diff options
Diffstat (limited to 'block/blk-merge.c')
| -rw-r--r-- | block/blk-merge.c | 1147 |
1 files changed, 1147 insertions, 0 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c new file mode 100644 index 000000000..f3b016b31 --- /dev/null +++ b/block/blk-merge.c @@ -0,0 +1,1147 @@ +// 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/scatterlist.h> +#include <linux/blk-cgroup.h> + +#include <trace/events/block.h> + +#include "blk.h" +#include "blk-rq-qos.h" + +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, &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); +} + +static struct bio *blk_bio_discard_split(struct request_queue *q, + struct bio *bio, + struct bio_set *bs, + unsigned *nsegs) +{ + unsigned int max_discard_sectors, granularity; + int alignment; + sector_t tmp; + unsigned split_sectors; + + *nsegs = 1; + + /* Zero-sector (unknown) and one-sector granularities are the same. */ + granularity = max(q->limits.discard_granularity >> 9, 1U); + + max_discard_sectors = min(q->limits.max_discard_sectors, + bio_allowed_max_sectors(q)); + max_discard_sectors -= max_discard_sectors % granularity; + + if (unlikely(!max_discard_sectors)) { + /* XXX: warn */ + return NULL; + } + + if (bio_sectors(bio) <= max_discard_sectors) + return NULL; + + split_sectors = max_discard_sectors; + + /* + * If the next starting sector would be misaligned, stop the discard at + * the previous aligned sector. + */ + alignment = (q->limits.discard_alignment >> 9) % granularity; + + tmp = bio->bi_iter.bi_sector + split_sectors - alignment; + tmp = sector_div(tmp, granularity); + + if (split_sectors > tmp) + split_sectors -= tmp; + + return bio_split(bio, split_sectors, GFP_NOIO, bs); +} + +static struct bio *blk_bio_write_zeroes_split(struct request_queue *q, + struct bio *bio, struct bio_set *bs, unsigned *nsegs) +{ + *nsegs = 0; + + if (!q->limits.max_write_zeroes_sectors) + return NULL; + + if (bio_sectors(bio) <= q->limits.max_write_zeroes_sectors) + return NULL; + + return bio_split(bio, q->limits.max_write_zeroes_sectors, GFP_NOIO, bs); +} + +static struct bio *blk_bio_write_same_split(struct request_queue *q, + struct bio *bio, + struct bio_set *bs, + unsigned *nsegs) +{ + *nsegs = 1; + + if (!q->limits.max_write_same_sectors) + return NULL; + + if (bio_sectors(bio) <= q->limits.max_write_same_sectors) + return NULL; + + return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs); +} + +/* + * 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 request_queue *q, + struct bio *bio) +{ + unsigned sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector, 0); + unsigned max_sectors = sectors; + unsigned pbs = queue_physical_block_size(q) >> SECTOR_SHIFT; + unsigned lbs = queue_logical_block_size(q) >> SECTOR_SHIFT; + unsigned start_offset = bio->bi_iter.bi_sector & (pbs - 1); + + max_sectors += start_offset; + max_sectors &= ~(pbs - 1); + if (max_sectors > start_offset) + return max_sectors - start_offset; + + return sectors & ~(lbs - 1); +} + +static inline unsigned get_max_segment_size(const struct request_queue *q, + struct page *start_page, + unsigned long offset) +{ + unsigned long mask = queue_segment_boundary(q); + + offset = mask & (page_to_phys(start_page) + offset); + + /* + * overflow may be triggered in case of zero page physical address + * on 32bit arch, use queue's max segment size when that happens. + */ + return min_not_zero(mask - offset + 1, + (unsigned long)queue_max_segment_size(q)); +} + +/** + * bvec_split_segs - verify whether or not a bvec should be split in the middle + * @q: [in] request queue associated with the bio associated with @bv + * @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 + * @sectors: [in,out] Number of sectors in the bio being built. Incremented + * by the number of sectors from @bv that may be appended to that + * bio without exceeding @max_sectors + * @max_segs: [in] upper bound for *@nsegs + * @max_sectors: [in] upper bound for *@sectors + * + * 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 request_queue *q, + const struct bio_vec *bv, unsigned *nsegs, + unsigned *sectors, unsigned max_segs, + unsigned max_sectors) +{ + unsigned max_len = (min(max_sectors, UINT_MAX >> 9) - *sectors) << 9; + 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(q, bv->bv_page, + bv->bv_offset + total_len); + seg_size = min(seg_size, len); + + (*nsegs)++; + total_len += seg_size; + len -= seg_size; + + if ((bv->bv_offset + total_len) & queue_virt_boundary(q)) + break; + } + + *sectors += total_len >> 9; + + /* tell the caller to split the bvec if it is too big to fit */ + return len > 0 || bv->bv_len > max_len; +} + +/** + * blk_bio_segment_split - split a bio in two bios + * @q: [in] request queue pointer + * @bio: [in] bio to be split + * @bs: [in] bio set to allocate the clone from + * @segs: [out] number of segments in the bio with the first half of the sectors + * + * Clone @bio, update the bi_iter of the clone to represent the first sectors + * of @bio and update @bio->bi_iter to represent the remaining sectors. The + * following is guaranteed for the cloned bio: + * - That it has at most get_max_io_size(@q, @bio) sectors. + * - That it has at most queue_max_segments(@q) segments. + * + * Except for discard requests the cloned bio will point at the bi_io_vec of + * the original bio. It is the responsibility of the caller to ensure that the + * original bio is not freed before the cloned bio. The caller is also + * responsible for ensuring that @bs is only destroyed after processing of the + * split bio has finished. + */ +static struct bio *blk_bio_segment_split(struct request_queue *q, + struct bio *bio, + struct bio_set *bs, + unsigned *segs) +{ + struct bio_vec bv, bvprv, *bvprvp = NULL; + struct bvec_iter iter; + unsigned nsegs = 0, sectors = 0; + const unsigned max_sectors = get_max_io_size(q, bio); + const unsigned max_segs = queue_max_segments(q); + + bio_for_each_bvec(bv, bio, iter) { + /* + * If the queue doesn't support SG gaps and adding this + * offset would create a gap, disallow it. + */ + if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset)) + goto split; + + if (nsegs < max_segs && + sectors + (bv.bv_len >> 9) <= max_sectors && + bv.bv_offset + bv.bv_len <= PAGE_SIZE) { + nsegs++; + sectors += bv.bv_len >> 9; + } else if (bvec_split_segs(q, &bv, &nsegs, §ors, max_segs, + max_sectors)) { + goto split; + } + + bvprv = bv; + bvprvp = &bvprv; + } + + *segs = nsegs; + return NULL; +split: + *segs = nsegs; + return bio_split(bio, sectors, GFP_NOIO, bs); +} + +/** + * __blk_queue_split - split a bio and submit the second half + * @bio: [in, out] bio to be split + * @nr_segs: [out] number of segments in the first bio + * + * Split a bio into two bios, chain the two bios, submit the second half and + * store a pointer to the first half in *@bio. If the second bio is still too + * big it will be split by a recursive call to this function. Since this + * function may allocate a new bio from @bio->bi_disk->queue->bio_split, it is + * the responsibility of the caller to ensure that + * @bio->bi_disk->queue->bio_split is only released after processing of the + * split bio has finished. + */ +void __blk_queue_split(struct bio **bio, unsigned int *nr_segs) +{ + struct request_queue *q = (*bio)->bi_disk->queue; + struct bio *split = NULL; + + switch (bio_op(*bio)) { + case REQ_OP_DISCARD: + case REQ_OP_SECURE_ERASE: + split = blk_bio_discard_split(q, *bio, &q->bio_split, nr_segs); + break; + case REQ_OP_WRITE_ZEROES: + split = blk_bio_write_zeroes_split(q, *bio, &q->bio_split, + nr_segs); + break; + case REQ_OP_WRITE_SAME: + split = blk_bio_write_same_split(q, *bio, &q->bio_split, + nr_segs); + break; + default: + /* + * All drivers must accept single-segments bios that are <= + * PAGE_SIZE. This is a quick and dirty check that relies on + * the fact that bi_io_vec[0] is always valid if a bio has data. + * The check might lead to occasional false negatives when bios + * are cloned, but compared to the performance impact of cloned + * bios themselves the loop below doesn't matter anyway. + */ + if (!q->limits.chunk_sectors && + (*bio)->bi_vcnt == 1 && + ((*bio)->bi_io_vec[0].bv_len + + (*bio)->bi_io_vec[0].bv_offset) <= PAGE_SIZE) { + *nr_segs = 1; + break; + } + split = blk_bio_segment_split(q, *bio, &q->bio_split, nr_segs); + break; + } + + if (split) { + /* there isn't chance to merge the splitted bio */ + split->bi_opf |= REQ_NOMERGE; + + bio_chain(split, *bio); + trace_block_split(q, split, (*bio)->bi_iter.bi_sector); + submit_bio_noacct(*bio); + *bio = split; + + blk_throtl_charge_bio_split(*bio); + } +} + +/** + * blk_queue_split - split a bio and submit the second half + * @bio: [in, out] bio to be split + * + * Split a bio into two bios, chains the two bios, submit the second half and + * store a pointer to the first half in *@bio. Since this function may allocate + * a new bio from @bio->bi_disk->queue->bio_split, it is the responsibility of + * the caller to ensure that @bio->bi_disk->queue->bio_split is only released + * after processing of the split bio has finished. + */ +void blk_queue_split(struct bio **bio) +{ + unsigned int nr_segs; + + __blk_queue_split(bio, &nr_segs); +} +EXPORT_SYMBOL(blk_queue_split); + +unsigned int blk_recalc_rq_segments(struct request *rq) +{ + unsigned int nr_phys_segs = 0; + unsigned int nr_sectors = 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; + case REQ_OP_WRITE_SAME: + return 1; + } + + rq_for_each_bvec(bv, rq, iter) + bvec_split_segs(rq->q, &bv, &nr_phys_segs, &nr_sectors, + UINT_MAX, UINT_MAX); + return nr_phys_segs; +} + +static inline struct scatterlist *blk_next_sg(struct scatterlist **sg, + struct scatterlist *sglist) +{ + if (!*sg) + return sglist; + + /* + * If the driver previously mapped a shorter list, we could see a + * termination bit prematurely unless it fully inits the sg table + * on each mapping. We KNOW that there must be more entries here + * or the driver would be buggy, so force clear the termination bit + * to avoid doing a full sg_init_table() in drivers for each command. + */ + sg_unmark_end(*sg); + return sg_next(*sg); +} + +static unsigned blk_bvec_map_sg(struct request_queue *q, + struct bio_vec *bvec, struct scatterlist *sglist, + struct scatterlist **sg) +{ + unsigned nbytes = bvec->bv_len; + unsigned nsegs = 0, total = 0; + + while (nbytes > 0) { + unsigned offset = bvec->bv_offset + total; + unsigned len = min(get_max_segment_size(q, bvec->bv_page, + offset), nbytes); + struct page *page = bvec->bv_page; + + /* + * Unfortunately a fair number of drivers barf on scatterlists + * that have an offset larger than PAGE_SIZE, despite other + * subsystems dealing with that invariant just fine. For now + * stick to the legacy format where we never present those from + * the block layer, but the code below should be removed once + * these offenders (mostly MMC/SD drivers) are fixed. + */ + page += (offset >> PAGE_SHIFT); + offset &= ~PAGE_MASK; + + *sg = blk_next_sg(sg, sglist); + sg_set_page(*sg, page, len, offset); + + total += len; + nbytes -= len; + nsegs++; + } + + return nsegs; +} + +static inline int __blk_bvec_map_sg(struct bio_vec bv, + struct scatterlist *sglist, struct scatterlist **sg) +{ + *sg = blk_next_sg(sg, sglist); + sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset); + return 1; +} + +/* only try to merge bvecs into one sg if they are from two bios */ +static inline bool +__blk_segment_map_sg_merge(struct request_queue *q, struct bio_vec *bvec, + struct bio_vec *bvprv, struct scatterlist **sg) +{ + + int nbytes = bvec->bv_len; + + if (!*sg) + return false; + + if ((*sg)->length + nbytes > queue_max_segment_size(q)) + return false; + + if (!biovec_phys_mergeable(q, bvprv, bvec)) + return false; + + (*sg)->length += nbytes; + + return true; +} + +static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, + struct scatterlist *sglist, + struct scatterlist **sg) +{ + struct bio_vec bvec, bvprv = { NULL }; + struct bvec_iter iter; + int nsegs = 0; + bool new_bio = false; + + for_each_bio(bio) { + bio_for_each_bvec(bvec, bio, iter) { + /* + * Only try to merge bvecs from two bios given we + * have done bio internal merge when adding pages + * to bio + */ + if (new_bio && + __blk_segment_map_sg_merge(q, &bvec, &bvprv, sg)) + goto next_bvec; + + if (bvec.bv_offset + bvec.bv_len <= PAGE_SIZE) + nsegs += __blk_bvec_map_sg(bvec, sglist, sg); + else + nsegs += blk_bvec_map_sg(q, &bvec, sglist, sg); + next_bvec: + new_bio = false; + } + if (likely(bio->bi_iter.bi_size)) { + bvprv = bvec; + new_bio = true; + } + } + + return nsegs; +} + +/* + * map a request to scatterlist, return number of sg entries setup. Caller + * must make sure sg can hold rq->nr_phys_segments entries + */ +int __blk_rq_map_sg(struct request_queue *q, struct request *rq, + struct scatterlist *sglist, struct scatterlist **last_sg) +{ + int nsegs = 0; + + if (rq->rq_flags & RQF_SPECIAL_PAYLOAD) + nsegs = __blk_bvec_map_sg(rq->special_vec, sglist, last_sg); + else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME) + nsegs = __blk_bvec_map_sg(bio_iovec(rq->bio), sglist, last_sg); + else if (rq->bio) + nsegs = __blk_bios_map_sg(q, rq->bio, sglist, last_sg); + + if (*last_sg) + sg_mark_end(*last_sg); + + /* + * Something must have been wrong if the figured number of + * segment is bigger than number of req's physical segments + */ + WARN_ON(nsegs > blk_rq_nr_phys_segments(rq)); + + return nsegs; +} +EXPORT_SYMBOL(__blk_rq_map_sg); + +static inline unsigned int blk_rq_get_max_segments(struct request *rq) +{ + if (req_op(rq) == REQ_OP_DISCARD) + return queue_max_discard_segments(rq->q); + return queue_max_segments(rq->q); +} + +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 (blk_integrity_merge_bio(req->q, req, bio) == false) + 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; + 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 (blk_integrity_merge_rq(q, req, next) == false) + return 0; + + if (!bio_crypt_ctx_merge_rq(req, next)) + return 0; + + /* Merge is OK... */ + req->nr_phys_segments = total_phys_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. + */ +void blk_rq_set_mixed_merge(struct request *rq) +{ + unsigned int 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 void blk_account_io_merge_request(struct request *req) +{ + if (blk_do_io_stat(req)) { + part_stat_lock(); + part_stat_inc(req->part, merges[op_stat_group(req_op(req))]); + part_stat_unlock(); + + hd_struct_put(req->part); + } +} + +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; +} + +/* + * 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 (rq_data_dir(req) != rq_data_dir(next) + || req->rq_disk != next->rq_disk) + return NULL; + + if (req_op(req) == REQ_OP_WRITE_SAME && + !blk_write_same_mergeable(req->bio, next->bio)) + return NULL; + + /* + * Don't allow merge of different write hints, or for a hint with + * non-hint IO. + */ + if (req->write_hint != next->write_hint) + return NULL; + + if (req->ioprio != next->ioprio) + 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->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; +} + +int blk_attempt_req_merge(struct request_queue *q, struct request *rq, + struct request *next) +{ + struct request *free; + + free = attempt_merge(q, rq, next); + if (free) { + blk_put_request(free); + return 1; + } + + return 0; +} + +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; + + /* different data direction or already started, don't merge */ + if (bio_data_dir(bio) != rq_data_dir(rq)) + return false; + + /* must be same device */ + if (rq->rq_disk != bio->bi_disk) + return false; + + /* don't merge across cgroup boundaries */ + if (!blk_cgroup_mergeable(rq, bio)) + return false; + + /* only merge integrity protected bio into ditto rq */ + if (blk_integrity_merge_bio(rq->q, rq, bio) == false) + return false; + + /* Only merge if the crypt contexts are compatible */ + if (!bio_crypt_rq_ctx_compatible(rq, bio)) + return false; + + /* must be using the same buffer */ + if (req_op(rq) == REQ_OP_WRITE_SAME && + !blk_write_same_mergeable(rq->bio, bio)) + return false; + + /* + * Don't allow merge of different write hints, or for a hint with + * non-hint IO. + */ + if (rq->write_hint != bio->bi_write_hint) + return false; + + if (rq->ioprio != bio_prio(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 (!blk_do_io_stat(req)) + return; + + part_stat_lock(); + part_stat_inc(req->part, merges[op_stat_group(req_op(req))]); + part_stat_unlock(); +} + +enum bio_merge_status { + BIO_MERGE_OK, + BIO_MERGE_NONE, + BIO_MERGE_FAILED, +}; + +static enum bio_merge_status bio_attempt_back_merge(struct request *req, + struct bio *bio, unsigned int nr_segs) +{ + const int ff = bio->bi_opf & REQ_FAILFAST_MASK; + + if (!ll_back_merge_fn(req, bio, nr_segs)) + return BIO_MERGE_FAILED; + + trace_block_bio_backmerge(req->q, req, bio); + rq_qos_merge(req->q, req, bio); + + if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) + blk_rq_set_mixed_merge(req); + + 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 int ff = bio->bi_opf & REQ_FAILFAST_MASK; + + if (!ll_front_merge_fn(req, bio, nr_segs)) + return BIO_MERGE_FAILED; + + trace_block_bio_frontmerge(req->q, req, bio); + rq_qos_merge(req->q, req, bio); + + if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) + blk_rq_set_mixed_merge(req); + + 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 + * @same_queue_rq: pointer to &struct request that gets filled in when + * another request associated with @q is found on the plug list + * (optional, may be %NULL) + * + * Determine whether @bio being queued on @q can be merged with a 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 request **same_queue_rq) +{ + struct blk_plug *plug; + struct request *rq; + struct list_head *plug_list; + + plug = blk_mq_plug(q, bio); + if (!plug) + return false; + + plug_list = &plug->mq_list; + + list_for_each_entry_reverse(rq, plug_list, queuelist) { + if (rq->q == q && same_queue_rq) { + /* + * Only blk-mq multiple hardware queues case checks the + * rq in the same queue, there should be only one such + * rq in a queue + **/ + *same_queue_rq = rq; + } + + if (rq->q != q) + continue; + + if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) == + BIO_MERGE_OK) + return true; + } + + 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); |