linux-kernel - [PATCH 5.7 434/477] io_uring: reap poll completions while waiting for refs to drop on exit

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Date:   Tue, 23 Jun 2020 21:57:11 +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, Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 5.7 434/477] io_uring: reap poll completions while waiting for refs to drop on exit

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

[ Upstream commit 56952e91acc93ed624fe9da840900defb75f1323 ]

If we're doing polled IO and end up having requests being submitted
async, then completions can come in while we're waiting for refs to
drop. We need to reap these manually, as nobody else will be looking
for them.

Break the wait into 1/20th of a second time waits, and check for done
poll completions if we time out. Otherwise we can have done poll
completions sitting in ctx->poll_list, which needs us to reap them but
we're just waiting for them.

Cc: stable@...r.kernel.org
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/io_uring.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -7404,7 +7404,17 @@ static void io_ring_exit_work(struct wor
 	if (ctx->rings)
 		io_cqring_overflow_flush(ctx, true);
 
-	wait_for_completion(&ctx->completions[0]);
+	/*
+	 * If we're doing polled IO and end up having requests being
+	 * submitted async (out-of-line), then completions can come in while
+	 * we're waiting for refs to drop. We need to reap these manually,
+	 * as nobody else will be looking for them.
+	 */
+	while (!wait_for_completion_timeout(&ctx->completions[0], HZ/20)) {
+		io_iopoll_reap_events(ctx);
+		if (ctx->rings)
+			io_cqring_overflow_flush(ctx, true);
+	}
 	io_ring_ctx_free(ctx);
 }