From: Josef Bacik <josef@toxicpanda.com>
Date: Fri, 12 Mar 2021 15:24:57 -0500
Subject: btrfs: convert BUG_ON()'s in relocate_tree_block
Git-commit: 1c7bfa159fe796f0f6d310b02215d765f066b9c2
Patch-mainline: v5.13-rc1
References: bsc#1187833

We have a couple of BUG_ON()'s in relocate_tree_block() that can be
tripped if we have file system corruption.  Convert these to ASSERT()'s
so developers still get yelled at when they break the backref code, but
error out nicely for users so the whole box doesn't go down.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Acked-by: Nikolay Borisov <nborisov@suse.com>
---
 fs/btrfs/relocation.c |   24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -3167,8 +3167,28 @@ static int relocate_tree_block(struct bt
 
 	if (root) {
 		if (test_bit(BTRFS_ROOT_REF_COWS, &root->state)) {
-			BUG_ON(node->new_bytenr);
-			BUG_ON(!list_empty(&node->list));
+			/*
+			 * This block was the root block of a root, and this is
+			 * the first time we're processing the block and thus it
+			 * should not have had the ->new_bytenr modified and
+			 * should have not been included on the changed list.
+			 *
+			 * However in the case of corruption we could have
+			 * multiple refs pointing to the same block improperly,
+			 * and thus we would trip over these checks.  ASSERT()
+			 * for the developer case, because it could indicate a
+			 * bug in the backref code, however error out for a
+			 * normal user in the case of corruption.
+			 */
+			ASSERT(node->new_bytenr == 0);
+			ASSERT(list_empty(&node->list));
+			if (node->new_bytenr || !list_empty(&node->list)) {
+				btrfs_err(root->fs_info,
+				  "bytenr %llu has improper references to it",
+					  node->bytenr);
+				ret = -EUCLEAN;
+				goto out;
+			}
 			btrfs_record_root_in_trans(trans, root);
 			root = root->reloc_root;
 			node->new_bytenr = root->node->start;