[PATCH v7 06/38] btrfs: do proper error handling in record_reloc_root_in_trans

[Josef Bacik <josef@toxicpanda.com>]

Generally speaking this shouldn't ever fail, the corresponding fs root
for the reloc root will already be in memory, so we won't get -ENOMEM
here.

However if there is no corresponding root for the reloc root then we
could get -ENOMEM when we try to allocate it or we could get -ENOENT
when we look it up and see that it doesn't exist.

Convert these BUG_ON()'s into ASSERT()'s + proper error handling for the
case of corruption.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/relocation.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 1c36b10fdd02..0eea27d9e3cf 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -1971,8 +1971,27 @@ static int record_reloc_root_in_trans(struct btrfs_trans_handle *trans,
 		return 0;
 
 	root = btrfs_get_fs_root(fs_info, reloc_root->root_key.offset, false);
-	BUG_ON(IS_ERR(root));
-	BUG_ON(root->reloc_root != reloc_root);
+
+	/*
+	 * This should succeed, since we can't have a reloc root without having
+	 * already looked up the actual root and created the reloc root for this
+	 * root.
+	 *
+	 * However if there's some sort of corruption where we have a ref to a
+	 * reloc root without a corresponding root this could return -ENOENT.
+	 */
+	if (IS_ERR(root)) {
+		ASSERT(0);
+		return PTR_ERR(root);
+	}
+	if (root->reloc_root != reloc_root) {
+		ASSERT(0);
+		btrfs_err(fs_info,
+			  "root %llu has two reloc roots associated with it",
+			  reloc_root->root_key.offset);
+		btrfs_put_root(root);
+		return -EUCLEAN;
+	}
 	ret = btrfs_record_root_in_trans(trans, root);
 	btrfs_put_root(root);
 
-- 
2.26.2