On 2020/07/03 15:56, Kanchan Joshi wrote: > On Fri, Jul 03, 2020 at 05:32:56AM +0000, Damien Le Moal wrote: >> On 2020/07/03 0:42, Kanchan Joshi wrote: >>> zone-append with bvec iov_iter gives WARN_ON, and returns -EINVAL. >>> Add new helper to process such iov_iter and add pages in bio honoring >>> zone-append specific constraints. >>> >>> Signed-off-by: Kanchan Joshi <[email protected]> >>> Signed-off-by: Selvakumar S <[email protected]> >>> Signed-off-by: Nitesh Shetty <[email protected]> >>> Signed-off-by: Javier Gonzalez <[email protected]> >>> --- >>> block/bio.c | 31 ++++++++++++++++++++++++++++--- >>> 1 file changed, 28 insertions(+), 3 deletions(-) >>> >>> diff --git a/block/bio.c b/block/bio.c >>> index 0cecdbc..ade9da7 100644 >>> --- a/block/bio.c >>> +++ b/block/bio.c >>> @@ -975,6 +975,30 @@ static int __bio_iov_bvec_add_pages(struct bio *bio, >>> struct iov_iter *iter) >>> iov_iter_advance(iter, size); >>> return 0; >>> } >>> +static int __bio_iov_bvec_append_add_pages(struct bio *bio, struct >>> iov_iter *iter) >>> +{ >>> + const struct bio_vec *bv = iter->bvec; >>> + unsigned int len; >>> + size_t size; >>> + struct request_queue *q = bio->bi_disk->queue; >>> + unsigned int max_append_sectors = queue_max_zone_append_sectors(q); >>> + bool same_page = false; >>> + >>> + if (WARN_ON_ONCE(!max_append_sectors)) >>> + return -EINVAL; >>> + >>> + if (WARN_ON_ONCE(iter->iov_offset > bv->bv_len)) >>> + return -EINVAL; >>> + >>> + len = min_t(size_t, bv->bv_len - iter->iov_offset, iter->count); >>> + size = bio_add_hw_page(q, bio, bv->bv_page, len, >>> + bv->bv_offset + iter->iov_offset, >>> + max_append_sectors, &same_page); >>> + if (unlikely(size != len)) >>> + return -EINVAL; >>> + iov_iter_advance(iter, size); >>> + return 0; >>> +} >>> >>> #define PAGE_PTRS_PER_BVEC (sizeof(struct bio_vec) / sizeof(struct >>> page *)) >>> >>> @@ -1105,9 +1129,10 @@ int bio_iov_iter_get_pages(struct bio *bio, struct >>> iov_iter *iter) >>> >>> do { >>> if (bio_op(bio) == REQ_OP_ZONE_APPEND) { >>> - if (WARN_ON_ONCE(is_bvec)) >>> - return -EINVAL; >>> - ret = __bio_iov_append_get_pages(bio, iter); >>> + if (is_bvec) >>> + ret = __bio_iov_bvec_append_add_pages(bio, >>> iter); >>> + else >>> + ret = __bio_iov_append_get_pages(bio, iter); >>> } else { >>> if (is_bvec) >>> ret = __bio_iov_bvec_add_pages(bio, iter); >>> >> >> The only user of this function that issues zone append requests is zonefs. >> The >> issued requests are not using bvec iter but a user direct IO buffer iter. So >> this change would have no user at all as far as I can see. Am I missing >> something ? What IO path makes this change necessary ? > > Yes, zonefs does not use bvec iter. But while enabling io-uring path for > zone-append, I hit into this condition returning -EINVAL. > > Reference (from user zone-append series cover letter): > "Append using io_uring fixed-buffer ---> > This is flagged as not-supported at the moment. Reason being, for fixed-buffer > io-uring sends iov_iter of bvec type. But current append-infra in block-layer > does not support such iov_iter." > > And zone-append doesn't have a problem in using bvec iter as well, so > thought that this may make infra more complete/future-proof?
As long as there is no possible user for this change, I do not see the point in adding it. -- Damien Le Moal Western Digital Research
