From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 085D2C2D0E4 for ; Tue, 24 Nov 2020 02:12:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 86BA3206E0 for ; Tue, 24 Nov 2020 02:12:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726765AbgKXCLu (ORCPT ); Mon, 23 Nov 2020 21:11:50 -0500 Received: from out30-44.freemail.mail.aliyun.com ([115.124.30.44]:58975 "EHLO out30-44.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726376AbgKXCLu (ORCPT ); Mon, 23 Nov 2020 21:11:50 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R821e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04420;MF=jefflexu@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0UGN9bKn_1606183905; Received: from admindeMacBook-Pro-2.local(mailfrom:jefflexu@linux.alibaba.com fp:SMTPD_---0UGN9bKn_1606183905) by smtp.aliyun-inc.com(127.0.0.1); Tue, 24 Nov 2020 10:11:45 +0800 Subject: Re: [PATCH v3] iomap: set REQ_NOWAIT according to IOCB_NOWAIT in Direct IO To: Hao Xu , Alexander Viro , Christoph Hellwig Cc: "Darrick J. Wong" , linux-fsdevel@vger.kernel.org, Konstantin Khlebnikov , Joseph Qi References: <1606121126-216843-1-git-send-email-haoxu@linux.alibaba.com> From: JeffleXu Message-ID: <57d7a8d0-a2c3-c4da-eb92-ce51c8881df9@linux.alibaba.com> Date: Tue, 24 Nov 2020 10:11:45 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.12.1 MIME-Version: 1.0 In-Reply-To: <1606121126-216843-1-git-send-email-haoxu@linux.alibaba.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 11/23/20 4:45 PM, Hao Xu wrote: > Currently, IOCB_NOWAIT is ignored in Direct IO, REQ_NOWAIT is only set > when IOCB_HIPRI is set. But REQ_NOWAIT should be set as well when > IOCB_NOWAIT is set. > > Suggested-by: Jeffle Xu > Signed-off-by: Konstantin Khlebnikov > Signed-off-by: Hao Xu > --- > > Hi all, > I tested fio io_uring direct read for a file on ext4 filesystem on a > nvme ssd. I found that IOCB_NOWAIT is ignored in iomap layer, which > means REQ_NOWAIT is not set in bio->bi_opf. This makes nowait IO a > normal IO. Since I'm new to iomap and block layer, I sincerely ask > yours opinions in case I misunderstand the code which is very likely > to happen.:) > > I found that Konstantin found this issue before in May > 2020 (https://www.spinics.net/lists/linux-block/msg53275.html), here add > his signature, add Jeffle's as well since he gave me some help. > > v1->v2: > * add same logic in __blkdev_direct_IO_simple() > v2->v3: > * add same logic in do_blockdev_direct_IO() > > fs/block_dev.c | 7 +++++++ > fs/direct-io.c | 6 ++++-- > fs/iomap/direct-io.c | 3 +++ > 3 files changed, 14 insertions(+), 2 deletions(-) > > diff --git a/fs/block_dev.c b/fs/block_dev.c > index 9e84b1928b94..f3e9e13a9a9f 100644 > --- a/fs/block_dev.c > +++ b/fs/block_dev.c > @@ -263,6 +263,10 @@ static void blkdev_bio_end_io_simple(struct bio *bio) > bio.bi_opf = dio_bio_write_op(iocb); > task_io_account_write(ret); > } > + > + if (iocb->ki_flags & IOCB_NOWAIT) > + bio.bi_opf |= REQ_NOWAIT; > + > if (iocb->ki_flags & IOCB_HIPRI) > bio_set_polled(&bio, iocb); > > @@ -424,6 +428,9 @@ static void blkdev_bio_end_io(struct bio *bio) > if (!nr_pages) { > bool polled = false; > > + if (iocb->ki_flags & IOCB_NOWAIT) > + bio->bi_opf |= REQ_NOWAIT; > + This should be moved outside the "if (!nr_pages) {}" clause. One direct IO can be split into several bios, among which only the last split bio will get into this conditional clause. Thanks, Jeffle > if (iocb->ki_flags & IOCB_HIPRI) { > bio_set_polled(bio, iocb); > polled = true; > diff --git a/fs/direct-io.c b/fs/direct-io.c > index d53fa92a1ab6..b221ed351c1c 100644 > --- a/fs/direct-io.c > +++ b/fs/direct-io.c > @@ -1206,11 +1206,13 @@ static inline int drop_refcount(struct dio *dio) > if (iov_iter_rw(iter) == WRITE) { > dio->op = REQ_OP_WRITE; > dio->op_flags = REQ_SYNC | REQ_IDLE; > - if (iocb->ki_flags & IOCB_NOWAIT) > - dio->op_flags |= REQ_NOWAIT; > } else { > dio->op = REQ_OP_READ; > } > + > + if (iocb->ki_flags & IOCB_NOWAIT) > + dio->op_flags |= REQ_NOWAIT; > + > if (iocb->ki_flags & IOCB_HIPRI) > dio->op_flags |= REQ_HIPRI; > > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c > index 933f234d5bec..2e897688ed6d 100644 > --- a/fs/iomap/direct-io.c > +++ b/fs/iomap/direct-io.c > @@ -64,6 +64,9 @@ static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap *iomap, > { > atomic_inc(&dio->ref); > > + if (dio->iocb->ki_flags & IOCB_NOWAIT) > + bio->bi_opf |= REQ_NOWAIT; > + > if (dio->iocb->ki_flags & IOCB_HIPRI) > bio_set_polled(bio, dio->iocb); > -- Thanks, Jeffle