Btrfs: read lock extent buffer while walking backrefs
authorFilipe Manana <fdmanana@suse.com>
Wed, 2 Jul 2014 19:07:54 +0000 (20:07 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Fri, 5 Sep 2014 23:34:16 +0000 (16:34 -0700)
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

index d9328a9..6244f9c 100644 (file)
@@ -984,8 +984,11 @@ 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;