On Tue, Jun 07, 2022 at 11:31:35PM +0000, Al Viro wrote:
> New flag, equivalent to removal of IOCB_DSYNC from iocb flags.
> This mimics what btrfs is doing (and that's what btrfs will
> switch to). However, I'm not at all sure that we want to
> suppress REQ_FUA for those - all btrfs hack really cares about
> is suppression of generic_write_sync(). For now let's keep
> the existing behaviour, but I really want to hear more detailed
> arguments pro or contra.
>
> [folded brain fix from willy]
>
> Suggested-by: Christoph Hellwig <hch@xxxxxx>
> Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Looks ok,
Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
--D
> ---
> fs/iomap/direct-io.c | 20 +++++++++++---------
> include/linux/iomap.h | 6 ++++++
> 2 files changed, 17 insertions(+), 9 deletions(-)
>
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index 370c3241618a..c10c69e2de24 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -548,17 +548,19 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
> }
>
> /* for data sync or sync, we need sync completion processing */
> - if (iocb->ki_flags & IOCB_DSYNC)
> + if (iocb->ki_flags & IOCB_DSYNC &&
> + !(dio_flags & IOMAP_DIO_NOSYNC)) {
> dio->flags |= IOMAP_DIO_NEED_SYNC;
>
> - /*
> - * For datasync only writes, we optimistically try using FUA for
> - * this IO. Any non-FUA write that occurs will clear this flag,
> - * hence we know before completion whether a cache flush is
> - * necessary.
> - */
> - if ((iocb->ki_flags & (IOCB_DSYNC | IOCB_SYNC)) == IOCB_DSYNC)
> - dio->flags |= IOMAP_DIO_WRITE_FUA;
> + /*
> + * For datasync only writes, we optimistically try
> + * using FUA for this IO. Any non-FUA write that
> + * occurs will clear this flag, hence we know before
> + * completion whether a cache flush is necessary.
> + */
> + if (!(iocb->ki_flags & IOCB_SYNC))
> + dio->flags |= IOMAP_DIO_WRITE_FUA;
> + }
> }
>
> if (dio_flags & IOMAP_DIO_OVERWRITE_ONLY) {
> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> index e552097c67e0..c8622d8f064e 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -353,6 +353,12 @@ struct iomap_dio_ops {
> */
> #define IOMAP_DIO_PARTIAL (1 << 2)
>
> +/*
> + * The caller will sync the write if needed; do not sync it within
> + * iomap_dio_rw. Overrides IOMAP_DIO_FORCE_WAIT.
> + */
> +#define IOMAP_DIO_NOSYNC (1 << 3)
> +
> ssize_t iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
> const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
> unsigned int dio_flags, void *private, size_t done_before);
> --
> 2.30.2
>
