From: Pavel Begunkov <asml.silence@gmail.com>
To: Hao Xu <haoxu@linux.alibaba.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Christoph Hellwig <hch@infradead.org>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>,
linux-fsdevel@vger.kernel.org,
Jeffle Xu <jefflexu@linux.alibaba.com>,
Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
Jens Axboe <axboe@kernel.dk>,
io-uring@vger.kernel.org, Joseph Qi <joseph.qi@linux.alibaba.com>,
linux-block@vger.kernel.org
Subject: Re: [PATCH v3 RESEND] iomap: set REQ_NOWAIT according to IOCB_NOWAIT in Direct IO
Date: Fri, 4 Dec 2020 11:44:10 +0000 [thread overview]
Message-ID: <e1faa714-7cb5-977f-1a87-5244adebe90d@gmail.com> (raw)
In-Reply-To: <1607075096-94235-1-git-send-email-haoxu@linux.alibaba.com>
On 04/12/2020 09:44, 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.
I believe Jens took my patch fixing that for blkdev_direct_IO*()
(but not iomap) a while ago.
BTW, even though get_maintainer.pl doesn't think so, AFAIK
fs/block_dev.c is managed by linux-block@vger.kernel.org. Please CC it
next time.
> Suggested-by: Jeffle Xu <jefflexu@linux.alibaba.com>
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
> Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
> ---
>
> 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.:)
> The example I use: io_uring direct randread, the first try is with
> IOCB_NOWAIT but not IOCB_HIPRI, the IOCB_NOWAIT is ignored in block
> layer which I think is not the designed behaviour.
>
> 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..ca6f365c2f14 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);
>
> @@ -417,6 +421,9 @@ static void blkdev_bio_end_io(struct bio *bio)
> task_io_account_write(bio->bi_iter.bi_size);
> }
>
> + if (iocb->ki_flags & IOCB_NOWAIT)
> + bio->bi_opf |= REQ_NOWAIT;
> +
> dio->size += bio->bi_iter.bi_size;
> pos += bio->bi_iter.bi_size;
>
> 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);
>
>
--
Pavel Begunkov
next prev parent reply other threads:[~2020-12-04 11:48 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-04 9:44 [PATCH v3 RESEND] iomap: set REQ_NOWAIT according to IOCB_NOWAIT in Direct IO Hao Xu
2020-12-04 11:44 ` Pavel Begunkov [this message]
2020-12-07 2:21 ` Dave Chinner
2020-12-07 23:40 ` Jens Axboe
2020-12-09 21:15 ` Dave Chinner
2020-12-10 2:33 ` JeffleXu
2020-12-08 5:46 ` JeffleXu
2020-12-09 21:23 ` Dave Chinner
2020-12-10 1:55 ` JeffleXu
2020-12-10 5:18 ` Dave Chinner
2020-12-11 2:50 ` JeffleXu
2020-12-14 2:56 ` Dave Chinner
2020-12-15 9:43 ` JeffleXu
2021-04-02 14:32 ` Pavel Begunkov
2021-04-02 16:26 ` Jens Axboe
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