diff options
Diffstat (limited to 'src/pager.c')
| -rw-r--r-- | src/pager.c | 711 |
1 files changed, 463 insertions, 248 deletions
diff --git a/src/pager.c b/src/pager.c index 41650d98f..9402b10d3 100644 --- a/src/pager.c +++ b/src/pager.c @@ -27,13 +27,15 @@ ** all writes in order to support rollback. Locking is used to limit ** access to one or more reader or on writer. ** -** @(#) $Id: pager.c,v 1.2 2001/04/14 16:38:23 drh Exp $ +** @(#) $Id: pager.c,v 1.3 2001/04/15 00:37:09 drh Exp $ */ +#include "sqliteInt.h" #include "pager.h" #include <fcntl.h> #include <sys/stat.h> #include <unistd.h> #include <assert.h> +#include <string.h> /* ** The page cache as a whole is always in one of the following @@ -66,15 +68,18 @@ #define SQLITE_READLOCK 1 #define SQLITE_WRITELOCK 2 + /* ** Each in-memory image of a page begins with the following header. */ +typedef struct PgHdr PgHdr; struct PgHdr { Pager *pPager; /* The pager to which this page belongs */ Pgno pgno; /* The page number for this page */ PgHdr *pNextHash, *pPrevHash; /* Hash collision chain for PgHdr.pgno */ int nRef; /* Number of users of this page */ - PgHdr *pNext, *pPrev; /* Freelist of pages where nRef==0 */ + PgHdr *pNextFree, *pPrevFree; /* Freelist of pages where nRef==0 */ + PgHdr *pNextAll, *pPrevAll; /* A list of all pages */ char inJournal; /* TRUE if has been written to journal */ char dirty; /* TRUE if we need to write back changes */ /* SQLITE_PAGE_SIZE bytes of page data follow this header */ @@ -88,15 +93,10 @@ struct PgHdr { #define DATA_TO_PGHDR(D) (&((PgHdr*)(D))[-1]) /* -** The number of page numbers that will fit on one page. -*/ -#define SQLITE_INDEX_SIZE (SQLITE_PAGE_SIZE/sizeof(Pgno)) - -/* ** How big to make the hash table used for locating in-memory pages ** by page number. */ -#define N_PG_HASH 353 +#define N_PG_HASH 101 /* ** A open page cache is an instance of the following structure. @@ -105,50 +105,152 @@ struct Pager { char *zFilename; /* Name of the database file */ char *zJournal; /* Name of the journal file */ int fd, jfd; /* File descriptors for database and journal */ - int nRef; /* Sum of PgHdr.nRef */ int dbSize; /* Number of pages in the file */ int origDbSize; /* dbSize before the current change */ - int jSize; /* Number of pages in the journal */ - int nIdx; /* Number of entries in aIdx[] */ int nPage; /* Total number of in-memory pages */ + int nRef; /* Number of in-memory pages with PgHdr.nRef>0 */ int mxPage; /* Maximum number of pages to hold in cache */ - char state; /* SQLITE_UNLOCK, _READLOCK or _WRITELOCK */ - char ioErr; /* True if an I/O error has occurred */ + int nHit, nMiss, nOvfl; /* Cache hits, missing, and LRU overflows */ + unsigned char state; /* SQLITE_UNLOCK, _READLOCK or _WRITELOCK */ + unsigned char errMask; /* One of several kinds of errors */ PgHdr *pFirst, *pLast; /* List of free pages */ + PgHdr *pAll; /* List of all pages */ PgHdr *aHash[N_PG_HASH]; /* Hash table to map page number of PgHdr */ - Pgno aIdx[SQLITE_INDEX_SIZE]; /* Current journal index page */ +}; + +/* +** These are bits that can be set in Pager.errMask. +*/ +#define PAGER_ERR_FULL 0x01 /* a write() failed */ +#define PAGER_ERR_MEM 0x02 /* malloc() failed */ +#define PAGER_ERR_LOCK 0x04 /* error in the locking protocol */ +#define PAGER_ERR_CORRUPT 0x08 /* database or journal corruption */ + +/* +** The journal file contains page records in the following +** format. +*/ +typedef struct PageRecord PageRecord; +struct PageRecord { + Pgno pgno; /* The page number */ + char aData[SQLITE_PAGE_SIZE]; /* Original data for page pgno */ +}; + +/* +** Journal files begin with the following magic string. This data +** is completely random. It is used only as a sanity check. +*/ +static const unsigned char aJournalMagic[] = { + 0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd4, }; /* ** Hash a page number */ -#define sqlite_pager_hash(PN) ((PN)%N_PG_HASH) +#define pager_hash(PN) ((PN)%N_PG_HASH) /* ** Attempt to acquire a read lock (if wrlock==0) or a write lock (if wrlock==1) ** on the database file. Return 0 on success and non-zero if the lock ** could not be acquired. */ -static int sqlite_pager_lock(int fd, int wrlock){ +static int pager_lock(int fd, int wrlock){ + int rc; struct flock lock; - lock.l_type = write_lock ? F_WRLCK : F_RDLCK; - return fcntl(fd, F_SETLK, &lock)!=0; + lock.l_type = wrlock ? F_WRLCK : F_RDLCK; + lock.l_whence = SEEK_SET; + lock.l_start = lock.l_len = 0L; + rc = fcntl(fd, F_SETLK, &lock); + return rc!=0; } /* ** Unlock the database file. */ -static int sqlite_pager_unlock(fd){ +static int pager_unlock(fd){ + int rc; struct flock lock; lock.l_type = F_UNLCK; - return fcntl(fd, F_SETLK, &lock)!=0; + lock.l_whence = SEEK_SET; + lock.l_start = lock.l_len = 0L; + rc = fcntl(fd, F_SETLK, &lock); + return rc!=0; +} + +/* +** Move the cursor for file descriptor fd to the point whereto from +** the beginning of the file. +*/ +static int pager_seek(int fd, off_t whereto){ + lseek(fd, whereto, SEEK_SET); + return SQLITE_OK; +} + +/* +** Truncate the given file so that it contains exactly mxPg pages +** of data. +*/ +static int pager_truncate(int fd, Pgno mxPg){ + int rc; + rc = ftruncate(fd, mxPg*SQLITE_PAGE_SIZE); + return rc!=0 ? SQLITE_IOERR : SQLITE_OK; +} + +/* +** Read nBytes of data from fd into pBuf. If the data cannot be +** read or only a partial read occurs, then the unread parts of +** pBuf are filled with zeros and this routine returns SQLITE_IOERR. +** If the read is completely successful, return SQLITE_OK. +*/ +static int pager_read(int fd, void *pBuf, int nByte){ + int rc; + rc = read(fd, pBuf, nByte); + if( rc<0 ){ + memset(pBuf, 0, nByte); + return SQLITE_IOERR; + } + if( rc<nByte ){ + memset(&((char*)pBuf)[rc], 0, nByte - rc); + rc = SQLITE_IOERR; + }else{ + rc = SQLITE_OK; + } + return rc; +} + +/* +** Write nBytes of data into fd. If any problem occurs or if the +** write is incomplete, SQLITE_IOERR is returned. SQLITE_OK is +** returned upon complete success. +*/ +static int pager_write(int fd, const void *pBuf, int nByte){ + int rc; + rc = write(fd, pBuf, nByte); + if( rc<nByte ){ + return SQLITE_FULL; + }else{ + return SQLITE_OK; + } +} + +/* +** Convert the bits in the pPager->errMask into an approprate +** return code. +*/ +static int pager_errcode(Pager *pPager){ + int rc = SQLITE_OK; + if( pPager->errMask & PAGER_ERR_LOCK ) rc = SQLITE_PROTOCOL; + if( pPager->errMask & PAGER_ERR_FULL ) rc = SQLITE_FULL; + if( pPager->errMask & PAGER_ERR_MEM ) rc = SQLITE_NOMEM; + if( pPager->errMask & PAGER_ERR_CORRUPT ) rc = SQLITE_CORRUPT; + return rc; } /* ** Find a page in the hash table given its page number. Return ** a pointer to the page or NULL if not found. */ -static PgHdr *sqlite_pager_lookup(Pager *pPager, Pgno pgno){ +static PgHdr *pager_lookup(Pager *pPager, Pgno pgno){ PgHdr *p = pPager->aHash[pgno % N_PG_HASH]; while( p && p->pgno!=pgno ){ p = p->pNextHash; @@ -162,21 +264,23 @@ static PgHdr *sqlite_pager_lookup(Pager *pPager, Pgno pgno){ ** opened. Any outstanding pages are invalidated and subsequent attempts ** to access those pages will likely result in a coredump. */ -static void sqlite_pager_reset(Pager *pPager){ +static void pager_reset(Pager *pPager){ PgHdr *pPg, *pNext; - for(pPg=pPager->pFirst; pPg; pPg=pNext){ - pNext = pPg->pNext; - sqlite_free(pPg); + for(pPg=pPager->pAll; pPg; pPg=pNext){ + pNext = pPg->pNextAll; + sqliteFree(pPg); } pPager->pFirst = 0; - pPager->pNext = 0; + pPager->pLast = 0; + pPager->pAll = 0; memset(pPager->aHash, 0, sizeof(pPager->aHash)); pPager->nPage = 0; if( pPager->state==SQLITE_WRITELOCK ){ - sqlite_pager_rollback(pPager); + sqlitepager_rollback(pPager); } - sqlite_pager_unlock(pPager->fd); + pager_unlock(pPager->fd); pPager->state = SQLITE_UNLOCK; + pPager->dbSize = -1; pPager->nRef = 0; } @@ -193,178 +297,155 @@ static void sqlite_pager_reset(Pager *pPager){ ** should get a write lock on the database without first getting a lock ** on the journal. So this routine should never fail. But it can fail ** if another process is not playing by the rules. If it does fail, -** all in-memory cache pages are invalidated and this routine returns -** SQLITE_PROTOCOL. SQLITE_OK is returned on success. +** all in-memory cache pages are invalidated, the PAGER_ERR_LOCK bit +** is set in pPager->errMask, and this routine returns SQLITE_PROTOCOL. +** SQLITE_OK is returned on success. */ -static int sqlite_pager_unwritelock(Pager *pPager){ +static int pager_unwritelock(Pager *pPager){ int rc; - assert( pPager->state==SQLITE_WRITELOCK ); - sqlite_pager_unlock(pPager->fd); - rc = sqlite_pager_lock(pPager->fd, 0); + PgHdr *pPg; + if( pPager->state!=SQLITE_WRITELOCK ) return SQLITE_OK; + pager_unlock(pPager->fd); + rc = pager_lock(pPager->fd, 0); unlink(pPager->zJournal); close(pPager->jfd); pPager->jfd = -1; + for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){ + pPg->inJournal = 0; + pPg->dirty = 0; + } if( rc!=SQLITE_OK ){ pPager->state = SQLITE_UNLOCK; - sqlite_pager_reset(pPager); rc = SQLITE_PROTOCOL; + pPager->errMask |= PAGER_ERR_LOCK; }else{ + rc = SQLITE_OK; pPager->state = SQLITE_READLOCK; } return rc; } - /* ** Playback the journal and thus restore the database file to ** the state it was in before we started making changes. ** -** A journal consists of multiple segments. Every segment begins -** with a single page containing SQLITE_INDEX_SIZE page numbers. This -** first page is called the index. Most segments have SQLITE_INDEX_SIZE -** additional pages after the index. The N-th page after the index -** contains the contents of a page in the database file before that -** page was changed. The N-th entry in the index tells which page -** of the index file the data is for. +** The journal file format is as follows: There is an initial +** file-type string for sanity checking. Then there is a single +** Pgno number which is the number of pages in the database before +** changes were made. The database is truncated to this size. +** Next come zero or more page records which each page record +** consists of a Pgno, SQLITE_PAGE_SIZE bytes of data. ** -** The first segment of a journal is formatted slightly differently. -** The first segment contains an index but only SQLITE_INDEX_SIZE-1 -** data pages. The first page number in the index is actually the -** total number of pages in the original file. This number is used -** to truncate the original database file back to its original size. -** The second number in the index page is the page number for the -** first data page. And so forth. +** For playback, the pages have to be read from the journal in +** reverse order and put back into the original database file. ** -** We really need to playback the journal beginning at the end -** and working backwards toward the beginning. That way changes -** to the database are undone in the reverse order from the way they -** were applied. This is important if the same page is changed -** more than once. But many operating systems work more efficiently -** if data is read forward instead of backwards. So for efficiency -** we want to read the data in the forward direction. -** -** This routine starts with the last segment and works backwards -** toward the first. Within each segment, however, data is read -** in the forward direction for efficiency. Care is taken that -** only the first appearance of each page is copied over to the -** database file. If a page appears in the index more than once, -** only the first occurrance is written. A hash table is used to -** keep track of which pages have been written and which have not. +** If the file opened as the journal file is not a well-formed +** journal file (as determined by looking at the magic number +** at the beginning) then this routine returns SQLITE_PROTOCOL. +** If any other errors occur during playback, the database will +** likely be corrupted, so the PAGER_ERR_CORRUPT bit is set in +** pPager->errMask and SQLITE_CORRUPT is returned. If it all +** works, then this routine returns SQLITE_OK. */ -static int sqlite_pager_playback(Pager *pPager){ - int nSeg; /* Number of segments */ - int i, j; /* Loop counters */ - Pgno mxPg = 0; /* Size of the original file in pages */ - struct stat statbuf; /* Used to size the journal */ - Pgno aIndex[SQLITE_INDEX_SIZE]; /* The index page */ - char aBuf[SQLITE_PAGE_SIZE]; /* Page transfer buffer */ - Pgno aHash[SQLITE_INDEX_SIZE*2-1]; /* Hash table for pages read so far */ +static int pager_playback(Pager *pPager){ + int nRec; /* Number of Records */ + int i; /* Loop counter */ + Pgno mxPg = 0; /* Size of the original file in pages */ + struct stat statbuf; /* Used to size the journal */ + PgHdr *pPg; /* An existing page in the cache */ + PageRecord pgRec; + unsigned char aMagic[sizeof(aJournalMagic)]; int rc; - /* Figure out how many segments are in the journal. Remember that - ** the first segment is one page shorter than the others and that - ** the last segment may be incomplete. + /* Read the beginning of the journal and truncate the + ** database file back to its original size. */ - if( fstat(pPager->jfd; &statbuf)!=0 ){ - return SQLITE_OK; + assert( pPager->jfd>=0 ); + pager_seek(pPager->jfd, 0); + rc = pager_read(pPager->jfd, aMagic, sizeof(aMagic)); + if( rc!=SQLITE_OK || memcmp(aMagic,aJournalMagic,sizeof(aMagic))!=0 ){ + return SQLITE_PROTOCOL; } - if( statbuf.st_size <= SQLITE_INDEX_SIZE*SQLITE_PAGE_SIZE ){ - nSeg = 1; - }else{ - int nPage = statbuf.st_size/SQLITE_PAGE_SIZE; - nPage -= SQLITE_INDEX_SIZE; - nSeg = 1 + nPage/(SQLITE_INDEX_SIZE+1); + rc = pager_read(pPager->jfd, &mxPg, sizeof(mxPg)); + if( rc!=SQLITE_OK ){ + return SQLITE_PROTOCOL; + } + pager_truncate(pPager->fd, mxPg); + pPager->dbSize = mxPg; + + /* Begin reading the journal beginning at the end and moving + ** toward the beginning. + */ + if( fstat(pPager->jfd, &statbuf)!=0 ){ + return SQLITE_OK; } + nRec = (statbuf.st_size - (sizeof(aMagic)+sizeof(Pgno))) / sizeof(PageRecord); /* Process segments beginning with the last and working backwards ** to the first. */ - for(i=nSeg-1; i>=0; i--){ + for(i=nRec-1; i>=0; i--){ /* Seek to the beginning of the segment */ - sqlite_pager_seekpage(pPager->jfd, - i>0 ? i*(SQLITE_INDEX_SIZE + 1) - 1 : 0, - SEEK_SET - ); - - /* Initialize the hash table used to avoid copying duplicate pages */ - memset(aHash, 0, sizeof(aHash)); - - /* Read the index page */ - sqlite_pager_readpage(pPager->jfd, aIndex); - - /* Extract the original file size from the first index entry if this - ** is the first segment */ - if( i==0 ){ - mxPg = aIndex[0]; - aIndex[0] = 0; + off_t ofst; + ofst = i*sizeof(PageRecord) + sizeof(aMagic) + sizeof(Pgno); + rc = pager_seek(pPager->jfd, ofst); + if( rc!=SQLITE_OK ) break; + rc = pager_read(pPager->jfd, &pgRec, sizeof(pgRec)); + if( rc!=SQLITE_OK ) break; + + /* Sanity checking on the page */ + if( pgRec.pgno>mxPg || pgRec.pgno==0 ){ + rc = SQLITE_CORRUPT; + break; } - /* Process pages of this segment in forward order + /* Playback the page. Update the in-memory copy of the page + ** at the same time, if there is one. */ - for(j=0; j<SQLITE_INDEX_SIZE; j++){ - Pgno pgno = aIndex[i]; - void *pBuf; - PgHdr *pPg; - - /* 0 means "no such page". Skip zero entries */ - if( pgno==0 ) continue; - - /* Check to see if pgno is in the hash table. Skip this - ** entry if it is. - */ - h = pgno % (SQLITE_PAGE_SIZE-1); - while( aHash[h]!=0 && aHash[h]!=pgno ){ - h++; - if( h>=SQLITE_PAGE_SIZE-1 ) h = 0; - } - if( aHash[h]==pgno ){ - lseek(pPager->jfd, SQLITE_PAGE_SIZE, SEEK_CUR); - continue; - } - aHash[h] = pgno; - - /* Playback the page. Update the in-memory copy of the page - ** at the same time, if there is one. - */ - pPg = sqlite_pager_lookup(pPager, pgno); - if( pPg ){ - pBuf = PGHDR_TO_DATA(pPg); - }else{ - pBuf = aBuf; - } - sqlite_pager_readpage(pPager->jfd, pBuf); - sqlite_pager_seekpage(pPager->fd, pgno, SEEK_SET); - rc = sqlite_pager_writepage(pPager->fd, pBuf); - if( rc!=SQLITE_OK ) return rc; + pPg = pager_lookup(pPager, pgRec.pgno); + if( pPg ){ + memcpy(PGHDR_TO_DATA(pPg), pgRec.aData, SQLITE_PAGE_SIZE); } + rc = pager_seek(pPager->fd, (pgRec.pgno-1)*SQLITE_PAGE_SIZE); + if( rc!=SQLITE_OK ) break; + rc = pager_write(pPager->fd, pgRec.aData, SQLITE_PAGE_SIZE); + if( rc!=SQLITE_OK ) break; } - - /* Truncate the database back to its original size - */ - if( mxPg>0 ){ - ftrucate(pPager->fd, mxPg * SQLITE_PAGE_SIZE); + if( rc!=SQLITE_OK ){ + pager_unwritelock(pPager); + pPager->errMask |= PAGER_ERR_CORRUPT; + rc = SQLITE_CORRUPT; + }else{ + rc = pager_unwritelock(pPager); } - return SQLITE_OK; + return rc; } /* ** Create a new page cache and put a pointer to the page cache in *ppPager. ** The file to be cached need not exist. The file is not opened until -** the first call to sqlite_pager_get() and is only held open until the -** last page is released using sqlite_pager_unref(). +** the first call to sqlitepager_get() and is only held open until the +** last page is released using sqlitepager_unref(). */ -int sqlite_pager_open(Pager **ppPager, const char *zFilename, int mxPage){ +int sqlitepager_open(Pager **ppPager, const char *zFilename, int mxPage){ Pager *pPager; int nameLen; int fd; - fd = open(zFilename, O_RDWR, 0644); + *ppPager = 0; + if( sqlite_malloc_failed ){ + return SQLITE_NOMEM; + } + fd = open(zFilename, O_RDWR|O_CREAT, 0644); if( fd<0 ){ return SQLITE_CANTOPEN; } nameLen = strlen(zFilename); pPager = sqliteMalloc( sizeof(*pPager) + nameLen*2 + 30 ); - if( pPager==0 ) return SQLITE_NOMEM; + if( pPager==0 ){ + close(fd); + return SQLITE_NOMEM; + } pPager->zFilename = (char*)&pPager[1]; pPager->zJournal = &pPager->zFilename[nameLen+1]; strcpy(pPager->zFilename, zFilename); @@ -377,6 +458,7 @@ int sqlite_pager_open(Pager **ppPager, const char *zFilename, int mxPage){ pPager->nPage = 0; pPager->mxPage = mxPage>10 ? mxPage : 10; pPager->state = SQLITE_UNLOCK; + pPager->errMask = 0; pPager->pFirst = 0; pPager->pLast = 0; memset(pPager->aHash, 0, sizeof(pPager->aHash)); @@ -387,9 +469,10 @@ int sqlite_pager_open(Pager **ppPager, const char *zFilename, int mxPage){ /* ** Return the total number of pages in the file opened by pPager. */ -int sqlite_pager_pagecount(Pager *pPager){ +int sqlitepager_pagecount(Pager *pPager){ int n; struct stat statbuf; + assert( pPager!=0 ); if( pPager->dbSize>=0 ){ return pPager->dbSize; } @@ -398,7 +481,7 @@ int sqlite_pager_pagecount(Pager *pPager){ }else{ n = statbuf.st_size/SQLITE_PAGE_SIZE; } - if( pPager->state!=SQLITE_NOLOCK ){ + if( pPager->state!=SQLITE_UNLOCK ){ pPager->dbSize = n; } return n; @@ -413,17 +496,16 @@ int sqlite_pager_pagecount(Pager *pPager){ ** with this page cache after this function returns will likely ** result in a coredump. */ -int sqlite_pager_close(Pager *pPager){ - int i; - PgHdr *pPg; +int sqlitepager_close(Pager *pPager){ + PgHdr *pPg, *pNext; switch( pPager->state ){ case SQLITE_WRITELOCK: { - sqlite_pager_rollback(pPager); - sqlite_pager_unlock(pPager->fd); + sqlitepager_rollback(pPager); + pager_unlock(pPager->fd); break; } case SQLITE_READLOCK: { - sqlite_pager_unlock(pPager->fd); + pager_unlock(pPager->fd); break; } default: { @@ -431,12 +513,9 @@ int sqlite_pager_close(Pager *pPager){ break; } } - for(i=0; i<N_PG_HASH; i++){ - PgHdr *pNext; - for(pPg=pPager->aHash[i]; pPg; pPg=pNext){ - pNext = pPg->pNextHash; - sqliteFree(pPg); - } + for(pPg=pPager->pAll; pPg; pPg=pNext){ + pNext = pPg->pNextAll; + sqliteFree(pPg); } if( pPager->fd>=0 ) close(pPager->fd); assert( pPager->jfd<0 ); @@ -447,25 +526,41 @@ int sqlite_pager_close(Pager *pPager){ /* ** Return the page number for the given page data */ -int sqlite_pager_pagenumber(void *pData){ +Pgno sqlitepager_pagenumber(void *pData){ PgHdr *p = DATA_TO_PGHDR(pData); return p->pgno; } /* -** Acquire a page +** Acquire a page. +** +** A read lock is obtained for the first page acquired. The lock +** is dropped when the last page is released. +** +** The acquisition might fail for several reasons. In all cases, +** an appropriate error code is returned and *ppPage is set to NULL. */ -int sqlite_pager_get(Pager *pPager, int pgno, void **ppPage){ +int sqlitepager_get(Pager *pPager, Pgno pgno, void **ppPage){ PgHdr *pPg; + /* Make sure we have not hit any critical errors. + */ + if( pPager==0 || pgno==0 ){ + return SQLITE_ERROR; + } + if( pPager->errMask & ~(PAGER_ERR_FULL) ){ + return pager_errcode(pPager); + } + /* If this is the first page accessed, then get a read lock ** on the database file. */ if( pPager->nRef==0 ){ - if( sqlite_pager_lock(pPager->fd, 0)!=0 ){ + if( pager_lock(pPager->fd, 0)!=0 ){ *ppPage = 0; return SQLITE_BUSY; } + pPager->state = SQLITE_READLOCK; /* If a journal file exists, try to play it back. */ @@ -476,16 +571,18 @@ int sqlite_pager_get(Pager *pPager, int pgno, void **ppPage){ ** we cannot get exclusive access to the journal file */ pPager->jfd = open(pPager->zJournal, O_RDONLY, 0); - if( pPager->jfd<0 || sqlite_pager_lock(pPager->jfd, 1)!=0 ){ + if( pPager->jfd<0 || pager_lock(pPager->jfd, 1)!=0 ){ if( pPager->jfd>=0 ){ close(pPager->jfd); pPager->jfd = -1; } - sqlite_pager_unlock(pPager->fd); + pager_unlock(pPager->fd); *ppPage = 0; return SQLITE_BUSY; } /* Get a write lock on the database */ - sqlite_pager_unlock(pPager->fd); - if( sqlite_pager_lock(pPager->fd, 1)!=0 ){ + pager_unlock(pPager->fd); + if( pager_lock(pPager->fd, 1)!=0 ){ + close(pPager->jfd); + pPager->jfd = -1; *ppPage = 0; return SQLITE_PROTOCOL; } @@ -493,36 +590,77 @@ int sqlite_pager_get(Pager *pPager, int pgno, void **ppPage){ /* Playback and delete the journal. Drop the database write ** lock and reacquire the read lock. */ - sqlite_pager_playback(pPager); - rc = sqlite_pager_unwritelock(pPager); - if( rc!=SQLITE_OK ){ return SQLITE_PROTOCOL; } + rc = pager_playback(pPager); + if( rc!=SQLITE_OK ){ + return rc; + } } pPg = 0; + pPager->nMiss++; }else{ /* Search for page in cache */ - pPg = sqlite_pager_lookup(pPager, pgno); + pPg = pager_lookup(pPager, pgno); + pPager->nHit++; } if( pPg==0 ){ + /* The requested page is not in the page cache. */ int h; if( pPager->nPage<pPager->mxPage || pPager->pFirst==0 ){ /* Create a new page */ - pPg = sqlite_malloc( sizeof(*pPg) + SQLITE_PAGE_SIZE ); + pPg = sqliteMalloc( sizeof(*pPg) + SQLITE_PAGE_SIZE ); + if( pPg==0 ){ + *ppPage = 0; + pager_unwritelock(pPager); + pPager->errMask |= PAGER_ERR_MEM; + return SQLITE_NOMEM; + } pPg->pPager = pPager; + pPg->pNextAll = pPager->pAll; + if( pPager->pAll ){ + pPager->pAll->pPrevAll = pPg; + } + pPg->pPrevAll = 0; + pPager->nPage++; }else{ - /* Recycle an older page */ + /* Recycle an older page. First locate the page to be recycled. + ** Try to find one that is not dirty and is near the head of + ** of the free list */ + int cnt = 4; pPg = pPager->pFirst; + while( pPg->dirty && 0<cnt-- ){ + pPg = pPg->pNextFree; + } + if( pPg==0 || pPg->dirty ) pPg = pPager->pFirst; + assert( pPg->nRef==0 ); + + /* If the page to be recycled is dirty, sync the journal and write + ** the old page into the database. */ if( pPg->dirty ){ int rc; - sqlite_pager_seekpage(pPager->fd, pPg->pgno, SEEK_SET); - rc = sqlite_pager_writepage(pPager->fd, PGHDR_TO_DATA(pPg)); + assert( pPg->inJournal==1 ); + assert( pPager->state==SQLITE_WRITELOCK ); + rc = fsync(pPager->jfd); + if( rc!=0 ){ + rc = sqlitepager_rollback(pPager); + *ppPage = 0; + if( rc==SQLITE_OK ) rc = SQLITE_IOERR; + return rc; + } + pager_seek(pPager->fd, (pPg->pgno-1)*SQLITE_PAGE_SIZE); + rc = pager_write(pPager->fd, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE); if( rc!=SQLITE_OK ){ + rc = sqlitepager_rollback(pPager); *ppPage = 0; + if( rc==SQLITE_OK ) rc = SQLITE_FULL; return rc; } - } - pPager->pFirst = pPg->pNext; + } + + /* Unlink the old page from the free list and the hash table + */ + pPager->pFirst = pPg->pNextFree; if( pPager->pFirst ){ - pPager->pFirst->pPrev = 0; + pPager->pFirst->pPrevFree = 0; }else{ pPager->pLast = 0; } @@ -532,36 +670,41 @@ int sqlite_pager_get(Pager *pPager, int pgno, void **ppPage){ if( pPg->pPrevHash ){ pPg->pPrevHash->pNextHash = pPg->pNextHash; }else{ - h = sqlite_pager_hash(pPg->pgno); + h = pager_hash(pPg->pgno); assert( pPager->aHash[h]==pPg ); pPager->aHash[h] = pPg->pNextHash; } + pPager->nOvfl++; } pPg->pgno = pgno; pPg->inJournal = 0; pPg->dirty = 0; pPg->nRef = 1; - h = sqlite_pager_hash(pgno); + pPager->nRef++; + h = pager_hash(pgno); pPg->pNextHash = pPager->aHash[h]; pPager->aHash[h] = pPg; if( pPg->pNextHash ){ assert( pPg->pNextHash->pPrevHash==0 ); pPg->pNextHash->pPrevHash = pPg; } - sqlite_pager_seekpage(pPager->fd, pgno, SEEK_SET); - sqlite_pager_readpage(pPager->fd, PGHDR_TO_DATA(pPg)); + pager_seek(pPager->fd, (pgno-1)*SQLITE_PAGE_SIZE); + pager_read(pPager->fd, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE); }else{ + /* The requested page is in the page cache. */ if( pPg->nRef==0 ){ - if( pPg->pPrev ){ - pPg->pPrev->pNext = pPg->pNext; + /* The page is currently on the freelist. Remove it. */ + if( pPg->pPrevFree ){ + pPg->pPrevFree->pNextFree = pPg->pNextFree; }else{ - pPager->pFirst = pPg->pNext; + pPager->pFirst = pPg->pNextFree; } - if( pPg->pNext ){ - pPg->pNext->pPrev = pPg->pPrev; + if( pPg->pNextFree ){ + pPg->pNextFree->pPrevFree = pPg->pPrevFree; }else{ - pPager->pLast = pPg->pPrev; + pPager->pLast = pPg->pPrevFree; } + pPager->nRef++; } pPg->nRef++; } @@ -574,31 +717,43 @@ int sqlite_pager_get(Pager *pPager, int pgno, void **ppPage){ ** ** If the number of references to the page drop to zero, then the ** page is added to the LRU list. When all references to all pages -** are released, a rollback occurs, and the lock on the database is +** are released, a rollback occurs and the lock on the database is ** removed. */ -int sqlite_pager_unref(void *pData){ +int sqlitepager_unref(void *pData){ Pager *pPager; PgHdr *pPg; + + /* Decrement the reference count for this page + */ pPg = DATA_TO_PGHDR(pData); assert( pPg->nRef>0 ); pPager = pPg->pPager; pPg->nRef--; + + /* When the number of references to a page reach 0, add the + ** page to the freelist. + */ if( pPg->nRef==0 ){ - pPg->pNext = 0; - pPg->pPrev = pPager->pLast; + pPg->pNextFree = 0; + pPg->pPrevFree = pPager->pLast; pPager->pLast = pPg; - if( pPg->pPrev ){ - pPg->pPrev->pNext = pPg; + if( pPg->pPrevFree ){ + pPg->pPrevFree->pNextFree = pPg; }else{ pPager->pFirst = pPg; } + + /* When all pages reach the freelist, drop the read lock from + ** the database file. + */ + pPager->nRef--; + assert( pPager->nRef>=0 ); + if( pPager->nRef==0 ){ + pager_reset(pPager); + } } - pPager->nRef--; - assert( pPager->nRef>=0 ); - if( pPager->nRef==0 ){ - sqlite_pager_reset(pPager); - } + return SQLITE_OK; } /* @@ -611,87 +766,120 @@ int sqlite_pager_unref(void *pData){ ** lock could not be acquired, this routine returns SQLITE_BUSY. The ** calling routine must check for that routine and be careful not to ** change any page data until this routine returns SQLITE_OK. +** +** If the journal file could not be written because the disk is full, +** then this routine returns SQLITE_FULL and does an immediate rollback. +** All subsequent write attempts also return SQLITE_FULL until there +** is a call to sqlitepager_commit() or sqlitepager_rollback() to +** reset. */ -int sqlite_pager_write(void *pData){ +int sqlitepager_write(void *pData){ PgHdr *pPg = DATA_TO_PGHDR(pData); Pager *pPager = pPg->pPager; int rc; + if( pPager->errMask ){ + return pager_errcode(pPager); + } + pPg->dirty = 1; if( pPg->inJournal ){ return SQLITE_OK; } - if( pPager->state==SQLITE_UNLOCK ){ return SQLITE_PROTOCOL; } + assert( pPager->state!=SQLITE_UNLOCK ); if( pPager->state==SQLITE_READLOCK ){ pPager->jfd = open(pPager->zJournal, O_RDWR|O_CREAT, 0644); if( pPager->jfd<0 ){ return SQLITE_CANTOPEN; } - if( sqlite_pager_lock(pPager->jfd, 1) ){ + if( pager_lock(pPager->jfd, 1) ){ close(pPager->jfd); pPager->jfd = -1; return SQLITE_BUSY; } - sqlite_pager_unlock(pPager->fd); - if( sqlite_pager_lock(pPager->fd, 1) ){ + pager_unlock(pPager->fd); + if( pager_lock(pPager->fd, 1) ){ close(pPager->jfd); pPager->jfd = -1; pPager->state = SQLITE_UNLOCK; - sqlite_pager_reset(pPager); + pPager->errMask |= PAGER_ERR_LOCK; return SQLITE_PROTOCOL; } pPager->state = SQLITE_WRITELOCK; - pPager->jSize = 1; - pPager->aIdx[0] = pPager->dbSize; + sqlitepager_pagecount(pPager); pPager->origDbSize = pPager->dbSize; - pPager->nIdx = 1; + rc = pager_write(pPager->jfd, aJournalMagic, sizeof(aJournalMagic)); + if( rc==SQLITE_OK ){ + rc = pager_write(pPager->jfd, &pPager->dbSize, sizeof(Pgno)); + } + if( rc!=SQLITE_OK ){ + rc = pager_unwritelock(pPager); + if( rc==SQLITE_OK ) rc = SQLITE_FULL; + return rc; + } } - /* Write this page to the journal */ + assert( pPager->state==SQLITE_WRITELOCK ); assert( pPager->jfd>=0 ); - if( pPg->pgno >= pPager->origDbSize ){ - sqlite_pager_seekpage(pPager->fd, pPg->pgno, SEEK_SET); - rc = sqlite_pager_writepage(pPager->fd, pData); - pPg->inJournal = 1; - return rc; + if( pPg->pgno <= pPager->origDbSize ){ + rc = pager_write(pPager->jfd, &pPg->pgno, sizeof(Pgno)); + if( rc==SQLITE_OK ){ + rc = pager_write(pPager->jfd, pData, SQLITE_PAGE_SIZE); + } + if( rc!=SQLITE_OK ){ + sqlitepager_rollback(pPager); + pPager->errMask |= PAGER_ERR_FULL; + return rc; + } } - pPager->aIdx[pPager->nIdx++] = pPg->pgno; - sqlite_pager_seekpage(pPager->jfd, pPager->jSize++, SEEK_SET); - rc = sqlite_pager_write(pPager->jfd, pData); pPg->inJournal = 1; - if( pPager->nIdx==SQLITE_INDEX_SIZE ){ - sqlite_pager_seekpage(pPager->jfd, pPager->idxPgno, SEEK_SET); - rc = sqlite_pager_writepage(pPager->jfd, &pPager->aIdx); - pPager->nIdx = 0; - pPager->jSize++; - } return rc; } /* ** Commit all changes to the database and release the write lock. +** +** If the commit fails for any reason, a rollback attempt is made +** and an error code is returned. If the commit worked, SQLITE_OK +** is returned. */ -int sqlite_pager_commit(Pager*){ +int sqlitepager_commit(Pager *pPager){ int i, rc; PgHdr *pPg; - assert( pPager->state==SQLITE_WRITELOCK ); + + if( pPager->errMask==PAGER_ERR_FULL ){ + rc = sqlitepager_rollback(pPager); + if( rc==SQLITE_OK ) rc = SQLITE_FULL; + return rc; + } + if( pPager->errMask!=0 ){ + rc = pager_errcode(pPager); + return rc; + } + if( pPager->state!=SQLITE_WRITELOCK ){ + return SQLITE_ERROR; + } assert( pPager->jfd>=0 ); - memset(&pPager->aIdx[&pPager->nIdx], 0, - (SQLITE_INDEX_SIZE - pPager->nIdx)*sizeof(Pgno)); - sqlite_pager_seekpage(pPager->jfd, pPager->idxPgno, SEEK_SET); - rc = sqlite_pager_writepage(pPager->jfd, &pPager->aIdx); if( fsync(pPager->jfd) ){ - return SQLITE_IOERR; + goto commit_abort; } for(i=0; i<N_PG_HASH; i++){ for(pPg=pPager->aHash[i]; pPg; pPg=pPg->pNextHash){ if( pPg->dirty==0 ) continue; - rc = sqlite_pager_seekpage(pPager->fd, pPg->pgno, SEEK_SET); - if( rc!=SQLITE_OK ) return rc; - rc = sqlite_pager_writePage(pPager->fd, PGHDR_TO_DATA(pPg)); - if( rc!=SQLITE_OK ) return rc; + rc = pager_seek(pPager->fd, (pPg->pgno-1)*SQLITE_PAGE_SIZE); + if( rc!=SQLITE_OK ) goto commit_abort; + rc = pager_write(pPager->fd, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE); + if( rc!=SQLITE_OK ) goto commit_abort; } } - if( fsync(pPager->fd) ){ - return SQLITE_IOERR; + if( fsync(pPager->fd) ) goto commit_abort; + rc = pager_unwritelock(pPager); + pPager->dbSize = -1; + return rc; + + /* Jump here if anything goes wrong during the commit process. + */ +commit_abort: + rc = sqlitepager_rollback(pPager); + if( rc==SQLITE_OK ){ + rc = SQLITE_FULL; } - rc = sqlite_pager_unwritelock(pPager); return rc; } @@ -699,17 +887,44 @@ int sqlite_pager_commit(Pager*){ ** Rollback all changes. The database falls back to read-only mode. ** All in-memory cache pages revert to their original data contents. ** The journal is deleted. +** +** This routine cannot fail unless some other process is not following +** the correct locking protocol (SQLITE_PROTOCOL) or unless some other +** process is writing trash into the journal file (SQLITE_CORRUPT) or +** unless a prior malloc() failed (SQLITE_NOMEM). Appropriate error +** codes are returned for all these occasions. Otherwise, +** SQLITE_OK is returned. */ -int sqlite_pager_rollback(Pager *pPager){ +int sqlitepager_rollback(Pager *pPager){ int rc; - if( pPager->state!=SQLITE_WRITELOCK ) return SQLITE_OK; - memset(&pPager->aIdx[&pPager->nIdx], 0, - (SQLITE_INDEX_SIZE - pPager->nIdx)*sizeof(Pgno)); - sqlite_pager_seekpage(pPager->jfd, pPager->idxPgno, SEEK_SET); - rc = sqlite_pager_writepage(pPager->jfd, &pPager->aIdx); - rc = sqlite_pager_playback(pPager); + if( pPager->errMask!=0 && pPager->errMask!=PAGER_ERR_FULL ){ + return pager_errcode(pPager); + } + if( pPager->state!=SQLITE_WRITELOCK ){ + return SQLITE_OK; + } + rc = pager_playback(pPager); if( rc!=SQLITE_OK ){ - rc = sqlite_pager_unwritelock(pPager); + rc = SQLITE_CORRUPT; + pPager->errMask |= PAGER_ERR_CORRUPT; } + pPager->dbSize = -1; return rc; }; + +/* +** This routine is used for testing and analysis only. +*/ +int *sqlitepager_stats(Pager *pPager){ + static int a[9]; + a[0] = pPager->nRef; + a[1] = pPager->nPage; + a[2] = pPager->mxPage; + a[3] = pPager->dbSize; + a[4] = pPager->state; + a[5] = pPager->errMask; + a[6] = pPager->nHit; + a[7] = pPager->nMiss; + a[8] = pPager->nOvfl; + return a; +} |