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Further fixes for deadlock in the presence of multiple snapshots.

Browse source 
There are still more to find, but this fix should cover the
common cases that folks are hitting.
This commit is contained in:
Kirk McKusick 2001-05-14 17:16:49 +00:00
parent 1d7d62d1e0
commit 7389126d9a
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=76580
1 changed files with 20 additions and 7 deletions
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27
sys/ufs/ffs/ffs_snapshot.c
View file

@ -73,8 +73,18 @@ static int mapacct __P((struct vnode *, ufs_daddr_t *, ufs_daddr_t *,
static int ffs_copyonwrite __P((struct vnode *, struct buf *));
static int readblock __P((struct buf *, daddr_t));
/*
* To ensure the consistency of snapshots across crashes, we must
* synchronously write out copied blocks before allowing the
* originals to be modified. Because of the rather severe speed
* penalty that this imposes, the following flag allows this
* crash persistence to be disabled.
*/
int dopersistence = 0;
#ifdef DEBUG
#include <sys/sysctl.h>
SYSCTL_INT(_debug, OID_AUTO, dopersistence, CTLFLAG_RW, &dopersistence, 0, "");
int snapdebug = 0;
SYSCTL_INT(_debug, OID_AUTO, snapdebug, CTLFLAG_RW, &snapdebug, 0, "");
#endif /* DEBUG */
@ -955,7 +965,7 @@ ffs_snapblkfree(freeip, bno, size)
if (savedcbp != 0) {
bcopy(savedcbp->b_data, cbp->b_data, fs->fs_bsize);
bawrite(cbp);
if (ip->i_effnlink > 0)
if (dopersistence && ip->i_effnlink > 0)
(void) VOP_FSYNC(vp, KERNCRED, MNT_WAIT, p);
VOP_UNLOCK(vp, 0, p);
continue;
@ -966,7 +976,7 @@ ffs_snapblkfree(freeip, bno, size)
if ((error = readblock(cbp, lbn)) != 0) {
bzero(cbp->b_data, fs->fs_bsize);
bawrite(cbp);
if (ip->i_effnlink > 0)
if (dopersistence && ip->i_effnlink > 0)
(void) VOP_FSYNC(vp, KERNCRED, MNT_WAIT, p);
VOP_UNLOCK(vp, 0, p);
break;
@ -982,7 +992,7 @@ ffs_snapblkfree(freeip, bno, size)
if (savedcbp) {
vp = savedcbp->b_vp;
bawrite(savedcbp);
if (VTOI(vp)->i_effnlink > 0) {
if (dopersistence && VTOI(vp)->i_effnlink > 0) {
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
(void) VOP_FSYNC(vp, KERNCRED, MNT_WAIT, p);
VOP_UNLOCK(vp, 0, p);
@ -1172,7 +1182,7 @@ ffs_copyonwrite(devvp, bp)
if (savedcbp != 0) {
bcopy(savedcbp->b_data, cbp->b_data, fs->fs_bsize);
bawrite(cbp);
if (ip->i_effnlink > 0)
if (dopersistence && ip->i_effnlink > 0)
(void) VOP_FSYNC(vp, KERNCRED, MNT_WAIT, p);
VOP_UNLOCK(vp, 0, p);
continue;
@ -1183,12 +1193,13 @@ ffs_copyonwrite(devvp, bp)
if ((error = readblock(cbp, lbn)) != 0) {
bzero(cbp->b_data, fs->fs_bsize);
bawrite(cbp);
if (ip->i_effnlink > 0)
if (dopersistence && ip->i_effnlink > 0)
(void) VOP_FSYNC(vp, KERNCRED, MNT_WAIT, p);
VOP_UNLOCK(vp, 0, p);
break;
}
savedcbp = cbp;
VOP_UNLOCK(vp, 0, p);
}
/*
* Note that we need to synchronously write snapshots that
@ -1198,9 +1209,11 @@ ffs_copyonwrite(devvp, bp)
if (savedcbp) {
vp = savedcbp->b_vp;
bawrite(savedcbp);
if (VTOI(vp)->i_effnlink > 0)
if (dopersistence && VTOI(vp)->i_effnlink > 0) {
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
(void) VOP_FSYNC(vp, KERNCRED, MNT_WAIT, p);
VOP_UNLOCK(vp, 0, p);
VOP_UNLOCK(vp, 0, p);
}
}
return (error);
}