btrfs: do not handle non-shareable roots in backref cache

Now that we handle relocation for non-shareable roots without using the
backref cache, remove the ->cowonly field from the backref nodes and
update the handling to throw an error.

Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

3 files changed, 24 insertions, 30 deletions

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index f686f01cdd9b..2e0e36487b33 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -3314,8 +3314,12 @@ static int handle_indirect_tree_backref(struct btrfs_trans_handle *trans,
 	root = btrfs_get_fs_root(fs_info, ref_key->offset, false);
 	if (IS_ERR(root))
 		return PTR_ERR(root);
-	if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
-		cur->cowonly = 1;
+
+	/* We shouldn't be using backref cache for non-shareable roots. */
+	if (unlikely(!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))) {
+		btrfs_put_root(root);
+		return -EUCLEAN;
+	}
 
 	if (btrfs_root_level(&root->root_item) == cur->level) {
 		/* Tree root */
@@ -3401,8 +3405,15 @@ static int handle_indirect_tree_backref(struct btrfs_trans_handle *trans,
 				goto out;
 			}
 			upper->owner = btrfs_header_owner(eb);
-			if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
-				upper->cowonly = 1;
+
+			/* We shouldn't be using backref cache for non shareable roots. */
+			if (unlikely(!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))) {
+				btrfs_put_root(root);
+				btrfs_backref_free_edge(cache, edge);
+				btrfs_backref_free_node(cache, upper);
+				ret = -EUCLEAN;
+				goto out;
+			}
 
 			/*
 			 * If we know the block isn't shared we can avoid
@@ -3593,15 +3604,10 @@ int btrfs_backref_finish_upper_links(struct btrfs_backref_cache *cache,
 
 	ASSERT(start->checked);
 
-	/* Insert this node to cache if it's not COW-only */
-	if (!start->cowonly) {
-		rb_node = rb_simple_insert(&cache->rb_root, start->bytenr,
-					   &start->rb_node);
-		if (rb_node)
-			btrfs_backref_panic(cache->fs_info, start->bytenr,
-					    -EEXIST);
-		list_add_tail(&start->lower, &cache->leaves);
-	}
+	rb_node = rb_simple_insert(&cache->rb_root, start->bytenr, &start->rb_node);
+	if (rb_node)
+		btrfs_backref_panic(cache->fs_info, start->bytenr, -EEXIST);
+	list_add_tail(&start->lower, &cache->leaves);
 
 	/*
 	 * Use breadth first search to iterate all related edges.
@@ -3655,23 +3661,13 @@ int btrfs_backref_finish_upper_links(struct btrfs_backref_cache *cache,
 			return -EUCLEAN;
 		}
 
-		/* Sanity check, COW-only node has non-COW-only parent */
-		if (start->cowonly != upper->cowonly) {
-			ASSERT(0);
+		rb_node = rb_simple_insert(&cache->rb_root, upper->bytenr,
+					   &upper->rb_node);
+		if (unlikely(rb_node)) {
+			btrfs_backref_panic(cache->fs_info, upper->bytenr, -EEXIST);
 			return -EUCLEAN;
 		}
 
-		/* Only cache non-COW-only (subvolume trees) tree blocks */
-		if (!upper->cowonly) {
-			rb_node = rb_simple_insert(&cache->rb_root, upper->bytenr,
-						   &upper->rb_node);
-			if (rb_node) {
-				btrfs_backref_panic(cache->fs_info,
-						upper->bytenr, -EEXIST);
-				return -EUCLEAN;
-			}
-		}
-
 		list_add_tail(&edge->list[UPPER], &upper->lower);
 
 		/*
diff --git a/fs/btrfs/backref.h b/fs/btrfs/backref.h
index 7220bde1fc31..c52bc5f45041 100644
--- a/fs/btrfs/backref.h
+++ b/fs/btrfs/backref.h
@@ -341,8 +341,6 @@ struct btrfs_backref_node {
 	struct extent_buffer *eb;
 	/* Level of the tree block */
 	unsigned int level:8;
-	/* Is the block in a non-shareable tree */
-	unsigned int cowonly:1;
 	/* 1 if no child node is in the cache */
 	unsigned int lowest:1;
 	/* Is the extent buffer locked */
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index c8f35d456a61..fe4e2528c806 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -2542,7 +2542,7 @@ static int relocate_tree_block(struct btrfs_trans_handle *trans,
 		ret = do_relocation(trans, rc, node, key, path, 1);
 	}
 out:
-	if (ret || node->level == 0 || node->cowonly)
+	if (ret || node->level == 0)
 		btrfs_backref_cleanup_node(&rc->backref_cache, node);
 	return ret;
 }