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From: Greg KH on 11 Aug 2010 20:20
2.6.35-stable review patch. If anyone has any objections, please let us know.

------------------

From: Eric Sandeen <sandeen(a)sandeen.net>

commit 437f88cc031ffe7f37f3e705367f4fe1f4be8b0f upstream.

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(a)cfl.rr.com>
Signed-off-by: Eric Sandeen <sandeen(a)redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso(a)mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh(a)suse.de>

---
fs/ext4/super.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -241,7 +241,7 @@ 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);
+ 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

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);
}



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