btrfs: add mount option for ref_tracker

The ref_tracker infrastructure aids debugging but is not enabled by
default as it has a performance impact. Add mount option 'ref_tracker'
so it can be selectively enabled on a filesystem. Currently it track
references of 'delayed inodes'.

Signed-off-by: Leo Martins <[email protected]>
Reviewed-by: David Sterba <[email protected]>
Signed-off-by: David Sterba <[email protected]>

Author: loemraw

fs/btrfs/delayed-inode.h

@@ -198,18 +198,27 @@ void btrfs_assert_delayed_root_empty(struct btrfs_fs_info *fs_info);
 #ifdef CONFIG_BTRFS_DEBUG
 static inline void btrfs_delayed_node_ref_tracker_dir_init(struct btrfs_delayed_node *node)
 {
+	if (!btrfs_test_opt(node->root->fs_info, REF_TRACKER))
+		return;
+
 	ref_tracker_dir_init(&node->ref_dir.dir,
 			     BTRFS_DELAYED_NODE_REF_TRACKER_QUARANTINE_COUNT,
 			     "delayed_node");
 }
 
 static inline void btrfs_delayed_node_ref_tracker_dir_exit(struct btrfs_delayed_node *node)
 {
+	if (!btrfs_test_opt(node->root->fs_info, REF_TRACKER))
+		return;
+
 	ref_tracker_dir_exit(&node->ref_dir.dir);
 }
 
 static inline void btrfs_delayed_node_ref_tracker_dir_print(struct btrfs_delayed_node *node)
 {
+	if (!btrfs_test_opt(node->root->fs_info, REF_TRACKER))
+		return;
+
 	ref_tracker_dir_print(&node->ref_dir.dir,
 			      BTRFS_DELAYED_NODE_REF_TRACKER_DISPLAY_LIMIT);
 }
@@ -218,12 +227,18 @@ static inline int btrfs_delayed_node_ref_tracker_alloc(struct btrfs_delayed_node
 						       struct btrfs_ref_tracker *tracker,
 						       gfp_t gfp)
 {
+	if (!btrfs_test_opt(node->root->fs_info, REF_TRACKER))
+		return 0;
+
 	return ref_tracker_alloc(&node->ref_dir.dir, &tracker->tracker, gfp);
 }
 
 static inline int btrfs_delayed_node_ref_tracker_free(struct btrfs_delayed_node *node,
 						      struct btrfs_ref_tracker *tracker)
 {
+	if (!btrfs_test_opt(node->root->fs_info, REF_TRACKER))
+		return 0;
+
 	return ref_tracker_free(&node->ref_dir.dir, &tracker->tracker);
 }
 #else

fs/btrfs/fs.h

@@ -245,6 +245,7 @@ enum {
 	BTRFS_MOUNT_NOSPACECACHE		= (1ULL << 30),
 	BTRFS_MOUNT_IGNOREMETACSUMS		= (1ULL << 31),
 	BTRFS_MOUNT_IGNORESUPERFLAGS		= (1ULL << 32),
+	BTRFS_MOUNT_REF_TRACKER			= (1ULL << 33),
 };
 
 /*

fs/btrfs/super.c

@@ -134,6 +134,7 @@ enum {
 #ifdef CONFIG_BTRFS_DEBUG
 	Opt_fragment, Opt_fragment_data, Opt_fragment_metadata, Opt_fragment_all,
 	Opt_ref_verify,
+	Opt_ref_tracker,
 #endif
 	Opt_err,
 };
@@ -255,6 +256,7 @@ static const struct fs_parameter_spec btrfs_fs_parameters[] = {
 	fsparam_flag_no("enospc_debug", Opt_enospc_debug),
 #ifdef CONFIG_BTRFS_DEBUG
 	fsparam_enum("fragment", Opt_fragment, btrfs_parameter_fragment),
+	fsparam_flag("ref_tracker", Opt_ref_tracker),
 	fsparam_flag("ref_verify", Opt_ref_verify),
 #endif
 	{}
@@ -631,6 +633,9 @@ static int btrfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
 	case Opt_ref_verify:
 		btrfs_set_opt(ctx->mount_opt, REF_VERIFY);
 		break;
+	case Opt_ref_tracker:
+		btrfs_set_opt(ctx->mount_opt, REF_TRACKER);
+		break;
 #endif
 	default:
 		btrfs_err(NULL, "unrecognized mount option '%s'", param->key);
@@ -1136,6 +1141,8 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
 #endif
 	if (btrfs_test_opt(info, REF_VERIFY))
 		seq_puts(seq, ",ref_verify");
+	if (btrfs_test_opt(info, REF_TRACKER))
+		seq_puts(seq, ",ref_tracker");
 	seq_printf(seq, ",subvolid=%llu", btrfs_root_id(BTRFS_I(d_inode(dentry))->root));
 	subvol_name = btrfs_get_subvol_name_from_objectid(info,
 			btrfs_root_id(BTRFS_I(d_inode(dentry))->root));