[PATCH 5/8] btrfs: tree-checker: don't fail on empty extent roots for extent tree v2

[Josef Bacik <josef@toxicpanda.com>]

For extent tree v2 we can definitely have empty extent roots, so skip
this particular check if we have that set.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/tree-checker.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
index 7733e8ac0a69..1c33dd0e4afc 100644
--- a/fs/btrfs/tree-checker.c
+++ b/fs/btrfs/tree-checker.c
@@ -1633,7 +1633,6 @@ static int check_leaf(struct extent_buffer *leaf, bool check_item_data)
 		/* These trees must never be empty */
 		if (unlikely(owner == BTRFS_ROOT_TREE_OBJECTID ||
 			     owner == BTRFS_CHUNK_TREE_OBJECTID ||
-			     owner == BTRFS_EXTENT_TREE_OBJECTID ||
 			     owner == BTRFS_DEV_TREE_OBJECTID ||
 			     owner == BTRFS_FS_TREE_OBJECTID ||
 			     owner == BTRFS_DATA_RELOC_TREE_OBJECTID)) {
@@ -1642,12 +1641,25 @@ static int check_leaf(struct extent_buffer *leaf, bool check_item_data)
 				    owner);
 			return -EUCLEAN;
 		}
+
 		/* Unknown tree */
 		if (unlikely(owner == 0)) {
 			generic_err(leaf, 0,
 				"invalid owner, root 0 is not defined");
 			return -EUCLEAN;
 		}
+
+		/* EXTENT_TREE_V2 can have empty extent trees. */
+		if (btrfs_fs_incompat(fs_info, EXTENT_TREE_V2))
+			return 0;
+
+		if (unlikely(owner == BTRFS_EXTENT_TREE_OBJECTID)) {
+			generic_err(leaf, 0,
+			"invalid root, root %llu must never be empty",
+				    owner);
+			return -EUCLEAN;
+		}
+
 		return 0;
 	}
 
-- 
2.26.3