| // 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/scatterlist.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_bvec_done) |
| idx = iter.bi_idx - 1; |
| else /* in the middle of bvec */ |
| idx = iter.bi_idx; |
| |
| *bv = bio->bi_io_vec[idx]; |
| |
| /* |
| * iter.bi_bvec_done records actual length of the last bvec |
| * if this bio ends in the middle of one io vector |
| */ |
| if (iter.bi_bvec_done) |
| bv->bv_len = iter.bi_bvec_done; |
| } |
| |
| 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 max size one bio can handle is UINT_MAX becasue bvec_iter.bi_size |
| * is defined as 'unsigned int', meantime it has to be aligned to with 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(UINT_MAX, lim->logical_block_size) >> SECTOR_SHIFT; |
| } |
| |
| static struct bio *bio_split_discard(struct bio *bio, |
| const struct queue_limits *lim, |
| unsigned *nsegs, struct bio_set *bs) |
| { |
| 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(lim->max_discard_sectors, bio_allowed_max_sectors(lim)); |
| max_discard_sectors -= max_discard_sectors % granularity; |
| if (unlikely(!max_discard_sectors)) |
| 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. |
| */ |
| 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_split(bio, split_sectors, GFP_NOIO, bs); |
| } |
| |
| static struct bio *bio_split_write_zeroes(struct bio *bio, |
| const struct queue_limits *lim, |
| unsigned *nsegs, struct bio_set *bs) |
| { |
| *nsegs = 0; |
| if (!lim->max_write_zeroes_sectors) |
| return NULL; |
| if (bio_sectors(bio) <= lim->max_write_zeroes_sectors) |
| return NULL; |
| return bio_split(bio, lim->max_write_zeroes_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 bio *bio, |
| const struct queue_limits *lim) |
| { |
| unsigned pbs = lim->physical_block_size >> SECTOR_SHIFT; |
| unsigned lbs = lim->logical_block_size >> SECTOR_SHIFT; |
| unsigned max_sectors = lim->max_sectors, start, end; |
| |
| if (lim->chunk_sectors) { |
| max_sectors = min(max_sectors, |
| blk_chunk_sectors_left(bio->bi_iter.bi_sector, |
| lim->chunk_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); |
| } |
| |
| /** |
| * get_max_segment_size() - maximum number of bytes to add as a single segment |
| * @lim: Request queue limits. |
| * @start_page: See below. |
| * @offset: Offset from @start_page where to add a segment. |
| * |
| * Returns the maximum number of bytes that can be added as a single segment. |
| */ |
| static inline unsigned get_max_segment_size(const struct queue_limits *lim, |
| struct page *start_page, unsigned long offset) |
| { |
| unsigned long mask = lim->seg_boundary_mask; |
| |
| offset = mask & (page_to_phys(start_page) + offset); |
| |
| /* |
| * Prevent an overflow if mask = ULONG_MAX and offset = 0 by adding 1 |
| * after having calculated the minimum. |
| */ |
| return min(mask - offset, (unsigned long)lim->max_segment_size - 1) + 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 = min(max_bytes, UINT_MAX) - *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, 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) & 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; |
| } |
| |
| /** |
| * bio_split_rw - split a bio in two bios |
| * @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 |
| * @bs: [in] bio set to allocate the clone from |
| * @max_bytes: [in] maximum number of bytes per bio |
| * |
| * 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 @max_bytes worth of data |
| * - 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. |
| */ |
| struct bio *bio_split_rw(struct bio *bio, const struct queue_limits *lim, |
| unsigned *segs, struct bio_set *bs, unsigned max_bytes) |
| { |
| struct bio_vec bv, bvprv, *bvprvp = NULL; |
| struct bvec_iter iter; |
| unsigned nsegs = 0, bytes = 0; |
| |
| 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(lim, bvprvp, bv.bv_offset)) |
| goto split; |
| |
| if (nsegs < lim->max_segments && |
| bytes + bv.bv_len <= max_bytes && |
| bv.bv_offset + bv.bv_len <= PAGE_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; |
| return NULL; |
| split: |
| /* |
| * 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) { |
| bio->bi_status = BLK_STS_AGAIN; |
| bio_endio(bio); |
| return ERR_PTR(-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. |
| */ |
| bytes = ALIGN_DOWN(bytes, lim->logical_block_size); |
| |
| /* |
| * 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); |
| return bio_split(bio, bytes >> SECTOR_SHIFT, GFP_NOIO, bs); |
| } |
| EXPORT_SYMBOL_GPL(bio_split_rw); |
| |
| /** |
| * __bio_split_to_limits - split a bio to fit the queue limits |
| * @bio: bio to be split |
| * @lim: queue limits to split based on |
| * @nr_segs: returns the number of segments in the returned bio |
| * |
| * Check if @bio needs splitting based on the queue limits, 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, |
| const struct queue_limits *lim, |
| unsigned int *nr_segs) |
| { |
| struct bio_set *bs = &bio->bi_bdev->bd_disk->bio_split; |
| struct bio *split; |
| |
| switch (bio_op(bio)) { |
| case REQ_OP_DISCARD: |
| case REQ_OP_SECURE_ERASE: |
| split = bio_split_discard(bio, lim, nr_segs, bs); |
| break; |
| case REQ_OP_WRITE_ZEROES: |
| split = bio_split_write_zeroes(bio, lim, nr_segs, bs); |
| break; |
| default: |
| split = bio_split_rw(bio, lim, nr_segs, bs, |
| get_max_io_size(bio, lim) << SECTOR_SHIFT); |
| if (IS_ERR(split)) |
| return NULL; |
| break; |
| } |
| |
| if (split) { |
| /* there isn't chance to merge the split bio */ |
| split->bi_opf |= REQ_NOMERGE; |
| |
| blkcg_bio_issue_init(split); |
| bio_chain(split, bio); |
| trace_block_split(split, bio->bi_iter.bi_sector); |
| submit_bio_noacct(bio); |
| return split; |
| } |
| return bio; |
| } |
| |
| /** |
| * 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) |
| { |
| const struct queue_limits *lim = &bdev_get_queue(bio->bi_bdev)->limits; |
| unsigned int nr_segs; |
| |
| if (bio_may_exceed_limits(bio, lim)) |
| return __bio_split_to_limits(bio, lim, &nr_segs); |
| return bio; |
| } |
| 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, 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->limits, |
| 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) |
| 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_sectors(struct request *rq, |
| sector_t offset) |
| { |
| struct request_queue *q = rq->q; |
| unsigned int max_sectors; |
| |
| if (blk_rq_is_passthrough(rq)) |
| return q->limits.max_hw_sectors; |
| |
| max_sectors = blk_queue_get_max_sectors(q, req_op(rq)); |
| if (!q->limits.chunk_sectors || |
| req_op(rq) == REQ_OP_DISCARD || |
| req_op(rq) == REQ_OP_SECURE_ERASE) |
| return max_sectors; |
| return min(max_sectors, |
| blk_chunk_sectors_left(offset, q->limits.chunk_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 (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. |
| */ |
| 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 (blk_do_io_stat(req)) { |
| part_stat_lock(); |
| part_stat_inc(req->part, merges[op_stat_group(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; |
| } |
| |
| /* |
| * 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)) |
| return NULL; |
| |
| /* Don't merge requests with different write hints. */ |
| 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; |
| } |
| |
| /* |
| * 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; |
| |
| /* different data direction or already started, don't merge */ |
| if (bio_data_dir(bio) != rq_data_dir(rq)) |
| 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; |
| |
| /* Don't merge requests with different write hints. */ |
| 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 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); |
| |
| 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); |
| |
| 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); |
| |
| 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; |
| struct request *rq; |
| |
| plug = blk_mq_plug(bio); |
| if (!plug || rq_list_empty(plug->mq_list)) |
| return false; |
| |
| rq_list_for_each(&plug->mq_list, rq) { |
| if (rq->q == q) { |
| if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) == |
| BIO_MERGE_OK) |
| return true; |
| break; |
| } |
| |
| /* |
| * Only keep iterating plug list for merges if we have multiple |
| * queues |
| */ |
| if (!plug->multiple_queues) |
| 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); |