a normal write to a database file (as opposed to ** doing a hot-journal rollback or a write to some file other than a ** normal database file) and we truncate the file to zero length, ** that effectively updates the change counter. This might happen ** when restoring a database using the backup API from a zero-length ** source. */ if( ((unixFile*)id)->inNormalWrite && nByte==0 ){ ((unixFile*)id)->transCntrChng = 1; } #endif return SQLITE_OK; } } /* ** Determine the current size of a file in bytes */ static int unixFileSize(sqlite3_file *id, i64 *pSize){ int rc; struct stat buf; assert( id ); rc = fstat(((unixFile*)id)->h, &buf); SimulateIOError( rc=1 ); if( rc!=0 ){ ((unixFile*)id)->lastErrno = errno; return SQLITE_IOERR_FSTAT; } *pSize = buf.st_size; /* When opening a zero-size database, the findLockInfo() procedure ** writes a single byte into that file in order to work around a bug ** in the OS-X msdos filesystem. In order to avoid problems with upper ** layers, we need to report this file size as zero even though it is ** really 1. Ticket #3260. */ if( *pSize==1 ) *pSize = 0; return SQLITE_OK; } #if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__) /* ** Handler for proxy-locking file-control verbs. Defined below in the ** proxying locking division. */ static int proxyFileControl(sqlite3_file*,int,void*); #endif /* ** Information and control of an open file handle. */ static int unixFileControl(sqlite3_file *id, int op, void *pArg){ switch( op ){ case SQLITE_FCNTL_LOCKSTATE: { *(int*)pArg = ((unixFile*)id)->locktype; return SQLITE_OK; } case SQLITE_LAST_ERRNO: { *(int*)pArg = ((unixFile*)id)->lastErrno; return SQLITE_OK; } #ifndef NDEBUG /* The pager calls this method to signal that it has done ** a rollback and that the database is therefore unchanged and ** it hence it is OK for the transaction change counter to be ** unchanged. */ case SQLITE_FCNTL_DB_UNCHANGED: { ((unixFile*)id)->dbUpdate = 0; return SQLITE_OK; } #endif #if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__) case SQLITE_SET_LOCKPROXYFILE: case SQLITE_GET_LOCKPROXYFILE: { return proxyFileControl(id,op,pArg); } #endif /* SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__) */ } return SQLITE_ERROR; } /* ** Return the sector size in bytes of the underlying block device for ** the specified file. This is almost always 512 bytes, but may be ** larger for some devices. ** ** SQLite code assumes this function cannot fail. It also assumes that ** if two files are created in the same file-system directory (i.e. ** a database and its journal file) that the sector size will be the ** same for both. */ static int unixSectorSize(sqlite3_file *NotUsed){ UNUSED_PARAMETER(NotUsed); return SQLITE_DEFAULT_SECTOR_SIZE; } /* ** Return the device characteristics for the file. This is always 0 for unix. */ static int unixDeviceCharacteristics(sqlite3_file *NotUsed){ UNUSED_PARAMETER(NotUsed); return 0; } /* ** Here ends the implementation of all sqlite3_file methods. ** ********************** End sqlite3_file Methods ******************************* ******************************************************************************/ /* ** This division contains definitions of sqlite3_io_methods objects that ** implement various file locking strategies. It also contains definitions ** of "finder" functions. A finder-function is used to locate the appropriate ** sqlite3_io_methods object for a particular database file. The pAppData ** field of the sqlite3_vfs VFS objects are initialized to be pointers to ** the correct finder-function for that VFS. ** ** Most finder functions return a pointer to a fixed sqlite3_io_methods ** object. The only interesting finder-function is autolockIoFinder, which ** looks at the filesystem type and tries to guess the best locking ** strategy from that. ** ** For finder-funtion F, two objects are created: ** ** (1) The real finder-function named "FImpt()". ** ** (2) A constant pointer to this function named just "F". ** ** ** A pointer to the F pointer is used as the pAppData value for VFS ** objects. We have to do this instead of letting pAppData point ** directly at the finder-function since C90 rules prevent a void* ** from be cast into a function pointer. ** ** ** Each instance of this macro generates two objects: ** ** * A constant sqlite3_io_methods object call METHOD that has locking ** methods CLOSE, LOCK, UNLOCK, CKRESLOCK. ** ** * An I/O method finder function called FINDER that returns a pointer ** to the METHOD object in the previous bullet. */ #define IOMETHODS(FINDER, METHOD, CLOSE, LOCK, UNLOCK, CKLOCK) \ static const sqlite3_io_methods METHOD = { \ 1, /* iVersion */ \ CLOSE, /* xClose */ \ unixRead, /* xRead */ \ unixWrite, /* xWrite */ \ unixTruncate, /* xTruncate */ \ unixSync, /* xSync */ \ unixFileSize, /* xFileSize */ \ LOCK, /* xLock */ \ UNLOCK, /* xUnlock */ \ CKLOCK, /* xCheckReservedLock */ \ unixFileControl, /* xFileControl */ \ unixSectorSize, /* xSectorSize */ \ unixDeviceCharacteristics /* xDeviceCapabilities */ \ }; \ static const sqlite3_io_methods *FINDER##Impl(const char *z, unixFile *p){ \ UNUSED_PARAMETER(z); UNUSED_PARAMETER(p); \ return &METHOD; \ } \ static const sqlite3_io_methods *(*const FINDER)(const char*,unixFile *p) \ = FINDER##Impl; /* ** Here are all of the sqlite3_io_methods objects for each of the ** locking strategies. Functions that return pointers to these methods ** are also created. */ IOMETHODS( posixIoFinder, /* Finder function name */ posixIoMethods, /* sqlite3_io_methods object name */ unixClose, /* xClose method */ unixLock, /* xLock method */ unixUnlock, /* xUnlock method */ unixCheckReservedLock /* xCheckReservedLock method */ ) IOMETHODS( nolockIoFinder, /* Finder function name */ nolockIoMethods, /* sqlite3_io_methods object name */ nolockClose, /* xClose method */ nolockLock, /* xLock method */ nolockUnlock, /* xUnlock method */ nolockCheckReservedLock /* xCheckReservedLock method */ ) IOMETHODS( dotlockIoFinder, /* Finder function name */ dotlockIoMethods, /* sqlite3_io_methods object name */ dotlockClose, /* xClose method */ dotlockLock, /* xLock method */ dotlockUnlock, /* xUnlock method */ dotlockCheckReservedLock /* xCheckReservedLock method */ ) #if SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORKS IOMETHODS( flockIoFinder, /* Finder function name */ flockIoMethods, /* sqlite3_io_methods object name */ flockClose, /* xClose method */ flockLock, /* xLock method */ flockUnlock, /* xUnlock method */ flockCheckReservedLock /* xCheckReservedLock method */ ) #endif #if OS_VXWORKS IOMETHODS( semIoFinder, /* Finder function name */ semIoMethods, /* sqlite3_io_methods object name */ semClose, /* xClose method */ semLock, /* xLock method */ semUnlock, /* xUnlock method */ semCheckReservedLock /* xCheckReservedLock method */ ) #endif #if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE IOMETHODS( afpIoFinder, /* Finder function name */ afpIoMethods, /* sqlite3_io_methods object name */ afpClose, /* xClose method */ afpLock, /* xLock method */ afpUnlock, /* xUnlock method */ afpCheckReservedLock /* xCheckReservedLock method */ ) #endif /* ** The proxy locking method is a "super-method" in the sense that it ** opens secondary file descriptors for the conch and lock files and ** it uses proxy, dot-file, AFP, and flock() locking methods on those ** secondary files. For this reason, the division that implements ** proxy locking is located much further down in the file. But we need ** to go ahead and define the sqlite3_io_methods and finder function ** for proxy locking here. So we forward declare the I/O methods. */ #if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE static int proxyClose(sqlite3_file*); static int proxyLock(sqlite3_file*, int); static int proxyUnlock(sqlite3_file*, int); static int proxyCheckReservedLock(sqlite3_file*, int*); IOMETHODS( proxyIoFinder, /* Finder function name */ proxyIoMethods, /* sqlite3_io_methods object name */ proxyClose, /* xClose method */ proxyLock, /* xLock method */ proxyUnlock, /* xUnlock method */ proxyCheckReservedLock /* xCheckReservedLock method */ ) #endif /* nfs lockd on OSX 10.3+ doesn't clear write locks when a read lock is set */ #if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE IOMETHODS( nfsIoFinder, /* Finder function name */ nfsIoMethods, /* sqlite3_io_methods object name */ unixClose, /* xClose method */ unixLock, /* xLock method */ nfsUnlock, /* xUnlock method */ unixCheckReservedLock /* xCheckReservedLock method */ ) #endif #if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE /* ** This "finder" function attempts to determine the best locking strategy ** for the database file "filePath". It then returns the sqlite3_io_methods ** object that implements that strategy. ** ** This is for MacOSX only. */ static const sqlite3_io_methods *autolockIoFinderImpl( const char *filePath, /* name of the database file */ unixFile *pNew /* open file object for the database file */ ){ static const struct Mapping { const char *zFilesystem; /* Filesystem type name */ const sqlite3_io_methods *pMethods; /* Appropriate locking method */ } aMap[] = { { "hfs", &posixIoMethods }, { "ufs", &posixIoMethods }, { "afpfs", &afpIoMethods }, { "smbfs", &afpIoMethods }, { "webdav", &nolockIoMethods }, { 0, 0 } }; int i; struct statfs fsInfo; struct flock lockInfo; if( !filePath ){ /* If filePath==NULL that means we are dealing with a transient file ** that does not need to be locked. */ return &nolockIoMethods; } if( statfs(filePath, &fsInfo) != -1 ){ if( fsInfo.f_flags & MNT_RDONLY ){ return &nolockIoMethods; } for(i=0; aMap[i].zFilesystem; i++){ if( strcmp(fsInfo.f_fstypename, aMap[i].zFilesystem)==0 ){ return aMap[i].pMethods; } } } /* Default case. Handles, amongst others, "nfs". ** Test byte-range lock using fcntl(). If the call succeeds, ** assume that the file-system supports POSIX style locks. */ lockInfo.l_len = 1; lockInfo.l_start = 0; lockInfo.l_whence = SEEK_SET; lockInfo.l_type = F_RDLCK; if( fcntl(pNew->h, F_GETLK, &lockInfo)!=-1 ) { if( strcmp(fsInfo.f_fstypename, "nfs")==0 ){ return &nfsIoMethods; } else { return &posixIoMethods; } }else{ return &dotlockIoMethods; } } static const sqlite3_io_methods *(*const autolockIoFinder)(const char*,unixFile*) = autolockIoFinderImpl; #endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */ #if OS_VXWORKS && SQLITE_ENABLE_LOCKING_STYLE /* ** This "finder" function attempts to determine the best locking strategy ** for the database file "filePath". It then returns the sqlite3_io_methods ** object that implements that strategy. ** ** This is for VXWorks only. */ static const sqlite3_io_methods *autolockIoFinderImpl( const char *filePath, /* name of the database file */ unixFile *pNew /* the open file object */ ){ struct flock lockInfo; if( !filePath ){ /* If filePath==NULL that means we are dealing with a transient file ** that does not need to be locked. */ return &nolockIoMethods; } /* Test if fcntl() is supported and use POSIX style locks. ** Otherwise fall back to the named semaphore method. */ lockInfo.l_len = 1; lockInfo.l_start = 0; lockInfo.l_whence = SEEK_SET; lockInfo.l_type = F_RDLCK; if( fcntl(pNew->h, F_GETLK, &lockInfo)!=-1 ) { return &posixIoMethods; }else{ return &semIoMethods; } } static const sqlite3_io_methods *(*const autolockIoFinder)(const char*,unixFile*) = autolockIoFinderImpl; #endif /* OS_VXWORKS && SQLITE_ENABLE_LOCKING_STYLE */ /* ** An abstract type for a pointer to a IO method finder function: */ typedef const sqlite3_io_methods *(*finder_type)(const char*,unixFile*); /**************************************************************************** **************************** sqlite3_vfs methods **************************** ** ** This division contains the implementation of methods on the ** sqlite3_vfs object. */ /* ** Initialize the contents of the unixFile structure pointed to by pId. */ static int fillInUnixFile( sqlite3_vfs *pVfs, /* Pointer to vfs object */ int h, /* Open file descriptor of file being opened */ int dirfd, /* Directory file descriptor */ sqlite3_file *pId, /* Write to the unixFile structure here */ const char *zFilename, /* Name of the file being opened */ int noLock, /* Omit locking if true */ int isDelete /* Delete on close if true */ ){ const sqlite3_io_methods *pLockingStyle; unixFile *pNew = (unixFile *)pId; int rc = SQLITE_OK; assert( pNew->pLock==NULL ); assert( pNew->pOpen==NULL ); /* Parameter isDelete is only used on vxworks. Express this explicitly ** here to prevent compiler warnings about unused parameters. */ UNUSED_PARAMETER(isDelete); OSTRACE3("OPEN %-3d %s\n", h, zFilename); pNew->h = h; pNew->dirfd = dirfd; SET_THREADID(pNew); pNew->fileFlags = 0; #if OS_VXWORKS pNew->pId = vxworksFindFileId(zFilename); if( pNew->pId==0 ){ noLock = 1; rc = SQLITE_NOMEM; } #endif if( noLock ){ pLockingStyle = &nolockIoMethods; }else{ pLockingStyle = (**(finder_type*)pVfs->pAppData)(zFilename, pNew); #if SQLITE_ENABLE_LOCKING_STYLE /* Cache zFilename in the locking context (AFP and dotlock override) for ** proxyLock activation is possible (remote proxy is based on db name) ** zFilename remains valid until file is closed, to support */ pNew->lockingContext = (void*)zFilename; #endif } if( pLockingStyle == &posixIoMethods #if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE || pLockingStyle == &nfsIoMethods #endif ){ unixEnterMutex(); rc = findLockInfo(pNew, &pNew->pLock, &pNew->pOpen); if( rc!=SQLITE_OK ){ /* If an error occured in findLockInfo(), close the file descriptor ** immediately, before releasing the mutex. findLockInfo() may fail ** in two scenarios: ** ** (a) A call to fstat() failed. ** (b) A malloc failed. ** ** Scenario (b) may only occur if the process is holding no other ** file descriptors open on the same file. If there were other file ** descriptors on this file, then no malloc would be required by ** findLockInfo(). If this is the case, it is quite safe to close ** handle h - as it is guaranteed that no posix locks will be released ** by doing so. ** ** If scenario (a) caused the error then things are not so safe. The ** implicit assumption here is that if fstat() fails, things are in ** such bad shape that dropping a lock or two doesn't matter much. */ close(h); h = -1; } unixLeaveMutex(); } #if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__) else if( pLockingStyle == &afpIoMethods ){ /* AFP locking uses the file path so it needs to be included in ** the afpLockingContext. */ afpLockingContext *pCtx; pNew->lockingContext = pCtx = sqlite3_malloc( sizeof(*pCtx) ); if( pCtx==0 ){ rc = SQLITE_NOMEM; }else{ /* NB: zFilename exists and remains valid until the file is closed ** according to requirement F11141. So we do not need to make a ** copy of the filename. */ pCtx->dbPath = zFilename; pCtx->reserved = 0; srandomdev(); unixEnterMutex(); rc = findLockInfo(pNew, &pNew->pLock, &pNew->pOpen); if( rc!=SQLITE_OK ){ sqlite3_free(pNew->lockingContext); close(h); h = -1; } unixLeaveMutex(); } } #endif else if( pLockingStyle == &dotlockIoMethods ){ /* Dotfile locking uses the file path so it needs to be included in ** the dotlockLockingContext */ char *zLockFile; int nFilename; nFilename = (int)strlen(zFilename) + 6; zLockFile = (char *)sqlite3_malloc(nFilename); if( zLockFile==0 ){ rc = SQLITE_NOMEM; }else{ sqlite3_snprintf(nFilename, zLockFile, "%s" DOTLOCK_SUFFIX, zFilename); } pNew->lockingContext = zLockFile; } #if OS_VXWORKS else if( pLockingStyle == &semIoMethods ){ /* Named semaphore locking uses the file path so it needs to be ** included in the semLockingContext */ unixEnterMutex(); rc = findLockInfo(pNew, &pNew->pLock, &pNew->pOpen); if( (rc==SQLITE_OK) && (pNew->pOpen->pSem==NULL) ){ char *zSemName = pNew->pOpen->aSemName; int n; sqlite3_snprintf(MAX_PATHNAME, zSemName, "/%s.sem", pNew->pId->zCanonicalName); for( n=1; zSemName[n]; n++ ) if( zSemName[n]=='/' ) zSemName[n] = '_'; pNew->pOpen->pSem = sem_open(zSemName, O_CREAT, 0666, 1); if( pNew->pOpen->pSem == SEM_FAILED ){ rc = SQLITE_NOMEM; pNew->pOpen->aSemName[0] = '\0'; } } unixLeaveMutex(); } #endif pNew->lastErrno = 0; #if OS_VXWORKS if( rc!=SQLITE_OK ){ if( h>=0 ) close(h); h = -1; unlink(zFilename); isDelete = 0; } pNew->isDelete = isDelete; #endif if( rc!=SQLITE_OK ){ if( dirfd>=0 ) close(dirfd); /* silent leak if fail, already in error */ if( h>=0 ) close(h); }else{ pNew->pMethod = pLockingStyle; OpenCounter(+1); } return rc; } /* ** Open a file descriptor to the directory containing file zFilename. ** If successful, *pFd is set to the opened file descriptor and ** SQLITE_OK is returned. If an error occurs, either SQLITE_NOMEM ** or SQLITE_CANTOPEN is returned and *pFd is set to an undefined ** value. ** ** If SQLITE_OK is returned, the caller is responsible for closing ** the file descriptor *pFd using close(). */ static int openDirectory(const char *zFilename, int *pFd){ int ii; int fd = -1; char zDirname[MAX_PATHNAME+1]; sqlite3_snprintf(MAX_PATHNAME, zDirname, "%s", zFilename); for(ii=(int)strlen(zDirname); ii>1 && zDirname[ii]!='/'; ii--); if( ii>0 ){ zDirname[ii] = '\0'; fd = open(zDirname, O_RDONLY|O_BINARY, 0); if( fd>=0 ){ #ifdef FD_CLOEXEC fcntl(fd, F_SETFD, fcntl(fd, F_GETFD, 0) | FD_CLOEXEC); #endif OSTRACE3("OPENDIR %-3d %s\n", fd, zDirname); } } *pFd = fd; return (fd>=0?SQLITE_OK:SQLITE_CANTOPEN); } /* ** Create a temporary file name in zBuf. zBuf must be allocated ** by the calling process and must be big enough to hold at least ** pVfs->mxPathname bytes. */ static int getTempname(int nBuf, char *zBuf){ static const char *azDirs[] = { 0, 0, "/var/tmp", "/usr/tmp", "/tmp", ".", }; static const unsigned char zChars[] = "abcdefghijklmnopqrstuvwxyz" "ABCDEFGHIJKLMNOPQRSTUVWXYZ" "0123456789"; unsigned int i, j; struct stat buf; const char *zDir = "."; /* It's odd to simulate an io-error here, but really this is just ** using the io-error infrastructure to test that SQLite handles this ** function failing. */ SimulateIOError( return SQLITE_IOERR ); azDirs[0] = sqlite3_temp_directory; if (NULL == azDirs[1]) { azDirs[1] = getenv("TMPDIR"); } for(i=0; i= (size_t)nBuf ){ return SQLITE_ERROR; } do{ sqlite3_snprintf(nBuf-17, zBuf, "%s/"SQLITE_TEMP_FILE_PREFIX, zDir); j = (int)strlen(zBuf); sqlite3_randomness(15, &zBuf[j]); for(i=0; i<15; i++, j++){ zBuf[j] = (char)zChars[ ((unsigned char)zBuf[j])%(sizeof(zChars)-1) ]; } zBuf[j] = 0; }while( access(zBuf,0)==0 ); return SQLITE_OK; } #if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__) /* ** Routine to transform a unixFile into a proxy-locking unixFile. ** Implementation in the proxy-lock division, but used by unixOpen() ** if SQLITE_PREFER_PROXY_LOCKING is defined. */ static int proxyTransformUnixFile(unixFile*, const char*); #endif /* ** Search for an unused file descriptor that was opened on the database ** file (not a journal or master-journal file) identified by pathname ** zPath with SQLITE_OPEN_XXX flags matching those passed as the second ** argument to this function. ** ** Such a file descriptor may exist if a database connection was closed ** but the associated file descriptor could not be closed because some ** other file descriptor open on the same file is holding a file-lock. ** Refer to comments in the unixClose() function and the lengthy comment ** describing "Posix Advisory Locking" at the start of this file for ** further details. Also, ticket #4018. ** ** If a suitable file descriptor is found, then it is returned. If no ** such file descriptor is located, -1 is returned. */ static UnixUnusedFd *findReusableFd(const char *zPath, int flags){ UnixUnusedFd *pUnused = 0; /* Do not search for an unused file descriptor on vxworks. Not because ** vxworks would not benefit from the change (it might, we're not sure), ** but because no way to test it is currently available. It is better ** not to risk breaking vxworks support for the sake of such an obscure ** feature. */ #if !OS_VXWORKS struct stat sStat; /* Results of stat() call */ /* A stat() call may fail for various reasons. If this happens, it is ** almost certain that an open() call on the same path will also fail. ** For this reason, if an error occurs in the stat() call here, it is ** ignored and -1 is returned. The caller will try to open a new file ** descriptor on the same path, fail, and return an error to SQLite. ** ** Even if a subsequent open() call does succeed, the consequences of ** not searching for a resusable file descriptor are not dire. */ if( 0==stat(zPath, &sStat) ){ struct unixOpenCnt *pOpen; unixEnterMutex(); pOpen = openList; while( pOpen && (pOpen->fileId.dev!=sStat.st_dev || pOpen->fileId.ino!=sStat.st_ino) ){ pOpen = pOpen->pNext; } if( pOpen ){ UnixUnusedFd **pp; for(pp=&pOpen->pUnused; *pp && (*pp)->flags!=flags; pp=&((*pp)->pNext)); pUnused = *pp; if( pUnused ){ *pp = pUnused->pNext; } } unixLeaveMutex(); } #endif /* if !OS_VXWORKS */ return pUnused; } /* ** Open the file zPath. ** ** Previously, the SQLite OS layer used three functions in place of this ** one: ** ** sqlite3OsOpenReadWrite(); ** sqlite3OsOpenReadOnly(); ** sqlite3OsOpenExclusive(); ** ** These calls correspond to the following combinations of flags: ** ** ReadWrite() -> (READWRITE | CREATE) ** ReadOnly() -> (READONLY) ** OpenExclusive() -> (READWRITE | CREATE | EXCLUSIVE) ** ** The old OpenExclusive() accepted a boolean argument - "delFlag". If ** true, the file was configured to be automatically deleted when the ** file handle closed. To achieve the same effect using this new ** interface, add the DELETEONCLOSE flag to those specified above for ** OpenExclusive(). */ static int unixOpen( sqlite3_vfs *pVfs, /* The VFS for which this is the xOpen method */ const char *zPath, /* Pathname of file to be opened */ sqlite3_file *pFile, /* The file descriptor to be filled in */ int flags, /* Input flags to control the opening */ int *pOutFlags /* Output flags returned to SQLite core */ ){ unixFile *p = (unixFile *)pFile; int fd = -1; /* File descriptor returned by open() */ int dirfd = -1; /* Directory file descriptor */ int openFlags = 0; /* Flags to pass to open() */ int eType = flags&0xFFFFFF00; /* Type of file to open */ int noLock; /* True to omit locking primitives */ int rc = SQLITE_OK; /* Function Return Code */ int isExclusive = (flags & SQLITE_OPEN_EXCLUSIVE); int isDelete = (flags & SQLITE_OPEN_DELETEONCLOSE); int isCreate = (flags & SQLITE_OPEN_CREATE); int isReadonly = (flags & SQLITE_OPEN_READONLY); int isReadWrite = (flags & SQLITE_OPEN_READWRITE); #if SQLITE_ENABLE_LOCKING_STYLE int isAutoProxy = (flags & SQLITE_OPEN_AUTOPROXY); #endif /* If creating a master or main-file journal, this function will open ** a file-descriptor on the directory too. The first time unixSync() ** is called the directory file descriptor will be fsync()ed and close()d. */ int isOpenDirectory = (isCreate && (eType==SQLITE_OPEN_MASTER_JOURNAL || eType==SQLITE_OPEN_MAIN_JOURNAL) ); /* If argument zPath is a NULL pointer, this function is required to open ** a temporary file. Use this buffer to store the file name in. */ char zTmpname[MAX_PATHNAME+1]; const char *zName = zPath; /* Check the following statements are true: ** ** (a) Exactly one of the READWRITE and READONLY flags must be set, and ** (b) if CREATE is set, then READWRITE must also be set, and ** (c) if EXCLUSIVE is set, then CREATE must also be set. ** (d) if DELETEONCLOSE is set, then CREATE must also be set. */ assert((isReadonly==0 || isReadWrite==0) && (isReadWrite || isReadonly)); assert(isCreate==0 || isReadWrite); assert(isExclusive==0 || isCreate); assert(isDelete==0 || isCreate); /* The main DB, main journal, and master journal are never automatically ** deleted. Nor are they ever temporary files. */ assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MAIN_DB ); assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MAIN_JOURNAL ); assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MASTER_JOURNAL ); /* Assert that the upper layer has set one of the "file-type" flags. */ assert( eType==SQLITE_OPEN_MAIN_DB || eType==SQLITE_OPEN_TEMP_DB || eType==SQLITE_OPEN_MAIN_JOURNAL || eType==SQLITE_OPEN_TEMP_JOURNAL || eType==SQLITE_OPEN_SUBJOURNAL || eType==SQLITE_OPEN_MASTER_JOURNAL || eType==SQLITE_OPEN_TRANSIENT_DB ); memset(p, 0, sizeof(unixFile)); if( eType==SQLITE_OPEN_MAIN_DB ){ UnixUnusedFd *pUnused; pUnused = findReusableFd(zName, flags); if( pUnused ){ fd = pUnused->fd; }else{ pUnused = sqlite3_malloc(sizeof(*pUnused)); if( !pUnused ){ return SQLITE_NOMEM; } } p->pUnused = pUnused; }else if( !zName ){ /* If zName is NULL, the upper layer is requesting a temp file. */ assert(isDelete && !isOpenDirectory); rc = getTempname(MAX_PATHNAME+1, zTmpname); if( rc!=SQLITE_OK ){ return rc; } zName = zTmpname; } /* Determine the value of the flags parameter passed to POSIX function ** open(). These must be calculated even if open() is not called, as ** they may be stored as part of the file handle and used by the ** 'conch file' locking functions later on. */ if( isReadonly ) openFlags |= O_RDONLY; if( isReadWrite ) openFlags |= O_RDWR; if( isCreate ) openFlags |= O_CREAT; if( isExclusive ) openFlags |= (O_EXCL|O_NOFOLLOW); openFlags |= (O_LARGEFILE|O_BINARY); if( fd<0 ){ mode_t openMode = (isDelete?0600:SQLITE_DEFAULT_FILE_PERMISSIONS); fd = open(zName, openFlags, openMode); OSTRACE4("OPENX %-3d %s 0%o\n", fd, zName, openFlags); if( fd<0 && errno!=EISDIR && isReadWrite && !isExclusive ){ /* Failed to open the file for read/write access. Try read-only. */ flags &= ~(SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE); openFlags &= ~(O_RDWR|O_CREAT); flags |= SQLITE_OPEN_READONLY; openFlags |= O_RDONLY; fd = open(zName, openFlags, openMode); } if( fd<0 ){ rc = SQLITE_CANTOPEN; goto open_finished; } } assert( fd>=0 ); if( pOutFlags ){ *pOutFlags = flags; } if( p->pUnused ){ p->pUnused->fd = fd; p->pUnused->flags = flags; } if( isDelete ){ #if OS_VXWORKS zPath = zName; #else unlink(zName); #endif } #if SQLITE_ENABLE_LOCKING_STYLE else{ p->openFlags = openFlags; } #endif if( isOpenDirectory ){ rc = openDirectory(zPath, &dirfd); if( rc!=SQLITE_OK ){ /* It is safe to close fd at this point, because it is guaranteed not ** to be open on a database file. If it were open on a database file, ** it would not be safe to close as this would release any locks held ** on the file by this process. */ assert( eType!=SQLITE_OPEN_MAIN_DB ); close(fd); /* silently leak if fail, already in error */ goto open_finished; } } #ifdef FD_CLOEXEC fcntl(fd, F_SETFD, fcntl(fd, F_GETFD, 0) | FD_CLOEXEC); #endif noLock = eType!=SQLITE_OPEN_MAIN_DB; #if defined(__APPLE__) || SQLITE_ENABLE_LOCKING_STYLE struct statfs fsInfo; if( fstatfs(fd, &fsInfo) == -1 ){ ((unixFile*)pFile)->lastErrno = errno; if( dirfd>=0 ) close(dirfd); /* silently leak if fail, in error */ close(fd); /* silently leak if fail, in error */ return SQLITE_IOERR_ACCESS; } if (0 == strncmp("msdos", fsInfo.f_fstypename, 5)) { ((unixFile*)pFile)->fsFlags |= SQLITE_FSFLAGS_IS_MSDOS; } #endif #if SQLITE_ENABLE_LOCKING_STYLE #if SQLITE_PREFER_PROXY_LOCKING isAutoProxy = 1; #endif if( isAutoProxy && (zPath!=NULL) && (!noLock) && pVfs->xOpen ){ char *envforce = getenv("SQLITE_FORCE_PROXY_LOCKING"); int useProxy = 0; /* SQLITE_FORCE_PROXY_LOCKING==1 means force always use proxy, 0 means ** never use proxy, NULL means use proxy for non-local files only. */ if( envforce!=NULL ){ useProxy = atoi(envforce)>0; }else{ struct statfs fsInfo; if( statfs(zPath, &fsInfo) == -1 ){ /* In theory, the close(fd) call is sub-optimal. If the file opened ** with fd is a database file, and there are other connections open ** on that file that are currently holding advisory locks on it, ** then the call to close() will cancel those locks. In practice, ** we're assuming that statfs() doesn't fail very often. At least ** not while other file descriptors opened by the same process on ** the same file are working. */ p->lastErrno = errno; if( dirfd>=0 ){ close(dirfd); /* silently leak if fail, in error */ } close(fd); /* silently leak if fail, in error */ rc = SQLITE_IOERR_ACCESS; goto open_finished; } useProxy = !(fsInfo.f_flags&MNT_LOCAL); } if( useProxy ){ rc = fillInUnixFile(pVfs, fd, dirfd, pFile, zPath, noLock, isDelete); if( rc==SQLITE_OK ){ rc = proxyTransformUnixFile((unixFile*)pFile, ":auto:"); if( rc!=SQLITE_OK ){ /* Use unixClose to clean up the resources added in fillInUnixFile ** and clear all the structure's references. Specifically, ** pFile->pMethods will be NULL so sqlite3OsClose will be a no-op */ unixClose(pFile); return rc; } } goto open_finished; } } #endif rc = fillInUnixFile(pVfs, fd, dirfd, pFile, zPath, noLock, isDelete); open_finished: if( rc!=SQLITE_OK ){ sqlite3_free(p->pUnused); } return rc; } /* ** Delete the file at zPath. If the dirSync argument is true, fsync() ** the directory after deleting the file. */ static int unixDelete( sqlite3_vfs *NotUsed, /* VFS containing this as the xDelete method */ const char *zPath, /* Name of file to be deleted */ int dirSync /* If true, fsync() directory after deleting file */ ){ int rc = SQLITE_OK; UNUSED_PARAMETER(NotUsed); SimulateIOError(return SQLITE_IOERR_DELETE); unlink(zPath); #ifndef SQLITE_DISABLE_DIRSYNC if( dirSync ){ int fd; rc = openDirectory(zPath, &fd); if( rc==SQLITE_OK ){ #if OS_VXWORKS if( fsync(fd)==-1 ) #else if( fsync(fd) ) #endif { rc = SQLITE_IOERR_DIR_FSYNC; } if( close(fd)&&!rc ){ rc = SQLITE_IOERR_DIR_CLOSE; } } } #endif return rc; } /* ** Test the existance of or access permissions of file zPath. The ** test performed depends on the value of flags: ** ** SQLITE_ACCESS_EXISTS: Return 1 if the file exists ** SQLITE_ACCESS_READWRITE: Return 1 if the file is read and writable. ** SQLITE_ACCESS_READONLY: Return 1 if the file is readable. ** ** Otherwise return 0. */ static int unixAccess( sqlite3_vfs *NotUsed, /* The VFS containing this xAccess method */ const char *zPath, /* Path of the file to examine */ int flags, /* What do we want to learn about the zPath file? */ int *pResOut /* Write result boolean here */ ){ int amode = 0; UNUSED_PARAMETER(NotUsed); SimulateIOError( return SQLITE_IOERR_ACCESS; ); switch( flags ){ case SQLITE_ACCESS_EXISTS: amode = F_OK; break; case SQLITE_ACCESS_READWRITE: amode = W_OK|R_OK; break; case SQLITE_ACCESS_READ: amode = R_OK; break; default: assert(!"Invalid flags argument"); } *pResOut = (access(zPath, amode)==0); return SQLITE_OK; } /* ** Turn a relative pathname into a full pathname. The relative path ** is stored as a nul-terminated string in the buffer pointed to by ** zPath. ** ** zOut points to a buffer of at least sqlite3_vfs.mxPathname bytes ** (in this case, MAX_PATHNAME bytes). The full-path is written to ** this buffer before returning. */ static int unixFullPathname( sqlite3_vfs *pVfs, /* Pointer to vfs object */ const char *zPath, /* Possibly relative input path */ int nOut, /* Size of output buffer in bytes */ char *zOut /* Output buffer */ ){ /* It's odd to simulate an io-error here, but really this is just ** using the io-error infrastructure to test that SQLite handles this ** function failing. This function could fail if, for example, the ** current working directory has been unlinked. */ SimulateIOError( return SQLITE_ERROR ); assert( pVfs->mxPathname==MAX_PATHNAME ); UNUSED_PARAMETER(pVfs); zOut[nOut-1] = '\0'; if( zPath[0]=='/' ){ sqlite3_snprintf(nOut, zOut, "%s", zPath); }else{ int nCwd; if( getcwd(zOut, nOut-1)==0 ){ return SQLITE_CANTOPEN; } nCwd = (int)strlen(zOut); sqlite3_snprintf(nOut-nCwd, &zOut[nCwd], "/%s", zPath); } return SQLITE_OK; } #ifndef SQLITE_OMIT_LOAD_EXTENSION /* ** Interfaces for opening a shared library, finding entry points ** within the shared library, and closing the shared library. */ #include static void *unixDlOpen(sqlite3_vfs *NotUsed, const char *zFilename){ UNUSED_PARAMETER(NotUsed); return dlopen(zFilename, RTLD_NOW | RTLD_GLOBAL); } /* ** SQLite calls this function immediately after a call to unixDlSym() or ** unixDlOpen() fails (returns a null pointer). If a more detailed error ** message is available, it is written to zBufOut. If no error message ** is available, zBufOut is left unmodified and SQLite uses a default ** error message. */ static void unixDlError(sqlite3_vfs *NotUsed, int nBuf, char *zBufOut){ char *zErr; UNUSED_PARAMETER(NotUsed); unixEnterMutex(); zErr = dlerror(); if( zErr ){ sqlite3_snprintf(nBuf, zBufOut, "%s", zErr); } unixLeaveMutex(); } static void (*unixDlSym(sqlite3_vfs *NotUsed, void *p, const char*zSym))(void){ /* ** GCC with -pedantic-errors says that C90 does not allow a void* to be ** cast into a pointer to a function. And yet the library dlsym() routine ** returns a void* which is really a pointer to a function. So how do we ** use dlsym() with -pedantic-errors? ** ** Variable x below is defined to be a pointer to a function taking ** parameters void* and const char* and returning a pointer to a function. ** We initialize x by assigning it a pointer to the dlsym() function. ** (That assignment requires a cast.) Then we call the function that ** x points to. ** ** This work-around is unlikely to work correctly on any system where ** you really cannot cast a function pointer into void*. But then, on the ** other hand, dlsym() will not work on such a system either, so we have ** not really lost anything. */ void (*(*x)(void*,const char*))(void); UNUSED_PARAMETER(NotUsed); x = (void(*(*)(void*,const char*))(void))dlsym; return (*x)(p, zSym); } static void unixDlClose(sqlite3_vfs *NotUsed, void *pHandle){ UNUSED_PARAMETER(NotUsed); dlclose(pHandle); } #else /* if SQLITE_OMIT_LOAD_EXTENSION is defined: */ #define unixDlOpen 0 #define unixDlError 0 #define unixDlSym 0 #define unixDlClose 0 #endif /* ** Write nBuf bytes of random data to the supplied buffer zBuf. */ static int unixRandomness(sqlite3_vfs *NotUsed, int nBuf, char *zBuf){ UNUSED_PARAMETER(NotUsed); assert((size_t)nBuf>=(sizeof(time_t)+sizeof(int))); /* We have to initialize zBuf to prevent valgrind from reporting ** errors. The reports issued by valgrind are incorrect - we would ** prefer that the randomness be increased by making use of the ** uninitialized space in zBuf - but valgrind errors tend to worry ** some users. Rather than argue, it seems easier just to initialize ** the whole array and silence valgrind, even if that means less randomness ** in the random seed. ** ** When testing, initializing zBuf[] to zero is all we do. That means ** that we always use the same random number sequence. This makes the ** tests repeatable. */ memset(zBuf, 0, nBuf); #if !defined(SQLITE_TEST) { int pid, fd; fd = open("/dev/urandom", O_RDONLY); if( fd<0 ){ time_t t; time(&t); memcpy(zBuf, &t, sizeof(t)); pid = getpid(); memcpy(&zBuf[sizeof(t)], &pid, sizeof(pid)); assert( sizeof(t)+sizeof(pid)<=(size_t)nBuf ); nBuf = sizeof(t) + sizeof(pid); }else{ nBuf = read(fd, zBuf, nBuf); close(fd); } } #endif return nBuf; } /* ** Sleep for a little while. Return the amount of time slept. ** The argument is the number of microseconds we want to sleep. ** The return value is the number of microseconds of sleep actually ** requested from the underlying operating system, a number which ** might be greater than or equal to the argument, but not less ** than the argument. */ static int unixSleep(sqlite3_vfs *NotUsed, int microseconds){ #if OS_VXWORKS struct timespec sp; sp.tv_sec = microseconds / 1000000; sp.tv_nsec = (microseconds % 1000000) * 1000; nanosleep(&sp, NULL); UNUSED_PARAMETER(NotUsed); return microseconds; #elif defined(HAVE_USLEEP) && HAVE_USLEEP usleep(microseconds); UNUSED_PARAMETER(NotUsed); return microseconds; #else int seconds = (microseconds+999999)/1000000; sleep(seconds); UNUSED_PARAMETER(NotUsed); return seconds*1000000; #endif } /* ** The following variable, if set to a non-zero value, is interpreted as ** the number of seconds since 1970 and is used to set the result of ** sqlite3OsCurrentTime() during testing. */ #ifdef SQLITE_TEST int sqlite3_current_time = 0; /* Fake system time in seconds since 1970. */ #endif /* ** Find the current time (in Universal Coordinated Time). Write the ** current time and date as a Julian Day number into *prNow and ** return 0. Return 1 if the time and date cannot be found. */ static int unixCurrentTime(sqlite3_vfs *NotUsed, double *prNow){ #if defined(SQLITE_OMIT_FLOATING_POINT) time_t t; time(&t); *prNow = (((sqlite3_int64)t)/8640 + 24405875)/10; #elif defined(NO_GETTOD) time_t t; time(&t); *prNow = t/86400.0 + 2440587.5; #elif OS_VXWORKS struct timespec sNow; clock_gettime(CLOCK_REALTIME, &sNow); *prNow = 2440587.5 + sNow.tv_sec/86400.0 + sNow.tv_nsec/86400000000000.0; #else struct timeval sNow; gettimeofday(&sNow, 0); *prNow = 2440587.5 + sNow.tv_sec/86400.0 + sNow.tv_usec/86400000000.0; #endif #ifdef SQLITE_TEST if( sqlite3_current_time ){ *prNow = sqlite3_current_time/86400.0 + 2440587.5; } #endif UNUSED_PARAMETER(NotUsed); return 0; } /* ** We added the xGetLastError() method with the intention of providing ** better low-level error messages when operating-system problems come up ** during SQLite operation. But so far, none of that has been implemented ** in the core. So this routine is never called. For now, it is merely ** a place-holder. */ static int unixGetLastError(sqlite3_vfs *NotUsed, int NotUsed2, char *NotUsed3){ UNUSED_PARAMETER(NotUsed); UNUSED_PARAMETER(NotUsed2); UNUSED_PARAMETER(NotUsed3); return 0; } /* ************************ End of sqlite3_vfs methods *************************** ******************************************************************************/ /****************************************************************************** ************************** Begin Proxy Locking ******************************** ** ** Proxy locking is a "uber-locking-method" in this sense: It uses the ** other locking methods on secondary lock files. Proxy locking is a ** meta-layer over top of the primitive locking implemented above. For ** this reason, the division that implements of proxy locking is deferred ** until late in the file (here) after all of the other I/O methods have ** been defined - so that the primitive locking methods are available ** as services to help with the implementation of proxy locking. ** **** ** ** The default locking schemes in SQLite use byte-range locks on the ** database file to coordinate safe, concurrent access by multiple readers ** and writers [http://sqlite.org/lockingv3.html]. The five file locking ** states (UNLOCKED, PENDING, SHARED, RESERVED, EXCLUSIVE) are implemented ** as POSIX read & write locks over fixed set of locations (via fsctl), ** on AFP and SMB only exclusive byte-range locks are available via fsctl ** with _IOWR('z', 23, struct ByteRangeLockPB2) to track the same 5 states. ** To simulate a F_RDLCK on the shared range, on AFP a randomly selected ** address in the shared range is taken for a SHARED lock, the entire ** shared range is taken for an EXCLUSIVE lock): ** ** PENDING_BYTE 0x40000000 ** RESERVED_BYTE 0x40000001 ** SHARED_RANGE 0x40000002 -> 0x40000200 ** ** This works well on the local file system, but shows a nearly 100x ** slowdown in read performance on AFP because the AFP client disables ** the read cache when byte-range locks are present. Enabling the read ** cache exposes a cache coherency problem that is present on all OS X ** supported network file systems. NFS and AFP both observe the ** close-to-open semantics for ensuring cache coherency ** [http://nfs.sourceforge.net/#faq_a8], which does not effectively ** address the requirements for concurrent database access by multiple ** readers and writers ** [http://www.nabble.com/SQLite-on-NFS-cache-coherency-td15655701.html]. ** ** To address the performance and cache coherency issues, proxy file locking ** changes the way database access is controlled by limiting access to a ** single host at a time and moving file locks off of the database file ** and onto a proxy file on the local file system. ** ** ** Using proxy locks ** ----------------- ** ** C APIs ** ** sqlite3_file_control(db, dbname, SQLITE_SET_LOCKPROXYFILE, ** | ":auto:"); ** sqlite3_file_control(db, dbname, SQLITE_GET_LOCKPROXYFILE, &); ** ** ** SQL pragmas ** ** PRAGMA [database.]lock_proxy_file= | :auto: ** PRAGMA [database.]lock_proxy_file ** ** Specifying ":auto:" means that if there is a conch file with a matching ** host ID in it, the proxy path in the conch file will be used, otherwise ** a proxy path based on the user's temp dir ** (via confstr(_CS_DARWIN_USER_TEMP_DIR,...)) will be used and the ** actual proxy file name is generated from the name and path of the ** database file. For example: ** ** For database path "/Users/me/foo.db" ** The lock path will be "/sqliteplocks/_Users_me_foo.db:auto:") ** ** Once a lock proxy is configured for a database connection, it can not ** be removed, however it may be switched to a different proxy path via ** the above APIs (assuming the conch file is not being held by another ** connection or process). ** ** ** How proxy locking works ** ----------------------- ** ** Proxy file locking relies primarily on two new supporting files: ** ** * conch file to limit access to the database file to a single host ** at a time ** ** * proxy file to act as a proxy for the advisory locks normally ** taken on the database ** ** The conch file - to use a proxy file, sqlite must first "hold the conch" ** by taking an sqlite-style shared lock on the conch file, reading the ** contents and comparing the host's unique host ID (see below) and lock ** proxy path against the values stored in the conch. The conch file is ** stored in the same directory as the database file and the file name ** is patterned after the database file name as ".-conch". ** If the conch file does not exist, or it's contents do not match the ** host ID and/or proxy path, then the lock is escalated to an exclusive ** lock and the conch file contents is updated with the host ID and proxy ** path and the lock is downgraded to a shared lock again. If the conch ** is held by another process (with a shared lock), the exclusive lock ** will fail and SQLITE_BUSY is returned. ** ** The proxy file - a single-byte file used for all advisory file locks ** normally taken on the database file. This allows for safe sharing ** of the database file for multiple readers and writers on the same ** host (the conch ensures that they all use the same local lock file). ** ** Requesting the lock proxy does not immediately take the conch, it is ** only taken when the first request to lock database file is made. ** This matches the semantics of the traditional locking behavior, where ** opening a connection to a database file does not take a lock on it. ** The shared lock and an open file descriptor are maintained until ** the connection to the database is closed. ** ** The proxy file and the lock file are never deleted so they only need ** to be created the first time they are used. ** ** Configuration options ** --------------------- ** ** SQLITE_PREFER_PROXY_LOCKING ** ** Database files accessed on non-local file systems are ** automatically configured for proxy locking, lock files are ** named automatically using the same logic as ** PRAGMA lock_proxy_file=":auto:" ** ** SQLITE_PROXY_DEBUG ** ** Enables the logging of error messages during host id file ** retrieval and creation ** ** LOCKPROXYDIR ** ** Overrides the default directory used for lock proxy files that ** are named automatically via the ":auto:" setting ** ** SQLITE_DEFAULT_PROXYDIR_PERMISSIONS ** ** Permissions to use when creating a directory for storing the ** lock proxy files, only used when LOCKPROXYDIR is not set. ** ** ** As mentioned above, when compiled with SQLITE_PREFER_PROXY_LOCKING, ** setting the environment variable SQLITE_FORCE_PROXY_LOCKING to 1 will ** force proxy locking to be used for every database file opened, and 0 ** will force automatic proxy locking to be disabled for all database ** files (explicity calling the SQLITE_SET_LOCKPROXYFILE pragma or ** sqlite_file_control API is not affected by SQLITE_FORCE_PROXY_LOCKING). */ /* ** Proxy locking is only available on MacOSX */ #if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE /* ** The proxyLockingContext has the path and file structures for the remote ** and local proxy files in it */ typedef struct proxyLockingContext proxyLockingContext; struct proxyLockingContext { unixFile *conchFile; /* Open conch file */ char *conchFilePath; /* Name of the conch file */ unixFile *lockProxy; /* Open proxy lock file */ char *lockProxyPath; /* Name of the proxy lock file */ char *dbPath; /* Name of the open file */ int conchHeld; /* 1 if the conch is held, -1 if lockless */ void *oldLockingContext; /* Original lockingcontext to restore on close */ sqlite3_io_methods const *pOldMethod; /* Original I/O methods for close */ }; /* ** The proxy lock file path for the database at dbPath is written into lPath, ** which must point to valid, writable memory large enough for a maxLen length ** file path. */ static int proxyGetLockPath(const char *dbPath, char *lPath, size_t maxLen){ int len; int dbLen; int i; #ifdef LOCKPROXYDIR len = strlcpy(lPath, LOCKPROXYDIR, maxLen); #else # ifdef _CS_DARWIN_USER_TEMP_DIR { if( !confstr(_CS_DARWIN_USER_TEMP_DIR, lPath, maxLen) ){ OSTRACE4("GETLOCKPATH failed %s errno=%d pid=%d\n", lPath, errno, getpid()); return SQLITE_IOERR_LOCK; } len = strlcat(lPath, "sqliteplocks", maxLen); } # else len = strlcpy(lPath, "/tmp/", maxLen); # endif #endif if( lPath[len-1]!='/' ){ len = strlcat(lPath, "/", maxLen); } /* transform the db path to a unique cache name */ dbLen = (int)strlen(dbPath); for( i=0; i 0) ){ /* only mkdir if leaf dir != "." or "/" or ".." */ if( i-start>2 || (i-start==1 && buf[start] != '.' && buf[start] != '/') || (i-start==2 && buf[start] != '.' && buf[start+1] != '.') ){ buf[i]='\0'; if( mkdir(buf, SQLITE_DEFAULT_PROXYDIR_PERMISSIONS) ){ int err=errno; if( err!=EEXIST ) { OSTRACE5("CREATELOCKPATH FAILED creating %s, " "'%s' proxy lock path=%s pid=%d\n", buf, strerror(err), lockPath, getpid()); return err; } } } start=i+1; } buf[i] = lockPath[i]; } OSTRACE3("CREATELOCKPATH proxy lock path=%s pid=%d\n", lockPath, getpid()); return 0; } /* ** Create a new VFS file descriptor (stored in memory obtained from ** sqlite3_malloc) and open the file named "path" in the file descriptor. ** ** The caller is responsible not only for closing the file descriptor ** but also for freeing the memory associated with the file descriptor. */ static int proxyCreateUnixFile( const char *path, /* path for the new unixFile */ unixFile **ppFile, /* unixFile created and returned by ref */ int islockfile /* if non zero missing dirs will be created */ ) { int fd = -1; int dirfd = -1; unixFile *pNew; int rc = SQLITE_OK; int openFlags = O_RDWR | O_CREAT; sqlite3_vfs dummyVfs; int terrno = 0; UnixUnusedFd *pUnused = NULL; /* 1. first try to open/create the file ** 2. if that fails, and this is a lock file (not-conch), try creating ** the parent directories and then try again. ** 3. if that fails, try to open the file read-only ** otherwise return BUSY (if lock file) or CANTOPEN for the conch file */ pUnused = findReusableFd(path, openFlags); if( pUnused ){ fd = pUnused->fd; }else{ pUnused = sqlite3_malloc(sizeof(*pUnused)); if( !pUnused ){ return SQLITE_NOMEM; } } if( fd<0 ){ fd = open(path, openFlags, SQLITE_DEFAULT_FILE_PERMISSIONS); terrno = errno; if( fd<0 && errno==ENOENT && islockfile ){ if( proxyCreateLockPath(path) == SQLITE_OK ){ fd = open(path, openFlags, SQLITE_DEFAULT_FILE_PERMISSIONS); } } } if( fd<0 ){ openFlags = O_RDONLY; fd = open(path, openFlags, SQLITE_DEFAULT_FILE_PERMISSIONS); terrno = errno; } if( fd<0 ){ if( islockfile ){ return SQLITE_BUSY; } switch (terrno) { case EACCES: return SQLITE_PERM; case EIO: return SQLITE_IOERR_LOCK; /* even though it is the conch */ default: return SQLITE_CANTOPEN; } } pNew = (unixFile *)sqlite3_malloc(sizeof(*pNew)); if( pNew==NULL ){ rc = SQLITE_NOMEM; goto end_create_proxy; } memset(pNew, 0, sizeof(unixFile)); pNew->openFlags = openFlags; dummyVfs.pAppData = (void*)&autolockIoFinder; pUnused->fd = fd; pUnused->flags = openFlags; pNew->pUnused = pUnused; rc = fillInUnixFile(&dummyVfs, fd, dirfd, (sqlite3_file*)pNew, path, 0, 0); if( rc==SQLITE_OK ){ *ppFile = pNew; return SQLITE_OK; } end_create_proxy: close(fd); /* silently leak fd if error, we're already in error */ sqlite3_free(pNew); sqlite3_free(pUnused); return rc; } #ifdef SQLITE_TEST /* simulate multiple hosts by creating unique hostid file paths */ int sqlite3_hostid_num = 0; #endif #define PROXY_HOSTIDLEN 16 /* conch file host id length */ /* get the host ID via gethostuuid(), pHostID must point to PROXY_HOSTIDLEN ** bytes of writable memory. */ static int proxyGetHostID(unsigned char *pHostID, int *pError){ struct timespec timeout = {1, 0}; /* 1 sec timeout */ assert(PROXY_HOSTIDLEN == sizeof(uuid_t)); memset(pHostID, 0, PROXY_HOSTIDLEN); if( gethostuuid(pHostID, &timeout) ){ int err = errno; if( pError ){ *pError = err; } return SQLITE_IOERR; } #ifdef SQLITE_TEST /* simulate multiple hosts by creating unique hostid file paths */ if( sqlite3_hostid_num != 0){ pHostID[0] = (char)(pHostID[0] + (char)(sqlite3_hostid_num & 0xFF)); } #endif return SQLITE_OK; } /* The conch file contains the header, host id and lock file path */ #define PROXY_CONCHVERSION 2 /* 1-byte header, 16-byte host id, path */ #define PROXY_HEADERLEN 1 /* conch file header length */ #define PROXY_PATHINDEX (PROXY_HEADERLEN+PROXY_HOSTIDLEN) #define PROXY_MAXCONCHLEN (PROXY_HEADERLEN+PROXY_HOSTIDLEN+MAXPATHLEN) /* ** Takes an open conch file, copies the contents to a new path and then moves ** it back. The newly created file's file descriptor is assigned to the ** conch file structure and finally the original conch file descriptor is ** closed. Returns zero if successful. */ static int proxyBreakConchLock(unixFile *pFile, uuid_t myHostID){ proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; unixFile *conchFile = pCtx->conchFile; char tPath[MAXPATHLEN]; char buf[PROXY_MAXCONCHLEN]; char *cPath = pCtx->conchFilePath; size_t readLen = 0; size_t pathLen = 0; char errmsg[64] = ""; int fd = -1; int rc = -1; /* create a new path by replace the trailing '-conch' with '-break' */ pathLen = strlcpy(tPath, cPath, MAXPATHLEN); if( pathLen>MAXPATHLEN || pathLen<6 || (strlcpy(&tPath[pathLen-5], "break", 6) != 5) ){ sprintf(errmsg, "path error (len %d)", (int)pathLen); goto end_breaklock; } /* read the conch content */ readLen = pread(conchFile->h, buf, PROXY_MAXCONCHLEN, 0); if( readLenh); conchFile->h = fd; conchFile->openFlags = O_RDWR | O_CREAT; end_breaklock: if( rc ){ if( fd>=0 ){ unlink(tPath); close(fd); } fprintf(stderr, "failed to break stale lock on %s, %s\n", cPath, errmsg); } return rc; } /* Take the requested lock on the conch file and break a stale lock if the ** host id matches. */ static int proxyConchLock(unixFile *pFile, uuid_t myHostID, int lockType){ proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; unixFile *conchFile = pCtx->conchFile; int rc = SQLITE_OK; int nTries = 0; struct timespec conchModTime; do { rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, lockType); nTries ++; if( rc==SQLITE_BUSY ){ /* If the lock failed (busy): * 1st try: get the mod time of the conch, wait 0.5s and try again. * 2nd try: fail if the mod time changed or host id is different, wait * 10 sec and try again * 3rd try: break the lock unless the mod time has changed. */ struct stat buf; if( fstat(conchFile->h, &buf) ){ pFile->lastErrno = errno; return SQLITE_IOERR_LOCK; } if( nTries==1 ){ conchModTime = buf.st_mtimespec; usleep(500000); /* wait 0.5 sec and try the lock again*/ continue; } assert( nTries>1 ); if( conchModTime.tv_sec != buf.st_mtimespec.tv_sec || conchModTime.tv_nsec != buf.st_mtimespec.tv_nsec ){ return SQLITE_BUSY; } if( nTries==2 ){ char tBuf[PROXY_MAXCONCHLEN]; int len = pread(conchFile->h, tBuf, PROXY_MAXCONCHLEN, 0); if( len<0 ){ pFile->lastErrno = errno; return SQLITE_IOERR_LOCK; } if( len>PROXY_PATHINDEX && tBuf[0]==(char)PROXY_CONCHVERSION){ /* don't break the lock if the host id doesn't match */ if( 0!=memcmp(&tBuf[PROXY_HEADERLEN], myHostID, PROXY_HOSTIDLEN) ){ return SQLITE_BUSY; } }else{ /* don't break the lock on short read or a version mismatch */ return SQLITE_BUSY; } usleep(10000000); /* wait 10 sec and try the lock again */ continue; } assert( nTries==3 ); if( 0==proxyBreakConchLock(pFile, myHostID) ){ rc = SQLITE_OK; if( lockType==EXCLUSIVE_LOCK ){ rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, SHARED_LOCK); } if( !rc ){ rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, lockType); } } } } while( rc==SQLITE_BUSY && nTries<3 ); return rc; } /* Takes the conch by taking a shared lock and read the contents conch, if ** lockPath is non-NULL, the host ID and lock file path must match. A NULL ** lockPath means that the lockPath in the conch file will be used if the ** host IDs match, or a new lock path will be generated automatically ** and written to the conch file. */ static int proxyTakeConch(unixFile *pFile){ proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; if( pCtx->conchHeld!=0 ){ return SQLITE_OK; }else{ unixFile *conchFile = pCtx->conchFile; uuid_t myHostID; int pError = 0; char readBuf[PROXY_MAXCONCHLEN]; char lockPath[MAXPATHLEN]; char *tempLockPath = NULL; int rc = SQLITE_OK; int createConch = 0; int hostIdMatch = 0; int readLen = 0; int tryOldLockPath = 0; int forceNewLockPath = 0; OSTRACE4("TAKECONCH %d for %s pid=%d\n", conchFile->h, (pCtx->lockProxyPath ? pCtx->lockProxyPath : ":auto:"), getpid()); rc = proxyGetHostID(myHostID, &pError); if( (rc&0xff)==SQLITE_IOERR ){ pFile->lastErrno = pError; goto end_takeconch; } rc = proxyConchLock(pFile, myHostID, SHARED_LOCK); if( rc!=SQLITE_OK ){ goto end_takeconch; } /* read the existing conch file */ readLen = seekAndRead((unixFile*)conchFile, 0, readBuf, PROXY_MAXCONCHLEN); if( readLen<0 ){ /* I/O error: lastErrno set by seekAndRead */ pFile->lastErrno = conchFile->lastErrno; rc = SQLITE_IOERR_READ; goto end_takeconch; }else if( readLen<=(PROXY_HEADERLEN+PROXY_HOSTIDLEN) || readBuf[0]!=(char)PROXY_CONCHVERSION ){ /* a short read or version format mismatch means we need to create a new ** conch file. */ createConch = 1; } /* if the host id matches and the lock path already exists in the conch ** we'll try to use the path there, if we can't open that path, we'll ** retry with a new auto-generated path */ do { /* in case we need to try again for an :auto: named lock file */ if( !createConch && !forceNewLockPath ){ hostIdMatch = !memcmp(&readBuf[PROXY_HEADERLEN], myHostID, PROXY_HOSTIDLEN); /* if the conch has data compare the contents */ if( !pCtx->lockProxyPath ){ /* for auto-named local lock file, just check the host ID and we'll ** use the local lock file path that's already in there */ if( hostIdMatch ){ size_t pathLen = (readLen - PROXY_PATHINDEX); if( pathLen>=MAXPATHLEN ){ pathLen=MAXPATHLEN-1; } memcpy(lockPath, &readBuf[PROXY_PATHINDEX], pathLen); lockPath[pathLen] = 0; tempLockPath = lockPath; tryOldLockPath = 1; /* create a copy of the lock path if the conch is taken */ goto end_takeconch; } }else if( hostIdMatch && !strncmp(pCtx->lockProxyPath, &readBuf[PROXY_PATHINDEX], readLen-PROXY_PATHINDEX) ){ /* conch host and lock path match */ goto end_takeconch; } } /* if the conch isn't writable and doesn't match, we can't take it */ if( (conchFile->openFlags&O_RDWR) == 0 ){ rc = SQLITE_BUSY; goto end_takeconch; } /* either the conch didn't match or we need to create a new one */ if( !pCtx->lockProxyPath ){ proxyGetLockPath(pCtx->dbPath, lockPath, MAXPATHLEN); tempLockPath = lockPath; /* create a copy of the lock path _only_ if the conch is taken */ } /* update conch with host and path (this will fail if other process ** has a shared lock already), if the host id matches, use the big ** stick. */ futimes(conchFile->h, NULL); if( hostIdMatch && !createConch ){ if( conchFile->pLock && conchFile->pLock->cnt>1 ){ /* We are trying for an exclusive lock but another thread in this ** same process is still holding a shared lock. */ rc = SQLITE_BUSY; } else { rc = proxyConchLock(pFile, myHostID, EXCLUSIVE_LOCK); } }else{ rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, EXCLUSIVE_LOCK); } if( rc==SQLITE_OK ){ char writeBuffer[PROXY_MAXCONCHLEN]; int writeSize = 0; writeBuffer[0] = (char)PROXY_CONCHVERSION; memcpy(&writeBuffer[PROXY_HEADERLEN], myHostID, PROXY_HOSTIDLEN); if( pCtx->lockProxyPath!=NULL ){ strlcpy(&writeBuffer[PROXY_PATHINDEX], pCtx->lockProxyPath, MAXPATHLEN); }else{ strlcpy(&writeBuffer[PROXY_PATHINDEX], tempLockPath, MAXPATHLEN); } writeSize = PROXY_PATHINDEX + strlen(&writeBuffer[PROXY_PATHINDEX]); ftruncate(conchFile->h, writeSize); rc = unixWrite((sqlite3_file *)conchFile, writeBuffer, writeSize, 0); fsync(conchFile->h); /* If we created a new conch file (not just updated the contents of a ** valid conch file), try to match the permissions of the database */ if( rc==SQLITE_OK && createConch ){ struct stat buf; int err = fstat(pFile->h, &buf); if( err==0 ){ mode_t cmode = buf.st_mode&(S_IRUSR|S_IWUSR | S_IRGRP|S_IWGRP | S_IROTH|S_IWOTH); /* try to match the database file R/W permissions, ignore failure */ #ifndef SQLITE_PROXY_DEBUG fchmod(conchFile->h, cmode); #else if( fchmod(conchFile->h, cmode)!=0 ){ int code = errno; fprintf(stderr, "fchmod %o FAILED with %d %s\n", cmode, code, strerror(code)); } else { fprintf(stderr, "fchmod %o SUCCEDED\n",cmode); } }else{ int code = errno; fprintf(stderr, "STAT FAILED[%d] with %d %s\n", err, code, strerror(code)); #endif } } } conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, SHARED_LOCK); end_takeconch: OSTRACE2("TRANSPROXY: CLOSE %d\n", pFile->h); if( rc==SQLITE_OK && pFile->openFlags ){ if( pFile->h>=0 ){ #ifdef STRICT_CLOSE_ERROR if( close(pFile->h) ){ pFile->lastErrno = errno; return SQLITE_IOERR_CLOSE; } #else close(pFile->h); /* silently leak fd if fail */ #endif } pFile->h = -1; int fd = open(pCtx->dbPath, pFile->openFlags, SQLITE_DEFAULT_FILE_PERMISSIONS); OSTRACE2("TRANSPROXY: OPEN %d\n", fd); if( fd>=0 ){ pFile->h = fd; }else{ rc=SQLITE_CANTOPEN; /* SQLITE_BUSY? proxyTakeConch called during locking */ } } if( rc==SQLITE_OK && !pCtx->lockProxy ){ char *path = tempLockPath ? tempLockPath : pCtx->lockProxyPath; rc = proxyCreateUnixFile(path, &pCtx->lockProxy, 1); if( rc!=SQLITE_OK && rc!=SQLITE_NOMEM && tryOldLockPath ){ /* we couldn't create the proxy lock file with the old lock file path ** so try again via auto-naming */ forceNewLockPath = 1; tryOldLockPath = 0; continue; /* go back to the do {} while start point, try again */ } } if( rc==SQLITE_OK ){ /* Need to make a copy of path if we extracted the value ** from the conch file or the path was allocated on the stack */ if( tempLockPath ){ pCtx->lockProxyPath = sqlite3DbStrDup(0, tempLockPath); if( !pCtx->lockProxyPath ){ rc = SQLITE_NOMEM; } } } if( rc==SQLITE_OK ){ pCtx->conchHeld = 1; if( pCtx->lockProxy->pMethod == &afpIoMethods ){ afpLockingContext *afpCtx; afpCtx = (afpLockingContext *)pCtx->lockProxy->lockingContext; afpCtx->dbPath = pCtx->lockProxyPath; } } else { conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, NO_LOCK); } OSTRACE3("TAKECONCH %d %s\n", conchFile->h, rc==SQLITE_OK?"ok":"failed"); return rc; } while (1); /* in case we need to retry the :auto: lock file - we should never get here except via the 'continue' call. */ } } /* ** If pFile holds a lock on a conch file, then release that lock. */ static int proxyReleaseConch(unixFile *pFile){ int rc; /* Subroutine return code */ proxyLockingContext *pCtx; /* The locking context for the proxy lock */ unixFile *conchFile; /* Name of the conch file */ pCtx = (proxyLockingContext *)pFile->lockingContext; conchFile = pCtx->conchFile; OSTRACE4("RELEASECONCH %d for %s pid=%d\n", conchFile->h, (pCtx->lockProxyPath ? pCtx->lockProxyPath : ":auto:"), getpid()); if( pCtx->conchHeld>0 ){ rc = conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, NO_LOCK); } pCtx->conchHeld = 0; OSTRACE3("RELEASECONCH %d %s\n", conchFile->h, (rc==SQLITE_OK ? "ok" : "failed")); return rc; } /* ** Given the name of a database file, compute the name of its conch file. ** Store the conch filename in memory obtained from sqlite3_malloc(). ** Make *pConchPath point to the new name. Return SQLITE_OK on success ** or SQLITE_NOMEM if unable to obtain memory. ** ** The caller is responsible for ensuring that the allocated memory ** space is eventually freed. ** ** *pConchPath is set to NULL if a memory allocation error occurs. */ static int proxyCreateConchPathname(char *dbPath, char **pConchPath){ int i; /* Loop counter */ int len = (int)strlen(dbPath); /* Length of database filename - dbPath */ char *conchPath; /* buffer in which to construct conch name */ /* Allocate space for the conch filename and initialize the name to ** the name of the original database file. */ *pConchPath = conchPath = (char *)sqlite3_malloc(len + 8); if( conchPath==0 ){ return SQLITE_NOMEM; } memcpy(conchPath, dbPath, len+1); /* now insert a "." before the last / character */ for( i=(len-1); i>=0; i-- ){ if( conchPath[i]=='/' ){ i++; break; } } conchPath[i]='.'; while ( ilockingContext; char *oldPath = pCtx->lockProxyPath; int rc = SQLITE_OK; if( pFile->locktype!=NO_LOCK ){ return SQLITE_BUSY; } /* nothing to do if the path is NULL, :auto: or matches the existing path */ if( !path || path[0]=='\0' || !strcmp(path, ":auto:") || (oldPath && !strncmp(oldPath, path, MAXPATHLEN)) ){ return SQLITE_OK; }else{ unixFile *lockProxy = pCtx->lockProxy; pCtx->lockProxy=NULL; pCtx->conchHeld = 0; if( lockProxy!=NULL ){ rc=lockProxy->pMethod->xClose((sqlite3_file *)lockProxy); if( rc ) return rc; sqlite3_free(lockProxy); } sqlite3_free(oldPath); pCtx->lockProxyPath = sqlite3DbStrDup(0, path); } return rc; } /* ** pFile is a file that has been opened by a prior xOpen call. dbPath ** is a string buffer at least MAXPATHLEN+1 characters in size. ** ** This routine find the filename associated with pFile and writes it ** int dbPath. */ static int proxyGetDbPathForUnixFile(unixFile *pFile, char *dbPath){ #if defined(__APPLE__) if( pFile->pMethod == &afpIoMethods ){ /* afp style keeps a reference to the db path in the filePath field ** of the struct */ assert( (int)strlen((char*)pFile->lockingContext)<=MAXPATHLEN ); strlcpy(dbPath, ((afpLockingContext *)pFile->lockingContext)->dbPath, MAXPATHLEN); } else #endif if( pFile->pMethod == &dotlockIoMethods ){ /* dot lock style uses the locking context to store the dot lock ** file path */ int len = strlen((char *)pFile->lockingContext) - strlen(DOTLOCK_SUFFIX); memcpy(dbPath, (char *)pFile->lockingContext, len + 1); }else{ /* all other styles use the locking context to store the db file path */ assert( strlen((char*)pFile->lockingContext)<=MAXPATHLEN ); strlcpy(dbPath, (char *)pFile->lockingContext, MAXPATHLEN); } return SQLITE_OK; } /* ** Takes an already filled in unix file and alters it so all file locking ** will be performed on the local proxy lock file. The following fields ** are preserved in the locking context so that they can be restored and ** the unix structure properly cleaned up at close time: ** ->lockingContext ** ->pMethod */ static int proxyTransformUnixFile(unixFile *pFile, const char *path) { proxyLockingContext *pCtx; char dbPath[MAXPATHLEN+1]; /* Name of the database file */ char *lockPath=NULL; int rc = SQLITE_OK; if( pFile->locktype!=NO_LOCK ){ return SQLITE_BUSY; } proxyGetDbPathForUnixFile(pFile, dbPath); if( !path || path[0]=='\0' || !strcmp(path, ":auto:") ){ lockPath=NULL; }else{ lockPath=(char *)path; } OSTRACE4("TRANSPROXY %d for %s pid=%d\n", pFile->h, (lockPath ? lockPath : ":auto:"), getpid()); pCtx = sqlite3_malloc( sizeof(*pCtx) ); if( pCtx==0 ){ return SQLITE_NOMEM; } memset(pCtx, 0, sizeof(*pCtx)); rc = proxyCreateConchPathname(dbPath, &pCtx->conchFilePath); if( rc==SQLITE_OK ){ rc = proxyCreateUnixFile(pCtx->conchFilePath, &pCtx->conchFile, 0); if( rc==SQLITE_CANTOPEN && ((pFile->openFlags&O_RDWR) == 0) ){ /* if (a) the open flags are not O_RDWR, (b) the conch isn't there, and ** (c) the file system is read-only, then enable no-locking access. ** Ugh, since O_RDONLY==0x0000 we test for !O_RDWR since unixOpen asserts ** that openFlags will have only one of O_RDONLY or O_RDWR. */ struct statfs fsInfo; struct stat conchInfo; int goLockless = 0; if( stat(pCtx->conchFilePath, &conchInfo) == -1 ) { int err = errno; if( (err==ENOENT) && (statfs(dbPath, &fsInfo) != -1) ){ goLockless = (fsInfo.f_flags&MNT_RDONLY) == MNT_RDONLY; } } if( goLockless ){ pCtx->conchHeld = -1; /* read only FS/ lockless */ rc = SQLITE_OK; } } } if( rc==SQLITE_OK && lockPath ){ pCtx->lockProxyPath = sqlite3DbStrDup(0, lockPath); } if( rc==SQLITE_OK ){ pCtx->dbPath = sqlite3DbStrDup(0, dbPath); if( pCtx->dbPath==NULL ){ rc = SQLITE_NOMEM; } } if( rc==SQLITE_OK ){ /* all memory is allocated, proxys are created and assigned, ** switch the locking context and pMethod then return. */ pCtx->oldLockingContext = pFile->lockingContext; pFile->lockingContext = pCtx; pCtx->pOldMethod = pFile->pMethod; pFile->pMethod = &proxyIoMethods; }else{ if( pCtx->conchFile ){ pCtx->conchFile->pMethod->xClose((sqlite3_file *)pCtx->conchFile); sqlite3_free(pCtx->conchFile); } sqlite3_free(pCtx->lockProxyPath); sqlite3_free(pCtx->conchFilePath); sqlite3_free(pCtx); } OSTRACE3("TRANSPROXY %d %s\n", pFile->h, (rc==SQLITE_OK ? "ok" : "failed")); return rc; } /* ** This routine handles sqlite3_file_control() calls that are specific ** to proxy locking. */ static int proxyFileControl(sqlite3_file *id, int op, void *pArg){ switch( op ){ case SQLITE_GET_LOCKPROXYFILE: { unixFile *pFile = (unixFile*)id; if( pFile->pMethod == &proxyIoMethods ){ proxyLockingContext *pCtx = (proxyLockingContext*)pFile->lockingContext; proxyTakeConch(pFile); if( pCtx->lockProxyPath ){ *(const char **)pArg = pCtx->lockProxyPath; }else{ *(const char **)pArg = ":auto: (not held)"; } } else { *(const char **)pArg = NULL; } return SQLITE_OK; } case SQLITE_SET_LOCKPROXYFILE: { unixFile *pFile = (unixFile*)id; int rc = SQLITE_OK; int isProxyStyle = (pFile->pMethod == &proxyIoMethods); if( pArg==NULL || (const char *)pArg==0 ){ if( isProxyStyle ){ /* turn off proxy locking - not supported */ rc = SQLITE_ERROR /*SQLITE_PROTOCOL? SQLITE_MISUSE?*/; }else{ /* turn off proxy locking - already off - NOOP */ rc = SQLITE_OK; } }else{ const char *proxyPath = (const char *)pArg; if( isProxyStyle ){ proxyLockingContext *pCtx = (proxyLockingContext*)pFile->lockingContext; if( !strcmp(pArg, ":auto:") || (pCtx->lockProxyPath && !strncmp(pCtx->lockProxyPath, proxyPath, MAXPATHLEN)) ){ rc = SQLITE_OK; }else{ rc = switchLockProxyPath(pFile, proxyPath); } }else{ /* turn on proxy file locking */ rc = proxyTransformUnixFile(pFile, proxyPath); } } return rc; } default: { assert( 0 ); /* The call assures that only valid opcodes are sent */ } } /*NOTREACHED*/ return SQLITE_ERROR; } /* ** Within this division (the proxying locking implementation) the procedures ** above this point are all utilities. The lock-related methods of the ** proxy-locking sqlite3_io_method object follow. */ /* ** This routine checks if there is a RESERVED lock held on the specified ** file by this or any other process. If such a lock is held, set *pResOut ** to a non-zero value otherwise *pResOut is set to zero. The return value ** is set to SQLITE_OK unless an I/O error occurs during lock checking. */ static int proxyCheckReservedLock(sqlite3_file *id, int *pResOut) { unixFile *pFile = (unixFile*)id; int rc = proxyTakeConch(pFile); if( rc==SQLITE_OK ){ proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; if( pCtx->conchHeld>0 ){ unixFile *proxy = pCtx->lockProxy; return proxy->pMethod->xCheckReservedLock((sqlite3_file*)proxy, pResOut); }else{ /* conchHeld < 0 is lockless */ pResOut=0; } } return rc; } /* ** Lock the file with the lock specified by parameter locktype - one ** of the following: ** ** (1) SHARED_LOCK ** (2) RESERVED_LOCK ** (3) PENDING_LOCK ** (4) EXCLUSIVE_LOCK ** ** Sometimes when requesting one lock state, additional lock states ** are inserted in between. The locking might fail on one of the later ** transitions leaving the lock state different from what it started but ** still short of its goal. The following chart shows the allowed ** transitions and the inserted intermediate states: ** ** UNLOCKED -> SHARED ** SHARED -> RESERVED ** SHARED -> (PENDING) -> EXCLUSIVE ** RESERVED -> (PENDING) -> EXCLUSIVE ** PENDING -> EXCLUSIVE ** ** This routine will only increase a lock. Use the sqlite3OsUnlock() ** routine to lower a locking level. */ static int proxyLock(sqlite3_file *id, int locktype) { unixFile *pFile = (unixFile*)id; int rc = proxyTakeConch(pFile); if( rc==SQLITE_OK ){ proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; if( pCtx->conchHeld>0 ){ unixFile *proxy = pCtx->lockProxy; rc = proxy->pMethod->xLock((sqlite3_file*)proxy, locktype); pFile->locktype = proxy->locktype; }else{ /* conchHeld < 0 is lockless */ } } return rc; } /* ** Lower the locking level on file descriptor pFile to locktype. locktype ** must be either NO_LOCK or SHARED_LOCK. ** ** If the locking level of the file descriptor is already at or below ** the requested locking level, this routine is a no-op. */ static int proxyUnlock(sqlite3_file *id, int locktype) { unixFile *pFile = (unixFile*)id; int rc = proxyTakeConch(pFile); if( rc==SQLITE_OK ){ proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; if( pCtx->conchHeld>0 ){ unixFile *proxy = pCtx->lockProxy; rc = proxy->pMethod->xUnlock((sqlite3_file*)proxy, locktype); pFile->locktype = proxy->locktype; }else{ /* conchHeld < 0 is lockless */ } } return rc; } /* ** Close a file that uses proxy locks. */ static int proxyClose(sqlite3_file *id) { if( id ){ unixFile *pFile = (unixFile*)id; proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; unixFile *lockProxy = pCtx->lockProxy; unixFile *conchFile = pCtx->conchFile; int rc = SQLITE_OK; if( lockProxy ){ rc = lockProxy->pMethod->xUnlock((sqlite3_file*)lockProxy, NO_LOCK); if( rc ) return rc; rc = lockProxy->pMethod->xClose((sqlite3_file*)lockProxy); if( rc ) return rc; sqlite3_free(lockProxy); pCtx->lockProxy = 0; } if( conchFile ){ if( pCtx->conchHeld ){ rc = proxyReleaseConch(pFile); if( rc ) return rc; } rc = conchFile->pMethod->xClose((sqlite3_file*)conchFile); if( rc ) return rc; sqlite3_free(conchFile); } sqlite3_free(pCtx->lockProxyPath); sqlite3_free(pCtx->conchFilePath); sqlite3_free(pCtx->dbPath); /* restore the original locking context and pMethod then close it */ pFile->lockingContext = pCtx->oldLockingContext; pFile->pMethod = pCtx->pOldMethod; sqlite3_free(pCtx); return pFile->pMethod->xClose(id); } return SQLITE_OK; } #endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */ /* ** The proxy locking style is intended for use with AFP filesystems. ** And since AFP is only supported on MacOSX, the proxy locking is also ** restricted to MacOSX. ** ** ******************* End of the proxy lock implementation ********************** ******************************************************************************/ /* ** Initialize the operating system interface. ** ** This routine registers all VFS implementations for unix-like operating ** systems. This routine, and the sqlite3_os_end() routine that follows, ** should be the only routines in this file that are visible from other ** files. ** ** This routine is called once during SQLite initialization and by a ** single thread. The memory allocation and mutex subsystems have not ** necessarily been initialized when this routine is called, and so they ** should not be used. */ int sqlite3_os_init(void){ /* ** The following macro defines an initializer for an sqlite3_vfs object. ** The name of the VFS is NAME. The pAppData is a pointer to a pointer ** to the "finder" function. (pAppData is a pointer to a pointer because ** silly C90 rules prohibit a void* from being cast to a function pointer ** and so we have to go through the intermediate pointer to avoid problems ** when compiling with -pedantic-errors on GCC.) ** ** The FINDER parameter to this macro is the name of the pointer to the ** finder-function. The finder-function returns a pointer to the ** sqlite_io_methods object that implements the desired locking ** behaviors. See the division above that contains the IOMETHODS ** macro for addition information on finder-functions. ** ** Most finders simply return a pointer to a fixed sqlite3_io_methods ** object. But the "autolockIoFinder" available on MacOSX does a little ** more than that; it looks at the filesystem type that hosts the ** database file and tries to choose an locking method appropriate for ** that filesystem time. */ #define UNIXVFS(VFSNAME, FINDER) { \ 1, /* iVersion */ \ sizeof(unixFile), /* szOsFile */ \ MAX_PATHNAME, /* mxPathname */ \ 0, /* pNext */ \ VFSNAME, /* zName */ \ (void*)&FINDER, /* pAppData */ \ unixOpen, /* xOpen */ \ unixDelete, /* xDelete */ \ unixAccess, /* xAccess */ \ unixFullPathname, /* xFullPathname */ \ unixDlOpen, /* xDlOpen */ \ unixDlError, /* xDlError */ \ unixDlSym, /* xDlSym */ \ unixDlClose, /* xDlClose */ \ unixRandomness, /* xRandomness */ \ unixSleep, /* xSleep */ \ unixCurrentTime, /* xCurrentTime */ \ unixGetLastError /* xGetLastError */ \ } /* ** All default VFSes for unix are contained in the following array. ** ** Note that the sqlite3_vfs.pNext field of the VFS object is modified ** by the SQLite core when the VFS is registered. So the following ** array cannot be const. */ static sqlite3_vfs aVfs[] = { #if SQLITE_ENABLE_LOCKING_STYLE && (OS_VXWORKS || defined(__APPLE__)) UNIXVFS("unix", autolockIoFinder ), #else UNIXVFS("unix", posixIoFinder ), #endif UNIXVFS("unix-none", nolockIoFinder ), UNIXVFS("unix-dotfile", dotlockIoFinder ), #if OS_VXWORKS UNIXVFS("unix-namedsem", semIoFinder ), #endif #if SQLITE_ENABLE_LOCKING_STYLE UNIXVFS("unix-posix", posixIoFinder ), #if !OS_VXWORKS UNIXVFS("unix-flock", flockIoFinder ), #endif #endif #if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__) UNIXVFS("unix-afp", afpIoFinder ), UNIXVFS("unix-nfs", nfsIoFinder ), UNIXVFS("unix-proxy", proxyIoFinder ), #endif }; unsigned int i; /* Loop counter */ /* Register all VFSes defined in the aVfs[] array */ for(i=0; i<(sizeof(aVfs)/sizeof(sqlite3_vfs)); i++){ sqlite3_vfs_register(&aVfs[i], i==0); } return SQLITE_OK; } /* ** Shutdown the operating system interface. ** ** Some operating systems might need to do some cleanup in this routine, ** to release dynamically allocated objects. But not on unix. ** This routine is a no-op for unix. */ int sqlite3_os_end(void){ return SQLITE_OK; } #endif /* SQLITE_OS_UNIX */