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; 85*c55ddd90SChristoph 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*c55ddd90SChristoph Hellwig static unsigned int bio_allowed_max_sectors(struct queue_limits *lim) 104b6dc6198SChristoph Hellwig { 105*c55ddd90SChristoph Hellwig return round_down(UINT_MAX, lim->logical_block_size) >> SECTOR_SHIFT; 106b6dc6198SChristoph Hellwig } 107b6dc6198SChristoph Hellwig 108*c55ddd90SChristoph Hellwig static struct bio *bio_split_discard(struct bio *bio, struct queue_limits *lim, 1095a97806fSChristoph Hellwig unsigned *nsegs, struct bio_set *bs) 11054efd50bSKent Overstreet { 11154efd50bSKent Overstreet unsigned int max_discard_sectors, granularity; 11254efd50bSKent Overstreet sector_t tmp; 11354efd50bSKent Overstreet unsigned split_sectors; 11454efd50bSKent Overstreet 115bdced438SMing Lei *nsegs = 1; 116bdced438SMing Lei 11754efd50bSKent Overstreet /* Zero-sector (unknown) and one-sector granularities are the same. */ 118*c55ddd90SChristoph Hellwig granularity = max(lim->discard_granularity >> 9, 1U); 11954efd50bSKent Overstreet 120*c55ddd90SChristoph Hellwig max_discard_sectors = 121*c55ddd90SChristoph Hellwig min(lim->max_discard_sectors, bio_allowed_max_sectors(lim)); 12254efd50bSKent Overstreet max_discard_sectors -= max_discard_sectors % granularity; 12354efd50bSKent Overstreet 12454efd50bSKent Overstreet if (unlikely(!max_discard_sectors)) { 12554efd50bSKent Overstreet /* XXX: warn */ 12654efd50bSKent Overstreet return NULL; 12754efd50bSKent Overstreet } 12854efd50bSKent Overstreet 12954efd50bSKent Overstreet if (bio_sectors(bio) <= max_discard_sectors) 13054efd50bSKent Overstreet return NULL; 13154efd50bSKent Overstreet 13254efd50bSKent Overstreet split_sectors = max_discard_sectors; 13354efd50bSKent Overstreet 13454efd50bSKent Overstreet /* 13554efd50bSKent Overstreet * If the next starting sector would be misaligned, stop the discard at 13654efd50bSKent Overstreet * the previous aligned sector. 13754efd50bSKent Overstreet */ 138*c55ddd90SChristoph Hellwig tmp = bio->bi_iter.bi_sector + split_sectors - 139*c55ddd90SChristoph Hellwig ((lim->discard_alignment >> 9) % granularity); 14054efd50bSKent Overstreet tmp = sector_div(tmp, granularity); 14154efd50bSKent Overstreet 14254efd50bSKent Overstreet if (split_sectors > tmp) 14354efd50bSKent Overstreet split_sectors -= tmp; 14454efd50bSKent Overstreet 14554efd50bSKent Overstreet return bio_split(bio, split_sectors, GFP_NOIO, bs); 14654efd50bSKent Overstreet } 14754efd50bSKent Overstreet 1485a97806fSChristoph Hellwig static struct bio *bio_split_write_zeroes(struct bio *bio, 149*c55ddd90SChristoph Hellwig struct queue_limits *lim, unsigned *nsegs, struct bio_set *bs) 150885fa13fSChristoph Hellwig { 151d665e12aSChristoph Hellwig *nsegs = 0; 152*c55ddd90SChristoph Hellwig if (!lim->max_write_zeroes_sectors) 153885fa13fSChristoph Hellwig return NULL; 154*c55ddd90SChristoph Hellwig if (bio_sectors(bio) <= lim->max_write_zeroes_sectors) 155885fa13fSChristoph Hellwig return NULL; 156*c55ddd90SChristoph Hellwig return bio_split(bio, lim->max_write_zeroes_sectors, GFP_NOIO, bs); 157885fa13fSChristoph Hellwig } 158885fa13fSChristoph Hellwig 1599cc5169cSBart Van Assche /* 1609cc5169cSBart Van Assche * Return the maximum number of sectors from the start of a bio that may be 1619cc5169cSBart Van Assche * submitted as a single request to a block device. If enough sectors remain, 1629cc5169cSBart Van Assche * align the end to the physical block size. Otherwise align the end to the 1639cc5169cSBart Van Assche * logical block size. This approach minimizes the number of non-aligned 1649cc5169cSBart Van Assche * requests that are submitted to a block device if the start of a bio is not 1659cc5169cSBart Van Assche * aligned to a physical block boundary. 1669cc5169cSBart Van Assche */ 1675a97806fSChristoph Hellwig static inline unsigned get_max_io_size(struct bio *bio, 168*c55ddd90SChristoph Hellwig struct queue_limits *lim) 169d0e5fbb0SMing Lei { 170*c55ddd90SChristoph Hellwig unsigned pbs = lim->physical_block_size >> SECTOR_SHIFT; 171*c55ddd90SChristoph Hellwig unsigned lbs = lim->logical_block_size >> SECTOR_SHIFT; 172*c55ddd90SChristoph Hellwig unsigned max_sectors = lim->max_sectors, start, end; 173d0e5fbb0SMing Lei 174*c55ddd90SChristoph Hellwig if (lim->chunk_sectors) { 175efef739dSChristoph Hellwig max_sectors = min(max_sectors, 176efef739dSChristoph Hellwig blk_chunk_sectors_left(bio->bi_iter.bi_sector, 177*c55ddd90SChristoph Hellwig lim->chunk_sectors)); 178efef739dSChristoph Hellwig } 179d0e5fbb0SMing Lei 18084613bedSChristoph Hellwig start = bio->bi_iter.bi_sector & (pbs - 1); 18184613bedSChristoph Hellwig end = (start + max_sectors) & ~(pbs - 1); 18284613bedSChristoph Hellwig if (end > start) 18384613bedSChristoph Hellwig return end - start; 18484613bedSChristoph Hellwig return max_sectors & ~(lbs - 1); 185d0e5fbb0SMing Lei } 186d0e5fbb0SMing Lei 187*c55ddd90SChristoph Hellwig static inline unsigned get_max_segment_size(struct queue_limits *lim, 188*c55ddd90SChristoph Hellwig struct page *start_page, unsigned long offset) 189dcebd755SMing Lei { 190*c55ddd90SChristoph Hellwig unsigned long mask = lim->seg_boundary_mask; 191dcebd755SMing Lei 192429120f3SMing Lei offset = mask & (page_to_phys(start_page) + offset); 1934a2f704eSMing Lei 1944a2f704eSMing Lei /* 1954a2f704eSMing Lei * overflow may be triggered in case of zero page physical address 1964a2f704eSMing Lei * on 32bit arch, use queue's max segment size when that happens. 1974a2f704eSMing Lei */ 1984a2f704eSMing Lei return min_not_zero(mask - offset + 1, 199*c55ddd90SChristoph Hellwig (unsigned long)lim->max_segment_size); 200dcebd755SMing Lei } 201dcebd755SMing Lei 202708b25b3SBart Van Assche /** 203708b25b3SBart Van Assche * bvec_split_segs - verify whether or not a bvec should be split in the middle 204*c55ddd90SChristoph Hellwig * @lim: [in] queue limits to split based on 205708b25b3SBart Van Assche * @bv: [in] bvec to examine 206708b25b3SBart Van Assche * @nsegs: [in,out] Number of segments in the bio being built. Incremented 207708b25b3SBart Van Assche * by the number of segments from @bv that may be appended to that 208708b25b3SBart Van Assche * bio without exceeding @max_segs 20967927d22SKeith Busch * @bytes: [in,out] Number of bytes in the bio being built. Incremented 21067927d22SKeith Busch * by the number of bytes from @bv that may be appended to that 21167927d22SKeith Busch * bio without exceeding @max_bytes 212708b25b3SBart Van Assche * @max_segs: [in] upper bound for *@nsegs 21367927d22SKeith Busch * @max_bytes: [in] upper bound for *@bytes 214708b25b3SBart Van Assche * 215708b25b3SBart Van Assche * When splitting a bio, it can happen that a bvec is encountered that is too 216708b25b3SBart Van Assche * big to fit in a single segment and hence that it has to be split in the 217708b25b3SBart Van Assche * middle. This function verifies whether or not that should happen. The value 218708b25b3SBart Van Assche * %true is returned if and only if appending the entire @bv to a bio with 219708b25b3SBart Van Assche * *@nsegs segments and *@sectors sectors would make that bio unacceptable for 220708b25b3SBart Van Assche * the block driver. 221dcebd755SMing Lei */ 222*c55ddd90SChristoph Hellwig static bool bvec_split_segs(struct queue_limits *lim, const struct bio_vec *bv, 223*c55ddd90SChristoph Hellwig unsigned *nsegs, unsigned *bytes, unsigned max_segs, 22467927d22SKeith Busch unsigned max_bytes) 225dcebd755SMing Lei { 22667927d22SKeith Busch unsigned max_len = min(max_bytes, UINT_MAX) - *bytes; 227708b25b3SBart Van Assche unsigned len = min(bv->bv_len, max_len); 228dcebd755SMing Lei unsigned total_len = 0; 229ff9811b3SBart Van Assche unsigned seg_size = 0; 230dcebd755SMing Lei 231ff9811b3SBart Van Assche while (len && *nsegs < max_segs) { 232*c55ddd90SChristoph Hellwig seg_size = get_max_segment_size(lim, bv->bv_page, 233429120f3SMing Lei bv->bv_offset + total_len); 234dcebd755SMing Lei seg_size = min(seg_size, len); 235dcebd755SMing Lei 236ff9811b3SBart Van Assche (*nsegs)++; 237dcebd755SMing Lei total_len += seg_size; 238dcebd755SMing Lei len -= seg_size; 239dcebd755SMing Lei 240*c55ddd90SChristoph Hellwig if ((bv->bv_offset + total_len) & lim->virt_boundary_mask) 241dcebd755SMing Lei break; 242dcebd755SMing Lei } 243dcebd755SMing Lei 24467927d22SKeith Busch *bytes += total_len; 245dcebd755SMing Lei 246708b25b3SBart Van Assche /* tell the caller to split the bvec if it is too big to fit */ 247708b25b3SBart Van Assche return len > 0 || bv->bv_len > max_len; 248dcebd755SMing Lei } 249dcebd755SMing Lei 250dad77584SBart Van Assche /** 2515a97806fSChristoph Hellwig * bio_split_rw - split a bio in two bios 252dad77584SBart Van Assche * @bio: [in] bio to be split 253*c55ddd90SChristoph Hellwig * @lim: [in] queue limits to split based on 254dad77584SBart Van Assche * @segs: [out] number of segments in the bio with the first half of the sectors 2555a97806fSChristoph Hellwig * @bs: [in] bio set to allocate the clone from 256a85b3637SChristoph Hellwig * @max_bytes: [in] maximum number of bytes per bio 257dad77584SBart Van Assche * 258dad77584SBart Van Assche * Clone @bio, update the bi_iter of the clone to represent the first sectors 259dad77584SBart Van Assche * of @bio and update @bio->bi_iter to represent the remaining sectors. The 260dad77584SBart Van Assche * following is guaranteed for the cloned bio: 261a85b3637SChristoph Hellwig * - That it has at most @max_bytes worth of data 262dad77584SBart Van Assche * - That it has at most queue_max_segments(@q) segments. 263dad77584SBart Van Assche * 264dad77584SBart Van Assche * Except for discard requests the cloned bio will point at the bi_io_vec of 265dad77584SBart Van Assche * the original bio. It is the responsibility of the caller to ensure that the 266dad77584SBart Van Assche * original bio is not freed before the cloned bio. The caller is also 267dad77584SBart Van Assche * responsible for ensuring that @bs is only destroyed after processing of the 268dad77584SBart Van Assche * split bio has finished. 269dad77584SBart Van Assche */ 270*c55ddd90SChristoph Hellwig static struct bio *bio_split_rw(struct bio *bio, struct queue_limits *lim, 271a85b3637SChristoph Hellwig unsigned *segs, struct bio_set *bs, unsigned max_bytes) 27254efd50bSKent Overstreet { 2735014c311SJens Axboe struct bio_vec bv, bvprv, *bvprvp = NULL; 27454efd50bSKent Overstreet struct bvec_iter iter; 27567927d22SKeith Busch unsigned nsegs = 0, bytes = 0; 27654efd50bSKent Overstreet 277dcebd755SMing Lei bio_for_each_bvec(bv, bio, iter) { 27854efd50bSKent Overstreet /* 27954efd50bSKent Overstreet * If the queue doesn't support SG gaps and adding this 28054efd50bSKent Overstreet * offset would create a gap, disallow it. 28154efd50bSKent Overstreet */ 282*c55ddd90SChristoph Hellwig if (bvprvp && bvec_gap_to_prev(lim, bvprvp, bv.bv_offset)) 28354efd50bSKent Overstreet goto split; 28454efd50bSKent Overstreet 285*c55ddd90SChristoph Hellwig if (nsegs < lim->max_segments && 28667927d22SKeith Busch bytes + bv.bv_len <= max_bytes && 287708b25b3SBart Van Assche bv.bv_offset + bv.bv_len <= PAGE_SIZE) { 288708b25b3SBart Van Assche nsegs++; 28967927d22SKeith Busch bytes += bv.bv_len; 290*c55ddd90SChristoph Hellwig } else { 291*c55ddd90SChristoph Hellwig if (bvec_split_segs(lim, &bv, &nsegs, &bytes, 292*c55ddd90SChristoph Hellwig lim->max_segments, max_bytes)) 293e36f6204SKeith Busch goto split; 294e36f6204SKeith Busch } 295e36f6204SKeith Busch 29654efd50bSKent Overstreet bvprv = bv; 297578270bfSMing Lei bvprvp = &bvprv; 29854efd50bSKent Overstreet } 29954efd50bSKent Overstreet 300d627065dSChristoph Hellwig *segs = nsegs; 301d627065dSChristoph Hellwig return NULL; 30254efd50bSKent Overstreet split: 303bdced438SMing Lei *segs = nsegs; 304cc29e1bfSJeffle Xu 305cc29e1bfSJeffle Xu /* 30667927d22SKeith Busch * Individual bvecs might not be logical block aligned. Round down the 30767927d22SKeith Busch * split size so that each bio is properly block size aligned, even if 30867927d22SKeith Busch * we do not use the full hardware limits. 30967927d22SKeith Busch */ 310*c55ddd90SChristoph Hellwig bytes = ALIGN_DOWN(bytes, lim->logical_block_size); 31167927d22SKeith Busch 31267927d22SKeith Busch /* 313cc29e1bfSJeffle Xu * Bio splitting may cause subtle trouble such as hang when doing sync 314cc29e1bfSJeffle Xu * iopoll in direct IO routine. Given performance gain of iopoll for 315cc29e1bfSJeffle Xu * big IO can be trival, disable iopoll when split needed. 316cc29e1bfSJeffle Xu */ 3176ce913feSChristoph Hellwig bio_clear_polled(bio); 31867927d22SKeith Busch return bio_split(bio, bytes >> SECTOR_SHIFT, GFP_NOIO, bs); 31954efd50bSKent Overstreet } 32054efd50bSKent Overstreet 321dad77584SBart Van Assche /** 3225a97806fSChristoph Hellwig * __bio_split_to_limits - split a bio to fit the queue limits 3235a97806fSChristoph Hellwig * @bio: bio to be split 324*c55ddd90SChristoph Hellwig * @lim: queue limits to split based on 3255a97806fSChristoph Hellwig * @nr_segs: returns the number of segments in the returned bio 326dad77584SBart Van Assche * 3275a97806fSChristoph Hellwig * Check if @bio needs splitting based on the queue limits, and if so split off 3285a97806fSChristoph Hellwig * a bio fitting the limits from the beginning of @bio and return it. @bio is 3295a97806fSChristoph Hellwig * shortened to the remainder and re-submitted. 3305a97806fSChristoph Hellwig * 3315a97806fSChristoph Hellwig * The split bio is allocated from @q->bio_split, which is provided by the 3325a97806fSChristoph Hellwig * block layer. 333dad77584SBart Van Assche */ 334*c55ddd90SChristoph Hellwig struct bio *__bio_split_to_limits(struct bio *bio, struct queue_limits *lim, 335abd45c15SJens Axboe unsigned int *nr_segs) 33654efd50bSKent Overstreet { 33746754bd0SChristoph Hellwig struct bio_set *bs = &bio->bi_bdev->bd_disk->bio_split; 3385a97806fSChristoph Hellwig struct bio *split; 33954efd50bSKent Overstreet 3405a97806fSChristoph Hellwig switch (bio_op(bio)) { 3417afafc8aSAdrian Hunter case REQ_OP_DISCARD: 3427afafc8aSAdrian Hunter case REQ_OP_SECURE_ERASE: 343*c55ddd90SChristoph Hellwig split = bio_split_discard(bio, lim, nr_segs, bs); 3447afafc8aSAdrian Hunter break; 345a6f0788eSChaitanya Kulkarni case REQ_OP_WRITE_ZEROES: 346*c55ddd90SChristoph Hellwig split = bio_split_write_zeroes(bio, lim, nr_segs, bs); 347a6f0788eSChaitanya Kulkarni break; 3487afafc8aSAdrian Hunter default: 349*c55ddd90SChristoph Hellwig split = bio_split_rw(bio, lim, nr_segs, bs, 350*c55ddd90SChristoph Hellwig get_max_io_size(bio, lim) << SECTOR_SHIFT); 3517afafc8aSAdrian Hunter break; 3527afafc8aSAdrian Hunter } 353bdced438SMing Lei 35454efd50bSKent Overstreet if (split) { 3556ac45aebSMing Lei /* there isn't chance to merge the splitted bio */ 3561eff9d32SJens Axboe split->bi_opf |= REQ_NOMERGE; 3576ac45aebSMing Lei 358957a2b34SMuchun Song blkcg_bio_issue_init(split); 3595a97806fSChristoph Hellwig bio_chain(split, bio); 3605a97806fSChristoph Hellwig trace_block_split(split, bio->bi_iter.bi_sector); 3615a97806fSChristoph Hellwig submit_bio_noacct(bio); 3625a97806fSChristoph Hellwig return split; 36354efd50bSKent Overstreet } 3645a97806fSChristoph Hellwig return bio; 36554efd50bSKent Overstreet } 36614ccb66bSChristoph Hellwig 367dad77584SBart Van Assche /** 3685a97806fSChristoph Hellwig * bio_split_to_limits - split a bio to fit the queue limits 3695a97806fSChristoph Hellwig * @bio: bio to be split 370dad77584SBart Van Assche * 3715a97806fSChristoph Hellwig * Check if @bio needs splitting based on the queue limits of @bio->bi_bdev, and 3725a97806fSChristoph Hellwig * if so split off a bio fitting the limits from the beginning of @bio and 3735a97806fSChristoph Hellwig * return it. @bio is shortened to the remainder and re-submitted. 3745a97806fSChristoph Hellwig * 3755a97806fSChristoph Hellwig * The split bio is allocated from @q->bio_split, which is provided by the 3765a97806fSChristoph Hellwig * block layer. 377dad77584SBart Van Assche */ 3785a97806fSChristoph Hellwig struct bio *bio_split_to_limits(struct bio *bio) 37914ccb66bSChristoph Hellwig { 380*c55ddd90SChristoph Hellwig struct queue_limits *lim = &bdev_get_queue(bio->bi_bdev)->limits; 38114ccb66bSChristoph Hellwig unsigned int nr_segs; 38214ccb66bSChristoph Hellwig 383*c55ddd90SChristoph Hellwig if (bio_may_exceed_limits(bio, lim)) 384*c55ddd90SChristoph Hellwig return __bio_split_to_limits(bio, lim, &nr_segs); 3855a97806fSChristoph Hellwig return bio; 38614ccb66bSChristoph Hellwig } 3875a97806fSChristoph Hellwig EXPORT_SYMBOL(bio_split_to_limits); 38854efd50bSKent Overstreet 389e9cd19c0SChristoph Hellwig unsigned int blk_recalc_rq_segments(struct request *rq) 390d6d48196SJens Axboe { 3916869875fSChristoph Hellwig unsigned int nr_phys_segs = 0; 39267927d22SKeith Busch unsigned int bytes = 0; 393e9cd19c0SChristoph Hellwig struct req_iterator iter; 3946869875fSChristoph Hellwig struct bio_vec bv; 395d6d48196SJens Axboe 396e9cd19c0SChristoph Hellwig if (!rq->bio) 3971e428079SJens Axboe return 0; 398d6d48196SJens Axboe 399e9cd19c0SChristoph Hellwig switch (bio_op(rq->bio)) { 400a6f0788eSChaitanya Kulkarni case REQ_OP_DISCARD: 401a6f0788eSChaitanya Kulkarni case REQ_OP_SECURE_ERASE: 402a958937fSDavid Jeffery if (queue_max_discard_segments(rq->q) > 1) { 403a958937fSDavid Jeffery struct bio *bio = rq->bio; 404a958937fSDavid Jeffery 405a958937fSDavid Jeffery for_each_bio(bio) 406a958937fSDavid Jeffery nr_phys_segs++; 407a958937fSDavid Jeffery return nr_phys_segs; 408a958937fSDavid Jeffery } 409a958937fSDavid Jeffery return 1; 410a6f0788eSChaitanya Kulkarni case REQ_OP_WRITE_ZEROES: 411f9d03f96SChristoph Hellwig return 0; 4122d9b02beSBart Van Assche default: 4132d9b02beSBart Van Assche break; 414a6f0788eSChaitanya Kulkarni } 4155cb8850cSKent Overstreet 416e9cd19c0SChristoph Hellwig rq_for_each_bvec(bv, rq, iter) 417*c55ddd90SChristoph Hellwig bvec_split_segs(&rq->q->limits, &bv, &nr_phys_segs, &bytes, 418708b25b3SBart Van Assche UINT_MAX, UINT_MAX); 4191e428079SJens Axboe return nr_phys_segs; 4201e428079SJens Axboe } 4211e428079SJens Axboe 42248d7727cSMing Lei static inline struct scatterlist *blk_next_sg(struct scatterlist **sg, 423862e5a5eSMing Lei struct scatterlist *sglist) 424862e5a5eSMing Lei { 425862e5a5eSMing Lei if (!*sg) 426862e5a5eSMing Lei return sglist; 427862e5a5eSMing Lei 428862e5a5eSMing Lei /* 429862e5a5eSMing Lei * If the driver previously mapped a shorter list, we could see a 430862e5a5eSMing Lei * termination bit prematurely unless it fully inits the sg table 431862e5a5eSMing Lei * on each mapping. We KNOW that there must be more entries here 432862e5a5eSMing Lei * or the driver would be buggy, so force clear the termination bit 433862e5a5eSMing Lei * to avoid doing a full sg_init_table() in drivers for each command. 434862e5a5eSMing Lei */ 435862e5a5eSMing Lei sg_unmark_end(*sg); 436862e5a5eSMing Lei return sg_next(*sg); 437862e5a5eSMing Lei } 438862e5a5eSMing Lei 439862e5a5eSMing Lei static unsigned blk_bvec_map_sg(struct request_queue *q, 440862e5a5eSMing Lei struct bio_vec *bvec, struct scatterlist *sglist, 441862e5a5eSMing Lei struct scatterlist **sg) 442862e5a5eSMing Lei { 443862e5a5eSMing Lei unsigned nbytes = bvec->bv_len; 4448a96a0e4SChristoph Hellwig unsigned nsegs = 0, total = 0; 445862e5a5eSMing Lei 446862e5a5eSMing Lei while (nbytes > 0) { 4478a96a0e4SChristoph Hellwig unsigned offset = bvec->bv_offset + total; 448*c55ddd90SChristoph Hellwig unsigned len = min(get_max_segment_size(&q->limits, 449*c55ddd90SChristoph Hellwig bvec->bv_page, offset), nbytes); 450f9f76879SChristoph Hellwig struct page *page = bvec->bv_page; 451f9f76879SChristoph Hellwig 452f9f76879SChristoph Hellwig /* 453f9f76879SChristoph Hellwig * Unfortunately a fair number of drivers barf on scatterlists 454f9f76879SChristoph Hellwig * that have an offset larger than PAGE_SIZE, despite other 455f9f76879SChristoph Hellwig * subsystems dealing with that invariant just fine. For now 456f9f76879SChristoph Hellwig * stick to the legacy format where we never present those from 457f9f76879SChristoph Hellwig * the block layer, but the code below should be removed once 458f9f76879SChristoph Hellwig * these offenders (mostly MMC/SD drivers) are fixed. 459f9f76879SChristoph Hellwig */ 460f9f76879SChristoph Hellwig page += (offset >> PAGE_SHIFT); 461f9f76879SChristoph Hellwig offset &= ~PAGE_MASK; 462862e5a5eSMing Lei 463862e5a5eSMing Lei *sg = blk_next_sg(sg, sglist); 464f9f76879SChristoph Hellwig sg_set_page(*sg, page, len, offset); 465862e5a5eSMing Lei 4668a96a0e4SChristoph Hellwig total += len; 4678a96a0e4SChristoph Hellwig nbytes -= len; 468862e5a5eSMing Lei nsegs++; 469862e5a5eSMing Lei } 470862e5a5eSMing Lei 471862e5a5eSMing Lei return nsegs; 472862e5a5eSMing Lei } 473862e5a5eSMing Lei 47416e3e418SMing Lei static inline int __blk_bvec_map_sg(struct bio_vec bv, 47516e3e418SMing Lei struct scatterlist *sglist, struct scatterlist **sg) 47616e3e418SMing Lei { 47716e3e418SMing Lei *sg = blk_next_sg(sg, sglist); 47816e3e418SMing Lei sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset); 47916e3e418SMing Lei return 1; 48016e3e418SMing Lei } 48116e3e418SMing Lei 482f6970f83SMing Lei /* only try to merge bvecs into one sg if they are from two bios */ 483f6970f83SMing Lei static inline bool 484f6970f83SMing Lei __blk_segment_map_sg_merge(struct request_queue *q, struct bio_vec *bvec, 485f6970f83SMing Lei struct bio_vec *bvprv, struct scatterlist **sg) 486963ab9e5SAsias He { 487963ab9e5SAsias He 488963ab9e5SAsias He int nbytes = bvec->bv_len; 489963ab9e5SAsias He 490f6970f83SMing Lei if (!*sg) 491f6970f83SMing Lei return false; 492f6970f83SMing Lei 493b4b6cb61SMing Lei if ((*sg)->length + nbytes > queue_max_segment_size(q)) 494f6970f83SMing Lei return false; 495f6970f83SMing Lei 4963dccdae5SChristoph Hellwig if (!biovec_phys_mergeable(q, bvprv, bvec)) 497f6970f83SMing Lei return false; 498963ab9e5SAsias He 499963ab9e5SAsias He (*sg)->length += nbytes; 500f6970f83SMing Lei 501f6970f83SMing Lei return true; 502963ab9e5SAsias He } 503963ab9e5SAsias He 5045cb8850cSKent Overstreet static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, 5055cb8850cSKent Overstreet struct scatterlist *sglist, 5065cb8850cSKent Overstreet struct scatterlist **sg) 5075cb8850cSKent Overstreet { 5083f649ab7SKees Cook struct bio_vec bvec, bvprv = { NULL }; 5095cb8850cSKent Overstreet struct bvec_iter iter; 51038417468SChristoph Hellwig int nsegs = 0; 511f6970f83SMing Lei bool new_bio = false; 5125cb8850cSKent Overstreet 513f6970f83SMing Lei for_each_bio(bio) { 514f6970f83SMing Lei bio_for_each_bvec(bvec, bio, iter) { 515f6970f83SMing Lei /* 516f6970f83SMing Lei * Only try to merge bvecs from two bios given we 517f6970f83SMing Lei * have done bio internal merge when adding pages 518f6970f83SMing Lei * to bio 519f6970f83SMing Lei */ 520f6970f83SMing Lei if (new_bio && 521f6970f83SMing Lei __blk_segment_map_sg_merge(q, &bvec, &bvprv, sg)) 522f6970f83SMing Lei goto next_bvec; 523f6970f83SMing Lei 524f6970f83SMing Lei if (bvec.bv_offset + bvec.bv_len <= PAGE_SIZE) 525f6970f83SMing Lei nsegs += __blk_bvec_map_sg(bvec, sglist, sg); 526f6970f83SMing Lei else 527f6970f83SMing Lei nsegs += blk_bvec_map_sg(q, &bvec, sglist, sg); 528f6970f83SMing Lei next_bvec: 529f6970f83SMing Lei new_bio = false; 530f6970f83SMing Lei } 531b21e11c5SMing Lei if (likely(bio->bi_iter.bi_size)) { 532f6970f83SMing Lei bvprv = bvec; 533f6970f83SMing Lei new_bio = true; 534f6970f83SMing Lei } 535b21e11c5SMing Lei } 5365cb8850cSKent Overstreet 5375cb8850cSKent Overstreet return nsegs; 5385cb8850cSKent Overstreet } 5395cb8850cSKent Overstreet 540d6d48196SJens Axboe /* 541d6d48196SJens Axboe * map a request to scatterlist, return number of sg entries setup. Caller 542d6d48196SJens Axboe * must make sure sg can hold rq->nr_phys_segments entries 543d6d48196SJens Axboe */ 54489de1504SChristoph Hellwig int __blk_rq_map_sg(struct request_queue *q, struct request *rq, 54589de1504SChristoph Hellwig struct scatterlist *sglist, struct scatterlist **last_sg) 546d6d48196SJens Axboe { 5475cb8850cSKent Overstreet int nsegs = 0; 548d6d48196SJens Axboe 549f9d03f96SChristoph Hellwig if (rq->rq_flags & RQF_SPECIAL_PAYLOAD) 55089de1504SChristoph Hellwig nsegs = __blk_bvec_map_sg(rq->special_vec, sglist, last_sg); 551f9d03f96SChristoph Hellwig else if (rq->bio) 55289de1504SChristoph Hellwig nsegs = __blk_bios_map_sg(q, rq->bio, sglist, last_sg); 553f18573abSFUJITA Tomonori 55489de1504SChristoph Hellwig if (*last_sg) 55589de1504SChristoph Hellwig sg_mark_end(*last_sg); 556d6d48196SJens Axboe 55712e57f59SMing Lei /* 55812e57f59SMing Lei * Something must have been wrong if the figured number of 55912e57f59SMing Lei * segment is bigger than number of req's physical segments 56012e57f59SMing Lei */ 561f9d03f96SChristoph Hellwig WARN_ON(nsegs > blk_rq_nr_phys_segments(rq)); 56212e57f59SMing Lei 563d6d48196SJens Axboe return nsegs; 564d6d48196SJens Axboe } 56589de1504SChristoph Hellwig EXPORT_SYMBOL(__blk_rq_map_sg); 566d6d48196SJens Axboe 567943b40c8SMing Lei static inline unsigned int blk_rq_get_max_segments(struct request *rq) 568943b40c8SMing Lei { 569943b40c8SMing Lei if (req_op(rq) == REQ_OP_DISCARD) 570943b40c8SMing Lei return queue_max_discard_segments(rq->q); 571943b40c8SMing Lei return queue_max_segments(rq->q); 572943b40c8SMing Lei } 573943b40c8SMing Lei 574badf7f64SChristoph Hellwig static inline unsigned int blk_rq_get_max_sectors(struct request *rq, 575badf7f64SChristoph Hellwig sector_t offset) 576badf7f64SChristoph Hellwig { 577badf7f64SChristoph Hellwig struct request_queue *q = rq->q; 578c8875190SChristoph Hellwig unsigned int max_sectors; 579badf7f64SChristoph Hellwig 580badf7f64SChristoph Hellwig if (blk_rq_is_passthrough(rq)) 581badf7f64SChristoph Hellwig return q->limits.max_hw_sectors; 582badf7f64SChristoph Hellwig 583c8875190SChristoph Hellwig max_sectors = blk_queue_get_max_sectors(q, req_op(rq)); 584badf7f64SChristoph Hellwig if (!q->limits.chunk_sectors || 585badf7f64SChristoph Hellwig req_op(rq) == REQ_OP_DISCARD || 586badf7f64SChristoph Hellwig req_op(rq) == REQ_OP_SECURE_ERASE) 587c8875190SChristoph Hellwig return max_sectors; 588c8875190SChristoph Hellwig return min(max_sectors, 589c8875190SChristoph Hellwig blk_chunk_sectors_left(offset, q->limits.chunk_sectors)); 590badf7f64SChristoph Hellwig } 591badf7f64SChristoph Hellwig 59214ccb66bSChristoph Hellwig static inline int ll_new_hw_segment(struct request *req, struct bio *bio, 59314ccb66bSChristoph Hellwig unsigned int nr_phys_segs) 594d6d48196SJens Axboe { 5956b2b0459STejun Heo if (!blk_cgroup_mergeable(req, bio)) 5966b2b0459STejun Heo goto no_merge; 5976b2b0459STejun Heo 5982705dfb2SMing Lei if (blk_integrity_merge_bio(req->q, req, bio) == false) 59913f05c8dSMartin K. Petersen goto no_merge; 60013f05c8dSMartin K. Petersen 6012705dfb2SMing Lei /* discard request merge won't add new segment */ 6022705dfb2SMing Lei if (req_op(req) == REQ_OP_DISCARD) 6032705dfb2SMing Lei return 1; 6042705dfb2SMing Lei 6052705dfb2SMing Lei if (req->nr_phys_segments + nr_phys_segs > blk_rq_get_max_segments(req)) 60613f05c8dSMartin K. Petersen goto no_merge; 607d6d48196SJens Axboe 608d6d48196SJens Axboe /* 609d6d48196SJens Axboe * This will form the start of a new hw segment. Bump both 610d6d48196SJens Axboe * counters. 611d6d48196SJens Axboe */ 612d6d48196SJens Axboe req->nr_phys_segments += nr_phys_segs; 613d6d48196SJens Axboe return 1; 61413f05c8dSMartin K. Petersen 61513f05c8dSMartin K. Petersen no_merge: 61614ccb66bSChristoph Hellwig req_set_nomerge(req->q, req); 61713f05c8dSMartin K. Petersen return 0; 618d6d48196SJens Axboe } 619d6d48196SJens Axboe 62014ccb66bSChristoph Hellwig int ll_back_merge_fn(struct request *req, struct bio *bio, unsigned int nr_segs) 621d6d48196SJens Axboe { 6225e7c4274SJens Axboe if (req_gap_back_merge(req, bio)) 6235e7c4274SJens Axboe return 0; 6247f39add3SSagi Grimberg if (blk_integrity_rq(req) && 6257f39add3SSagi Grimberg integrity_req_gap_back_merge(req, bio)) 6267f39add3SSagi Grimberg return 0; 627a892c8d5SSatya Tangirala if (!bio_crypt_ctx_back_mergeable(req, bio)) 628a892c8d5SSatya Tangirala return 0; 629f31dc1cdSMartin K. Petersen if (blk_rq_sectors(req) + bio_sectors(bio) > 63017007f39SDamien Le Moal blk_rq_get_max_sectors(req, blk_rq_pos(req))) { 63114ccb66bSChristoph Hellwig req_set_nomerge(req->q, req); 632d6d48196SJens Axboe return 0; 633d6d48196SJens Axboe } 634d6d48196SJens Axboe 63514ccb66bSChristoph Hellwig return ll_new_hw_segment(req, bio, nr_segs); 636d6d48196SJens Axboe } 637d6d48196SJens Axboe 638eda5cc99SChristoph Hellwig static int ll_front_merge_fn(struct request *req, struct bio *bio, 639eda5cc99SChristoph Hellwig unsigned int nr_segs) 640d6d48196SJens Axboe { 6415e7c4274SJens Axboe if (req_gap_front_merge(req, bio)) 6425e7c4274SJens Axboe return 0; 6437f39add3SSagi Grimberg if (blk_integrity_rq(req) && 6447f39add3SSagi Grimberg integrity_req_gap_front_merge(req, bio)) 6457f39add3SSagi Grimberg return 0; 646a892c8d5SSatya Tangirala if (!bio_crypt_ctx_front_mergeable(req, bio)) 647a892c8d5SSatya Tangirala return 0; 648f31dc1cdSMartin K. Petersen if (blk_rq_sectors(req) + bio_sectors(bio) > 64917007f39SDamien Le Moal blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) { 65014ccb66bSChristoph Hellwig req_set_nomerge(req->q, req); 651d6d48196SJens Axboe return 0; 652d6d48196SJens Axboe } 653d6d48196SJens Axboe 65414ccb66bSChristoph Hellwig return ll_new_hw_segment(req, bio, nr_segs); 655d6d48196SJens Axboe } 656d6d48196SJens Axboe 657445251d0SJens Axboe static bool req_attempt_discard_merge(struct request_queue *q, struct request *req, 658445251d0SJens Axboe struct request *next) 659445251d0SJens Axboe { 660445251d0SJens Axboe unsigned short segments = blk_rq_nr_discard_segments(req); 661445251d0SJens Axboe 662445251d0SJens Axboe if (segments >= queue_max_discard_segments(q)) 663445251d0SJens Axboe goto no_merge; 664445251d0SJens Axboe if (blk_rq_sectors(req) + bio_sectors(next->bio) > 665445251d0SJens Axboe blk_rq_get_max_sectors(req, blk_rq_pos(req))) 666445251d0SJens Axboe goto no_merge; 667445251d0SJens Axboe 668445251d0SJens Axboe req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next); 669445251d0SJens Axboe return true; 670445251d0SJens Axboe no_merge: 671445251d0SJens Axboe req_set_nomerge(q, req); 672445251d0SJens Axboe return false; 673445251d0SJens Axboe } 674445251d0SJens Axboe 675d6d48196SJens Axboe static int ll_merge_requests_fn(struct request_queue *q, struct request *req, 676d6d48196SJens Axboe struct request *next) 677d6d48196SJens Axboe { 678d6d48196SJens Axboe int total_phys_segments; 679d6d48196SJens Axboe 6805e7c4274SJens Axboe if (req_gap_back_merge(req, next->bio)) 681854fbb9cSKeith Busch return 0; 682854fbb9cSKeith Busch 683d6d48196SJens Axboe /* 684d6d48196SJens Axboe * Will it become too large? 685d6d48196SJens Axboe */ 686f31dc1cdSMartin K. Petersen if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > 68717007f39SDamien Le Moal blk_rq_get_max_sectors(req, blk_rq_pos(req))) 688d6d48196SJens Axboe return 0; 689d6d48196SJens Axboe 690d6d48196SJens Axboe total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; 691943b40c8SMing Lei if (total_phys_segments > blk_rq_get_max_segments(req)) 692d6d48196SJens Axboe return 0; 693d6d48196SJens Axboe 6946b2b0459STejun Heo if (!blk_cgroup_mergeable(req, next->bio)) 6956b2b0459STejun Heo return 0; 6966b2b0459STejun Heo 6974eaf99beSMartin K. Petersen if (blk_integrity_merge_rq(q, req, next) == false) 69813f05c8dSMartin K. Petersen return 0; 69913f05c8dSMartin K. Petersen 700a892c8d5SSatya Tangirala if (!bio_crypt_ctx_merge_rq(req, next)) 701a892c8d5SSatya Tangirala return 0; 702a892c8d5SSatya Tangirala 703d6d48196SJens Axboe /* Merge is OK... */ 704d6d48196SJens Axboe req->nr_phys_segments = total_phys_segments; 705d6d48196SJens Axboe return 1; 706d6d48196SJens Axboe } 707d6d48196SJens Axboe 70880a761fdSTejun Heo /** 70980a761fdSTejun Heo * blk_rq_set_mixed_merge - mark a request as mixed merge 71080a761fdSTejun Heo * @rq: request to mark as mixed merge 71180a761fdSTejun Heo * 71280a761fdSTejun Heo * Description: 71380a761fdSTejun Heo * @rq is about to be mixed merged. Make sure the attributes 71480a761fdSTejun Heo * which can be mixed are set in each bio and mark @rq as mixed 71580a761fdSTejun Heo * merged. 71680a761fdSTejun Heo */ 71780a761fdSTejun Heo void blk_rq_set_mixed_merge(struct request *rq) 71880a761fdSTejun Heo { 71916458cf3SBart Van Assche blk_opf_t ff = rq->cmd_flags & REQ_FAILFAST_MASK; 72080a761fdSTejun Heo struct bio *bio; 72180a761fdSTejun Heo 722e8064021SChristoph Hellwig if (rq->rq_flags & RQF_MIXED_MERGE) 72380a761fdSTejun Heo return; 72480a761fdSTejun Heo 72580a761fdSTejun Heo /* 72680a761fdSTejun Heo * @rq will no longer represent mixable attributes for all the 72780a761fdSTejun Heo * contained bios. It will just track those of the first one. 72880a761fdSTejun Heo * Distributes the attributs to each bio. 72980a761fdSTejun Heo */ 73080a761fdSTejun Heo for (bio = rq->bio; bio; bio = bio->bi_next) { 7311eff9d32SJens Axboe WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) && 7321eff9d32SJens Axboe (bio->bi_opf & REQ_FAILFAST_MASK) != ff); 7331eff9d32SJens Axboe bio->bi_opf |= ff; 73480a761fdSTejun Heo } 735e8064021SChristoph Hellwig rq->rq_flags |= RQF_MIXED_MERGE; 73680a761fdSTejun Heo } 73780a761fdSTejun Heo 738b9c54f56SKonstantin Khlebnikov static void blk_account_io_merge_request(struct request *req) 73926308eabSJerome Marchand { 74026308eabSJerome Marchand if (blk_do_io_stat(req)) { 741112f158fSMike Snitzer part_stat_lock(); 742b9c54f56SKonstantin Khlebnikov part_stat_inc(req->part, merges[op_stat_group(req_op(req))]); 74326308eabSJerome Marchand part_stat_unlock(); 74426308eabSJerome Marchand } 74526308eabSJerome Marchand } 746b9c54f56SKonstantin Khlebnikov 747e96c0d83SEric Biggers static enum elv_merge blk_try_req_merge(struct request *req, 748e96c0d83SEric Biggers struct request *next) 74969840466SJianchao Wang { 75069840466SJianchao Wang if (blk_discard_mergable(req)) 75169840466SJianchao Wang return ELEVATOR_DISCARD_MERGE; 75269840466SJianchao Wang else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next)) 75369840466SJianchao Wang return ELEVATOR_BACK_MERGE; 75469840466SJianchao Wang 75569840466SJianchao Wang return ELEVATOR_NO_MERGE; 75669840466SJianchao Wang } 75726308eabSJerome Marchand 758d6d48196SJens Axboe /* 759b973cb7eSJens Axboe * For non-mq, this has to be called with the request spinlock acquired. 760b973cb7eSJens Axboe * For mq with scheduling, the appropriate queue wide lock should be held. 761d6d48196SJens Axboe */ 762b973cb7eSJens Axboe static struct request *attempt_merge(struct request_queue *q, 763b973cb7eSJens Axboe struct request *req, struct request *next) 764d6d48196SJens Axboe { 765d6d48196SJens Axboe if (!rq_mergeable(req) || !rq_mergeable(next)) 766b973cb7eSJens Axboe return NULL; 767d6d48196SJens Axboe 768288dab8aSChristoph Hellwig if (req_op(req) != req_op(next)) 769b973cb7eSJens Axboe return NULL; 770f31dc1cdSMartin K. Petersen 77179bb1dbdSChristoph Hellwig if (rq_data_dir(req) != rq_data_dir(next)) 772b973cb7eSJens Axboe return NULL; 773d6d48196SJens Axboe 774668ffc03SDamien Le Moal if (req->ioprio != next->ioprio) 775668ffc03SDamien Le Moal return NULL; 776668ffc03SDamien Le Moal 777cb6934f8SJens Axboe /* 778d6d48196SJens Axboe * If we are allowed to merge, then append bio list 779d6d48196SJens Axboe * from next to rq and release next. merge_requests_fn 780d6d48196SJens Axboe * will have updated segment counts, update sector 781445251d0SJens Axboe * counts here. Handle DISCARDs separately, as they 782445251d0SJens Axboe * have separate settings. 783d6d48196SJens Axboe */ 78469840466SJianchao Wang 78569840466SJianchao Wang switch (blk_try_req_merge(req, next)) { 78669840466SJianchao Wang case ELEVATOR_DISCARD_MERGE: 787445251d0SJens Axboe if (!req_attempt_discard_merge(q, req, next)) 788445251d0SJens Axboe return NULL; 78969840466SJianchao Wang break; 79069840466SJianchao Wang case ELEVATOR_BACK_MERGE: 79169840466SJianchao Wang if (!ll_merge_requests_fn(q, req, next)) 792b973cb7eSJens Axboe return NULL; 79369840466SJianchao Wang break; 79469840466SJianchao Wang default: 79569840466SJianchao Wang return NULL; 79669840466SJianchao Wang } 797d6d48196SJens Axboe 798d6d48196SJens Axboe /* 79980a761fdSTejun Heo * If failfast settings disagree or any of the two is already 80080a761fdSTejun Heo * a mixed merge, mark both as mixed before proceeding. This 80180a761fdSTejun Heo * makes sure that all involved bios have mixable attributes 80280a761fdSTejun Heo * set properly. 80380a761fdSTejun Heo */ 804e8064021SChristoph Hellwig if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) || 80580a761fdSTejun Heo (req->cmd_flags & REQ_FAILFAST_MASK) != 80680a761fdSTejun Heo (next->cmd_flags & REQ_FAILFAST_MASK)) { 80780a761fdSTejun Heo blk_rq_set_mixed_merge(req); 80880a761fdSTejun Heo blk_rq_set_mixed_merge(next); 80980a761fdSTejun Heo } 81080a761fdSTejun Heo 81180a761fdSTejun Heo /* 812522a7775SOmar Sandoval * At this point we have either done a back merge or front merge. We 813522a7775SOmar Sandoval * need the smaller start_time_ns of the merged requests to be the 814522a7775SOmar Sandoval * current request for accounting purposes. 815d6d48196SJens Axboe */ 816522a7775SOmar Sandoval if (next->start_time_ns < req->start_time_ns) 817522a7775SOmar Sandoval req->start_time_ns = next->start_time_ns; 818d6d48196SJens Axboe 819d6d48196SJens Axboe req->biotail->bi_next = next->bio; 820d6d48196SJens Axboe req->biotail = next->biotail; 821d6d48196SJens Axboe 822a2dec7b3STejun Heo req->__data_len += blk_rq_bytes(next); 823d6d48196SJens Axboe 8242a5cf35cSMing Lei if (!blk_discard_mergable(req)) 825d6d48196SJens Axboe elv_merge_requests(q, req, next); 826d6d48196SJens Axboe 82742dad764SJerome Marchand /* 82842dad764SJerome Marchand * 'next' is going away, so update stats accordingly 82942dad764SJerome Marchand */ 830b9c54f56SKonstantin Khlebnikov blk_account_io_merge_request(next); 831d6d48196SJens Axboe 832a54895faSChristoph Hellwig trace_block_rq_merge(next); 833f3bdc62fSJan Kara 834e4d750c9SJens Axboe /* 835e4d750c9SJens Axboe * ownership of bio passed from next to req, return 'next' for 836e4d750c9SJens Axboe * the caller to free 837e4d750c9SJens Axboe */ 8381cd96c24SBoaz Harrosh next->bio = NULL; 839b973cb7eSJens Axboe return next; 840d6d48196SJens Axboe } 841d6d48196SJens Axboe 842eda5cc99SChristoph Hellwig static struct request *attempt_back_merge(struct request_queue *q, 843eda5cc99SChristoph Hellwig struct request *rq) 844d6d48196SJens Axboe { 845d6d48196SJens Axboe struct request *next = elv_latter_request(q, rq); 846d6d48196SJens Axboe 847d6d48196SJens Axboe if (next) 848d6d48196SJens Axboe return attempt_merge(q, rq, next); 849d6d48196SJens Axboe 850b973cb7eSJens Axboe return NULL; 851d6d48196SJens Axboe } 852d6d48196SJens Axboe 853eda5cc99SChristoph Hellwig static struct request *attempt_front_merge(struct request_queue *q, 854eda5cc99SChristoph Hellwig struct request *rq) 855d6d48196SJens Axboe { 856d6d48196SJens Axboe struct request *prev = elv_former_request(q, rq); 857d6d48196SJens Axboe 858d6d48196SJens Axboe if (prev) 859d6d48196SJens Axboe return attempt_merge(q, prev, rq); 860d6d48196SJens Axboe 861b973cb7eSJens Axboe return NULL; 862d6d48196SJens Axboe } 8635e84ea3aSJens Axboe 864fd2ef39cSJan Kara /* 865fd2ef39cSJan Kara * Try to merge 'next' into 'rq'. Return true if the merge happened, false 866fd2ef39cSJan Kara * otherwise. The caller is responsible for freeing 'next' if the merge 867fd2ef39cSJan Kara * happened. 868fd2ef39cSJan Kara */ 869fd2ef39cSJan Kara bool blk_attempt_req_merge(struct request_queue *q, struct request *rq, 8705e84ea3aSJens Axboe struct request *next) 8715e84ea3aSJens Axboe { 872fd2ef39cSJan Kara return attempt_merge(q, rq, next); 8735e84ea3aSJens Axboe } 874050c8ea8STejun Heo 875050c8ea8STejun Heo bool blk_rq_merge_ok(struct request *rq, struct bio *bio) 876050c8ea8STejun Heo { 877e2a60da7SMartin K. Petersen if (!rq_mergeable(rq) || !bio_mergeable(bio)) 878050c8ea8STejun Heo return false; 879050c8ea8STejun Heo 880288dab8aSChristoph Hellwig if (req_op(rq) != bio_op(bio)) 881f31dc1cdSMartin K. Petersen return false; 882f31dc1cdSMartin K. Petersen 883050c8ea8STejun Heo /* different data direction or already started, don't merge */ 884050c8ea8STejun Heo if (bio_data_dir(bio) != rq_data_dir(rq)) 885050c8ea8STejun Heo return false; 886050c8ea8STejun Heo 8876b2b0459STejun Heo /* don't merge across cgroup boundaries */ 8886b2b0459STejun Heo if (!blk_cgroup_mergeable(rq, bio)) 8896b2b0459STejun Heo return false; 8906b2b0459STejun Heo 891050c8ea8STejun Heo /* only merge integrity protected bio into ditto rq */ 8924eaf99beSMartin K. Petersen if (blk_integrity_merge_bio(rq->q, rq, bio) == false) 893050c8ea8STejun Heo return false; 894050c8ea8STejun Heo 895a892c8d5SSatya Tangirala /* Only merge if the crypt contexts are compatible */ 896a892c8d5SSatya Tangirala if (!bio_crypt_rq_ctx_compatible(rq, bio)) 897a892c8d5SSatya Tangirala return false; 898a892c8d5SSatya Tangirala 899668ffc03SDamien Le Moal if (rq->ioprio != bio_prio(bio)) 900668ffc03SDamien Le Moal return false; 901668ffc03SDamien Le Moal 902050c8ea8STejun Heo return true; 903050c8ea8STejun Heo } 904050c8ea8STejun Heo 90534fe7c05SChristoph Hellwig enum elv_merge blk_try_merge(struct request *rq, struct bio *bio) 906050c8ea8STejun Heo { 90769840466SJianchao Wang if (blk_discard_mergable(rq)) 9081e739730SChristoph Hellwig return ELEVATOR_DISCARD_MERGE; 9091e739730SChristoph Hellwig else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) 910050c8ea8STejun Heo return ELEVATOR_BACK_MERGE; 9114f024f37SKent Overstreet else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) 912050c8ea8STejun Heo return ELEVATOR_FRONT_MERGE; 913050c8ea8STejun Heo return ELEVATOR_NO_MERGE; 914050c8ea8STejun Heo } 9158e756373SBaolin Wang 9168e756373SBaolin Wang static void blk_account_io_merge_bio(struct request *req) 9178e756373SBaolin Wang { 9188e756373SBaolin Wang if (!blk_do_io_stat(req)) 9198e756373SBaolin Wang return; 9208e756373SBaolin Wang 9218e756373SBaolin Wang part_stat_lock(); 9228e756373SBaolin Wang part_stat_inc(req->part, merges[op_stat_group(req_op(req))]); 9238e756373SBaolin Wang part_stat_unlock(); 9248e756373SBaolin Wang } 9258e756373SBaolin Wang 926eda5cc99SChristoph Hellwig enum bio_merge_status { 927eda5cc99SChristoph Hellwig BIO_MERGE_OK, 928eda5cc99SChristoph Hellwig BIO_MERGE_NONE, 929eda5cc99SChristoph Hellwig BIO_MERGE_FAILED, 930eda5cc99SChristoph Hellwig }; 931eda5cc99SChristoph Hellwig 932eda5cc99SChristoph Hellwig static enum bio_merge_status bio_attempt_back_merge(struct request *req, 933eda5cc99SChristoph Hellwig struct bio *bio, unsigned int nr_segs) 9348e756373SBaolin Wang { 93516458cf3SBart Van Assche const blk_opf_t ff = bio->bi_opf & REQ_FAILFAST_MASK; 9368e756373SBaolin Wang 9378e756373SBaolin Wang if (!ll_back_merge_fn(req, bio, nr_segs)) 9387d7ca7c5SBaolin Wang return BIO_MERGE_FAILED; 9398e756373SBaolin Wang 940e8a676d6SChristoph Hellwig trace_block_bio_backmerge(bio); 9418e756373SBaolin Wang rq_qos_merge(req->q, req, bio); 9428e756373SBaolin Wang 9438e756373SBaolin Wang if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) 9448e756373SBaolin Wang blk_rq_set_mixed_merge(req); 9458e756373SBaolin Wang 9468e756373SBaolin Wang req->biotail->bi_next = bio; 9478e756373SBaolin Wang req->biotail = bio; 9488e756373SBaolin Wang req->__data_len += bio->bi_iter.bi_size; 9498e756373SBaolin Wang 9508e756373SBaolin Wang bio_crypt_free_ctx(bio); 9518e756373SBaolin Wang 9528e756373SBaolin Wang blk_account_io_merge_bio(req); 9537d7ca7c5SBaolin Wang return BIO_MERGE_OK; 9548e756373SBaolin Wang } 9558e756373SBaolin Wang 956eda5cc99SChristoph Hellwig static enum bio_merge_status bio_attempt_front_merge(struct request *req, 957eda5cc99SChristoph Hellwig struct bio *bio, unsigned int nr_segs) 9588e756373SBaolin Wang { 95916458cf3SBart Van Assche const blk_opf_t ff = bio->bi_opf & REQ_FAILFAST_MASK; 9608e756373SBaolin Wang 9618e756373SBaolin Wang if (!ll_front_merge_fn(req, bio, nr_segs)) 9627d7ca7c5SBaolin Wang return BIO_MERGE_FAILED; 9638e756373SBaolin Wang 964e8a676d6SChristoph Hellwig trace_block_bio_frontmerge(bio); 9658e756373SBaolin Wang rq_qos_merge(req->q, req, bio); 9668e756373SBaolin Wang 9678e756373SBaolin Wang if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) 9688e756373SBaolin Wang blk_rq_set_mixed_merge(req); 9698e756373SBaolin Wang 9708e756373SBaolin Wang bio->bi_next = req->bio; 9718e756373SBaolin Wang req->bio = bio; 9728e756373SBaolin Wang 9738e756373SBaolin Wang req->__sector = bio->bi_iter.bi_sector; 9748e756373SBaolin Wang req->__data_len += bio->bi_iter.bi_size; 9758e756373SBaolin Wang 9768e756373SBaolin Wang bio_crypt_do_front_merge(req, bio); 9778e756373SBaolin Wang 9788e756373SBaolin Wang blk_account_io_merge_bio(req); 9797d7ca7c5SBaolin Wang return BIO_MERGE_OK; 9808e756373SBaolin Wang } 9818e756373SBaolin Wang 982eda5cc99SChristoph Hellwig static enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q, 983eda5cc99SChristoph Hellwig struct request *req, struct bio *bio) 9848e756373SBaolin Wang { 9858e756373SBaolin Wang unsigned short segments = blk_rq_nr_discard_segments(req); 9868e756373SBaolin Wang 9878e756373SBaolin Wang if (segments >= queue_max_discard_segments(q)) 9888e756373SBaolin Wang goto no_merge; 9898e756373SBaolin Wang if (blk_rq_sectors(req) + bio_sectors(bio) > 9908e756373SBaolin Wang blk_rq_get_max_sectors(req, blk_rq_pos(req))) 9918e756373SBaolin Wang goto no_merge; 9928e756373SBaolin Wang 9938e756373SBaolin Wang rq_qos_merge(q, req, bio); 9948e756373SBaolin Wang 9958e756373SBaolin Wang req->biotail->bi_next = bio; 9968e756373SBaolin Wang req->biotail = bio; 9978e756373SBaolin Wang req->__data_len += bio->bi_iter.bi_size; 9988e756373SBaolin Wang req->nr_phys_segments = segments + 1; 9998e756373SBaolin Wang 10008e756373SBaolin Wang blk_account_io_merge_bio(req); 10017d7ca7c5SBaolin Wang return BIO_MERGE_OK; 10028e756373SBaolin Wang no_merge: 10038e756373SBaolin Wang req_set_nomerge(q, req); 10047d7ca7c5SBaolin Wang return BIO_MERGE_FAILED; 10057d7ca7c5SBaolin Wang } 10067d7ca7c5SBaolin Wang 10077d7ca7c5SBaolin Wang static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q, 10087d7ca7c5SBaolin Wang struct request *rq, 10097d7ca7c5SBaolin Wang struct bio *bio, 10107d7ca7c5SBaolin Wang unsigned int nr_segs, 10117d7ca7c5SBaolin Wang bool sched_allow_merge) 10127d7ca7c5SBaolin Wang { 10137d7ca7c5SBaolin Wang if (!blk_rq_merge_ok(rq, bio)) 10147d7ca7c5SBaolin Wang return BIO_MERGE_NONE; 10157d7ca7c5SBaolin Wang 10167d7ca7c5SBaolin Wang switch (blk_try_merge(rq, bio)) { 10177d7ca7c5SBaolin Wang case ELEVATOR_BACK_MERGE: 1018265600b7SBaolin Wang if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio)) 10197d7ca7c5SBaolin Wang return bio_attempt_back_merge(rq, bio, nr_segs); 10207d7ca7c5SBaolin Wang break; 10217d7ca7c5SBaolin Wang case ELEVATOR_FRONT_MERGE: 1022265600b7SBaolin Wang if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio)) 10237d7ca7c5SBaolin Wang return bio_attempt_front_merge(rq, bio, nr_segs); 10247d7ca7c5SBaolin Wang break; 10257d7ca7c5SBaolin Wang case ELEVATOR_DISCARD_MERGE: 10267d7ca7c5SBaolin Wang return bio_attempt_discard_merge(q, rq, bio); 10277d7ca7c5SBaolin Wang default: 10287d7ca7c5SBaolin Wang return BIO_MERGE_NONE; 10297d7ca7c5SBaolin Wang } 10307d7ca7c5SBaolin Wang 10317d7ca7c5SBaolin Wang return BIO_MERGE_FAILED; 10328e756373SBaolin Wang } 10338e756373SBaolin Wang 10348e756373SBaolin Wang /** 10358e756373SBaolin Wang * blk_attempt_plug_merge - try to merge with %current's plugged list 10368e756373SBaolin Wang * @q: request_queue new bio is being queued at 10378e756373SBaolin Wang * @bio: new bio being queued 10388e756373SBaolin Wang * @nr_segs: number of segments in @bio 103987c037d1SJens Axboe * from the passed in @q already in the plug list 10408e756373SBaolin Wang * 1041d38a9c04SJens Axboe * Determine whether @bio being queued on @q can be merged with the previous 1042d38a9c04SJens Axboe * request on %current's plugged list. Returns %true if merge was successful, 10438e756373SBaolin Wang * otherwise %false. 10448e756373SBaolin Wang * 10458e756373SBaolin Wang * Plugging coalesces IOs from the same issuer for the same purpose without 10468e756373SBaolin Wang * going through @q->queue_lock. As such it's more of an issuing mechanism 10478e756373SBaolin Wang * than scheduling, and the request, while may have elvpriv data, is not 10488e756373SBaolin Wang * added on the elevator at this point. In addition, we don't have 10498e756373SBaolin Wang * reliable access to the elevator outside queue lock. Only check basic 10508e756373SBaolin Wang * merging parameters without querying the elevator. 10518e756373SBaolin Wang * 10528e756373SBaolin Wang * Caller must ensure !blk_queue_nomerges(q) beforehand. 10538e756373SBaolin Wang */ 10548e756373SBaolin Wang bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio, 10550c5bcc92SChristoph Hellwig unsigned int nr_segs) 10568e756373SBaolin Wang { 10578e756373SBaolin Wang struct blk_plug *plug; 10588e756373SBaolin Wang struct request *rq; 10598e756373SBaolin Wang 10606deacb3bSChristoph Hellwig plug = blk_mq_plug(bio); 1061bc490f81SJens Axboe if (!plug || rq_list_empty(plug->mq_list)) 10628e756373SBaolin Wang return false; 10638e756373SBaolin Wang 10645b205071SJens Axboe rq_list_for_each(&plug->mq_list, rq) { 106587c037d1SJens Axboe if (rq->q == q) { 1066a1cb6537SMing Lei if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) == 1067a1cb6537SMing Lei BIO_MERGE_OK) 10688e756373SBaolin Wang return true; 10695b205071SJens Axboe break; 10705b205071SJens Axboe } 10715b205071SJens Axboe 10725b205071SJens Axboe /* 10735b205071SJens Axboe * Only keep iterating plug list for merges if we have multiple 10745b205071SJens Axboe * queues 10755b205071SJens Axboe */ 10765b205071SJens Axboe if (!plug->multiple_queues) 10775b205071SJens Axboe break; 1078a1cb6537SMing Lei } 10798e756373SBaolin Wang return false; 10808e756373SBaolin Wang } 1081bdc6a287SBaolin Wang 1082bdc6a287SBaolin Wang /* 1083bdc6a287SBaolin Wang * Iterate list of requests and see if we can merge this bio with any 1084bdc6a287SBaolin Wang * of them. 1085bdc6a287SBaolin Wang */ 1086bdc6a287SBaolin Wang bool blk_bio_list_merge(struct request_queue *q, struct list_head *list, 1087bdc6a287SBaolin Wang struct bio *bio, unsigned int nr_segs) 1088bdc6a287SBaolin Wang { 1089bdc6a287SBaolin Wang struct request *rq; 1090bdc6a287SBaolin Wang int checked = 8; 1091bdc6a287SBaolin Wang 1092bdc6a287SBaolin Wang list_for_each_entry_reverse(rq, list, queuelist) { 1093bdc6a287SBaolin Wang if (!checked--) 1094bdc6a287SBaolin Wang break; 1095bdc6a287SBaolin Wang 10967d7ca7c5SBaolin Wang switch (blk_attempt_bio_merge(q, rq, bio, nr_segs, true)) { 10977d7ca7c5SBaolin Wang case BIO_MERGE_NONE: 1098bdc6a287SBaolin Wang continue; 10997d7ca7c5SBaolin Wang case BIO_MERGE_OK: 11007d7ca7c5SBaolin Wang return true; 11017d7ca7c5SBaolin Wang case BIO_MERGE_FAILED: 11027d7ca7c5SBaolin Wang return false; 1103bdc6a287SBaolin Wang } 1104bdc6a287SBaolin Wang 1105bdc6a287SBaolin Wang } 1106bdc6a287SBaolin Wang 1107bdc6a287SBaolin Wang return false; 1108bdc6a287SBaolin Wang } 1109bdc6a287SBaolin Wang EXPORT_SYMBOL_GPL(blk_bio_list_merge); 1110eda5cc99SChristoph Hellwig 1111eda5cc99SChristoph Hellwig bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio, 1112eda5cc99SChristoph Hellwig unsigned int nr_segs, struct request **merged_request) 1113eda5cc99SChristoph Hellwig { 1114eda5cc99SChristoph Hellwig struct request *rq; 1115eda5cc99SChristoph Hellwig 1116eda5cc99SChristoph Hellwig switch (elv_merge(q, &rq, bio)) { 1117eda5cc99SChristoph Hellwig case ELEVATOR_BACK_MERGE: 1118eda5cc99SChristoph Hellwig if (!blk_mq_sched_allow_merge(q, rq, bio)) 1119eda5cc99SChristoph Hellwig return false; 1120eda5cc99SChristoph Hellwig if (bio_attempt_back_merge(rq, bio, nr_segs) != BIO_MERGE_OK) 1121eda5cc99SChristoph Hellwig return false; 1122eda5cc99SChristoph Hellwig *merged_request = attempt_back_merge(q, rq); 1123eda5cc99SChristoph Hellwig if (!*merged_request) 1124eda5cc99SChristoph Hellwig elv_merged_request(q, rq, ELEVATOR_BACK_MERGE); 1125eda5cc99SChristoph Hellwig return true; 1126eda5cc99SChristoph Hellwig case ELEVATOR_FRONT_MERGE: 1127eda5cc99SChristoph Hellwig if (!blk_mq_sched_allow_merge(q, rq, bio)) 1128eda5cc99SChristoph Hellwig return false; 1129eda5cc99SChristoph Hellwig if (bio_attempt_front_merge(rq, bio, nr_segs) != BIO_MERGE_OK) 1130eda5cc99SChristoph Hellwig return false; 1131eda5cc99SChristoph Hellwig *merged_request = attempt_front_merge(q, rq); 1132eda5cc99SChristoph Hellwig if (!*merged_request) 1133eda5cc99SChristoph Hellwig elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE); 1134eda5cc99SChristoph Hellwig return true; 1135eda5cc99SChristoph Hellwig case ELEVATOR_DISCARD_MERGE: 1136eda5cc99SChristoph Hellwig return bio_attempt_discard_merge(q, rq, bio) == BIO_MERGE_OK; 1137eda5cc99SChristoph Hellwig default: 1138eda5cc99SChristoph Hellwig return false; 1139eda5cc99SChristoph Hellwig } 1140eda5cc99SChristoph Hellwig } 1141eda5cc99SChristoph Hellwig EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge); 1142