From: Josef Bacik <josef@toxicpanda.com>
Date: Fri, 12 Mar 2021 15:25:31 -0500
Subject: btrfs: cleanup error handling in prepare_to_merge
Git-commit: e0b085b0b03fa5c435b7240668f144199ed989c4
Patch-mainline: v5.13-rc1
References: bsc#1187833

This probably can't happen even with a corrupt file system, because we
would have failed much earlier on than here.  However there's no reason
we can't just check and bail out as appropriate, so do that and convert
the correctness BUG_ON() to an ASSERT().

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ add comment ]
Signed-off-by: David Sterba <dsterba@suse.com>
Acked-by: Nikolay Borisov <nborisov@suse.com>
---
 fs/btrfs/relocation.c |   14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -2565,8 +2565,18 @@ again:
 		list_del_init(&reloc_root->root_list);
 
 		root = read_fs_root(fs_info, reloc_root->root_key.offset);
-		BUG_ON(IS_ERR(root));
-		BUG_ON(root->reloc_root != reloc_root);
+		if (IS_ERR(root)) {
+			/*
+			 * Even if we have an error we need this reloc root
+			 * back on our list so we can clean up properly.
+			 */
+			list_add(&reloc_root->root_list, &reloc_roots);
+			btrfs_abort_transaction(trans, (int)PTR_ERR(root));
+			if (!err)
+				err = PTR_ERR(root);
+			break;
+		}
+		ASSERT(root->reloc_root == reloc_root);
 
 		/*
 		 * set reference count to 1, so btrfs_recover_relocation