| 1 | // SPDX-License-Identifier: GPL-2.0 |
| 2 | /* |
| 3 | * Functions related to segment and merge handling |
| 4 | */ |
| 5 | #include <linux/kernel.h> |
| 6 | #include <linux/module.h> |
| 7 | #include <linux/bio.h> |
| 8 | #include <linux/blkdev.h> |
| 9 | #include <linux/blk-integrity.h> |
| 10 | #include <linux/scatterlist.h> |
| 11 | #include <linux/part_stat.h> |
| 12 | #include <linux/blk-cgroup.h> |
| 13 | |
| 14 | #include <trace/events/block.h> |
| 15 | |
| 16 | #include "blk.h" |
| 17 | #include "blk-mq-sched.h" |
| 18 | #include "blk-rq-qos.h" |
| 19 | #include "blk-throttle.h" |
| 20 | |
| 21 | static inline void bio_get_first_bvec(struct bio *bio, struct bio_vec *bv) |
| 22 | { |
| 23 | *bv = mp_bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter); |
| 24 | } |
| 25 | |
| 26 | static inline void bio_get_last_bvec(struct bio *bio, struct bio_vec *bv) |
| 27 | { |
| 28 | struct bvec_iter iter = bio->bi_iter; |
| 29 | int idx; |
| 30 | |
| 31 | bio_get_first_bvec(bio, bv); |
| 32 | if (bv->bv_len == bio->bi_iter.bi_size) |
| 33 | return; /* this bio only has a single bvec */ |
| 34 | |
| 35 | bio_advance_iter(bio, &iter, iter.bi_size); |
| 36 | |
| 37 | if (!iter.bi_bvec_done) |
| 38 | idx = iter.bi_idx - 1; |
| 39 | else /* in the middle of bvec */ |
| 40 | idx = iter.bi_idx; |
| 41 | |
| 42 | *bv = bio->bi_io_vec[idx]; |
| 43 | |
| 44 | /* |
| 45 | * iter.bi_bvec_done records actual length of the last bvec |
| 46 | * if this bio ends in the middle of one io vector |
| 47 | */ |
| 48 | if (iter.bi_bvec_done) |
| 49 | bv->bv_len = iter.bi_bvec_done; |
| 50 | } |
| 51 | |
| 52 | static inline bool bio_will_gap(struct request_queue *q, |
| 53 | struct request *prev_rq, struct bio *prev, struct bio *next) |
| 54 | { |
| 55 | struct bio_vec pb, nb; |
| 56 | |
| 57 | if (!bio_has_data(prev) || !queue_virt_boundary(q)) |
| 58 | return false; |
| 59 | |
| 60 | /* |
| 61 | * Don't merge if the 1st bio starts with non-zero offset, otherwise it |
| 62 | * is quite difficult to respect the sg gap limit. We work hard to |
| 63 | * merge a huge number of small single bios in case of mkfs. |
| 64 | */ |
| 65 | if (prev_rq) |
| 66 | bio_get_first_bvec(prev_rq->bio, &pb); |
| 67 | else |
| 68 | bio_get_first_bvec(prev, &pb); |
| 69 | if (pb.bv_offset & queue_virt_boundary(q)) |
| 70 | return true; |
| 71 | |
| 72 | /* |
| 73 | * We don't need to worry about the situation that the merged segment |
| 74 | * ends in unaligned virt boundary: |
| 75 | * |
| 76 | * - if 'pb' ends aligned, the merged segment ends aligned |
| 77 | * - if 'pb' ends unaligned, the next bio must include |
| 78 | * one single bvec of 'nb', otherwise the 'nb' can't |
| 79 | * merge with 'pb' |
| 80 | */ |
| 81 | bio_get_last_bvec(prev, &pb); |
| 82 | bio_get_first_bvec(next, &nb); |
| 83 | if (biovec_phys_mergeable(q, &pb, &nb)) |
| 84 | return false; |
| 85 | return __bvec_gap_to_prev(&q->limits, &pb, nb.bv_offset); |
| 86 | } |
| 87 | |
| 88 | static inline bool req_gap_back_merge(struct request *req, struct bio *bio) |
| 89 | { |
| 90 | return bio_will_gap(req->q, req, req->biotail, bio); |
| 91 | } |
| 92 | |
| 93 | static inline bool req_gap_front_merge(struct request *req, struct bio *bio) |
| 94 | { |
| 95 | return bio_will_gap(req->q, NULL, bio, req->bio); |
| 96 | } |
| 97 | |
| 98 | /* |
| 99 | * The max size one bio can handle is UINT_MAX becasue bvec_iter.bi_size |
| 100 | * is defined as 'unsigned int', meantime it has to be aligned to with the |
| 101 | * logical block size, which is the minimum accepted unit by hardware. |
| 102 | */ |
| 103 | static unsigned int bio_allowed_max_sectors(const struct queue_limits *lim) |
| 104 | { |
| 105 | return round_down(UINT_MAX, lim->logical_block_size) >> SECTOR_SHIFT; |
| 106 | } |
| 107 | |
| 108 | static struct bio *bio_split_discard(struct bio *bio, |
| 109 | const struct queue_limits *lim, |
| 110 | unsigned *nsegs, struct bio_set *bs) |
| 111 | { |
| 112 | unsigned int max_discard_sectors, granularity; |
| 113 | sector_t tmp; |
| 114 | unsigned split_sectors; |
| 115 | |
| 116 | *nsegs = 1; |
| 117 | |
| 118 | /* Zero-sector (unknown) and one-sector granularities are the same. */ |
| 119 | granularity = max(lim->discard_granularity >> 9, 1U); |
| 120 | |
| 121 | max_discard_sectors = |
| 122 | min(lim->max_discard_sectors, bio_allowed_max_sectors(lim)); |
| 123 | max_discard_sectors -= max_discard_sectors % granularity; |
| 124 | |
| 125 | if (unlikely(!max_discard_sectors)) { |
| 126 | /* XXX: warn */ |
| 127 | return NULL; |
| 128 | } |
| 129 | |
| 130 | if (bio_sectors(bio) <= max_discard_sectors) |
| 131 | return NULL; |
| 132 | |
| 133 | split_sectors = max_discard_sectors; |
| 134 | |
| 135 | /* |
| 136 | * If the next starting sector would be misaligned, stop the discard at |
| 137 | * the previous aligned sector. |
| 138 | */ |
| 139 | tmp = bio->bi_iter.bi_sector + split_sectors - |
| 140 | ((lim->discard_alignment >> 9) % granularity); |
| 141 | tmp = sector_div(tmp, granularity); |
| 142 | |
| 143 | if (split_sectors > tmp) |
| 144 | split_sectors -= tmp; |
| 145 | |
| 146 | return bio_split(bio, split_sectors, GFP_NOIO, bs); |
| 147 | } |
| 148 | |
| 149 | static struct bio *bio_split_write_zeroes(struct bio *bio, |
| 150 | const struct queue_limits *lim, |
| 151 | unsigned *nsegs, struct bio_set *bs) |
| 152 | { |
| 153 | *nsegs = 0; |
| 154 | if (!lim->max_write_zeroes_sectors) |
| 155 | return NULL; |
| 156 | if (bio_sectors(bio) <= lim->max_write_zeroes_sectors) |
| 157 | return NULL; |
| 158 | return bio_split(bio, lim->max_write_zeroes_sectors, GFP_NOIO, bs); |
| 159 | } |
| 160 | |
| 161 | /* |
| 162 | * Return the maximum number of sectors from the start of a bio that may be |
| 163 | * submitted as a single request to a block device. If enough sectors remain, |
| 164 | * align the end to the physical block size. Otherwise align the end to the |
| 165 | * logical block size. This approach minimizes the number of non-aligned |
| 166 | * requests that are submitted to a block device if the start of a bio is not |
| 167 | * aligned to a physical block boundary. |
| 168 | */ |
| 169 | static inline unsigned get_max_io_size(struct bio *bio, |
| 170 | const struct queue_limits *lim) |
| 171 | { |
| 172 | unsigned pbs = lim->physical_block_size >> SECTOR_SHIFT; |
| 173 | unsigned lbs = lim->logical_block_size >> SECTOR_SHIFT; |
| 174 | unsigned max_sectors = lim->max_sectors, start, end; |
| 175 | |
| 176 | if (lim->chunk_sectors) { |
| 177 | max_sectors = min(max_sectors, |
| 178 | blk_chunk_sectors_left(bio->bi_iter.bi_sector, |
| 179 | lim->chunk_sectors)); |
| 180 | } |
| 181 | |
| 182 | start = bio->bi_iter.bi_sector & (pbs - 1); |
| 183 | end = (start + max_sectors) & ~(pbs - 1); |
| 184 | if (end > start) |
| 185 | return end - start; |
| 186 | return max_sectors & ~(lbs - 1); |
| 187 | } |
| 188 | |
| 189 | /** |
| 190 | * get_max_segment_size() - maximum number of bytes to add as a single segment |
| 191 | * @lim: Request queue limits. |
| 192 | * @start_page: See below. |
| 193 | * @offset: Offset from @start_page where to add a segment. |
| 194 | * |
| 195 | * Returns the maximum number of bytes that can be added as a single segment. |
| 196 | */ |
| 197 | static inline unsigned get_max_segment_size(const struct queue_limits *lim, |
| 198 | struct page *start_page, unsigned long offset) |
| 199 | { |
| 200 | unsigned long mask = lim->seg_boundary_mask; |
| 201 | |
| 202 | offset = mask & (page_to_phys(start_page) + offset); |
| 203 | |
| 204 | /* |
| 205 | * Prevent an overflow if mask = ULONG_MAX and offset = 0 by adding 1 |
| 206 | * after having calculated the minimum. |
| 207 | */ |
| 208 | return min(mask - offset, (unsigned long)lim->max_segment_size - 1) + 1; |
| 209 | } |
| 210 | |
| 211 | /** |
| 212 | * bvec_split_segs - verify whether or not a bvec should be split in the middle |
| 213 | * @lim: [in] queue limits to split based on |
| 214 | * @bv: [in] bvec to examine |
| 215 | * @nsegs: [in,out] Number of segments in the bio being built. Incremented |
| 216 | * by the number of segments from @bv that may be appended to that |
| 217 | * bio without exceeding @max_segs |
| 218 | * @bytes: [in,out] Number of bytes in the bio being built. Incremented |
| 219 | * by the number of bytes from @bv that may be appended to that |
| 220 | * bio without exceeding @max_bytes |
| 221 | * @max_segs: [in] upper bound for *@nsegs |
| 222 | * @max_bytes: [in] upper bound for *@bytes |
| 223 | * |
| 224 | * When splitting a bio, it can happen that a bvec is encountered that is too |
| 225 | * big to fit in a single segment and hence that it has to be split in the |
| 226 | * middle. This function verifies whether or not that should happen. The value |
| 227 | * %true is returned if and only if appending the entire @bv to a bio with |
| 228 | * *@nsegs segments and *@sectors sectors would make that bio unacceptable for |
| 229 | * the block driver. |
| 230 | */ |
| 231 | static bool bvec_split_segs(const struct queue_limits *lim, |
| 232 | const struct bio_vec *bv, unsigned *nsegs, unsigned *bytes, |
| 233 | unsigned max_segs, unsigned max_bytes) |
| 234 | { |
| 235 | unsigned max_len = min(max_bytes, UINT_MAX) - *bytes; |
| 236 | unsigned len = min(bv->bv_len, max_len); |
| 237 | unsigned total_len = 0; |
| 238 | unsigned seg_size = 0; |
| 239 | |
| 240 | while (len && *nsegs < max_segs) { |
| 241 | seg_size = get_max_segment_size(lim, bv->bv_page, |
| 242 | bv->bv_offset + total_len); |
| 243 | seg_size = min(seg_size, len); |
| 244 | |
| 245 | (*nsegs)++; |
| 246 | total_len += seg_size; |
| 247 | len -= seg_size; |
| 248 | |
| 249 | if ((bv->bv_offset + total_len) & lim->virt_boundary_mask) |
| 250 | break; |
| 251 | } |
| 252 | |
| 253 | *bytes += total_len; |
| 254 | |
| 255 | /* tell the caller to split the bvec if it is too big to fit */ |
| 256 | return len > 0 || bv->bv_len > max_len; |
| 257 | } |
| 258 | |
| 259 | /** |
| 260 | * bio_split_rw - split a bio in two bios |
| 261 | * @bio: [in] bio to be split |
| 262 | * @lim: [in] queue limits to split based on |
| 263 | * @segs: [out] number of segments in the bio with the first half of the sectors |
| 264 | * @bs: [in] bio set to allocate the clone from |
| 265 | * @max_bytes: [in] maximum number of bytes per bio |
| 266 | * |
| 267 | * Clone @bio, update the bi_iter of the clone to represent the first sectors |
| 268 | * of @bio and update @bio->bi_iter to represent the remaining sectors. The |
| 269 | * following is guaranteed for the cloned bio: |
| 270 | * - That it has at most @max_bytes worth of data |
| 271 | * - That it has at most queue_max_segments(@q) segments. |
| 272 | * |
| 273 | * Except for discard requests the cloned bio will point at the bi_io_vec of |
| 274 | * the original bio. It is the responsibility of the caller to ensure that the |
| 275 | * original bio is not freed before the cloned bio. The caller is also |
| 276 | * responsible for ensuring that @bs is only destroyed after processing of the |
| 277 | * split bio has finished. |
| 278 | */ |
| 279 | struct bio *bio_split_rw(struct bio *bio, const struct queue_limits *lim, |
| 280 | unsigned *segs, struct bio_set *bs, unsigned max_bytes) |
| 281 | { |
| 282 | struct bio_vec bv, bvprv, *bvprvp = NULL; |
| 283 | struct bvec_iter iter; |
| 284 | unsigned nsegs = 0, bytes = 0; |
| 285 | |
| 286 | bio_for_each_bvec(bv, bio, iter) { |
| 287 | /* |
| 288 | * If the queue doesn't support SG gaps and adding this |
| 289 | * offset would create a gap, disallow it. |
| 290 | */ |
| 291 | if (bvprvp && bvec_gap_to_prev(lim, bvprvp, bv.bv_offset)) |
| 292 | goto split; |
| 293 | |
| 294 | if (nsegs < lim->max_segments && |
| 295 | bytes + bv.bv_len <= max_bytes && |
| 296 | bv.bv_offset + bv.bv_len <= PAGE_SIZE) { |
| 297 | nsegs++; |
| 298 | bytes += bv.bv_len; |
| 299 | } else { |
| 300 | if (bvec_split_segs(lim, &bv, &nsegs, &bytes, |
| 301 | lim->max_segments, max_bytes)) |
| 302 | goto split; |
| 303 | } |
| 304 | |
| 305 | bvprv = bv; |
| 306 | bvprvp = &bvprv; |
| 307 | } |
| 308 | |
| 309 | *segs = nsegs; |
| 310 | return NULL; |
| 311 | split: |
| 312 | /* |
| 313 | * We can't sanely support splitting for a REQ_NOWAIT bio. End it |
| 314 | * with EAGAIN if splitting is required and return an error pointer. |
| 315 | */ |
| 316 | if (bio->bi_opf & REQ_NOWAIT) { |
| 317 | bio->bi_status = BLK_STS_AGAIN; |
| 318 | bio_endio(bio); |
| 319 | return ERR_PTR(-EAGAIN); |
| 320 | } |
| 321 | |
| 322 | *segs = nsegs; |
| 323 | |
| 324 | /* |
| 325 | * Individual bvecs might not be logical block aligned. Round down the |
| 326 | * split size so that each bio is properly block size aligned, even if |
| 327 | * we do not use the full hardware limits. |
| 328 | */ |
| 329 | bytes = ALIGN_DOWN(bytes, lim->logical_block_size); |
| 330 | |
| 331 | /* |
| 332 | * Bio splitting may cause subtle trouble such as hang when doing sync |
| 333 | * iopoll in direct IO routine. Given performance gain of iopoll for |
| 334 | * big IO can be trival, disable iopoll when split needed. |
| 335 | */ |
| 336 | bio_clear_polled(bio); |
| 337 | return bio_split(bio, bytes >> SECTOR_SHIFT, GFP_NOIO, bs); |
| 338 | } |
| 339 | EXPORT_SYMBOL_GPL(bio_split_rw); |
| 340 | |
| 341 | /** |
| 342 | * __bio_split_to_limits - split a bio to fit the queue limits |
| 343 | * @bio: bio to be split |
| 344 | * @lim: queue limits to split based on |
| 345 | * @nr_segs: returns the number of segments in the returned bio |
| 346 | * |
| 347 | * Check if @bio needs splitting based on the queue limits, and if so split off |
| 348 | * a bio fitting the limits from the beginning of @bio and return it. @bio is |
| 349 | * shortened to the remainder and re-submitted. |
| 350 | * |
| 351 | * The split bio is allocated from @q->bio_split, which is provided by the |
| 352 | * block layer. |
| 353 | */ |
| 354 | struct bio *__bio_split_to_limits(struct bio *bio, |
| 355 | const struct queue_limits *lim, |
| 356 | unsigned int *nr_segs) |
| 357 | { |
| 358 | struct bio_set *bs = &bio->bi_bdev->bd_disk->bio_split; |
| 359 | struct bio *split; |
| 360 | |
| 361 | switch (bio_op(bio)) { |
| 362 | case REQ_OP_DISCARD: |
| 363 | case REQ_OP_SECURE_ERASE: |
| 364 | split = bio_split_discard(bio, lim, nr_segs, bs); |
| 365 | break; |
| 366 | case REQ_OP_WRITE_ZEROES: |
| 367 | split = bio_split_write_zeroes(bio, lim, nr_segs, bs); |
| 368 | break; |
| 369 | default: |
| 370 | split = bio_split_rw(bio, lim, nr_segs, bs, |
| 371 | get_max_io_size(bio, lim) << SECTOR_SHIFT); |
| 372 | if (IS_ERR(split)) |
| 373 | return NULL; |
| 374 | break; |
| 375 | } |
| 376 | |
| 377 | if (split) { |
| 378 | /* there isn't chance to merge the split bio */ |
| 379 | split->bi_opf |= REQ_NOMERGE; |
| 380 | |
| 381 | blkcg_bio_issue_init(split); |
| 382 | bio_chain(split, bio); |
| 383 | trace_block_split(split, bio->bi_iter.bi_sector); |
| 384 | submit_bio_noacct(bio); |
| 385 | return split; |
| 386 | } |
| 387 | return bio; |
| 388 | } |
| 389 | |
| 390 | /** |
| 391 | * bio_split_to_limits - split a bio to fit the queue limits |
| 392 | * @bio: bio to be split |
| 393 | * |
| 394 | * Check if @bio needs splitting based on the queue limits of @bio->bi_bdev, and |
| 395 | * if so split off a bio fitting the limits from the beginning of @bio and |
| 396 | * return it. @bio is shortened to the remainder and re-submitted. |
| 397 | * |
| 398 | * The split bio is allocated from @q->bio_split, which is provided by the |
| 399 | * block layer. |
| 400 | */ |
| 401 | struct bio *bio_split_to_limits(struct bio *bio) |
| 402 | { |
| 403 | const struct queue_limits *lim = &bdev_get_queue(bio->bi_bdev)->limits; |
| 404 | unsigned int nr_segs; |
| 405 | |
| 406 | if (bio_may_exceed_limits(bio, lim)) |
| 407 | return __bio_split_to_limits(bio, lim, &nr_segs); |
| 408 | return bio; |
| 409 | } |
| 410 | EXPORT_SYMBOL(bio_split_to_limits); |
| 411 | |
| 412 | unsigned int blk_recalc_rq_segments(struct request *rq) |
| 413 | { |
| 414 | unsigned int nr_phys_segs = 0; |
| 415 | unsigned int bytes = 0; |
| 416 | struct req_iterator iter; |
| 417 | struct bio_vec bv; |
| 418 | |
| 419 | if (!rq->bio) |
| 420 | return 0; |
| 421 | |
| 422 | switch (bio_op(rq->bio)) { |
| 423 | case REQ_OP_DISCARD: |
| 424 | case REQ_OP_SECURE_ERASE: |
| 425 | if (queue_max_discard_segments(rq->q) > 1) { |
| 426 | struct bio *bio = rq->bio; |
| 427 | |
| 428 | for_each_bio(bio) |
| 429 | nr_phys_segs++; |
| 430 | return nr_phys_segs; |
| 431 | } |
| 432 | return 1; |
| 433 | case REQ_OP_WRITE_ZEROES: |
| 434 | return 0; |
| 435 | default: |
| 436 | break; |
| 437 | } |
| 438 | |
| 439 | rq_for_each_bvec(bv, rq, iter) |
| 440 | bvec_split_segs(&rq->q->limits, &bv, &nr_phys_segs, &bytes, |
| 441 | UINT_MAX, UINT_MAX); |
| 442 | return nr_phys_segs; |
| 443 | } |
| 444 | |
| 445 | static inline struct scatterlist *blk_next_sg(struct scatterlist **sg, |
| 446 | struct scatterlist *sglist) |
| 447 | { |
| 448 | if (!*sg) |
| 449 | return sglist; |
| 450 | |
| 451 | /* |
| 452 | * If the driver previously mapped a shorter list, we could see a |
| 453 | * termination bit prematurely unless it fully inits the sg table |
| 454 | * on each mapping. We KNOW that there must be more entries here |
| 455 | * or the driver would be buggy, so force clear the termination bit |
| 456 | * to avoid doing a full sg_init_table() in drivers for each command. |
| 457 | */ |
| 458 | sg_unmark_end(*sg); |
| 459 | return sg_next(*sg); |
| 460 | } |
| 461 | |
| 462 | static unsigned blk_bvec_map_sg(struct request_queue *q, |
| 463 | struct bio_vec *bvec, struct scatterlist *sglist, |
| 464 | struct scatterlist **sg) |
| 465 | { |
| 466 | unsigned nbytes = bvec->bv_len; |
| 467 | unsigned nsegs = 0, total = 0; |
| 468 | |
| 469 | while (nbytes > 0) { |
| 470 | unsigned offset = bvec->bv_offset + total; |
| 471 | unsigned len = min(get_max_segment_size(&q->limits, |
| 472 | bvec->bv_page, offset), nbytes); |
| 473 | struct page *page = bvec->bv_page; |
| 474 | |
| 475 | /* |
| 476 | * Unfortunately a fair number of drivers barf on scatterlists |
| 477 | * that have an offset larger than PAGE_SIZE, despite other |
| 478 | * subsystems dealing with that invariant just fine. For now |
| 479 | * stick to the legacy format where we never present those from |
| 480 | * the block layer, but the code below should be removed once |
| 481 | * these offenders (mostly MMC/SD drivers) are fixed. |
| 482 | */ |
| 483 | page += (offset >> PAGE_SHIFT); |
| 484 | offset &= ~PAGE_MASK; |
| 485 | |
| 486 | *sg = blk_next_sg(sg, sglist); |
| 487 | sg_set_page(*sg, page, len, offset); |
| 488 | |
| 489 | total += len; |
| 490 | nbytes -= len; |
| 491 | nsegs++; |
| 492 | } |
| 493 | |
| 494 | return nsegs; |
| 495 | } |
| 496 | |
| 497 | static inline int __blk_bvec_map_sg(struct bio_vec bv, |
| 498 | struct scatterlist *sglist, struct scatterlist **sg) |
| 499 | { |
| 500 | *sg = blk_next_sg(sg, sglist); |
| 501 | sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset); |
| 502 | return 1; |
| 503 | } |
| 504 | |
| 505 | /* only try to merge bvecs into one sg if they are from two bios */ |
| 506 | static inline bool |
| 507 | __blk_segment_map_sg_merge(struct request_queue *q, struct bio_vec *bvec, |
| 508 | struct bio_vec *bvprv, struct scatterlist **sg) |
| 509 | { |
| 510 | |
| 511 | int nbytes = bvec->bv_len; |
| 512 | |
| 513 | if (!*sg) |
| 514 | return false; |
| 515 | |
| 516 | if ((*sg)->length + nbytes > queue_max_segment_size(q)) |
| 517 | return false; |
| 518 | |
| 519 | if (!biovec_phys_mergeable(q, bvprv, bvec)) |
| 520 | return false; |
| 521 | |
| 522 | (*sg)->length += nbytes; |
| 523 | |
| 524 | return true; |
| 525 | } |
| 526 | |
| 527 | static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, |
| 528 | struct scatterlist *sglist, |
| 529 | struct scatterlist **sg) |
| 530 | { |
| 531 | struct bio_vec bvec, bvprv = { NULL }; |
| 532 | struct bvec_iter iter; |
| 533 | int nsegs = 0; |
| 534 | bool new_bio = false; |
| 535 | |
| 536 | for_each_bio(bio) { |
| 537 | bio_for_each_bvec(bvec, bio, iter) { |
| 538 | /* |
| 539 | * Only try to merge bvecs from two bios given we |
| 540 | * have done bio internal merge when adding pages |
| 541 | * to bio |
| 542 | */ |
| 543 | if (new_bio && |
| 544 | __blk_segment_map_sg_merge(q, &bvec, &bvprv, sg)) |
| 545 | goto next_bvec; |
| 546 | |
| 547 | if (bvec.bv_offset + bvec.bv_len <= PAGE_SIZE) |
| 548 | nsegs += __blk_bvec_map_sg(bvec, sglist, sg); |
| 549 | else |
| 550 | nsegs += blk_bvec_map_sg(q, &bvec, sglist, sg); |
| 551 | next_bvec: |
| 552 | new_bio = false; |
| 553 | } |
| 554 | if (likely(bio->bi_iter.bi_size)) { |
| 555 | bvprv = bvec; |
| 556 | new_bio = true; |
| 557 | } |
| 558 | } |
| 559 | |
| 560 | return nsegs; |
| 561 | } |
| 562 | |
| 563 | /* |
| 564 | * map a request to scatterlist, return number of sg entries setup. Caller |
| 565 | * must make sure sg can hold rq->nr_phys_segments entries |
| 566 | */ |
| 567 | int __blk_rq_map_sg(struct request_queue *q, struct request *rq, |
| 568 | struct scatterlist *sglist, struct scatterlist **last_sg) |
| 569 | { |
| 570 | int nsegs = 0; |
| 571 | |
| 572 | if (rq->rq_flags & RQF_SPECIAL_PAYLOAD) |
| 573 | nsegs = __blk_bvec_map_sg(rq->special_vec, sglist, last_sg); |
| 574 | else if (rq->bio) |
| 575 | nsegs = __blk_bios_map_sg(q, rq->bio, sglist, last_sg); |
| 576 | |
| 577 | if (*last_sg) |
| 578 | sg_mark_end(*last_sg); |
| 579 | |
| 580 | /* |
| 581 | * Something must have been wrong if the figured number of |
| 582 | * segment is bigger than number of req's physical segments |
| 583 | */ |
| 584 | WARN_ON(nsegs > blk_rq_nr_phys_segments(rq)); |
| 585 | |
| 586 | return nsegs; |
| 587 | } |
| 588 | EXPORT_SYMBOL(__blk_rq_map_sg); |
| 589 | |
| 590 | static inline unsigned int blk_rq_get_max_segments(struct request *rq) |
| 591 | { |
| 592 | if (req_op(rq) == REQ_OP_DISCARD) |
| 593 | return queue_max_discard_segments(rq->q); |
| 594 | return queue_max_segments(rq->q); |
| 595 | } |
| 596 | |
| 597 | static inline unsigned int blk_rq_get_max_sectors(struct request *rq, |
| 598 | sector_t offset) |
| 599 | { |
| 600 | struct request_queue *q = rq->q; |
| 601 | unsigned int max_sectors; |
| 602 | |
| 603 | if (blk_rq_is_passthrough(rq)) |
| 604 | return q->limits.max_hw_sectors; |
| 605 | |
| 606 | max_sectors = blk_queue_get_max_sectors(q, req_op(rq)); |
| 607 | if (!q->limits.chunk_sectors || |
| 608 | req_op(rq) == REQ_OP_DISCARD || |
| 609 | req_op(rq) == REQ_OP_SECURE_ERASE) |
| 610 | return max_sectors; |
| 611 | return min(max_sectors, |
| 612 | blk_chunk_sectors_left(offset, q->limits.chunk_sectors)); |
| 613 | } |
| 614 | |
| 615 | static inline int ll_new_hw_segment(struct request *req, struct bio *bio, |
| 616 | unsigned int nr_phys_segs) |
| 617 | { |
| 618 | if (!blk_cgroup_mergeable(req, bio)) |
| 619 | goto no_merge; |
| 620 | |
| 621 | if (blk_integrity_merge_bio(req->q, req, bio) == false) |
| 622 | goto no_merge; |
| 623 | |
| 624 | /* discard request merge won't add new segment */ |
| 625 | if (req_op(req) == REQ_OP_DISCARD) |
| 626 | return 1; |
| 627 | |
| 628 | if (req->nr_phys_segments + nr_phys_segs > blk_rq_get_max_segments(req)) |
| 629 | goto no_merge; |
| 630 | |
| 631 | /* |
| 632 | * This will form the start of a new hw segment. Bump both |
| 633 | * counters. |
| 634 | */ |
| 635 | req->nr_phys_segments += nr_phys_segs; |
| 636 | return 1; |
| 637 | |
| 638 | no_merge: |
| 639 | req_set_nomerge(req->q, req); |
| 640 | return 0; |
| 641 | } |
| 642 | |
| 643 | int ll_back_merge_fn(struct request *req, struct bio *bio, unsigned int nr_segs) |
| 644 | { |
| 645 | if (req_gap_back_merge(req, bio)) |
| 646 | return 0; |
| 647 | if (blk_integrity_rq(req) && |
| 648 | integrity_req_gap_back_merge(req, bio)) |
| 649 | return 0; |
| 650 | if (!bio_crypt_ctx_back_mergeable(req, bio)) |
| 651 | return 0; |
| 652 | if (blk_rq_sectors(req) + bio_sectors(bio) > |
| 653 | blk_rq_get_max_sectors(req, blk_rq_pos(req))) { |
| 654 | req_set_nomerge(req->q, req); |
| 655 | return 0; |
| 656 | } |
| 657 | |
| 658 | return ll_new_hw_segment(req, bio, nr_segs); |
| 659 | } |
| 660 | |
| 661 | static int ll_front_merge_fn(struct request *req, struct bio *bio, |
| 662 | unsigned int nr_segs) |
| 663 | { |
| 664 | if (req_gap_front_merge(req, bio)) |
| 665 | return 0; |
| 666 | if (blk_integrity_rq(req) && |
| 667 | integrity_req_gap_front_merge(req, bio)) |
| 668 | return 0; |
| 669 | if (!bio_crypt_ctx_front_mergeable(req, bio)) |
| 670 | return 0; |
| 671 | if (blk_rq_sectors(req) + bio_sectors(bio) > |
| 672 | blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) { |
| 673 | req_set_nomerge(req->q, req); |
| 674 | return 0; |
| 675 | } |
| 676 | |
| 677 | return ll_new_hw_segment(req, bio, nr_segs); |
| 678 | } |
| 679 | |
| 680 | static bool req_attempt_discard_merge(struct request_queue *q, struct request *req, |
| 681 | struct request *next) |
| 682 | { |
| 683 | unsigned short segments = blk_rq_nr_discard_segments(req); |
| 684 | |
| 685 | if (segments >= queue_max_discard_segments(q)) |
| 686 | goto no_merge; |
| 687 | if (blk_rq_sectors(req) + bio_sectors(next->bio) > |
| 688 | blk_rq_get_max_sectors(req, blk_rq_pos(req))) |
| 689 | goto no_merge; |
| 690 | |
| 691 | req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next); |
| 692 | return true; |
| 693 | no_merge: |
| 694 | req_set_nomerge(q, req); |
| 695 | return false; |
| 696 | } |
| 697 | |
| 698 | static int ll_merge_requests_fn(struct request_queue *q, struct request *req, |
| 699 | struct request *next) |
| 700 | { |
| 701 | int total_phys_segments; |
| 702 | |
| 703 | if (req_gap_back_merge(req, next->bio)) |
| 704 | return 0; |
| 705 | |
| 706 | /* |
| 707 | * Will it become too large? |
| 708 | */ |
| 709 | if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > |
| 710 | blk_rq_get_max_sectors(req, blk_rq_pos(req))) |
| 711 | return 0; |
| 712 | |
| 713 | total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; |
| 714 | if (total_phys_segments > blk_rq_get_max_segments(req)) |
| 715 | return 0; |
| 716 | |
| 717 | if (!blk_cgroup_mergeable(req, next->bio)) |
| 718 | return 0; |
| 719 | |
| 720 | if (blk_integrity_merge_rq(q, req, next) == false) |
| 721 | return 0; |
| 722 | |
| 723 | if (!bio_crypt_ctx_merge_rq(req, next)) |
| 724 | return 0; |
| 725 | |
| 726 | /* Merge is OK... */ |
| 727 | req->nr_phys_segments = total_phys_segments; |
| 728 | return 1; |
| 729 | } |
| 730 | |
| 731 | /** |
| 732 | * blk_rq_set_mixed_merge - mark a request as mixed merge |
| 733 | * @rq: request to mark as mixed merge |
| 734 | * |
| 735 | * Description: |
| 736 | * @rq is about to be mixed merged. Make sure the attributes |
| 737 | * which can be mixed are set in each bio and mark @rq as mixed |
| 738 | * merged. |
| 739 | */ |
| 740 | void blk_rq_set_mixed_merge(struct request *rq) |
| 741 | { |
| 742 | blk_opf_t ff = rq->cmd_flags & REQ_FAILFAST_MASK; |
| 743 | struct bio *bio; |
| 744 | |
| 745 | if (rq->rq_flags & RQF_MIXED_MERGE) |
| 746 | return; |
| 747 | |
| 748 | /* |
| 749 | * @rq will no longer represent mixable attributes for all the |
| 750 | * contained bios. It will just track those of the first one. |
| 751 | * Distributes the attributs to each bio. |
| 752 | */ |
| 753 | for (bio = rq->bio; bio; bio = bio->bi_next) { |
| 754 | WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) && |
| 755 | (bio->bi_opf & REQ_FAILFAST_MASK) != ff); |
| 756 | bio->bi_opf |= ff; |
| 757 | } |
| 758 | rq->rq_flags |= RQF_MIXED_MERGE; |
| 759 | } |
| 760 | |
| 761 | static inline blk_opf_t bio_failfast(const struct bio *bio) |
| 762 | { |
| 763 | if (bio->bi_opf & REQ_RAHEAD) |
| 764 | return REQ_FAILFAST_MASK; |
| 765 | |
| 766 | return bio->bi_opf & REQ_FAILFAST_MASK; |
| 767 | } |
| 768 | |
| 769 | /* |
| 770 | * After we are marked as MIXED_MERGE, any new RA bio has to be updated |
| 771 | * as failfast, and request's failfast has to be updated in case of |
| 772 | * front merge. |
| 773 | */ |
| 774 | static inline void blk_update_mixed_merge(struct request *req, |
| 775 | struct bio *bio, bool front_merge) |
| 776 | { |
| 777 | if (req->rq_flags & RQF_MIXED_MERGE) { |
| 778 | if (bio->bi_opf & REQ_RAHEAD) |
| 779 | bio->bi_opf |= REQ_FAILFAST_MASK; |
| 780 | |
| 781 | if (front_merge) { |
| 782 | req->cmd_flags &= ~REQ_FAILFAST_MASK; |
| 783 | req->cmd_flags |= bio->bi_opf & REQ_FAILFAST_MASK; |
| 784 | } |
| 785 | } |
| 786 | } |
| 787 | |
| 788 | static void blk_account_io_merge_request(struct request *req) |
| 789 | { |
| 790 | if (blk_do_io_stat(req)) { |
| 791 | part_stat_lock(); |
| 792 | part_stat_inc(req->part, merges[op_stat_group(req_op(req))]); |
| 793 | part_stat_unlock(); |
| 794 | } |
| 795 | } |
| 796 | |
| 797 | static enum elv_merge blk_try_req_merge(struct request *req, |
| 798 | struct request *next) |
| 799 | { |
| 800 | if (blk_discard_mergable(req)) |
| 801 | return ELEVATOR_DISCARD_MERGE; |
| 802 | else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next)) |
| 803 | return ELEVATOR_BACK_MERGE; |
| 804 | |
| 805 | return ELEVATOR_NO_MERGE; |
| 806 | } |
| 807 | |
| 808 | /* |
| 809 | * For non-mq, this has to be called with the request spinlock acquired. |
| 810 | * For mq with scheduling, the appropriate queue wide lock should be held. |
| 811 | */ |
| 812 | static struct request *attempt_merge(struct request_queue *q, |
| 813 | struct request *req, struct request *next) |
| 814 | { |
| 815 | if (!rq_mergeable(req) || !rq_mergeable(next)) |
| 816 | return NULL; |
| 817 | |
| 818 | if (req_op(req) != req_op(next)) |
| 819 | return NULL; |
| 820 | |
| 821 | if (rq_data_dir(req) != rq_data_dir(next)) |
| 822 | return NULL; |
| 823 | |
| 824 | if (req->ioprio != next->ioprio) |
| 825 | return NULL; |
| 826 | |
| 827 | /* |
| 828 | * If we are allowed to merge, then append bio list |
| 829 | * from next to rq and release next. merge_requests_fn |
| 830 | * will have updated segment counts, update sector |
| 831 | * counts here. Handle DISCARDs separately, as they |
| 832 | * have separate settings. |
| 833 | */ |
| 834 | |
| 835 | switch (blk_try_req_merge(req, next)) { |
| 836 | case ELEVATOR_DISCARD_MERGE: |
| 837 | if (!req_attempt_discard_merge(q, req, next)) |
| 838 | return NULL; |
| 839 | break; |
| 840 | case ELEVATOR_BACK_MERGE: |
| 841 | if (!ll_merge_requests_fn(q, req, next)) |
| 842 | return NULL; |
| 843 | break; |
| 844 | default: |
| 845 | return NULL; |
| 846 | } |
| 847 | |
| 848 | /* |
| 849 | * If failfast settings disagree or any of the two is already |
| 850 | * a mixed merge, mark both as mixed before proceeding. This |
| 851 | * makes sure that all involved bios have mixable attributes |
| 852 | * set properly. |
| 853 | */ |
| 854 | if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) || |
| 855 | (req->cmd_flags & REQ_FAILFAST_MASK) != |
| 856 | (next->cmd_flags & REQ_FAILFAST_MASK)) { |
| 857 | blk_rq_set_mixed_merge(req); |
| 858 | blk_rq_set_mixed_merge(next); |
| 859 | } |
| 860 | |
| 861 | /* |
| 862 | * At this point we have either done a back merge or front merge. We |
| 863 | * need the smaller start_time_ns of the merged requests to be the |
| 864 | * current request for accounting purposes. |
| 865 | */ |
| 866 | if (next->start_time_ns < req->start_time_ns) |
| 867 | req->start_time_ns = next->start_time_ns; |
| 868 | |
| 869 | req->biotail->bi_next = next->bio; |
| 870 | req->biotail = next->biotail; |
| 871 | |
| 872 | req->__data_len += blk_rq_bytes(next); |
| 873 | |
| 874 | if (!blk_discard_mergable(req)) |
| 875 | elv_merge_requests(q, req, next); |
| 876 | |
| 877 | /* |
| 878 | * 'next' is going away, so update stats accordingly |
| 879 | */ |
| 880 | blk_account_io_merge_request(next); |
| 881 | |
| 882 | trace_block_rq_merge(next); |
| 883 | |
| 884 | /* |
| 885 | * ownership of bio passed from next to req, return 'next' for |
| 886 | * the caller to free |
| 887 | */ |
| 888 | next->bio = NULL; |
| 889 | return next; |
| 890 | } |
| 891 | |
| 892 | static struct request *attempt_back_merge(struct request_queue *q, |
| 893 | struct request *rq) |
| 894 | { |
| 895 | struct request *next = elv_latter_request(q, rq); |
| 896 | |
| 897 | if (next) |
| 898 | return attempt_merge(q, rq, next); |
| 899 | |
| 900 | return NULL; |
| 901 | } |
| 902 | |
| 903 | static struct request *attempt_front_merge(struct request_queue *q, |
| 904 | struct request *rq) |
| 905 | { |
| 906 | struct request *prev = elv_former_request(q, rq); |
| 907 | |
| 908 | if (prev) |
| 909 | return attempt_merge(q, prev, rq); |
| 910 | |
| 911 | return NULL; |
| 912 | } |
| 913 | |
| 914 | /* |
| 915 | * Try to merge 'next' into 'rq'. Return true if the merge happened, false |
| 916 | * otherwise. The caller is responsible for freeing 'next' if the merge |
| 917 | * happened. |
| 918 | */ |
| 919 | bool blk_attempt_req_merge(struct request_queue *q, struct request *rq, |
| 920 | struct request *next) |
| 921 | { |
| 922 | return attempt_merge(q, rq, next); |
| 923 | } |
| 924 | |
| 925 | bool blk_rq_merge_ok(struct request *rq, struct bio *bio) |
| 926 | { |
| 927 | if (!rq_mergeable(rq) || !bio_mergeable(bio)) |
| 928 | return false; |
| 929 | |
| 930 | if (req_op(rq) != bio_op(bio)) |
| 931 | return false; |
| 932 | |
| 933 | /* different data direction or already started, don't merge */ |
| 934 | if (bio_data_dir(bio) != rq_data_dir(rq)) |
| 935 | return false; |
| 936 | |
| 937 | /* don't merge across cgroup boundaries */ |
| 938 | if (!blk_cgroup_mergeable(rq, bio)) |
| 939 | return false; |
| 940 | |
| 941 | /* only merge integrity protected bio into ditto rq */ |
| 942 | if (blk_integrity_merge_bio(rq->q, rq, bio) == false) |
| 943 | return false; |
| 944 | |
| 945 | /* Only merge if the crypt contexts are compatible */ |
| 946 | if (!bio_crypt_rq_ctx_compatible(rq, bio)) |
| 947 | return false; |
| 948 | |
| 949 | if (rq->ioprio != bio_prio(bio)) |
| 950 | return false; |
| 951 | |
| 952 | return true; |
| 953 | } |
| 954 | |
| 955 | enum elv_merge blk_try_merge(struct request *rq, struct bio *bio) |
| 956 | { |
| 957 | if (blk_discard_mergable(rq)) |
| 958 | return ELEVATOR_DISCARD_MERGE; |
| 959 | else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) |
| 960 | return ELEVATOR_BACK_MERGE; |
| 961 | else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) |
| 962 | return ELEVATOR_FRONT_MERGE; |
| 963 | return ELEVATOR_NO_MERGE; |
| 964 | } |
| 965 | |
| 966 | static void blk_account_io_merge_bio(struct request *req) |
| 967 | { |
| 968 | if (!blk_do_io_stat(req)) |
| 969 | return; |
| 970 | |
| 971 | part_stat_lock(); |
| 972 | part_stat_inc(req->part, merges[op_stat_group(req_op(req))]); |
| 973 | part_stat_unlock(); |
| 974 | } |
| 975 | |
| 976 | enum bio_merge_status { |
| 977 | BIO_MERGE_OK, |
| 978 | BIO_MERGE_NONE, |
| 979 | BIO_MERGE_FAILED, |
| 980 | }; |
| 981 | |
| 982 | static enum bio_merge_status bio_attempt_back_merge(struct request *req, |
| 983 | struct bio *bio, unsigned int nr_segs) |
| 984 | { |
| 985 | const blk_opf_t ff = bio_failfast(bio); |
| 986 | |
| 987 | if (!ll_back_merge_fn(req, bio, nr_segs)) |
| 988 | return BIO_MERGE_FAILED; |
| 989 | |
| 990 | trace_block_bio_backmerge(bio); |
| 991 | rq_qos_merge(req->q, req, bio); |
| 992 | |
| 993 | if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) |
| 994 | blk_rq_set_mixed_merge(req); |
| 995 | |
| 996 | blk_update_mixed_merge(req, bio, false); |
| 997 | |
| 998 | req->biotail->bi_next = bio; |
| 999 | req->biotail = bio; |
| 1000 | req->__data_len += bio->bi_iter.bi_size; |
| 1001 | |
| 1002 | bio_crypt_free_ctx(bio); |
| 1003 | |
| 1004 | blk_account_io_merge_bio(req); |
| 1005 | return BIO_MERGE_OK; |
| 1006 | } |
| 1007 | |
| 1008 | static enum bio_merge_status bio_attempt_front_merge(struct request *req, |
| 1009 | struct bio *bio, unsigned int nr_segs) |
| 1010 | { |
| 1011 | const blk_opf_t ff = bio_failfast(bio); |
| 1012 | |
| 1013 | if (!ll_front_merge_fn(req, bio, nr_segs)) |
| 1014 | return BIO_MERGE_FAILED; |
| 1015 | |
| 1016 | trace_block_bio_frontmerge(bio); |
| 1017 | rq_qos_merge(req->q, req, bio); |
| 1018 | |
| 1019 | if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) |
| 1020 | blk_rq_set_mixed_merge(req); |
| 1021 | |
| 1022 | blk_update_mixed_merge(req, bio, true); |
| 1023 | |
| 1024 | bio->bi_next = req->bio; |
| 1025 | req->bio = bio; |
| 1026 | |
| 1027 | req->__sector = bio->bi_iter.bi_sector; |
| 1028 | req->__data_len += bio->bi_iter.bi_size; |
| 1029 | |
| 1030 | bio_crypt_do_front_merge(req, bio); |
| 1031 | |
| 1032 | blk_account_io_merge_bio(req); |
| 1033 | return BIO_MERGE_OK; |
| 1034 | } |
| 1035 | |
| 1036 | static enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q, |
| 1037 | struct request *req, struct bio *bio) |
| 1038 | { |
| 1039 | unsigned short segments = blk_rq_nr_discard_segments(req); |
| 1040 | |
| 1041 | if (segments >= queue_max_discard_segments(q)) |
| 1042 | goto no_merge; |
| 1043 | if (blk_rq_sectors(req) + bio_sectors(bio) > |
| 1044 | blk_rq_get_max_sectors(req, blk_rq_pos(req))) |
| 1045 | goto no_merge; |
| 1046 | |
| 1047 | rq_qos_merge(q, req, bio); |
| 1048 | |
| 1049 | req->biotail->bi_next = bio; |
| 1050 | req->biotail = bio; |
| 1051 | req->__data_len += bio->bi_iter.bi_size; |
| 1052 | req->nr_phys_segments = segments + 1; |
| 1053 | |
| 1054 | blk_account_io_merge_bio(req); |
| 1055 | return BIO_MERGE_OK; |
| 1056 | no_merge: |
| 1057 | req_set_nomerge(q, req); |
| 1058 | return BIO_MERGE_FAILED; |
| 1059 | } |
| 1060 | |
| 1061 | static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q, |
| 1062 | struct request *rq, |
| 1063 | struct bio *bio, |
| 1064 | unsigned int nr_segs, |
| 1065 | bool sched_allow_merge) |
| 1066 | { |
| 1067 | if (!blk_rq_merge_ok(rq, bio)) |
| 1068 | return BIO_MERGE_NONE; |
| 1069 | |
| 1070 | switch (blk_try_merge(rq, bio)) { |
| 1071 | case ELEVATOR_BACK_MERGE: |
| 1072 | if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio)) |
| 1073 | return bio_attempt_back_merge(rq, bio, nr_segs); |
| 1074 | break; |
| 1075 | case ELEVATOR_FRONT_MERGE: |
| 1076 | if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio)) |
| 1077 | return bio_attempt_front_merge(rq, bio, nr_segs); |
| 1078 | break; |
| 1079 | case ELEVATOR_DISCARD_MERGE: |
| 1080 | return bio_attempt_discard_merge(q, rq, bio); |
| 1081 | default: |
| 1082 | return BIO_MERGE_NONE; |
| 1083 | } |
| 1084 | |
| 1085 | return BIO_MERGE_FAILED; |
| 1086 | } |
| 1087 | |
| 1088 | /** |
| 1089 | * blk_attempt_plug_merge - try to merge with %current's plugged list |
| 1090 | * @q: request_queue new bio is being queued at |
| 1091 | * @bio: new bio being queued |
| 1092 | * @nr_segs: number of segments in @bio |
| 1093 | * from the passed in @q already in the plug list |
| 1094 | * |
| 1095 | * Determine whether @bio being queued on @q can be merged with the previous |
| 1096 | * request on %current's plugged list. Returns %true if merge was successful, |
| 1097 | * otherwise %false. |
| 1098 | * |
| 1099 | * Plugging coalesces IOs from the same issuer for the same purpose without |
| 1100 | * going through @q->queue_lock. As such it's more of an issuing mechanism |
| 1101 | * than scheduling, and the request, while may have elvpriv data, is not |
| 1102 | * added on the elevator at this point. In addition, we don't have |
| 1103 | * reliable access to the elevator outside queue lock. Only check basic |
| 1104 | * merging parameters without querying the elevator. |
| 1105 | * |
| 1106 | * Caller must ensure !blk_queue_nomerges(q) beforehand. |
| 1107 | */ |
| 1108 | bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio, |
| 1109 | unsigned int nr_segs) |
| 1110 | { |
| 1111 | struct blk_plug *plug; |
| 1112 | struct request *rq; |
| 1113 | |
| 1114 | plug = blk_mq_plug(bio); |
| 1115 | if (!plug || rq_list_empty(plug->mq_list)) |
| 1116 | return false; |
| 1117 | |
| 1118 | rq_list_for_each(&plug->mq_list, rq) { |
| 1119 | if (rq->q == q) { |
| 1120 | if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) == |
| 1121 | BIO_MERGE_OK) |
| 1122 | return true; |
| 1123 | break; |
| 1124 | } |
| 1125 | |
| 1126 | /* |
| 1127 | * Only keep iterating plug list for merges if we have multiple |
| 1128 | * queues |
| 1129 | */ |
| 1130 | if (!plug->multiple_queues) |
| 1131 | break; |
| 1132 | } |
| 1133 | return false; |
| 1134 | } |
| 1135 | |
| 1136 | /* |
| 1137 | * Iterate list of requests and see if we can merge this bio with any |
| 1138 | * of them. |
| 1139 | */ |
| 1140 | bool blk_bio_list_merge(struct request_queue *q, struct list_head *list, |
| 1141 | struct bio *bio, unsigned int nr_segs) |
| 1142 | { |
| 1143 | struct request *rq; |
| 1144 | int checked = 8; |
| 1145 | |
| 1146 | list_for_each_entry_reverse(rq, list, queuelist) { |
| 1147 | if (!checked--) |
| 1148 | break; |
| 1149 | |
| 1150 | switch (blk_attempt_bio_merge(q, rq, bio, nr_segs, true)) { |
| 1151 | case BIO_MERGE_NONE: |
| 1152 | continue; |
| 1153 | case BIO_MERGE_OK: |
| 1154 | return true; |
| 1155 | case BIO_MERGE_FAILED: |
| 1156 | return false; |
| 1157 | } |
| 1158 | |
| 1159 | } |
| 1160 | |
| 1161 | return false; |
| 1162 | } |
| 1163 | EXPORT_SYMBOL_GPL(blk_bio_list_merge); |
| 1164 | |
| 1165 | bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio, |
| 1166 | unsigned int nr_segs, struct request **merged_request) |
| 1167 | { |
| 1168 | struct request *rq; |
| 1169 | |
| 1170 | switch (elv_merge(q, &rq, bio)) { |
| 1171 | case ELEVATOR_BACK_MERGE: |
| 1172 | if (!blk_mq_sched_allow_merge(q, rq, bio)) |
| 1173 | return false; |
| 1174 | if (bio_attempt_back_merge(rq, bio, nr_segs) != BIO_MERGE_OK) |
| 1175 | return false; |
| 1176 | *merged_request = attempt_back_merge(q, rq); |
| 1177 | if (!*merged_request) |
| 1178 | elv_merged_request(q, rq, ELEVATOR_BACK_MERGE); |
| 1179 | return true; |
| 1180 | case ELEVATOR_FRONT_MERGE: |
| 1181 | if (!blk_mq_sched_allow_merge(q, rq, bio)) |
| 1182 | return false; |
| 1183 | if (bio_attempt_front_merge(rq, bio, nr_segs) != BIO_MERGE_OK) |
| 1184 | return false; |
| 1185 | *merged_request = attempt_front_merge(q, rq); |
| 1186 | if (!*merged_request) |
| 1187 | elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE); |
| 1188 | return true; |
| 1189 | case ELEVATOR_DISCARD_MERGE: |
| 1190 | return bio_attempt_discard_merge(q, rq, bio) == BIO_MERGE_OK; |
| 1191 | default: |
| 1192 | return false; |
| 1193 | } |
| 1194 | } |
| 1195 | EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge); |