[PATCH 9/9] io-wq: small optimization for __io_worker_busy()

[Hao Xu <haoxu@linux.alibaba.com>]

Let's change the worker state between free/running only when it's
necessary. This can reduce some lock contension.

Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
---
 fs/io-wq.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index 097ea598bfe5..377c3e42a491 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -434,12 +434,11 @@ static void io_wqe_dec_running(struct io_worker *worker)
  */
 static void __io_worker_busy(struct io_wqe *wqe, struct io_worker *worker,
 			     struct io_wq_work *work)
-	__must_hold(wqe->lock)
 {
-	if (worker->flags & IO_WORKER_F_FREE) {
-		worker->flags &= ~IO_WORKER_F_FREE;
-		hlist_nulls_del_init_rcu(&worker->nulls_node);
-	}
+	raw_spin_lock(&wqe->lock);
+	worker->flags &= ~IO_WORKER_F_FREE;
+	hlist_nulls_del_init_rcu(&worker->nulls_node);
+	raw_spin_unlock(&wqe->lock);
 }
 
 /*
@@ -587,13 +586,10 @@ static void io_worker_handle_work(struct io_worker *worker, struct io_wqe_acct *
 		 * clear the stalled flag.
 		 */
 		work = io_get_next_work(acct, worker, needs_lock);
-		if (work) {
-			raw_spin_lock(&wqe->lock);
+		if (work && (worker->flags & IO_WORKER_F_FREE))
 			__io_worker_busy(wqe, worker, work);
-			raw_spin_unlock(&wqe->lock);
-		} else {
+		else if (!work)
 			break;
-		}
 		io_assign_current_work(worker, work);
 		__set_current_state(TASK_RUNNING);
 
-- 
2.24.4