linux-kernel - [PATCH 1/4] io_uring: fix hanging iopoll in case of -EAGAIN

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Date:   Tue, 23 Jun 2020 01:16:32 +0300
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Jens Axboe <axboe@...nel.dk>, io-uring@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/4] io_uring: fix hanging iopoll in case of -EAGAIN

io_do_iopoll() won't do anything with a request unless
req->iopoll_completed is set. So io_complete_rw_iopoll() has to set
it, otherwise io_do_iopoll() will poll a file again and again even
though the request of interest was completed long ago.

Fixes: bbde017a32b3 ("io_uring: add memory barrier to synchronize
io_kiocb's result and iopoll_completed")
Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
 fs/io_uring.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index c686061c3762..bb0dfc450db5 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2104,10 +2104,8 @@ static void io_complete_rw_iopoll(struct kiocb *kiocb, long res, long res2)
 
 	WRITE_ONCE(req->result, res);
 	/* order with io_poll_complete() checking ->result */
-	if (res != -EAGAIN) {
-		smp_wmb();
-		WRITE_ONCE(req->iopoll_completed, 1);
-	}
+	smp_wmb();
+	WRITE_ONCE(req->iopoll_completed, 1);
 }
 
 /*
-- 
2.24.0