block: remove the bi_phys_segments field in struct bio [Linux 5.3]

This Linux kernel change "block: remove the bi_phys_segments field in struct bio" is included in the Linux 5.3 release. This change is authored by Christoph Hellwig <hch [at] lst.de> on Thu Jun 6 12:29:01 2019 +0200. The commit for this change in Linux stable tree is 14ccb66 (patch).

block: remove the bi_phys_segments field in struct bio

We only need the number of segments in the blk-mq submission path.
Remove the field from struct bio, and return it from a variant of
blk_queue_split instead of that it can passed as an argument to
those functions that need the value.

This also means we stop recounting segments except for cloning
and partial segments.

To keep the number of arguments in this how path down remove
pointless struct request_queue arguments from any of the functions
that had it and grew a nr_segs argument.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

There are 243 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 Documentation/block/biodoc.txt |  1 -
 block/bfq-iosched.c            |  5 +--
 block/bio.c                    | 15 +--------
 block/blk-core.c               | 32 ++++++++----------
 block/blk-map.c                | 10 ++++--
 block/blk-merge.c              | 75 +++++++++++++++---------------------------
 block/blk-mq-sched.c           | 26 ++++++++-------
 block/blk-mq-sched.h           | 10 +++---
 block/blk-mq.c                 | 23 ++++++-------
 block/blk.h                    | 23 ++++++-------
 block/kyber-iosched.c          |  5 +--
 block/mq-deadline.c            |  5 +--
 drivers/md/raid5.c             |  1 -
 include/linux/bio.h            |  1 -
 include/linux/blk-mq.h         |  2 +-
 include/linux/blk_types.h      |  6 ----
 include/linux/blkdev.h         |  1 -
 include/linux/elevator.h       |  2 +-
 18 files changed, 106 insertions(+), 137 deletions(-)

diff --git a/Documentation/block/biodoc.txt b/Documentation/block/biodoc.txt
index ac18b48..31c17766 100644
--- a/Documentation/block/biodoc.txt
+++ b/Documentation/block/biodoc.txt
@@ -436,7 +436,6 @@ struct bio {
        struct bvec_iter    bi_iter;    /* current index into bio_vec array */

        unsigned int    bi_size;     /* total size in bytes */
-       unsigned short  bi_phys_segments; /* segments after physaddr coalesce*/
        unsigned short  bi_hw_segments; /* segments after DMA remapping */
        unsigned int    bi_max;      /* max bio_vecs we can hold
                                         used as index into pool */
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index f8d430f..a6bf842 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -2027,7 +2027,8 @@ static void bfq_remove_request(struct request_queue *q,

 }

-static bool bfq_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio)
+static bool bfq_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio,
+       unsigned int nr_segs)
 {
    struct request_queue *q = hctx->queue;
    struct bfq_data *bfqd = q->elevator->elevator_data;
@@ -2050,7 +2051,7 @@ static bool bfq_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio)
        bfqd->bio_bfqq = NULL;
    bfqd->bio_bic = bic;

-   ret = blk_mq_sched_try_merge(q, bio, &free);
+   ret = blk_mq_sched_try_merge(q, bio, nr_segs, &free);

    if (free)
        blk_mq_free_request(free);
diff --git a/block/bio.c b/block/bio.c
index 4bcdcd3..ad9c3aa 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -558,14 +558,6 @@ void bio_put(struct bio *bio)
 }
 EXPORT_SYMBOL(bio_put);

-int bio_phys_segments(struct request_queue *q, struct bio *bio)
-{
-   if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
-       blk_recount_segments(q, bio);
-
-   return bio->bi_phys_segments;
-}
-
 /**
  *     __bio_clone_fast - clone a bio that shares the original bio's biovec
  *     @bio: destination bio
@@ -739,7 +731,7 @@ static int __bio_add_pc_page(struct request_queue *q, struct bio *bio,
    if (bio_full(bio))
        return 0;

-   if (bio->bi_phys_segments >= queue_max_segments(q))
+   if (bio->bi_vcnt >= queue_max_segments(q))
        return 0;

    bvec = &bio->bi_io_vec[bio->bi_vcnt];
@@ -749,8 +741,6 @@ static int __bio_add_pc_page(struct request_queue *q, struct bio *bio,
    bio->bi_vcnt++;
  done:
    bio->bi_iter.bi_size += len;
-   bio->bi_phys_segments = bio->bi_vcnt;
-   bio_set_flag(bio, BIO_SEG_VALID);
    return len;
 }

@@ -1909,10 +1899,7 @@ void bio_trim(struct bio *bio, int offset, int size)
    if (offset == 0 && size == bio->bi_iter.bi_size)
        return;

-   bio_clear_flag(bio, BIO_SEG_VALID);
-
    bio_advance(bio, offset << 9);
-
    bio->bi_iter.bi_size = size;

    if (bio_integrity(bio))
diff --git a/block/blk-core.c b/block/blk-core.c
index d1c7c69a..ef998a7 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -550,15 +550,15 @@ void blk_put_request(struct request *req)
 }
 EXPORT_SYMBOL(blk_put_request);

-bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
-               struct bio *bio)
+bool 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(q, req, bio))
+   if (!ll_back_merge_fn(req, bio, nr_segs))
        return false;

-   trace_block_bio_backmerge(q, req, bio);
+   trace_block_bio_backmerge(req->q, req, bio);

    if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
        blk_rq_set_mixed_merge(req);
@@ -571,15 +571,15 @@ bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
    return true;
 }

-bool bio_attempt_front_merge(struct request_queue *q, struct request *req,
-                struct bio *bio)
+bool 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(q, req, bio))
+   if (!ll_front_merge_fn(req, bio, nr_segs))
        return false;

-   trace_block_bio_frontmerge(q, req, bio);
+   trace_block_bio_frontmerge(req->q, req, bio);

    if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
        blk_rq_set_mixed_merge(req);
@@ -621,6 +621,7 @@ bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
  * 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)
@@ -639,7 +640,7 @@ bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
  * Caller must ensure !blk_queue_nomerges(q) beforehand.
  */
 bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
-               struct request **same_queue_rq)
+       unsigned int nr_segs, struct request **same_queue_rq)
 {
    struct blk_plug *plug;
    struct request *rq;
@@ -668,10 +669,10 @@ bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,

        switch (blk_try_merge(rq, bio)) {
        case ELEVATOR_BACK_MERGE:
-           merged = bio_attempt_back_merge(q, rq, bio);
+           merged = bio_attempt_back_merge(rq, bio, nr_segs);
            break;
        case ELEVATOR_FRONT_MERGE:
-           merged = bio_attempt_front_merge(q, rq, bio);
+           merged = bio_attempt_front_merge(rq, bio, nr_segs);
            break;
        case ELEVATOR_DISCARD_MERGE:
            merged = bio_attempt_discard_merge(q, rq, bio);
@@ -1427,14 +1428,9 @@ bool blk_update_request(struct request *req, blk_status_t error,
 }
 EXPORT_SYMBOL_GPL(blk_update_request);

-void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
-            struct bio *bio)
+void blk_rq_bio_prep(struct request *rq, struct bio *bio, unsigned int nr_segs)
 {
-   if (bio_has_data(bio))
-       rq->nr_phys_segments = bio_phys_segments(q, bio);
-   else if (bio_op(bio) == REQ_OP_DISCARD)
-       rq->nr_phys_segments = 1;
-
+   rq->nr_phys_segments = nr_segs;
    rq->__data_len = bio->bi_iter.bi_size;
    rq->bio = rq->biotail = bio;
    rq->ioprio = bio_prio(bio);
diff --git a/block/blk-map.c b/block/blk-map.c
index db9373b..3a62e47 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -18,13 +18,19 @@
 int blk_rq_append_bio(struct request *rq, struct bio **bio)
 {
    struct bio *orig_bio = *bio;
+   struct bvec_iter iter;
+   struct bio_vec bv;
+   unsigned int nr_segs = 0;

    blk_queue_bounce(rq->q, bio);

+   bio_for_each_bvec(bv, *bio, iter)
+       nr_segs++;
+
    if (!rq->bio) {
-       blk_rq_bio_prep(rq->q, rq, *bio);
+       blk_rq_bio_prep(rq, *bio, nr_segs);
    } else {
-       if (!ll_back_merge_fn(rq->q, rq, *bio)) {
+       if (!ll_back_merge_fn(rq, *bio, nr_segs)) {
            if (orig_bio != *bio) {
                bio_put(*bio);
                *bio = orig_bio;
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 17713d7..72b4fd8 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -258,32 +258,29 @@ static struct bio *blk_bio_segment_split(struct request_queue *q,
    return do_split ? new : NULL;
 }

-void blk_queue_split(struct request_queue *q, struct bio **bio)
+void __blk_queue_split(struct request_queue *q, struct bio **bio,
+       unsigned int *nr_segs)
 {
-   struct bio *split, *res;
-   unsigned nsegs;
+   struct bio *split;

    switch (bio_op(*bio)) {
    case REQ_OP_DISCARD:
    case REQ_OP_SECURE_ERASE:
-       split = blk_bio_discard_split(q, *bio, &q->bio_split, &nsegs);
+       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, &nsegs);
+       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, &nsegs);
+       split = blk_bio_write_same_split(q, *bio, &q->bio_split,
+               nr_segs);
        break;
    default:
-       split = blk_bio_segment_split(q, *bio, &q->bio_split, &nsegs);
+       split = blk_bio_segment_split(q, *bio, &q->bio_split, nr_segs);
        break;
    }

-   /* physical segments can be figured out during splitting */
-   res = split ? split : *bio;
-   res->bi_phys_segments = nsegs;
-   bio_set_flag(res, BIO_SEG_VALID);
-
    if (split) {
        /* there isn't chance to merge the splitted bio */
        split->bi_opf |= REQ_NOMERGE;
@@ -304,6 +301,13 @@ void blk_queue_split(struct request_queue *q, struct bio **bio)
        *bio = split;
    }
 }
+
+void blk_queue_split(struct request_queue *q, struct bio **bio)
+{
+   unsigned int nr_segs;
+
+   __blk_queue_split(q, bio, &nr_segs);
+}
 EXPORT_SYMBOL(blk_queue_split);

 static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
@@ -338,17 +342,6 @@ void blk_recalc_rq_segments(struct request *rq)
    rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio);
 }

-void blk_recount_segments(struct request_queue *q, struct bio *bio)
-{
-   struct bio *nxt = bio->bi_next;
-
-   bio->bi_next = NULL;
-   bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio);
-   bio->bi_next = nxt;
-
-   bio_set_flag(bio, BIO_SEG_VALID);
-}
-
 static inline struct scatterlist *blk_next_sg(struct scatterlist **sg,
        struct scatterlist *sglist)
 {
@@ -519,16 +512,13 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq,
 }
 EXPORT_SYMBOL(blk_rq_map_sg);

-static inline int ll_new_hw_segment(struct request_queue *q,
-                   struct request *req,
-                   struct bio *bio)
+static inline int ll_new_hw_segment(struct request *req, struct bio *bio,
+       unsigned int nr_phys_segs)
 {
-   int nr_phys_segs = bio_phys_segments(q, bio);
-
-   if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
+   if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(req->q))
        goto no_merge;

-   if (blk_integrity_merge_bio(q, req, bio) == false)
+   if (blk_integrity_merge_bio(req->q, req, bio) == false)
        goto no_merge;

    /*
@@ -539,12 +529,11 @@ static inline int ll_new_hw_segment(struct request_queue *q,
    return 1;

 no_merge:
-   req_set_nomerge(q, req);
+   req_set_nomerge(req->q, req);
    return 0;
 }

-int ll_back_merge_fn(struct request_queue *q, struct request *req,
-            struct bio *bio)
+int ll_back_merge_fn(struct request *req, struct bio *bio, unsigned int nr_segs)
 {
    if (req_gap_back_merge(req, bio))
        return 0;
@@ -553,21 +542,15 @@ int ll_back_merge_fn(struct request_queue *q, struct request *req,
        return 0;
    if (blk_rq_sectors(req) + bio_sectors(bio) >
        blk_rq_get_max_sectors(req, blk_rq_pos(req))) {
-       req_set_nomerge(q, req);
+       req_set_nomerge(req->q, req);
        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);
+   return ll_new_hw_segment(req, bio, nr_segs);
 }

-int ll_front_merge_fn(struct request_queue *q, struct request *req,
-             struct bio *bio)
+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) &&
@@ -575,15 +558,11 @@ int ll_front_merge_fn(struct request_queue *q, struct request *req,
        return 0;
    if (blk_rq_sectors(req) + bio_sectors(bio) >
        blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) {
-       req_set_nomerge(q, req);
+       req_set_nomerge(req->q, req);
        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);
+   return ll_new_hw_segment(req, bio, nr_segs);
 }

 static bool req_attempt_discard_merge(struct request_queue *q, struct request *req,
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 2766066..956a7aa 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -224,7 +224,7 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
 }

 bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
-               struct request **merged_request)
+       unsigned int nr_segs, struct request **merged_request)
 {
    struct request *rq;

@@ -232,7 +232,7 @@ bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
    case ELEVATOR_BACK_MERGE:
        if (!blk_mq_sched_allow_merge(q, rq, bio))
            return false;
-       if (!bio_attempt_back_merge(q, rq, bio))
+       if (!bio_attempt_back_merge(rq, bio, nr_segs))
            return false;
        *merged_request = attempt_back_merge(q, rq);
        if (!*merged_request)
@@ -241,7 +241,7 @@ bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
    case ELEVATOR_FRONT_MERGE:
        if (!blk_mq_sched_allow_merge(q, rq, bio))
            return false;
-       if (!bio_attempt_front_merge(q, rq, bio))
+       if (!bio_attempt_front_merge(rq, bio, nr_segs))
            return false;
        *merged_request = attempt_front_merge(q, rq);
        if (!*merged_request)
@@ -260,7 +260,7 @@ bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
  * of them.
  */
 bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list,
-              struct bio *bio)
+              struct bio *bio, unsigned int nr_segs)
 {
    struct request *rq;
    int checked = 8;
@@ -277,11 +277,13 @@ bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list,
        switch (blk_try_merge(rq, bio)) {
        case ELEVATOR_BACK_MERGE:
            if (blk_mq_sched_allow_merge(q, rq, bio))
-               merged = bio_attempt_back_merge(q, rq, bio);
+               merged = bio_attempt_back_merge(rq, bio,
+                       nr_segs);
            break;
        case ELEVATOR_FRONT_MERGE:
            if (blk_mq_sched_allow_merge(q, rq, bio))
-               merged = bio_attempt_front_merge(q, rq, bio);
+               merged = bio_attempt_front_merge(rq, bio,
+                       nr_segs);
            break;
        case ELEVATOR_DISCARD_MERGE:
            merged = bio_attempt_discard_merge(q, rq, bio);
@@ -304,13 +306,14 @@ bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list,
  */
 static bool blk_mq_attempt_merge(struct request_queue *q,
                 struct blk_mq_hw_ctx *hctx,
-                struct blk_mq_ctx *ctx, struct bio *bio)
+                struct blk_mq_ctx *ctx, struct bio *bio,
+                unsigned int nr_segs)
 {
    enum hctx_type type = hctx->type;

    lockdep_assert_held(&ctx->lock);

-   if (blk_mq_bio_list_merge(q, &ctx->rq_lists[type], bio)) {
+   if (blk_mq_bio_list_merge(q, &ctx->rq_lists[type], bio, nr_segs)) {
        ctx->rq_merged++;
        return true;
    }
@@ -318,7 +321,8 @@ static bool blk_mq_attempt_merge(struct request_queue *q,
    return false;
 }

-bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)
+bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio,
+       unsigned int nr_segs)
 {
    struct elevator_queue *e = q->elevator;
    struct blk_mq_ctx *ctx = blk_mq_get_ctx(q);
@@ -328,7 +332,7 @@ bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)

    if (e && e->type->ops.bio_merge) {
        blk_mq_put_ctx(ctx);
-       return e->type->ops.bio_merge(hctx, bio);
+       return e->type->ops.bio_merge(hctx, bio, nr_segs);
    }

    type = hctx->type;
@@ -336,7 +340,7 @@ bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)
            !list_empty_careful(&ctx->rq_lists[type])) {
        /* default per sw-queue merge */
        spin_lock(&ctx->lock);
-       ret = blk_mq_attempt_merge(q, hctx, ctx, bio);
+       ret = blk_mq_attempt_merge(q, hctx, ctx, bio, nr_segs);
        spin_unlock(&ctx->lock);
    }

diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h
index 3cf92cb..cf22ab0 100644
--- a/block/blk-mq-sched.h
+++ b/block/blk-mq-sched.h
@@ -12,8 +12,9 @@ void blk_mq_sched_free_hctx_data(struct request_queue *q,

 void blk_mq_sched_request_inserted(struct request *rq);
 bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
-               struct request **merged_request);
-bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio);
+       unsigned int nr_segs, struct request **merged_request);
+bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio,
+       unsigned int nr_segs);
 bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq);
 void blk_mq_sched_mark_restart_hctx(struct blk_mq_hw_ctx *hctx);
 void blk_mq_sched_restart(struct blk_mq_hw_ctx *hctx);
@@ -31,12 +32,13 @@ void blk_mq_sched_insert_requests(struct blk_mq_hw_ctx *hctx,
 void blk_mq_sched_free_requests(struct request_queue *q);

 static inline bool
-blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)
+blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio,
+       unsigned int nr_segs)
 {
    if (blk_queue_nomerges(q) || !bio_mergeable(bio))
        return false;

-   return __blk_mq_sched_bio_merge(q, bio);
+   return __blk_mq_sched_bio_merge(q, bio, nr_segs);
 }

 static inline bool
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 61457bf..d893838 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1764,14 +1764,15 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
    }
 }

-static void blk_mq_bio_to_request(struct request *rq, struct bio *bio)
+static void blk_mq_bio_to_request(struct request *rq, struct bio *bio,
+       unsigned int nr_segs)
 {
    if (bio->bi_opf & REQ_RAHEAD)
        rq->cmd_flags |= REQ_FAILFAST_MASK;

    rq->__sector = bio->bi_iter.bi_sector;
    rq->write_hint = bio->bi_write_hint;
-   blk_rq_bio_prep(rq->q, rq, bio);
+   blk_rq_bio_prep(rq, bio, nr_segs);

    blk_account_io_start(rq, true);
 }
@@ -1941,20 +1942,20 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
    struct request *rq;
    struct blk_plug *plug;
    struct request *same_queue_rq = NULL;
+   unsigned int nr_segs;
    blk_qc_t cookie;

    blk_queue_bounce(q, &bio);
-
-   blk_queue_split(q, &bio);
+   __blk_queue_split(q, &bio, &nr_segs);

    if (!bio_integrity_prep(bio))
        return BLK_QC_T_NONE;

    if (!is_flush_fua && !blk_queue_nomerges(q) &&
-       blk_attempt_plug_merge(q, bio, &same_queue_rq))
+       blk_attempt_plug_merge(q, bio, nr_segs, &same_queue_rq))
        return BLK_QC_T_NONE;

-   if (blk_mq_sched_bio_merge(q, bio))
+   if (blk_mq_sched_bio_merge(q, bio, nr_segs))
        return BLK_QC_T_NONE;

    rq_qos_throttle(q, bio);
@@ -1977,7 +1978,7 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
    plug = current->plug;
    if (unlikely(is_flush_fua)) {
        blk_mq_put_ctx(data.ctx);
-       blk_mq_bio_to_request(rq, bio);
+       blk_mq_bio_to_request(rq, bio, nr_segs);

        /* bypass scheduler for flush rq */
        blk_insert_flush(rq);
@@ -1991,7 +1992,7 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
        struct request *last = NULL;

        blk_mq_put_ctx(data.ctx);
-       blk_mq_bio_to_request(rq, bio);
+       blk_mq_bio_to_request(rq, bio, nr_segs);

        if (!request_count)
            trace_block_plug(q);
@@ -2006,7 +2007,7 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)

        blk_add_rq_to_plug(plug, rq);
    } else if (plug && !blk_queue_nomerges(q)) {
-       blk_mq_bio_to_request(rq, bio);
+       blk_mq_bio_to_request(rq, bio, nr_segs);

        /*
         * We do limited plugging. If the bio can be merged, do that.
@@ -2035,11 +2036,11 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
    } else if ((q->nr_hw_queues > 1 && is_sync) || (!q->elevator &&
            !data.hctx->dispatch_busy)) {
        blk_mq_put_ctx(data.ctx);
-       blk_mq_bio_to_request(rq, bio);
+       blk_mq_bio_to_request(rq, bio, nr_segs);
        blk_mq_try_issue_directly(data.hctx, rq, &cookie);
    } else {
        blk_mq_put_ctx(data.ctx);
-       blk_mq_bio_to_request(rq, bio);
+       blk_mq_bio_to_request(rq, bio, nr_segs);
        blk_mq_sched_insert_request(rq, false, true, true);
    }

diff --git a/block/blk.h b/block/blk.h
index 7814aa2..a1d33cb 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -51,8 +51,7 @@ struct blk_flush_queue *blk_alloc_flush_queue(struct request_queue *q,
        int node, int cmd_size, gfp_t flags);
 void blk_free_flush_queue(struct blk_flush_queue *q);

-void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
-           struct bio *bio);
+void blk_rq_bio_prep(struct request *rq, struct bio *bio, unsigned int nr_segs);
 void blk_freeze_queue(struct request_queue *q);

 static inline void blk_queue_enter_live(struct request_queue *q)
@@ -154,14 +153,14 @@ static inline bool bio_integrity_endio(struct bio *bio)
 unsigned long blk_rq_timeout(unsigned long timeout);
 void blk_add_timer(struct request *req);

-bool bio_attempt_front_merge(struct request_queue *q, struct request *req,
-                struct bio *bio);
-bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
-               struct bio *bio);
+bool bio_attempt_front_merge(struct request *req, struct bio *bio,
+       unsigned int nr_segs);
+bool bio_attempt_back_merge(struct request *req, struct bio *bio,
+       unsigned int nr_segs);
 bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
        struct bio *bio);
 bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
-               struct request **same_queue_rq);
+       unsigned int nr_segs, struct request **same_queue_rq);

 void blk_account_io_start(struct request *req, bool new_io);
 void blk_account_io_completion(struct request *req, unsigned int bytes);
@@ -202,10 +201,12 @@ static inline int blk_should_fake_timeout(struct request_queue *q)
 }
 #endif

-int ll_back_merge_fn(struct request_queue *q, struct request *req,
-            struct bio *bio);
-int ll_front_merge_fn(struct request_queue *q, struct request *req, 
-             struct bio *bio);
+void __blk_queue_split(struct request_queue *q, struct bio **bio,
+       unsigned int *nr_segs);
+int ll_back_merge_fn(struct request *req, struct bio *bio,
+       unsigned int nr_segs);
+int ll_front_merge_fn(struct request *req,  struct bio *bio,
+       unsigned int nr_segs);
 struct request *attempt_back_merge(struct request_queue *q, struct request *rq);
 struct request *attempt_front_merge(struct request_queue *q, struct request *rq);
 int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
diff --git a/block/kyber-iosched.c b/block/kyber-iosched.c
index c3b0511..3c26026 100644
--- a/block/kyber-iosched.c
+++ b/block/kyber-iosched.c
@@ -562,7 +562,8 @@ static void kyber_limit_depth(unsigned int op, struct blk_mq_alloc_data *data)
    }
 }

-static bool kyber_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio)
+static bool kyber_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio,
+       unsigned int nr_segs)
 {
    struct kyber_hctx_data *khd = hctx->sched_data;
    struct blk_mq_ctx *ctx = blk_mq_get_ctx(hctx->queue);
@@ -572,7 +573,7 @@ static bool kyber_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio)
    bool merged;

    spin_lock(&kcq->lock);
-   merged = blk_mq_bio_list_merge(hctx->queue, rq_list, bio);
+   merged = blk_mq_bio_list_merge(hctx->queue, rq_list, bio, nr_segs);
    spin_unlock(&kcq->lock);
    blk_mq_put_ctx(ctx);

diff --git a/block/mq-deadline.c b/block/mq-deadline.c
index 1876f57..b8a682b 100644
--- a/block/mq-deadline.c
+++ b/block/mq-deadline.c
@@ -469,7 +469,8 @@ static int dd_request_merge(struct request_queue *q, struct request **rq,
    return ELEVATOR_NO_MERGE;
 }

-static bool dd_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio)
+static bool dd_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio,
+       unsigned int nr_segs)
 {
    struct request_queue *q = hctx->queue;
    struct deadline_data *dd = q->elevator->elevator_data;
@@ -477,7 +478,7 @@ static bool dd_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio)
    bool ret;

    spin_lock(&dd->lock);
-   ret = blk_mq_sched_try_merge(q, bio, &free);
+   ret = blk_mq_sched_try_merge(q, bio, nr_segs, &free);
    spin_unlock(&dd->lock);

    if (free)
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index da94cba..3de4e13 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5251,7 +5251,6 @@ static int raid5_read_one_chunk(struct mddev *mddev, struct bio *raid_bio)
        rcu_read_unlock();
        raid_bio->bi_next = (void*)rdev;
        bio_set_dev(align_bi, rdev->bdev);
-       bio_clear_flag(align_bi, BIO_SEG_VALID);

        if (is_badblock(rdev, align_bi->bi_iter.bi_sector,
                bio_sectors(align_bi),
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 0f23b56..ee11c43 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -408,7 +408,6 @@ static inline void bio_wouldblock_error(struct bio *bio)
 }

 struct request_queue;
-extern int bio_phys_segments(struct request_queue *, struct bio *);

 extern int submit_bio_wait(struct bio *bio);
 extern void bio_advance(struct bio *, unsigned);
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 15d1aa5..3fa1fa5 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -306,7 +306,7 @@ static inline u16 blk_mq_unique_tag_to_tag(u32 unique_tag)
 bool blk_mq_complete_request(struct request *rq);
 void blk_mq_complete_request_sync(struct request *rq);
 bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list,
-              struct bio *bio);
+              struct bio *bio, unsigned int nr_segs);
 bool blk_mq_queue_stopped(struct request_queue *q);
 void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx);
 void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx);
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 95202f8..6a53799 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -154,11 +154,6 @@ struct bio {
    blk_status_t        bi_status;
    u8          bi_partno;

-   /* Number of segments in this BIO after
-    * physical address coalescing is performed.
-    */
-   unsigned int        bi_phys_segments;
-
    struct bvec_iter    bi_iter;

    atomic_t        __bi_remaining;
@@ -210,7 +205,6 @@ struct bio {
  */
 enum {
    BIO_NO_PAGE_REF,    /* don't put release vec pages */
-   BIO_SEG_VALID,      /* bi_phys_segments valid */
    BIO_CLONED,     /* doesn't own data */
    BIO_BOUNCED,        /* bio is a bounce bio */
    BIO_USER_MAPPED,    /* contains user pages */
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 2d4dfe8..d5d3bb4 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -841,7 +841,6 @@ extern blk_status_t blk_insert_cloned_request(struct request_queue *q,
                     struct request *rq);
 extern int blk_rq_append_bio(struct request *rq, struct bio **bio);
 extern void blk_queue_split(struct request_queue *, struct bio **);
-extern void blk_recount_segments(struct request_queue *, struct bio *);
 extern int scsi_verify_blk_ioctl(struct block_device *, unsigned int);
 extern int scsi_cmd_blk_ioctl(struct block_device *, fmode_t,
                  unsigned int, void __user *);
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index 6e8bc53..169bb2e 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -34,7 +34,7 @@ struct elevator_mq_ops {
    void (*depth_updated)(struct blk_mq_hw_ctx *);

    bool (*allow_merge)(struct request_queue *, struct request *, struct bio *);
-   bool (*bio_merge)(struct blk_mq_hw_ctx *, struct bio *);
+   bool (*bio_merge)(struct blk_mq_hw_ctx *, struct bio *, unsigned int);
    int (*request_merge)(struct request_queue *q, struct request **, struct bio *);
    void (*request_merged)(struct request_queue *, struct request *, enum elv_merge);
    void (*requests_merged)(struct request_queue *, struct request *, struct request *);

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