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Reduce the probability of low block numbers passed to ffs_snapblkfree() by

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skipping the call from ffs_snapremove() if the block number is zero.

Simplify snapshot locking in ffs_copyonwrite() and ffs_snapblkfree() by using
the same locking protocol for low block numbers as for larger block numbers.
This removes a lock leak that could happen if vn_lock() succeeded after
lockmgr() failed in ffs_snapblkfree().

Check if snapshot is gone before retrying a lock in ffs_copyonwrite().
This commit is contained in:
tegge 2005-10-09 19:45:01 +00:00
parent 4422105e30
commit 1a45f40f4f
1 changed files with 35 additions and 55 deletions
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90
sys/ufs/ffs/ffs_snapshot.c
View File

@ -1484,6 +1484,8 @@ ffs_snapremove(vp)
*/
for (blkno = 1; blkno < NDADDR; blkno++) {
dblk = DIP(ip, i_db[blkno]);
if (dblk == 0)
continue;
if (dblk == BLK_NOCOPY || dblk == BLK_SNAP)
DIP_SET(ip, i_db[blkno], 0);
else if ((dblk == blkstofrags(fs, blkno) &&
@ -1507,6 +1509,8 @@ ffs_snapremove(vp)
for (loc = 0; loc < last; loc++) {
if (ip->i_ump->um_fstype == UFS1) {
dblk = ((ufs1_daddr_t *)(ibp->b_data))[loc];
if (dblk == 0)
continue;
if (dblk == BLK_NOCOPY || dblk == BLK_SNAP)
((ufs1_daddr_t *)(ibp->b_data))[loc]= 0;
else if ((dblk == blkstofrags(fs, blkno) &&
@ -1519,6 +1523,8 @@ ffs_snapremove(vp)
continue;
}
dblk = ((ufs2_daddr_t *)(ibp->b_data))[loc];
if (dblk == 0)
continue;
if (dblk == BLK_NOCOPY || dblk == BLK_SNAP)
((ufs2_daddr_t *)(ibp->b_data))[loc] = 0;
else if ((dblk == blkstofrags(fs, blkno) &&
@ -1570,7 +1576,7 @@ ffs_snapblkfree(fs, devvp, bno, size, inum)
struct vnode *vp = NULL;
ufs_lbn_t lbn;
ufs2_daddr_t blkno;
int indiroff = 0, snapshot_locked = 0, error = 0, claimedblk = 0;
int indiroff = 0, error = 0, claimedblk = 0;
struct snapdata *sn;
lbn = fragstoblks(fs, bno);
@ -1581,6 +1587,10 @@ ffs_snapblkfree(fs, devvp, bno, size, inum)
VI_UNLOCK(devvp);
return (0);
}
if (lockmgr(&sn->sn_lock,
LK_INTERLOCK | LK_EXCLUSIVE | LK_SLEEPFAIL,
VI_MTX(devvp), td) != 0)
goto retry;
TAILQ_FOREACH(ip, &sn->sn_head, i_nextsnap) {
vp = ITOV(ip);
/*
@ -1589,12 +1599,6 @@ ffs_snapblkfree(fs, devvp, bno, size, inum)
if (lbn < NDADDR) {
blkno = DIP(ip, i_db[lbn]);
} else {
if (snapshot_locked == 0 &&
lockmgr(vp->v_vnlock,
LK_INTERLOCK | LK_EXCLUSIVE | LK_SLEEPFAIL,
VI_MTX(devvp), td) != 0)
goto retry;
snapshot_locked = 1;
td->td_pflags |= TDP_COWINPROGRESS;
error = UFS_BALLOC(vp, lblktosize(fs, (off_t)lbn),
fs->fs_bsize, KERNCRED, BA_METAONLY, &ibp);
@ -1624,16 +1628,6 @@ ffs_snapblkfree(fs, devvp, bno, size, inum)
*/
if (claimedblk)
panic("snapblkfree: inconsistent block type");
if (snapshot_locked == 0 &&
lockmgr(vp->v_vnlock,
LK_INTERLOCK | LK_EXCLUSIVE | LK_NOWAIT,
VI_MTX(devvp), td) != 0) {
if (lbn >= NDADDR)
bqrelse(ibp);
vn_lock(vp, LK_EXCLUSIVE | LK_SLEEPFAIL, td);
goto retry;
}
snapshot_locked = 1;
if (lbn < NDADDR) {
DIP_SET(ip, i_db[lbn], BLK_NOCOPY);
ip->i_flag |= IN_CHANGE | IN_UPDATE;
@ -1664,16 +1658,6 @@ ffs_snapblkfree(fs, devvp, bno, size, inum)
* routine as to why only a single snapshot needs to
* claim this block.
*/
if (snapshot_locked == 0 &&
lockmgr(vp->v_vnlock,
LK_INTERLOCK | LK_EXCLUSIVE | LK_NOWAIT,
VI_MTX(devvp), td) != 0) {
if (lbn >= NDADDR)
bqrelse(ibp);
vn_lock(vp, LK_EXCLUSIVE | LK_SLEEPFAIL, td);
goto retry;
}
snapshot_locked = 1;
if (size == fs->fs_bsize) {
#ifdef DEBUG
if (snapdebug)
@ -1758,10 +1742,7 @@ ffs_snapblkfree(fs, devvp, bno, size, inum)
* not be freed. Although space will be lost, the snapshot
* will stay consistent.
*/
if (snapshot_locked)
lockmgr(vp->v_vnlock, LK_RELEASE, NULL, td);
else
VI_UNLOCK(devvp);
lockmgr(vp->v_vnlock, LK_RELEASE, NULL, td);
return (error);
}
@ -1968,7 +1949,7 @@ ffs_copyonwrite(devvp, bp)
struct inode *ip;
struct vnode *vp = 0;
ufs2_daddr_t lbn, blkno, *snapblklist;
int lower, upper, mid, indiroff, snapshot_locked = 0, error = 0;
int lower, upper, mid, indiroff, error = 0;
int launched_async_io, prev_norunningbuf;
if (td->td_pflags & TDP_COWINPROGRESS)
@ -1979,6 +1960,11 @@ ffs_copyonwrite(devvp, bp)
*/
VI_LOCK(devvp);
sn = devvp->v_rdev->si_snapdata;
if (sn == NULL ||
TAILQ_FIRST(&sn->sn_head) == NULL) {
VI_UNLOCK(devvp);
return (0); /* No snapshot */
}
ip = TAILQ_FIRST(&sn->sn_head);
fs = ip->i_fs;
lbn = fragstoblks(fs, dbtofsb(fs, bp->b_blkno));
@ -2009,7 +1995,20 @@ ffs_copyonwrite(devvp, bp)
/*
* Not in the precomputed list, so check the snapshots.
*/
retry:
while (lockmgr(&sn->sn_lock,
LK_INTERLOCK | LK_EXCLUSIVE | LK_SLEEPFAIL,
VI_MTX(devvp), td) != 0) {
VI_LOCK(devvp);
sn = devvp->v_rdev->si_snapdata;
if (sn == NULL ||
TAILQ_FIRST(&sn->sn_head) == NULL) {
VI_UNLOCK(devvp);
if (bp->b_runningbufspace)
atomic_add_int(&runningbufspace,
bp->b_runningbufspace);
return (0); /* Snapshot gone */
}
}
TAILQ_FOREACH(ip, &sn->sn_head, i_nextsnap) {
vp = ITOV(ip);
/*
@ -2029,14 +2028,6 @@ ffs_copyonwrite(devvp, bp)
if (lbn < NDADDR) {
blkno = DIP(ip, i_db[lbn]);
} else {
if (snapshot_locked == 0 &&
lockmgr(vp->v_vnlock,
LK_INTERLOCK | LK_EXCLUSIVE | LK_SLEEPFAIL,
VI_MTX(devvp), td) != 0) {
VI_LOCK(devvp);
goto retry;
}
snapshot_locked = 1;
td->td_pflags |= TDP_COWINPROGRESS | TDP_NORUNNINGBUF;
error = UFS_BALLOC(vp, lblktosize(fs, (off_t)lbn),
fs->fs_bsize, KERNCRED, BA_METAONLY, &ibp);
@ -2066,14 +2057,6 @@ ffs_copyonwrite(devvp, bp)
* lock, we ensure that we will never be in competition
* with another process to allocate a block.
*/
if (snapshot_locked == 0 &&
lockmgr(vp->v_vnlock,
LK_INTERLOCK | LK_EXCLUSIVE | LK_SLEEPFAIL,
VI_MTX(devvp), td) != 0) {
VI_LOCK(devvp);
goto retry;
}
snapshot_locked = 1;
td->td_pflags |= TDP_COWINPROGRESS | TDP_NORUNNINGBUF;
error = UFS_BALLOC(vp, lblktosize(fs, (off_t)lbn),
fs->fs_bsize, KERNCRED, 0, &cbp);
@ -2135,12 +2118,9 @@ ffs_copyonwrite(devvp, bp)
else
launched_async_io = 1;
}
if (snapshot_locked) {
lockmgr(vp->v_vnlock, LK_RELEASE, NULL, td);
td->td_pflags = (td->td_pflags & ~TDP_NORUNNINGBUF) |
prev_norunningbuf;
} else
VI_UNLOCK(devvp);
lockmgr(vp->v_vnlock, LK_RELEASE, NULL, td);
td->td_pflags = (td->td_pflags & ~TDP_NORUNNINGBUF) |
prev_norunningbuf;
if (launched_async_io && (td->td_pflags & TDP_NORUNNINGBUF) == 0)
waitrunningbufspace();
/*