Re: [PATCH v9 02/41] iomap: support REQ_OP_ZONE_APPEND

[Naohiro Aota <naohiro.aota@xxxxxxx>]

Note: this patch is for this series.

https://lore.kernel.org/linux-btrfs/cover.1604065156.git.naohiro.aota@xxxxxxx/T/

The patch below uses IOMAP_F_ZONE_APPEND flag to make the iomap bio to be
REQ_OP_ZONE_APPEND.

https://lore.kernel.org/linux-btrfs/cover.1604065156.git.naohiro.aota@xxxxxxx/T/#m7b3f2d01ab554ea4cba244608655268211928799

On Fri, Oct 30, 2020 at 10:51:09PM +0900, Naohiro Aota wrote:
> A ZONE_APPEND bio must follow hardware restrictions (e.g. not exceeding
> max_zone_append_sectors) not to be split. bio_iov_iter_get_pages builds
> such restricted bio using __bio_iov_append_get_pages if bio_op(bio) ==
> REQ_OP_ZONE_APPEND.
>
> To utilize it, we need to set the bio_op before calling
> bio_iov_iter_get_pages(). This commit introduces IOMAP_F_ZONE_APPEND, so
> that iomap user can set the flag to indicate they want REQ_OP_ZONE_APPEND
> and restricted bio.
>
> Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> Cc: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx>
> Cc: linux-xfs@xxxxxxxxxxxxxxx
> Signed-off-by: Naohiro Aota <naohiro.aota@xxxxxxx>
> ---
> fs/iomap/direct-io.c  | 22 ++++++++++++++++------
> include/linux/iomap.h |  1 +
> 2 files changed, 17 insertions(+), 6 deletions(-)
>
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index c1aafb2ab990..e534703c5594 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -210,6 +210,7 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
> 	struct bio *bio;
> 	bool need_zeroout = false;
> 	bool use_fua = false;
> +	bool zone_append = false;
> 	int nr_pages, ret = 0;
> 	size_t copied = 0;
> 	size_t orig_count;
> @@ -241,6 +242,8 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
> 			use_fua = true;
> 	}
>
> +	zone_append = iomap->flags & IOMAP_F_ZONE_APPEND;
> +
> 	/*
> 	 * Save the original count and trim the iter to just the extent we
> 	 * are operating on right now.  The iter will be re-expanded once
> @@ -278,6 +281,19 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
> 		bio->bi_private = dio;
> 		bio->bi_end_io = iomap_dio_bio_end_io;
>
> +		if (dio->flags & IOMAP_DIO_WRITE) {
> +			bio->bi_opf = (zone_append ? REQ_OP_ZONE_APPEND : REQ_OP_WRITE) |
> +				      REQ_SYNC | REQ_IDLE;
> +			if (use_fua)
> +				bio->bi_opf |= REQ_FUA;
> +			else
> +				dio->flags &= ~IOMAP_DIO_WRITE_FUA;
> +		} else {
> +			WARN_ON_ONCE(zone_append);
> +
> +			bio->bi_opf = REQ_OP_READ;
> +		}
> +
> 		ret = bio_iov_iter_get_pages(bio, dio->submit.iter);
> 		if (unlikely(ret)) {
> 			/*
> @@ -292,14 +308,8 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
>
> 		n = bio->bi_iter.bi_size;
> 		if (dio->flags & IOMAP_DIO_WRITE) {
> -			bio->bi_opf = REQ_OP_WRITE | REQ_SYNC | REQ_IDLE;
> -			if (use_fua)
> -				bio->bi_opf |= REQ_FUA;
> -			else
> -				dio->flags &= ~IOMAP_DIO_WRITE_FUA;
> 			task_io_account_write(n);
> 		} else {
> -			bio->bi_opf = REQ_OP_READ;
> 			if (dio->flags & IOMAP_DIO_DIRTY)
> 				bio_set_pages_dirty(bio);
> 		}
> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> index 4d1d3c3469e9..1bccd1880d0d 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -54,6 +54,7 @@ struct vm_fault;
> #define IOMAP_F_SHARED		0x04
> #define IOMAP_F_MERGED		0x08
> #define IOMAP_F_BUFFER_HEAD	0x10
> +#define IOMAP_F_ZONE_APPEND	0x20
>
> /*
>  * Flags set by the core iomap code during operations:
> --
> 2.27.0