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Subject[PATCH 5.0 039/146] btrfs: remove WARN_ON in log_dir_items
Date
5.0-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
@@ -3517,9 +3517,16 @@ 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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