Re: [PATCH 1/8] iomap: cleanup up iomap_dio_bio_end_io()

From: "Darrick J. Wong" <djwong@kernel.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: io-uring@vger.kernel.org, linux-xfs@vger.kernel.org, hch@lst.de,
	andres@anarazel.de, david@fromorbit.com
Subject: Re: [PATCH 1/8] iomap: cleanup up iomap_dio_bio_end_io()
Date: Fri, 21 Jul 2023 08:13:40 -0700	[thread overview]
Message-ID: <20230721151340.GK11352@frogsfrogsfrogs> (raw)
In-Reply-To: <20230720181310.71589-2-axboe@kernel.dk>

On Thu, Jul 20, 2023 at 12:13:03PM -0600, Jens Axboe wrote:
> Make the logic a bit easier to follow:
> 
> 1) Add a release_bio out path, as everybody needs to touch that, and
>    have our bio ref check jump there if it's non-zero.
> 2) Add a kiocb local variable.
> 3) Add comments for each of the three conditions (sync, inline, or
>    async workqueue punt).
> 
> No functional changes in this patch.
> 
> Signed-off-by: Jens Axboe <axboe@kernel.dk>

Thanks for deindentifying this,
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
>  fs/iomap/direct-io.c | 46 +++++++++++++++++++++++++++++---------------
>  1 file changed, 31 insertions(+), 15 deletions(-)
> 
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index ea3b868c8355..0ce60e80c901 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -152,27 +152,43 @@ void iomap_dio_bio_end_io(struct bio *bio)
>  {
>  	struct iomap_dio *dio = bio->bi_private;
>  	bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY);
> +	struct kiocb *iocb = dio->iocb;
>  
>  	if (bio->bi_status)
>  		iomap_dio_set_error(dio, blk_status_to_errno(bio->bi_status));
> +	if (!atomic_dec_and_test(&dio->ref))
> +		goto release_bio;
>  
> -	if (atomic_dec_and_test(&dio->ref)) {
> -		if (dio->wait_for_completion) {
> -			struct task_struct *waiter = dio->submit.waiter;
> -			WRITE_ONCE(dio->submit.waiter, NULL);
> -			blk_wake_io_task(waiter);
> -		} else if (dio->flags & IOMAP_DIO_WRITE) {
> -			struct inode *inode = file_inode(dio->iocb->ki_filp);
> -
> -			WRITE_ONCE(dio->iocb->private, NULL);
> -			INIT_WORK(&dio->aio.work, iomap_dio_complete_work);
> -			queue_work(inode->i_sb->s_dio_done_wq, &dio->aio.work);
> -		} else {
> -			WRITE_ONCE(dio->iocb->private, NULL);
> -			iomap_dio_complete_work(&dio->aio.work);
> -		}
> +	/*
> +	 * Synchronous dio, task itself will handle any completion work
> +	 * that needs after IO. All we need to do is wake the task.
> +	 */
> +	if (dio->wait_for_completion) {
> +		struct task_struct *waiter = dio->submit.waiter;
> +
> +		WRITE_ONCE(dio->submit.waiter, NULL);
> +		blk_wake_io_task(waiter);
> +		goto release_bio;
> +	}
> +
> +	/* Read completion can always complete inline. */
> +	if (!(dio->flags & IOMAP_DIO_WRITE)) {
> +		WRITE_ONCE(iocb->private, NULL);
> +		iomap_dio_complete_work(&dio->aio.work);
> +		goto release_bio;
>  	}
>  
> +	/*
> +	 * Async DIO completion that requires filesystem level completion work
> +	 * gets punted to a work queue to complete as the operation may require
> +	 * more IO to be issued to finalise filesystem metadata changes or
> +	 * guarantee data integrity.
> +	 */
> +	WRITE_ONCE(iocb->private, NULL);
> +	INIT_WORK(&dio->aio.work, iomap_dio_complete_work);
> +	queue_work(file_inode(iocb->ki_filp)->i_sb->s_dio_done_wq,
> +			&dio->aio.work);
> +release_bio:
>  	if (should_dirty) {
>  		bio_check_pages_dirty(bio);
>  	} else {
> -- 
> 2.40.1
> 