diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/os_unix.c | 51 |
1 files changed, 34 insertions, 17 deletions
diff --git a/src/os_unix.c b/src/os_unix.c index c79e1b48e..0413c5dfa 100644 --- a/src/os_unix.c +++ b/src/os_unix.c @@ -3282,13 +3282,22 @@ static void unixShmPurge(unixFile *pFd){ ** as the open database file and has the same name as the open database ** file with the "-shm" suffix added. For example, if the database file ** is "/home/user1/config.db" then the file that is created and mmapped -** for shared memory will be called "/home/user1/config.db-shm". We -** experimented with using files in /dev/tmp or an some other tmpfs mount. -** But if a file in a different directory from the database file is used, -** then differing access permissions or a chroot() might cause two different -** processes on the same database to end up using different files for -** shared memory - meaning that their memory would not really be shared - -** resulting in database corruption. +** for shared memory will be called "/home/user1/config.db-shm". +** +** Another approach to is to use files in /dev/shm or /dev/tmp or an +** some other tmpfs mount. But if a file in a different directory +** from the database file is used, then differing access permissions +** or a chroot() might cause two different processes on the same +** database to end up using different files for shared memory - +** meaning that their memory would not really be shared - resulting +** in database corruption. Nevertheless, this tmpfs file usage +** can be enabled at compile-time using -DSQLITE_SHM_DIRECTORY="/dev/shm" +** or the equivalent. The use of the SQLITE_SHM_DIRECTORY compile-time +** option results in an incompatible build of SQLite; builds of SQLite +** that with differing SQLITE_SHM_DIRECTORY settings attempt to use the +** same database file at the same time, database corruption will likely +** result. The SQLITE_SHM_DIRECTORY compile-time option is considered +** "unsupported" and may go away in a future SQLite release. ** ** When opening a new shared-memory file, if no other instances of that ** file are currently open, in this process or in other processes, then @@ -3327,7 +3336,11 @@ static int unixOpenSharedMemory(unixFile *pDbFd){ goto shm_open_err; } +#ifdef SQLITE_SHM_DIRECTORY + nShmFilename = sizeof(SQLITE_SHM_DIRECTORY) + 30; +#else nShmFilename = 5 + (int)strlen(pDbFd->zPath); +#endif pShmNode = sqlite3_malloc( sizeof(*pShmNode) + nShmFilename ); if( pShmNode==0 ){ rc = SQLITE_NOMEM; @@ -3335,7 +3348,13 @@ static int unixOpenSharedMemory(unixFile *pDbFd){ } memset(pShmNode, 0, sizeof(*pShmNode)); zShmFilename = pShmNode->zFilename = (char*)&pShmNode[1]; +#ifdef SQLITE_SHM_DIRECTORY + sqlite3_snprintf(nShmFilename, zShmFilename, + SQLITE_SHM_DIRECTORY "/sqlite-shm-%x-%x", + (u32)sStat.st_ino, (u32)sStat.st_dev); +#else sqlite3_snprintf(nShmFilename, zShmFilename, "%s-shm", pDbFd->zPath); +#endif pShmNode->h = -1; pDbFd->pInode->pShmNode = pShmNode; pShmNode->pInode = pDbFd->pInode; @@ -4311,14 +4330,13 @@ static UnixUnusedFd *findReusableFd(const char *zPath, int flags){ ** ** If the file being opened is a temporary file, it is always created with ** the octal permissions 0600 (read/writable by owner only). If the file -** is a database or master journal file, it is created with the permissions -** mask SQLITE_DEFAULT_FILE_PERMISSIONS. +** is a database, journal or master journal file, it is created with the +** permissions mask SQLITE_DEFAULT_FILE_PERMISSIONS. ** -** Finally, if the file being opened is a WAL or regular journal file, then -** this function queries the file-system for the permissions on the -** corresponding database file and sets *pMode to this value. Whenever -** possible, WAL and journal files are created using the same permissions -** as the associated database file. +** Finally, if the file being opened is a WAL file, then this function +** queries the file-system for the permissions on the corresponding database +** file and sets *pMode to this value. Whenever possible, WAL files are +** created using the same permissions as the associated database file. */ static int findCreateFileMode( const char *zPath, /* Path of file (possibly) being created */ @@ -4326,12 +4344,12 @@ static int findCreateFileMode( mode_t *pMode /* OUT: Permissions to open file with */ ){ int rc = SQLITE_OK; /* Return Code */ - if( flags & (SQLITE_OPEN_WAL|SQLITE_OPEN_MAIN_JOURNAL) ){ + if( flags & SQLITE_OPEN_WAL ){ char zDb[MAX_PATHNAME+1]; /* Database file path */ int nDb; /* Number of valid bytes in zDb */ struct stat sStat; /* Output of stat() on database file */ - nDb = sqlite3Strlen30(zPath) - ((flags & SQLITE_OPEN_WAL) ? 4 : 8); + nDb = sqlite3Strlen30(zPath) - 4; memcpy(zDb, zPath, nDb); zDb[nDb] = '\0'; if( 0==stat(zDb, &sStat) ){ @@ -4474,7 +4492,6 @@ static int unixOpen( rc = findCreateFileMode(zName, flags, &openMode); if( rc!=SQLITE_OK ){ assert( !p->pUnused ); - assert( eType==SQLITE_OPEN_WAL || eType==SQLITE_OPEN_MAIN_JOURNAL ); return rc; } fd = open(zName, openFlags, openMode); |