1b2441318SGreg Kroah-Hartman // SPDX-License-Identifier: GPL-2.0 2d6d48196SJens Axboe /* 3d6d48196SJens Axboe * Functions related to segment and merge handling 4d6d48196SJens Axboe */ 5d6d48196SJens Axboe #include <linux/kernel.h> 6d6d48196SJens Axboe #include <linux/module.h> 7d6d48196SJens Axboe #include <linux/bio.h> 8d6d48196SJens Axboe #include <linux/blkdev.h> 9d6d48196SJens Axboe #include <linux/scatterlist.h> 10d6d48196SJens Axboe 11cda22646SMike Krinkin #include <trace/events/block.h> 12cda22646SMike Krinkin 13d6d48196SJens Axboe #include "blk.h" 14d6d48196SJens Axboe 1554efd50bSKent Overstreet static struct bio *blk_bio_discard_split(struct request_queue *q, 1654efd50bSKent Overstreet struct bio *bio, 17bdced438SMing Lei struct bio_set *bs, 18bdced438SMing Lei unsigned *nsegs) 1954efd50bSKent Overstreet { 2054efd50bSKent Overstreet unsigned int max_discard_sectors, granularity; 2154efd50bSKent Overstreet int alignment; 2254efd50bSKent Overstreet sector_t tmp; 2354efd50bSKent Overstreet unsigned split_sectors; 2454efd50bSKent Overstreet 25bdced438SMing Lei *nsegs = 1; 26bdced438SMing Lei 2754efd50bSKent Overstreet /* Zero-sector (unknown) and one-sector granularities are the same. */ 2854efd50bSKent Overstreet granularity = max(q->limits.discard_granularity >> 9, 1U); 2954efd50bSKent Overstreet 3054efd50bSKent Overstreet max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9); 3154efd50bSKent Overstreet max_discard_sectors -= max_discard_sectors % granularity; 3254efd50bSKent Overstreet 3354efd50bSKent Overstreet if (unlikely(!max_discard_sectors)) { 3454efd50bSKent Overstreet /* XXX: warn */ 3554efd50bSKent Overstreet return NULL; 3654efd50bSKent Overstreet } 3754efd50bSKent Overstreet 3854efd50bSKent Overstreet if (bio_sectors(bio) <= max_discard_sectors) 3954efd50bSKent Overstreet return NULL; 4054efd50bSKent Overstreet 4154efd50bSKent Overstreet split_sectors = max_discard_sectors; 4254efd50bSKent Overstreet 4354efd50bSKent Overstreet /* 4454efd50bSKent Overstreet * If the next starting sector would be misaligned, stop the discard at 4554efd50bSKent Overstreet * the previous aligned sector. 4654efd50bSKent Overstreet */ 4754efd50bSKent Overstreet alignment = (q->limits.discard_alignment >> 9) % granularity; 4854efd50bSKent Overstreet 4954efd50bSKent Overstreet tmp = bio->bi_iter.bi_sector + split_sectors - alignment; 5054efd50bSKent Overstreet tmp = sector_div(tmp, granularity); 5154efd50bSKent Overstreet 5254efd50bSKent Overstreet if (split_sectors > tmp) 5354efd50bSKent Overstreet split_sectors -= tmp; 5454efd50bSKent Overstreet 5554efd50bSKent Overstreet return bio_split(bio, split_sectors, GFP_NOIO, bs); 5654efd50bSKent Overstreet } 5754efd50bSKent Overstreet 58885fa13fSChristoph Hellwig static struct bio *blk_bio_write_zeroes_split(struct request_queue *q, 59885fa13fSChristoph Hellwig struct bio *bio, struct bio_set *bs, unsigned *nsegs) 60885fa13fSChristoph Hellwig { 61885fa13fSChristoph Hellwig *nsegs = 1; 62885fa13fSChristoph Hellwig 63885fa13fSChristoph Hellwig if (!q->limits.max_write_zeroes_sectors) 64885fa13fSChristoph Hellwig return NULL; 65885fa13fSChristoph Hellwig 66885fa13fSChristoph Hellwig if (bio_sectors(bio) <= q->limits.max_write_zeroes_sectors) 67885fa13fSChristoph Hellwig return NULL; 68885fa13fSChristoph Hellwig 69885fa13fSChristoph Hellwig return bio_split(bio, q->limits.max_write_zeroes_sectors, GFP_NOIO, bs); 70885fa13fSChristoph Hellwig } 71885fa13fSChristoph Hellwig 7254efd50bSKent Overstreet static struct bio *blk_bio_write_same_split(struct request_queue *q, 7354efd50bSKent Overstreet struct bio *bio, 74bdced438SMing Lei struct bio_set *bs, 75bdced438SMing Lei unsigned *nsegs) 7654efd50bSKent Overstreet { 77bdced438SMing Lei *nsegs = 1; 78bdced438SMing Lei 7954efd50bSKent Overstreet if (!q->limits.max_write_same_sectors) 8054efd50bSKent Overstreet return NULL; 8154efd50bSKent Overstreet 8254efd50bSKent Overstreet if (bio_sectors(bio) <= q->limits.max_write_same_sectors) 8354efd50bSKent Overstreet return NULL; 8454efd50bSKent Overstreet 8554efd50bSKent Overstreet return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs); 8654efd50bSKent Overstreet } 8754efd50bSKent Overstreet 88d0e5fbb0SMing Lei static inline unsigned get_max_io_size(struct request_queue *q, 89d0e5fbb0SMing Lei struct bio *bio) 90d0e5fbb0SMing Lei { 91d0e5fbb0SMing Lei unsigned sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector); 92d0e5fbb0SMing Lei unsigned mask = queue_logical_block_size(q) - 1; 93d0e5fbb0SMing Lei 94d0e5fbb0SMing Lei /* aligned to logical block size */ 95d0e5fbb0SMing Lei sectors &= ~(mask >> 9); 96d0e5fbb0SMing Lei 97d0e5fbb0SMing Lei return sectors; 98d0e5fbb0SMing Lei } 99d0e5fbb0SMing Lei 10054efd50bSKent Overstreet static struct bio *blk_bio_segment_split(struct request_queue *q, 10154efd50bSKent Overstreet struct bio *bio, 102bdced438SMing Lei struct bio_set *bs, 103bdced438SMing Lei unsigned *segs) 10454efd50bSKent Overstreet { 1055014c311SJens Axboe struct bio_vec bv, bvprv, *bvprvp = NULL; 10654efd50bSKent Overstreet struct bvec_iter iter; 1078ae12666SKent Overstreet unsigned seg_size = 0, nsegs = 0, sectors = 0; 10802e70742SMing Lei unsigned front_seg_size = bio->bi_seg_front_size; 10902e70742SMing Lei bool do_split = true; 11002e70742SMing Lei struct bio *new = NULL; 111d0e5fbb0SMing Lei const unsigned max_sectors = get_max_io_size(q, bio); 11254efd50bSKent Overstreet 11354efd50bSKent Overstreet bio_for_each_segment(bv, bio, iter) { 11454efd50bSKent Overstreet /* 11554efd50bSKent Overstreet * If the queue doesn't support SG gaps and adding this 11654efd50bSKent Overstreet * offset would create a gap, disallow it. 11754efd50bSKent Overstreet */ 1185014c311SJens Axboe if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset)) 11954efd50bSKent Overstreet goto split; 12054efd50bSKent Overstreet 121d0e5fbb0SMing Lei if (sectors + (bv.bv_len >> 9) > max_sectors) { 122e36f6204SKeith Busch /* 123e36f6204SKeith Busch * Consider this a new segment if we're splitting in 124e36f6204SKeith Busch * the middle of this vector. 125e36f6204SKeith Busch */ 126e36f6204SKeith Busch if (nsegs < queue_max_segments(q) && 127d0e5fbb0SMing Lei sectors < max_sectors) { 128e36f6204SKeith Busch nsegs++; 129d0e5fbb0SMing Lei sectors = max_sectors; 130e36f6204SKeith Busch } 131d0e5fbb0SMing Lei if (sectors) 132e36f6204SKeith Busch goto split; 133d0e5fbb0SMing Lei /* Make this single bvec as the 1st segment */ 134e36f6204SKeith Busch } 135e36f6204SKeith Busch 1365014c311SJens Axboe if (bvprvp && blk_queue_cluster(q)) { 13754efd50bSKent Overstreet if (seg_size + bv.bv_len > queue_max_segment_size(q)) 13854efd50bSKent Overstreet goto new_segment; 1395014c311SJens Axboe if (!BIOVEC_PHYS_MERGEABLE(bvprvp, &bv)) 14054efd50bSKent Overstreet goto new_segment; 1415014c311SJens Axboe if (!BIOVEC_SEG_BOUNDARY(q, bvprvp, &bv)) 14254efd50bSKent Overstreet goto new_segment; 14354efd50bSKent Overstreet 14454efd50bSKent Overstreet seg_size += bv.bv_len; 14554efd50bSKent Overstreet bvprv = bv; 146578270bfSMing Lei bvprvp = &bvprv; 14752cc6eeaSMing Lei sectors += bv.bv_len >> 9; 148a88d32afSMing Lei 149a88d32afSMing Lei if (nsegs == 1 && seg_size > front_seg_size) 150a88d32afSMing Lei front_seg_size = seg_size; 15154efd50bSKent Overstreet continue; 15254efd50bSKent Overstreet } 15354efd50bSKent Overstreet new_segment: 15454efd50bSKent Overstreet if (nsegs == queue_max_segments(q)) 15554efd50bSKent Overstreet goto split; 15654efd50bSKent Overstreet 15754efd50bSKent Overstreet nsegs++; 15854efd50bSKent Overstreet bvprv = bv; 159578270bfSMing Lei bvprvp = &bvprv; 16054efd50bSKent Overstreet seg_size = bv.bv_len; 16152cc6eeaSMing Lei sectors += bv.bv_len >> 9; 16202e70742SMing Lei 16302e70742SMing Lei if (nsegs == 1 && seg_size > front_seg_size) 16402e70742SMing Lei front_seg_size = seg_size; 16554efd50bSKent Overstreet } 16654efd50bSKent Overstreet 16702e70742SMing Lei do_split = false; 16854efd50bSKent Overstreet split: 169bdced438SMing Lei *segs = nsegs; 17002e70742SMing Lei 17102e70742SMing Lei if (do_split) { 17202e70742SMing Lei new = bio_split(bio, sectors, GFP_NOIO, bs); 17302e70742SMing Lei if (new) 17402e70742SMing Lei bio = new; 17502e70742SMing Lei } 17602e70742SMing Lei 17702e70742SMing Lei bio->bi_seg_front_size = front_seg_size; 17802e70742SMing Lei if (seg_size > bio->bi_seg_back_size) 17902e70742SMing Lei bio->bi_seg_back_size = seg_size; 18002e70742SMing Lei 18102e70742SMing Lei return do_split ? new : NULL; 18254efd50bSKent Overstreet } 18354efd50bSKent Overstreet 184af67c31fSNeilBrown void blk_queue_split(struct request_queue *q, struct bio **bio) 18554efd50bSKent Overstreet { 186bdced438SMing Lei struct bio *split, *res; 187bdced438SMing Lei unsigned nsegs; 18854efd50bSKent Overstreet 1897afafc8aSAdrian Hunter switch (bio_op(*bio)) { 1907afafc8aSAdrian Hunter case REQ_OP_DISCARD: 1917afafc8aSAdrian Hunter case REQ_OP_SECURE_ERASE: 192af67c31fSNeilBrown split = blk_bio_discard_split(q, *bio, q->bio_split, &nsegs); 1937afafc8aSAdrian Hunter break; 194a6f0788eSChaitanya Kulkarni case REQ_OP_WRITE_ZEROES: 195af67c31fSNeilBrown split = blk_bio_write_zeroes_split(q, *bio, q->bio_split, &nsegs); 196a6f0788eSChaitanya Kulkarni break; 1977afafc8aSAdrian Hunter case REQ_OP_WRITE_SAME: 198af67c31fSNeilBrown split = blk_bio_write_same_split(q, *bio, q->bio_split, &nsegs); 1997afafc8aSAdrian Hunter break; 2007afafc8aSAdrian Hunter default: 201bdced438SMing Lei split = blk_bio_segment_split(q, *bio, q->bio_split, &nsegs); 2027afafc8aSAdrian Hunter break; 2037afafc8aSAdrian Hunter } 204bdced438SMing Lei 205bdced438SMing Lei /* physical segments can be figured out during splitting */ 206bdced438SMing Lei res = split ? split : *bio; 207bdced438SMing Lei res->bi_phys_segments = nsegs; 208bdced438SMing Lei bio_set_flag(res, BIO_SEG_VALID); 20954efd50bSKent Overstreet 21054efd50bSKent Overstreet if (split) { 2116ac45aebSMing Lei /* there isn't chance to merge the splitted bio */ 2121eff9d32SJens Axboe split->bi_opf |= REQ_NOMERGE; 2136ac45aebSMing Lei 21454efd50bSKent Overstreet bio_chain(split, *bio); 215cda22646SMike Krinkin trace_block_split(q, split, (*bio)->bi_iter.bi_sector); 21654efd50bSKent Overstreet generic_make_request(*bio); 21754efd50bSKent Overstreet *bio = split; 21854efd50bSKent Overstreet } 21954efd50bSKent Overstreet } 22054efd50bSKent Overstreet EXPORT_SYMBOL(blk_queue_split); 22154efd50bSKent Overstreet 2221e428079SJens Axboe static unsigned int __blk_recalc_rq_segments(struct request_queue *q, 22307388549SMing Lei struct bio *bio, 22407388549SMing Lei bool no_sg_merge) 225d6d48196SJens Axboe { 2267988613bSKent Overstreet struct bio_vec bv, bvprv = { NULL }; 22754efd50bSKent Overstreet int cluster, prev = 0; 2281e428079SJens Axboe unsigned int seg_size, nr_phys_segs; 22959247eaeSJens Axboe struct bio *fbio, *bbio; 2307988613bSKent Overstreet struct bvec_iter iter; 231d6d48196SJens Axboe 2321e428079SJens Axboe if (!bio) 2331e428079SJens Axboe return 0; 234d6d48196SJens Axboe 235a6f0788eSChaitanya Kulkarni switch (bio_op(bio)) { 236a6f0788eSChaitanya Kulkarni case REQ_OP_DISCARD: 237a6f0788eSChaitanya Kulkarni case REQ_OP_SECURE_ERASE: 238a6f0788eSChaitanya Kulkarni case REQ_OP_WRITE_ZEROES: 239f9d03f96SChristoph Hellwig return 0; 240f9d03f96SChristoph Hellwig case REQ_OP_WRITE_SAME: 2415cb8850cSKent Overstreet return 1; 242a6f0788eSChaitanya Kulkarni } 2435cb8850cSKent Overstreet 2441e428079SJens Axboe fbio = bio; 245e692cb66SMartin K. Petersen cluster = blk_queue_cluster(q); 2465df97b91SMikulas Patocka seg_size = 0; 2472c8919deSAndi Kleen nr_phys_segs = 0; 2481e428079SJens Axboe for_each_bio(bio) { 2497988613bSKent Overstreet bio_for_each_segment(bv, bio, iter) { 250d6d48196SJens Axboe /* 25105f1dd53SJens Axboe * If SG merging is disabled, each bio vector is 25205f1dd53SJens Axboe * a segment 25305f1dd53SJens Axboe */ 25405f1dd53SJens Axboe if (no_sg_merge) 25505f1dd53SJens Axboe goto new_segment; 25605f1dd53SJens Axboe 25754efd50bSKent Overstreet if (prev && cluster) { 2587988613bSKent Overstreet if (seg_size + bv.bv_len 259ae03bf63SMartin K. Petersen > queue_max_segment_size(q)) 260d6d48196SJens Axboe goto new_segment; 2617988613bSKent Overstreet if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv)) 262d6d48196SJens Axboe goto new_segment; 2637988613bSKent Overstreet if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv)) 264d6d48196SJens Axboe goto new_segment; 265d6d48196SJens Axboe 2667988613bSKent Overstreet seg_size += bv.bv_len; 267d6d48196SJens Axboe bvprv = bv; 268d6d48196SJens Axboe continue; 269d6d48196SJens Axboe } 270d6d48196SJens Axboe new_segment: 2711e428079SJens Axboe if (nr_phys_segs == 1 && seg_size > 2721e428079SJens Axboe fbio->bi_seg_front_size) 2731e428079SJens Axboe fbio->bi_seg_front_size = seg_size; 27486771427SFUJITA Tomonori 275d6d48196SJens Axboe nr_phys_segs++; 276d6d48196SJens Axboe bvprv = bv; 27754efd50bSKent Overstreet prev = 1; 2787988613bSKent Overstreet seg_size = bv.bv_len; 279d6d48196SJens Axboe } 28059247eaeSJens Axboe bbio = bio; 2811e428079SJens Axboe } 282d6d48196SJens Axboe 28359247eaeSJens Axboe if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size) 28459247eaeSJens Axboe fbio->bi_seg_front_size = seg_size; 28559247eaeSJens Axboe if (seg_size > bbio->bi_seg_back_size) 28659247eaeSJens Axboe bbio->bi_seg_back_size = seg_size; 2871e428079SJens Axboe 2881e428079SJens Axboe return nr_phys_segs; 2891e428079SJens Axboe } 2901e428079SJens Axboe 2911e428079SJens Axboe void blk_recalc_rq_segments(struct request *rq) 2921e428079SJens Axboe { 29307388549SMing Lei bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE, 29407388549SMing Lei &rq->q->queue_flags); 29507388549SMing Lei 29607388549SMing Lei rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio, 29707388549SMing Lei no_sg_merge); 298d6d48196SJens Axboe } 299d6d48196SJens Axboe 300d6d48196SJens Axboe void blk_recount_segments(struct request_queue *q, struct bio *bio) 301d6d48196SJens Axboe { 3027f60dcaaSMing Lei unsigned short seg_cnt; 303764f612cSMing Lei 3047f60dcaaSMing Lei /* estimate segment number by bi_vcnt for non-cloned bio */ 3057f60dcaaSMing Lei if (bio_flagged(bio, BIO_CLONED)) 3067f60dcaaSMing Lei seg_cnt = bio_segments(bio); 3077f60dcaaSMing Lei else 3087f60dcaaSMing Lei seg_cnt = bio->bi_vcnt; 3097f60dcaaSMing Lei 3107f60dcaaSMing Lei if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) && 3117f60dcaaSMing Lei (seg_cnt < queue_max_segments(q))) 3127f60dcaaSMing Lei bio->bi_phys_segments = seg_cnt; 31305f1dd53SJens Axboe else { 314d6d48196SJens Axboe struct bio *nxt = bio->bi_next; 3151e428079SJens Axboe 316d6d48196SJens Axboe bio->bi_next = NULL; 3177f60dcaaSMing Lei bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false); 318d6d48196SJens Axboe bio->bi_next = nxt; 31905f1dd53SJens Axboe } 32005f1dd53SJens Axboe 321b7c44ed9SJens Axboe bio_set_flag(bio, BIO_SEG_VALID); 322d6d48196SJens Axboe } 323d6d48196SJens Axboe EXPORT_SYMBOL(blk_recount_segments); 324d6d48196SJens Axboe 325d6d48196SJens Axboe static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, 326d6d48196SJens Axboe struct bio *nxt) 327d6d48196SJens Axboe { 3282b8221e1SKent Overstreet struct bio_vec end_bv = { NULL }, nxt_bv; 329f619d254SKent Overstreet 330e692cb66SMartin K. Petersen if (!blk_queue_cluster(q)) 331d6d48196SJens Axboe return 0; 332d6d48196SJens Axboe 33386771427SFUJITA Tomonori if (bio->bi_seg_back_size + nxt->bi_seg_front_size > 334ae03bf63SMartin K. Petersen queue_max_segment_size(q)) 335d6d48196SJens Axboe return 0; 336d6d48196SJens Axboe 337e17fc0a1SDavid Woodhouse if (!bio_has_data(bio)) 338e17fc0a1SDavid Woodhouse return 1; 339e17fc0a1SDavid Woodhouse 340e827091cSMing Lei bio_get_last_bvec(bio, &end_bv); 341e827091cSMing Lei bio_get_first_bvec(nxt, &nxt_bv); 342f619d254SKent Overstreet 343f619d254SKent Overstreet if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv)) 344e17fc0a1SDavid Woodhouse return 0; 345e17fc0a1SDavid Woodhouse 346d6d48196SJens Axboe /* 347e17fc0a1SDavid Woodhouse * bio and nxt are contiguous in memory; check if the queue allows 348d6d48196SJens Axboe * these two to be merged into one 349d6d48196SJens Axboe */ 350f619d254SKent Overstreet if (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv)) 351d6d48196SJens Axboe return 1; 352d6d48196SJens Axboe 353d6d48196SJens Axboe return 0; 354d6d48196SJens Axboe } 355d6d48196SJens Axboe 3567988613bSKent Overstreet static inline void 357963ab9e5SAsias He __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, 3587988613bSKent Overstreet struct scatterlist *sglist, struct bio_vec *bvprv, 359963ab9e5SAsias He struct scatterlist **sg, int *nsegs, int *cluster) 360963ab9e5SAsias He { 361963ab9e5SAsias He 362963ab9e5SAsias He int nbytes = bvec->bv_len; 363963ab9e5SAsias He 3647988613bSKent Overstreet if (*sg && *cluster) { 365963ab9e5SAsias He if ((*sg)->length + nbytes > queue_max_segment_size(q)) 366963ab9e5SAsias He goto new_segment; 367963ab9e5SAsias He 3687988613bSKent Overstreet if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) 369963ab9e5SAsias He goto new_segment; 3707988613bSKent Overstreet if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec)) 371963ab9e5SAsias He goto new_segment; 372963ab9e5SAsias He 373963ab9e5SAsias He (*sg)->length += nbytes; 374963ab9e5SAsias He } else { 375963ab9e5SAsias He new_segment: 376963ab9e5SAsias He if (!*sg) 377963ab9e5SAsias He *sg = sglist; 378963ab9e5SAsias He else { 379963ab9e5SAsias He /* 380963ab9e5SAsias He * If the driver previously mapped a shorter 381963ab9e5SAsias He * list, we could see a termination bit 382963ab9e5SAsias He * prematurely unless it fully inits the sg 383963ab9e5SAsias He * table on each mapping. We KNOW that there 384963ab9e5SAsias He * must be more entries here or the driver 385963ab9e5SAsias He * would be buggy, so force clear the 386963ab9e5SAsias He * termination bit to avoid doing a full 387963ab9e5SAsias He * sg_init_table() in drivers for each command. 388963ab9e5SAsias He */ 389c8164d89SPaolo Bonzini sg_unmark_end(*sg); 390963ab9e5SAsias He *sg = sg_next(*sg); 391963ab9e5SAsias He } 392963ab9e5SAsias He 393963ab9e5SAsias He sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); 394963ab9e5SAsias He (*nsegs)++; 395963ab9e5SAsias He } 3967988613bSKent Overstreet *bvprv = *bvec; 397963ab9e5SAsias He } 398963ab9e5SAsias He 399f9d03f96SChristoph Hellwig static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv, 400f9d03f96SChristoph Hellwig struct scatterlist *sglist, struct scatterlist **sg) 401f9d03f96SChristoph Hellwig { 402f9d03f96SChristoph Hellwig *sg = sglist; 403f9d03f96SChristoph Hellwig sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset); 404f9d03f96SChristoph Hellwig return 1; 405f9d03f96SChristoph Hellwig } 406f9d03f96SChristoph Hellwig 4075cb8850cSKent Overstreet static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, 4085cb8850cSKent Overstreet struct scatterlist *sglist, 4095cb8850cSKent Overstreet struct scatterlist **sg) 4105cb8850cSKent Overstreet { 4115cb8850cSKent Overstreet struct bio_vec bvec, bvprv = { NULL }; 4125cb8850cSKent Overstreet struct bvec_iter iter; 413f9d03f96SChristoph Hellwig int cluster = blk_queue_cluster(q), nsegs = 0; 4145cb8850cSKent Overstreet 4155cb8850cSKent Overstreet for_each_bio(bio) 4165cb8850cSKent Overstreet bio_for_each_segment(bvec, bio, iter) 4175cb8850cSKent Overstreet __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg, 4185cb8850cSKent Overstreet &nsegs, &cluster); 4195cb8850cSKent Overstreet 4205cb8850cSKent Overstreet return nsegs; 4215cb8850cSKent Overstreet } 4225cb8850cSKent Overstreet 423d6d48196SJens Axboe /* 424d6d48196SJens Axboe * map a request to scatterlist, return number of sg entries setup. Caller 425d6d48196SJens Axboe * must make sure sg can hold rq->nr_phys_segments entries 426d6d48196SJens Axboe */ 427d6d48196SJens Axboe int blk_rq_map_sg(struct request_queue *q, struct request *rq, 428d6d48196SJens Axboe struct scatterlist *sglist) 429d6d48196SJens Axboe { 4305cb8850cSKent Overstreet struct scatterlist *sg = NULL; 4315cb8850cSKent Overstreet int nsegs = 0; 432d6d48196SJens Axboe 433f9d03f96SChristoph Hellwig if (rq->rq_flags & RQF_SPECIAL_PAYLOAD) 434f9d03f96SChristoph Hellwig nsegs = __blk_bvec_map_sg(q, rq->special_vec, sglist, &sg); 435f9d03f96SChristoph Hellwig else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME) 436f9d03f96SChristoph Hellwig nsegs = __blk_bvec_map_sg(q, bio_iovec(rq->bio), sglist, &sg); 437f9d03f96SChristoph Hellwig else if (rq->bio) 4385cb8850cSKent Overstreet nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg); 439f18573abSFUJITA Tomonori 440e8064021SChristoph Hellwig if (unlikely(rq->rq_flags & RQF_COPY_USER) && 4412e46e8b2STejun Heo (blk_rq_bytes(rq) & q->dma_pad_mask)) { 4422e46e8b2STejun Heo unsigned int pad_len = 4432e46e8b2STejun Heo (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1; 444f18573abSFUJITA Tomonori 445f18573abSFUJITA Tomonori sg->length += pad_len; 446f18573abSFUJITA Tomonori rq->extra_len += pad_len; 447f18573abSFUJITA Tomonori } 448f18573abSFUJITA Tomonori 4492fb98e84STejun Heo if (q->dma_drain_size && q->dma_drain_needed(rq)) { 450a8ebb056SMike Christie if (op_is_write(req_op(rq))) 451db0a2e00STejun Heo memset(q->dma_drain_buffer, 0, q->dma_drain_size); 452db0a2e00STejun Heo 453da81ed16SDan Williams sg_unmark_end(sg); 454d6d48196SJens Axboe sg = sg_next(sg); 455d6d48196SJens Axboe sg_set_page(sg, virt_to_page(q->dma_drain_buffer), 456d6d48196SJens Axboe q->dma_drain_size, 457d6d48196SJens Axboe ((unsigned long)q->dma_drain_buffer) & 458d6d48196SJens Axboe (PAGE_SIZE - 1)); 459d6d48196SJens Axboe nsegs++; 4607a85f889SFUJITA Tomonori rq->extra_len += q->dma_drain_size; 461d6d48196SJens Axboe } 462d6d48196SJens Axboe 463d6d48196SJens Axboe if (sg) 464d6d48196SJens Axboe sg_mark_end(sg); 465d6d48196SJens Axboe 46612e57f59SMing Lei /* 46712e57f59SMing Lei * Something must have been wrong if the figured number of 46812e57f59SMing Lei * segment is bigger than number of req's physical segments 46912e57f59SMing Lei */ 470f9d03f96SChristoph Hellwig WARN_ON(nsegs > blk_rq_nr_phys_segments(rq)); 47112e57f59SMing Lei 472d6d48196SJens Axboe return nsegs; 473d6d48196SJens Axboe } 474d6d48196SJens Axboe EXPORT_SYMBOL(blk_rq_map_sg); 475d6d48196SJens Axboe 476d6d48196SJens Axboe static inline int ll_new_hw_segment(struct request_queue *q, 477d6d48196SJens Axboe struct request *req, 478d6d48196SJens Axboe struct bio *bio) 479d6d48196SJens Axboe { 480d6d48196SJens Axboe int nr_phys_segs = bio_phys_segments(q, bio); 481d6d48196SJens Axboe 48213f05c8dSMartin K. Petersen if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q)) 48313f05c8dSMartin K. Petersen goto no_merge; 48413f05c8dSMartin K. Petersen 4854eaf99beSMartin K. Petersen if (blk_integrity_merge_bio(q, req, bio) == false) 48613f05c8dSMartin K. Petersen goto no_merge; 487d6d48196SJens Axboe 488d6d48196SJens Axboe /* 489d6d48196SJens Axboe * This will form the start of a new hw segment. Bump both 490d6d48196SJens Axboe * counters. 491d6d48196SJens Axboe */ 492d6d48196SJens Axboe req->nr_phys_segments += nr_phys_segs; 493d6d48196SJens Axboe return 1; 49413f05c8dSMartin K. Petersen 49513f05c8dSMartin K. Petersen no_merge: 496e0c72300SRitesh Harjani req_set_nomerge(q, req); 49713f05c8dSMartin K. Petersen return 0; 498d6d48196SJens Axboe } 499d6d48196SJens Axboe 500d6d48196SJens Axboe int ll_back_merge_fn(struct request_queue *q, struct request *req, 501d6d48196SJens Axboe struct bio *bio) 502d6d48196SJens Axboe { 5035e7c4274SJens Axboe if (req_gap_back_merge(req, bio)) 5045e7c4274SJens Axboe return 0; 5057f39add3SSagi Grimberg if (blk_integrity_rq(req) && 5067f39add3SSagi Grimberg integrity_req_gap_back_merge(req, bio)) 5077f39add3SSagi Grimberg return 0; 508f31dc1cdSMartin K. Petersen if (blk_rq_sectors(req) + bio_sectors(bio) > 50917007f39SDamien Le Moal blk_rq_get_max_sectors(req, blk_rq_pos(req))) { 510e0c72300SRitesh Harjani req_set_nomerge(q, req); 511d6d48196SJens Axboe return 0; 512d6d48196SJens Axboe } 5132cdf79caSJens Axboe if (!bio_flagged(req->biotail, BIO_SEG_VALID)) 514d6d48196SJens Axboe blk_recount_segments(q, req->biotail); 5152cdf79caSJens Axboe if (!bio_flagged(bio, BIO_SEG_VALID)) 516d6d48196SJens Axboe blk_recount_segments(q, bio); 517d6d48196SJens Axboe 518d6d48196SJens Axboe return ll_new_hw_segment(q, req, bio); 519d6d48196SJens Axboe } 520d6d48196SJens Axboe 521d6d48196SJens Axboe int ll_front_merge_fn(struct request_queue *q, struct request *req, 522d6d48196SJens Axboe struct bio *bio) 523d6d48196SJens Axboe { 5245e7c4274SJens Axboe 5255e7c4274SJens Axboe if (req_gap_front_merge(req, bio)) 5265e7c4274SJens Axboe return 0; 5277f39add3SSagi Grimberg if (blk_integrity_rq(req) && 5287f39add3SSagi Grimberg integrity_req_gap_front_merge(req, bio)) 5297f39add3SSagi Grimberg return 0; 530f31dc1cdSMartin K. Petersen if (blk_rq_sectors(req) + bio_sectors(bio) > 53117007f39SDamien Le Moal blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) { 532e0c72300SRitesh Harjani req_set_nomerge(q, req); 533d6d48196SJens Axboe return 0; 534d6d48196SJens Axboe } 5352cdf79caSJens Axboe if (!bio_flagged(bio, BIO_SEG_VALID)) 536d6d48196SJens Axboe blk_recount_segments(q, bio); 5372cdf79caSJens Axboe if (!bio_flagged(req->bio, BIO_SEG_VALID)) 538d6d48196SJens Axboe blk_recount_segments(q, req->bio); 539d6d48196SJens Axboe 540d6d48196SJens Axboe return ll_new_hw_segment(q, req, bio); 541d6d48196SJens Axboe } 542d6d48196SJens Axboe 543e7e24500SJens Axboe /* 544e7e24500SJens Axboe * blk-mq uses req->special to carry normal driver per-request payload, it 545e7e24500SJens Axboe * does not indicate a prepared command that we cannot merge with. 546e7e24500SJens Axboe */ 547e7e24500SJens Axboe static bool req_no_special_merge(struct request *req) 548e7e24500SJens Axboe { 549e7e24500SJens Axboe struct request_queue *q = req->q; 550e7e24500SJens Axboe 551e7e24500SJens Axboe return !q->mq_ops && req->special; 552e7e24500SJens Axboe } 553e7e24500SJens Axboe 554d6d48196SJens Axboe static int ll_merge_requests_fn(struct request_queue *q, struct request *req, 555d6d48196SJens Axboe struct request *next) 556d6d48196SJens Axboe { 557d6d48196SJens Axboe int total_phys_segments; 55886771427SFUJITA Tomonori unsigned int seg_size = 55986771427SFUJITA Tomonori req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size; 560d6d48196SJens Axboe 561d6d48196SJens Axboe /* 562d6d48196SJens Axboe * First check if the either of the requests are re-queued 563d6d48196SJens Axboe * requests. Can't merge them if they are. 564d6d48196SJens Axboe */ 565e7e24500SJens Axboe if (req_no_special_merge(req) || req_no_special_merge(next)) 566d6d48196SJens Axboe return 0; 567d6d48196SJens Axboe 5685e7c4274SJens Axboe if (req_gap_back_merge(req, next->bio)) 569854fbb9cSKeith Busch return 0; 570854fbb9cSKeith Busch 571d6d48196SJens Axboe /* 572d6d48196SJens Axboe * Will it become too large? 573d6d48196SJens Axboe */ 574f31dc1cdSMartin K. Petersen if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > 57517007f39SDamien Le Moal blk_rq_get_max_sectors(req, blk_rq_pos(req))) 576d6d48196SJens Axboe return 0; 577d6d48196SJens Axboe 578d6d48196SJens Axboe total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; 57986771427SFUJITA Tomonori if (blk_phys_contig_segment(q, req->biotail, next->bio)) { 58086771427SFUJITA Tomonori if (req->nr_phys_segments == 1) 58186771427SFUJITA Tomonori req->bio->bi_seg_front_size = seg_size; 58286771427SFUJITA Tomonori if (next->nr_phys_segments == 1) 58386771427SFUJITA Tomonori next->biotail->bi_seg_back_size = seg_size; 584d6d48196SJens Axboe total_phys_segments--; 58586771427SFUJITA Tomonori } 586d6d48196SJens Axboe 5878a78362cSMartin K. Petersen if (total_phys_segments > queue_max_segments(q)) 588d6d48196SJens Axboe return 0; 589d6d48196SJens Axboe 5904eaf99beSMartin K. Petersen if (blk_integrity_merge_rq(q, req, next) == false) 59113f05c8dSMartin K. Petersen return 0; 59213f05c8dSMartin K. Petersen 593d6d48196SJens Axboe /* Merge is OK... */ 594d6d48196SJens Axboe req->nr_phys_segments = total_phys_segments; 595d6d48196SJens Axboe return 1; 596d6d48196SJens Axboe } 597d6d48196SJens Axboe 59880a761fdSTejun Heo /** 59980a761fdSTejun Heo * blk_rq_set_mixed_merge - mark a request as mixed merge 60080a761fdSTejun Heo * @rq: request to mark as mixed merge 60180a761fdSTejun Heo * 60280a761fdSTejun Heo * Description: 60380a761fdSTejun Heo * @rq is about to be mixed merged. Make sure the attributes 60480a761fdSTejun Heo * which can be mixed are set in each bio and mark @rq as mixed 60580a761fdSTejun Heo * merged. 60680a761fdSTejun Heo */ 60780a761fdSTejun Heo void blk_rq_set_mixed_merge(struct request *rq) 60880a761fdSTejun Heo { 60980a761fdSTejun Heo unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK; 61080a761fdSTejun Heo struct bio *bio; 61180a761fdSTejun Heo 612e8064021SChristoph Hellwig if (rq->rq_flags & RQF_MIXED_MERGE) 61380a761fdSTejun Heo return; 61480a761fdSTejun Heo 61580a761fdSTejun Heo /* 61680a761fdSTejun Heo * @rq will no longer represent mixable attributes for all the 61780a761fdSTejun Heo * contained bios. It will just track those of the first one. 61880a761fdSTejun Heo * Distributes the attributs to each bio. 61980a761fdSTejun Heo */ 62080a761fdSTejun Heo for (bio = rq->bio; bio; bio = bio->bi_next) { 6211eff9d32SJens Axboe WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) && 6221eff9d32SJens Axboe (bio->bi_opf & REQ_FAILFAST_MASK) != ff); 6231eff9d32SJens Axboe bio->bi_opf |= ff; 62480a761fdSTejun Heo } 625e8064021SChristoph Hellwig rq->rq_flags |= RQF_MIXED_MERGE; 62680a761fdSTejun Heo } 62780a761fdSTejun Heo 62826308eabSJerome Marchand static void blk_account_io_merge(struct request *req) 62926308eabSJerome Marchand { 63026308eabSJerome Marchand if (blk_do_io_stat(req)) { 63126308eabSJerome Marchand struct hd_struct *part; 63226308eabSJerome Marchand int cpu; 63326308eabSJerome Marchand 63426308eabSJerome Marchand cpu = part_stat_lock(); 63509e099d4SJerome Marchand part = req->part; 63626308eabSJerome Marchand 637d62e26b3SJens Axboe part_round_stats(req->q, cpu, part); 638d62e26b3SJens Axboe part_dec_in_flight(req->q, part, rq_data_dir(req)); 63926308eabSJerome Marchand 6406c23a968SJens Axboe hd_struct_put(part); 64126308eabSJerome Marchand part_stat_unlock(); 64226308eabSJerome Marchand } 64326308eabSJerome Marchand } 64426308eabSJerome Marchand 645d6d48196SJens Axboe /* 646b973cb7eSJens Axboe * For non-mq, this has to be called with the request spinlock acquired. 647b973cb7eSJens Axboe * For mq with scheduling, the appropriate queue wide lock should be held. 648d6d48196SJens Axboe */ 649b973cb7eSJens Axboe static struct request *attempt_merge(struct request_queue *q, 650b973cb7eSJens Axboe struct request *req, struct request *next) 651d6d48196SJens Axboe { 6522fff8a92SBart Van Assche if (!q->mq_ops) 6532fff8a92SBart Van Assche lockdep_assert_held(q->queue_lock); 6542fff8a92SBart Van Assche 655d6d48196SJens Axboe if (!rq_mergeable(req) || !rq_mergeable(next)) 656b973cb7eSJens Axboe return NULL; 657d6d48196SJens Axboe 658288dab8aSChristoph Hellwig if (req_op(req) != req_op(next)) 659b973cb7eSJens Axboe return NULL; 660f31dc1cdSMartin K. Petersen 661d6d48196SJens Axboe /* 662d6d48196SJens Axboe * not contiguous 663d6d48196SJens Axboe */ 66483096ebfSTejun Heo if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next)) 665b973cb7eSJens Axboe return NULL; 666d6d48196SJens Axboe 667d6d48196SJens Axboe if (rq_data_dir(req) != rq_data_dir(next) 668d6d48196SJens Axboe || req->rq_disk != next->rq_disk 669e7e24500SJens Axboe || req_no_special_merge(next)) 670b973cb7eSJens Axboe return NULL; 671d6d48196SJens Axboe 6728fe0d473SMike Christie if (req_op(req) == REQ_OP_WRITE_SAME && 6734363ac7cSMartin K. Petersen !blk_write_same_mergeable(req->bio, next->bio)) 674b973cb7eSJens Axboe return NULL; 6754363ac7cSMartin K. Petersen 676d6d48196SJens Axboe /* 677cb6934f8SJens Axboe * Don't allow merge of different write hints, or for a hint with 678cb6934f8SJens Axboe * non-hint IO. 679cb6934f8SJens Axboe */ 680cb6934f8SJens Axboe if (req->write_hint != next->write_hint) 681cb6934f8SJens Axboe return NULL; 682cb6934f8SJens Axboe 683cb6934f8SJens Axboe /* 684d6d48196SJens Axboe * If we are allowed to merge, then append bio list 685d6d48196SJens Axboe * from next to rq and release next. merge_requests_fn 686d6d48196SJens Axboe * will have updated segment counts, update sector 687d6d48196SJens Axboe * counts here. 688d6d48196SJens Axboe */ 689d6d48196SJens Axboe if (!ll_merge_requests_fn(q, req, next)) 690b973cb7eSJens Axboe return NULL; 691d6d48196SJens Axboe 692d6d48196SJens Axboe /* 69380a761fdSTejun Heo * If failfast settings disagree or any of the two is already 69480a761fdSTejun Heo * a mixed merge, mark both as mixed before proceeding. This 69580a761fdSTejun Heo * makes sure that all involved bios have mixable attributes 69680a761fdSTejun Heo * set properly. 69780a761fdSTejun Heo */ 698e8064021SChristoph Hellwig if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) || 69980a761fdSTejun Heo (req->cmd_flags & REQ_FAILFAST_MASK) != 70080a761fdSTejun Heo (next->cmd_flags & REQ_FAILFAST_MASK)) { 70180a761fdSTejun Heo blk_rq_set_mixed_merge(req); 70280a761fdSTejun Heo blk_rq_set_mixed_merge(next); 70380a761fdSTejun Heo } 70480a761fdSTejun Heo 70580a761fdSTejun Heo /* 706d6d48196SJens Axboe * At this point we have either done a back merge 707d6d48196SJens Axboe * or front merge. We need the smaller start_time of 708d6d48196SJens Axboe * the merged requests to be the current request 709d6d48196SJens Axboe * for accounting purposes. 710d6d48196SJens Axboe */ 711d6d48196SJens Axboe if (time_after(req->start_time, next->start_time)) 712d6d48196SJens Axboe req->start_time = next->start_time; 713d6d48196SJens Axboe 714d6d48196SJens Axboe req->biotail->bi_next = next->bio; 715d6d48196SJens Axboe req->biotail = next->biotail; 716d6d48196SJens Axboe 717a2dec7b3STejun Heo req->__data_len += blk_rq_bytes(next); 718d6d48196SJens Axboe 719d6d48196SJens Axboe elv_merge_requests(q, req, next); 720d6d48196SJens Axboe 72142dad764SJerome Marchand /* 72242dad764SJerome Marchand * 'next' is going away, so update stats accordingly 72342dad764SJerome Marchand */ 72442dad764SJerome Marchand blk_account_io_merge(next); 725d6d48196SJens Axboe 726d6d48196SJens Axboe req->ioprio = ioprio_best(req->ioprio, next->ioprio); 727ab780f1eSJens Axboe if (blk_rq_cpu_valid(next)) 728ab780f1eSJens Axboe req->cpu = next->cpu; 729d6d48196SJens Axboe 730e4d750c9SJens Axboe /* 731e4d750c9SJens Axboe * ownership of bio passed from next to req, return 'next' for 732e4d750c9SJens Axboe * the caller to free 733e4d750c9SJens Axboe */ 7341cd96c24SBoaz Harrosh next->bio = NULL; 735b973cb7eSJens Axboe return next; 736d6d48196SJens Axboe } 737d6d48196SJens Axboe 738b973cb7eSJens Axboe struct request *attempt_back_merge(struct request_queue *q, struct request *rq) 739d6d48196SJens Axboe { 740d6d48196SJens Axboe struct request *next = elv_latter_request(q, rq); 741d6d48196SJens Axboe 742d6d48196SJens Axboe if (next) 743d6d48196SJens Axboe return attempt_merge(q, rq, next); 744d6d48196SJens Axboe 745b973cb7eSJens Axboe return NULL; 746d6d48196SJens Axboe } 747d6d48196SJens Axboe 748b973cb7eSJens Axboe struct request *attempt_front_merge(struct request_queue *q, struct request *rq) 749d6d48196SJens Axboe { 750d6d48196SJens Axboe struct request *prev = elv_former_request(q, rq); 751d6d48196SJens Axboe 752d6d48196SJens Axboe if (prev) 753d6d48196SJens Axboe return attempt_merge(q, prev, rq); 754d6d48196SJens Axboe 755b973cb7eSJens Axboe return NULL; 756d6d48196SJens Axboe } 7575e84ea3aSJens Axboe 7585e84ea3aSJens Axboe int blk_attempt_req_merge(struct request_queue *q, struct request *rq, 7595e84ea3aSJens Axboe struct request *next) 7605e84ea3aSJens Axboe { 76172ef799bSTahsin Erdogan struct elevator_queue *e = q->elevator; 762e4d750c9SJens Axboe struct request *free; 76372ef799bSTahsin Erdogan 764bd166ef1SJens Axboe if (!e->uses_mq && e->type->ops.sq.elevator_allow_rq_merge_fn) 765c51ca6cfSJens Axboe if (!e->type->ops.sq.elevator_allow_rq_merge_fn(q, rq, next)) 76672ef799bSTahsin Erdogan return 0; 76772ef799bSTahsin Erdogan 768e4d750c9SJens Axboe free = attempt_merge(q, rq, next); 769e4d750c9SJens Axboe if (free) { 770e4d750c9SJens Axboe __blk_put_request(q, free); 771e4d750c9SJens Axboe return 1; 772e4d750c9SJens Axboe } 773e4d750c9SJens Axboe 774e4d750c9SJens Axboe return 0; 7755e84ea3aSJens Axboe } 776050c8ea8STejun Heo 777050c8ea8STejun Heo bool blk_rq_merge_ok(struct request *rq, struct bio *bio) 778050c8ea8STejun Heo { 779e2a60da7SMartin K. Petersen if (!rq_mergeable(rq) || !bio_mergeable(bio)) 780050c8ea8STejun Heo return false; 781050c8ea8STejun Heo 782288dab8aSChristoph Hellwig if (req_op(rq) != bio_op(bio)) 783f31dc1cdSMartin K. Petersen return false; 784f31dc1cdSMartin K. Petersen 785050c8ea8STejun Heo /* different data direction or already started, don't merge */ 786050c8ea8STejun Heo if (bio_data_dir(bio) != rq_data_dir(rq)) 787050c8ea8STejun Heo return false; 788050c8ea8STejun Heo 789050c8ea8STejun Heo /* must be same device and not a special request */ 79074d46992SChristoph Hellwig if (rq->rq_disk != bio->bi_disk || req_no_special_merge(rq)) 791050c8ea8STejun Heo return false; 792050c8ea8STejun Heo 793050c8ea8STejun Heo /* only merge integrity protected bio into ditto rq */ 7944eaf99beSMartin K. Petersen if (blk_integrity_merge_bio(rq->q, rq, bio) == false) 795050c8ea8STejun Heo return false; 796050c8ea8STejun Heo 7974363ac7cSMartin K. Petersen /* must be using the same buffer */ 7988fe0d473SMike Christie if (req_op(rq) == REQ_OP_WRITE_SAME && 7994363ac7cSMartin K. Petersen !blk_write_same_mergeable(rq->bio, bio)) 8004363ac7cSMartin K. Petersen return false; 8014363ac7cSMartin K. Petersen 802cb6934f8SJens Axboe /* 803cb6934f8SJens Axboe * Don't allow merge of different write hints, or for a hint with 804cb6934f8SJens Axboe * non-hint IO. 805cb6934f8SJens Axboe */ 806cb6934f8SJens Axboe if (rq->write_hint != bio->bi_write_hint) 807cb6934f8SJens Axboe return false; 808cb6934f8SJens Axboe 809050c8ea8STejun Heo return true; 810050c8ea8STejun Heo } 811050c8ea8STejun Heo 81234fe7c05SChristoph Hellwig enum elv_merge blk_try_merge(struct request *rq, struct bio *bio) 813050c8ea8STejun Heo { 8141e739730SChristoph Hellwig if (req_op(rq) == REQ_OP_DISCARD && 8151e739730SChristoph Hellwig queue_max_discard_segments(rq->q) > 1) 8161e739730SChristoph Hellwig return ELEVATOR_DISCARD_MERGE; 8171e739730SChristoph Hellwig else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) 818050c8ea8STejun Heo return ELEVATOR_BACK_MERGE; 8194f024f37SKent Overstreet else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) 820050c8ea8STejun Heo return ELEVATOR_FRONT_MERGE; 821050c8ea8STejun Heo return ELEVATOR_NO_MERGE; 822050c8ea8STejun Heo } 823