database/sqlite
1
0
Fork 0
mirror of https://github.com/sqlite/sqlite.git synced 2025-11-12 13:01:09 +03:00
Code Activity

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

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

FossilOrigin-Name: 00051c3296e11211b2bb5ae28f016b17dca857d7
This commit is contained in:
drh
2011-03-12 17:02:57 +00:00
parent 11c58f7d8e
commit a7e61d8b24
4 changed files with 98 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files

77
src/os_unix.c
View File

@@ -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