bcachefs: add time_stats for btree_node_read_done()

Seeing weird latency issues in the btree node read path - add one
bch2_btree_node_read_done().
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/bcachefs.h

@@ -425,6 +425,7 @@ BCH_DEBUG_PARAMS_DEBUG()
 	x(btree_node_merge)			\
 	x(btree_node_sort)			\
 	x(btree_node_read)			\
+	x(btree_node_read_done)			\
 	x(btree_interior_update_foreground)	\
 	x(btree_interior_update_total)		\
 	x(btree_gc)				\

fs/bcachefs/btree_io.c

@@ -942,6 +942,7 @@ int bch2_btree_node_read_done(struct bch_fs *c, struct bch_dev *ca,
 	unsigned ptr_written = btree_ptr_sectors_written(&b->key);
 	struct printbuf buf = PRINTBUF;
 	int ret = 0, retry_read = 0, write = READ;
+	u64 start_time = local_clock();
 
 	b->version_ondisk = U16_MAX;
 	/* We might get called multiple times on read retry: */
@@ -1209,6 +1210,7 @@ int bch2_btree_node_read_done(struct bch_fs *c, struct bch_dev *ca,
 out:
 	mempool_free(iter, &c->fill_iter);
 	printbuf_exit(&buf);
+	bch2_time_stats_update(&c->times[BCH_TIME_btree_node_read_done], start_time);
 	return retry_read;
 fsck_err:
 	if (ret == -BCH_ERR_btree_node_read_err_want_retry ||