Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | Date | Mon, 02 Aug 2010 14:04:46 +0200 | From | Stefan Bader <> | Subject | Re: [Stable-review] [116/165] ext4: dont return to userspace after freezing the fs with a mutex held |
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We have reports about this patch breaking lvm snapshhots. Eric, there is a patch mentioned which is supposed to fix things but its not upstream, yet. Do you know what happened to that?
-Stefan
PATCH] ext4: fix freeze deadlock under IO
Commit 6b0310fbf087ad6 caused a regression resulting in deadlocks when freezing a filesystem which had active IO; the vfs_check_frozen level (SB_FREEZE_WRITE) did not let the freeze-related IO syncing through. Duh.
Changing the test to FREEZE_TRANS should let the normal freeze syncing get through the fs, but still block any transactions from starting once the fs is completely frozen.
I tested this by running fsstress in the background while periodically snapshotting the fs and running fsck on the result. I ran into occasional deadlocks, but different ones. I think this is a fine fix for the problem at hand, and the other deadlocky things will need more investigation.
Reported-by: Phillip Susi <psusi@cfl.rr.com> Signed-off-by: Eric Sandeen <sandeen@redhat.com> ---
diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 4e8983a..a45ced9 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -241,7 +241,7 @@ handle_t *ext4_journal_start_sb(struct super_block *sb, int nblocks) if (sb->s_flags & MS_RDONLY) return ERR_PTR(-EROFS);
- vfs_check_frozen(sb, SB_FREEZE_WRITE); + vfs_check_frozen(sb, SB_FREEZE_TRANS); /* Special case here: if the journal has aborted behind our * backs (eg. EIO in the commit thread), then we still need to * take the FS itself readonly cleanly. */ @@ -3491,7 +3491,7 @@ int ext4_force_commit(struct super_block *sb)
journal = EXT4_SB(sb)->s_journal; if (journal) { - vfs_check_frozen(sb, SB_FREEZE_WRITE); + vfs_check_frozen(sb, SB_FREEZE_TRANS); ret = ext4_journal_force_commit(journal); }
On 07/30/2010 07:15 PM, Greg KH wrote: > 2.6.32-stable review patch. If anyone has any objections, please let us know. > > ------------------ > > commit 6b0310fbf087ad6e9e3b8392adca97cd77184084 upstream (as of v2.6.34-git13) > > ext4_freeze() used jbd2_journal_lock_updates() which takes > the j_barrier mutex, and then returns to userspace. The > kernel does not like this: > > ================================================ > [ BUG: lock held when returning to user space! ] > ------------------------------------------------ > lvcreate/1075 is leaving the kernel with locks still held! > 1 lock held by lvcreate/1075: > #0: (&journal->j_barrier){+.+...}, at: [<ffffffff811c6214>] > jbd2_journal_lock_updates+0xe1/0xf0 > > Use vfs_check_frozen() added to ext4_journal_start_sb() and > ext4_force_commit() instead. > > Addresses-Red-Hat-Bugzilla: #568503 > > Signed-off-by: Eric Sandeen <sandeen@redhat.com> > Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> > Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> > --- > fs/ext4/super.c | 20 ++++++++++---------- > 1 file changed, 10 insertions(+), 10 deletions(-) > > --- a/fs/ext4/super.c > +++ b/fs/ext4/super.c > @@ -227,6 +227,7 @@ handle_t *ext4_journal_start_sb(struct s > if (sb->s_flags & MS_RDONLY) > return ERR_PTR(-EROFS); > > + vfs_check_frozen(sb, SB_FREEZE_WRITE); > /* Special case here: if the journal has aborted behind our > * backs (eg. EIO in the commit thread), then we still need to > * take the FS itself readonly cleanly. */ > @@ -3391,8 +3392,10 @@ int ext4_force_commit(struct super_block > return 0; > > journal = EXT4_SB(sb)->s_journal; > - if (journal) > + if (journal) { > + vfs_check_frozen(sb, SB_FREEZE_WRITE); > ret = ext4_journal_force_commit(journal); > + } > > return ret; > } > @@ -3441,18 +3444,16 @@ static int ext4_freeze(struct super_bloc > * the journal. > */ > error = jbd2_journal_flush(journal); > - if (error < 0) { > - out: > - jbd2_journal_unlock_updates(journal); > - return error; > - } > + if (error < 0) > + goto out; > > /* Journal blocked and flushed, clear needs_recovery flag. */ > EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER); > error = ext4_commit_super(sb, 1); > - if (error) > - goto out; > - return 0; > +out: > + /* we rely on s_frozen to stop further updates */ > + jbd2_journal_unlock_updates(EXT4_SB(sb)->s_journal); > + return error; > } > > /* > @@ -3469,7 +3470,6 @@ static int ext4_unfreeze(struct super_bl > EXT4_SET_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER); > ext4_commit_super(sb, 1); > unlock_super(sb); > - jbd2_journal_unlock_updates(EXT4_SB(sb)->s_journal); > return 0; > } > > > > _______________________________________________ > Stable-review mailing list > Stable-review@linux.kernel.org > http://linux.kernel.org/mailman/listinfo/stable-review
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