linux-kernel - [PATCH 5.18 460/879] io_uring: avoid io-wq -EAGAIN looping for !IOPOLL

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Date:   Tue,  7 Jun 2022 18:59:38 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Pavel Begunkov <asml.silence@...il.com>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.18 460/879] io_uring: avoid io-wq -EAGAIN looping for !IOPOLL

From: Pavel Begunkov <asml.silence@...il.com>

[ Upstream commit e0deb6a025ae8c850dc8685be39fb27b06c88736 ]

If an opcode handler semi-reliably returns -EAGAIN, io_wq_submit_work()
might continue busily hammer the same handler over and over again, which
is not ideal. The -EAGAIN handling in question was put there only for
IOPOLL, so restrict it to IOPOLL mode only where there is no other
recourse than to retry as we cannot wait.

Fixes: def596e9557c9 ("io_uring: support for IO polling")
Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
Link: https://lore.kernel.org/r/f168b4f24181942f3614dd8ff648221736f572e6.1652433740.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/io_uring.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index e0823f58f795..7272e410d24a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -7327,6 +7327,8 @@ static void io_wq_submit_work(struct io_wq_work *work)
 		 * wait for request slots on the block side.
 		 */
 		if (!needs_poll) {
+			if (!(req->ctx->flags & IORING_SETUP_IOPOLL))
+				break;
 			cond_resched();
 			continue;
 		}
-- 
2.35.1