Merge branch 'for-linus-4.5' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs

Pull btrfs fix from Chris Mason:
 "Filipe nailed down a problem where tree log replay would do some work
  that orphan code wasn't expecting to be done yet, leading to BUG_ON"

* 'for-linus-4.5' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs:
  Btrfs: fix loading of orphan roots leading to BUG_ON

1 files changed, 9 insertions, 1 deletions

diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
index 7cf8509deda7..2c849b08a91b 100644
--- a/fs/btrfs/root-tree.c
+++ b/fs/btrfs/root-tree.c
@@ -310,8 +310,16 @@ int btrfs_find_orphan_roots(struct btrfs_root *tree_root)
                 set_bit(BTRFS_ROOT_ORPHAN_ITEM_INSERTED, &root->state);
 
                 err = btrfs_insert_fs_root(root->fs_info, root);
+                /*
+                 * The root might have been inserted already, as before we look
+                 * for orphan roots, log replay might have happened, which
+                 * triggers a transaction commit and qgroup accounting, which
+                 * in turn reads and inserts fs roots while doing backref
+                 * walking.
+                 */
+                if (err == -EEXIST)
+                        err = 0;
                 if (err) {
-                        BUG_ON(err == -EEXIST);
                         btrfs_free_fs_root(root);
                         break;
                 }