Add the new optional "unix-excl" VFS. This VFS grabs an exclusive lock on

the database preventing other processes from accessing it, but continues to
allow other database connections from the same process.

FossilOrigin-Name: 00051c3296e11211b2bb5ae28f016b17dca857d7

manifest

@@ -1,5 +1,8 @@
-C More\stests\sfor\sSQLITE_OMIT_UNIQUE_ENFORCEMENT\sand\sminor\schange\sto\simplementation.
+-----BEGIN PGP SIGNED MESSAGE-----
-D 2011-03-12T04:58:55.547
+Hash: SHA1
+
+C Add\sthe\snew\soptional\s"unix-excl"\sVFS.\s\sThis\sVFS\sgrabs\san\sexclusive\slock\son\nthe\sdatabase\spreventing\sother\sprocesses\sfrom\saccessing\sit,\sbut\scontinues\sto\nallow\sother\sdatabase\sconnections\sfrom\sthe\ssame\sprocess.
+D 2011-03-12T17:02:57.101
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 27701a1653595a1f2187dc61c8117e00a6c1d50f
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -162,7 +165,7 @@ F src/os.c 22ac61d06e72a0dac900400147333b07b13d8e1d
 F src/os.h 9dbed8c2b9c1f2f2ebabc09e49829d4777c26bf9
 F src/os_common.h a8f95b81eca8a1ab8593d23e94f8a35f35d4078f
 F src/os_os2.c 2596fd2d5d0976c6c0c628d0c3c7c4e7a724f4cf
-F src/os_unix.c c4d50608133e16185dd2e120d2713c096f390260
+F src/os_unix.c 557837beff775c448bb072ae21edeff912d1f0df
 F src/os_win.c 24d72407a90551969744cf9bcbb1b4c72c5fa845
 F src/pager.c 6aa906b60a59664ba58d3f746164bb010d407ce1
 F src/pager.h 3f8c783de1d4706b40b1ac15b64f5f896bcc78d1
@@ -177,7 +180,7 @@ F src/random.c cd4a67b3953b88019f8cd4ccd81394a8ddfaba50
 F src/resolve.c 1c0f32b64f8e3f555fe1f732f9d6f501a7f05706
 F src/rowset.c 69afa95a97c524ba6faf3805e717b5b7ae85a697
 F src/select.c d24406c45dd2442eb2eeaac413439066b149c944
-F src/shell.c 649c51979812f77f97507024a4cea480c6862b8b
+F src/shell.c 54f8fe0afab6839444882c4d18a0032668392c9a
 F src/sqlite.h.in 369c767e6b9f101d63d8e4c5e40279f975ccec08
 F src/sqlite3ext.h c90bd5507099f62043832d73f6425d8d5c5da754
 F src/sqliteInt.h 2cea3e47997e3f4d9b4f1ce62f99c35be1b5a586
@@ -913,7 +916,18 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
 F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f
-P f957f23a8a392bb1720720960bda2c7b24de9663
+P b86999436ec2414c990ba720441fe316f647eef6
-R 9809ca6e3f2473669b6771844893033b
+R b4018b4a3ca8304164ff6618b813c5a9
-U shaneh
+T *bgcolor * #aaa8d3
-Z 165de3d9f760ec4796ef397e07022985
+T *branch * unix-excl
+T *sym-unix-excl *
+T -sym-trunk *
+U drh
+Z ca346ade739e93ef182345e803581a80
+-----BEGIN PGP SIGNATURE-----
+Version: GnuPG v1.4.6 (GNU/Linux)
+
+iD8DBQFNe6dEoxKgR168RlERAkgMAJ47rTo3YzDvLp8S+pIflXBmm5FOSwCggCkn
+s82X2XcH9cqBqUU6lQenClw=
+=LUbU
+-----END PGP SIGNATURE-----

manifest.uuid

@@ -1 +1 @@
-b86999436ec2414c990ba720441fe316f647eef6
+00051c3296e11211b2bb5ae28f016b17dca857d7

src/os_unix.c

@@ -206,6 +206,7 @@ struct unixFile {
   int h;                              /* The file descriptor */
   int dirfd;                          /* File descriptor for the directory */
   unsigned char eFileLock;            /* The type of lock held on this fd */
+  unsigned char ctrlFlags;            /* Behavioral bits.  UNIXFILE_* flags */
   int lastErrno;                      /* The unix errno from last I/O error */
   void *lockingContext;               /* Locking style specific state */
   UnixUnusedFd *pUnused;              /* Pre-allocated UnixUnusedFd */
@@ -242,6 +243,11 @@ struct unixFile {
 #endif
 };
 
+/*
+** Allowed values for the unixFile.ctrlFlags bitmask:
+*/
+#define UNIXFILE_EXCL   0x01     /* Connections from one process only */
+
 /*
 ** Include code that is common to all os_*.c files
 */
@@ -887,7 +893,8 @@ struct unixFileId {
 struct unixInodeInfo {
   struct unixFileId fileId;       /* The lookup key */
   int nShared;                    /* Number of SHARED locks held */
-  int eFileLock;                  /* One of SHARED_LOCK, RESERVED_LOCK etc. */
+  unsigned char eFileLock;        /* One of SHARED_LOCK, RESERVED_LOCK etc. */
+  unsigned char bProcessLock;     /* An exclusive process lock is held */
   int nRef;                       /* Number of pointers to this structure */
   unixShmNode *pShmNode;          /* Shared memory associated with this inode */
   int nLock;                      /* Number of outstanding file locks */
@@ -1158,7 +1165,7 @@ static int unixCheckReservedLock(sqlite3_file *id, int *pResOut){
   /* Otherwise see if some other process holds it.
   */
 #ifndef __DJGPP__
-  if( !reserved ){
+  if( !reserved && !pFile->pInode->bProcessLock ){
     struct flock lock;
     lock.l_whence = SEEK_SET;
     lock.l_start = RESERVED_BYTE;
@@ -1181,6 +1188,40 @@ static int unixCheckReservedLock(sqlite3_file *id, int *pResOut){
   return rc;
 }
 
+/*
+** Attempt to set a system-lock on the file pFile.  The lock is 
+** described by pLock.
+**
+** If the pFile was opened from unix-excl, then the only lock ever
+** obtained is an exclusive lock, and it is obtained exactly once
+** the first time any lock is attempted.  All subsequent system locking
+** operations become no-ops.  Locking operations still happen internally,
+** in order to coordinate access between separate database connections
+** within this process, but all of that is handled in memory and the
+** operating system does not participate.
+*/
+static int unixFileLock(unixFile *pFile, struct flock *pLock){
+  int rc;
+  assert( unixMutexHeld() );
+  if( (pFile->ctrlFlags & UNIXFILE_EXCL)!=0 || pFile->pInode->bProcessLock ){
+    if( pFile->pInode->bProcessLock==0 ){
+      struct flock lock;
+      lock.l_whence = SEEK_SET;
+      lock.l_start = SHARED_FIRST;
+      lock.l_len = SHARED_SIZE;
+      lock.l_type = F_WRLCK;
+      rc = osFcntl(pFile->h, F_SETLK, &lock);
+      if( rc<0 ) return rc;
+      pFile->pInode->bProcessLock = 1;
+    }else{
+      rc = 0;
+    }
+  }else{
+    rc = osFcntl(pFile->h, F_SETLK, pLock);
+  }
+  return rc;
+}
+
 /*
 ** Lock the file with the lock specified by parameter eFileLock - one
 ** of the following:
@@ -1317,7 +1358,7 @@ static int unixLock(sqlite3_file *id, int eFileLock){
   ){
     lock.l_type = (eFileLock==SHARED_LOCK?F_RDLCK:F_WRLCK);
     lock.l_start = PENDING_BYTE;
-    s = osFcntl(pFile->h, F_SETLK, &lock);
+    s = unixFileLock(pFile, &lock);
     if( s==(-1) ){
       tErrno = errno;
       rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
@@ -1339,14 +1380,14 @@ static int unixLock(sqlite3_file *id, int eFileLock){
     /* Now get the read-lock */
     lock.l_start = SHARED_FIRST;
     lock.l_len = SHARED_SIZE;
-    if( (s = osFcntl(pFile->h, F_SETLK, &lock))==(-1) ){
+    if( (s = unixFileLock(pFile, &lock))==(-1) ){
       tErrno = errno;
     }
     /* Drop the temporary PENDING lock */
     lock.l_start = PENDING_BYTE;
     lock.l_len = 1L;
     lock.l_type = F_UNLCK;
-    if( osFcntl(pFile->h, F_SETLK, &lock)!=0 ){
+    if( unixFileLock(pFile, &lock)!=0 ){
       if( s != -1 ){
         /* This could happen with a network mount */
         tErrno = errno; 
@@ -1389,7 +1430,7 @@ static int unixLock(sqlite3_file *id, int eFileLock){
       default:
         assert(0);
     }
-    s = osFcntl(pFile->h, F_SETLK, &lock);
+    s = unixFileLock(pFile, &lock);
     if( s==(-1) ){
       tErrno = errno;
       rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
@@ -1458,7 +1499,7 @@ static void setPendingFd(unixFile *pFile){
 ** 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 eFileLock, int handleNFSUnlock){
+static int posixUnlock(sqlite3_file *id, int eFileLock, int handleNFSUnlock){
   unixFile *pFile = (unixFile*)id;
   unixInodeInfo *pInode;
   struct flock lock;
@@ -1525,7 +1566,7 @@ static int _posixUnlock(sqlite3_file *id, int eFileLock, int handleNFSUnlock){
         lock.l_whence = SEEK_SET;
         lock.l_start = SHARED_FIRST;
         lock.l_len = divSize;
-        if( osFcntl(h, F_SETLK, &lock)==(-1) ){
+        if( unixFileLock(pFile,, &lock)==(-1) ){
           tErrno = errno;
           rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
           if( IS_LOCK_ERROR(rc) ){
@@ -1537,7 +1578,7 @@ static int _posixUnlock(sqlite3_file *id, int eFileLock, int handleNFSUnlock){
         lock.l_whence = SEEK_SET;
         lock.l_start = SHARED_FIRST;
         lock.l_len = divSize;
-        if( osFcntl(h, F_SETLK, &lock)==(-1) ){
+        if( unixFileLock(pFile, &lock)==(-1) ){
           tErrno = errno;
           rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_RDLOCK);
           if( IS_LOCK_ERROR(rc) ){
@@ -1549,7 +1590,7 @@ static int _posixUnlock(sqlite3_file *id, int eFileLock, int handleNFSUnlock){
         lock.l_whence = SEEK_SET;
         lock.l_start = SHARED_FIRST+divSize;
         lock.l_len = SHARED_SIZE-divSize;
-        if( osFcntl(h, F_SETLK, &lock)==(-1) ){
+        if( unixFileLock(pFile, &lock)==(-1) ){
           tErrno = errno;
           rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
           if( IS_LOCK_ERROR(rc) ){
@@ -1564,7 +1605,7 @@ static int _posixUnlock(sqlite3_file *id, int eFileLock, int handleNFSUnlock){
         lock.l_whence = SEEK_SET;
         lock.l_start = SHARED_FIRST;
         lock.l_len = SHARED_SIZE;
-        if( osFcntl(h, F_SETLK, &lock)==(-1) ){
+        if( unixFileLock(pFile, &lock)==(-1) ){
           tErrno = errno;
           rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_RDLOCK);
           if( IS_LOCK_ERROR(rc) ){
@@ -1578,7 +1619,7 @@ static int _posixUnlock(sqlite3_file *id, int eFileLock, int handleNFSUnlock){
     lock.l_whence = SEEK_SET;
     lock.l_start = PENDING_BYTE;
     lock.l_len = 2L;  assert( PENDING_BYTE+1==RESERVED_BYTE );
-    if( osFcntl(h, F_SETLK, &lock)!=(-1) ){
+    if( unixFileLock(pFile, &lock)!=(-1) ){
       pInode->eFileLock = SHARED_LOCK;
     }else{
       tErrno = errno;
@@ -1602,7 +1643,7 @@ static int _posixUnlock(sqlite3_file *id, int eFileLock, int handleNFSUnlock){
       SimulateIOErrorBenign(1);
       SimulateIOError( h=(-1) )
       SimulateIOErrorBenign(0);
-      if( osFcntl(h, F_SETLK, &lock)!=(-1) ){
+      if( unixFileLock(pFile, &lock)!=(-1) ){
         pInode->eFileLock = NO_LOCK;
       }else{
         tErrno = errno;
@@ -1640,7 +1681,7 @@ end_unlock:
 ** the requested locking level, this routine is a no-op.
 */
 static int unixUnlock(sqlite3_file *id, int eFileLock){
-  return _posixUnlock(id, eFileLock, 0);
+  return posixUnlock(id, eFileLock, 0);
 }
 
 /*
@@ -2821,7 +2862,7 @@ static int afpClose(sqlite3_file *id) {
  ** the requested locking level, this routine is a no-op.
  */
 static int nfsUnlock(sqlite3_file *id, int eFileLock){
-  return _posixUnlock(id, eFileLock, 1);
+  return posixUnlock(id, eFileLock, 1);
 }
 
 #endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
@@ -4351,6 +4392,11 @@ static int fillInUnixFile(
   pNew->h = h;
   pNew->dirfd = dirfd;
   pNew->zPath = zFilename;
+  if( memcmp(pVfs->zName,"unix-excl",10)==0 ){
+    pNew->ctrlFlags = UNIXFILE_EXCL;
+  }else{
+    pNew->ctrlFlags = 0;
+  }
 
 #if OS_VXWORKS
   pNew->pId = vxworksFindFileId(zFilename);
@@ -6550,6 +6596,7 @@ int sqlite3_os_init(void){
 #endif
     UNIXVFS("unix-none",     nolockIoFinder ),
     UNIXVFS("unix-dotfile",  dotlockIoFinder ),
+    UNIXVFS("unix-excl",     posixIoFinder ),
 #if OS_VXWORKS
     UNIXVFS("unix-namedsem", semIoFinder ),
 #endif

src/shell.c

@@ -419,6 +419,7 @@ struct callback_data {
                          ** .explain ON */
   char outfile[FILENAME_MAX]; /* Filename for *out */
   const char *zDbFilename;    /* name of the database file */
+  const char *zVfs;           /* Name of VFS to use */
   sqlite3_stmt *pStmt;   /* Current statement if any. */
   FILE *pLog;            /* Write log output here */
 };
@@ -2600,6 +2601,7 @@ static const char zOptions[] =
   "   -stats               print memory stats before each finalize\n"
   "   -nullvalue 'text'    set text string for NULL values\n"
   "   -version             show SQLite version\n"
+  "   -vfs NAME            use NAME as the default VFS\n"
 ;
 static void usage(int showDetail){
   fprintf(stderr,
@@ -2684,6 +2686,15 @@ int main(int argc, char **argv){
 #if defined(SQLITE_ENABLE_MEMSYS3) || defined(SQLITE_ENABLE_MEMSYS5)
       sqlite3_config(SQLITE_CONFIG_HEAP, malloc((int)szHeap), (int)szHeap, 64);
 #endif
+    }else if( strcmp(argv[i],"-vfs")==0 ){
+      i++;
+      sqlite3_vfs *pVfs = sqlite3_vfs_find(argv[i]);
+      if( pVfs ){
+        sqlite3_vfs_register(pVfs, 1);
+      }else{
+        fprintf(stderr, "no such VFS: \"%s\"\n", argv[i]);
+        exit(1);
+      }
     }
   }
   if( i<argc ){
@@ -2792,6 +2803,8 @@ int main(int argc, char **argv){
       stdin_is_interactive = 0;
     }else if( strcmp(z,"-heap")==0 ){
       i++;
+    }else if( strcmp(z,"-vfs")==0 ){
+      i++;
     }else if( strcmp(z,"-help")==0 || strcmp(z, "--help")==0 ){
       usage(1);
     }else{