--- /dev/null
+/*
+ * 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 "blk.h"
+
+static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
+ struct bio *bio,
+ bool no_sg_merge)
+{
+ struct bio_vec bv, bvprv = { NULL };
+ int cluster, high, highprv = 1;
+ unsigned int seg_size, nr_phys_segs;
+ struct bio *fbio, *bbio;
+ struct bvec_iter iter;
+
+ if (!bio)
+ return 0;
+
+ /*
+ * This should probably be returning 0, but blk_add_request_payload()
+ * (Christoph!!!!)
+ */
+ if (bio->bi_rw & REQ_DISCARD)
+ return 1;
+
+ if (bio->bi_rw & REQ_WRITE_SAME)
+ return 1;
+
+ fbio = bio;
+ cluster = blk_queue_cluster(q);
+ seg_size = 0;
+ nr_phys_segs = 0;
+ high = 0;
+ for_each_bio(bio) {
+ bio_for_each_segment(bv, bio, iter) {
+ /*
+ * If SG merging is disabled, each bio vector is
+ * a segment
+ */
+ if (no_sg_merge)
+ goto new_segment;
+
+ /*
+ * the trick here is making sure that a high page is
+ * never considered part of another segment, since
+ * that might change with the bounce page.
+ */
+ high = page_to_pfn(bv.bv_page) > queue_bounce_pfn(q);
+ if (!high && !highprv && cluster) {
+ if (seg_size + bv.bv_len
+ > queue_max_segment_size(q))
+ goto new_segment;
+ if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv))
+ goto new_segment;
+ if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv))
+ goto new_segment;
+
+ seg_size += bv.bv_len;
+ bvprv = bv;
+ continue;
+ }
+new_segment:
+ if (nr_phys_segs == 1 && seg_size >
+ fbio->bi_seg_front_size)
+ fbio->bi_seg_front_size = seg_size;
+
+ nr_phys_segs++;
+ bvprv = bv;
+ seg_size = bv.bv_len;
+ highprv = high;
+ }
+ bbio = bio;
+ }
+
+ if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
+ fbio->bi_seg_front_size = seg_size;
+ if (seg_size > bbio->bi_seg_back_size)
+ bbio->bi_seg_back_size = seg_size;
+
+ return nr_phys_segs;
+}
+
+void blk_recalc_rq_segments(struct request *rq)
+{
+ bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE,
+ &rq->q->queue_flags);
+
+ rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio,
+ no_sg_merge);
+}
+
+void blk_recount_segments(struct request_queue *q, struct bio *bio)
+{
+ unsigned short seg_cnt;
+
+ /* estimate segment number by bi_vcnt for non-cloned bio */
+ if (bio_flagged(bio, BIO_CLONED))
+ seg_cnt = bio_segments(bio);
+ else
+ seg_cnt = bio->bi_vcnt;
+
+ if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) &&
+ (seg_cnt < queue_max_segments(q)))
+ bio->bi_phys_segments = seg_cnt;
+ else {
+ struct bio *nxt = bio->bi_next;
+
+ bio->bi_next = NULL;
+ bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false);
+ bio->bi_next = nxt;
+ }
+
+ bio->bi_flags |= (1 << BIO_SEG_VALID);
+}
+EXPORT_SYMBOL(blk_recount_segments);
+
+static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
+ struct bio *nxt)
+{
+ struct bio_vec end_bv = { NULL }, nxt_bv;
+ struct bvec_iter iter;
+
+ if (!blk_queue_cluster(q))
+ return 0;
+
+ if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
+ queue_max_segment_size(q))
+ return 0;
+
+ if (!bio_has_data(bio))
+ return 1;
+
+ bio_for_each_segment(end_bv, bio, iter)
+ if (end_bv.bv_len == iter.bi_size)
+ break;
+
+ nxt_bv = bio_iovec(nxt);
+
+ if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv))
+ return 0;
+
+ /*
+ * bio and nxt are contiguous in memory; check if the queue allows
+ * these two to be merged into one
+ */
+ if (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv))
+ return 1;
+
+ return 0;
+}
+
+static inline void
+__blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
+ struct scatterlist *sglist, struct bio_vec *bvprv,
+ struct scatterlist **sg, int *nsegs, int *cluster)
+{
+
+ int nbytes = bvec->bv_len;
+
+ if (*sg && *cluster) {
+ if ((*sg)->length + nbytes > queue_max_segment_size(q))
+ goto new_segment;
+
+ if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
+ goto new_segment;
+ if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
+ goto new_segment;
+
+ (*sg)->length += nbytes;
+ } else {
+new_segment:
+ if (!*sg)
+ *sg = sglist;
+ else {
+ /*
+ * 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);
+ *sg = sg_next(*sg);
+ }
+
+ sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
+ (*nsegs)++;
+ }
+ *bvprv = *bvec;
+}
+
+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, cluster;
+
+ nsegs = 0;
+ cluster = blk_queue_cluster(q);
+
+ if (bio->bi_rw & REQ_DISCARD) {
+ /*
+ * This is a hack - drivers should be neither modifying the
+ * biovec, nor relying on bi_vcnt - but because of
+ * blk_add_request_payload(), a discard bio may or may not have
+ * a payload we need to set up here (thank you Christoph) and
+ * bi_vcnt is really the only way of telling if we need to.
+ */
+
+ if (bio->bi_vcnt)
+ goto single_segment;
+
+ return 0;
+ }
+
+ if (bio->bi_rw & REQ_WRITE_SAME) {
+single_segment:
+ *sg = sglist;
+ bvec = bio_iovec(bio);
+ sg_set_page(*sg, bvec.bv_page, bvec.bv_len, bvec.bv_offset);
+ return 1;
+ }
+
+ for_each_bio(bio)
+ bio_for_each_segment(bvec, bio, iter)
+ __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg,
+ &nsegs, &cluster);
+
+ 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 *sg = NULL;
+ int nsegs = 0;
+
+ if (rq->bio)
+ nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);
+
+ if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
+ (blk_rq_bytes(rq) & q->dma_pad_mask)) {
+ unsigned int pad_len =
+ (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
+
+ sg->length += pad_len;
+ rq->extra_len += pad_len;
+ }
+
+ if (q->dma_drain_size && q->dma_drain_needed(rq)) {
+ if (rq->cmd_flags & REQ_WRITE)
+ memset(q->dma_drain_buffer, 0, q->dma_drain_size);
+
+ sg->page_link &= ~0x02;
+ sg = sg_next(sg);
+ sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
+ q->dma_drain_size,
+ ((unsigned long)q->dma_drain_buffer) &
+ (PAGE_SIZE - 1));
+ nsegs++;
+ rq->extra_len += q->dma_drain_size;
+ }
+
+ if (sg)
+ sg_mark_end(sg);
+
+ return nsegs;
+}
+EXPORT_SYMBOL(blk_rq_map_sg);
+
+static inline int ll_new_hw_segment(struct request_queue *q,
+ struct request *req,
+ struct bio *bio)
+{
+ int nr_phys_segs = bio_phys_segments(q, bio);
+
+ if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
+ goto no_merge;
+
+ if (blk_integrity_merge_bio(q, req, bio) == false)
+ 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->cmd_flags |= REQ_NOMERGE;
+ if (req == q->last_merge)
+ q->last_merge = NULL;
+ return 0;
+}
+
+int ll_back_merge_fn(struct request_queue *q, struct request *req,
+ struct bio *bio)
+{
+ if (blk_rq_sectors(req) + bio_sectors(bio) >
+ blk_rq_get_max_sectors(req)) {
+ req->cmd_flags |= REQ_NOMERGE;
+ if (req == q->last_merge)
+ q->last_merge = NULL;
+ return 0;
+ }
+ if (!bio_flagged(req->biotail, BIO_SEG_VALID))
+ blk_recount_segments(q, req->biotail);
+ if (!bio_flagged(bio, BIO_SEG_VALID))
+ blk_recount_segments(q, bio);
+
+ return ll_new_hw_segment(q, req, bio);
+}
+
+int ll_front_merge_fn(struct request_queue *q, struct request *req,
+ struct bio *bio)
+{
+ if (blk_rq_sectors(req) + bio_sectors(bio) >
+ blk_rq_get_max_sectors(req)) {
+ req->cmd_flags |= REQ_NOMERGE;
+ if (req == q->last_merge)
+ q->last_merge = NULL;
+ return 0;
+ }
+ if (!bio_flagged(bio, BIO_SEG_VALID))
+ blk_recount_segments(q, bio);
+ if (!bio_flagged(req->bio, BIO_SEG_VALID))
+ blk_recount_segments(q, req->bio);
+
+ return ll_new_hw_segment(q, req, bio);
+}
+
+/*
+ * blk-mq uses req->special to carry normal driver per-request payload, it
+ * does not indicate a prepared command that we cannot merge with.
+ */
+static bool req_no_special_merge(struct request *req)
+{
+ struct request_queue *q = req->q;
+
+ return !q->mq_ops && req->special;
+}
+
+static int req_gap_to_prev(struct request *req, struct request *next)
+{
+ struct bio *prev = req->biotail;
+
+ return bvec_gap_to_prev(&prev->bi_io_vec[prev->bi_vcnt - 1],
+ next->bio->bi_io_vec[0].bv_offset);
+}
+
+static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
+ struct request *next)
+{
+ int total_phys_segments;
+ unsigned int seg_size =
+ req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
+
+ /*
+ * First check if the either of the requests are re-queued
+ * requests. Can't merge them if they are.
+ */
+ if (req_no_special_merge(req) || req_no_special_merge(next))
+ return 0;
+
+ if (test_bit(QUEUE_FLAG_SG_GAPS, &q->queue_flags) &&
+ req_gap_to_prev(req, next))
+ return 0;
+
+ /*
+ * Will it become too large?
+ */
+ if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
+ blk_rq_get_max_sectors(req))
+ return 0;
+
+ total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
+ if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
+ if (req->nr_phys_segments == 1)
+ req->bio->bi_seg_front_size = seg_size;
+ if (next->nr_phys_segments == 1)
+ next->biotail->bi_seg_back_size = seg_size;
+ total_phys_segments--;
+ }
+
+ if (total_phys_segments > queue_max_segments(q))
+ return 0;
+
+ if (blk_integrity_merge_rq(q, req, next) == false)
+ 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->cmd_flags & REQ_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_rw & REQ_FAILFAST_MASK) &&
+ (bio->bi_rw & REQ_FAILFAST_MASK) != ff);
+ bio->bi_rw |= ff;
+ }
+ rq->cmd_flags |= REQ_MIXED_MERGE;
+}
+
+static void blk_account_io_merge(struct request *req)
+{
+ if (blk_do_io_stat(req)) {
+ struct hd_struct *part;
+ int cpu;
+
+ cpu = part_stat_lock();
+ part = req->part;
+
+ part_round_stats(cpu, part);
+ part_dec_in_flight(part, rq_data_dir(req));
+
+ hd_struct_put(part);
+ part_stat_unlock();
+ }
+}
+
+/*
+ * Has to be called with the request spinlock acquired
+ */
+static int attempt_merge(struct request_queue *q, struct request *req,
+ struct request *next)
+{
+ if (!rq_mergeable(req) || !rq_mergeable(next))
+ return 0;
+
+ if (!blk_check_merge_flags(req->cmd_flags, next->cmd_flags))
+ return 0;
+
+ /*
+ * not contiguous
+ */
+ if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
+ return 0;
+
+ if (rq_data_dir(req) != rq_data_dir(next)
+ || req->rq_disk != next->rq_disk
+ || req_no_special_merge(next))
+ return 0;
+
+ if (req->cmd_flags & REQ_WRITE_SAME &&
+ !blk_write_same_mergeable(req->bio, next->bio))
+ return 0;
+
+ /*
+ * 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.
+ */
+ if (!ll_merge_requests_fn(q, req, next))
+ return 0;
+
+ /*
+ * 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->cmd_flags | next->cmd_flags) & REQ_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 of
+ * the merged requests to be the current request
+ * for accounting purposes.
+ */
+ if (time_after(req->start_time, next->start_time))
+ req->start_time = next->start_time;
+
+ req->biotail->bi_next = next->bio;
+ req->biotail = next->biotail;
+
+ req->__data_len += blk_rq_bytes(next);
+
+ elv_merge_requests(q, req, next);
+
+ /*
+ * 'next' is going away, so update stats accordingly
+ */
+ blk_account_io_merge(next);
+
+ req->ioprio = ioprio_best(req->ioprio, next->ioprio);
+ if (blk_rq_cpu_valid(next))
+ req->cpu = next->cpu;
+
+ /* owner-ship of bio passed from next to req */
+ next->bio = NULL;
+ __blk_put_request(q, next);
+ return 1;
+}
+
+int 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 0;
+}
+
+int 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 0;
+}
+
+int 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)
+{
+ struct request_queue *q = rq->q;
+
+ if (!rq_mergeable(rq) || !bio_mergeable(bio))
+ return false;
+
+ if (!blk_check_merge_flags(rq->cmd_flags, bio->bi_rw))
+ 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 and not a special request */
+ if (rq->rq_disk != bio->bi_bdev->bd_disk || req_no_special_merge(rq))
+ return false;
+
+ /* only merge integrity protected bio into ditto rq */
+ if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
+ return false;
+
+ /* must be using the same buffer */
+ if (rq->cmd_flags & REQ_WRITE_SAME &&
+ !blk_write_same_mergeable(rq->bio, bio))
+ return false;
+
+ if (q->queue_flags & (1 << QUEUE_FLAG_SG_GAPS)) {
+ struct bio_vec *bprev;
+
+ bprev = &rq->biotail->bi_io_vec[rq->biotail->bi_vcnt - 1];
+ if (bvec_gap_to_prev(bprev, bio->bi_io_vec[0].bv_offset))
+ return false;
+ }
+
+ return true;
+}
+
+int blk_try_merge(struct request *rq, struct bio *bio)
+{
+ 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;
+}
Code Review / kvmfornfv.git / blobdiff