linux-kernel - [PATCH 6.7 642/713] io_uring: don't save/restore iowait state

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Date: Sun, 24 Mar 2024 18:46:08 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Jens Axboe <axboe@...nel.dk>,
	Sasha Levin <sashal@...nel.org>
Subject: [PATCH 6.7 642/713] io_uring: don't save/restore iowait state

From: Jens Axboe <axboe@...nel.dk>

[ Upstream commit 6f0974eccbf78baead1735722c4f1ee3eb9422cd ]

This kind of state is per-syscall, and since we're doing the waiting off
entering the io_uring_enter(2) syscall, there's no way that iowait can
already be set for this case. Simplify it by setting it if we need to,
and always clearing it to 0 when done.

Fixes: 7b72d661f1f2 ("io_uring: gate iowait schedule on having pending requests")
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 io_uring/io_uring.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index b658ba6703cc2..205dad9603733 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -2508,7 +2508,7 @@ static bool current_pending_io(void)
 static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx,
 					  struct io_wait_queue *iowq)
 {
-	int io_wait, ret;
+	int ret;
 
 	if (unlikely(READ_ONCE(ctx->check_cq)))
 		return 1;
@@ -2526,7 +2526,6 @@ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx,
 	 * can take into account that the task is waiting for IO - turns out
 	 * to be important for low QD IO.
 	 */
-	io_wait = current->in_iowait;
 	if (current_pending_io())
 		current->in_iowait = 1;
 	ret = 0;
@@ -2534,7 +2533,7 @@ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx,
 		schedule();
 	else if (!schedule_hrtimeout(&iowq->timeout, HRTIMER_MODE_ABS))
 		ret = -ETIME;
-	current->in_iowait = io_wait;
+	current->in_iowait = 0;
 	return ret;
 }
 
-- 
2.43.0