/* * 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) { struct bio_vec bv, bvprv = { NULL }; int cluster, high, highprv = 1, no_sg_merge; 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; no_sg_merge = test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags); 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) { rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio); } void blk_recount_segments(struct request_queue *q, struct bio *bio) { if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags)) bio->bi_phys_segments = bio->bi_vcnt; else { struct bio *nxt = bio->bi_next; bio->bi_next = NULL; bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio); 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); /** * blk_bio_map_sg - map a bio to a scatterlist * @q: request_queue in question * @bio: bio being mapped * @sglist: scatterlist being mapped * * Note: * Caller must make sure sg can hold bio->bi_phys_segments entries * * Will return the number of sg entries setup */ int blk_bio_map_sg(struct request_queue *q, struct bio *bio, struct scatterlist *sglist) { struct scatterlist *sg = NULL; int nsegs; struct bio *next = bio->bi_next; bio->bi_next = NULL; nsegs = __blk_bios_map_sg(q, bio, sglist, &sg); bio->bi_next = next; if (sg) sg_mark_end(sg); BUG_ON(bio->bi_phys_segments && nsegs > bio->bi_phys_segments); return nsegs; } EXPORT_SYMBOL(blk_bio_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 (bio_integrity(bio) && blk_integrity_merge_bio(q, req, bio)) 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 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; /* * 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_rq(req) && blk_integrity_merge_rq(q, req, next)) 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 (bio_integrity(bio) != blk_integrity_rq(rq)) 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[bio->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; }