Btrfs: return gracefully from balance if fs tree is corrupted

Liu Bo · kdave · commit 3561b9db7092 · 2016-09-26T17:59:49.000+02:00
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 &lt;bo.li.liu@oracle.com&gt;
Reviewed-by: Josef Bacik &lt;jbacik@fb.com&gt;
Signed-off-by: David Sterba &lt;dsterba@suse.com&gt;
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
@@ -923,9 +923,16 @@ struct backref_node *build_backref_tree(struct reloc_control *rc,
 			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];
