Index: src/os_unix.c ================================================================== --- src/os_unix.c +++ src/os_unix.c @@ -210,10 +210,11 @@ int lastErrno; /* The unix errno from last I/O error */ void *lockingContext; /* Locking style specific state */ UnixUnusedFd *pUnused; /* Pre-allocated UnixUnusedFd */ const char *zPath; /* Name of the file */ unixShm *pShm; /* Shared memory segment information */ + int readOnlyShm; /* True to open shared-memory read-only */ int szChunk; /* Configured by FCNTL_CHUNK_SIZE */ #if SQLITE_ENABLE_LOCKING_STYLE int openFlags; /* The flags specified at open() */ #endif #if SQLITE_ENABLE_LOCKING_STYLE || defined(__APPLE__) @@ -3450,10 +3451,14 @@ return SQLITE_OK; } case SQLITE_FCNTL_SIZE_HINT: { return fcntlSizeHint((unixFile *)id, *(i64 *)pArg); } + case SQLITE_FCNTL_READONLY_SHM: { + ((unixFile*)id)->readOnlyShm = (pArg!=0); + 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. @@ -3539,10 +3544,11 @@ int szRegion; /* Size of shared-memory regions */ int nRegion; /* Size of array apRegion */ char **apRegion; /* Array of mapped shared-memory regions */ int nRef; /* Number of unixShm objects pointing to this */ unixShm *pFirst; /* All unixShm objects pointing to this */ + u8 readOnly; /* True if this is a read-only mapping */ #ifdef SQLITE_DEBUG u8 exclMask; /* Mask of exclusive locks held */ u8 sharedMask; /* Mask of shared locks held */ u8 nextShmId; /* Next available unixShm.id value */ #endif @@ -3778,31 +3784,50 @@ rc = SQLITE_NOMEM; goto shm_open_err; } if( pInode->bProcessLock==0 ){ - pShmNode->h = robust_open(zShmFilename, O_RDWR|O_CREAT, - (sStat.st_mode & 0777)); + int flags = (pDbFd->readOnlyShm ? O_RDONLY : O_RDWR|O_CREAT); + pShmNode->h = robust_open(zShmFilename, flags, (sStat.st_mode & 0777)); if( pShmNode->h<0 ){ rc = unixLogError(SQLITE_CANTOPEN_BKPT, "open", zShmFilename); goto shm_open_err; } + pShmNode->readOnly = pDbFd->readOnlyShm; /* Check to see if another process is holding the dead-man switch. - ** If not, truncate the file to zero length. - */ - rc = SQLITE_OK; - if( unixShmSystemLock(pShmNode, F_WRLCK, UNIX_SHM_DMS, 1)==SQLITE_OK ){ - if( robust_ftruncate(pShmNode->h, 0) ){ - rc = unixLogError(SQLITE_IOERR_SHMOPEN, "ftruncate", zShmFilename); - } - } - if( rc==SQLITE_OK ){ - rc = unixShmSystemLock(pShmNode, F_RDLCK, UNIX_SHM_DMS, 1); - } - if( rc ) goto shm_open_err; - } + ** If not, zero the first few bytes of the shared-memory file to make + ** sure it is not mistaken for valid by code in wal.c. Except, if this + ** is a read-only connection to the shared-memory then it is not possible + ** to check check if another process is holding a read-lock on the DMS + ** byte, as we cannot attempt a write-lock via a read-only file + ** descriptor. So in this case, we just assume the shared-memory + ** contents are Ok and proceed. */ + if( pShmNode->readOnly==0 ){ + rc = SQLITE_OK; + if( unixShmSystemLock(pShmNode, F_WRLCK, UNIX_SHM_DMS, 1)==SQLITE_OK ){ + if( pDbFd->readOnlyShm ){ + rc = SQLITE_IOERR_SHMOPEN; + }else if( 4!=osWrite(pShmNode->h, "\00\00\00\00", 4) ){ + rc = unixLogError(SQLITE_IOERR_SHMOPEN, "ftruncate", zShmFilename); + } + } + if( rc==SQLITE_OK ){ + rc = unixShmSystemLock(pShmNode, F_RDLCK, UNIX_SHM_DMS, 1); + } + if( rc ) goto shm_open_err; + } + } + } + + /* If the unixShmNode is read-only, but SQLITE_FCNTL_READONLY_SHM has not + ** been set for file-descriptor pDbFd, return an error. The wal.c module + ** will then call this function again with SQLITE_FCNTL_READONLY_SHM set. + */ + else if( pShmNode->readOnly && !pDbFd->readOnlyShm ){ + rc = SQLITE_IOERR_SHMOPEN; + goto shm_open_err; } /* Make the new connection a child of the unixShmNode */ p->pShmNode = pShmNode; #ifdef SQLITE_DEBUG @@ -3921,11 +3946,11 @@ } pShmNode->apRegion = apNew; while(pShmNode->nRegion<=iRegion){ void *pMem; if( pShmNode->h>=0 ){ - pMem = mmap(0, szRegion, PROT_READ|PROT_WRITE, + pMem = mmap(0, szRegion, PROT_READ|(!pShmNode->readOnly?PROT_WRITE:0), MAP_SHARED, pShmNode->h, pShmNode->nRegion*szRegion ); if( pMem==MAP_FAILED ){ rc = unixLogError(SQLITE_IOERR_SHMMAP, "mmap", pShmNode->zFilename); goto shmpage_out; Index: src/sqlite.h.in ================================================================== --- src/sqlite.h.in +++ src/sqlite.h.in @@ -452,10 +452,13 @@ #define SQLITE_IOERR_SEEK (SQLITE_IOERR | (22<<8)) #define SQLITE_LOCKED_SHAREDCACHE (SQLITE_LOCKED | (1<<8)) #define SQLITE_BUSY_RECOVERY (SQLITE_BUSY | (1<<8)) #define SQLITE_CANTOPEN_NOTEMPDIR (SQLITE_CANTOPEN | (1<<8)) +#define SQLITE_READONLY_RECOVERY (SQLITE_READONLY | (1<<8)) +#define SQLITE_READONLY_CANTLOCK (SQLITE_READONLY | (2<<8)) + /* ** CAPI3REF: Flags For File Open Operations ** ** These bit values are intended for use in the ** 3rd parameter to the [sqlite3_open_v2()] interface and @@ -740,10 +743,11 @@ #define SQLITE_LAST_ERRNO 4 #define SQLITE_FCNTL_SIZE_HINT 5 #define SQLITE_FCNTL_CHUNK_SIZE 6 #define SQLITE_FCNTL_FILE_POINTER 7 #define SQLITE_FCNTL_SYNC_OMITTED 8 +#define SQLITE_FCNTL_READONLY_SHM 9 /* ** CAPI3REF: Mutex Handle ** Index: src/test1.c ================================================================== --- src/test1.c +++ src/test1.c @@ -161,10 +161,13 @@ case SQLITE_IOERR_NOMEM: zName = "SQLITE_IOERR_NOMEM"; break; case SQLITE_IOERR_ACCESS: zName = "SQLITE_IOERR_ACCESS"; break; case SQLITE_IOERR_CHECKRESERVEDLOCK: zName = "SQLITE_IOERR_CHECKRESERVEDLOCK"; break; case SQLITE_IOERR_LOCK: zName = "SQLITE_IOERR_LOCK"; break; + + case SQLITE_READONLY_RECOVERY: zName = "SQLITE_READONLY_RECOVERY"; break; + case SQLITE_READONLY_CANTLOCK: zName = "SQLITE_READONLY_CANTLOCK"; break; default: zName = "SQLITE_Unknown"; break; } return zName; } #define t1ErrorName sqlite3TestErrorName Index: src/wal.c ================================================================== --- src/wal.c +++ src/wal.c @@ -418,10 +418,11 @@ i16 readLock; /* Which read lock is being held. -1 for none */ u8 exclusiveMode; /* Non-zero if connection is in exclusive mode */ u8 writeLock; /* True if in a write transaction */ u8 ckptLock; /* True if holding a checkpoint lock */ u8 readOnly; /* True if the WAL file is open read-only */ + u8 readOnlyShm; /* True if the SHM file is open read-only */ WalIndexHdr hdr; /* Wal-index header for current transaction */ const char *zWalName; /* Name of WAL file */ u32 nCkpt; /* Checkpoint sequence counter in the wal-header */ #ifdef SQLITE_DEBUG u8 lockError; /* True if a locking error has occurred */ @@ -526,10 +527,20 @@ if( !pWal->apWiData[iPage] ) rc = SQLITE_NOMEM; }else{ rc = sqlite3OsShmMap(pWal->pDbFd, iPage, WALINDEX_PGSZ, pWal->writeLock, (void volatile **)&pWal->apWiData[iPage] ); + if( rc==SQLITE_CANTOPEN && iPage==0 ){ + sqlite3OsFileControl(pWal->pDbFd, SQLITE_FCNTL_READONLY_SHM, (void*)1); + rc = sqlite3OsShmMap(pWal->pDbFd, iPage, WALINDEX_PGSZ, + pWal->writeLock, (void volatile **)&pWal->apWiData[iPage] + ); + if( rc==SQLITE_OK ){ + pWal->readOnly = pWal->readOnlyShm = 1; + } + sqlite3OsFileControl(pWal->pDbFd, SQLITE_FCNTL_READONLY_SHM, (void*)0); + } } } *ppPage = pWal->apWiData[iPage]; assert( iPage==0 || *ppPage || rc!=SQLITE_OK ); @@ -770,19 +781,21 @@ SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED); WALTRACE(("WAL%p: release SHARED-%s\n", pWal, walLockName(lockIdx))); } static int walLockExclusive(Wal *pWal, int lockIdx, int n){ int rc; + assert( pWal->readOnlyShm==0 ); if( pWal->exclusiveMode ) return SQLITE_OK; rc = sqlite3OsShmLock(pWal->pDbFd, lockIdx, n, SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE); WALTRACE(("WAL%p: acquire EXCLUSIVE-%s cnt=%d %s\n", pWal, walLockName(lockIdx), n, rc ? "failed" : "ok")); VVA_ONLY( pWal->lockError = (u8)(rc!=SQLITE_OK && rc!=SQLITE_BUSY); ) return rc; } static void walUnlockExclusive(Wal *pWal, int lockIdx, int n){ + assert( pWal->readOnlyShm==0 ); if( pWal->exclusiveMode ) return; (void)sqlite3OsShmLock(pWal->pDbFd, lockIdx, n, SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE); WALTRACE(("WAL%p: release EXCLUSIVE-%s cnt=%d\n", pWal, walLockName(lockIdx), n)); @@ -1054,10 +1067,11 @@ */ assert( pWal->ckptLock==1 || pWal->ckptLock==0 ); assert( WAL_ALL_BUT_WRITE==WAL_WRITE_LOCK+1 ); assert( WAL_CKPT_LOCK==WAL_ALL_BUT_WRITE ); assert( pWal->writeLock ); + assert( pWal->readOnlyShm==0 ); iLock = WAL_ALL_BUT_WRITE + pWal->ckptLock; nLock = SQLITE_SHM_NLOCK - iLock; rc = walLockExclusive(pWal, iLock, nLock); if( rc ){ return rc; @@ -1902,28 +1916,35 @@ ** being modified by another thread or process. */ badHdr = (page0 ? walIndexTryHdr(pWal, pChanged) : 1); /* If the first attempt failed, it might have been due to a race - ** with a writer. So get a WRITE lock and try again. + ** with a writer. So lock the WAL_WRITE_LOCK byte and try again. */ assert( badHdr==0 || pWal->writeLock==0 ); - if( badHdr && SQLITE_OK==(rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1)) ){ - pWal->writeLock = 1; - if( SQLITE_OK==(rc = walIndexPage(pWal, 0, &page0)) ){ - badHdr = walIndexTryHdr(pWal, pChanged); - if( badHdr ){ - /* If the wal-index header is still malformed even while holding - ** a WRITE lock, it can only mean that the header is corrupted and - ** needs to be reconstructed. So run recovery to do exactly that. - */ - rc = walIndexRecover(pWal); - *pChanged = 1; + if( badHdr ){ + if( pWal->readOnlyShm ){ + if( SQLITE_OK==(rc = walLockShared(pWal, WAL_WRITE_LOCK)) ){ + walUnlockShared(pWal, WAL_WRITE_LOCK); + rc = SQLITE_READONLY_RECOVERY; + } + }else if( SQLITE_OK==(rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1)) ){ + pWal->writeLock = 1; + if( SQLITE_OK==(rc = walIndexPage(pWal, 0, &page0)) ){ + badHdr = walIndexTryHdr(pWal, pChanged); + if( badHdr ){ + /* If the wal-index header is still malformed even while holding + ** a WRITE lock, it can only mean that the header is corrupted and + ** needs to be reconstructed. So run recovery to do exactly that. + */ + rc = walIndexRecover(pWal); + *pChanged = 1; + } } + pWal->writeLock = 0; + walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1); } - pWal->writeLock = 0; - walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1); } /* If the header is read successfully, check the version number to make ** sure the wal-index was not constructed with some future format that ** this version of SQLite cannot understand. @@ -2106,11 +2127,11 @@ mxI = i; } } /* There was once an "if" here. The extra "{" is to preserve indentation. */ { - if( mxReadMark < pWal->hdr.mxFrame || mxI==0 ){ + if( pWal->readOnlyShm==0 && (mxReadMark < pWal->hdr.mxFrame || mxI==0) ){ for(i=1; iaReadMark[i] = pWal->hdr.mxFrame; mxI = i; @@ -2121,11 +2142,12 @@ } } } if( mxI==0 ){ assert( rc==SQLITE_BUSY ); - return WAL_RETRY; + assert( rc==SQLITE_BUSY || (pWal->readOnlyShm && rc==SQLITE_OK) ); + return rc==SQLITE_BUSY ? WAL_RETRY : SQLITE_READONLY_CANTLOCK; } rc = walLockShared(pWal, WAL_READ_LOCK(mxI)); if( rc ){ return rc==SQLITE_BUSY ? WAL_RETRY : rc; @@ -2357,10 +2379,11 @@ assert( pWal->readLock>=0 ); if( pWal->readOnly ){ return SQLITE_READONLY; } + assert( pWal->readOnlyShm==0 ); /* Only one writer allowed at a time. Get the write lock. Return ** SQLITE_BUSY if unable. */ rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1); @@ -2746,10 +2769,14 @@ assert( pWal->ckptLock==0 ); assert( pWal->writeLock==0 ); WALTRACE(("WAL%p: checkpoint begins\n", pWal)); + if( pWal->readOnlyShm ){ + return SQLITE_READONLY; + } + rc = walLockExclusive(pWal, WAL_CKPT_LOCK, 1); if( rc ){ /* Usually this is SQLITE_BUSY meaning that another thread or process ** is already running a checkpoint, or maybe a recovery. But it might ** also be SQLITE_IOERR. */ Index: test/lock_common.tcl ================================================================== --- test/lock_common.tcl +++ test/lock_common.tcl @@ -53,12 +53,12 @@ proc csql3 {sql} { list [catch { sql3 $sql } msg] $msg } uplevel set $varname $tn uplevel $script - code2 { db2 close } - code3 { db3 close } + catch { code2 { db2 close } } + catch { code3 { db3 close } } catch { close $::code2_chan } catch { close $::code3_chan } catch { db close } } } ADDED test/walro.test Index: test/walro.test ================================================================== --- test/walro.test +++ test/walro.test @@ -0,0 +1,121 @@ +# 2011 May 09 +# +# 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 tests for using WAL databases in read-only mode. +# + +set testdir [file dirname $argv0] +source $testdir/tester.tcl +source $testdir/lock_common.tcl +set ::testprefix walro + + +do_multiclient_test tn { + # These tests are only going to work on unix. + # + if {$tcl_platform(platform) != "unix"} continue + + # Do not run tests with the connections in the same process. + # + if {$tn==2} continue + + # Close all connections and delete the database. + # + code1 { db close } + code2 { db2 close } + code3 { db3 close } + forcedelete test.db + forcedelete walro + + file mkdir walro + + do_test 1.1.1 { + code2 { sqlite3 db2 test.db } + sql2 { + PRAGMA journal_mode = WAL; + CREATE TABLE t1(x, y); + INSERT INTO t1 VALUES('a', 'b'); + } + file exists test.db-shm + } {1} + + do_test 1.1.2 { + file attributes test.db-shm -permissions r--r--r-- + code1 { sqlite3 db test.db } + } {} + + do_test 1.1.3 { sql1 "SELECT * FROM t1" } {a b} + do_test 1.1.4 { sql2 "INSERT INTO t1 VALUES('c', 'd')" } {} + do_test 1.1.5 { sql1 "SELECT * FROM t1" } {a b c d} + + # Check that the read-only connection cannot write or checkpoint the db. + # + do_test 1.1.6 { + csql1 "INSERT INTO t1 VALUES('e', 'f')" + } {1 {attempt to write a readonly database}} + do_test 1.1.7 { + csql1 "PRAGMA wal_checkpoint" + } {1 {attempt to write a readonly database}} + + do_test 1.1.9 { sql2 "INSERT INTO t1 VALUES('e', 'f')" } {} + do_test 1.1.10 { sql1 "SELECT * FROM t1" } {a b c d e f} + + do_test 1.1.11 { + sql2 { + INSERT INTO t1 VALUES('g', 'h'); + PRAGMA wal_checkpoint; + } + set {} {} + } {} + do_test 1.1.12 { sql1 "SELECT * FROM t1" } {a b c d e f g h} + do_test 1.1.13 { sql2 "INSERT INTO t1 VALUES('i', 'j')" } {} + + do_test 1.2.1 { + code2 { db2 close } + code1 { db close } + list [file exists test.db-wal] [file exists test.db-shm] + } {1 1} + do_test 1.2.2 { + code1 { sqlite3 db test.db } + sql1 { SELECT * FROM t1 } + } {a b c d e f g h i j} + + do_test 1.2.3 { + code1 { db close } + file attributes test.db-shm -permissions rw-r--r-- + hexio_write test.db-shm 0 01020304 + file attributes test.db-shm -permissions r--r--r-- + code1 { sqlite3 db test.db } + csql1 { SELECT * FROM t1 } + } {1 {attempt to write a readonly database}} + do_test 1.2.4 { + code1 { sqlite3_extended_errcode db } + } {SQLITE_READONLY_RECOVERY} + + do_test 1.2.5 { + file attributes test.db-shm -permissions rw-r--r-- + code2 { sqlite3 db2 test.db } + sql2 "SELECT * FROM t1" + } {a b c d e f g h i j} + file attributes test.db-shm -permissions r--r--r-- + do_test 1.2.6 { sql1 "SELECT * FROM t1" } {a b c d e f g h i j} + + do_test 1.2.7 { + sql2 { + PRAGMA wal_checkpoint; + INSERT INTO t1 VALUES('k', 'l'); + } + set {} {} + } {} + do_test 1.2.8 { sql1 "SELECT * FROM t1" } {a b c d e f g h i j k l} +} + +finish_test