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- // 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>
- #ifndef __GENKSYMS__
- #include <linux/blk-cgroup.h>
- #endif
- #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);
- /*
- * 'next' is going away, so update stats accordingly
- */
- blk_account_io_merge_request(next);
- trace_block_rq_merge(q, 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);
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