diff options
| author | Jens Axboe <axboe@fb.com> | 2014-06-24 16:22:24 -0600 |
|---|---|---|
| committer | Jens Axboe <axboe@fb.com> | 2014-06-24 16:22:24 -0600 |
| commit | 66cb45aa41315d1d9972cada354fbdf7870d7714 (patch) | |
| tree | 5ca5ef3c31f24a7a11989d8a6a163eed9aaf9528 | |
| parent | 3a4b0eda8e4b27e6aca86f9f4d327c1070815e30 (diff) | |
block: add support for limiting gaps in SG lists
Another restriction inherited for NVMe - those devices don't support
SG lists that have "gaps" in them. Gaps refers to cases where the
previous SG entry doesn't end on a page boundary. For NVMe, all SG
entries must start at offset 0 (except the first) and end on a page
boundary (except the last).
Signed-off-by: Jens Axboe <axboe@fb.com>
| -rw-r--r-- | block/bio.c | 8 | ||||
| -rw-r--r-- | block/blk-merge.c | 10 | ||||
| -rw-r--r-- | include/linux/bio.h | 9 | ||||
| -rw-r--r-- | include/linux/blkdev.h | 1 |
4 files changed, 28 insertions, 0 deletions
diff --git a/block/bio.c b/block/bio.c index 8c2e55e39a1b..0ec61c9e536c 100644 --- a/block/bio.c +++ b/block/bio.c @@ -746,6 +746,14 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page goto done; } + + /* + * If the queue doesn't support SG gaps and adding this + * offset would create a gap, disallow it. + */ + if (q->queue_flags & (1 << QUEUE_FLAG_SG_GAPS) && + bvec_gap_to_prev(prev, offset)) + return 0; } if (bio->bi_vcnt >= bio->bi_max_vecs) diff --git a/block/blk-merge.c b/block/blk-merge.c index b3bf0df0f4c2..54535831f1e1 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -568,6 +568,8 @@ int blk_attempt_req_merge(struct request_queue *q, struct request *rq, bool blk_rq_merge_ok(struct request *rq, struct bio *bio) { + struct request_queue *q = rq->q; + if (!rq_mergeable(rq) || !bio_mergeable(bio)) return false; @@ -591,6 +593,14 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio) !blk_write_same_mergeable(rq->bio, bio)) return false; + if (q->queue_flags & (1 << QUEUE_FLAG_SG_GAPS)) { + struct bio_vec *bprev; + + bprev = &rq->biotail->bi_io_vec[bio->bi_vcnt - 1]; + if (bvec_gap_to_prev(bprev, bio->bi_io_vec[0].bv_offset)) + return false; + } + return true; } diff --git a/include/linux/bio.h b/include/linux/bio.h index f91decbca96b..d2633ee099d9 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -186,6 +186,15 @@ static inline void *bio_data(struct bio *bio) #define BIOVEC_SEG_BOUNDARY(q, b1, b2) \ __BIO_SEG_BOUNDARY(bvec_to_phys((b1)), bvec_to_phys((b2)) + (b2)->bv_len, queue_segment_boundary((q))) +/* + * Check if adding a bio_vec after bprv with offset would create a gap in + * the SG list. Most drivers don't care about this, but some do. + */ +static inline bool bvec_gap_to_prev(struct bio_vec *bprv, unsigned int offset) +{ + return offset || ((bprv->bv_offset + bprv->bv_len) & (PAGE_SIZE - 1)); +} + #define bio_io_error(bio) bio_endio((bio), -EIO) /* diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 713f8b62b435..8699bcf5f099 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -512,6 +512,7 @@ struct request_queue { #define QUEUE_FLAG_DEAD 19 /* queue tear-down finished */ #define QUEUE_FLAG_INIT_DONE 20 /* queue is initialized */ #define QUEUE_FLAG_NO_SG_MERGE 21 /* don't attempt to merge SG segments*/ +#define QUEUE_FLAG_SG_GAPS 22 /* queue doesn't support SG gaps */ #define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \ (1 << QUEUE_FLAG_STACKABLE) | \ |