diff options
Diffstat (limited to 'block/blk-merge.c')
-rw-r--r-- | block/blk-merge.c | 351 |
1 files changed, 168 insertions, 183 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c index 71e9ac03f621..17713d7d98d5 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -12,23 +12,6 @@ #include "blk.h" -/* - * Check if the two bvecs from two bios can be merged to one segment. If yes, - * no need to check gap between the two bios since the 1st bio and the 1st bvec - * in the 2nd bio can be handled in one segment. - */ -static inline bool bios_segs_mergeable(struct request_queue *q, - struct bio *prev, struct bio_vec *prev_last_bv, - struct bio_vec *next_first_bv) -{ - if (!biovec_phys_mergeable(q, prev_last_bv, next_first_bv)) - return false; - if (prev->bi_seg_back_size + next_first_bv->bv_len > - queue_max_segment_size(q)) - return false; - return true; -} - static inline bool bio_will_gap(struct request_queue *q, struct request *prev_rq, struct bio *prev, struct bio *next) { @@ -60,7 +43,7 @@ static inline bool bio_will_gap(struct request_queue *q, */ bio_get_last_bvec(prev, &pb); bio_get_first_bvec(next, &nb); - if (bios_segs_mergeable(q, prev, &pb, &nb)) + if (biovec_phys_mergeable(q, &pb, &nb)) return false; return __bvec_gap_to_prev(q, &pb, nb.bv_offset); } @@ -161,6 +144,56 @@ static inline unsigned get_max_io_size(struct request_queue *q, return sectors; } +static unsigned get_max_segment_size(struct request_queue *q, + unsigned offset) +{ + unsigned long mask = queue_segment_boundary(q); + + /* default segment boundary mask means no boundary limit */ + if (mask == BLK_SEG_BOUNDARY_MASK) + return queue_max_segment_size(q); + + return min_t(unsigned long, mask - (mask & offset) + 1, + queue_max_segment_size(q)); +} + +/* + * Split the bvec @bv into segments, and update all kinds of + * variables. + */ +static bool bvec_split_segs(struct request_queue *q, struct bio_vec *bv, + unsigned *nsegs, unsigned *sectors, unsigned max_segs) +{ + unsigned len = bv->bv_len; + unsigned total_len = 0; + unsigned new_nsegs = 0, seg_size = 0; + + /* + * Multi-page bvec may be too big to hold in one segment, so the + * current bvec has to be splitted as multiple segments. + */ + while (len && new_nsegs + *nsegs < max_segs) { + seg_size = get_max_segment_size(q, bv->bv_offset + total_len); + seg_size = min(seg_size, len); + + new_nsegs++; + total_len += seg_size; + len -= seg_size; + + if ((bv->bv_offset + total_len) & queue_virt_boundary(q)) + break; + } + + if (new_nsegs) { + *nsegs += new_nsegs; + if (sectors) + *sectors += total_len >> 9; + } + + /* split in the middle of the bvec if len != 0 */ + return !!len; +} + static struct bio *blk_bio_segment_split(struct request_queue *q, struct bio *bio, struct bio_set *bs, @@ -168,13 +201,13 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, { struct bio_vec bv, bvprv, *bvprvp = NULL; struct bvec_iter iter; - unsigned seg_size = 0, nsegs = 0, sectors = 0; - unsigned front_seg_size = bio->bi_seg_front_size; + unsigned nsegs = 0, sectors = 0; bool do_split = true; struct bio *new = NULL; const unsigned max_sectors = get_max_io_size(q, bio); + const unsigned max_segs = queue_max_segments(q); - bio_for_each_segment(bv, bio, iter) { + bio_for_each_bvec(bv, bio, iter) { /* * If the queue doesn't support SG gaps and adding this * offset would create a gap, disallow it. @@ -187,40 +220,29 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, * Consider this a new segment if we're splitting in * the middle of this vector. */ - if (nsegs < queue_max_segments(q) && + if (nsegs < max_segs && sectors < max_sectors) { - nsegs++; - sectors = max_sectors; + /* split in the middle of bvec */ + bv.bv_len = (max_sectors - sectors) << 9; + bvec_split_segs(q, &bv, &nsegs, + §ors, max_segs); } goto split; } - if (bvprvp) { - if (seg_size + bv.bv_len > queue_max_segment_size(q)) - goto new_segment; - if (!biovec_phys_mergeable(q, bvprvp, &bv)) - goto new_segment; - - seg_size += bv.bv_len; - bvprv = bv; - bvprvp = &bvprv; - sectors += bv.bv_len >> 9; - - continue; - } -new_segment: - if (nsegs == queue_max_segments(q)) + if (nsegs == max_segs) goto split; - if (nsegs == 1 && seg_size > front_seg_size) - front_seg_size = seg_size; - - nsegs++; bvprv = bv; bvprvp = &bvprv; - seg_size = bv.bv_len; - sectors += bv.bv_len >> 9; + if (bv.bv_offset + bv.bv_len <= PAGE_SIZE) { + nsegs++; + sectors += bv.bv_len >> 9; + } else if (bvec_split_segs(q, &bv, &nsegs, §ors, + max_segs)) { + goto split; + } } do_split = false; @@ -233,12 +255,6 @@ split: bio = new; } - if (nsegs == 1 && seg_size > front_seg_size) - front_seg_size = seg_size; - bio->bi_seg_front_size = front_seg_size; - if (seg_size > bio->bi_seg_back_size) - bio->bi_seg_back_size = seg_size; - return do_split ? new : NULL; } @@ -291,14 +307,11 @@ void blk_queue_split(struct request_queue *q, struct bio **bio) EXPORT_SYMBOL(blk_queue_split); static unsigned int __blk_recalc_rq_segments(struct request_queue *q, - struct bio *bio, - bool no_sg_merge) + struct bio *bio) { - struct bio_vec bv, bvprv = { NULL }; - int prev = 0; - unsigned int seg_size, nr_phys_segs; - struct bio *fbio, *bbio; + unsigned int nr_phys_segs = 0; struct bvec_iter iter; + struct bio_vec bv; if (!bio) return 0; @@ -312,161 +325,143 @@ static unsigned int __blk_recalc_rq_segments(struct request_queue *q, return 1; } - fbio = bio; - seg_size = 0; - nr_phys_segs = 0; for_each_bio(bio) { - bio_for_each_segment(bv, bio, iter) { - /* - * If SG merging is disabled, each bio vector is - * a segment - */ - if (no_sg_merge) - goto new_segment; - - if (prev) { - if (seg_size + bv.bv_len - > queue_max_segment_size(q)) - goto new_segment; - if (!biovec_phys_mergeable(q, &bvprv, &bv)) - goto new_segment; - - seg_size += bv.bv_len; - bvprv = bv; - continue; - } -new_segment: - if (nr_phys_segs == 1 && seg_size > - fbio->bi_seg_front_size) - fbio->bi_seg_front_size = seg_size; - - nr_phys_segs++; - bvprv = bv; - prev = 1; - seg_size = bv.bv_len; - } - bbio = bio; + bio_for_each_bvec(bv, bio, iter) + bvec_split_segs(q, &bv, &nr_phys_segs, NULL, UINT_MAX); } - if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size) - fbio->bi_seg_front_size = seg_size; - if (seg_size > bbio->bi_seg_back_size) - bbio->bi_seg_back_size = seg_size; - return nr_phys_segs; } void blk_recalc_rq_segments(struct request *rq) { - bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE, - &rq->q->queue_flags); - - rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio, - no_sg_merge); + rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio); } void blk_recount_segments(struct request_queue *q, struct bio *bio) { - unsigned short seg_cnt; + struct bio *nxt = bio->bi_next; - /* estimate segment number by bi_vcnt for non-cloned bio */ - if (bio_flagged(bio, BIO_CLONED)) - seg_cnt = bio_segments(bio); - else - seg_cnt = bio->bi_vcnt; - - if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) && - (seg_cnt < queue_max_segments(q))) - bio->bi_phys_segments = seg_cnt; - else { - struct bio *nxt = bio->bi_next; - - bio->bi_next = NULL; - bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false); - bio->bi_next = nxt; - } + bio->bi_next = NULL; + bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio); + bio->bi_next = nxt; bio_set_flag(bio, BIO_SEG_VALID); } -static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, - struct bio *nxt) +static inline struct scatterlist *blk_next_sg(struct scatterlist **sg, + struct scatterlist *sglist) { - struct bio_vec end_bv = { NULL }, nxt_bv; - - if (bio->bi_seg_back_size + nxt->bi_seg_front_size > - queue_max_segment_size(q)) - return 0; + if (!*sg) + return sglist; - if (!bio_has_data(bio)) - return 1; - - bio_get_last_bvec(bio, &end_bv); - bio_get_first_bvec(nxt, &nxt_bv); - - return biovec_phys_mergeable(q, &end_bv, &nxt_bv); + /* + * If the driver previously mapped a shorter list, we could see a + * termination bit prematurely unless it fully inits the sg table + * on each mapping. We KNOW that there must be more entries here + * or the driver would be buggy, so force clear the termination bit + * to avoid doing a full sg_init_table() in drivers for each command. + */ + sg_unmark_end(*sg); + return sg_next(*sg); } -static inline void -__blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, - struct scatterlist *sglist, struct bio_vec *bvprv, - struct scatterlist **sg, int *nsegs) +static unsigned blk_bvec_map_sg(struct request_queue *q, + struct bio_vec *bvec, struct scatterlist *sglist, + struct scatterlist **sg) { + unsigned nbytes = bvec->bv_len; + unsigned nsegs = 0, total = 0; - int nbytes = bvec->bv_len; + while (nbytes > 0) { + unsigned offset = bvec->bv_offset + total; + unsigned len = min(get_max_segment_size(q, offset), nbytes); + struct page *page = bvec->bv_page; - if (*sg) { - if ((*sg)->length + nbytes > queue_max_segment_size(q)) - goto new_segment; - if (!biovec_phys_mergeable(q, bvprv, bvec)) - goto new_segment; - - (*sg)->length += nbytes; - } else { -new_segment: - if (!*sg) - *sg = sglist; - else { - /* - * If the driver previously mapped a shorter - * list, we could see a termination bit - * prematurely unless it fully inits the sg - * table on each mapping. We KNOW that there - * must be more entries here or the driver - * would be buggy, so force clear the - * termination bit to avoid doing a full - * sg_init_table() in drivers for each command. - */ - sg_unmark_end(*sg); - *sg = sg_next(*sg); - } + /* + * Unfortunately a fair number of drivers barf on scatterlists + * that have an offset larger than PAGE_SIZE, despite other + * subsystems dealing with that invariant just fine. For now + * stick to the legacy format where we never present those from + * the block layer, but the code below should be removed once + * these offenders (mostly MMC/SD drivers) are fixed. + */ + page += (offset >> PAGE_SHIFT); + offset &= ~PAGE_MASK; - sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); - (*nsegs)++; + *sg = blk_next_sg(sg, sglist); + sg_set_page(*sg, page, len, offset); + + total += len; + nbytes -= len; + nsegs++; } - *bvprv = *bvec; + + return nsegs; } -static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv, +static inline int __blk_bvec_map_sg(struct bio_vec bv, struct scatterlist *sglist, struct scatterlist **sg) { - *sg = sglist; + *sg = blk_next_sg(sg, sglist); sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset); return 1; } +/* only try to merge bvecs into one sg if they are from two bios */ +static inline bool +__blk_segment_map_sg_merge(struct request_queue *q, struct bio_vec *bvec, + struct bio_vec *bvprv, struct scatterlist **sg) +{ + + int nbytes = bvec->bv_len; + + if (!*sg) + return false; + + if ((*sg)->length + nbytes > queue_max_segment_size(q)) + return false; + + if (!biovec_phys_mergeable(q, bvprv, bvec)) + return false; + + (*sg)->length += nbytes; + + return true; +} + static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, struct scatterlist *sglist, struct scatterlist **sg) { - struct bio_vec bvec, bvprv = { NULL }; + struct bio_vec uninitialized_var(bvec), bvprv = { NULL }; struct bvec_iter iter; int nsegs = 0; + bool new_bio = false; - for_each_bio(bio) - bio_for_each_segment(bvec, bio, iter) - __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg, - &nsegs); + for_each_bio(bio) { + bio_for_each_bvec(bvec, bio, iter) { + /* + * Only try to merge bvecs from two bios given we + * have done bio internal merge when adding pages + * to bio + */ + if (new_bio && + __blk_segment_map_sg_merge(q, &bvec, &bvprv, sg)) + goto next_bvec; + + if (bvec.bv_offset + bvec.bv_len <= PAGE_SIZE) + nsegs += __blk_bvec_map_sg(bvec, sglist, sg); + else + nsegs += blk_bvec_map_sg(q, &bvec, sglist, sg); + next_bvec: + new_bio = false; + } + if (likely(bio->bi_iter.bi_size)) { + bvprv = bvec; + new_bio = true; + } + } return nsegs; } @@ -482,9 +477,9 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq, int nsegs = 0; if (rq->rq_flags & RQF_SPECIAL_PAYLOAD) - nsegs = __blk_bvec_map_sg(q, rq->special_vec, sglist, &sg); + nsegs = __blk_bvec_map_sg(rq->special_vec, sglist, &sg); else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME) - nsegs = __blk_bvec_map_sg(q, bio_iovec(rq->bio), sglist, &sg); + nsegs = __blk_bvec_map_sg(bio_iovec(rq->bio), sglist, &sg); else if (rq->bio) nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg); @@ -613,8 +608,6 @@ static int ll_merge_requests_fn(struct request_queue *q, struct request *req, struct request *next) { int total_phys_segments; - unsigned int seg_size = - req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size; if (req_gap_back_merge(req, next->bio)) return 0; @@ -627,14 +620,6 @@ static int ll_merge_requests_fn(struct request_queue *q, struct request *req, return 0; total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; - if (blk_phys_contig_segment(q, req->biotail, next->bio)) { - if (req->nr_phys_segments == 1) - req->bio->bi_seg_front_size = seg_size; - if (next->nr_phys_segments == 1) - next->biotail->bi_seg_back_size = seg_size; - total_phys_segments--; - } - if (total_phys_segments > queue_max_segments(q)) return 0; |