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    Subject[25/93] freeze_bdev: dont deactivate successfully frozen MS_RDONLY sb
    2.6.32-stable review patch.  If anyone has any objections, please let us know.

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

    From: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>

    commit 4b06e5b9ad8abb20105b2b25e42c509ebe9b2d76 upstream.

    Thanks Thomas and Christoph for testing and review.
    I removed 'smp_wmb()' before up_write from the previous patch,
    since up_write() should have necessary ordering constraints.
    (I.e. the change of s_frozen is visible to others after up_write)
    I'm quite sure the change is harmless but if you are uncomfortable
    with Tested-by/Reviewed-by on the modified patch, please remove them.

    If MS_RDONLY, freeze_bdev should just up_write(s_umount) instead of
    deactivate_locked_super().
    Also, keep sb->s_frozen consistent so that remount can check the frozen state.

    Otherwise a crash reported here can happen:
    http://lkml.org/lkml/2010/1/16/37
    http://lkml.org/lkml/2010/1/28/53

    This patch should be applied for 2.6.32 stable series, too.

    Reviewed-by: Christoph Hellwig <hch@lst.de>
    Tested-by: Thomas Backlund <tmb@mandriva.org>
    Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
    Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    --- a/fs/block_dev.c
    +++ b/fs/block_dev.c
    @@ -246,7 +246,8 @@ struct super_block *freeze_bdev(struct block_device *bdev)
    if (!sb)
    goto out;
    if (sb->s_flags & MS_RDONLY) {
    - deactivate_locked_super(sb);
    + sb->s_frozen = SB_FREEZE_TRANS;
    + up_write(&sb->s_umount);
    mutex_unlock(&bdev->bd_fsfreeze_mutex);
    return sb;
    }
    @@ -307,7 +308,7 @@ int thaw_bdev(struct block_device *bdev, struct super_block *sb)
    BUG_ON(sb->s_bdev != bdev);
    down_write(&sb->s_umount);
    if (sb->s_flags & MS_RDONLY)
    - goto out_deactivate;
    + goto out_unfrozen;

    if (sb->s_op->unfreeze_fs) {
    error = sb->s_op->unfreeze_fs(sb);
    @@ -321,11 +322,11 @@ int thaw_bdev(struct block_device *bdev, struct super_block *sb)
    }
    }

    +out_unfrozen:
    sb->s_frozen = SB_UNFROZEN;
    smp_wmb();
    wake_up(&sb->s_wait_unfrozen);

    -out_deactivate:
    if (sb)
    deactivate_locked_super(sb);
    out_unlock:



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