linux-kernel - [PATCH 5.8 186/255] io_uring: clear req->result on IOPOLL re-issue

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Date:   Tue,  1 Sep 2020 17:10:42 +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, Andres Freund <andres@...razel.de>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 5.8 186/255] io_uring: clear req->result on IOPOLL re-issue

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

commit 56450c20fe10d4d93f58019109aa4e06fc0b9206 upstream.

Make sure we clear req->result, which was set to -EAGAIN for retry
purposes, when moving it to the reissue list. Otherwise we can end up
retrying a request more than once, which leads to weird results in
the io-wq handling (and other spots).

Cc: stable@...r.kernel.org
Reported-by: Andres Freund <andres@...razel.de>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/io_uring.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1810,6 +1810,7 @@ static void io_iopoll_complete(struct io
 
 		req = list_first_entry(done, struct io_kiocb, list);
 		if (READ_ONCE(req->result) == -EAGAIN) {
+			req->result = 0;
 			req->iopoll_completed = 0;
 			list_move_tail(&req->list, &again);
 			continue;