diff options
Diffstat (limited to 'block/blk-merge.c')
| -rw-r--r-- | block/blk-merge.c | 1168 |
1 files changed, 1168 insertions, 0 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c new file mode 100644 index 000000000..258a72607 --- /dev/null +++ b/block/blk-merge.c @@ -0,0 +1,1168 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Functions related to segment and merge handling + */ +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/bio.h> +#include <linux/blkdev.h> +#include <linux/blk-integrity.h> +#include <linux/part_stat.h> +#include <linux/blk-cgroup.h> + +#include <trace/events/block.h> + +#include "blk.h" +#include "blk-mq-sched.h" +#include "blk-rq-qos.h" +#include "blk-throttle.h" + +static inline void bio_get_first_bvec(struct bio *bio, struct bio_vec *bv) +{ + *bv = mp_bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter); +} + +static inline void bio_get_last_bvec(struct bio *bio, struct bio_vec *bv) +{ + struct bvec_iter iter = bio->bi_iter; + int idx; + + bio_get_first_bvec(bio, bv); + if (bv->bv_len == bio->bi_iter.bi_size) + return; /* this bio only has a single bvec */ + + bio_advance_iter(bio, &iter, iter.bi_size); + + if (!iter.bi_offset) + idx = iter.bi_idx - 1; + else /* in the middle of bvec */ + idx = iter.bi_idx; + + *bv = bio->bi_io_vec[idx]; + + /* + * iter.bi_offset records actual length of the last bvec + * if this bio ends in the middle of one io vector + */ + if (iter.bi_offset) + bv->bv_len = iter.bi_offset; +} + +static inline bool bio_will_gap(struct request_queue *q, + struct request *prev_rq, struct bio *prev, struct bio *next) +{ + struct bio_vec pb, nb; + + if (!bio_has_data(prev) || !queue_virt_boundary(q)) + return false; + + /* + * Don't merge if the 1st bio starts with non-zero offset, otherwise it + * is quite difficult to respect the sg gap limit. We work hard to + * merge a huge number of small single bios in case of mkfs. + */ + if (prev_rq) + bio_get_first_bvec(prev_rq->bio, &pb); + else + bio_get_first_bvec(prev, &pb); + if (pb.bv_offset & queue_virt_boundary(q)) + return true; + + /* + * We don't need to worry about the situation that the merged segment + * ends in unaligned virt boundary: + * + * - if 'pb' ends aligned, the merged segment ends aligned + * - if 'pb' ends unaligned, the next bio must include + * one single bvec of 'nb', otherwise the 'nb' can't + * merge with 'pb' + */ + bio_get_last_bvec(prev, &pb); + bio_get_first_bvec(next, &nb); + if (biovec_phys_mergeable(q, &pb, &nb)) + return false; + return __bvec_gap_to_prev(&q->limits, &pb, nb.bv_offset); +} + +static inline bool req_gap_back_merge(struct request *req, struct bio *bio) +{ + return bio_will_gap(req->q, req, req->biotail, bio); +} + +static inline bool req_gap_front_merge(struct request *req, struct bio *bio) +{ + return bio_will_gap(req->q, NULL, bio, req->bio); +} + +/* + * The maximum size that a bio can fit has to be aligned down to the + * logical block size, which is the minimum accepted unit by hardware. + */ +static unsigned int bio_allowed_max_sectors(const struct queue_limits *lim) +{ + return round_down(BIO_MAX_SIZE, lim->logical_block_size) >> + SECTOR_SHIFT; +} + +/* + * bio_submit_split_bioset - Submit a bio, splitting it at a designated sector + * @bio: the original bio to be submitted and split + * @split_sectors: the sector count at which to split + * @bs: the bio set used for allocating the new split bio + * + * The original bio is modified to contain the remaining sectors and submitted. + * The caller is responsible for submitting the returned bio. + * + * If succeed, the newly allocated bio representing the initial part will be + * returned, on failure NULL will be returned and original bio will fail. + */ +struct bio *bio_submit_split_bioset(struct bio *bio, unsigned int split_sectors, + struct bio_set *bs) +{ + struct bio *split = bio_split(bio, split_sectors, GFP_NOIO, bs); + + if (IS_ERR(split)) { + bio_endio_status(bio, errno_to_blk_status(PTR_ERR(split))); + return NULL; + } + + bio_chain(split, bio); + trace_block_split(split, bio->bi_iter.bi_sector); + WARN_ON_ONCE(bio_zone_write_plugging(bio)); + + if (should_fail_bio(bio)) + bio_io_error(bio); + else if (!blk_throtl_bio(bio)) + submit_bio_noacct_nocheck(bio, true); + + return split; +} +EXPORT_SYMBOL_GPL(bio_submit_split_bioset); + +static struct bio *bio_submit_split(struct bio *bio, int split_sectors) +{ + if (unlikely(split_sectors < 0)) { + bio_endio_status(bio, errno_to_blk_status(split_sectors)); + return NULL; + } + + if (split_sectors) { + bio = bio_submit_split_bioset(bio, split_sectors, + &bio->bi_bdev->bd_disk->bio_split); + if (bio) + bio->bi_opf |= REQ_NOMERGE; + } + + return bio; +} + +static struct bio *__bio_split_discard(struct bio *bio, + const struct queue_limits *lim, unsigned *nsegs, + unsigned int max_sectors) +{ + unsigned int max_discard_sectors, granularity; + sector_t tmp; + unsigned split_sectors; + + *nsegs = 1; + + granularity = max(lim->discard_granularity >> 9, 1U); + + max_discard_sectors = min(max_sectors, bio_allowed_max_sectors(lim)); + max_discard_sectors -= max_discard_sectors % granularity; + if (unlikely(!max_discard_sectors)) + return bio; + + if (bio_sectors(bio) <= max_discard_sectors) + return bio; + + split_sectors = max_discard_sectors; + + /* + * If the next starting sector would be misaligned, stop the discard at + * the previous aligned sector. + */ + tmp = bio->bi_iter.bi_sector + split_sectors - + ((lim->discard_alignment >> 9) % granularity); + tmp = sector_div(tmp, granularity); + + if (split_sectors > tmp) + split_sectors -= tmp; + + return bio_submit_split(bio, split_sectors); +} + +struct bio *bio_split_discard(struct bio *bio, const struct queue_limits *lim, + unsigned *nsegs) +{ + unsigned int max_sectors; + + if (bio_op(bio) == REQ_OP_SECURE_ERASE) + max_sectors = lim->max_secure_erase_sectors; + else + max_sectors = lim->max_discard_sectors; + + return __bio_split_discard(bio, lim, nsegs, max_sectors); +} + +static inline unsigned int blk_boundary_sectors(const struct queue_limits *lim, + bool is_atomic) +{ + /* + * chunk_sectors must be a multiple of atomic_write_boundary_sectors if + * both non-zero. + */ + if (is_atomic && lim->atomic_write_boundary_sectors) + return lim->atomic_write_boundary_sectors; + + return lim->chunk_sectors; +} + +/* + * Return the maximum number of sectors from the start of a bio that may be + * submitted as a single request to a block device. If enough sectors remain, + * align the end to the physical block size. Otherwise align the end to the + * logical block size. This approach minimizes the number of non-aligned + * requests that are submitted to a block device if the start of a bio is not + * aligned to a physical block boundary. + */ +static inline unsigned get_max_io_size(struct bio *bio, + const struct queue_limits *lim) +{ + unsigned pbs = lim->physical_block_size >> SECTOR_SHIFT; + unsigned lbs = lim->logical_block_size >> SECTOR_SHIFT; + bool is_atomic = bio->bi_opf & REQ_ATOMIC; + unsigned boundary_sectors = blk_boundary_sectors(lim, is_atomic); + unsigned max_sectors, start, end; + + /* + * We ignore lim->max_sectors for atomic writes because it may less + * than the actual bio size, which we cannot tolerate. + */ + if (bio_op(bio) == REQ_OP_WRITE_ZEROES) + max_sectors = lim->max_write_zeroes_sectors; + else if (is_atomic) + max_sectors = lim->atomic_write_max_sectors; + else + max_sectors = lim->max_sectors; + + if (boundary_sectors) { + max_sectors = min(max_sectors, + blk_boundary_sectors_left(bio->bi_iter.bi_sector, + boundary_sectors)); + } + + start = bio->bi_iter.bi_sector & (pbs - 1); + end = (start + max_sectors) & ~(pbs - 1); + if (end > start) + return end - start; + return max_sectors & ~(lbs - 1); +} + +/** + * bvec_split_segs - verify whether or not a bvec should be split in the middle + * @lim: [in] queue limits to split based on + * @bv: [in] bvec to examine + * @nsegs: [in,out] Number of segments in the bio being built. Incremented + * by the number of segments from @bv that may be appended to that + * bio without exceeding @max_segs + * @bytes: [in,out] Number of bytes in the bio being built. Incremented + * by the number of bytes from @bv that may be appended to that + * bio without exceeding @max_bytes + * @max_segs: [in] upper bound for *@nsegs + * @max_bytes: [in] upper bound for *@bytes + * + * When splitting a bio, it can happen that a bvec is encountered that is too + * big to fit in a single segment and hence that it has to be split in the + * middle. This function verifies whether or not that should happen. The value + * %true is returned if and only if appending the entire @bv to a bio with + * *@nsegs segments and *@sectors sectors would make that bio unacceptable for + * the block driver. + */ +static bool bvec_split_segs(const struct queue_limits *lim, + const struct bio_vec *bv, unsigned *nsegs, unsigned *bytes, + unsigned max_segs, unsigned max_bytes) +{ + unsigned max_len = max_bytes - *bytes; + unsigned len = min(bv->bv_len, max_len); + unsigned total_len = 0; + unsigned seg_size = 0; + + while (len && *nsegs < max_segs) { + seg_size = get_max_segment_size(lim, bvec_phys(bv) + total_len, len); + + (*nsegs)++; + total_len += seg_size; + len -= seg_size; + + if ((bv->bv_offset + total_len) & lim->virt_boundary_mask) + break; + } + + *bytes += total_len; + + /* tell the caller to split the bvec if it is too big to fit */ + return len > 0 || bv->bv_len > max_len; +} + +static unsigned int bio_split_alignment(struct bio *bio, + const struct queue_limits *lim) +{ + if (op_is_write(bio_op(bio)) && lim->zone_write_granularity) + return lim->zone_write_granularity; + return lim->logical_block_size; +} + +static inline unsigned int bvec_seg_gap(struct bio_vec *bvprv, + struct bio_vec *bv) +{ + return bv->bv_offset | (bvprv->bv_offset + bvprv->bv_len); +} + +/** + * bio_split_io_at - check if and where to split a bio + * @bio: [in] bio to be split + * @lim: [in] queue limits to split based on + * @segs: [out] number of segments in the bio with the first half of the sectors + * @max_bytes: [in] maximum number of bytes per bio + * @len_align_mask: [in] length alignment mask for each vector + * + * Find out if @bio needs to be split to fit the queue limits in @lim and a + * maximum size of @max_bytes. Returns a negative error number if @bio can't be + * split, 0 if the bio doesn't have to be split, or a positive sector offset if + * @bio needs to be split. + */ +int bio_split_io_at(struct bio *bio, const struct queue_limits *lim, + unsigned *segs, unsigned max_bytes, unsigned len_align_mask) +{ + struct bio_crypt_ctx *bc = bio_crypt_ctx(bio); + struct bio_vec bv, bvprv, *bvprvp = NULL; + unsigned nsegs = 0, bytes = 0, gaps = 0; + struct bvec_iter iter; + unsigned start_align_mask = lim->dma_alignment; + + if (bc) { + start_align_mask |= (bc->bc_key->crypto_cfg.data_unit_size - 1); + len_align_mask |= (bc->bc_key->crypto_cfg.data_unit_size - 1); + } + + bio_for_each_bvec(bv, bio, iter) { + if (bv.bv_offset & start_align_mask || + bv.bv_len & len_align_mask) + return -EINVAL; + + /* + * If the queue doesn't support SG gaps and adding this + * offset would create a gap, disallow it. + */ + if (bvprvp) { + if (bvec_gap_to_prev(lim, bvprvp, bv.bv_offset)) + goto split; + gaps |= bvec_seg_gap(bvprvp, &bv); + } + + if (nsegs < lim->max_segments && + bytes + bv.bv_len <= max_bytes && + bv.bv_offset + bv.bv_len <= lim->max_fast_segment_size) { + nsegs++; + bytes += bv.bv_len; + } else { + if (bvec_split_segs(lim, &bv, &nsegs, &bytes, + lim->max_segments, max_bytes)) + goto split; + } + + bvprv = bv; + bvprvp = &bvprv; + } + + *segs = nsegs; + bio->bi_bvec_gap_bit = ffs(gaps); + return 0; +split: + if (bio->bi_opf & REQ_ATOMIC) + return -EINVAL; + + /* + * We can't sanely support splitting for a REQ_NOWAIT bio. End it + * with EAGAIN if splitting is required and return an error pointer. + */ + if (bio->bi_opf & REQ_NOWAIT) + return -EAGAIN; + + *segs = nsegs; + + /* + * Individual bvecs might not be logical block aligned. Round down the + * split size so that each bio is properly block size aligned, even if + * we do not use the full hardware limits. + * + * It is possible to submit a bio that can't be split into a valid io: + * there may either be too many discontiguous vectors for the max + * segments limit, or contain virtual boundary gaps without having a + * valid block sized split. A zero byte result means one of those + * conditions occured. + */ + bytes = ALIGN_DOWN(bytes, bio_split_alignment(bio, lim)); + if (!bytes) + return -EINVAL; + + /* + * Bio splitting may cause subtle trouble such as hang when doing sync + * iopoll in direct IO routine. Given performance gain of iopoll for + * big IO can be trival, disable iopoll when split needed. + */ + bio_clear_polled(bio); + bio->bi_bvec_gap_bit = ffs(gaps); + return bytes >> SECTOR_SHIFT; +} +EXPORT_SYMBOL_GPL(bio_split_io_at); + +struct bio *bio_split_rw(struct bio *bio, const struct queue_limits *lim, + unsigned *nr_segs) +{ + return bio_submit_split(bio, + bio_split_rw_at(bio, lim, nr_segs, + get_max_io_size(bio, lim) << SECTOR_SHIFT)); +} + +/* + * REQ_OP_ZONE_APPEND bios must never be split by the block layer. + * + * But we want the nr_segs calculation provided by bio_split_rw_at, and having + * a good sanity check that the submitter built the bio correctly is nice to + * have as well. + */ +struct bio *bio_split_zone_append(struct bio *bio, + const struct queue_limits *lim, unsigned *nr_segs) +{ + int split_sectors; + + split_sectors = bio_split_rw_at(bio, lim, nr_segs, + lim->max_zone_append_sectors << SECTOR_SHIFT); + if (WARN_ON_ONCE(split_sectors > 0)) + split_sectors = -EINVAL; + return bio_submit_split(bio, split_sectors); +} + +struct bio *bio_split_write_zeroes(struct bio *bio, + const struct queue_limits *lim, unsigned *nsegs) +{ + unsigned int max_sectors = get_max_io_size(bio, lim); + + *nsegs = 0; + + /* + * An unset limit should normally not happen, as bio submission is keyed + * off having a non-zero limit. But SCSI can clear the limit in the + * I/O completion handler, and we can race and see this. Splitting to a + * zero limit obviously doesn't make sense, so band-aid it here. + */ + if (!max_sectors) + return bio; + if (bio_sectors(bio) <= max_sectors) + return bio; + return bio_submit_split(bio, max_sectors); +} + +/** + * bio_split_to_limits - split a bio to fit the queue limits + * @bio: bio to be split + * + * Check if @bio needs splitting based on the queue limits of @bio->bi_bdev, and + * if so split off a bio fitting the limits from the beginning of @bio and + * return it. @bio is shortened to the remainder and re-submitted. + * + * The split bio is allocated from @q->bio_split, which is provided by the + * block layer. + */ +struct bio *bio_split_to_limits(struct bio *bio) +{ + unsigned int nr_segs; + + return __bio_split_to_limits(bio, bdev_limits(bio->bi_bdev), &nr_segs); +} +EXPORT_SYMBOL(bio_split_to_limits); + +unsigned int blk_recalc_rq_segments(struct request *rq) +{ + unsigned int nr_phys_segs = 0; + unsigned int bytes = 0; + struct req_iterator iter; + struct bio_vec bv; + + if (!rq->bio) + return 0; + + switch (bio_op(rq->bio)) { + case REQ_OP_DISCARD: + case REQ_OP_SECURE_ERASE: + if (queue_max_discard_segments(rq->q) > 1) { + struct bio *bio = rq->bio; + + for_each_bio(bio) + nr_phys_segs++; + return nr_phys_segs; + } + return 1; + case REQ_OP_WRITE_ZEROES: + return 0; + default: + break; + } + + rq_for_each_bvec(bv, rq, iter) + bvec_split_segs(&rq->q->limits, &bv, &nr_phys_segs, &bytes, + UINT_MAX, BIO_MAX_SIZE); + return nr_phys_segs; +} + +static inline unsigned int blk_rq_get_max_sectors(struct request *rq, + sector_t offset) +{ + struct request_queue *q = rq->q; + struct queue_limits *lim = &q->limits; + unsigned int max_sectors, boundary_sectors; + bool is_atomic = rq->cmd_flags & REQ_ATOMIC; + + if (blk_rq_is_passthrough(rq)) + return q->limits.max_hw_sectors; + + boundary_sectors = blk_boundary_sectors(lim, is_atomic); + max_sectors = blk_queue_get_max_sectors(rq); + + if (!boundary_sectors || + req_op(rq) == REQ_OP_DISCARD || + req_op(rq) == REQ_OP_SECURE_ERASE) + return max_sectors; + return min(max_sectors, + blk_boundary_sectors_left(offset, boundary_sectors)); +} + +static inline int ll_new_hw_segment(struct request *req, struct bio *bio, + unsigned int nr_phys_segs) +{ + if (!blk_cgroup_mergeable(req, bio)) + goto no_merge; + + if (unlikely(!blk_integrity_merge_bio(req->q, req, bio))) + goto no_merge; + + /* discard request merge won't add new segment */ + if (req_op(req) == REQ_OP_DISCARD) + return 1; + + if (req->nr_phys_segments + nr_phys_segs > blk_rq_get_max_segments(req)) + goto no_merge; + + /* + * This will form the start of a new hw segment. Bump both + * counters. + */ + req->nr_phys_segments += nr_phys_segs; + if (bio_integrity(bio)) + req->nr_integrity_segments += blk_rq_count_integrity_sg(req->q, + bio); + return 1; + +no_merge: + req_set_nomerge(req->q, req); + return 0; +} + +int ll_back_merge_fn(struct request *req, struct bio *bio, unsigned int nr_segs) +{ + if (req_gap_back_merge(req, bio)) + return 0; + if (blk_integrity_rq(req) && + integrity_req_gap_back_merge(req, bio)) + return 0; + if (!bio_crypt_ctx_back_mergeable(req, bio)) + return 0; + if (blk_rq_sectors(req) + bio_sectors(bio) > + blk_rq_get_max_sectors(req, blk_rq_pos(req))) { + req_set_nomerge(req->q, req); + return 0; + } + + return ll_new_hw_segment(req, bio, nr_segs); +} + +static int ll_front_merge_fn(struct request *req, struct bio *bio, + unsigned int nr_segs) +{ + if (req_gap_front_merge(req, bio)) + return 0; + if (blk_integrity_rq(req) && + integrity_req_gap_front_merge(req, bio)) + return 0; + if (!bio_crypt_ctx_front_mergeable(req, bio)) + return 0; + if (blk_rq_sectors(req) + bio_sectors(bio) > + blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) { + req_set_nomerge(req->q, req); + return 0; + } + + return ll_new_hw_segment(req, bio, nr_segs); +} + +static bool req_attempt_discard_merge(struct request_queue *q, struct request *req, + struct request *next) +{ + unsigned short segments = blk_rq_nr_discard_segments(req); + + if (segments >= queue_max_discard_segments(q)) + goto no_merge; + if (blk_rq_sectors(req) + bio_sectors(next->bio) > + blk_rq_get_max_sectors(req, blk_rq_pos(req))) + goto no_merge; + + req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next); + return true; +no_merge: + req_set_nomerge(q, req); + return false; +} + +static int ll_merge_requests_fn(struct request_queue *q, struct request *req, + struct request *next) +{ + int total_phys_segments; + + if (req_gap_back_merge(req, next->bio)) + return 0; + + /* + * Will it become too large? + */ + if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > + blk_rq_get_max_sectors(req, blk_rq_pos(req))) + return 0; + + total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; + if (total_phys_segments > blk_rq_get_max_segments(req)) + return 0; + + if (!blk_cgroup_mergeable(req, next->bio)) + return 0; + + if (unlikely(!blk_integrity_merge_rq(q, req, next))) + return 0; + + if (!bio_crypt_ctx_merge_rq(req, next)) + return 0; + + /* Merge is OK... */ + req->nr_phys_segments = total_phys_segments; + req->nr_integrity_segments += next->nr_integrity_segments; + return 1; +} + +/** + * blk_rq_set_mixed_merge - mark a request as mixed merge + * @rq: request to mark as mixed merge + * + * Description: + * @rq is about to be mixed merged. Make sure the attributes + * which can be mixed are set in each bio and mark @rq as mixed + * merged. + */ +static void blk_rq_set_mixed_merge(struct request *rq) +{ + blk_opf_t ff = rq->cmd_flags & REQ_FAILFAST_MASK; + struct bio *bio; + + if (rq->rq_flags & RQF_MIXED_MERGE) + return; + + /* + * @rq will no longer represent mixable attributes for all the + * contained bios. It will just track those of the first one. + * Distributes the attributs to each bio. + */ + for (bio = rq->bio; bio; bio = bio->bi_next) { + WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) && + (bio->bi_opf & REQ_FAILFAST_MASK) != ff); + bio->bi_opf |= ff; + } + rq->rq_flags |= RQF_MIXED_MERGE; +} + +static inline blk_opf_t bio_failfast(const struct bio *bio) +{ + if (bio->bi_opf & REQ_RAHEAD) + return REQ_FAILFAST_MASK; + + return bio->bi_opf & REQ_FAILFAST_MASK; +} + +/* + * After we are marked as MIXED_MERGE, any new RA bio has to be updated + * as failfast, and request's failfast has to be updated in case of + * front merge. + */ +static inline void blk_update_mixed_merge(struct request *req, + struct bio *bio, bool front_merge) +{ + if (req->rq_flags & RQF_MIXED_MERGE) { + if (bio->bi_opf & REQ_RAHEAD) + bio->bi_opf |= REQ_FAILFAST_MASK; + + if (front_merge) { + req->cmd_flags &= ~REQ_FAILFAST_MASK; + req->cmd_flags |= bio->bi_opf & REQ_FAILFAST_MASK; + } + } +} + +static void blk_account_io_merge_request(struct request *req) +{ + if (req->rq_flags & RQF_IO_STAT) { + part_stat_lock(); + part_stat_inc(req->part, merges[op_stat_group(req_op(req))]); + bdev_dec_in_flight(req->part, req_op(req)); + part_stat_unlock(); + } +} + +static enum elv_merge blk_try_req_merge(struct request *req, + struct request *next) +{ + if (blk_discard_mergable(req)) + return ELEVATOR_DISCARD_MERGE; + else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next)) + return ELEVATOR_BACK_MERGE; + + return ELEVATOR_NO_MERGE; +} + +static bool blk_atomic_write_mergeable_rq_bio(struct request *rq, + struct bio *bio) +{ + return (rq->cmd_flags & REQ_ATOMIC) == (bio->bi_opf & REQ_ATOMIC); +} + +static bool blk_atomic_write_mergeable_rqs(struct request *rq, + struct request *next) +{ + return (rq->cmd_flags & REQ_ATOMIC) == (next->cmd_flags & REQ_ATOMIC); +} + +u8 bio_seg_gap(struct request_queue *q, struct bio *prev, struct bio *next, + u8 gaps_bit) +{ + struct bio_vec pb, nb; + + if (!bio_has_data(prev)) + return 0; + + gaps_bit = min_not_zero(gaps_bit, prev->bi_bvec_gap_bit); + gaps_bit = min_not_zero(gaps_bit, next->bi_bvec_gap_bit); + + bio_get_last_bvec(prev, &pb); + bio_get_first_bvec(next, &nb); + if (!biovec_phys_mergeable(q, &pb, &nb)) + gaps_bit = min_not_zero(gaps_bit, ffs(bvec_seg_gap(&pb, &nb))); + return gaps_bit; +} + +/* + * For non-mq, this has to be called with the request spinlock acquired. + * For mq with scheduling, the appropriate queue wide lock should be held. + */ +static struct request *attempt_merge(struct request_queue *q, + struct request *req, struct request *next) +{ + if (!rq_mergeable(req) || !rq_mergeable(next)) + return NULL; + + if (req_op(req) != req_op(next)) + return NULL; + + if (req->bio->bi_write_hint != next->bio->bi_write_hint) + return NULL; + if (req->bio->bi_write_stream != next->bio->bi_write_stream) + return NULL; + if (req->bio->bi_ioprio != next->bio->bi_ioprio) + return NULL; + if (!blk_atomic_write_mergeable_rqs(req, next)) + return NULL; + + /* + * If we are allowed to merge, then append bio list + * from next to rq and release next. merge_requests_fn + * will have updated segment counts, update sector + * counts here. Handle DISCARDs separately, as they + * have separate settings. + */ + + switch (blk_try_req_merge(req, next)) { + case ELEVATOR_DISCARD_MERGE: + if (!req_attempt_discard_merge(q, req, next)) + return NULL; + break; + case ELEVATOR_BACK_MERGE: + if (!ll_merge_requests_fn(q, req, next)) + return NULL; + break; + default: + return NULL; + } + + /* + * If failfast settings disagree or any of the two is already + * a mixed merge, mark both as mixed before proceeding. This + * makes sure that all involved bios have mixable attributes + * set properly. + */ + if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) || + (req->cmd_flags & REQ_FAILFAST_MASK) != + (next->cmd_flags & REQ_FAILFAST_MASK)) { + blk_rq_set_mixed_merge(req); + blk_rq_set_mixed_merge(next); + } + + /* + * At this point we have either done a back merge or front merge. We + * need the smaller start_time_ns of the merged requests to be the + * current request for accounting purposes. + */ + if (next->start_time_ns < req->start_time_ns) + req->start_time_ns = next->start_time_ns; + + req->phys_gap_bit = bio_seg_gap(req->q, req->biotail, next->bio, + min_not_zero(next->phys_gap_bit, + req->phys_gap_bit)); + req->biotail->bi_next = next->bio; + req->biotail = next->biotail; + + req->__data_len += blk_rq_bytes(next); + + if (!blk_discard_mergable(req)) + elv_merge_requests(q, req, next); + + blk_crypto_rq_put_keyslot(next); + + /* + * 'next' is going away, so update stats accordingly + */ + blk_account_io_merge_request(next); + + trace_block_rq_merge(next); + + /* + * ownership of bio passed from next to req, return 'next' for + * the caller to free + */ + next->bio = NULL; + return next; +} + +static struct request *attempt_back_merge(struct request_queue *q, + struct request *rq) +{ + struct request *next = elv_latter_request(q, rq); + + if (next) + return attempt_merge(q, rq, next); + + return NULL; +} + +static struct request *attempt_front_merge(struct request_queue *q, + struct request *rq) +{ + struct request *prev = elv_former_request(q, rq); + + if (prev) + return attempt_merge(q, prev, rq); + + return NULL; +} + +/* + * Try to merge 'next' into 'rq'. Return true if the merge happened, false + * otherwise. The caller is responsible for freeing 'next' if the merge + * happened. + */ +bool blk_attempt_req_merge(struct request_queue *q, struct request *rq, + struct request *next) +{ + return attempt_merge(q, rq, next); +} + +bool blk_rq_merge_ok(struct request *rq, struct bio *bio) +{ + if (!rq_mergeable(rq) || !bio_mergeable(bio)) + return false; + + if (req_op(rq) != bio_op(bio)) + return false; + + if (!blk_cgroup_mergeable(rq, bio)) + return false; + if (unlikely(!blk_integrity_merge_bio(rq->q, rq, bio))) + return false; + if (!bio_crypt_rq_ctx_compatible(rq, bio)) + return false; + if (rq->bio->bi_write_hint != bio->bi_write_hint) + return false; + if (rq->bio->bi_write_stream != bio->bi_write_stream) + return false; + if (rq->bio->bi_ioprio != bio->bi_ioprio) + return false; + if (unlikely(!blk_atomic_write_mergeable_rq_bio(rq, bio))) + return false; + + return true; +} + +enum elv_merge blk_try_merge(struct request *rq, struct bio *bio) +{ + if (blk_discard_mergable(rq)) + return ELEVATOR_DISCARD_MERGE; + else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) + return ELEVATOR_BACK_MERGE; + else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) + return ELEVATOR_FRONT_MERGE; + return ELEVATOR_NO_MERGE; +} + +static void blk_account_io_merge_bio(struct request *req) +{ + if (req->rq_flags & RQF_IO_STAT) { + part_stat_lock(); + part_stat_inc(req->part, merges[op_stat_group(req_op(req))]); + part_stat_unlock(); + } +} + +enum bio_merge_status bio_attempt_back_merge(struct request *req, + struct bio *bio, unsigned int nr_segs) +{ + const blk_opf_t ff = bio_failfast(bio); + + if (!ll_back_merge_fn(req, bio, nr_segs)) + return BIO_MERGE_FAILED; + + trace_block_bio_backmerge(bio); + rq_qos_merge(req->q, req, bio); + + if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) + blk_rq_set_mixed_merge(req); + + blk_update_mixed_merge(req, bio, false); + + if (req->rq_flags & RQF_ZONE_WRITE_PLUGGING) + blk_zone_write_plug_bio_merged(bio); + + req->phys_gap_bit = bio_seg_gap(req->q, req->biotail, bio, + req->phys_gap_bit); + req->biotail->bi_next = bio; + req->biotail = bio; + req->__data_len += bio->bi_iter.bi_size; + + bio_crypt_free_ctx(bio); + + blk_account_io_merge_bio(req); + return BIO_MERGE_OK; +} + +static enum bio_merge_status bio_attempt_front_merge(struct request *req, + struct bio *bio, unsigned int nr_segs) +{ + const blk_opf_t ff = bio_failfast(bio); + + /* + * A front merge for writes to sequential zones of a zoned block device + * can happen only if the user submitted writes out of order. Do not + * merge such write to let it fail. + */ + if (req->rq_flags & RQF_ZONE_WRITE_PLUGGING) + return BIO_MERGE_FAILED; + + if (!ll_front_merge_fn(req, bio, nr_segs)) + return BIO_MERGE_FAILED; + + trace_block_bio_frontmerge(bio); + rq_qos_merge(req->q, req, bio); + + if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) + blk_rq_set_mixed_merge(req); + + blk_update_mixed_merge(req, bio, true); + + req->phys_gap_bit = bio_seg_gap(req->q, bio, req->bio, + req->phys_gap_bit); + bio->bi_next = req->bio; + req->bio = bio; + + req->__sector = bio->bi_iter.bi_sector; + req->__data_len += bio->bi_iter.bi_size; + + bio_crypt_do_front_merge(req, bio); + + blk_account_io_merge_bio(req); + return BIO_MERGE_OK; +} + +static enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q, + struct request *req, struct bio *bio) +{ + unsigned short segments = blk_rq_nr_discard_segments(req); + + if (segments >= queue_max_discard_segments(q)) + goto no_merge; + if (blk_rq_sectors(req) + bio_sectors(bio) > + blk_rq_get_max_sectors(req, blk_rq_pos(req))) + goto no_merge; + + rq_qos_merge(q, req, bio); + + req->biotail->bi_next = bio; + req->biotail = bio; + req->__data_len += bio->bi_iter.bi_size; + req->nr_phys_segments = segments + 1; + + blk_account_io_merge_bio(req); + return BIO_MERGE_OK; +no_merge: + req_set_nomerge(q, req); + return BIO_MERGE_FAILED; +} + +static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q, + struct request *rq, + struct bio *bio, + unsigned int nr_segs, + bool sched_allow_merge) +{ + if (!blk_rq_merge_ok(rq, bio)) + return BIO_MERGE_NONE; + + switch (blk_try_merge(rq, bio)) { + case ELEVATOR_BACK_MERGE: + if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio)) + return bio_attempt_back_merge(rq, bio, nr_segs); + break; + case ELEVATOR_FRONT_MERGE: + if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio)) + return bio_attempt_front_merge(rq, bio, nr_segs); + break; + case ELEVATOR_DISCARD_MERGE: + return bio_attempt_discard_merge(q, rq, bio); + default: + return BIO_MERGE_NONE; + } + + return BIO_MERGE_FAILED; +} + +/** + * blk_attempt_plug_merge - try to merge with %current's plugged list + * @q: request_queue new bio is being queued at + * @bio: new bio being queued + * @nr_segs: number of segments in @bio + * from the passed in @q already in the plug list + * + * Determine whether @bio being queued on @q can be merged with the previous + * request on %current's plugged list. Returns %true if merge was successful, + * otherwise %false. + * + * Plugging coalesces IOs from the same issuer for the same purpose without + * going through @q->queue_lock. As such it's more of an issuing mechanism + * than scheduling, and the request, while may have elvpriv data, is not + * added on the elevator at this point. In addition, we don't have + * reliable access to the elevator outside queue lock. Only check basic + * merging parameters without querying the elevator. + * + * Caller must ensure !blk_queue_nomerges(q) beforehand. + */ +bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio, + unsigned int nr_segs) +{ + struct blk_plug *plug = current->plug; + struct request *rq; + + if (!plug || rq_list_empty(&plug->mq_list)) + return false; + + rq = plug->mq_list.tail; + if (rq->q == q) + return blk_attempt_bio_merge(q, rq, bio, nr_segs, false) == + BIO_MERGE_OK; + else if (!plug->multiple_queues) + return false; + + rq_list_for_each(&plug->mq_list, rq) { + if (rq->q != q) + continue; + if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) == + BIO_MERGE_OK) + return true; + break; + } + return false; +} + +/* + * Iterate list of requests and see if we can merge this bio with any + * of them. + */ +bool blk_bio_list_merge(struct request_queue *q, struct list_head *list, + struct bio *bio, unsigned int nr_segs) +{ + struct request *rq; + int checked = 8; + + list_for_each_entry_reverse(rq, list, queuelist) { + if (!checked--) + break; + + switch (blk_attempt_bio_merge(q, rq, bio, nr_segs, true)) { + case BIO_MERGE_NONE: + continue; + case BIO_MERGE_OK: + return true; + case BIO_MERGE_FAILED: + return false; + } + + } + + return false; +} +EXPORT_SYMBOL_GPL(blk_bio_list_merge); + +bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio, + unsigned int nr_segs, struct request **merged_request) +{ + struct request *rq; + + switch (elv_merge(q, &rq, bio)) { + case ELEVATOR_BACK_MERGE: + if (!blk_mq_sched_allow_merge(q, rq, bio)) + return false; + if (bio_attempt_back_merge(rq, bio, nr_segs) != BIO_MERGE_OK) + return false; + *merged_request = attempt_back_merge(q, rq); + if (!*merged_request) + elv_merged_request(q, rq, ELEVATOR_BACK_MERGE); + return true; + case ELEVATOR_FRONT_MERGE: + if (!blk_mq_sched_allow_merge(q, rq, bio)) + return false; + if (bio_attempt_front_merge(rq, bio, nr_segs) != BIO_MERGE_OK) + return false; + *merged_request = attempt_front_merge(q, rq); + if (!*merged_request) + elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE); + return true; + case ELEVATOR_DISCARD_MERGE: + return bio_attempt_discard_merge(q, rq, bio) == BIO_MERGE_OK; + default: + return false; + } +} +EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge); |