linux-kernel - [PATCH 5.11 01/31] io_uring: dont attempt IO reissue from the ring exit path

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Date:   Fri, 19 Mar 2021 13:18:55 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.11 01/31] io_uring: dont attempt IO reissue from the ring exit path

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

[ Upstream commit 7c977a58dc83366e488c217fd88b1469d242bee5 ]

If we're exiting the ring, just let the IO fail with -EAGAIN as nobody
will care anyway. It's not the right context to reissue from.

Cc: stable@...r.kernel.org
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/io_uring.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 00ef0b90d149..68508f010b90 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2717,6 +2717,13 @@ static bool io_rw_reissue(struct io_kiocb *req, long res)
 		return false;
 	if ((res != -EAGAIN && res != -EOPNOTSUPP) || io_wq_current_is_worker())
 		return false;
+	/*
+	 * If ref is dying, we might be running poll reap from the exit work.
+	 * Don't attempt to reissue from that path, just let it fail with
+	 * -EAGAIN.
+	 */
+	if (percpu_ref_is_dying(&req->ctx->refs))
+		return false;
 
 	lockdep_assert_held(&req->ctx->uring_lock);
 
-- 
2.30.1