svn commit: r225851 - stable/9/sys/ufs/ffs
Kirk McKusick
mckusick at FreeBSD.org
Wed Sep 28 19:38:48 UTC 2011
Author: mckusick
Date: Wed Sep 28 19:38:47 2011
New Revision: 225851
URL: http://svn.freebsd.org/changeset/base/225851
Log:
MFC r225807:
This update eliminates a lock-order reversal warning discovered
whle tracking down the system hang reported in kern/160662 and
corrected in revision 225806 (MFC'ed as 225850). The LOR is not
the cause of the system hang and indeed cannot cause an actual
deadlock. However, it can be easily eliminated by defering the
acquisition of a buflock until after all the vnode locks have
been acquired.
As journaled soft updates first appeared in 9.0, this will be the
only MFC of this change.
Approved by: re (kib)
Reported by: Hans Ottevanger
PR: kern/160662
Modified:
stable/9/sys/ufs/ffs/ffs_snapshot.c
Modified: stable/9/sys/ufs/ffs/ffs_snapshot.c
==============================================================================
--- stable/9/sys/ufs/ffs/ffs_snapshot.c Wed Sep 28 19:36:21 2011 (r225850)
+++ stable/9/sys/ufs/ffs/ffs_snapshot.c Wed Sep 28 19:38:47 2011 (r225851)
@@ -212,7 +212,7 @@ ffs_snapshot(mp, snapfile)
struct fs *copy_fs = NULL, *fs;
struct thread *td = curthread;
struct inode *ip, *xp;
- struct buf *bp, *nbp, *ibp, *sbp = NULL;
+ struct buf *bp, *nbp, *ibp;
struct nameidata nd;
struct mount *wrtmp;
struct vattr vat;
@@ -460,21 +460,14 @@ restart:
* Grab a copy of the superblock and its summary information.
* We delay writing it until the suspension is released below.
*/
- error = bread(vp, lblkno(fs, fs->fs_sblockloc), fs->fs_bsize,
- KERNCRED, &sbp);
- if (error) {
- brelse(sbp);
- sbp = NULL;
- goto out1;
- }
- loc = blkoff(fs, fs->fs_sblockloc);
- copy_fs = (struct fs *)(sbp->b_data + loc);
+ copy_fs = malloc((u_long)fs->fs_bsize, M_UFSMNT, M_WAITOK);
bcopy(fs, copy_fs, fs->fs_sbsize);
if ((fs->fs_flags & (FS_UNCLEAN | FS_NEEDSFSCK)) == 0)
copy_fs->fs_clean = 1;
size = fs->fs_bsize < SBLOCKSIZE ? fs->fs_bsize : SBLOCKSIZE;
if (fs->fs_sbsize < size)
- bzero(&sbp->b_data[loc + fs->fs_sbsize], size - fs->fs_sbsize);
+ bzero(&((char *)copy_fs)[fs->fs_sbsize],
+ size - fs->fs_sbsize);
size = blkroundup(fs, fs->fs_cssize);
if (fs->fs_contigsumsize > 0)
size += fs->fs_ncg * sizeof(int32_t);
@@ -490,8 +483,8 @@ restart:
len, KERNCRED, &bp)) != 0) {
brelse(bp);
free(copy_fs->fs_csp, M_UFSMNT);
- bawrite(sbp);
- sbp = NULL;
+ free(copy_fs, M_UFSMNT);
+ copy_fs = NULL;
goto out1;
}
bcopy(bp->b_data, space, (u_int)len);
@@ -606,8 +599,8 @@ loop:
vdrop(xvp);
if (error) {
free(copy_fs->fs_csp, M_UFSMNT);
- bawrite(sbp);
- sbp = NULL;
+ free(copy_fs, M_UFSMNT);
+ copy_fs = NULL;
MNT_VNODE_FOREACH_ABORT(mp, mvp);
goto out1;
}
@@ -621,8 +614,8 @@ loop:
error = softdep_journal_lookup(mp, &xvp);
if (error) {
free(copy_fs->fs_csp, M_UFSMNT);
- bawrite(sbp);
- sbp = NULL;
+ free(copy_fs, M_UFSMNT);
+ copy_fs = NULL;
goto out1;
}
xp = VTOI(xvp);
@@ -688,8 +681,8 @@ loop:
VI_UNLOCK(devvp);
ASSERT_VOP_LOCKED(vp, "ffs_snapshot vp");
out1:
- KASSERT((sn != NULL && sbp != NULL && error == 0) ||
- (sn == NULL && sbp == NULL && error != 0),
+ KASSERT((sn != NULL && copy_fs != NULL && error == 0) ||
+ (sn == NULL && copy_fs == NULL && error != 0),
("email phk@ and mckusick@"));
/*
* Resume operation on filesystem.
@@ -703,7 +696,7 @@ out1:
vp->v_mount->mnt_stat.f_mntonname, (long)endtime.tv_sec,
endtime.tv_nsec / 1000000, redo, fs->fs_ncg);
}
- if (sbp == NULL)
+ if (copy_fs == NULL)
goto out;
/*
* Copy allocation information from all the snapshots in
@@ -793,6 +786,15 @@ out1:
space = (char *)space + fs->fs_bsize;
bawrite(nbp);
}
+ error = bread(vp, lblkno(fs, fs->fs_sblockloc), fs->fs_bsize,
+ KERNCRED, &nbp);
+ if (error) {
+ brelse(nbp);
+ } else {
+ loc = blkoff(fs, fs->fs_sblockloc);
+ bcopy((char *)copy_fs, &nbp->b_data[loc], fs->fs_bsize);
+ bawrite(nbp);
+ }
/*
* As this is the newest list, it is the most inclusive, so
* should replace the previous list.
@@ -822,7 +824,8 @@ out1:
vrele(vp); /* Drop extra reference */
done:
free(copy_fs->fs_csp, M_UFSMNT);
- bawrite(sbp);
+ free(copy_fs, M_UFSMNT);
+ copy_fs = NULL;
out:
NDFREE(&nd, NDF_ONLY_PNBUF);
if (saved_nice > 0) {
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