btrfs: remove NULL transaction support for btrfs_lookup_extent_info()

There are no callers of btrfs_lookup_extent_info() that pass a NULL value
for the transaction handle argument, so there's no point in having special
logic to deal with the NULL. The last caller that passed a NULL value was
removed in commit 19b546d7 ("btrfs: relocation:
Use btrfs_find_all_leafs to locate data extent parent tree leaves").

So remove the NULL handling from btrfs_lookup_extent_info().
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent-tree.c

@@ -126,11 +126,6 @@ int btrfs_lookup_extent_info(struct btrfs_trans_handle *trans,
 	if (!path)
 		return -ENOMEM;
 
-	if (!trans) {
-		path->skip_locking = 1;
-		path->search_commit_root = 1;
-	}
-
 search_again:
 	key.objectid = bytenr;
 	key.offset = offset;
@@ -171,11 +166,7 @@ int btrfs_lookup_extent_info(struct btrfs_trans_handle *trans,
 			btrfs_err(fs_info,
 			"unexpected extent item size, has %u expect >= %zu",
 				  item_size, sizeof(*ei));
-			if (trans)
-				btrfs_abort_transaction(trans, ret);
-			else
-				btrfs_handle_fs_error(fs_info, ret, NULL);
-
+			btrfs_abort_transaction(trans, ret);
 			goto out_free;
 		}
 
@@ -186,9 +177,6 @@ int btrfs_lookup_extent_info(struct btrfs_trans_handle *trans,
 		ret = 0;
 	}
 
-	if (!trans)
-		goto out;
-
 	delayed_refs = &trans->transaction->delayed_refs;
 	spin_lock(&delayed_refs->lock);
 	head = btrfs_find_delayed_ref_head(delayed_refs, bytenr);
@@ -219,7 +207,7 @@ int btrfs_lookup_extent_info(struct btrfs_trans_handle *trans,
 		mutex_unlock(&head->mutex);
 	}
 	spin_unlock(&delayed_refs->lock);
-out:
+
 	WARN_ON(num_refs == 0);
 	if (refs)
 		*refs = num_refs;