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.
Would you mind putting this paragraph in a comment before the
bio_iov_iter_get_pages call? I could easily see someone (i.e. 2021 me)
forgetting there's a data dependency and breaking this.
> 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 = ;
> +
> /*
> * 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;
> + }
Also, I think this should be hoisted into a separate helper to return
bi_opf rather than making iomap_dio_bio_actor even longer...
/*
* Figure out the bio's operation flags from the dio request, the
* mapping, and whether or not we want FUA. Note that we can end up
* clearing the WRITE_FUA flag in the dio request.
*/
static inline unsigned int
iomap_dio_bio_opflags(struct iomap_dio *dio, struct iomap *iomap, bool use_fua)
{
unsigned int opflags = REQ_SYNC | REQ_IDLE;
if (!(dio->flags & IOMAP_DIO_WRITE)) {
WARN_ON_ONCE(iomap->flags & IOMAP_F_ZONE_APPEND);
return REQ_OP_READ;
}
if (iomap->flags & IOMAP_F_ZONE_APPEND)
opflags |= REQ_OP_ZONE_APPEND;
else
opflags |= REQ_OP_WRITE;
if (use_fua)
opflags |= REQ_FUA;
else
dio->flags &= ~IOMAP_DIO_WRITE_FUA;
return opflags;
}
/*
* Set the operation flags early so that bio_iov_iter_get_pages can
* set up the page vector appropriately for a ZONE_APPEND operation.
*/
bio->bi_opf = iomap_dio_bio_opflags(dio, iomap, use_fua);
ret = bio_iov_iter_get_pages(bio, dio->submit.iter);
if (unlikely(ret)) {
--D
> +
> 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
>
