From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it1-f196.google.com ([209.85.166.196]:38795 "EHLO mail-it1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727013AbeLAEG4 (ORCPT ); Fri, 30 Nov 2018 23:06:56 -0500 Received: by mail-it1-f196.google.com with SMTP id h65so10225656ith.3 for ; Fri, 30 Nov 2018 08:57:01 -0800 (PST) From: Jens Axboe To: linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-aio@kvack.org Cc: hch@lst.de, Jens Axboe Subject: [PATCH 07/27] iomap: ensure that async polled IO is marked REQ_NOWAIT Date: Fri, 30 Nov 2018 09:56:26 -0700 Message-Id: <20181130165646.27341-8-axboe@kernel.dk> In-Reply-To: <20181130165646.27341-1-axboe@kernel.dk> References: <20181130165646.27341-1-axboe@kernel.dk> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: We can't wait for polled events to complete, as they may require active polling from whoever submitted it. If that is the same task that is submitting new IO, we could deadlock waiting for IO to complete that this task is supposed to be completing itself. Signed-off-by: Jens Axboe --- fs/iomap.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/fs/iomap.c b/fs/iomap.c index 16787b3b09fd..96d60b9b2bea 100644 --- a/fs/iomap.c +++ b/fs/iomap.c @@ -1451,8 +1451,16 @@ static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap *iomap, { atomic_inc(&dio->ref); - if (dio->iocb->ki_flags & IOCB_HIPRI) + if (dio->iocb->ki_flags & IOCB_HIPRI) { bio->bi_opf |= REQ_HIPRI; + /* + * For async polled IO, we can't wait for requests to + * complete, as they may also be polled and require active + * reaping. + */ + if (!dio->wait_for_completion) + bio->bi_opf |= REQ_NOWAIT; + } dio->submit.last_queue = bdev_get_queue(iomap->bdev); dio->submit.cookie = submit_bio(bio); -- 2.17.1