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    Subject[67/67] ext4: fix freeze deadlock under IO
    2.6.35-stable review patch.  If anyone has any objections, please let us know.

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

    From: Eric Sandeen <sandeen@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@cfl.rr.com>
    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 | 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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