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Simplify the wal-readonly branch so that it does not require changes to

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anything other than os_unix.c and wal.c and a couple of new error codes.

FossilOrigin-Name: d6b4709de4d1f8af001f58938247f00a652a616e
This commit is contained in:
drh
2011-06-01 20:01:49 +00:00
parent f167694f9a
commit 66dfec8b7a
12 changed files with 74 additions and 169 deletions
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69
src/os_unix.c
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@@ -212,7 +212,6 @@ struct unixFile {
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() */
@@ -3453,10 +3452,6 @@ static int unixFileControl(sqlite3_file *id, int op, void *pArg){
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
@@ -3542,11 +3537,11 @@ struct unixShmNode {
char *zFilename; /* Name of the mmapped file */
int h; /* Open file descriptor */
int szRegion; /* Size of shared-memory regions */
int nRegion; /* Size of array apRegion */
u16 nRegion; /* Size of array apRegion */
u8 isReadonly; /* True if read-only */
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 */
@@ -3787,48 +3782,38 @@ static int unixOpenSharedMemory(unixFile *pDbFd){
}
if( pInode->bProcessLock==0 ){
int flags = (pDbFd->readOnlyShm ? O_RDONLY : O_RDWR|O_CREAT);
pShmNode->h = robust_open(zShmFilename, flags, (sStat.st_mode & 0777));
pShmNode->h = robust_open(zShmFilename, O_RDWR|O_CREAT,
(sStat.st_mode & 0777));
if( pShmNode->h<0 ){
rc = unixLogError(SQLITE_CANTOPEN_BKPT, "open", zShmFilename);
goto shm_open_err;
const char *zRO;
zRO = sqlite3_uri_parameter(pDbFd->zPath, "readonly_shm");
if( zRO && (zRO[0]!='0' || zRO[1]!=0) ){
pShmNode->h = robust_open(zShmFilename, O_RDONLY,
(sStat.st_mode & 0777));
pShmNode->isReadonly = 1;
}
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, 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 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( 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
@@ -3949,7 +3934,8 @@ static int unixShmMap(
while(pShmNode->nRegion<=iRegion){
void *pMem;
if( pShmNode->h>=0 ){
pMem = mmap(0, szRegion, PROT_READ|(!pShmNode->readOnly?PROT_WRITE:0),
pMem = mmap(0, szRegion,
pShmNode->isReadonly ? PROT_READ : PROT_READ|PROT_WRITE,
MAP_SHARED, pShmNode->h, pShmNode->nRegion*szRegion
);
if( pMem==MAP_FAILED ){
@@ -3975,6 +3961,7 @@ shmpage_out:
}else{
*pp = 0;
}
if( pShmNode->isReadonly && rc==SQLITE_OK ) rc = SQLITE_READONLY;
sqlite3_mutex_leave(pShmNode->mutex);
return rc;
}