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[5.10,4/5] io_uring: fix io_cqring_events()'s noflush

Message ID 018bb0de66981fa798da015a983e5bb6c41bae5b.1607293068.git.asml.silence@gmail.com
State Accepted
Commit 59850d226e4907a6f37c1d2fe5ba97546a8691a4
Headers show
Series [5.10,1/5] io_uring: always let io_iopoll_complete() complete polled io. | expand

Commit Message

Pavel Begunkov Dec. 6, 2020, 10:22 p.m. UTC 
Checking !list_empty(&ctx->cq_overflow_list) around noflush in
io_cqring_events() is racy, because if it fails but a request overflowed
just after that, io_cqring_overflow_flush() still will be called.

Remove the second check, it shouldn't be a problem for performance,
because there is cq_check_overflow bit check just above.

Cc: <stable@vger.kernel.org> # 5.5+
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

diff --git a/fs/io_uring.c b/fs/io_uring.c
index b1ba9a738315..f707caed9f79 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2246,7 +2246,7 @@  static unsigned io_cqring_events(struct io_ring_ctx *ctx, bool noflush)
 		 * we wake up the task, and the next invocation will flush the
 		 * entries. We cannot safely to it from here.
 		 */
-		if (noflush && !list_empty(&ctx->cq_overflow_list))
+		if (noflush)
 			return -1U;
 
 		io_cqring_overflow_flush(ctx, false, NULL, NULL);