[PATCH 3.16 086/125] Btrfs: read lock extent buffer while walking backrefs

Greg Kroah-Hartman
2014-09-03T22:18:57Z

From: Filipe Manana <fdmanana@suse.com>

commit 6f7ff6d7832c6be13e8c95598884dbc40ad69fb7 upstream.

Before processing the extent buffer, acquire a read lock on it, so
that we're safe against concurrent updates on the extent buffer.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/btrfs/backref.c | 3 +++
1 file changed, 3 insertions(+)

--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -1000,8 +1000,11 @@ again:
ret = -EIO;
goto out;
}
+ btrfs_tree_read_lock(eb);
+ btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
ret = find_extent_in_eb(eb, bytenr,
*extent_item_pos, &eie);
+ btrfs_tree_read_unlock_blocking(eb);
free_extent_buffer(eb);
if (ret < 0)
goto out;