Re: [PATCH 1/1] iomap: propagate nowait to block layer

["Darrick J. Wong" <djwong@kernel.org>]

On Wed, Feb 26, 2025 at 01:33:58AM +0000, Pavel Begunkov wrote:
> There are reports of high io_uring submission latency for ext4 and xfs,
> which is due to iomap not propagating nowait flag to the block layer
> resulting in waiting for IO during tag allocation.
> 
> Cc: stable@vger.kernel.org
> Link: https://github.com/axboe/liburing/issues/826#issuecomment-2674131870
> Reported-by: wu lei <uwydoc@gmail.com>
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
>  fs/iomap/direct-io.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index b521eb15759e..25c5e87dbd94 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -81,6 +81,9 @@ static void iomap_dio_submit_bio(const struct iomap_iter *iter,
>  		WRITE_ONCE(iocb->private, bio);
>  	}
>  
> +	if (iocb->ki_flags & IOCB_NOWAIT)
> +		bio->bi_opf |= REQ_NOWAIT;

Shouldn't this go in iomap_dio_bio_opflags?

--D

> +
>  	if (dio->dops && dio->dops->submit_io)
>  		dio->dops->submit_io(iter, bio, pos);
>  	else
> -- 
> 2.48.1
>