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> 9fe45e630SChristoph Hellwig #include <linux/blk-integrity.h> 10d6d48196SJens Axboe #include <linux/scatterlist.h> 11d6d48196SJens Axboe 12cda22646SMike Krinkin #include <trace/events/block.h> 13cda22646SMike Krinkin 14d6d48196SJens Axboe #include "blk.h" 158e756373SBaolin Wang #include "blk-rq-qos.h" 16*a7b36ee6SJens Axboe #include "blk-throttle.h" 17d6d48196SJens Axboe 18e9907009SChristoph Hellwig static inline bool bio_will_gap(struct request_queue *q, 19e9907009SChristoph Hellwig struct request *prev_rq, struct bio *prev, struct bio *next) 20e9907009SChristoph Hellwig { 21e9907009SChristoph Hellwig struct bio_vec pb, nb; 22e9907009SChristoph Hellwig 23e9907009SChristoph Hellwig if (!bio_has_data(prev) || !queue_virt_boundary(q)) 24e9907009SChristoph Hellwig return false; 25e9907009SChristoph Hellwig 26e9907009SChristoph Hellwig /* 27e9907009SChristoph Hellwig * Don't merge if the 1st bio starts with non-zero offset, otherwise it 28e9907009SChristoph Hellwig * is quite difficult to respect the sg gap limit. We work hard to 29e9907009SChristoph Hellwig * merge a huge number of small single bios in case of mkfs. 30e9907009SChristoph Hellwig */ 31e9907009SChristoph Hellwig if (prev_rq) 32e9907009SChristoph Hellwig bio_get_first_bvec(prev_rq->bio, &pb); 33e9907009SChristoph Hellwig else 34e9907009SChristoph Hellwig bio_get_first_bvec(prev, &pb); 35df376b2eSJohannes Thumshirn if (pb.bv_offset & queue_virt_boundary(q)) 36e9907009SChristoph Hellwig return true; 37e9907009SChristoph Hellwig 38e9907009SChristoph Hellwig /* 39e9907009SChristoph Hellwig * We don't need to worry about the situation that the merged segment 40e9907009SChristoph Hellwig * ends in unaligned virt boundary: 41e9907009SChristoph Hellwig * 42e9907009SChristoph Hellwig * - if 'pb' ends aligned, the merged segment ends aligned 43e9907009SChristoph Hellwig * - if 'pb' ends unaligned, the next bio must include 44e9907009SChristoph Hellwig * one single bvec of 'nb', otherwise the 'nb' can't 45e9907009SChristoph Hellwig * merge with 'pb' 46e9907009SChristoph Hellwig */ 47e9907009SChristoph Hellwig bio_get_last_bvec(prev, &pb); 48e9907009SChristoph Hellwig bio_get_first_bvec(next, &nb); 49200a9affSChristoph Hellwig if (biovec_phys_mergeable(q, &pb, &nb)) 50e9907009SChristoph Hellwig return false; 51e9907009SChristoph Hellwig return __bvec_gap_to_prev(q, &pb, nb.bv_offset); 52e9907009SChristoph Hellwig } 53e9907009SChristoph Hellwig 54e9907009SChristoph Hellwig static inline bool req_gap_back_merge(struct request *req, struct bio *bio) 55e9907009SChristoph Hellwig { 56e9907009SChristoph Hellwig return bio_will_gap(req->q, req, req->biotail, bio); 57e9907009SChristoph Hellwig } 58e9907009SChristoph Hellwig 59e9907009SChristoph Hellwig static inline bool req_gap_front_merge(struct request *req, struct bio *bio) 60e9907009SChristoph Hellwig { 61e9907009SChristoph Hellwig return bio_will_gap(req->q, NULL, bio, req->bio); 62e9907009SChristoph Hellwig } 63e9907009SChristoph Hellwig 6454efd50bSKent Overstreet static struct bio *blk_bio_discard_split(struct request_queue *q, 6554efd50bSKent Overstreet struct bio *bio, 66bdced438SMing Lei struct bio_set *bs, 67bdced438SMing Lei unsigned *nsegs) 6854efd50bSKent Overstreet { 6954efd50bSKent Overstreet unsigned int max_discard_sectors, granularity; 7054efd50bSKent Overstreet int alignment; 7154efd50bSKent Overstreet sector_t tmp; 7254efd50bSKent Overstreet unsigned split_sectors; 7354efd50bSKent Overstreet 74bdced438SMing Lei *nsegs = 1; 75bdced438SMing Lei 7654efd50bSKent Overstreet /* Zero-sector (unknown) and one-sector granularities are the same. */ 7754efd50bSKent Overstreet granularity = max(q->limits.discard_granularity >> 9, 1U); 7854efd50bSKent Overstreet 791adfc5e4SMing Lei max_discard_sectors = min(q->limits.max_discard_sectors, 801adfc5e4SMing Lei bio_allowed_max_sectors(q)); 8154efd50bSKent Overstreet max_discard_sectors -= max_discard_sectors % granularity; 8254efd50bSKent Overstreet 8354efd50bSKent Overstreet if (unlikely(!max_discard_sectors)) { 8454efd50bSKent Overstreet /* XXX: warn */ 8554efd50bSKent Overstreet return NULL; 8654efd50bSKent Overstreet } 8754efd50bSKent Overstreet 8854efd50bSKent Overstreet if (bio_sectors(bio) <= max_discard_sectors) 8954efd50bSKent Overstreet return NULL; 9054efd50bSKent Overstreet 9154efd50bSKent Overstreet split_sectors = max_discard_sectors; 9254efd50bSKent Overstreet 9354efd50bSKent Overstreet /* 9454efd50bSKent Overstreet * If the next starting sector would be misaligned, stop the discard at 9554efd50bSKent Overstreet * the previous aligned sector. 9654efd50bSKent Overstreet */ 9754efd50bSKent Overstreet alignment = (q->limits.discard_alignment >> 9) % granularity; 9854efd50bSKent Overstreet 9954efd50bSKent Overstreet tmp = bio->bi_iter.bi_sector + split_sectors - alignment; 10054efd50bSKent Overstreet tmp = sector_div(tmp, granularity); 10154efd50bSKent Overstreet 10254efd50bSKent Overstreet if (split_sectors > tmp) 10354efd50bSKent Overstreet split_sectors -= tmp; 10454efd50bSKent Overstreet 10554efd50bSKent Overstreet return bio_split(bio, split_sectors, GFP_NOIO, bs); 10654efd50bSKent Overstreet } 10754efd50bSKent Overstreet 108885fa13fSChristoph Hellwig static struct bio *blk_bio_write_zeroes_split(struct request_queue *q, 109885fa13fSChristoph Hellwig struct bio *bio, struct bio_set *bs, unsigned *nsegs) 110885fa13fSChristoph Hellwig { 111d665e12aSChristoph Hellwig *nsegs = 0; 112885fa13fSChristoph Hellwig 113885fa13fSChristoph Hellwig if (!q->limits.max_write_zeroes_sectors) 114885fa13fSChristoph Hellwig return NULL; 115885fa13fSChristoph Hellwig 116885fa13fSChristoph Hellwig if (bio_sectors(bio) <= q->limits.max_write_zeroes_sectors) 117885fa13fSChristoph Hellwig return NULL; 118885fa13fSChristoph Hellwig 119885fa13fSChristoph Hellwig return bio_split(bio, q->limits.max_write_zeroes_sectors, GFP_NOIO, bs); 120885fa13fSChristoph Hellwig } 121885fa13fSChristoph Hellwig 12254efd50bSKent Overstreet static struct bio *blk_bio_write_same_split(struct request_queue *q, 12354efd50bSKent Overstreet struct bio *bio, 124bdced438SMing Lei struct bio_set *bs, 125bdced438SMing Lei unsigned *nsegs) 12654efd50bSKent Overstreet { 127bdced438SMing Lei *nsegs = 1; 128bdced438SMing Lei 12954efd50bSKent Overstreet if (!q->limits.max_write_same_sectors) 13054efd50bSKent Overstreet return NULL; 13154efd50bSKent Overstreet 13254efd50bSKent Overstreet if (bio_sectors(bio) <= q->limits.max_write_same_sectors) 13354efd50bSKent Overstreet return NULL; 13454efd50bSKent Overstreet 13554efd50bSKent Overstreet return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs); 13654efd50bSKent Overstreet } 13754efd50bSKent Overstreet 1389cc5169cSBart Van Assche /* 1399cc5169cSBart Van Assche * Return the maximum number of sectors from the start of a bio that may be 1409cc5169cSBart Van Assche * submitted as a single request to a block device. If enough sectors remain, 1419cc5169cSBart Van Assche * align the end to the physical block size. Otherwise align the end to the 1429cc5169cSBart Van Assche * logical block size. This approach minimizes the number of non-aligned 1439cc5169cSBart Van Assche * requests that are submitted to a block device if the start of a bio is not 1449cc5169cSBart Van Assche * aligned to a physical block boundary. 1459cc5169cSBart Van Assche */ 146d0e5fbb0SMing Lei static inline unsigned get_max_io_size(struct request_queue *q, 147d0e5fbb0SMing Lei struct bio *bio) 148d0e5fbb0SMing Lei { 1493ee16db3SMike Snitzer unsigned sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector, 0); 1509cc5169cSBart Van Assche unsigned max_sectors = sectors; 1519cc5169cSBart Van Assche unsigned pbs = queue_physical_block_size(q) >> SECTOR_SHIFT; 1529cc5169cSBart Van Assche unsigned lbs = queue_logical_block_size(q) >> SECTOR_SHIFT; 1539cc5169cSBart Van Assche unsigned start_offset = bio->bi_iter.bi_sector & (pbs - 1); 154d0e5fbb0SMing Lei 1559cc5169cSBart Van Assche max_sectors += start_offset; 1569cc5169cSBart Van Assche max_sectors &= ~(pbs - 1); 1579cc5169cSBart Van Assche if (max_sectors > start_offset) 1589cc5169cSBart Van Assche return max_sectors - start_offset; 159d0e5fbb0SMing Lei 160e4b469c6SKeith Busch return sectors & ~(lbs - 1); 161d0e5fbb0SMing Lei } 162d0e5fbb0SMing Lei 163429120f3SMing Lei static inline unsigned get_max_segment_size(const struct request_queue *q, 164429120f3SMing Lei struct page *start_page, 165429120f3SMing Lei unsigned long offset) 166dcebd755SMing Lei { 167dcebd755SMing Lei unsigned long mask = queue_segment_boundary(q); 168dcebd755SMing Lei 169429120f3SMing Lei offset = mask & (page_to_phys(start_page) + offset); 1704a2f704eSMing Lei 1714a2f704eSMing Lei /* 1724a2f704eSMing Lei * overflow may be triggered in case of zero page physical address 1734a2f704eSMing Lei * on 32bit arch, use queue's max segment size when that happens. 1744a2f704eSMing Lei */ 1754a2f704eSMing Lei return min_not_zero(mask - offset + 1, 1764a2f704eSMing Lei (unsigned long)queue_max_segment_size(q)); 177dcebd755SMing Lei } 178dcebd755SMing Lei 179708b25b3SBart Van Assche /** 180708b25b3SBart Van Assche * bvec_split_segs - verify whether or not a bvec should be split in the middle 181708b25b3SBart Van Assche * @q: [in] request queue associated with the bio associated with @bv 182708b25b3SBart Van Assche * @bv: [in] bvec to examine 183708b25b3SBart Van Assche * @nsegs: [in,out] Number of segments in the bio being built. Incremented 184708b25b3SBart Van Assche * by the number of segments from @bv that may be appended to that 185708b25b3SBart Van Assche * bio without exceeding @max_segs 186708b25b3SBart Van Assche * @sectors: [in,out] Number of sectors in the bio being built. Incremented 187708b25b3SBart Van Assche * by the number of sectors from @bv that may be appended to that 188708b25b3SBart Van Assche * bio without exceeding @max_sectors 189708b25b3SBart Van Assche * @max_segs: [in] upper bound for *@nsegs 190708b25b3SBart Van Assche * @max_sectors: [in] upper bound for *@sectors 191708b25b3SBart Van Assche * 192708b25b3SBart Van Assche * When splitting a bio, it can happen that a bvec is encountered that is too 193708b25b3SBart Van Assche * big to fit in a single segment and hence that it has to be split in the 194708b25b3SBart Van Assche * middle. This function verifies whether or not that should happen. The value 195708b25b3SBart Van Assche * %true is returned if and only if appending the entire @bv to a bio with 196708b25b3SBart Van Assche * *@nsegs segments and *@sectors sectors would make that bio unacceptable for 197708b25b3SBart Van Assche * the block driver. 198dcebd755SMing Lei */ 199af2c68feSBart Van Assche static bool bvec_split_segs(const struct request_queue *q, 200af2c68feSBart Van Assche const struct bio_vec *bv, unsigned *nsegs, 201708b25b3SBart Van Assche unsigned *sectors, unsigned max_segs, 202708b25b3SBart Van Assche unsigned max_sectors) 203dcebd755SMing Lei { 204708b25b3SBart Van Assche unsigned max_len = (min(max_sectors, UINT_MAX >> 9) - *sectors) << 9; 205708b25b3SBart Van Assche unsigned len = min(bv->bv_len, max_len); 206dcebd755SMing Lei unsigned total_len = 0; 207ff9811b3SBart Van Assche unsigned seg_size = 0; 208dcebd755SMing Lei 209ff9811b3SBart Van Assche while (len && *nsegs < max_segs) { 210429120f3SMing Lei seg_size = get_max_segment_size(q, bv->bv_page, 211429120f3SMing Lei bv->bv_offset + total_len); 212dcebd755SMing Lei seg_size = min(seg_size, len); 213dcebd755SMing Lei 214ff9811b3SBart Van Assche (*nsegs)++; 215dcebd755SMing Lei total_len += seg_size; 216dcebd755SMing Lei len -= seg_size; 217dcebd755SMing Lei 218dcebd755SMing Lei if ((bv->bv_offset + total_len) & queue_virt_boundary(q)) 219dcebd755SMing Lei break; 220dcebd755SMing Lei } 221dcebd755SMing Lei 222dcebd755SMing Lei *sectors += total_len >> 9; 223dcebd755SMing Lei 224708b25b3SBart Van Assche /* tell the caller to split the bvec if it is too big to fit */ 225708b25b3SBart Van Assche return len > 0 || bv->bv_len > max_len; 226dcebd755SMing Lei } 227dcebd755SMing Lei 228dad77584SBart Van Assche /** 229dad77584SBart Van Assche * blk_bio_segment_split - split a bio in two bios 230dad77584SBart Van Assche * @q: [in] request queue pointer 231dad77584SBart Van Assche * @bio: [in] bio to be split 232dad77584SBart Van Assche * @bs: [in] bio set to allocate the clone from 233dad77584SBart Van Assche * @segs: [out] number of segments in the bio with the first half of the sectors 234dad77584SBart Van Assche * 235dad77584SBart Van Assche * Clone @bio, update the bi_iter of the clone to represent the first sectors 236dad77584SBart Van Assche * of @bio and update @bio->bi_iter to represent the remaining sectors. The 237dad77584SBart Van Assche * following is guaranteed for the cloned bio: 238dad77584SBart Van Assche * - That it has at most get_max_io_size(@q, @bio) sectors. 239dad77584SBart Van Assche * - That it has at most queue_max_segments(@q) segments. 240dad77584SBart Van Assche * 241dad77584SBart Van Assche * Except for discard requests the cloned bio will point at the bi_io_vec of 242dad77584SBart Van Assche * the original bio. It is the responsibility of the caller to ensure that the 243dad77584SBart Van Assche * original bio is not freed before the cloned bio. The caller is also 244dad77584SBart Van Assche * responsible for ensuring that @bs is only destroyed after processing of the 245dad77584SBart Van Assche * split bio has finished. 246dad77584SBart Van Assche */ 24754efd50bSKent Overstreet static struct bio *blk_bio_segment_split(struct request_queue *q, 24854efd50bSKent Overstreet struct bio *bio, 249bdced438SMing Lei struct bio_set *bs, 250bdced438SMing Lei unsigned *segs) 25154efd50bSKent Overstreet { 2525014c311SJens Axboe struct bio_vec bv, bvprv, *bvprvp = NULL; 25354efd50bSKent Overstreet struct bvec_iter iter; 2546869875fSChristoph Hellwig unsigned nsegs = 0, sectors = 0; 255d0e5fbb0SMing Lei const unsigned max_sectors = get_max_io_size(q, bio); 25605b700baSMing Lei const unsigned max_segs = queue_max_segments(q); 25754efd50bSKent Overstreet 258dcebd755SMing Lei bio_for_each_bvec(bv, bio, iter) { 25954efd50bSKent Overstreet /* 26054efd50bSKent Overstreet * If the queue doesn't support SG gaps and adding this 26154efd50bSKent Overstreet * offset would create a gap, disallow it. 26254efd50bSKent Overstreet */ 2635014c311SJens Axboe if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset)) 26454efd50bSKent Overstreet goto split; 26554efd50bSKent Overstreet 26605b700baSMing Lei if (nsegs < max_segs && 267708b25b3SBart Van Assche sectors + (bv.bv_len >> 9) <= max_sectors && 268708b25b3SBart Van Assche bv.bv_offset + bv.bv_len <= PAGE_SIZE) { 269708b25b3SBart Van Assche nsegs++; 270708b25b3SBart Van Assche sectors += bv.bv_len >> 9; 271708b25b3SBart Van Assche } else if (bvec_split_segs(q, &bv, &nsegs, §ors, max_segs, 272708b25b3SBart Van Assche max_sectors)) { 273e36f6204SKeith Busch goto split; 274e36f6204SKeith Busch } 275e36f6204SKeith Busch 27654efd50bSKent Overstreet bvprv = bv; 277578270bfSMing Lei bvprvp = &bvprv; 27854efd50bSKent Overstreet } 27954efd50bSKent Overstreet 280d627065dSChristoph Hellwig *segs = nsegs; 281d627065dSChristoph Hellwig return NULL; 28254efd50bSKent Overstreet split: 283bdced438SMing Lei *segs = nsegs; 284cc29e1bfSJeffle Xu 285cc29e1bfSJeffle Xu /* 286cc29e1bfSJeffle Xu * Bio splitting may cause subtle trouble such as hang when doing sync 287cc29e1bfSJeffle Xu * iopoll in direct IO routine. Given performance gain of iopoll for 288cc29e1bfSJeffle Xu * big IO can be trival, disable iopoll when split needed. 289cc29e1bfSJeffle Xu */ 290270a1c91SJens Axboe bio_clear_hipri(bio); 291cc29e1bfSJeffle Xu 292d627065dSChristoph Hellwig return bio_split(bio, sectors, GFP_NOIO, bs); 29354efd50bSKent Overstreet } 29454efd50bSKent Overstreet 295dad77584SBart Van Assche /** 296dad77584SBart Van Assche * __blk_queue_split - split a bio and submit the second half 297dad77584SBart Van Assche * @bio: [in, out] bio to be split 298dad77584SBart Van Assche * @nr_segs: [out] number of segments in the first bio 299dad77584SBart Van Assche * 300dad77584SBart Van Assche * Split a bio into two bios, chain the two bios, submit the second half and 301dad77584SBart Van Assche * store a pointer to the first half in *@bio. If the second bio is still too 302dad77584SBart Van Assche * big it will be split by a recursive call to this function. Since this 303309dca30SChristoph Hellwig * function may allocate a new bio from q->bio_split, it is the responsibility 304309dca30SChristoph Hellwig * of the caller to ensure that q->bio_split is only released after processing 305309dca30SChristoph Hellwig * of the split bio has finished. 306dad77584SBart Van Assche */ 307f695ca38SChristoph Hellwig void __blk_queue_split(struct bio **bio, unsigned int *nr_segs) 30854efd50bSKent Overstreet { 309309dca30SChristoph Hellwig struct request_queue *q = (*bio)->bi_bdev->bd_disk->queue; 310fa532287SChristoph Hellwig struct bio *split = NULL; 31154efd50bSKent Overstreet 3127afafc8aSAdrian Hunter switch (bio_op(*bio)) { 3137afafc8aSAdrian Hunter case REQ_OP_DISCARD: 3147afafc8aSAdrian Hunter case REQ_OP_SECURE_ERASE: 31514ccb66bSChristoph Hellwig split = blk_bio_discard_split(q, *bio, &q->bio_split, nr_segs); 3167afafc8aSAdrian Hunter break; 317a6f0788eSChaitanya Kulkarni case REQ_OP_WRITE_ZEROES: 31814ccb66bSChristoph Hellwig split = blk_bio_write_zeroes_split(q, *bio, &q->bio_split, 31914ccb66bSChristoph Hellwig nr_segs); 320a6f0788eSChaitanya Kulkarni break; 3217afafc8aSAdrian Hunter case REQ_OP_WRITE_SAME: 32214ccb66bSChristoph Hellwig split = blk_bio_write_same_split(q, *bio, &q->bio_split, 32314ccb66bSChristoph Hellwig nr_segs); 3247afafc8aSAdrian Hunter break; 3257afafc8aSAdrian Hunter default: 326fa532287SChristoph Hellwig /* 327fa532287SChristoph Hellwig * All drivers must accept single-segments bios that are <= 328fa532287SChristoph Hellwig * PAGE_SIZE. This is a quick and dirty check that relies on 329fa532287SChristoph Hellwig * the fact that bi_io_vec[0] is always valid if a bio has data. 330fa532287SChristoph Hellwig * The check might lead to occasional false negatives when bios 331fa532287SChristoph Hellwig * are cloned, but compared to the performance impact of cloned 332fa532287SChristoph Hellwig * bios themselves the loop below doesn't matter anyway. 333fa532287SChristoph Hellwig */ 334fa532287SChristoph Hellwig if (!q->limits.chunk_sectors && 335fa532287SChristoph Hellwig (*bio)->bi_vcnt == 1 && 33659db8ba2SMing Lei ((*bio)->bi_io_vec[0].bv_len + 3371e279153SJens Axboe (*bio)->bi_io_vec[0].bv_offset) <= PAGE_SIZE) { 338fa532287SChristoph Hellwig *nr_segs = 1; 339fa532287SChristoph Hellwig break; 340fa532287SChristoph Hellwig } 34114ccb66bSChristoph Hellwig split = blk_bio_segment_split(q, *bio, &q->bio_split, nr_segs); 3427afafc8aSAdrian Hunter break; 3437afafc8aSAdrian Hunter } 344bdced438SMing Lei 34554efd50bSKent Overstreet if (split) { 3466ac45aebSMing Lei /* there isn't chance to merge the splitted bio */ 3471eff9d32SJens Axboe split->bi_opf |= REQ_NOMERGE; 3486ac45aebSMing Lei 34954efd50bSKent Overstreet bio_chain(split, *bio); 350eb6f7f7cSChristoph Hellwig trace_block_split(split, (*bio)->bi_iter.bi_sector); 351ed00aabdSChristoph Hellwig submit_bio_noacct(*bio); 35254efd50bSKent Overstreet *bio = split; 3534f1e9630SChunguang Xu 3544f1e9630SChunguang Xu blk_throtl_charge_bio_split(*bio); 35554efd50bSKent Overstreet } 35654efd50bSKent Overstreet } 35714ccb66bSChristoph Hellwig 358dad77584SBart Van Assche /** 359dad77584SBart Van Assche * blk_queue_split - split a bio and submit the second half 360dad77584SBart Van Assche * @bio: [in, out] bio to be split 361dad77584SBart Van Assche * 362dad77584SBart Van Assche * Split a bio into two bios, chains the two bios, submit the second half and 363dad77584SBart Van Assche * store a pointer to the first half in *@bio. Since this function may allocate 364309dca30SChristoph Hellwig * a new bio from q->bio_split, it is the responsibility of the caller to ensure 365309dca30SChristoph Hellwig * that q->bio_split is only released after processing of the split bio has 366309dca30SChristoph Hellwig * finished. 367dad77584SBart Van Assche */ 368f695ca38SChristoph Hellwig void blk_queue_split(struct bio **bio) 36914ccb66bSChristoph Hellwig { 37014ccb66bSChristoph Hellwig unsigned int nr_segs; 37114ccb66bSChristoph Hellwig 372f695ca38SChristoph Hellwig __blk_queue_split(bio, &nr_segs); 37314ccb66bSChristoph Hellwig } 37454efd50bSKent Overstreet EXPORT_SYMBOL(blk_queue_split); 37554efd50bSKent Overstreet 376e9cd19c0SChristoph Hellwig unsigned int blk_recalc_rq_segments(struct request *rq) 377d6d48196SJens Axboe { 3786869875fSChristoph Hellwig unsigned int nr_phys_segs = 0; 379ff9811b3SBart Van Assche unsigned int nr_sectors = 0; 380e9cd19c0SChristoph Hellwig struct req_iterator iter; 3816869875fSChristoph Hellwig struct bio_vec bv; 382d6d48196SJens Axboe 383e9cd19c0SChristoph Hellwig if (!rq->bio) 3841e428079SJens Axboe return 0; 385d6d48196SJens Axboe 386e9cd19c0SChristoph Hellwig switch (bio_op(rq->bio)) { 387a6f0788eSChaitanya Kulkarni case REQ_OP_DISCARD: 388a6f0788eSChaitanya Kulkarni case REQ_OP_SECURE_ERASE: 389a958937fSDavid Jeffery if (queue_max_discard_segments(rq->q) > 1) { 390a958937fSDavid Jeffery struct bio *bio = rq->bio; 391a958937fSDavid Jeffery 392a958937fSDavid Jeffery for_each_bio(bio) 393a958937fSDavid Jeffery nr_phys_segs++; 394a958937fSDavid Jeffery return nr_phys_segs; 395a958937fSDavid Jeffery } 396a958937fSDavid Jeffery return 1; 397a6f0788eSChaitanya Kulkarni case REQ_OP_WRITE_ZEROES: 398f9d03f96SChristoph Hellwig return 0; 399f9d03f96SChristoph Hellwig case REQ_OP_WRITE_SAME: 4005cb8850cSKent Overstreet return 1; 401a6f0788eSChaitanya Kulkarni } 4025cb8850cSKent Overstreet 403e9cd19c0SChristoph Hellwig rq_for_each_bvec(bv, rq, iter) 404ff9811b3SBart Van Assche bvec_split_segs(rq->q, &bv, &nr_phys_segs, &nr_sectors, 405708b25b3SBart Van Assche UINT_MAX, UINT_MAX); 4061e428079SJens Axboe return nr_phys_segs; 4071e428079SJens Axboe } 4081e428079SJens Axboe 40948d7727cSMing Lei static inline struct scatterlist *blk_next_sg(struct scatterlist **sg, 410862e5a5eSMing Lei struct scatterlist *sglist) 411862e5a5eSMing Lei { 412862e5a5eSMing Lei if (!*sg) 413862e5a5eSMing Lei return sglist; 414862e5a5eSMing Lei 415862e5a5eSMing Lei /* 416862e5a5eSMing Lei * If the driver previously mapped a shorter list, we could see a 417862e5a5eSMing Lei * termination bit prematurely unless it fully inits the sg table 418862e5a5eSMing Lei * on each mapping. We KNOW that there must be more entries here 419862e5a5eSMing Lei * or the driver would be buggy, so force clear the termination bit 420862e5a5eSMing Lei * to avoid doing a full sg_init_table() in drivers for each command. 421862e5a5eSMing Lei */ 422862e5a5eSMing Lei sg_unmark_end(*sg); 423862e5a5eSMing Lei return sg_next(*sg); 424862e5a5eSMing Lei } 425862e5a5eSMing Lei 426862e5a5eSMing Lei static unsigned blk_bvec_map_sg(struct request_queue *q, 427862e5a5eSMing Lei struct bio_vec *bvec, struct scatterlist *sglist, 428862e5a5eSMing Lei struct scatterlist **sg) 429862e5a5eSMing Lei { 430862e5a5eSMing Lei unsigned nbytes = bvec->bv_len; 4318a96a0e4SChristoph Hellwig unsigned nsegs = 0, total = 0; 432862e5a5eSMing Lei 433862e5a5eSMing Lei while (nbytes > 0) { 4348a96a0e4SChristoph Hellwig unsigned offset = bvec->bv_offset + total; 435429120f3SMing Lei unsigned len = min(get_max_segment_size(q, bvec->bv_page, 436429120f3SMing Lei offset), nbytes); 437f9f76879SChristoph Hellwig struct page *page = bvec->bv_page; 438f9f76879SChristoph Hellwig 439f9f76879SChristoph Hellwig /* 440f9f76879SChristoph Hellwig * Unfortunately a fair number of drivers barf on scatterlists 441f9f76879SChristoph Hellwig * that have an offset larger than PAGE_SIZE, despite other 442f9f76879SChristoph Hellwig * subsystems dealing with that invariant just fine. For now 443f9f76879SChristoph Hellwig * stick to the legacy format where we never present those from 444f9f76879SChristoph Hellwig * the block layer, but the code below should be removed once 445f9f76879SChristoph Hellwig * these offenders (mostly MMC/SD drivers) are fixed. 446f9f76879SChristoph Hellwig */ 447f9f76879SChristoph Hellwig page += (offset >> PAGE_SHIFT); 448f9f76879SChristoph Hellwig offset &= ~PAGE_MASK; 449862e5a5eSMing Lei 450862e5a5eSMing Lei *sg = blk_next_sg(sg, sglist); 451f9f76879SChristoph Hellwig sg_set_page(*sg, page, len, offset); 452862e5a5eSMing Lei 4538a96a0e4SChristoph Hellwig total += len; 4548a96a0e4SChristoph Hellwig nbytes -= len; 455862e5a5eSMing Lei nsegs++; 456862e5a5eSMing Lei } 457862e5a5eSMing Lei 458862e5a5eSMing Lei return nsegs; 459862e5a5eSMing Lei } 460862e5a5eSMing Lei 46116e3e418SMing Lei static inline int __blk_bvec_map_sg(struct bio_vec bv, 46216e3e418SMing Lei struct scatterlist *sglist, struct scatterlist **sg) 46316e3e418SMing Lei { 46416e3e418SMing Lei *sg = blk_next_sg(sg, sglist); 46516e3e418SMing Lei sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset); 46616e3e418SMing Lei return 1; 46716e3e418SMing Lei } 46816e3e418SMing Lei 469f6970f83SMing Lei /* only try to merge bvecs into one sg if they are from two bios */ 470f6970f83SMing Lei static inline bool 471f6970f83SMing Lei __blk_segment_map_sg_merge(struct request_queue *q, struct bio_vec *bvec, 472f6970f83SMing Lei struct bio_vec *bvprv, struct scatterlist **sg) 473963ab9e5SAsias He { 474963ab9e5SAsias He 475963ab9e5SAsias He int nbytes = bvec->bv_len; 476963ab9e5SAsias He 477f6970f83SMing Lei if (!*sg) 478f6970f83SMing Lei return false; 479f6970f83SMing Lei 480b4b6cb61SMing Lei if ((*sg)->length + nbytes > queue_max_segment_size(q)) 481f6970f83SMing Lei return false; 482f6970f83SMing Lei 4833dccdae5SChristoph Hellwig if (!biovec_phys_mergeable(q, bvprv, bvec)) 484f6970f83SMing Lei return false; 485963ab9e5SAsias He 486963ab9e5SAsias He (*sg)->length += nbytes; 487f6970f83SMing Lei 488f6970f83SMing Lei return true; 489963ab9e5SAsias He } 490963ab9e5SAsias He 4915cb8850cSKent Overstreet static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, 4925cb8850cSKent Overstreet struct scatterlist *sglist, 4935cb8850cSKent Overstreet struct scatterlist **sg) 4945cb8850cSKent Overstreet { 4953f649ab7SKees Cook struct bio_vec bvec, bvprv = { NULL }; 4965cb8850cSKent Overstreet struct bvec_iter iter; 49738417468SChristoph Hellwig int nsegs = 0; 498f6970f83SMing Lei bool new_bio = false; 4995cb8850cSKent Overstreet 500f6970f83SMing Lei for_each_bio(bio) { 501f6970f83SMing Lei bio_for_each_bvec(bvec, bio, iter) { 502f6970f83SMing Lei /* 503f6970f83SMing Lei * Only try to merge bvecs from two bios given we 504f6970f83SMing Lei * have done bio internal merge when adding pages 505f6970f83SMing Lei * to bio 506f6970f83SMing Lei */ 507f6970f83SMing Lei if (new_bio && 508f6970f83SMing Lei __blk_segment_map_sg_merge(q, &bvec, &bvprv, sg)) 509f6970f83SMing Lei goto next_bvec; 510f6970f83SMing Lei 511f6970f83SMing Lei if (bvec.bv_offset + bvec.bv_len <= PAGE_SIZE) 512f6970f83SMing Lei nsegs += __blk_bvec_map_sg(bvec, sglist, sg); 513f6970f83SMing Lei else 514f6970f83SMing Lei nsegs += blk_bvec_map_sg(q, &bvec, sglist, sg); 515f6970f83SMing Lei next_bvec: 516f6970f83SMing Lei new_bio = false; 517f6970f83SMing Lei } 518b21e11c5SMing Lei if (likely(bio->bi_iter.bi_size)) { 519f6970f83SMing Lei bvprv = bvec; 520f6970f83SMing Lei new_bio = true; 521f6970f83SMing Lei } 522b21e11c5SMing Lei } 5235cb8850cSKent Overstreet 5245cb8850cSKent Overstreet return nsegs; 5255cb8850cSKent Overstreet } 5265cb8850cSKent Overstreet 527d6d48196SJens Axboe /* 528d6d48196SJens Axboe * map a request to scatterlist, return number of sg entries setup. Caller 529d6d48196SJens Axboe * must make sure sg can hold rq->nr_phys_segments entries 530d6d48196SJens Axboe */ 53189de1504SChristoph Hellwig int __blk_rq_map_sg(struct request_queue *q, struct request *rq, 53289de1504SChristoph Hellwig struct scatterlist *sglist, struct scatterlist **last_sg) 533d6d48196SJens Axboe { 5345cb8850cSKent Overstreet int nsegs = 0; 535d6d48196SJens Axboe 536f9d03f96SChristoph Hellwig if (rq->rq_flags & RQF_SPECIAL_PAYLOAD) 53789de1504SChristoph Hellwig nsegs = __blk_bvec_map_sg(rq->special_vec, sglist, last_sg); 538f9d03f96SChristoph Hellwig else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME) 53989de1504SChristoph Hellwig nsegs = __blk_bvec_map_sg(bio_iovec(rq->bio), sglist, last_sg); 540f9d03f96SChristoph Hellwig else if (rq->bio) 54189de1504SChristoph Hellwig nsegs = __blk_bios_map_sg(q, rq->bio, sglist, last_sg); 542f18573abSFUJITA Tomonori 54389de1504SChristoph Hellwig if (*last_sg) 54489de1504SChristoph Hellwig sg_mark_end(*last_sg); 545d6d48196SJens Axboe 54612e57f59SMing Lei /* 54712e57f59SMing Lei * Something must have been wrong if the figured number of 54812e57f59SMing Lei * segment is bigger than number of req's physical segments 54912e57f59SMing Lei */ 550f9d03f96SChristoph Hellwig WARN_ON(nsegs > blk_rq_nr_phys_segments(rq)); 55112e57f59SMing Lei 552d6d48196SJens Axboe return nsegs; 553d6d48196SJens Axboe } 55489de1504SChristoph Hellwig EXPORT_SYMBOL(__blk_rq_map_sg); 555d6d48196SJens Axboe 556943b40c8SMing Lei static inline unsigned int blk_rq_get_max_segments(struct request *rq) 557943b40c8SMing Lei { 558943b40c8SMing Lei if (req_op(rq) == REQ_OP_DISCARD) 559943b40c8SMing Lei return queue_max_discard_segments(rq->q); 560943b40c8SMing Lei return queue_max_segments(rq->q); 561943b40c8SMing Lei } 562943b40c8SMing Lei 563badf7f64SChristoph Hellwig static inline unsigned int blk_rq_get_max_sectors(struct request *rq, 564badf7f64SChristoph Hellwig sector_t offset) 565badf7f64SChristoph Hellwig { 566badf7f64SChristoph Hellwig struct request_queue *q = rq->q; 567badf7f64SChristoph Hellwig 568badf7f64SChristoph Hellwig if (blk_rq_is_passthrough(rq)) 569badf7f64SChristoph Hellwig return q->limits.max_hw_sectors; 570badf7f64SChristoph Hellwig 571badf7f64SChristoph Hellwig if (!q->limits.chunk_sectors || 572badf7f64SChristoph Hellwig req_op(rq) == REQ_OP_DISCARD || 573badf7f64SChristoph Hellwig req_op(rq) == REQ_OP_SECURE_ERASE) 574badf7f64SChristoph Hellwig return blk_queue_get_max_sectors(q, req_op(rq)); 575badf7f64SChristoph Hellwig 576badf7f64SChristoph Hellwig return min(blk_max_size_offset(q, offset, 0), 577badf7f64SChristoph Hellwig blk_queue_get_max_sectors(q, req_op(rq))); 578badf7f64SChristoph Hellwig } 579badf7f64SChristoph Hellwig 58014ccb66bSChristoph Hellwig static inline int ll_new_hw_segment(struct request *req, struct bio *bio, 58114ccb66bSChristoph Hellwig unsigned int nr_phys_segs) 582d6d48196SJens Axboe { 5832705dfb2SMing Lei if (blk_integrity_merge_bio(req->q, req, bio) == false) 58413f05c8dSMartin K. Petersen goto no_merge; 58513f05c8dSMartin K. Petersen 5862705dfb2SMing Lei /* discard request merge won't add new segment */ 5872705dfb2SMing Lei if (req_op(req) == REQ_OP_DISCARD) 5882705dfb2SMing Lei return 1; 5892705dfb2SMing Lei 5902705dfb2SMing Lei if (req->nr_phys_segments + nr_phys_segs > blk_rq_get_max_segments(req)) 59113f05c8dSMartin K. Petersen goto no_merge; 592d6d48196SJens Axboe 593d6d48196SJens Axboe /* 594d6d48196SJens Axboe * This will form the start of a new hw segment. Bump both 595d6d48196SJens Axboe * counters. 596d6d48196SJens Axboe */ 597d6d48196SJens Axboe req->nr_phys_segments += nr_phys_segs; 598d6d48196SJens Axboe return 1; 59913f05c8dSMartin K. Petersen 60013f05c8dSMartin K. Petersen no_merge: 60114ccb66bSChristoph Hellwig req_set_nomerge(req->q, req); 60213f05c8dSMartin K. Petersen return 0; 603d6d48196SJens Axboe } 604d6d48196SJens Axboe 60514ccb66bSChristoph Hellwig int ll_back_merge_fn(struct request *req, struct bio *bio, unsigned int nr_segs) 606d6d48196SJens Axboe { 6075e7c4274SJens Axboe if (req_gap_back_merge(req, bio)) 6085e7c4274SJens Axboe return 0; 6097f39add3SSagi Grimberg if (blk_integrity_rq(req) && 6107f39add3SSagi Grimberg integrity_req_gap_back_merge(req, bio)) 6117f39add3SSagi Grimberg return 0; 612a892c8d5SSatya Tangirala if (!bio_crypt_ctx_back_mergeable(req, bio)) 613a892c8d5SSatya Tangirala return 0; 614f31dc1cdSMartin K. Petersen if (blk_rq_sectors(req) + bio_sectors(bio) > 61517007f39SDamien Le Moal blk_rq_get_max_sectors(req, blk_rq_pos(req))) { 61614ccb66bSChristoph Hellwig req_set_nomerge(req->q, req); 617d6d48196SJens Axboe return 0; 618d6d48196SJens Axboe } 619d6d48196SJens Axboe 62014ccb66bSChristoph Hellwig return ll_new_hw_segment(req, bio, nr_segs); 621d6d48196SJens Axboe } 622d6d48196SJens Axboe 623eda5cc99SChristoph Hellwig static int ll_front_merge_fn(struct request *req, struct bio *bio, 624eda5cc99SChristoph Hellwig unsigned int nr_segs) 625d6d48196SJens Axboe { 6265e7c4274SJens Axboe if (req_gap_front_merge(req, bio)) 6275e7c4274SJens Axboe return 0; 6287f39add3SSagi Grimberg if (blk_integrity_rq(req) && 6297f39add3SSagi Grimberg integrity_req_gap_front_merge(req, bio)) 6307f39add3SSagi Grimberg return 0; 631a892c8d5SSatya Tangirala if (!bio_crypt_ctx_front_mergeable(req, bio)) 632a892c8d5SSatya Tangirala return 0; 633f31dc1cdSMartin K. Petersen if (blk_rq_sectors(req) + bio_sectors(bio) > 63417007f39SDamien Le Moal blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) { 63514ccb66bSChristoph Hellwig req_set_nomerge(req->q, req); 636d6d48196SJens Axboe return 0; 637d6d48196SJens Axboe } 638d6d48196SJens Axboe 63914ccb66bSChristoph Hellwig return ll_new_hw_segment(req, bio, nr_segs); 640d6d48196SJens Axboe } 641d6d48196SJens Axboe 642445251d0SJens Axboe static bool req_attempt_discard_merge(struct request_queue *q, struct request *req, 643445251d0SJens Axboe struct request *next) 644445251d0SJens Axboe { 645445251d0SJens Axboe unsigned short segments = blk_rq_nr_discard_segments(req); 646445251d0SJens Axboe 647445251d0SJens Axboe if (segments >= queue_max_discard_segments(q)) 648445251d0SJens Axboe goto no_merge; 649445251d0SJens Axboe if (blk_rq_sectors(req) + bio_sectors(next->bio) > 650445251d0SJens Axboe blk_rq_get_max_sectors(req, blk_rq_pos(req))) 651445251d0SJens Axboe goto no_merge; 652445251d0SJens Axboe 653445251d0SJens Axboe req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next); 654445251d0SJens Axboe return true; 655445251d0SJens Axboe no_merge: 656445251d0SJens Axboe req_set_nomerge(q, req); 657445251d0SJens Axboe return false; 658445251d0SJens Axboe } 659445251d0SJens Axboe 660d6d48196SJens Axboe static int ll_merge_requests_fn(struct request_queue *q, struct request *req, 661d6d48196SJens Axboe struct request *next) 662d6d48196SJens Axboe { 663d6d48196SJens Axboe int total_phys_segments; 664d6d48196SJens Axboe 6655e7c4274SJens Axboe if (req_gap_back_merge(req, next->bio)) 666854fbb9cSKeith Busch return 0; 667854fbb9cSKeith Busch 668d6d48196SJens Axboe /* 669d6d48196SJens Axboe * Will it become too large? 670d6d48196SJens Axboe */ 671f31dc1cdSMartin K. Petersen if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > 67217007f39SDamien Le Moal blk_rq_get_max_sectors(req, blk_rq_pos(req))) 673d6d48196SJens Axboe return 0; 674d6d48196SJens Axboe 675d6d48196SJens Axboe total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; 676943b40c8SMing Lei if (total_phys_segments > blk_rq_get_max_segments(req)) 677d6d48196SJens Axboe return 0; 678d6d48196SJens Axboe 6794eaf99beSMartin K. Petersen if (blk_integrity_merge_rq(q, req, next) == false) 68013f05c8dSMartin K. Petersen return 0; 68113f05c8dSMartin K. Petersen 682a892c8d5SSatya Tangirala if (!bio_crypt_ctx_merge_rq(req, next)) 683a892c8d5SSatya Tangirala return 0; 684a892c8d5SSatya Tangirala 685d6d48196SJens Axboe /* Merge is OK... */ 686d6d48196SJens Axboe req->nr_phys_segments = total_phys_segments; 687d6d48196SJens Axboe return 1; 688d6d48196SJens Axboe } 689d6d48196SJens Axboe 69080a761fdSTejun Heo /** 69180a761fdSTejun Heo * blk_rq_set_mixed_merge - mark a request as mixed merge 69280a761fdSTejun Heo * @rq: request to mark as mixed merge 69380a761fdSTejun Heo * 69480a761fdSTejun Heo * Description: 69580a761fdSTejun Heo * @rq is about to be mixed merged. Make sure the attributes 69680a761fdSTejun Heo * which can be mixed are set in each bio and mark @rq as mixed 69780a761fdSTejun Heo * merged. 69880a761fdSTejun Heo */ 69980a761fdSTejun Heo void blk_rq_set_mixed_merge(struct request *rq) 70080a761fdSTejun Heo { 70180a761fdSTejun Heo unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK; 70280a761fdSTejun Heo struct bio *bio; 70380a761fdSTejun Heo 704e8064021SChristoph Hellwig if (rq->rq_flags & RQF_MIXED_MERGE) 70580a761fdSTejun Heo return; 70680a761fdSTejun Heo 70780a761fdSTejun Heo /* 70880a761fdSTejun Heo * @rq will no longer represent mixable attributes for all the 70980a761fdSTejun Heo * contained bios. It will just track those of the first one. 71080a761fdSTejun Heo * Distributes the attributs to each bio. 71180a761fdSTejun Heo */ 71280a761fdSTejun Heo for (bio = rq->bio; bio; bio = bio->bi_next) { 7131eff9d32SJens Axboe WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) && 7141eff9d32SJens Axboe (bio->bi_opf & REQ_FAILFAST_MASK) != ff); 7151eff9d32SJens Axboe bio->bi_opf |= ff; 71680a761fdSTejun Heo } 717e8064021SChristoph Hellwig rq->rq_flags |= RQF_MIXED_MERGE; 71880a761fdSTejun Heo } 71980a761fdSTejun Heo 720b9c54f56SKonstantin Khlebnikov static void blk_account_io_merge_request(struct request *req) 72126308eabSJerome Marchand { 72226308eabSJerome Marchand if (blk_do_io_stat(req)) { 723112f158fSMike Snitzer part_stat_lock(); 724b9c54f56SKonstantin Khlebnikov part_stat_inc(req->part, merges[op_stat_group(req_op(req))]); 72526308eabSJerome Marchand part_stat_unlock(); 72626308eabSJerome Marchand } 72726308eabSJerome Marchand } 728b9c54f56SKonstantin Khlebnikov 729e96c0d83SEric Biggers static enum elv_merge blk_try_req_merge(struct request *req, 730e96c0d83SEric Biggers struct request *next) 73169840466SJianchao Wang { 73269840466SJianchao Wang if (blk_discard_mergable(req)) 73369840466SJianchao Wang return ELEVATOR_DISCARD_MERGE; 73469840466SJianchao Wang else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next)) 73569840466SJianchao Wang return ELEVATOR_BACK_MERGE; 73669840466SJianchao Wang 73769840466SJianchao Wang return ELEVATOR_NO_MERGE; 73869840466SJianchao Wang } 73926308eabSJerome Marchand 740badf7f64SChristoph Hellwig static inline bool blk_write_same_mergeable(struct bio *a, struct bio *b) 741badf7f64SChristoph Hellwig { 742badf7f64SChristoph Hellwig if (bio_page(a) == bio_page(b) && bio_offset(a) == bio_offset(b)) 743badf7f64SChristoph Hellwig return true; 744badf7f64SChristoph Hellwig return false; 745badf7f64SChristoph Hellwig } 746badf7f64SChristoph Hellwig 747d6d48196SJens Axboe /* 748b973cb7eSJens Axboe * For non-mq, this has to be called with the request spinlock acquired. 749b973cb7eSJens Axboe * For mq with scheduling, the appropriate queue wide lock should be held. 750d6d48196SJens Axboe */ 751b973cb7eSJens Axboe static struct request *attempt_merge(struct request_queue *q, 752b973cb7eSJens Axboe struct request *req, struct request *next) 753d6d48196SJens Axboe { 754d6d48196SJens Axboe if (!rq_mergeable(req) || !rq_mergeable(next)) 755b973cb7eSJens Axboe return NULL; 756d6d48196SJens Axboe 757288dab8aSChristoph Hellwig if (req_op(req) != req_op(next)) 758b973cb7eSJens Axboe return NULL; 759f31dc1cdSMartin K. Petersen 760d6d48196SJens Axboe if (rq_data_dir(req) != rq_data_dir(next) 7612081a56bSJens Axboe || req->rq_disk != next->rq_disk) 762b973cb7eSJens Axboe return NULL; 763d6d48196SJens Axboe 7648fe0d473SMike Christie if (req_op(req) == REQ_OP_WRITE_SAME && 7654363ac7cSMartin K. Petersen !blk_write_same_mergeable(req->bio, next->bio)) 766b973cb7eSJens Axboe return NULL; 7674363ac7cSMartin K. Petersen 768d6d48196SJens Axboe /* 769cb6934f8SJens Axboe * Don't allow merge of different write hints, or for a hint with 770cb6934f8SJens Axboe * non-hint IO. 771cb6934f8SJens Axboe */ 772cb6934f8SJens Axboe if (req->write_hint != next->write_hint) 773cb6934f8SJens Axboe return NULL; 774cb6934f8SJens Axboe 775668ffc03SDamien Le Moal if (req->ioprio != next->ioprio) 776668ffc03SDamien Le Moal return NULL; 777668ffc03SDamien Le Moal 778cb6934f8SJens Axboe /* 779d6d48196SJens Axboe * If we are allowed to merge, then append bio list 780d6d48196SJens Axboe * from next to rq and release next. merge_requests_fn 781d6d48196SJens Axboe * will have updated segment counts, update sector 782445251d0SJens Axboe * counts here. Handle DISCARDs separately, as they 783445251d0SJens Axboe * have separate settings. 784d6d48196SJens Axboe */ 78569840466SJianchao Wang 78669840466SJianchao Wang switch (blk_try_req_merge(req, next)) { 78769840466SJianchao Wang case ELEVATOR_DISCARD_MERGE: 788445251d0SJens Axboe if (!req_attempt_discard_merge(q, req, next)) 789445251d0SJens Axboe return NULL; 79069840466SJianchao Wang break; 79169840466SJianchao Wang case ELEVATOR_BACK_MERGE: 79269840466SJianchao Wang if (!ll_merge_requests_fn(q, req, next)) 793b973cb7eSJens Axboe return NULL; 79469840466SJianchao Wang break; 79569840466SJianchao Wang default: 79669840466SJianchao Wang return NULL; 79769840466SJianchao Wang } 798d6d48196SJens Axboe 799d6d48196SJens Axboe /* 80080a761fdSTejun Heo * If failfast settings disagree or any of the two is already 80180a761fdSTejun Heo * a mixed merge, mark both as mixed before proceeding. This 80280a761fdSTejun Heo * makes sure that all involved bios have mixable attributes 80380a761fdSTejun Heo * set properly. 80480a761fdSTejun Heo */ 805e8064021SChristoph Hellwig if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) || 80680a761fdSTejun Heo (req->cmd_flags & REQ_FAILFAST_MASK) != 80780a761fdSTejun Heo (next->cmd_flags & REQ_FAILFAST_MASK)) { 80880a761fdSTejun Heo blk_rq_set_mixed_merge(req); 80980a761fdSTejun Heo blk_rq_set_mixed_merge(next); 81080a761fdSTejun Heo } 81180a761fdSTejun Heo 81280a761fdSTejun Heo /* 813522a7775SOmar Sandoval * At this point we have either done a back merge or front merge. We 814522a7775SOmar Sandoval * need the smaller start_time_ns of the merged requests to be the 815522a7775SOmar Sandoval * current request for accounting purposes. 816d6d48196SJens Axboe */ 817522a7775SOmar Sandoval if (next->start_time_ns < req->start_time_ns) 818522a7775SOmar Sandoval req->start_time_ns = next->start_time_ns; 819d6d48196SJens Axboe 820d6d48196SJens Axboe req->biotail->bi_next = next->bio; 821d6d48196SJens Axboe req->biotail = next->biotail; 822d6d48196SJens Axboe 823a2dec7b3STejun Heo req->__data_len += blk_rq_bytes(next); 824d6d48196SJens Axboe 8252a5cf35cSMing Lei if (!blk_discard_mergable(req)) 826d6d48196SJens Axboe elv_merge_requests(q, req, next); 827d6d48196SJens Axboe 82842dad764SJerome Marchand /* 82942dad764SJerome Marchand * 'next' is going away, so update stats accordingly 83042dad764SJerome Marchand */ 831b9c54f56SKonstantin Khlebnikov blk_account_io_merge_request(next); 832d6d48196SJens Axboe 833a54895faSChristoph Hellwig trace_block_rq_merge(next); 834f3bdc62fSJan Kara 835e4d750c9SJens Axboe /* 836e4d750c9SJens Axboe * ownership of bio passed from next to req, return 'next' for 837e4d750c9SJens Axboe * the caller to free 838e4d750c9SJens Axboe */ 8391cd96c24SBoaz Harrosh next->bio = NULL; 840b973cb7eSJens Axboe return next; 841d6d48196SJens Axboe } 842d6d48196SJens Axboe 843eda5cc99SChristoph Hellwig static struct request *attempt_back_merge(struct request_queue *q, 844eda5cc99SChristoph Hellwig struct request *rq) 845d6d48196SJens Axboe { 846d6d48196SJens Axboe struct request *next = elv_latter_request(q, rq); 847d6d48196SJens Axboe 848d6d48196SJens Axboe if (next) 849d6d48196SJens Axboe return attempt_merge(q, rq, next); 850d6d48196SJens Axboe 851b973cb7eSJens Axboe return NULL; 852d6d48196SJens Axboe } 853d6d48196SJens Axboe 854eda5cc99SChristoph Hellwig static struct request *attempt_front_merge(struct request_queue *q, 855eda5cc99SChristoph Hellwig struct request *rq) 856d6d48196SJens Axboe { 857d6d48196SJens Axboe struct request *prev = elv_former_request(q, rq); 858d6d48196SJens Axboe 859d6d48196SJens Axboe if (prev) 860d6d48196SJens Axboe return attempt_merge(q, prev, rq); 861d6d48196SJens Axboe 862b973cb7eSJens Axboe return NULL; 863d6d48196SJens Axboe } 8645e84ea3aSJens Axboe 865fd2ef39cSJan Kara /* 866fd2ef39cSJan Kara * Try to merge 'next' into 'rq'. Return true if the merge happened, false 867fd2ef39cSJan Kara * otherwise. The caller is responsible for freeing 'next' if the merge 868fd2ef39cSJan Kara * happened. 869fd2ef39cSJan Kara */ 870fd2ef39cSJan Kara bool blk_attempt_req_merge(struct request_queue *q, struct request *rq, 8715e84ea3aSJens Axboe struct request *next) 8725e84ea3aSJens Axboe { 873fd2ef39cSJan Kara return attempt_merge(q, rq, next); 8745e84ea3aSJens Axboe } 875050c8ea8STejun Heo 876050c8ea8STejun Heo bool blk_rq_merge_ok(struct request *rq, struct bio *bio) 877050c8ea8STejun Heo { 878e2a60da7SMartin K. Petersen if (!rq_mergeable(rq) || !bio_mergeable(bio)) 879050c8ea8STejun Heo return false; 880050c8ea8STejun Heo 881288dab8aSChristoph Hellwig if (req_op(rq) != bio_op(bio)) 882f31dc1cdSMartin K. Petersen return false; 883f31dc1cdSMartin K. Petersen 884050c8ea8STejun Heo /* different data direction or already started, don't merge */ 885050c8ea8STejun Heo if (bio_data_dir(bio) != rq_data_dir(rq)) 886050c8ea8STejun Heo return false; 887050c8ea8STejun Heo 8882081a56bSJens Axboe /* must be same device */ 889309dca30SChristoph Hellwig if (rq->rq_disk != bio->bi_bdev->bd_disk) 890050c8ea8STejun Heo return false; 891050c8ea8STejun Heo 892050c8ea8STejun Heo /* only merge integrity protected bio into ditto rq */ 8934eaf99beSMartin K. Petersen if (blk_integrity_merge_bio(rq->q, rq, bio) == false) 894050c8ea8STejun Heo return false; 895050c8ea8STejun Heo 896a892c8d5SSatya Tangirala /* Only merge if the crypt contexts are compatible */ 897a892c8d5SSatya Tangirala if (!bio_crypt_rq_ctx_compatible(rq, bio)) 898a892c8d5SSatya Tangirala return false; 899a892c8d5SSatya Tangirala 9004363ac7cSMartin K. Petersen /* must be using the same buffer */ 9018fe0d473SMike Christie if (req_op(rq) == REQ_OP_WRITE_SAME && 9024363ac7cSMartin K. Petersen !blk_write_same_mergeable(rq->bio, bio)) 9034363ac7cSMartin K. Petersen return false; 9044363ac7cSMartin K. Petersen 905cb6934f8SJens Axboe /* 906cb6934f8SJens Axboe * Don't allow merge of different write hints, or for a hint with 907cb6934f8SJens Axboe * non-hint IO. 908cb6934f8SJens Axboe */ 909cb6934f8SJens Axboe if (rq->write_hint != bio->bi_write_hint) 910cb6934f8SJens Axboe return false; 911cb6934f8SJens Axboe 912668ffc03SDamien Le Moal if (rq->ioprio != bio_prio(bio)) 913668ffc03SDamien Le Moal return false; 914668ffc03SDamien Le Moal 915050c8ea8STejun Heo return true; 916050c8ea8STejun Heo } 917050c8ea8STejun Heo 91834fe7c05SChristoph Hellwig enum elv_merge blk_try_merge(struct request *rq, struct bio *bio) 919050c8ea8STejun Heo { 92069840466SJianchao Wang if (blk_discard_mergable(rq)) 9211e739730SChristoph Hellwig return ELEVATOR_DISCARD_MERGE; 9221e739730SChristoph Hellwig else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) 923050c8ea8STejun Heo return ELEVATOR_BACK_MERGE; 9244f024f37SKent Overstreet else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) 925050c8ea8STejun Heo return ELEVATOR_FRONT_MERGE; 926050c8ea8STejun Heo return ELEVATOR_NO_MERGE; 927050c8ea8STejun Heo } 9288e756373SBaolin Wang 9298e756373SBaolin Wang static void blk_account_io_merge_bio(struct request *req) 9308e756373SBaolin Wang { 9318e756373SBaolin Wang if (!blk_do_io_stat(req)) 9328e756373SBaolin Wang return; 9338e756373SBaolin Wang 9348e756373SBaolin Wang part_stat_lock(); 9358e756373SBaolin Wang part_stat_inc(req->part, merges[op_stat_group(req_op(req))]); 9368e756373SBaolin Wang part_stat_unlock(); 9378e756373SBaolin Wang } 9388e756373SBaolin Wang 939eda5cc99SChristoph Hellwig enum bio_merge_status { 940eda5cc99SChristoph Hellwig BIO_MERGE_OK, 941eda5cc99SChristoph Hellwig BIO_MERGE_NONE, 942eda5cc99SChristoph Hellwig BIO_MERGE_FAILED, 943eda5cc99SChristoph Hellwig }; 944eda5cc99SChristoph Hellwig 945eda5cc99SChristoph Hellwig static enum bio_merge_status bio_attempt_back_merge(struct request *req, 946eda5cc99SChristoph Hellwig struct bio *bio, unsigned int nr_segs) 9478e756373SBaolin Wang { 9488e756373SBaolin Wang const int ff = bio->bi_opf & REQ_FAILFAST_MASK; 9498e756373SBaolin Wang 9508e756373SBaolin Wang if (!ll_back_merge_fn(req, bio, nr_segs)) 9517d7ca7c5SBaolin Wang return BIO_MERGE_FAILED; 9528e756373SBaolin Wang 953e8a676d6SChristoph Hellwig trace_block_bio_backmerge(bio); 9548e756373SBaolin Wang rq_qos_merge(req->q, req, bio); 9558e756373SBaolin Wang 9568e756373SBaolin Wang if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) 9578e756373SBaolin Wang blk_rq_set_mixed_merge(req); 9588e756373SBaolin Wang 9598e756373SBaolin Wang req->biotail->bi_next = bio; 9608e756373SBaolin Wang req->biotail = bio; 9618e756373SBaolin Wang req->__data_len += bio->bi_iter.bi_size; 9628e756373SBaolin Wang 9638e756373SBaolin Wang bio_crypt_free_ctx(bio); 9648e756373SBaolin Wang 9658e756373SBaolin Wang blk_account_io_merge_bio(req); 9667d7ca7c5SBaolin Wang return BIO_MERGE_OK; 9678e756373SBaolin Wang } 9688e756373SBaolin Wang 969eda5cc99SChristoph Hellwig static enum bio_merge_status bio_attempt_front_merge(struct request *req, 970eda5cc99SChristoph Hellwig struct bio *bio, unsigned int nr_segs) 9718e756373SBaolin Wang { 9728e756373SBaolin Wang const int ff = bio->bi_opf & REQ_FAILFAST_MASK; 9738e756373SBaolin Wang 9748e756373SBaolin Wang if (!ll_front_merge_fn(req, bio, nr_segs)) 9757d7ca7c5SBaolin Wang return BIO_MERGE_FAILED; 9768e756373SBaolin Wang 977e8a676d6SChristoph Hellwig trace_block_bio_frontmerge(bio); 9788e756373SBaolin Wang rq_qos_merge(req->q, req, bio); 9798e756373SBaolin Wang 9808e756373SBaolin Wang if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) 9818e756373SBaolin Wang blk_rq_set_mixed_merge(req); 9828e756373SBaolin Wang 9838e756373SBaolin Wang bio->bi_next = req->bio; 9848e756373SBaolin Wang req->bio = bio; 9858e756373SBaolin Wang 9868e756373SBaolin Wang req->__sector = bio->bi_iter.bi_sector; 9878e756373SBaolin Wang req->__data_len += bio->bi_iter.bi_size; 9888e756373SBaolin Wang 9898e756373SBaolin Wang bio_crypt_do_front_merge(req, bio); 9908e756373SBaolin Wang 9918e756373SBaolin Wang blk_account_io_merge_bio(req); 9927d7ca7c5SBaolin Wang return BIO_MERGE_OK; 9938e756373SBaolin Wang } 9948e756373SBaolin Wang 995eda5cc99SChristoph Hellwig static enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q, 996eda5cc99SChristoph Hellwig struct request *req, struct bio *bio) 9978e756373SBaolin Wang { 9988e756373SBaolin Wang unsigned short segments = blk_rq_nr_discard_segments(req); 9998e756373SBaolin Wang 10008e756373SBaolin Wang if (segments >= queue_max_discard_segments(q)) 10018e756373SBaolin Wang goto no_merge; 10028e756373SBaolin Wang if (blk_rq_sectors(req) + bio_sectors(bio) > 10038e756373SBaolin Wang blk_rq_get_max_sectors(req, blk_rq_pos(req))) 10048e756373SBaolin Wang goto no_merge; 10058e756373SBaolin Wang 10068e756373SBaolin Wang rq_qos_merge(q, req, bio); 10078e756373SBaolin Wang 10088e756373SBaolin Wang req->biotail->bi_next = bio; 10098e756373SBaolin Wang req->biotail = bio; 10108e756373SBaolin Wang req->__data_len += bio->bi_iter.bi_size; 10118e756373SBaolin Wang req->nr_phys_segments = segments + 1; 10128e756373SBaolin Wang 10138e756373SBaolin Wang blk_account_io_merge_bio(req); 10147d7ca7c5SBaolin Wang return BIO_MERGE_OK; 10158e756373SBaolin Wang no_merge: 10168e756373SBaolin Wang req_set_nomerge(q, req); 10177d7ca7c5SBaolin Wang return BIO_MERGE_FAILED; 10187d7ca7c5SBaolin Wang } 10197d7ca7c5SBaolin Wang 10207d7ca7c5SBaolin Wang static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q, 10217d7ca7c5SBaolin Wang struct request *rq, 10227d7ca7c5SBaolin Wang struct bio *bio, 10237d7ca7c5SBaolin Wang unsigned int nr_segs, 10247d7ca7c5SBaolin Wang bool sched_allow_merge) 10257d7ca7c5SBaolin Wang { 10267d7ca7c5SBaolin Wang if (!blk_rq_merge_ok(rq, bio)) 10277d7ca7c5SBaolin Wang return BIO_MERGE_NONE; 10287d7ca7c5SBaolin Wang 10297d7ca7c5SBaolin Wang switch (blk_try_merge(rq, bio)) { 10307d7ca7c5SBaolin Wang case ELEVATOR_BACK_MERGE: 1031265600b7SBaolin Wang if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio)) 10327d7ca7c5SBaolin Wang return bio_attempt_back_merge(rq, bio, nr_segs); 10337d7ca7c5SBaolin Wang break; 10347d7ca7c5SBaolin Wang case ELEVATOR_FRONT_MERGE: 1035265600b7SBaolin Wang if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio)) 10367d7ca7c5SBaolin Wang return bio_attempt_front_merge(rq, bio, nr_segs); 10377d7ca7c5SBaolin Wang break; 10387d7ca7c5SBaolin Wang case ELEVATOR_DISCARD_MERGE: 10397d7ca7c5SBaolin Wang return bio_attempt_discard_merge(q, rq, bio); 10407d7ca7c5SBaolin Wang default: 10417d7ca7c5SBaolin Wang return BIO_MERGE_NONE; 10427d7ca7c5SBaolin Wang } 10437d7ca7c5SBaolin Wang 10447d7ca7c5SBaolin Wang return BIO_MERGE_FAILED; 10458e756373SBaolin Wang } 10468e756373SBaolin Wang 10478e756373SBaolin Wang /** 10488e756373SBaolin Wang * blk_attempt_plug_merge - try to merge with %current's plugged list 10498e756373SBaolin Wang * @q: request_queue new bio is being queued at 10508e756373SBaolin Wang * @bio: new bio being queued 10518e756373SBaolin Wang * @nr_segs: number of segments in @bio 10528e756373SBaolin Wang * @same_queue_rq: pointer to &struct request that gets filled in when 10538e756373SBaolin Wang * another request associated with @q is found on the plug list 10548e756373SBaolin Wang * (optional, may be %NULL) 10558e756373SBaolin Wang * 10568e756373SBaolin Wang * Determine whether @bio being queued on @q can be merged with a request 10578e756373SBaolin Wang * on %current's plugged list. Returns %true if merge was successful, 10588e756373SBaolin Wang * otherwise %false. 10598e756373SBaolin Wang * 10608e756373SBaolin Wang * Plugging coalesces IOs from the same issuer for the same purpose without 10618e756373SBaolin Wang * going through @q->queue_lock. As such it's more of an issuing mechanism 10628e756373SBaolin Wang * than scheduling, and the request, while may have elvpriv data, is not 10638e756373SBaolin Wang * added on the elevator at this point. In addition, we don't have 10648e756373SBaolin Wang * reliable access to the elevator outside queue lock. Only check basic 10658e756373SBaolin Wang * merging parameters without querying the elevator. 10668e756373SBaolin Wang * 10678e756373SBaolin Wang * Caller must ensure !blk_queue_nomerges(q) beforehand. 10688e756373SBaolin Wang */ 10698e756373SBaolin Wang bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio, 10708e756373SBaolin Wang unsigned int nr_segs, struct request **same_queue_rq) 10718e756373SBaolin Wang { 10728e756373SBaolin Wang struct blk_plug *plug; 10738e756373SBaolin Wang struct request *rq; 10748e756373SBaolin Wang struct list_head *plug_list; 10758e756373SBaolin Wang 10768e756373SBaolin Wang plug = blk_mq_plug(q, bio); 10778e756373SBaolin Wang if (!plug) 10788e756373SBaolin Wang return false; 10798e756373SBaolin Wang 10808e756373SBaolin Wang plug_list = &plug->mq_list; 10818e756373SBaolin Wang 10828e756373SBaolin Wang list_for_each_entry_reverse(rq, plug_list, queuelist) { 10838e756373SBaolin Wang if (rq->q == q && same_queue_rq) { 10848e756373SBaolin Wang /* 10858e756373SBaolin Wang * Only blk-mq multiple hardware queues case checks the 10868e756373SBaolin Wang * rq in the same queue, there should be only one such 10878e756373SBaolin Wang * rq in a queue 10888e756373SBaolin Wang **/ 10898e756373SBaolin Wang *same_queue_rq = rq; 10908e756373SBaolin Wang } 10918e756373SBaolin Wang 10927d7ca7c5SBaolin Wang if (rq->q != q) 10938e756373SBaolin Wang continue; 10948e756373SBaolin Wang 10957d7ca7c5SBaolin Wang if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) == 10967d7ca7c5SBaolin Wang BIO_MERGE_OK) 10978e756373SBaolin Wang return true; 10988e756373SBaolin Wang } 10998e756373SBaolin Wang 11008e756373SBaolin Wang return false; 11018e756373SBaolin Wang } 1102bdc6a287SBaolin Wang 1103bdc6a287SBaolin Wang /* 1104bdc6a287SBaolin Wang * Iterate list of requests and see if we can merge this bio with any 1105bdc6a287SBaolin Wang * of them. 1106bdc6a287SBaolin Wang */ 1107bdc6a287SBaolin Wang bool blk_bio_list_merge(struct request_queue *q, struct list_head *list, 1108bdc6a287SBaolin Wang struct bio *bio, unsigned int nr_segs) 1109bdc6a287SBaolin Wang { 1110bdc6a287SBaolin Wang struct request *rq; 1111bdc6a287SBaolin Wang int checked = 8; 1112bdc6a287SBaolin Wang 1113bdc6a287SBaolin Wang list_for_each_entry_reverse(rq, list, queuelist) { 1114bdc6a287SBaolin Wang if (!checked--) 1115bdc6a287SBaolin Wang break; 1116bdc6a287SBaolin Wang 11177d7ca7c5SBaolin Wang switch (blk_attempt_bio_merge(q, rq, bio, nr_segs, true)) { 11187d7ca7c5SBaolin Wang case BIO_MERGE_NONE: 1119bdc6a287SBaolin Wang continue; 11207d7ca7c5SBaolin Wang case BIO_MERGE_OK: 11217d7ca7c5SBaolin Wang return true; 11227d7ca7c5SBaolin Wang case BIO_MERGE_FAILED: 11237d7ca7c5SBaolin Wang return false; 1124bdc6a287SBaolin Wang } 1125bdc6a287SBaolin Wang 1126bdc6a287SBaolin Wang } 1127bdc6a287SBaolin Wang 1128bdc6a287SBaolin Wang return false; 1129bdc6a287SBaolin Wang } 1130bdc6a287SBaolin Wang EXPORT_SYMBOL_GPL(blk_bio_list_merge); 1131eda5cc99SChristoph Hellwig 1132eda5cc99SChristoph Hellwig bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio, 1133eda5cc99SChristoph Hellwig unsigned int nr_segs, struct request **merged_request) 1134eda5cc99SChristoph Hellwig { 1135eda5cc99SChristoph Hellwig struct request *rq; 1136eda5cc99SChristoph Hellwig 1137eda5cc99SChristoph Hellwig switch (elv_merge(q, &rq, bio)) { 1138eda5cc99SChristoph Hellwig case ELEVATOR_BACK_MERGE: 1139eda5cc99SChristoph Hellwig if (!blk_mq_sched_allow_merge(q, rq, bio)) 1140eda5cc99SChristoph Hellwig return false; 1141eda5cc99SChristoph Hellwig if (bio_attempt_back_merge(rq, bio, nr_segs) != BIO_MERGE_OK) 1142eda5cc99SChristoph Hellwig return false; 1143eda5cc99SChristoph Hellwig *merged_request = attempt_back_merge(q, rq); 1144eda5cc99SChristoph Hellwig if (!*merged_request) 1145eda5cc99SChristoph Hellwig elv_merged_request(q, rq, ELEVATOR_BACK_MERGE); 1146eda5cc99SChristoph Hellwig return true; 1147eda5cc99SChristoph Hellwig case ELEVATOR_FRONT_MERGE: 1148eda5cc99SChristoph Hellwig if (!blk_mq_sched_allow_merge(q, rq, bio)) 1149eda5cc99SChristoph Hellwig return false; 1150eda5cc99SChristoph Hellwig if (bio_attempt_front_merge(rq, bio, nr_segs) != BIO_MERGE_OK) 1151eda5cc99SChristoph Hellwig return false; 1152eda5cc99SChristoph Hellwig *merged_request = attempt_front_merge(q, rq); 1153eda5cc99SChristoph Hellwig if (!*merged_request) 1154eda5cc99SChristoph Hellwig elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE); 1155eda5cc99SChristoph Hellwig return true; 1156eda5cc99SChristoph Hellwig case ELEVATOR_DISCARD_MERGE: 1157eda5cc99SChristoph Hellwig return bio_attempt_discard_merge(q, rq, bio) == BIO_MERGE_OK; 1158eda5cc99SChristoph Hellwig default: 1159eda5cc99SChristoph Hellwig return false; 1160eda5cc99SChristoph Hellwig } 1161eda5cc99SChristoph Hellwig } 1162eda5cc99SChristoph Hellwig EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge); 1163