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> 1182d981d4SChristoph Hellwig #include <linux/part_stat.h> 126b2b0459STejun Heo #include <linux/blk-cgroup.h> 13d6d48196SJens Axboe 14cda22646SMike Krinkin #include <trace/events/block.h> 15cda22646SMike Krinkin 16d6d48196SJens Axboe #include "blk.h" 172aa7745bSChristoph Hellwig #include "blk-mq-sched.h" 188e756373SBaolin Wang #include "blk-rq-qos.h" 19a7b36ee6SJens Axboe #include "blk-throttle.h" 20d6d48196SJens Axboe 21ff18d77bSChristoph Hellwig static inline void bio_get_first_bvec(struct bio *bio, struct bio_vec *bv) 22ff18d77bSChristoph Hellwig { 23ff18d77bSChristoph Hellwig *bv = mp_bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter); 24ff18d77bSChristoph Hellwig } 25ff18d77bSChristoph Hellwig 26ff18d77bSChristoph Hellwig static inline void bio_get_last_bvec(struct bio *bio, struct bio_vec *bv) 27ff18d77bSChristoph Hellwig { 28ff18d77bSChristoph Hellwig struct bvec_iter iter = bio->bi_iter; 29ff18d77bSChristoph Hellwig int idx; 30ff18d77bSChristoph Hellwig 31ff18d77bSChristoph Hellwig bio_get_first_bvec(bio, bv); 32ff18d77bSChristoph Hellwig if (bv->bv_len == bio->bi_iter.bi_size) 33ff18d77bSChristoph Hellwig return; /* this bio only has a single bvec */ 34ff18d77bSChristoph Hellwig 35ff18d77bSChristoph Hellwig bio_advance_iter(bio, &iter, iter.bi_size); 36ff18d77bSChristoph Hellwig 37ff18d77bSChristoph Hellwig if (!iter.bi_bvec_done) 38ff18d77bSChristoph Hellwig idx = iter.bi_idx - 1; 39ff18d77bSChristoph Hellwig else /* in the middle of bvec */ 40ff18d77bSChristoph Hellwig idx = iter.bi_idx; 41ff18d77bSChristoph Hellwig 42ff18d77bSChristoph Hellwig *bv = bio->bi_io_vec[idx]; 43ff18d77bSChristoph Hellwig 44ff18d77bSChristoph Hellwig /* 45ff18d77bSChristoph Hellwig * iter.bi_bvec_done records actual length of the last bvec 46ff18d77bSChristoph Hellwig * if this bio ends in the middle of one io vector 47ff18d77bSChristoph Hellwig */ 48ff18d77bSChristoph Hellwig if (iter.bi_bvec_done) 49ff18d77bSChristoph Hellwig bv->bv_len = iter.bi_bvec_done; 50ff18d77bSChristoph Hellwig } 51ff18d77bSChristoph Hellwig 52e9907009SChristoph Hellwig static inline bool bio_will_gap(struct request_queue *q, 53e9907009SChristoph Hellwig struct request *prev_rq, struct bio *prev, struct bio *next) 54e9907009SChristoph Hellwig { 55e9907009SChristoph Hellwig struct bio_vec pb, nb; 56e9907009SChristoph Hellwig 57e9907009SChristoph Hellwig if (!bio_has_data(prev) || !queue_virt_boundary(q)) 58e9907009SChristoph Hellwig return false; 59e9907009SChristoph Hellwig 60e9907009SChristoph Hellwig /* 61e9907009SChristoph Hellwig * Don't merge if the 1st bio starts with non-zero offset, otherwise it 62e9907009SChristoph Hellwig * is quite difficult to respect the sg gap limit. We work hard to 63e9907009SChristoph Hellwig * merge a huge number of small single bios in case of mkfs. 64e9907009SChristoph Hellwig */ 65e9907009SChristoph Hellwig if (prev_rq) 66e9907009SChristoph Hellwig bio_get_first_bvec(prev_rq->bio, &pb); 67e9907009SChristoph Hellwig else 68e9907009SChristoph Hellwig bio_get_first_bvec(prev, &pb); 69df376b2eSJohannes Thumshirn if (pb.bv_offset & queue_virt_boundary(q)) 70e9907009SChristoph Hellwig return true; 71e9907009SChristoph Hellwig 72e9907009SChristoph Hellwig /* 73e9907009SChristoph Hellwig * We don't need to worry about the situation that the merged segment 74e9907009SChristoph Hellwig * ends in unaligned virt boundary: 75e9907009SChristoph Hellwig * 76e9907009SChristoph Hellwig * - if 'pb' ends aligned, the merged segment ends aligned 77e9907009SChristoph Hellwig * - if 'pb' ends unaligned, the next bio must include 78e9907009SChristoph Hellwig * one single bvec of 'nb', otherwise the 'nb' can't 79e9907009SChristoph Hellwig * merge with 'pb' 80e9907009SChristoph Hellwig */ 81e9907009SChristoph Hellwig bio_get_last_bvec(prev, &pb); 82e9907009SChristoph Hellwig bio_get_first_bvec(next, &nb); 83200a9affSChristoph Hellwig if (biovec_phys_mergeable(q, &pb, &nb)) 84e9907009SChristoph Hellwig return false; 85c55ddd90SChristoph Hellwig return __bvec_gap_to_prev(&q->limits, &pb, nb.bv_offset); 86e9907009SChristoph Hellwig } 87e9907009SChristoph Hellwig 88e9907009SChristoph Hellwig static inline bool req_gap_back_merge(struct request *req, struct bio *bio) 89e9907009SChristoph Hellwig { 90e9907009SChristoph Hellwig return bio_will_gap(req->q, req, req->biotail, bio); 91e9907009SChristoph Hellwig } 92e9907009SChristoph Hellwig 93e9907009SChristoph Hellwig static inline bool req_gap_front_merge(struct request *req, struct bio *bio) 94e9907009SChristoph Hellwig { 95e9907009SChristoph Hellwig return bio_will_gap(req->q, NULL, bio, req->bio); 96e9907009SChristoph Hellwig } 97e9907009SChristoph Hellwig 98b6dc6198SChristoph Hellwig /* 99b6dc6198SChristoph Hellwig * The max size one bio can handle is UINT_MAX becasue bvec_iter.bi_size 100b6dc6198SChristoph Hellwig * is defined as 'unsigned int', meantime it has to be aligned to with the 101b6dc6198SChristoph Hellwig * logical block size, which is the minimum accepted unit by hardware. 102b6dc6198SChristoph Hellwig */ 103*aa261f20SBart Van Assche static unsigned int bio_allowed_max_sectors(const struct queue_limits *lim) 104b6dc6198SChristoph Hellwig { 105c55ddd90SChristoph Hellwig return round_down(UINT_MAX, lim->logical_block_size) >> SECTOR_SHIFT; 106b6dc6198SChristoph Hellwig } 107b6dc6198SChristoph Hellwig 108*aa261f20SBart Van Assche static struct bio *bio_split_discard(struct bio *bio, 109*aa261f20SBart Van Assche const struct queue_limits *lim, 1105a97806fSChristoph Hellwig unsigned *nsegs, struct bio_set *bs) 11154efd50bSKent Overstreet { 11254efd50bSKent Overstreet unsigned int max_discard_sectors, granularity; 11354efd50bSKent Overstreet sector_t tmp; 11454efd50bSKent Overstreet unsigned split_sectors; 11554efd50bSKent Overstreet 116bdced438SMing Lei *nsegs = 1; 117bdced438SMing Lei 11854efd50bSKent Overstreet /* Zero-sector (unknown) and one-sector granularities are the same. */ 119c55ddd90SChristoph Hellwig granularity = max(lim->discard_granularity >> 9, 1U); 12054efd50bSKent Overstreet 121c55ddd90SChristoph Hellwig max_discard_sectors = 122c55ddd90SChristoph Hellwig min(lim->max_discard_sectors, bio_allowed_max_sectors(lim)); 12354efd50bSKent Overstreet max_discard_sectors -= max_discard_sectors % granularity; 12454efd50bSKent Overstreet 12554efd50bSKent Overstreet if (unlikely(!max_discard_sectors)) { 12654efd50bSKent Overstreet /* XXX: warn */ 12754efd50bSKent Overstreet return NULL; 12854efd50bSKent Overstreet } 12954efd50bSKent Overstreet 13054efd50bSKent Overstreet if (bio_sectors(bio) <= max_discard_sectors) 13154efd50bSKent Overstreet return NULL; 13254efd50bSKent Overstreet 13354efd50bSKent Overstreet split_sectors = max_discard_sectors; 13454efd50bSKent Overstreet 13554efd50bSKent Overstreet /* 13654efd50bSKent Overstreet * If the next starting sector would be misaligned, stop the discard at 13754efd50bSKent Overstreet * the previous aligned sector. 13854efd50bSKent Overstreet */ 139c55ddd90SChristoph Hellwig tmp = bio->bi_iter.bi_sector + split_sectors - 140c55ddd90SChristoph Hellwig ((lim->discard_alignment >> 9) % granularity); 14154efd50bSKent Overstreet tmp = sector_div(tmp, granularity); 14254efd50bSKent Overstreet 14354efd50bSKent Overstreet if (split_sectors > tmp) 14454efd50bSKent Overstreet split_sectors -= tmp; 14554efd50bSKent Overstreet 14654efd50bSKent Overstreet return bio_split(bio, split_sectors, GFP_NOIO, bs); 14754efd50bSKent Overstreet } 14854efd50bSKent Overstreet 1495a97806fSChristoph Hellwig static struct bio *bio_split_write_zeroes(struct bio *bio, 150*aa261f20SBart Van Assche const struct queue_limits *lim, 151*aa261f20SBart Van Assche unsigned *nsegs, struct bio_set *bs) 152885fa13fSChristoph Hellwig { 153d665e12aSChristoph Hellwig *nsegs = 0; 154c55ddd90SChristoph Hellwig if (!lim->max_write_zeroes_sectors) 155885fa13fSChristoph Hellwig return NULL; 156c55ddd90SChristoph Hellwig if (bio_sectors(bio) <= lim->max_write_zeroes_sectors) 157885fa13fSChristoph Hellwig return NULL; 158c55ddd90SChristoph Hellwig return bio_split(bio, lim->max_write_zeroes_sectors, GFP_NOIO, bs); 159885fa13fSChristoph Hellwig } 160885fa13fSChristoph Hellwig 1619cc5169cSBart Van Assche /* 1629cc5169cSBart Van Assche * Return the maximum number of sectors from the start of a bio that may be 1639cc5169cSBart Van Assche * submitted as a single request to a block device. If enough sectors remain, 1649cc5169cSBart Van Assche * align the end to the physical block size. Otherwise align the end to the 1659cc5169cSBart Van Assche * logical block size. This approach minimizes the number of non-aligned 1669cc5169cSBart Van Assche * requests that are submitted to a block device if the start of a bio is not 1679cc5169cSBart Van Assche * aligned to a physical block boundary. 1689cc5169cSBart Van Assche */ 1695a97806fSChristoph Hellwig static inline unsigned get_max_io_size(struct bio *bio, 170*aa261f20SBart Van Assche const struct queue_limits *lim) 171d0e5fbb0SMing Lei { 172c55ddd90SChristoph Hellwig unsigned pbs = lim->physical_block_size >> SECTOR_SHIFT; 173c55ddd90SChristoph Hellwig unsigned lbs = lim->logical_block_size >> SECTOR_SHIFT; 174c55ddd90SChristoph Hellwig unsigned max_sectors = lim->max_sectors, start, end; 175d0e5fbb0SMing Lei 176c55ddd90SChristoph Hellwig if (lim->chunk_sectors) { 177efef739dSChristoph Hellwig max_sectors = min(max_sectors, 178efef739dSChristoph Hellwig blk_chunk_sectors_left(bio->bi_iter.bi_sector, 179c55ddd90SChristoph Hellwig lim->chunk_sectors)); 180efef739dSChristoph Hellwig } 181d0e5fbb0SMing Lei 18284613bedSChristoph Hellwig start = bio->bi_iter.bi_sector & (pbs - 1); 18384613bedSChristoph Hellwig end = (start + max_sectors) & ~(pbs - 1); 18484613bedSChristoph Hellwig if (end > start) 18584613bedSChristoph Hellwig return end - start; 18684613bedSChristoph Hellwig return max_sectors & ~(lbs - 1); 187d0e5fbb0SMing Lei } 188d0e5fbb0SMing Lei 189*aa261f20SBart Van Assche static inline unsigned get_max_segment_size(const struct queue_limits *lim, 190c55ddd90SChristoph Hellwig struct page *start_page, unsigned long offset) 191dcebd755SMing Lei { 192c55ddd90SChristoph Hellwig unsigned long mask = lim->seg_boundary_mask; 193dcebd755SMing Lei 194429120f3SMing Lei offset = mask & (page_to_phys(start_page) + offset); 1954a2f704eSMing Lei 1964a2f704eSMing Lei /* 1974a2f704eSMing Lei * overflow may be triggered in case of zero page physical address 1984a2f704eSMing Lei * on 32bit arch, use queue's max segment size when that happens. 1994a2f704eSMing Lei */ 2004a2f704eSMing Lei return min_not_zero(mask - offset + 1, 201c55ddd90SChristoph Hellwig (unsigned long)lim->max_segment_size); 202dcebd755SMing Lei } 203dcebd755SMing Lei 204708b25b3SBart Van Assche /** 205708b25b3SBart Van Assche * bvec_split_segs - verify whether or not a bvec should be split in the middle 206c55ddd90SChristoph Hellwig * @lim: [in] queue limits to split based on 207708b25b3SBart Van Assche * @bv: [in] bvec to examine 208708b25b3SBart Van Assche * @nsegs: [in,out] Number of segments in the bio being built. Incremented 209708b25b3SBart Van Assche * by the number of segments from @bv that may be appended to that 210708b25b3SBart Van Assche * bio without exceeding @max_segs 21167927d22SKeith Busch * @bytes: [in,out] Number of bytes in the bio being built. Incremented 21267927d22SKeith Busch * by the number of bytes from @bv that may be appended to that 21367927d22SKeith Busch * bio without exceeding @max_bytes 214708b25b3SBart Van Assche * @max_segs: [in] upper bound for *@nsegs 21567927d22SKeith Busch * @max_bytes: [in] upper bound for *@bytes 216708b25b3SBart Van Assche * 217708b25b3SBart Van Assche * When splitting a bio, it can happen that a bvec is encountered that is too 218708b25b3SBart Van Assche * big to fit in a single segment and hence that it has to be split in the 219708b25b3SBart Van Assche * middle. This function verifies whether or not that should happen. The value 220708b25b3SBart Van Assche * %true is returned if and only if appending the entire @bv to a bio with 221708b25b3SBart Van Assche * *@nsegs segments and *@sectors sectors would make that bio unacceptable for 222708b25b3SBart Van Assche * the block driver. 223dcebd755SMing Lei */ 224*aa261f20SBart Van Assche static bool bvec_split_segs(const struct queue_limits *lim, 225*aa261f20SBart Van Assche const struct bio_vec *bv, unsigned *nsegs, unsigned *bytes, 226*aa261f20SBart Van Assche unsigned max_segs, unsigned max_bytes) 227dcebd755SMing Lei { 22867927d22SKeith Busch unsigned max_len = min(max_bytes, UINT_MAX) - *bytes; 229708b25b3SBart Van Assche unsigned len = min(bv->bv_len, max_len); 230dcebd755SMing Lei unsigned total_len = 0; 231ff9811b3SBart Van Assche unsigned seg_size = 0; 232dcebd755SMing Lei 233ff9811b3SBart Van Assche while (len && *nsegs < max_segs) { 234c55ddd90SChristoph Hellwig seg_size = get_max_segment_size(lim, bv->bv_page, 235429120f3SMing Lei bv->bv_offset + total_len); 236dcebd755SMing Lei seg_size = min(seg_size, len); 237dcebd755SMing Lei 238ff9811b3SBart Van Assche (*nsegs)++; 239dcebd755SMing Lei total_len += seg_size; 240dcebd755SMing Lei len -= seg_size; 241dcebd755SMing Lei 242c55ddd90SChristoph Hellwig if ((bv->bv_offset + total_len) & lim->virt_boundary_mask) 243dcebd755SMing Lei break; 244dcebd755SMing Lei } 245dcebd755SMing Lei 24667927d22SKeith Busch *bytes += total_len; 247dcebd755SMing Lei 248708b25b3SBart Van Assche /* tell the caller to split the bvec if it is too big to fit */ 249708b25b3SBart Van Assche return len > 0 || bv->bv_len > max_len; 250dcebd755SMing Lei } 251dcebd755SMing Lei 252dad77584SBart Van Assche /** 2535a97806fSChristoph Hellwig * bio_split_rw - split a bio in two bios 254dad77584SBart Van Assche * @bio: [in] bio to be split 255c55ddd90SChristoph Hellwig * @lim: [in] queue limits to split based on 256dad77584SBart Van Assche * @segs: [out] number of segments in the bio with the first half of the sectors 2575a97806fSChristoph Hellwig * @bs: [in] bio set to allocate the clone from 258a85b3637SChristoph Hellwig * @max_bytes: [in] maximum number of bytes per bio 259dad77584SBart Van Assche * 260dad77584SBart Van Assche * Clone @bio, update the bi_iter of the clone to represent the first sectors 261dad77584SBart Van Assche * of @bio and update @bio->bi_iter to represent the remaining sectors. The 262dad77584SBart Van Assche * following is guaranteed for the cloned bio: 263a85b3637SChristoph Hellwig * - That it has at most @max_bytes worth of data 264dad77584SBart Van Assche * - That it has at most queue_max_segments(@q) segments. 265dad77584SBart Van Assche * 266dad77584SBart Van Assche * Except for discard requests the cloned bio will point at the bi_io_vec of 267dad77584SBart Van Assche * the original bio. It is the responsibility of the caller to ensure that the 268dad77584SBart Van Assche * original bio is not freed before the cloned bio. The caller is also 269dad77584SBart Van Assche * responsible for ensuring that @bs is only destroyed after processing of the 270dad77584SBart Van Assche * split bio has finished. 271dad77584SBart Van Assche */ 272*aa261f20SBart Van Assche static struct bio *bio_split_rw(struct bio *bio, const struct queue_limits *lim, 273a85b3637SChristoph Hellwig unsigned *segs, struct bio_set *bs, unsigned max_bytes) 27454efd50bSKent Overstreet { 2755014c311SJens Axboe struct bio_vec bv, bvprv, *bvprvp = NULL; 27654efd50bSKent Overstreet struct bvec_iter iter; 27767927d22SKeith Busch unsigned nsegs = 0, bytes = 0; 27854efd50bSKent Overstreet 279dcebd755SMing Lei bio_for_each_bvec(bv, bio, iter) { 28054efd50bSKent Overstreet /* 28154efd50bSKent Overstreet * If the queue doesn't support SG gaps and adding this 28254efd50bSKent Overstreet * offset would create a gap, disallow it. 28354efd50bSKent Overstreet */ 284c55ddd90SChristoph Hellwig if (bvprvp && bvec_gap_to_prev(lim, bvprvp, bv.bv_offset)) 28554efd50bSKent Overstreet goto split; 28654efd50bSKent Overstreet 287c55ddd90SChristoph Hellwig if (nsegs < lim->max_segments && 28867927d22SKeith Busch bytes + bv.bv_len <= max_bytes && 289708b25b3SBart Van Assche bv.bv_offset + bv.bv_len <= PAGE_SIZE) { 290708b25b3SBart Van Assche nsegs++; 29167927d22SKeith Busch bytes += bv.bv_len; 292c55ddd90SChristoph Hellwig } else { 293c55ddd90SChristoph Hellwig if (bvec_split_segs(lim, &bv, &nsegs, &bytes, 294c55ddd90SChristoph Hellwig lim->max_segments, max_bytes)) 295e36f6204SKeith Busch goto split; 296e36f6204SKeith Busch } 297e36f6204SKeith Busch 29854efd50bSKent Overstreet bvprv = bv; 299578270bfSMing Lei bvprvp = &bvprv; 30054efd50bSKent Overstreet } 30154efd50bSKent Overstreet 302d627065dSChristoph Hellwig *segs = nsegs; 303d627065dSChristoph Hellwig return NULL; 30454efd50bSKent Overstreet split: 305bdced438SMing Lei *segs = nsegs; 306cc29e1bfSJeffle Xu 307cc29e1bfSJeffle Xu /* 30867927d22SKeith Busch * Individual bvecs might not be logical block aligned. Round down the 30967927d22SKeith Busch * split size so that each bio is properly block size aligned, even if 31067927d22SKeith Busch * we do not use the full hardware limits. 31167927d22SKeith Busch */ 312c55ddd90SChristoph Hellwig bytes = ALIGN_DOWN(bytes, lim->logical_block_size); 31367927d22SKeith Busch 31467927d22SKeith Busch /* 315cc29e1bfSJeffle Xu * Bio splitting may cause subtle trouble such as hang when doing sync 316cc29e1bfSJeffle Xu * iopoll in direct IO routine. Given performance gain of iopoll for 317cc29e1bfSJeffle Xu * big IO can be trival, disable iopoll when split needed. 318cc29e1bfSJeffle Xu */ 3196ce913feSChristoph Hellwig bio_clear_polled(bio); 32067927d22SKeith Busch return bio_split(bio, bytes >> SECTOR_SHIFT, GFP_NOIO, bs); 32154efd50bSKent Overstreet } 32254efd50bSKent Overstreet 323dad77584SBart Van Assche /** 3245a97806fSChristoph Hellwig * __bio_split_to_limits - split a bio to fit the queue limits 3255a97806fSChristoph Hellwig * @bio: bio to be split 326c55ddd90SChristoph Hellwig * @lim: queue limits to split based on 3275a97806fSChristoph Hellwig * @nr_segs: returns the number of segments in the returned bio 328dad77584SBart Van Assche * 3295a97806fSChristoph Hellwig * Check if @bio needs splitting based on the queue limits, and if so split off 3305a97806fSChristoph Hellwig * a bio fitting the limits from the beginning of @bio and return it. @bio is 3315a97806fSChristoph Hellwig * shortened to the remainder and re-submitted. 3325a97806fSChristoph Hellwig * 3335a97806fSChristoph Hellwig * The split bio is allocated from @q->bio_split, which is provided by the 3345a97806fSChristoph Hellwig * block layer. 335dad77584SBart Van Assche */ 336*aa261f20SBart Van Assche struct bio *__bio_split_to_limits(struct bio *bio, 337*aa261f20SBart Van Assche const struct queue_limits *lim, 338abd45c15SJens Axboe unsigned int *nr_segs) 33954efd50bSKent Overstreet { 34046754bd0SChristoph Hellwig struct bio_set *bs = &bio->bi_bdev->bd_disk->bio_split; 3415a97806fSChristoph Hellwig struct bio *split; 34254efd50bSKent Overstreet 3435a97806fSChristoph Hellwig switch (bio_op(bio)) { 3447afafc8aSAdrian Hunter case REQ_OP_DISCARD: 3457afafc8aSAdrian Hunter case REQ_OP_SECURE_ERASE: 346c55ddd90SChristoph Hellwig split = bio_split_discard(bio, lim, nr_segs, bs); 3477afafc8aSAdrian Hunter break; 348a6f0788eSChaitanya Kulkarni case REQ_OP_WRITE_ZEROES: 349c55ddd90SChristoph Hellwig split = bio_split_write_zeroes(bio, lim, nr_segs, bs); 350a6f0788eSChaitanya Kulkarni break; 3517afafc8aSAdrian Hunter default: 352c55ddd90SChristoph Hellwig split = bio_split_rw(bio, lim, nr_segs, bs, 353c55ddd90SChristoph Hellwig get_max_io_size(bio, lim) << SECTOR_SHIFT); 3547afafc8aSAdrian Hunter break; 3557afafc8aSAdrian Hunter } 356bdced438SMing Lei 35754efd50bSKent Overstreet if (split) { 3586ac45aebSMing Lei /* there isn't chance to merge the splitted bio */ 3591eff9d32SJens Axboe split->bi_opf |= REQ_NOMERGE; 3606ac45aebSMing Lei 361957a2b34SMuchun Song blkcg_bio_issue_init(split); 3625a97806fSChristoph Hellwig bio_chain(split, bio); 3635a97806fSChristoph Hellwig trace_block_split(split, bio->bi_iter.bi_sector); 3645a97806fSChristoph Hellwig submit_bio_noacct(bio); 3655a97806fSChristoph Hellwig return split; 36654efd50bSKent Overstreet } 3675a97806fSChristoph Hellwig return bio; 36854efd50bSKent Overstreet } 36914ccb66bSChristoph Hellwig 370dad77584SBart Van Assche /** 3715a97806fSChristoph Hellwig * bio_split_to_limits - split a bio to fit the queue limits 3725a97806fSChristoph Hellwig * @bio: bio to be split 373dad77584SBart Van Assche * 3745a97806fSChristoph Hellwig * Check if @bio needs splitting based on the queue limits of @bio->bi_bdev, and 3755a97806fSChristoph Hellwig * if so split off a bio fitting the limits from the beginning of @bio and 3765a97806fSChristoph Hellwig * return it. @bio is shortened to the remainder and re-submitted. 3775a97806fSChristoph Hellwig * 3785a97806fSChristoph Hellwig * The split bio is allocated from @q->bio_split, which is provided by the 3795a97806fSChristoph Hellwig * block layer. 380dad77584SBart Van Assche */ 3815a97806fSChristoph Hellwig struct bio *bio_split_to_limits(struct bio *bio) 38214ccb66bSChristoph Hellwig { 383*aa261f20SBart Van Assche const struct queue_limits *lim = &bdev_get_queue(bio->bi_bdev)->limits; 38414ccb66bSChristoph Hellwig unsigned int nr_segs; 38514ccb66bSChristoph Hellwig 386c55ddd90SChristoph Hellwig if (bio_may_exceed_limits(bio, lim)) 387c55ddd90SChristoph Hellwig return __bio_split_to_limits(bio, lim, &nr_segs); 3885a97806fSChristoph Hellwig return bio; 38914ccb66bSChristoph Hellwig } 3905a97806fSChristoph Hellwig EXPORT_SYMBOL(bio_split_to_limits); 39154efd50bSKent Overstreet 392e9cd19c0SChristoph Hellwig unsigned int blk_recalc_rq_segments(struct request *rq) 393d6d48196SJens Axboe { 3946869875fSChristoph Hellwig unsigned int nr_phys_segs = 0; 39567927d22SKeith Busch unsigned int bytes = 0; 396e9cd19c0SChristoph Hellwig struct req_iterator iter; 3976869875fSChristoph Hellwig struct bio_vec bv; 398d6d48196SJens Axboe 399e9cd19c0SChristoph Hellwig if (!rq->bio) 4001e428079SJens Axboe return 0; 401d6d48196SJens Axboe 402e9cd19c0SChristoph Hellwig switch (bio_op(rq->bio)) { 403a6f0788eSChaitanya Kulkarni case REQ_OP_DISCARD: 404a6f0788eSChaitanya Kulkarni case REQ_OP_SECURE_ERASE: 405a958937fSDavid Jeffery if (queue_max_discard_segments(rq->q) > 1) { 406a958937fSDavid Jeffery struct bio *bio = rq->bio; 407a958937fSDavid Jeffery 408a958937fSDavid Jeffery for_each_bio(bio) 409a958937fSDavid Jeffery nr_phys_segs++; 410a958937fSDavid Jeffery return nr_phys_segs; 411a958937fSDavid Jeffery } 412a958937fSDavid Jeffery return 1; 413a6f0788eSChaitanya Kulkarni case REQ_OP_WRITE_ZEROES: 414f9d03f96SChristoph Hellwig return 0; 4152d9b02beSBart Van Assche default: 4162d9b02beSBart Van Assche break; 417a6f0788eSChaitanya Kulkarni } 4185cb8850cSKent Overstreet 419e9cd19c0SChristoph Hellwig rq_for_each_bvec(bv, rq, iter) 420c55ddd90SChristoph Hellwig bvec_split_segs(&rq->q->limits, &bv, &nr_phys_segs, &bytes, 421708b25b3SBart Van Assche UINT_MAX, UINT_MAX); 4221e428079SJens Axboe return nr_phys_segs; 4231e428079SJens Axboe } 4241e428079SJens Axboe 42548d7727cSMing Lei static inline struct scatterlist *blk_next_sg(struct scatterlist **sg, 426862e5a5eSMing Lei struct scatterlist *sglist) 427862e5a5eSMing Lei { 428862e5a5eSMing Lei if (!*sg) 429862e5a5eSMing Lei return sglist; 430862e5a5eSMing Lei 431862e5a5eSMing Lei /* 432862e5a5eSMing Lei * If the driver previously mapped a shorter list, we could see a 433862e5a5eSMing Lei * termination bit prematurely unless it fully inits the sg table 434862e5a5eSMing Lei * on each mapping. We KNOW that there must be more entries here 435862e5a5eSMing Lei * or the driver would be buggy, so force clear the termination bit 436862e5a5eSMing Lei * to avoid doing a full sg_init_table() in drivers for each command. 437862e5a5eSMing Lei */ 438862e5a5eSMing Lei sg_unmark_end(*sg); 439862e5a5eSMing Lei return sg_next(*sg); 440862e5a5eSMing Lei } 441862e5a5eSMing Lei 442862e5a5eSMing Lei static unsigned blk_bvec_map_sg(struct request_queue *q, 443862e5a5eSMing Lei struct bio_vec *bvec, struct scatterlist *sglist, 444862e5a5eSMing Lei struct scatterlist **sg) 445862e5a5eSMing Lei { 446862e5a5eSMing Lei unsigned nbytes = bvec->bv_len; 4478a96a0e4SChristoph Hellwig unsigned nsegs = 0, total = 0; 448862e5a5eSMing Lei 449862e5a5eSMing Lei while (nbytes > 0) { 4508a96a0e4SChristoph Hellwig unsigned offset = bvec->bv_offset + total; 451c55ddd90SChristoph Hellwig unsigned len = min(get_max_segment_size(&q->limits, 452c55ddd90SChristoph Hellwig bvec->bv_page, offset), nbytes); 453f9f76879SChristoph Hellwig struct page *page = bvec->bv_page; 454f9f76879SChristoph Hellwig 455f9f76879SChristoph Hellwig /* 456f9f76879SChristoph Hellwig * Unfortunately a fair number of drivers barf on scatterlists 457f9f76879SChristoph Hellwig * that have an offset larger than PAGE_SIZE, despite other 458f9f76879SChristoph Hellwig * subsystems dealing with that invariant just fine. For now 459f9f76879SChristoph Hellwig * stick to the legacy format where we never present those from 460f9f76879SChristoph Hellwig * the block layer, but the code below should be removed once 461f9f76879SChristoph Hellwig * these offenders (mostly MMC/SD drivers) are fixed. 462f9f76879SChristoph Hellwig */ 463f9f76879SChristoph Hellwig page += (offset >> PAGE_SHIFT); 464f9f76879SChristoph Hellwig offset &= ~PAGE_MASK; 465862e5a5eSMing Lei 466862e5a5eSMing Lei *sg = blk_next_sg(sg, sglist); 467f9f76879SChristoph Hellwig sg_set_page(*sg, page, len, offset); 468862e5a5eSMing Lei 4698a96a0e4SChristoph Hellwig total += len; 4708a96a0e4SChristoph Hellwig nbytes -= len; 471862e5a5eSMing Lei nsegs++; 472862e5a5eSMing Lei } 473862e5a5eSMing Lei 474862e5a5eSMing Lei return nsegs; 475862e5a5eSMing Lei } 476862e5a5eSMing Lei 47716e3e418SMing Lei static inline int __blk_bvec_map_sg(struct bio_vec bv, 47816e3e418SMing Lei struct scatterlist *sglist, struct scatterlist **sg) 47916e3e418SMing Lei { 48016e3e418SMing Lei *sg = blk_next_sg(sg, sglist); 48116e3e418SMing Lei sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset); 48216e3e418SMing Lei return 1; 48316e3e418SMing Lei } 48416e3e418SMing Lei 485f6970f83SMing Lei /* only try to merge bvecs into one sg if they are from two bios */ 486f6970f83SMing Lei static inline bool 487f6970f83SMing Lei __blk_segment_map_sg_merge(struct request_queue *q, struct bio_vec *bvec, 488f6970f83SMing Lei struct bio_vec *bvprv, struct scatterlist **sg) 489963ab9e5SAsias He { 490963ab9e5SAsias He 491963ab9e5SAsias He int nbytes = bvec->bv_len; 492963ab9e5SAsias He 493f6970f83SMing Lei if (!*sg) 494f6970f83SMing Lei return false; 495f6970f83SMing Lei 496b4b6cb61SMing Lei if ((*sg)->length + nbytes > queue_max_segment_size(q)) 497f6970f83SMing Lei return false; 498f6970f83SMing Lei 4993dccdae5SChristoph Hellwig if (!biovec_phys_mergeable(q, bvprv, bvec)) 500f6970f83SMing Lei return false; 501963ab9e5SAsias He 502963ab9e5SAsias He (*sg)->length += nbytes; 503f6970f83SMing Lei 504f6970f83SMing Lei return true; 505963ab9e5SAsias He } 506963ab9e5SAsias He 5075cb8850cSKent Overstreet static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, 5085cb8850cSKent Overstreet struct scatterlist *sglist, 5095cb8850cSKent Overstreet struct scatterlist **sg) 5105cb8850cSKent Overstreet { 5113f649ab7SKees Cook struct bio_vec bvec, bvprv = { NULL }; 5125cb8850cSKent Overstreet struct bvec_iter iter; 51338417468SChristoph Hellwig int nsegs = 0; 514f6970f83SMing Lei bool new_bio = false; 5155cb8850cSKent Overstreet 516f6970f83SMing Lei for_each_bio(bio) { 517f6970f83SMing Lei bio_for_each_bvec(bvec, bio, iter) { 518f6970f83SMing Lei /* 519f6970f83SMing Lei * Only try to merge bvecs from two bios given we 520f6970f83SMing Lei * have done bio internal merge when adding pages 521f6970f83SMing Lei * to bio 522f6970f83SMing Lei */ 523f6970f83SMing Lei if (new_bio && 524f6970f83SMing Lei __blk_segment_map_sg_merge(q, &bvec, &bvprv, sg)) 525f6970f83SMing Lei goto next_bvec; 526f6970f83SMing Lei 527f6970f83SMing Lei if (bvec.bv_offset + bvec.bv_len <= PAGE_SIZE) 528f6970f83SMing Lei nsegs += __blk_bvec_map_sg(bvec, sglist, sg); 529f6970f83SMing Lei else 530f6970f83SMing Lei nsegs += blk_bvec_map_sg(q, &bvec, sglist, sg); 531f6970f83SMing Lei next_bvec: 532f6970f83SMing Lei new_bio = false; 533f6970f83SMing Lei } 534b21e11c5SMing Lei if (likely(bio->bi_iter.bi_size)) { 535f6970f83SMing Lei bvprv = bvec; 536f6970f83SMing Lei new_bio = true; 537f6970f83SMing Lei } 538b21e11c5SMing Lei } 5395cb8850cSKent Overstreet 5405cb8850cSKent Overstreet return nsegs; 5415cb8850cSKent Overstreet } 5425cb8850cSKent Overstreet 543d6d48196SJens Axboe /* 544d6d48196SJens Axboe * map a request to scatterlist, return number of sg entries setup. Caller 545d6d48196SJens Axboe * must make sure sg can hold rq->nr_phys_segments entries 546d6d48196SJens Axboe */ 54789de1504SChristoph Hellwig int __blk_rq_map_sg(struct request_queue *q, struct request *rq, 54889de1504SChristoph Hellwig struct scatterlist *sglist, struct scatterlist **last_sg) 549d6d48196SJens Axboe { 5505cb8850cSKent Overstreet int nsegs = 0; 551d6d48196SJens Axboe 552f9d03f96SChristoph Hellwig if (rq->rq_flags & RQF_SPECIAL_PAYLOAD) 55389de1504SChristoph Hellwig nsegs = __blk_bvec_map_sg(rq->special_vec, sglist, last_sg); 554f9d03f96SChristoph Hellwig else if (rq->bio) 55589de1504SChristoph Hellwig nsegs = __blk_bios_map_sg(q, rq->bio, sglist, last_sg); 556f18573abSFUJITA Tomonori 55789de1504SChristoph Hellwig if (*last_sg) 55889de1504SChristoph Hellwig sg_mark_end(*last_sg); 559d6d48196SJens Axboe 56012e57f59SMing Lei /* 56112e57f59SMing Lei * Something must have been wrong if the figured number of 56212e57f59SMing Lei * segment is bigger than number of req's physical segments 56312e57f59SMing Lei */ 564f9d03f96SChristoph Hellwig WARN_ON(nsegs > blk_rq_nr_phys_segments(rq)); 56512e57f59SMing Lei 566d6d48196SJens Axboe return nsegs; 567d6d48196SJens Axboe } 56889de1504SChristoph Hellwig EXPORT_SYMBOL(__blk_rq_map_sg); 569d6d48196SJens Axboe 570943b40c8SMing Lei static inline unsigned int blk_rq_get_max_segments(struct request *rq) 571943b40c8SMing Lei { 572943b40c8SMing Lei if (req_op(rq) == REQ_OP_DISCARD) 573943b40c8SMing Lei return queue_max_discard_segments(rq->q); 574943b40c8SMing Lei return queue_max_segments(rq->q); 575943b40c8SMing Lei } 576943b40c8SMing Lei 577badf7f64SChristoph Hellwig static inline unsigned int blk_rq_get_max_sectors(struct request *rq, 578badf7f64SChristoph Hellwig sector_t offset) 579badf7f64SChristoph Hellwig { 580badf7f64SChristoph Hellwig struct request_queue *q = rq->q; 581c8875190SChristoph Hellwig unsigned int max_sectors; 582badf7f64SChristoph Hellwig 583badf7f64SChristoph Hellwig if (blk_rq_is_passthrough(rq)) 584badf7f64SChristoph Hellwig return q->limits.max_hw_sectors; 585badf7f64SChristoph Hellwig 586c8875190SChristoph Hellwig max_sectors = blk_queue_get_max_sectors(q, req_op(rq)); 587badf7f64SChristoph Hellwig if (!q->limits.chunk_sectors || 588badf7f64SChristoph Hellwig req_op(rq) == REQ_OP_DISCARD || 589badf7f64SChristoph Hellwig req_op(rq) == REQ_OP_SECURE_ERASE) 590c8875190SChristoph Hellwig return max_sectors; 591c8875190SChristoph Hellwig return min(max_sectors, 592c8875190SChristoph Hellwig blk_chunk_sectors_left(offset, q->limits.chunk_sectors)); 593badf7f64SChristoph Hellwig } 594badf7f64SChristoph Hellwig 59514ccb66bSChristoph Hellwig static inline int ll_new_hw_segment(struct request *req, struct bio *bio, 59614ccb66bSChristoph Hellwig unsigned int nr_phys_segs) 597d6d48196SJens Axboe { 5986b2b0459STejun Heo if (!blk_cgroup_mergeable(req, bio)) 5996b2b0459STejun Heo goto no_merge; 6006b2b0459STejun Heo 6012705dfb2SMing Lei if (blk_integrity_merge_bio(req->q, req, bio) == false) 60213f05c8dSMartin K. Petersen goto no_merge; 60313f05c8dSMartin K. Petersen 6042705dfb2SMing Lei /* discard request merge won't add new segment */ 6052705dfb2SMing Lei if (req_op(req) == REQ_OP_DISCARD) 6062705dfb2SMing Lei return 1; 6072705dfb2SMing Lei 6082705dfb2SMing Lei if (req->nr_phys_segments + nr_phys_segs > blk_rq_get_max_segments(req)) 60913f05c8dSMartin K. Petersen goto no_merge; 610d6d48196SJens Axboe 611d6d48196SJens Axboe /* 612d6d48196SJens Axboe * This will form the start of a new hw segment. Bump both 613d6d48196SJens Axboe * counters. 614d6d48196SJens Axboe */ 615d6d48196SJens Axboe req->nr_phys_segments += nr_phys_segs; 616d6d48196SJens Axboe return 1; 61713f05c8dSMartin K. Petersen 61813f05c8dSMartin K. Petersen no_merge: 61914ccb66bSChristoph Hellwig req_set_nomerge(req->q, req); 62013f05c8dSMartin K. Petersen return 0; 621d6d48196SJens Axboe } 622d6d48196SJens Axboe 62314ccb66bSChristoph Hellwig int ll_back_merge_fn(struct request *req, struct bio *bio, unsigned int nr_segs) 624d6d48196SJens Axboe { 6255e7c4274SJens Axboe if (req_gap_back_merge(req, bio)) 6265e7c4274SJens Axboe return 0; 6277f39add3SSagi Grimberg if (blk_integrity_rq(req) && 6287f39add3SSagi Grimberg integrity_req_gap_back_merge(req, bio)) 6297f39add3SSagi Grimberg return 0; 630a892c8d5SSatya Tangirala if (!bio_crypt_ctx_back_mergeable(req, bio)) 631a892c8d5SSatya Tangirala return 0; 632f31dc1cdSMartin K. Petersen if (blk_rq_sectors(req) + bio_sectors(bio) > 63317007f39SDamien Le Moal blk_rq_get_max_sectors(req, blk_rq_pos(req))) { 63414ccb66bSChristoph Hellwig req_set_nomerge(req->q, req); 635d6d48196SJens Axboe return 0; 636d6d48196SJens Axboe } 637d6d48196SJens Axboe 63814ccb66bSChristoph Hellwig return ll_new_hw_segment(req, bio, nr_segs); 639d6d48196SJens Axboe } 640d6d48196SJens Axboe 641eda5cc99SChristoph Hellwig static int ll_front_merge_fn(struct request *req, struct bio *bio, 642eda5cc99SChristoph Hellwig unsigned int nr_segs) 643d6d48196SJens Axboe { 6445e7c4274SJens Axboe if (req_gap_front_merge(req, bio)) 6455e7c4274SJens Axboe return 0; 6467f39add3SSagi Grimberg if (blk_integrity_rq(req) && 6477f39add3SSagi Grimberg integrity_req_gap_front_merge(req, bio)) 6487f39add3SSagi Grimberg return 0; 649a892c8d5SSatya Tangirala if (!bio_crypt_ctx_front_mergeable(req, bio)) 650a892c8d5SSatya Tangirala return 0; 651f31dc1cdSMartin K. Petersen if (blk_rq_sectors(req) + bio_sectors(bio) > 65217007f39SDamien Le Moal blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) { 65314ccb66bSChristoph Hellwig req_set_nomerge(req->q, req); 654d6d48196SJens Axboe return 0; 655d6d48196SJens Axboe } 656d6d48196SJens Axboe 65714ccb66bSChristoph Hellwig return ll_new_hw_segment(req, bio, nr_segs); 658d6d48196SJens Axboe } 659d6d48196SJens Axboe 660445251d0SJens Axboe static bool req_attempt_discard_merge(struct request_queue *q, struct request *req, 661445251d0SJens Axboe struct request *next) 662445251d0SJens Axboe { 663445251d0SJens Axboe unsigned short segments = blk_rq_nr_discard_segments(req); 664445251d0SJens Axboe 665445251d0SJens Axboe if (segments >= queue_max_discard_segments(q)) 666445251d0SJens Axboe goto no_merge; 667445251d0SJens Axboe if (blk_rq_sectors(req) + bio_sectors(next->bio) > 668445251d0SJens Axboe blk_rq_get_max_sectors(req, blk_rq_pos(req))) 669445251d0SJens Axboe goto no_merge; 670445251d0SJens Axboe 671445251d0SJens Axboe req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next); 672445251d0SJens Axboe return true; 673445251d0SJens Axboe no_merge: 674445251d0SJens Axboe req_set_nomerge(q, req); 675445251d0SJens Axboe return false; 676445251d0SJens Axboe } 677445251d0SJens Axboe 678d6d48196SJens Axboe static int ll_merge_requests_fn(struct request_queue *q, struct request *req, 679d6d48196SJens Axboe struct request *next) 680d6d48196SJens Axboe { 681d6d48196SJens Axboe int total_phys_segments; 682d6d48196SJens Axboe 6835e7c4274SJens Axboe if (req_gap_back_merge(req, next->bio)) 684854fbb9cSKeith Busch return 0; 685854fbb9cSKeith Busch 686d6d48196SJens Axboe /* 687d6d48196SJens Axboe * Will it become too large? 688d6d48196SJens Axboe */ 689f31dc1cdSMartin K. Petersen if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > 69017007f39SDamien Le Moal blk_rq_get_max_sectors(req, blk_rq_pos(req))) 691d6d48196SJens Axboe return 0; 692d6d48196SJens Axboe 693d6d48196SJens Axboe total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; 694943b40c8SMing Lei if (total_phys_segments > blk_rq_get_max_segments(req)) 695d6d48196SJens Axboe return 0; 696d6d48196SJens Axboe 6976b2b0459STejun Heo if (!blk_cgroup_mergeable(req, next->bio)) 6986b2b0459STejun Heo return 0; 6996b2b0459STejun Heo 7004eaf99beSMartin K. Petersen if (blk_integrity_merge_rq(q, req, next) == false) 70113f05c8dSMartin K. Petersen return 0; 70213f05c8dSMartin K. Petersen 703a892c8d5SSatya Tangirala if (!bio_crypt_ctx_merge_rq(req, next)) 704a892c8d5SSatya Tangirala return 0; 705a892c8d5SSatya Tangirala 706d6d48196SJens Axboe /* Merge is OK... */ 707d6d48196SJens Axboe req->nr_phys_segments = total_phys_segments; 708d6d48196SJens Axboe return 1; 709d6d48196SJens Axboe } 710d6d48196SJens Axboe 71180a761fdSTejun Heo /** 71280a761fdSTejun Heo * blk_rq_set_mixed_merge - mark a request as mixed merge 71380a761fdSTejun Heo * @rq: request to mark as mixed merge 71480a761fdSTejun Heo * 71580a761fdSTejun Heo * Description: 71680a761fdSTejun Heo * @rq is about to be mixed merged. Make sure the attributes 71780a761fdSTejun Heo * which can be mixed are set in each bio and mark @rq as mixed 71880a761fdSTejun Heo * merged. 71980a761fdSTejun Heo */ 72080a761fdSTejun Heo void blk_rq_set_mixed_merge(struct request *rq) 72180a761fdSTejun Heo { 72216458cf3SBart Van Assche blk_opf_t ff = rq->cmd_flags & REQ_FAILFAST_MASK; 72380a761fdSTejun Heo struct bio *bio; 72480a761fdSTejun Heo 725e8064021SChristoph Hellwig if (rq->rq_flags & RQF_MIXED_MERGE) 72680a761fdSTejun Heo return; 72780a761fdSTejun Heo 72880a761fdSTejun Heo /* 72980a761fdSTejun Heo * @rq will no longer represent mixable attributes for all the 73080a761fdSTejun Heo * contained bios. It will just track those of the first one. 73180a761fdSTejun Heo * Distributes the attributs to each bio. 73280a761fdSTejun Heo */ 73380a761fdSTejun Heo for (bio = rq->bio; bio; bio = bio->bi_next) { 7341eff9d32SJens Axboe WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) && 7351eff9d32SJens Axboe (bio->bi_opf & REQ_FAILFAST_MASK) != ff); 7361eff9d32SJens Axboe bio->bi_opf |= ff; 73780a761fdSTejun Heo } 738e8064021SChristoph Hellwig rq->rq_flags |= RQF_MIXED_MERGE; 73980a761fdSTejun Heo } 74080a761fdSTejun Heo 741b9c54f56SKonstantin Khlebnikov static void blk_account_io_merge_request(struct request *req) 74226308eabSJerome Marchand { 74326308eabSJerome Marchand if (blk_do_io_stat(req)) { 744112f158fSMike Snitzer part_stat_lock(); 745b9c54f56SKonstantin Khlebnikov part_stat_inc(req->part, merges[op_stat_group(req_op(req))]); 74626308eabSJerome Marchand part_stat_unlock(); 74726308eabSJerome Marchand } 74826308eabSJerome Marchand } 749b9c54f56SKonstantin Khlebnikov 750e96c0d83SEric Biggers static enum elv_merge blk_try_req_merge(struct request *req, 751e96c0d83SEric Biggers struct request *next) 75269840466SJianchao Wang { 75369840466SJianchao Wang if (blk_discard_mergable(req)) 75469840466SJianchao Wang return ELEVATOR_DISCARD_MERGE; 75569840466SJianchao Wang else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next)) 75669840466SJianchao Wang return ELEVATOR_BACK_MERGE; 75769840466SJianchao Wang 75869840466SJianchao Wang return ELEVATOR_NO_MERGE; 75969840466SJianchao Wang } 76026308eabSJerome Marchand 761d6d48196SJens Axboe /* 762b973cb7eSJens Axboe * For non-mq, this has to be called with the request spinlock acquired. 763b973cb7eSJens Axboe * For mq with scheduling, the appropriate queue wide lock should be held. 764d6d48196SJens Axboe */ 765b973cb7eSJens Axboe static struct request *attempt_merge(struct request_queue *q, 766b973cb7eSJens Axboe struct request *req, struct request *next) 767d6d48196SJens Axboe { 768d6d48196SJens Axboe if (!rq_mergeable(req) || !rq_mergeable(next)) 769b973cb7eSJens Axboe return NULL; 770d6d48196SJens Axboe 771288dab8aSChristoph Hellwig if (req_op(req) != req_op(next)) 772b973cb7eSJens Axboe return NULL; 773f31dc1cdSMartin K. Petersen 77479bb1dbdSChristoph Hellwig if (rq_data_dir(req) != rq_data_dir(next)) 775b973cb7eSJens Axboe return NULL; 776d6d48196SJens Axboe 777668ffc03SDamien Le Moal if (req->ioprio != next->ioprio) 778668ffc03SDamien Le Moal return NULL; 779668ffc03SDamien Le Moal 780cb6934f8SJens Axboe /* 781d6d48196SJens Axboe * If we are allowed to merge, then append bio list 782d6d48196SJens Axboe * from next to rq and release next. merge_requests_fn 783d6d48196SJens Axboe * will have updated segment counts, update sector 784445251d0SJens Axboe * counts here. Handle DISCARDs separately, as they 785445251d0SJens Axboe * have separate settings. 786d6d48196SJens Axboe */ 78769840466SJianchao Wang 78869840466SJianchao Wang switch (blk_try_req_merge(req, next)) { 78969840466SJianchao Wang case ELEVATOR_DISCARD_MERGE: 790445251d0SJens Axboe if (!req_attempt_discard_merge(q, req, next)) 791445251d0SJens Axboe return NULL; 79269840466SJianchao Wang break; 79369840466SJianchao Wang case ELEVATOR_BACK_MERGE: 79469840466SJianchao Wang if (!ll_merge_requests_fn(q, req, next)) 795b973cb7eSJens Axboe return NULL; 79669840466SJianchao Wang break; 79769840466SJianchao Wang default: 79869840466SJianchao Wang return NULL; 79969840466SJianchao Wang } 800d6d48196SJens Axboe 801d6d48196SJens Axboe /* 80280a761fdSTejun Heo * If failfast settings disagree or any of the two is already 80380a761fdSTejun Heo * a mixed merge, mark both as mixed before proceeding. This 80480a761fdSTejun Heo * makes sure that all involved bios have mixable attributes 80580a761fdSTejun Heo * set properly. 80680a761fdSTejun Heo */ 807e8064021SChristoph Hellwig if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) || 80880a761fdSTejun Heo (req->cmd_flags & REQ_FAILFAST_MASK) != 80980a761fdSTejun Heo (next->cmd_flags & REQ_FAILFAST_MASK)) { 81080a761fdSTejun Heo blk_rq_set_mixed_merge(req); 81180a761fdSTejun Heo blk_rq_set_mixed_merge(next); 81280a761fdSTejun Heo } 81380a761fdSTejun Heo 81480a761fdSTejun Heo /* 815522a7775SOmar Sandoval * At this point we have either done a back merge or front merge. We 816522a7775SOmar Sandoval * need the smaller start_time_ns of the merged requests to be the 817522a7775SOmar Sandoval * current request for accounting purposes. 818d6d48196SJens Axboe */ 819522a7775SOmar Sandoval if (next->start_time_ns < req->start_time_ns) 820522a7775SOmar Sandoval req->start_time_ns = next->start_time_ns; 821d6d48196SJens Axboe 822d6d48196SJens Axboe req->biotail->bi_next = next->bio; 823d6d48196SJens Axboe req->biotail = next->biotail; 824d6d48196SJens Axboe 825a2dec7b3STejun Heo req->__data_len += blk_rq_bytes(next); 826d6d48196SJens Axboe 8272a5cf35cSMing Lei if (!blk_discard_mergable(req)) 828d6d48196SJens Axboe elv_merge_requests(q, req, next); 829d6d48196SJens Axboe 83042dad764SJerome Marchand /* 83142dad764SJerome Marchand * 'next' is going away, so update stats accordingly 83242dad764SJerome Marchand */ 833b9c54f56SKonstantin Khlebnikov blk_account_io_merge_request(next); 834d6d48196SJens Axboe 835a54895faSChristoph Hellwig trace_block_rq_merge(next); 836f3bdc62fSJan Kara 837e4d750c9SJens Axboe /* 838e4d750c9SJens Axboe * ownership of bio passed from next to req, return 'next' for 839e4d750c9SJens Axboe * the caller to free 840e4d750c9SJens Axboe */ 8411cd96c24SBoaz Harrosh next->bio = NULL; 842b973cb7eSJens Axboe return next; 843d6d48196SJens Axboe } 844d6d48196SJens Axboe 845eda5cc99SChristoph Hellwig static struct request *attempt_back_merge(struct request_queue *q, 846eda5cc99SChristoph Hellwig struct request *rq) 847d6d48196SJens Axboe { 848d6d48196SJens Axboe struct request *next = elv_latter_request(q, rq); 849d6d48196SJens Axboe 850d6d48196SJens Axboe if (next) 851d6d48196SJens Axboe return attempt_merge(q, rq, next); 852d6d48196SJens Axboe 853b973cb7eSJens Axboe return NULL; 854d6d48196SJens Axboe } 855d6d48196SJens Axboe 856eda5cc99SChristoph Hellwig static struct request *attempt_front_merge(struct request_queue *q, 857eda5cc99SChristoph Hellwig struct request *rq) 858d6d48196SJens Axboe { 859d6d48196SJens Axboe struct request *prev = elv_former_request(q, rq); 860d6d48196SJens Axboe 861d6d48196SJens Axboe if (prev) 862d6d48196SJens Axboe return attempt_merge(q, prev, rq); 863d6d48196SJens Axboe 864b973cb7eSJens Axboe return NULL; 865d6d48196SJens Axboe } 8665e84ea3aSJens Axboe 867fd2ef39cSJan Kara /* 868fd2ef39cSJan Kara * Try to merge 'next' into 'rq'. Return true if the merge happened, false 869fd2ef39cSJan Kara * otherwise. The caller is responsible for freeing 'next' if the merge 870fd2ef39cSJan Kara * happened. 871fd2ef39cSJan Kara */ 872fd2ef39cSJan Kara bool blk_attempt_req_merge(struct request_queue *q, struct request *rq, 8735e84ea3aSJens Axboe struct request *next) 8745e84ea3aSJens Axboe { 875fd2ef39cSJan Kara return attempt_merge(q, rq, next); 8765e84ea3aSJens Axboe } 877050c8ea8STejun Heo 878050c8ea8STejun Heo bool blk_rq_merge_ok(struct request *rq, struct bio *bio) 879050c8ea8STejun Heo { 880e2a60da7SMartin K. Petersen if (!rq_mergeable(rq) || !bio_mergeable(bio)) 881050c8ea8STejun Heo return false; 882050c8ea8STejun Heo 883288dab8aSChristoph Hellwig if (req_op(rq) != bio_op(bio)) 884f31dc1cdSMartin K. Petersen return false; 885f31dc1cdSMartin K. Petersen 886050c8ea8STejun Heo /* different data direction or already started, don't merge */ 887050c8ea8STejun Heo if (bio_data_dir(bio) != rq_data_dir(rq)) 888050c8ea8STejun Heo return false; 889050c8ea8STejun Heo 8906b2b0459STejun Heo /* don't merge across cgroup boundaries */ 8916b2b0459STejun Heo if (!blk_cgroup_mergeable(rq, bio)) 8926b2b0459STejun Heo return false; 8936b2b0459STejun Heo 894050c8ea8STejun Heo /* only merge integrity protected bio into ditto rq */ 8954eaf99beSMartin K. Petersen if (blk_integrity_merge_bio(rq->q, rq, bio) == false) 896050c8ea8STejun Heo return false; 897050c8ea8STejun Heo 898a892c8d5SSatya Tangirala /* Only merge if the crypt contexts are compatible */ 899a892c8d5SSatya Tangirala if (!bio_crypt_rq_ctx_compatible(rq, bio)) 900a892c8d5SSatya Tangirala return false; 901a892c8d5SSatya Tangirala 902668ffc03SDamien Le Moal if (rq->ioprio != bio_prio(bio)) 903668ffc03SDamien Le Moal return false; 904668ffc03SDamien Le Moal 905050c8ea8STejun Heo return true; 906050c8ea8STejun Heo } 907050c8ea8STejun Heo 90834fe7c05SChristoph Hellwig enum elv_merge blk_try_merge(struct request *rq, struct bio *bio) 909050c8ea8STejun Heo { 91069840466SJianchao Wang if (blk_discard_mergable(rq)) 9111e739730SChristoph Hellwig return ELEVATOR_DISCARD_MERGE; 9121e739730SChristoph Hellwig else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) 913050c8ea8STejun Heo return ELEVATOR_BACK_MERGE; 9144f024f37SKent Overstreet else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) 915050c8ea8STejun Heo return ELEVATOR_FRONT_MERGE; 916050c8ea8STejun Heo return ELEVATOR_NO_MERGE; 917050c8ea8STejun Heo } 9188e756373SBaolin Wang 9198e756373SBaolin Wang static void blk_account_io_merge_bio(struct request *req) 9208e756373SBaolin Wang { 9218e756373SBaolin Wang if (!blk_do_io_stat(req)) 9228e756373SBaolin Wang return; 9238e756373SBaolin Wang 9248e756373SBaolin Wang part_stat_lock(); 9258e756373SBaolin Wang part_stat_inc(req->part, merges[op_stat_group(req_op(req))]); 9268e756373SBaolin Wang part_stat_unlock(); 9278e756373SBaolin Wang } 9288e756373SBaolin Wang 929eda5cc99SChristoph Hellwig enum bio_merge_status { 930eda5cc99SChristoph Hellwig BIO_MERGE_OK, 931eda5cc99SChristoph Hellwig BIO_MERGE_NONE, 932eda5cc99SChristoph Hellwig BIO_MERGE_FAILED, 933eda5cc99SChristoph Hellwig }; 934eda5cc99SChristoph Hellwig 935eda5cc99SChristoph Hellwig static enum bio_merge_status bio_attempt_back_merge(struct request *req, 936eda5cc99SChristoph Hellwig struct bio *bio, unsigned int nr_segs) 9378e756373SBaolin Wang { 93816458cf3SBart Van Assche const blk_opf_t ff = bio->bi_opf & REQ_FAILFAST_MASK; 9398e756373SBaolin Wang 9408e756373SBaolin Wang if (!ll_back_merge_fn(req, bio, nr_segs)) 9417d7ca7c5SBaolin Wang return BIO_MERGE_FAILED; 9428e756373SBaolin Wang 943e8a676d6SChristoph Hellwig trace_block_bio_backmerge(bio); 9448e756373SBaolin Wang rq_qos_merge(req->q, req, bio); 9458e756373SBaolin Wang 9468e756373SBaolin Wang if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) 9478e756373SBaolin Wang blk_rq_set_mixed_merge(req); 9488e756373SBaolin Wang 9498e756373SBaolin Wang req->biotail->bi_next = bio; 9508e756373SBaolin Wang req->biotail = bio; 9518e756373SBaolin Wang req->__data_len += bio->bi_iter.bi_size; 9528e756373SBaolin Wang 9538e756373SBaolin Wang bio_crypt_free_ctx(bio); 9548e756373SBaolin Wang 9558e756373SBaolin Wang blk_account_io_merge_bio(req); 9567d7ca7c5SBaolin Wang return BIO_MERGE_OK; 9578e756373SBaolin Wang } 9588e756373SBaolin Wang 959eda5cc99SChristoph Hellwig static enum bio_merge_status bio_attempt_front_merge(struct request *req, 960eda5cc99SChristoph Hellwig struct bio *bio, unsigned int nr_segs) 9618e756373SBaolin Wang { 96216458cf3SBart Van Assche const blk_opf_t ff = bio->bi_opf & REQ_FAILFAST_MASK; 9638e756373SBaolin Wang 9648e756373SBaolin Wang if (!ll_front_merge_fn(req, bio, nr_segs)) 9657d7ca7c5SBaolin Wang return BIO_MERGE_FAILED; 9668e756373SBaolin Wang 967e8a676d6SChristoph Hellwig trace_block_bio_frontmerge(bio); 9688e756373SBaolin Wang rq_qos_merge(req->q, req, bio); 9698e756373SBaolin Wang 9708e756373SBaolin Wang if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) 9718e756373SBaolin Wang blk_rq_set_mixed_merge(req); 9728e756373SBaolin Wang 9738e756373SBaolin Wang bio->bi_next = req->bio; 9748e756373SBaolin Wang req->bio = bio; 9758e756373SBaolin Wang 9768e756373SBaolin Wang req->__sector = bio->bi_iter.bi_sector; 9778e756373SBaolin Wang req->__data_len += bio->bi_iter.bi_size; 9788e756373SBaolin Wang 9798e756373SBaolin Wang bio_crypt_do_front_merge(req, bio); 9808e756373SBaolin Wang 9818e756373SBaolin Wang blk_account_io_merge_bio(req); 9827d7ca7c5SBaolin Wang return BIO_MERGE_OK; 9838e756373SBaolin Wang } 9848e756373SBaolin Wang 985eda5cc99SChristoph Hellwig static enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q, 986eda5cc99SChristoph Hellwig struct request *req, struct bio *bio) 9878e756373SBaolin Wang { 9888e756373SBaolin Wang unsigned short segments = blk_rq_nr_discard_segments(req); 9898e756373SBaolin Wang 9908e756373SBaolin Wang if (segments >= queue_max_discard_segments(q)) 9918e756373SBaolin Wang goto no_merge; 9928e756373SBaolin Wang if (blk_rq_sectors(req) + bio_sectors(bio) > 9938e756373SBaolin Wang blk_rq_get_max_sectors(req, blk_rq_pos(req))) 9948e756373SBaolin Wang goto no_merge; 9958e756373SBaolin Wang 9968e756373SBaolin Wang rq_qos_merge(q, req, bio); 9978e756373SBaolin Wang 9988e756373SBaolin Wang req->biotail->bi_next = bio; 9998e756373SBaolin Wang req->biotail = bio; 10008e756373SBaolin Wang req->__data_len += bio->bi_iter.bi_size; 10018e756373SBaolin Wang req->nr_phys_segments = segments + 1; 10028e756373SBaolin Wang 10038e756373SBaolin Wang blk_account_io_merge_bio(req); 10047d7ca7c5SBaolin Wang return BIO_MERGE_OK; 10058e756373SBaolin Wang no_merge: 10068e756373SBaolin Wang req_set_nomerge(q, req); 10077d7ca7c5SBaolin Wang return BIO_MERGE_FAILED; 10087d7ca7c5SBaolin Wang } 10097d7ca7c5SBaolin Wang 10107d7ca7c5SBaolin Wang static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q, 10117d7ca7c5SBaolin Wang struct request *rq, 10127d7ca7c5SBaolin Wang struct bio *bio, 10137d7ca7c5SBaolin Wang unsigned int nr_segs, 10147d7ca7c5SBaolin Wang bool sched_allow_merge) 10157d7ca7c5SBaolin Wang { 10167d7ca7c5SBaolin Wang if (!blk_rq_merge_ok(rq, bio)) 10177d7ca7c5SBaolin Wang return BIO_MERGE_NONE; 10187d7ca7c5SBaolin Wang 10197d7ca7c5SBaolin Wang switch (blk_try_merge(rq, bio)) { 10207d7ca7c5SBaolin Wang case ELEVATOR_BACK_MERGE: 1021265600b7SBaolin Wang if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio)) 10227d7ca7c5SBaolin Wang return bio_attempt_back_merge(rq, bio, nr_segs); 10237d7ca7c5SBaolin Wang break; 10247d7ca7c5SBaolin Wang case ELEVATOR_FRONT_MERGE: 1025265600b7SBaolin Wang if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio)) 10267d7ca7c5SBaolin Wang return bio_attempt_front_merge(rq, bio, nr_segs); 10277d7ca7c5SBaolin Wang break; 10287d7ca7c5SBaolin Wang case ELEVATOR_DISCARD_MERGE: 10297d7ca7c5SBaolin Wang return bio_attempt_discard_merge(q, rq, bio); 10307d7ca7c5SBaolin Wang default: 10317d7ca7c5SBaolin Wang return BIO_MERGE_NONE; 10327d7ca7c5SBaolin Wang } 10337d7ca7c5SBaolin Wang 10347d7ca7c5SBaolin Wang return BIO_MERGE_FAILED; 10358e756373SBaolin Wang } 10368e756373SBaolin Wang 10378e756373SBaolin Wang /** 10388e756373SBaolin Wang * blk_attempt_plug_merge - try to merge with %current's plugged list 10398e756373SBaolin Wang * @q: request_queue new bio is being queued at 10408e756373SBaolin Wang * @bio: new bio being queued 10418e756373SBaolin Wang * @nr_segs: number of segments in @bio 104287c037d1SJens Axboe * from the passed in @q already in the plug list 10438e756373SBaolin Wang * 1044d38a9c04SJens Axboe * Determine whether @bio being queued on @q can be merged with the previous 1045d38a9c04SJens Axboe * request on %current's plugged list. Returns %true if merge was successful, 10468e756373SBaolin Wang * otherwise %false. 10478e756373SBaolin Wang * 10488e756373SBaolin Wang * Plugging coalesces IOs from the same issuer for the same purpose without 10498e756373SBaolin Wang * going through @q->queue_lock. As such it's more of an issuing mechanism 10508e756373SBaolin Wang * than scheduling, and the request, while may have elvpriv data, is not 10518e756373SBaolin Wang * added on the elevator at this point. In addition, we don't have 10528e756373SBaolin Wang * reliable access to the elevator outside queue lock. Only check basic 10538e756373SBaolin Wang * merging parameters without querying the elevator. 10548e756373SBaolin Wang * 10558e756373SBaolin Wang * Caller must ensure !blk_queue_nomerges(q) beforehand. 10568e756373SBaolin Wang */ 10578e756373SBaolin Wang bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio, 10580c5bcc92SChristoph Hellwig unsigned int nr_segs) 10598e756373SBaolin Wang { 10608e756373SBaolin Wang struct blk_plug *plug; 10618e756373SBaolin Wang struct request *rq; 10628e756373SBaolin Wang 10636deacb3bSChristoph Hellwig plug = blk_mq_plug(bio); 1064bc490f81SJens Axboe if (!plug || rq_list_empty(plug->mq_list)) 10658e756373SBaolin Wang return false; 10668e756373SBaolin Wang 10675b205071SJens Axboe rq_list_for_each(&plug->mq_list, rq) { 106887c037d1SJens Axboe if (rq->q == q) { 1069a1cb6537SMing Lei if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) == 1070a1cb6537SMing Lei BIO_MERGE_OK) 10718e756373SBaolin Wang return true; 10725b205071SJens Axboe break; 10735b205071SJens Axboe } 10745b205071SJens Axboe 10755b205071SJens Axboe /* 10765b205071SJens Axboe * Only keep iterating plug list for merges if we have multiple 10775b205071SJens Axboe * queues 10785b205071SJens Axboe */ 10795b205071SJens Axboe if (!plug->multiple_queues) 10805b205071SJens Axboe break; 1081a1cb6537SMing Lei } 10828e756373SBaolin Wang return false; 10838e756373SBaolin Wang } 1084bdc6a287SBaolin Wang 1085bdc6a287SBaolin Wang /* 1086bdc6a287SBaolin Wang * Iterate list of requests and see if we can merge this bio with any 1087bdc6a287SBaolin Wang * of them. 1088bdc6a287SBaolin Wang */ 1089bdc6a287SBaolin Wang bool blk_bio_list_merge(struct request_queue *q, struct list_head *list, 1090bdc6a287SBaolin Wang struct bio *bio, unsigned int nr_segs) 1091bdc6a287SBaolin Wang { 1092bdc6a287SBaolin Wang struct request *rq; 1093bdc6a287SBaolin Wang int checked = 8; 1094bdc6a287SBaolin Wang 1095bdc6a287SBaolin Wang list_for_each_entry_reverse(rq, list, queuelist) { 1096bdc6a287SBaolin Wang if (!checked--) 1097bdc6a287SBaolin Wang break; 1098bdc6a287SBaolin Wang 10997d7ca7c5SBaolin Wang switch (blk_attempt_bio_merge(q, rq, bio, nr_segs, true)) { 11007d7ca7c5SBaolin Wang case BIO_MERGE_NONE: 1101bdc6a287SBaolin Wang continue; 11027d7ca7c5SBaolin Wang case BIO_MERGE_OK: 11037d7ca7c5SBaolin Wang return true; 11047d7ca7c5SBaolin Wang case BIO_MERGE_FAILED: 11057d7ca7c5SBaolin Wang return false; 1106bdc6a287SBaolin Wang } 1107bdc6a287SBaolin Wang 1108bdc6a287SBaolin Wang } 1109bdc6a287SBaolin Wang 1110bdc6a287SBaolin Wang return false; 1111bdc6a287SBaolin Wang } 1112bdc6a287SBaolin Wang EXPORT_SYMBOL_GPL(blk_bio_list_merge); 1113eda5cc99SChristoph Hellwig 1114eda5cc99SChristoph Hellwig bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio, 1115eda5cc99SChristoph Hellwig unsigned int nr_segs, struct request **merged_request) 1116eda5cc99SChristoph Hellwig { 1117eda5cc99SChristoph Hellwig struct request *rq; 1118eda5cc99SChristoph Hellwig 1119eda5cc99SChristoph Hellwig switch (elv_merge(q, &rq, bio)) { 1120eda5cc99SChristoph Hellwig case ELEVATOR_BACK_MERGE: 1121eda5cc99SChristoph Hellwig if (!blk_mq_sched_allow_merge(q, rq, bio)) 1122eda5cc99SChristoph Hellwig return false; 1123eda5cc99SChristoph Hellwig if (bio_attempt_back_merge(rq, bio, nr_segs) != BIO_MERGE_OK) 1124eda5cc99SChristoph Hellwig return false; 1125eda5cc99SChristoph Hellwig *merged_request = attempt_back_merge(q, rq); 1126eda5cc99SChristoph Hellwig if (!*merged_request) 1127eda5cc99SChristoph Hellwig elv_merged_request(q, rq, ELEVATOR_BACK_MERGE); 1128eda5cc99SChristoph Hellwig return true; 1129eda5cc99SChristoph Hellwig case ELEVATOR_FRONT_MERGE: 1130eda5cc99SChristoph Hellwig if (!blk_mq_sched_allow_merge(q, rq, bio)) 1131eda5cc99SChristoph Hellwig return false; 1132eda5cc99SChristoph Hellwig if (bio_attempt_front_merge(rq, bio, nr_segs) != BIO_MERGE_OK) 1133eda5cc99SChristoph Hellwig return false; 1134eda5cc99SChristoph Hellwig *merged_request = attempt_front_merge(q, rq); 1135eda5cc99SChristoph Hellwig if (!*merged_request) 1136eda5cc99SChristoph Hellwig elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE); 1137eda5cc99SChristoph Hellwig return true; 1138eda5cc99SChristoph Hellwig case ELEVATOR_DISCARD_MERGE: 1139eda5cc99SChristoph Hellwig return bio_attempt_discard_merge(q, rq, bio) == BIO_MERGE_OK; 1140eda5cc99SChristoph Hellwig default: 1141eda5cc99SChristoph Hellwig return false; 1142eda5cc99SChristoph Hellwig } 1143eda5cc99SChristoph Hellwig } 1144eda5cc99SChristoph Hellwig EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge); 1145