Patch "Btrfs: return gracefully from balance if fs tree is corrupted" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

Btrfs: return gracefully from balance if fs tree is corrupted

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
btrfs-return-gracefully-from-balance-if-fs-tree-is-corrupted.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Liu Bo <[email protected]>
Date: Wed, 14 Sep 2016 08:51:46 -0700
Subject: Btrfs: return gracefully from balance if fs tree is corrupted

From: Liu Bo <[email protected]>

commit 3561b9db70928f207be4570b48fc19898eeaef54 upstream.

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.

---
 fs/btrfs/relocation.c |   23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

@@ -921,9 +921,16 @@ 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++) {

@@ -2676,11 +2683,15 @@ static int do_relocation(struct btrfs_tr
 
 		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];

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/btrfs-fix-memory-leak-in-reading-btree-blocks.patch queue-4.4/btrfs-bail-out-if-block-group-has-different-mixed-flag.patch queue-4.4/btrfs-return-gracefully-from-balance-if-fs-tree-is-corrupted.patch queue-4.4/btrfs-don-t-bug-during-drop-snapshot.patch queue-4.4/btrfs-fix-memory-leak-in-do_walk_down.patch