Re: [PATCH v3 4/9] Introduce IOCB_SWAP kiocb flag to trigger REQ_SWAP

Dave Chinner
2021-09-26T21:56:39Z

On Fri, Sep 24, 2021 at 06:18:32PM +0100, David Howells wrote:
> Introduce an IOCB_SWAP flag for the kiocb struct such that the REQ_SWAP
> will get set on lower level operation structures in generic code.
>
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: Matthew Wilcox <willy@infradead.org>
> cc: Christoph Hellwig <hch@lst.de>
> cc: Darrick J. Wong <djwong@kernel.org>
> cc: linux-xfs@vger.kernel.org
> cc: linux-block@vger.kernel.org
> cc: linux-fsdevel@vger.kernel.org
> cc: linux-mm@kvack.org
> ---
>
> fs/direct-io.c | 2 ++
> include/linux/bio.h | 2 ++
> include/linux/fs.h | 1 +
> 3 files changed, 5 insertions(+)
>
> diff --git a/fs/direct-io.c b/fs/direct-io.c
> index b2e86e739d7a..76eec0a68fa4 100644
> --- a/fs/direct-io.c
> +++ b/fs/direct-io.c
> @@ -1216,6 +1216,8 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
> }
> if (iocb->ki_flags & IOCB_HIPRI)
> dio->op_flags |= REQ_HIPRI;
> + if (iocb->ki_flags & IOCB_SWAP)
> + dio->op_flags |= REQ_SWAP;
>
> /*
> * For AIO O_(D)SYNC writes we need to defer completions to a workqueue
> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index 00952e92eae1..b01133727494 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -787,6 +787,8 @@ static inline void bio_set_polled(struct bio *bio, struct kiocb *kiocb)
> bio->bi_opf |= REQ_HIPRI;
> if (!is_sync_kiocb(kiocb))
> bio->bi_opf |= REQ_NOWAIT;
> + if (kiocb->ki_flags & IOCB_SWAP)
> + bio->bi_opf |= REQ_SWAP;
> }
>
> struct bio *blk_next_bio(struct bio *bio, unsigned int nr_pages, gfp_t gfp);
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index c909ca6c0eb6..c20f4423e2f1 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -321,6 +321,7 @@ enum rw_hint {
> #define IOCB_NOIO (1 << 20)
> /* can use bio alloc cache */
> #define IOCB_ALLOC_CACHE (1 << 21)
> +#define IOCB_SWAP (1 << 22) /* Operation on a swapfile */
>
> struct kiocb {
> struct file *ki_filp;

This doesn't set REQ_SWAP for the iomap based DIO path.
bio_set_polled() is only called from iomap for IOCB_HIPRI IO.

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com