[PATCH v8 06/39] btrfs: do proper error handling in record_reloc_root_in_trans

[Josef Bacik]

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 <jo...@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 b70a666612a7..28d49b14a23a 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