btrfs: add a leak check for roots

Now that we're going to start relying on getting ref counting right for
roots, add a list to track allocated roots and print out any roots that
aren't freed up at free_fs_info time.

Hide this behind CONFIG_BTRFS_DEBUG because this will just be used for
developers to verify they aren't breaking things.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -947,6 +947,7 @@ struct btrfs_fs_info {
 #ifdef CONFIG_BTRFS_DEBUG
 	struct kobject *debug_kobj;
 	struct kobject *discard_debug_kobj;
+	struct list_head allocated_roots;
 #endif
 };
 
@@ -1149,6 +1150,10 @@ struct btrfs_root {
 #ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
 	u64 alloc_bytenr;
 #endif
+
+#ifdef CONFIG_BTRFS_DEBUG
+	struct list_head leak_list;
+#endif
 };
 
 struct btrfs_clone_extent_info {

fs/btrfs/disk-io.c

@@ -1202,6 +1202,12 @@ static void __setup_root(struct btrfs_root *root, struct btrfs_fs_info *fs_info,
 
 	spin_lock_init(&root->root_item_lock);
 	btrfs_qgroup_init_swapped_blocks(&root->swapped_blocks);
+#ifdef CONFIG_BTRFS_DEBUG
+	INIT_LIST_HEAD(&root->leak_list);
+	spin_lock(&fs_info->fs_roots_radix_lock);
+	list_add_tail(&root->leak_list, &fs_info->allocated_roots);
+	spin_unlock(&fs_info->fs_roots_radix_lock);
+#endif
 }
 
 static struct btrfs_root *btrfs_alloc_root(struct btrfs_fs_info *fs_info,
@@ -1531,6 +1537,24 @@ int btrfs_insert_fs_root(struct btrfs_fs_info *fs_info,
 	return ret;
 }
 
+void btrfs_check_leaked_roots(struct btrfs_fs_info *fs_info)
+{
+#ifdef CONFIG_BTRFS_DEBUG
+	struct btrfs_root *root;
+
+	while (!list_empty(&fs_info->allocated_roots)) {
+		root = list_first_entry(&fs_info->allocated_roots,
+					struct btrfs_root, leak_list);
+		btrfs_err(fs_info, "leaked root %llu-%llu refcount %d",
+			  root->root_key.objectid, root->root_key.offset,
+			  refcount_read(&root->refs));
+		while (refcount_read(&root->refs) > 1)
+			btrfs_put_fs_root(root);
+		btrfs_put_fs_root(root);
+	}
+#endif
+}
+
 void btrfs_free_fs_info(struct btrfs_fs_info *fs_info)
 {
 	percpu_counter_destroy(&fs_info->dirty_metadata_bytes);
@@ -1551,6 +1575,7 @@ void btrfs_free_fs_info(struct btrfs_fs_info *fs_info)
 	btrfs_put_fs_root(fs_info->uuid_root);
 	btrfs_put_fs_root(fs_info->free_space_root);
 	btrfs_put_fs_root(fs_info->fs_root);
+	btrfs_check_leaked_roots(fs_info);
 	kfree(fs_info->super_copy);
 	kfree(fs_info->super_for_commit);
 	kvfree(fs_info);
@@ -2677,6 +2702,9 @@ void btrfs_init_fs_info(struct btrfs_fs_info *fs_info)
 	INIT_LIST_HEAD(&fs_info->space_info);
 	INIT_LIST_HEAD(&fs_info->tree_mod_seq_list);
 	INIT_LIST_HEAD(&fs_info->unused_bgs);
+#ifdef CONFIG_BTRFS_DEBUG
+	INIT_LIST_HEAD(&fs_info->allocated_roots);
+#endif
 	extent_map_tree_init(&fs_info->mapping_tree);
 	btrfs_init_block_rsv(&fs_info->global_block_rsv,
 			     BTRFS_BLOCK_RSV_GLOBAL);

fs/btrfs/disk-io.h

@@ -39,6 +39,7 @@ static inline u64 btrfs_sb_offset(int mirror)
 struct btrfs_device;
 struct btrfs_fs_devices;
 
+void btrfs_check_leaked_roots(struct btrfs_fs_info *fs_info);
 void btrfs_init_fs_info(struct btrfs_fs_info *fs_info);
 int btrfs_verify_level_key(struct extent_buffer *eb, int level,
 			   struct btrfs_key *first_key, u64 parent_transid);
@@ -101,8 +102,14 @@ static inline void btrfs_put_fs_root(struct btrfs_root *root)
 {
 	if (!root)
 		return;
-	if (refcount_dec_and_test(&root->refs))
+	if (refcount_dec_and_test(&root->refs)) {
+#ifdef CONFIG_BTRFS_DEBUG
+		spin_lock(&root->fs_info->fs_roots_radix_lock);
+		list_del_init(&root->leak_list);
+		spin_unlock(&root->fs_info->fs_roots_radix_lock);
+#endif
 		kfree(root);
+	}
 }
 
 void btrfs_mark_buffer_dirty(struct extent_buffer *buf);

fs/btrfs/tests/btrfs-tests.c

@@ -193,6 +193,7 @@ void btrfs_free_dummy_fs_info(struct btrfs_fs_info *fs_info)
 	btrfs_free_fs_roots(fs_info);
 	cleanup_srcu_struct(&fs_info->subvol_srcu);
 	kfree(fs_info->super_copy);
+	btrfs_check_leaked_roots(fs_info);
 	kfree(fs_info->fs_devices);
 	kfree(fs_info);
 }