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When a database file is opened, try to find an unused file descriptor to reuse. This change affects unix (and other systems that use os_unix.c) only. Fix for cvstrac ticket [http://www.sqlite.org/cvstrac/tktview?tn=4018|#4018].

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FossilOrigin-Name: 9b4d9ab62d687289837b13b07885e72cc3abe8a9
This commit is contained in:
dan
2009-08-21 17:18:03 +00:00
parent d00151613a
commit 08da86a68e
4 changed files with 287 additions and 132 deletions
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303
src/os_unix.c
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@@ -181,6 +181,7 @@ struct unixFile {
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 */
int flags; /* Flags value returned by xOpen() */
#if SQLITE_ENABLE_LOCKING_STYLE
int openFlags; /* The flags specified at open() */
#endif
@@ -202,11 +203,6 @@ struct unixFile {
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 */
/* If true, that means we are dealing with a database file that has
** a range of locking bytes from PENDING_BYTE through PENDING_BYTE+511
** which should never be read or written. Asserts() will verify this */
unsigned char isLockable; /* True if file might be locked */
#endif
#ifdef SQLITE_TEST
/* In test mode, increase the size of this structure a bit so that
@@ -753,7 +749,10 @@ struct unixOpenCnt {
int nRef; /* Number of pointers to this structure */
int nLock; /* Number of outstanding locks */
int nPending; /* Number of pending close() operations */
int *aPending; /* Malloced space holding fds awaiting close() */
struct PendingClose {
int fd; /* File descriptor to close */
int flags; /* Flags this file descriptor was opened with */
} *aPending; /* Malloced space holding fds awaiting close() */
#if OS_VXWORKS
sem_t *pSem; /* Named POSIX semaphore */
char aSemName[MAX_PATHNAME+1]; /* Name of that semaphore */
@@ -1405,6 +1404,60 @@ end_lock:
return rc;
}
/*
** Close all file descriptors accumuated in the p->aPending[] array. If
** all such file descriptors are closed without error, the aPending[]
** array is deleted and SQLITE_OK returned.
**
** Otherwise, if an error occurs, then successfully closed file descriptor
** entries in the aPending[] array are set to -1, the aPending[] array
** not deleted and SQLITE_IOERR_CLOSE returned.
*/
static int closePendingFds(unixFile *pFile){
struct unixOpenCnt *pOpen = pFile->pOpen;
struct PendingClose *aPending = pOpen->aPending;
int i;
int rc = SQLITE_OK;
assert( unixMutexHeld() );
for(i=0; i<pOpen->nPending; i++){
if( aPending[i].fd>=0 ){
if( close(aPending[i].fd) ){
pFile->lastErrno = errno;
rc = SQLITE_IOERR_CLOSE;
}else{
aPending[i].fd = -1;
}
}
}
if( rc==SQLITE_OK ){
sqlite3_free(aPending);
pOpen->nPending = 0;
pOpen->aPending = 0;
}
return rc;
}
/*
** Add the file descriptor used by file handle pFile to the corresponding
** aPending[] array to be closed after some other connection releases
** a lock.
*/
static void setPendingFd(unixFile *pFile){
struct PendingClose *aNew;
struct unixOpenCnt *pOpen = pFile->pOpen;
int nByte = (pOpen->nPending+1)*sizeof(pOpen->aPending[0]);
aNew = sqlite3_realloc(pOpen->aPending, nByte);
if( aNew==0 ){
/* If a malloc fails, just leak the file descriptor */
}else{
pOpen->aPending = aNew;
pOpen->aPending[pOpen->nPending].fd = pFile->h;
pOpen->aPending[pOpen->nPending].flags = pFile->flags;
pOpen->nPending++;
pFile->h = -1;
}
}
/*
** Lower the locking level on file descriptor pFile to locktype. locktype
** must be either NO_LOCK or SHARED_LOCK.
@@ -1487,7 +1540,6 @@ static int unixUnlock(sqlite3_file *id, int locktype){
}
if( locktype==NO_LOCK ){
struct unixOpenCnt *pOpen;
int rc2 = SQLITE_OK;
/* Decrement the shared lock counter. Release the lock using an
** OS call only when all threads in this same process have released
@@ -1522,27 +1574,10 @@ static int unixUnlock(sqlite3_file *id, int locktype){
pOpen->nLock--;
assert( pOpen->nLock>=0 );
if( pOpen->nLock==0 && pOpen->nPending>0 ){
int i;
for(i=0; i<pOpen->nPending; i++){
/* close pending fds, but if closing fails don't free the array
** assign -1 to the successfully closed descriptors and record the
** error. The next attempt to unlock will try again. */
if( pOpen->aPending[i] < 0 ) continue;
if( close(pOpen->aPending[i]) ){
pFile->lastErrno = errno;
rc2 = SQLITE_IOERR_CLOSE;
}else{
pOpen->aPending[i] = -1;
}
int rc2 = closePendingFds(pFile);
if( rc==SQLITE_OK ){
rc = rc2;
}
if( rc2==SQLITE_OK ){
sqlite3_free(pOpen->aPending);
pOpen->nPending = 0;
pOpen->aPending = 0;
}
}
if( rc==SQLITE_OK ){
rc = rc2;
}
}
@@ -1612,17 +1647,7 @@ static int unixClose(sqlite3_file *id){
** descriptor to pOpen->aPending. It will be automatically closed when
** the last lock is cleared.
*/
int *aNew;
struct unixOpenCnt *pOpen = pFile->pOpen;
aNew = sqlite3_realloc(pOpen->aPending, (pOpen->nPending+1)*sizeof(int) );
if( aNew==0 ){
/* If a malloc fails, just leak the file descriptor */
}else{
pOpen->aPending = aNew;
pOpen->aPending[pOpen->nPending] = pFile->h;
pOpen->nPending++;
pFile->h = -1;
}
setPendingFd(pFile);
}
releaseLockInfo(pFile->pLock);
releaseOpenCnt(pFile->pOpen);
@@ -2592,26 +2617,14 @@ static int afpUnlock(sqlite3_file *id, int locktype) {
pOpen->nLock--;
assert( pOpen->nLock>=0 );
if( pOpen->nLock==0 && pOpen->nPending>0 ){
int i;
for(i=0; i<pOpen->nPending; i++){
if( pOpen->aPending[i] < 0 ) continue;
if( close(pOpen->aPending[i]) ){
pFile->lastErrno = errno;
rc = SQLITE_IOERR_CLOSE;
}else{
pOpen->aPending[i] = -1;
}
}
if( rc==SQLITE_OK ){
sqlite3_free(pOpen->aPending);
pOpen->nPending = 0;
pOpen->aPending = 0;
}
rc = closePendingFds(pFile);
}
}
}
unixLeaveMutex();
if( rc==SQLITE_OK ) pFile->locktype = locktype;
if( rc==SQLITE_OK ){
pFile->locktype = locktype;
}
return rc;
}
@@ -2629,17 +2642,7 @@ static int afpClose(sqlite3_file *id) {
** descriptor to pOpen->aPending. It will be automatically closed when
** the last lock is cleared.
*/
int *aNew;
struct unixOpenCnt *pOpen = pFile->pOpen;
aNew = sqlite3_realloc(pOpen->aPending, (pOpen->nPending+1)*sizeof(int) );
if( aNew==0 ){
/* If a malloc fails, just leak the file descriptor */
}else{
pOpen->aPending = aNew;
pOpen->aPending[pOpen->nPending] = pFile->h;
pOpen->nPending++;
pFile->h = -1;
}
setPendingFd(pFile);
}
releaseOpenCnt(pFile->pOpen);
sqlite3_free(pFile->lockingContext);
@@ -2725,22 +2728,25 @@ static int unixRead(
int amt,
sqlite3_int64 offset
){
unixFile *pFile = (unixFile *)id;
int got;
assert( id );
/* Never read or write any of the bytes in the locking range */
assert( ((unixFile*)id)->isLockable==0
|| offset>=PENDING_BYTE+512
|| offset+amt<=PENDING_BYTE );
/* 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->flags&SQLITE_OPEN_MAIN_DB)==0
|| offset>=PENDING_BYTE+512
|| offset+amt<=PENDING_BYTE
);
got = seekAndRead((unixFile*)id, offset, pBuf, amt);
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{
((unixFile*)id)->lastErrno = 0; /* not a system error */
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;
@@ -2794,14 +2800,17 @@ static int unixWrite(
int amt,
sqlite3_int64 offset
){
unixFile *pFile = (unixFile*)id;
int wrote = 0;
assert( id );
assert( amt>0 );
/* Never read or write any of the bytes in the locking range */
assert( ((unixFile*)id)->isLockable==0
|| offset>=PENDING_BYTE+512
|| offset+amt<=PENDING_BYTE );
/* 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->flags&SQLITE_OPEN_MAIN_DB)==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
@@ -2810,8 +2819,7 @@ static int unixWrite(
** has changed. If the transaction counter is modified, record that
** fact too.
*/
if( ((unixFile*)id)->inNormalWrite ){
unixFile *pFile = (unixFile*)id;
if( pFile->inNormalWrite ){
pFile->dbUpdate = 1; /* The database has been modified */
if( offset<=24 && offset+amt>=27 ){
int rc;
@@ -2826,7 +2834,7 @@ static int unixWrite(
}
#endif
while( amt>0 && (wrote = seekAndWrite((unixFile*)id, offset, pBuf, amt))>0 ){
while( amt>0 && (wrote = seekAndWrite(pFile, offset, pBuf, amt))>0 ){
amt -= wrote;
offset += wrote;
pBuf = &((char*)pBuf)[wrote];
@@ -2838,7 +2846,7 @@ static int unixWrite(
/* lastErrno set by seekAndWrite */
return SQLITE_IOERR_WRITE;
}else{
((unixFile*)id)->lastErrno = 0; /* not a system error */
pFile->lastErrno = 0; /* not a system error */
return SQLITE_FULL;
}
}
@@ -3650,6 +3658,58 @@ static int getTempname(int nBuf, char *zBuf){
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 int findReusableFd(const char *zPath, int flags){
int fd = -1; /* Return value */
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 *p;
struct unixFileId id;
id.dev = sStat.st_dev;
id.ino = sStat.st_ino;
unixEnterMutex();
for(p=openList; p&& memcmp(&id, &p->fileId, sizeof(id)); p=p->pNext);
if( p && p->aPending ){
int i;
struct PendingClose *aPending = p->aPending;
for(i=0; i<p->nPending; i++){
if( aPending[i].fd>=0 && flags==aPending[i].flags ){
fd = aPending[i].fd;
aPending[i].fd = -1;
break;
}
}
}
unixLeaveMutex();
}
return fd;
}
/*
** Open the file zPath.
@@ -3680,12 +3740,13 @@ static int unixOpen(
int flags, /* Input flags to control the opening */
int *pOutFlags /* Output flags returned to SQLite core */
){
int fd = -1; /* File descriptor returned by open() */
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;
int rc = SQLITE_OK; /* Function Return Code */
int isExclusive = (flags & SQLITE_OPEN_EXCLUSIVE);
int isDelete = (flags & SQLITE_OPEN_DELETEONCLOSE);
@@ -3720,11 +3781,10 @@ static int unixOpen(
assert(isDelete==0 || isCreate);
/* The main DB, main journal, and master journal are never automatically
** deleted
*/
assert( eType!=SQLITE_OPEN_MAIN_DB || !isDelete );
assert( eType!=SQLITE_OPEN_MAIN_JOURNAL || !isDelete );
assert( eType!=SQLITE_OPEN_MASTER_JOURNAL || !isDelete );
** 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
@@ -3733,9 +3793,19 @@ static int unixOpen(
|| eType==SQLITE_OPEN_TRANSIENT_DB
);
memset(pFile, 0, sizeof(unixFile));
memset(p, 0, sizeof(unixFile));
if( !zName ){
if( eType==SQLITE_OPEN_MAIN_DB ){
/* Try to find an unused file descriptor to reuse. This is not done
** for 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 for
** the sake of such an obscure feature. */
#if !OS_VXWORKS
fd = findReusableFd(zName, flags);
#endif
}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 ){
@@ -3744,23 +3814,35 @@ static int unixOpen(
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);
fd = open(zName, openFlags, isDelete?0600:SQLITE_DEFAULT_FILE_PERMISSIONS);
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);
flags |= SQLITE_OPEN_READONLY;
return unixOpen(pVfs, zPath, pFile, flags, pOutFlags);
}
if( fd<0 ){
return SQLITE_CANTOPEN;
fd = open(zName, openFlags, isDelete?0600:SQLITE_DEFAULT_FILE_PERMISSIONS);
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);
flags |= SQLITE_OPEN_READONLY;
return unixOpen(pVfs, zPath, pFile, flags, pOutFlags);
}
if( fd<0 ){
return SQLITE_CANTOPEN;
}
}
assert( fd>=0 );
p->flags = flags;
if( pOutFlags ){
*pOutFlags = flags;
}
if( isDelete ){
#if OS_VXWORKS
zPath = zName;
@@ -3770,24 +3852,19 @@ static int unixOpen(
}
#if SQLITE_ENABLE_LOCKING_STYLE
else{
((unixFile*)pFile)->openFlags = openFlags;
}
#endif
if( pOutFlags ){
*pOutFlags = flags;
}
#ifndef NDEBUG
if( (flags & SQLITE_OPEN_MAIN_DB)!=0 ){
((unixFile*)pFile)->isLockable = 1;
p->openFlags = openFlags;
}
#endif
assert( fd>=0 );
if( isOpenDirectory ){
rc = openDirectory(zPath, &dirfd);
if( rc!=SQLITE_OK ){
close(fd); /* silently leak if fail, already in error */
/* 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 cause any locks held
** on the file by this process to be released. */
assert( eType!=SQLITE_OPEN_MAIN_DB );
close(fd); /* silently leak if fail, already in error */
return rc;
}
}
@@ -3803,16 +3880,14 @@ static int unixOpen(
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
*/
/* 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 ){
((unixFile*)pFile)->lastErrno = errno;
((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;