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Allocation-map update paths compare two LSNs against that base while deciding whether a metapage must inherit an older recovery LSN or a newer commit LSN. lmLogSync() updates log->syncpt while holding log->loglock. The pmap update paths protect the metapage and logsynclist state with log->synclock instead, so their plain logdiff() reads of log->syncpt can race with the sync point update. In dbUpdatePMap(), the transaction LSN difference is even computed before taking log->synclock and then compared with a metapage difference computed later, allowing one inheritance decision to use two different sync point bases. A mixed-base comparison can miss an older transaction LSN inheritance. After the transaction block is removed from the logsynclist, the allocation-map metapage can then remain too young and allow a later sync point to advance past allocation log records before the persistent map page reaches home. Snapshot log->syncpt once for each logsynclist ordering decision and use that snapshot for all comparisons in the decision. Mark the concurrent syncpt stores with WRITE_ONCE() to pair with the snapshots and document that the field is intentionally accessed locklessly relative to log->synclock. Signed-off-by: Cen Zhang --- fs/jfs/jfs_dmap.c | 12 ++++++------ fs/jfs/jfs_imap.c | 11 ++++++----- fs/jfs/jfs_logmgr.c | 5 +++-- fs/jfs/jfs_logmgr.h | 10 ++++++++++ fs/jfs/jfs_txnmgr.c | 9 ++++++--- 5 files changed, 31 insertions(+), 16 deletions(-) diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c index 2abe8cc02ee6f..d0b31ebd30cad 100644 --- a/fs/jfs/jfs_dmap.c +++ b/fs/jfs/jfs_dmap.c @@ -446,7 +446,7 @@ dbUpdatePMap(struct inode *ipbmap, struct dmap *dp; struct metapage *mp; struct jfs_log *log; - int lsn, difft, diffp; + int lsn, difft, diffp, syncpt; unsigned long flags; =20 /* the blocks better be within the mapsize. */ @@ -458,10 +458,8 @@ dbUpdatePMap(struct inode *ipbmap, return -EIO; } =20 - /* compute delta of transaction lsn from log syncpt */ lsn =3D tblk->lsn; log =3D (struct jfs_log *) JFS_SBI(tblk->sb)->log; - logdiff(difft, lsn, log); =20 /* * update the block state a dmap at a time. @@ -553,9 +551,11 @@ dbUpdatePMap(struct inode *ipbmap, lastlblkno =3D lblkno; =20 LOGSYNC_LOCK(log, flags); + syncpt =3D READ_ONCE(log->syncpt); + difft =3D logdiff_syncpt(lsn, syncpt, log->logsize); if (mp->lsn !=3D 0) { /* inherit older/smaller lsn */ - logdiff(diffp, mp->lsn, log); + diffp =3D logdiff_syncpt(mp->lsn, syncpt, log->logsize); if (difft < diffp) { mp->lsn =3D lsn; =20 @@ -564,8 +564,8 @@ dbUpdatePMap(struct inode *ipbmap, } =20 /* inherit younger/larger clsn */ - logdiff(difft, tblk->clsn, log); - logdiff(diffp, mp->clsn, log); + difft =3D logdiff_syncpt(tblk->clsn, syncpt, log->logsize); + diffp =3D logdiff_syncpt(mp->clsn, syncpt, log->logsize); if (difft > diffp) mp->clsn =3D tblk->clsn; } else { diff --git a/fs/jfs/jfs_imap.c b/fs/jfs/jfs_imap.c index 294a67327c735..62fe50a65aa50 100644 --- a/fs/jfs/jfs_imap.c +++ b/fs/jfs/jfs_imap.c @@ -2732,7 +2732,7 @@ diUpdatePMap(struct inode *ipimap, struct inomap *imap; u32 mask; struct jfs_log *log; - int lsn, difft, diffp; + int lsn, difft, diffp, syncpt; unsigned long flags; =20 imap =3D JFS_IP(ipimap)->i_imap; @@ -2808,10 +2808,11 @@ diUpdatePMap(struct inode *ipimap, lsn =3D tblk->lsn; log =3D JFS_SBI(tblk->sb)->log; LOGSYNC_LOCK(log, flags); + syncpt =3D READ_ONCE(log->syncpt); if (mp->lsn !=3D 0) { /* inherit older/smaller lsn */ - logdiff(difft, lsn, log); - logdiff(diffp, mp->lsn, log); + difft =3D logdiff_syncpt(lsn, syncpt, log->logsize); + diffp =3D logdiff_syncpt(mp->lsn, syncpt, log->logsize); if (difft < diffp) { mp->lsn =3D lsn; /* move mp after tblock in logsync list */ @@ -2819,8 +2820,8 @@ diUpdatePMap(struct inode *ipimap, } /* inherit younger/larger clsn */ assert(mp->clsn); - logdiff(difft, tblk->clsn, log); - logdiff(diffp, mp->clsn, log); + difft =3D logdiff_syncpt(tblk->clsn, syncpt, log->logsize); + diffp =3D logdiff_syncpt(mp->clsn, syncpt, log->logsize); if (difft > diffp) mp->clsn =3D tblk->clsn; } else { diff --git a/fs/jfs/jfs_logmgr.c b/fs/jfs/jfs_logmgr.c index ada00d5bc2146..5483de65d6d55 100644 --- a/fs/jfs/jfs_logmgr.c +++ b/fs/jfs/jfs_logmgr.c @@ -968,7 +968,7 @@ static int lmLogSync(struct jfs_log * log, int hard_syn= c) lrd.log.syncpt.sync =3D cpu_to_le32(log->sync); lsn =3D lmWriteRecord(log, NULL, &lrd, NULL); =20 - log->syncpt =3D log->sync; + WRITE_ONCE(log->syncpt, log->sync); } else lsn =3D log->lsn; =20 @@ -1002,7 +1002,8 @@ static int lmLogSync(struct jfs_log * log, int hard_s= ync) /* log->state =3D LOGWRAP; */ =20 /* reset sync point computation */ - log->syncpt =3D log->sync =3D lsn; + log->sync =3D lsn; + WRITE_ONCE(log->syncpt, lsn); log->nextsync =3D delta; } else /* next syncpt trigger =3D written + more */ diff --git a/fs/jfs/jfs_logmgr.h b/fs/jfs/jfs_logmgr.h index 8b8994e48cd08..7f534ea9605b6 100644 --- a/fs/jfs/jfs_logmgr.h +++ b/fs/jfs/jfs_logmgr.h @@ -487,6 +487,16 @@ struct logsyncblk { diff +=3D (log)->logsize;\ } =20 +static inline int logdiff_syncpt(int lsn, int syncpt, int logsize) +{ + int diff =3D lsn - syncpt; + + if (diff < 0) + diff +=3D logsize; + + return diff; +} + extern int lmLogOpen(struct super_block *sb); extern int lmLogClose(struct super_block *sb); extern int lmLogShutdown(struct jfs_log * log); diff --git a/fs/jfs/jfs_txnmgr.c b/fs/jfs/jfs_txnmgr.c index c16578af3a77e..db2f677742d1f 100644 --- a/fs/jfs/jfs_txnmgr.c +++ b/fs/jfs/jfs_txnmgr.c @@ -905,7 +905,7 @@ static void txUnlock(struct tblock * tblk) lid_t lid, next, llid, k; struct metapage *mp; struct jfs_log *log; - int difft, diffp; + int difft, diffp, syncpt; unsigned long flags; =20 jfs_info("txUnlock: tblk =3D 0x%p", tblk); @@ -935,8 +935,11 @@ static void txUnlock(struct tblock * tblk) /* inherit younger/larger clsn */ LOGSYNC_LOCK(log, flags); if (mp->clsn) { - logdiff(difft, tblk->clsn, log); - logdiff(diffp, mp->clsn, log); + syncpt =3D READ_ONCE(log->syncpt); + difft =3D logdiff_syncpt(tblk->clsn, syncpt, + log->logsize); + diffp =3D logdiff_syncpt(mp->clsn, syncpt, + log->logsize); if (difft > diffp) mp->clsn =3D tblk->clsn; } else