Btrfs: return gracefully from balance if fs tree is corrupted

When relocating tree blocks, we firstly get block information from
back references in the extent tree, we then search fs tree to try to
find all parents of a block.

However, if fs tree is corrupted, eg. if there're some missing
items, we could come across these WARN_ONs and BUG_ONs.

This makes us print some error messages and return gracefully
from balance.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
(cherry picked from commit ecc3b8e78e181e4769012e2a6ce3294307fdf766)

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 39e25b859808a3f11ab99d4b3ad475f58405f6e5..f1b6eae9a48a5b61f82614cce0ba66a05dbfc123 100644 (file)
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -922,9 +922,16 @@ again:
                        path2->slots[level]--;
 
                eb = path2->nodes[level];
-               WARN_ON(btrfs_node_blockptr(eb, path2->slots[level]) !=
-                       cur->bytenr);
-
+               if (btrfs_node_blockptr(eb, path2->slots[level]) !=
+                   cur->bytenr) {
+                       btrfs_err(root->fs_info,
+       "couldn't find block (%llu) (level %d) in tree (%llu) with key (%llu %u %llu)",
+                                 cur->bytenr, level - 1, root->objectid,
+                                 node_key->objectid, node_key->type,
+                                 node_key->offset);
+                       err = -ENOENT;
+                       goto out;
+               }
                lower = cur;
                need_check = true;
                for (; level < BTRFS_MAX_LEVEL; level++) {
@@ -2686,11 +2693,15 @@ static int do_relocation(struct btrfs_trans_handle *trans,
 
                if (!upper->eb) {
                        ret = btrfs_search_slot(trans, root, key, path, 0, 1);
-                       if (ret < 0) {
-                               err = ret;
+                       if (ret) {
+                               if (ret < 0)
+                                       err = ret;
+                               else
+                                       err = -ENOENT;
+
+                               btrfs_release_path(path);
                                break;
                        }
-                       BUG_ON(ret > 0);
 
                        if (!upper->eb) {
                                upper->eb = path->nodes[upper->level];