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    Subject[PATCH 4.9 17/56] btrfs: remove WARN_ON in log_dir_items
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

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

    From: Josef Bacik <josef@toxicpanda.com>

    commit 2cc8334270e281815c3850c3adea363c51f21e0d upstream.

    When Filipe added the recursive directory logging stuff in
    2f2ff0ee5e430 ("Btrfs: fix metadata inconsistencies after directory
    fsync") he specifically didn't take the directory i_mutex for the
    children directories that we need to log because of lockdep. This is
    generally fine, but can lead to this WARN_ON() tripping if we happen to
    run delayed deletion's in between our first search and our second search
    of dir_item/dir_indexes for this directory. We expect this to happen,
    so the WARN_ON() isn't necessary. Drop the WARN_ON() and add a comment
    so we know why this case can happen.

    CC: stable@vger.kernel.org # 4.4+
    Reviewed-by: Filipe Manana <fdmanana@suse.com>
    Signed-off-by: Josef Bacik <josef@toxicpanda.com>
    Signed-off-by: David Sterba <dsterba@suse.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/btrfs/tree-log.c | 11 +++++++++--
    1 file changed, 9 insertions(+), 2 deletions(-)

    --- a/fs/btrfs/tree-log.c
    +++ b/fs/btrfs/tree-log.c
    @@ -3343,9 +3343,16 @@ static noinline int log_dir_items(struct
    }
    btrfs_release_path(path);

    - /* find the first key from this transaction again */
    + /*
    + * Find the first key from this transaction again. See the note for
    + * log_new_dir_dentries, if we're logging a directory recursively we
    + * won't be holding its i_mutex, which means we can modify the directory
    + * while we're logging it. If we remove an entry between our first
    + * search and this search we'll not find the key again and can just
    + * bail.
    + */
    ret = btrfs_search_slot(NULL, root, &min_key, path, 0, 0);
    - if (WARN_ON(ret != 0))
    + if (ret != 0)
    goto done;

    /*

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