diff options
Diffstat (limited to 'block/blk-merge.c')
| -rw-r--r-- | block/blk-merge.c | 610 |
1 files changed, 610 insertions, 0 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c new file mode 100644 index 000000000..fd3fee81c --- /dev/null +++ b/block/blk-merge.c @@ -0,0 +1,610 @@ +/* + * Functions related to segment and merge handling + */ +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/bio.h> +#include <linux/blkdev.h> +#include <linux/scatterlist.h> + +#include "blk.h" + +static unsigned int __blk_recalc_rq_segments(struct request_queue *q, + struct bio *bio, + bool no_sg_merge) +{ + struct bio_vec bv, bvprv = { NULL }; + int cluster, high, highprv = 1; + unsigned int seg_size, nr_phys_segs; + struct bio *fbio, *bbio; + struct bvec_iter iter; + + if (!bio) + return 0; + + /* + * This should probably be returning 0, but blk_add_request_payload() + * (Christoph!!!!) + */ + if (bio->bi_rw & REQ_DISCARD) + return 1; + + if (bio->bi_rw & REQ_WRITE_SAME) + return 1; + + fbio = bio; + cluster = blk_queue_cluster(q); + seg_size = 0; + nr_phys_segs = 0; + high = 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; + + /* + * the trick here is making sure that a high page is + * never considered part of another segment, since + * that might change with the bounce page. + */ + high = page_to_pfn(bv.bv_page) > queue_bounce_pfn(q); + if (!high && !highprv && cluster) { + if (seg_size + bv.bv_len + > queue_max_segment_size(q)) + goto new_segment; + if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv)) + goto new_segment; + if (!BIOVEC_SEG_BOUNDARY(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; + seg_size = bv.bv_len; + highprv = high; + } + bbio = bio; + } + + 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); +} + +void blk_recount_segments(struct request_queue *q, struct bio *bio) +{ + unsigned short seg_cnt; + + /* 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_flags |= (1 << BIO_SEG_VALID); +} +EXPORT_SYMBOL(blk_recount_segments); + +static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, + struct bio *nxt) +{ + struct bio_vec end_bv = { NULL }, nxt_bv; + struct bvec_iter iter; + + if (!blk_queue_cluster(q)) + return 0; + + if (bio->bi_seg_back_size + nxt->bi_seg_front_size > + queue_max_segment_size(q)) + return 0; + + if (!bio_has_data(bio)) + return 1; + + bio_for_each_segment(end_bv, bio, iter) + if (end_bv.bv_len == iter.bi_size) + break; + + nxt_bv = bio_iovec(nxt); + + if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv)) + return 0; + + /* + * bio and nxt are contiguous in memory; check if the queue allows + * these two to be merged into one + */ + if (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv)) + return 1; + + return 0; +} + +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, int *cluster) +{ + + int nbytes = bvec->bv_len; + + if (*sg && *cluster) { + if ((*sg)->length + nbytes > queue_max_segment_size(q)) + goto new_segment; + + if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) + goto new_segment; + if (!BIOVEC_SEG_BOUNDARY(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); + } + + sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); + (*nsegs)++; + } + *bvprv = *bvec; +} + +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 bvec_iter iter; + int nsegs, cluster; + + nsegs = 0; + cluster = blk_queue_cluster(q); + + if (bio->bi_rw & REQ_DISCARD) { + /* + * This is a hack - drivers should be neither modifying the + * biovec, nor relying on bi_vcnt - but because of + * blk_add_request_payload(), a discard bio may or may not have + * a payload we need to set up here (thank you Christoph) and + * bi_vcnt is really the only way of telling if we need to. + */ + + if (bio->bi_vcnt) + goto single_segment; + + return 0; + } + + if (bio->bi_rw & REQ_WRITE_SAME) { +single_segment: + *sg = sglist; + bvec = bio_iovec(bio); + sg_set_page(*sg, bvec.bv_page, bvec.bv_len, bvec.bv_offset); + return 1; + } + + for_each_bio(bio) + bio_for_each_segment(bvec, bio, iter) + __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg, + &nsegs, &cluster); + + return nsegs; +} + +/* + * map a request to scatterlist, return number of sg entries setup. Caller + * must make sure sg can hold rq->nr_phys_segments entries + */ +int blk_rq_map_sg(struct request_queue *q, struct request *rq, + struct scatterlist *sglist) +{ + struct scatterlist *sg = NULL; + int nsegs = 0; + + if (rq->bio) + nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg); + + if (unlikely(rq->cmd_flags & REQ_COPY_USER) && + (blk_rq_bytes(rq) & q->dma_pad_mask)) { + unsigned int pad_len = + (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1; + + sg->length += pad_len; + rq->extra_len += pad_len; + } + + if (q->dma_drain_size && q->dma_drain_needed(rq)) { + if (rq->cmd_flags & REQ_WRITE) + memset(q->dma_drain_buffer, 0, q->dma_drain_size); + + sg->page_link &= ~0x02; + sg = sg_next(sg); + sg_set_page(sg, virt_to_page(q->dma_drain_buffer), + q->dma_drain_size, + ((unsigned long)q->dma_drain_buffer) & + (PAGE_SIZE - 1)); + nsegs++; + rq->extra_len += q->dma_drain_size; + } + + if (sg) + sg_mark_end(sg); + + return nsegs; +} +EXPORT_SYMBOL(blk_rq_map_sg); + +static inline int ll_new_hw_segment(struct request_queue *q, + struct request *req, + struct bio *bio) +{ + int nr_phys_segs = bio_phys_segments(q, bio); + + if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q)) + goto no_merge; + + if (blk_integrity_merge_bio(q, req, bio) == false) + goto no_merge; + + /* + * This will form the start of a new hw segment. Bump both + * counters. + */ + req->nr_phys_segments += nr_phys_segs; + return 1; + +no_merge: + req->cmd_flags |= REQ_NOMERGE; + if (req == q->last_merge) + q->last_merge = NULL; + return 0; +} + +int ll_back_merge_fn(struct request_queue *q, struct request *req, + struct bio *bio) +{ + if (blk_rq_sectors(req) + bio_sectors(bio) > + blk_rq_get_max_sectors(req)) { + req->cmd_flags |= REQ_NOMERGE; + if (req == q->last_merge) + q->last_merge = NULL; + return 0; + } + if (!bio_flagged(req->biotail, BIO_SEG_VALID)) + blk_recount_segments(q, req->biotail); + if (!bio_flagged(bio, BIO_SEG_VALID)) + blk_recount_segments(q, bio); + + return ll_new_hw_segment(q, req, bio); +} + +int ll_front_merge_fn(struct request_queue *q, struct request *req, + struct bio *bio) +{ + if (blk_rq_sectors(req) + bio_sectors(bio) > + blk_rq_get_max_sectors(req)) { + req->cmd_flags |= REQ_NOMERGE; + if (req == q->last_merge) + q->last_merge = NULL; + return 0; + } + if (!bio_flagged(bio, BIO_SEG_VALID)) + blk_recount_segments(q, bio); + if (!bio_flagged(req->bio, BIO_SEG_VALID)) + blk_recount_segments(q, req->bio); + + return ll_new_hw_segment(q, req, bio); +} + +/* + * blk-mq uses req->special to carry normal driver per-request payload, it + * does not indicate a prepared command that we cannot merge with. + */ +static bool req_no_special_merge(struct request *req) +{ + struct request_queue *q = req->q; + + return !q->mq_ops && req->special; +} + +static int req_gap_to_prev(struct request *req, struct request *next) +{ + struct bio *prev = req->biotail; + + return bvec_gap_to_prev(&prev->bi_io_vec[prev->bi_vcnt - 1], + next->bio->bi_io_vec[0].bv_offset); +} + +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; + + /* + * First check if the either of the requests are re-queued + * requests. Can't merge them if they are. + */ + if (req_no_special_merge(req) || req_no_special_merge(next)) + return 0; + + if (test_bit(QUEUE_FLAG_SG_GAPS, &q->queue_flags) && + req_gap_to_prev(req, next)) + return 0; + + /* + * Will it become too large? + */ + if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > + blk_rq_get_max_sectors(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; + + if (blk_integrity_merge_rq(q, req, next) == false) + return 0; + + /* Merge is OK... */ + req->nr_phys_segments = total_phys_segments; + return 1; +} + +/** + * blk_rq_set_mixed_merge - mark a request as mixed merge + * @rq: request to mark as mixed merge + * + * Description: + * @rq is about to be mixed merged. Make sure the attributes + * which can be mixed are set in each bio and mark @rq as mixed + * merged. + */ +void blk_rq_set_mixed_merge(struct request *rq) +{ + unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK; + struct bio *bio; + + if (rq->cmd_flags & REQ_MIXED_MERGE) + return; + + /* + * @rq will no longer represent mixable attributes for all the + * contained bios. It will just track those of the first one. + * Distributes the attributs to each bio. + */ + for (bio = rq->bio; bio; bio = bio->bi_next) { + WARN_ON_ONCE((bio->bi_rw & REQ_FAILFAST_MASK) && + (bio->bi_rw & REQ_FAILFAST_MASK) != ff); + bio->bi_rw |= ff; + } + rq->cmd_flags |= REQ_MIXED_MERGE; +} + +static void blk_account_io_merge(struct request *req) +{ + if (blk_do_io_stat(req)) { + struct hd_struct *part; + int cpu; + + cpu = part_stat_lock(); + part = req->part; + + part_round_stats(cpu, part); + part_dec_in_flight(part, rq_data_dir(req)); + + hd_struct_put(part); + part_stat_unlock(); + } +} + +/* + * Has to be called with the request spinlock acquired + */ +static int attempt_merge(struct request_queue *q, struct request *req, + struct request *next) +{ + if (!rq_mergeable(req) || !rq_mergeable(next)) + return 0; + + if (!blk_check_merge_flags(req->cmd_flags, next->cmd_flags)) + return 0; + + /* + * not contiguous + */ + if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next)) + return 0; + + if (rq_data_dir(req) != rq_data_dir(next) + || req->rq_disk != next->rq_disk + || req_no_special_merge(next)) + return 0; + + if (req->cmd_flags & REQ_WRITE_SAME && + !blk_write_same_mergeable(req->bio, next->bio)) + return 0; + + /* + * If we are allowed to merge, then append bio list + * from next to rq and release next. merge_requests_fn + * will have updated segment counts, update sector + * counts here. + */ + if (!ll_merge_requests_fn(q, req, next)) + return 0; + + /* + * If failfast settings disagree or any of the two is already + * a mixed merge, mark both as mixed before proceeding. This + * makes sure that all involved bios have mixable attributes + * set properly. + */ + if ((req->cmd_flags | next->cmd_flags) & REQ_MIXED_MERGE || + (req->cmd_flags & REQ_FAILFAST_MASK) != + (next->cmd_flags & REQ_FAILFAST_MASK)) { + blk_rq_set_mixed_merge(req); + blk_rq_set_mixed_merge(next); + } + + /* + * At this point we have either done a back merge + * or front merge. We need the smaller start_time of + * the merged requests to be the current request + * for accounting purposes. + */ + if (time_after(req->start_time, next->start_time)) + req->start_time = next->start_time; + + req->biotail->bi_next = next->bio; + req->biotail = next->biotail; + + req->__data_len += blk_rq_bytes(next); + + elv_merge_requests(q, req, next); + + /* + * 'next' is going away, so update stats accordingly + */ + blk_account_io_merge(next); + + req->ioprio = ioprio_best(req->ioprio, next->ioprio); + if (blk_rq_cpu_valid(next)) + req->cpu = next->cpu; + + /* owner-ship of bio passed from next to req */ + next->bio = NULL; + __blk_put_request(q, next); + return 1; +} + +int attempt_back_merge(struct request_queue *q, struct request *rq) +{ + struct request *next = elv_latter_request(q, rq); + + if (next) + return attempt_merge(q, rq, next); + + return 0; +} + +int attempt_front_merge(struct request_queue *q, struct request *rq) +{ + struct request *prev = elv_former_request(q, rq); + + if (prev) + return attempt_merge(q, prev, rq); + + return 0; +} + +int blk_attempt_req_merge(struct request_queue *q, struct request *rq, + struct request *next) +{ + return attempt_merge(q, rq, next); +} + +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; + + if (!blk_check_merge_flags(rq->cmd_flags, bio->bi_rw)) + return false; + + /* different data direction or already started, don't merge */ + if (bio_data_dir(bio) != rq_data_dir(rq)) + return false; + + /* must be same device and not a special request */ + if (rq->rq_disk != bio->bi_bdev->bd_disk || req_no_special_merge(rq)) + return false; + + /* only merge integrity protected bio into ditto rq */ + if (blk_integrity_merge_bio(rq->q, rq, bio) == false) + return false; + + /* must be using the same buffer */ + if (rq->cmd_flags & REQ_WRITE_SAME && + !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[rq->biotail->bi_vcnt - 1]; + if (bvec_gap_to_prev(bprev, bio->bi_io_vec[0].bv_offset)) + return false; + } + + return true; +} + +int blk_try_merge(struct request *rq, struct bio *bio) +{ + if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) + return ELEVATOR_BACK_MERGE; + else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) + return ELEVATOR_FRONT_MERGE; + return ELEVATOR_NO_MERGE; +} |