block: Add a new helper to attempt to merge a bio

There are lots of duplicated code when trying to merge a bio from
plug list and sw queue, we can introduce a new helper to attempt
to merge a bio, which can simplify the blk_bio_list_merge()
and blk_attempt_plug_merge().

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-merge.c b/block/blk-merge.c
index b09e9fc4423675bb86f03576d1afddc32dd851fd..80c974484a3ff51f45e8dc21f72034786dd11481 100644 (file)
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -907,13 +907,14 @@ static void blk_account_io_merge_bio(struct request *req)
        part_stat_unlock();
 }
 
-bool bio_attempt_back_merge(struct request *req, struct bio *bio,
-               unsigned int nr_segs)
+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 false;
+               return BIO_MERGE_FAILED;
 
        trace_block_bio_backmerge(req->q, req, bio);
        rq_qos_merge(req->q, req, bio);
@@ -928,16 +929,17 @@ bool bio_attempt_back_merge(struct request *req, struct bio *bio,
        bio_crypt_free_ctx(bio);
 
        blk_account_io_merge_bio(req);
-       return true;
+       return BIO_MERGE_OK;
 }
 
-bool bio_attempt_front_merge(struct request *req, struct bio *bio,
-               unsigned int nr_segs)
+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 false;
+               return BIO_MERGE_FAILED;
 
        trace_block_bio_frontmerge(req->q, req, bio);
        rq_qos_merge(req->q, req, bio);
@@ -954,11 +956,12 @@ bool bio_attempt_front_merge(struct request *req, struct bio *bio,
        bio_crypt_do_front_merge(req, bio);
 
        blk_account_io_merge_bio(req);
-       return true;
+       return BIO_MERGE_OK;
 }
 
-bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
-               struct bio *bio)
+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);
 
@@ -976,10 +979,39 @@ bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
        req->nr_phys_segments = segments + 1;
 
        blk_account_io_merge_bio(req);
-       return true;
+       return BIO_MERGE_OK;
 no_merge:
        req_set_nomerge(q, req);
-       return false;
+       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 ||
+                   (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 ||
+                   (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;
 }
 
 /**
@@ -1018,8 +1050,6 @@ bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
        plug_list = &plug->mq_list;
 
        list_for_each_entry_reverse(rq, plug_list, queuelist) {
-               bool merged = false;
-
                if (rq->q == q && same_queue_rq) {
                        /*
                         * Only blk-mq multiple hardware queues case checks the
@@ -1029,24 +1059,11 @@ bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
                        *same_queue_rq = rq;
                }
 
-               if (rq->q != q || !blk_rq_merge_ok(rq, bio))
+               if (rq->q != q)
                        continue;
 
-               switch (blk_try_merge(rq, bio)) {
-               case ELEVATOR_BACK_MERGE:
-                       merged = bio_attempt_back_merge(rq, bio, nr_segs);
-                       break;
-               case ELEVATOR_FRONT_MERGE:
-                       merged = bio_attempt_front_merge(rq, bio, nr_segs);
-                       break;
-               case ELEVATOR_DISCARD_MERGE:
-                       merged = bio_attempt_discard_merge(q, rq, bio);
-                       break;
-               default:
-                       break;
-               }
-
-               if (merged)
+               if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) ==
+                   BIO_MERGE_OK)
                        return true;
        }
 
@@ -1064,33 +1081,18 @@ bool blk_bio_list_merge(struct request_queue *q, struct list_head *list,
        int checked = 8;
 
        list_for_each_entry_reverse(rq, list, queuelist) {
-               bool merged = false;
-
                if (!checked--)
                        break;
 
-               if (!blk_rq_merge_ok(rq, bio))
-                       continue;
-
-               switch (blk_try_merge(rq, bio)) {
-               case ELEVATOR_BACK_MERGE:
-                       if (blk_mq_sched_allow_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(rq, bio,
-                                               nr_segs);
-                       break;
-               case ELEVATOR_DISCARD_MERGE:
-                       merged = bio_attempt_discard_merge(q, rq, bio);
-                       break;
-               default:
+               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 merged;
        }
 
        return false;

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 82acff96c093659f2a9aae9ca6806f46bdb09fc3..94db0c9d59b88ed502b2dca2156731897d2ea44c 100644 (file)
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -368,7 +368,7 @@ 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(rq, bio, nr_segs))
+               if (bio_attempt_back_merge(rq, bio, nr_segs) != BIO_MERGE_OK)
                        return false;
                *merged_request = attempt_back_merge(q, rq);
                if (!*merged_request)
@@ -377,14 +377,14 @@ 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(rq, bio, nr_segs))
+               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);
+               return bio_attempt_discard_merge(q, rq, bio) == BIO_MERGE_OK;
        default:
                return false;
        }

diff --git a/block/blk.h b/block/blk.h
index d6152d20d4e2bebc734587b6e9d4ce5edd4bd91f..a180443ac13f72f0b8fab1eb26cbed6fb8369475 100644 (file)
--- a/block/blk.h
+++ b/block/blk.h
@@ -29,6 +29,12 @@ struct blk_flush_queue {
        spinlock_t              mq_flush_lock;
 };
 
+enum bio_merge_status {
+       BIO_MERGE_OK,
+       BIO_MERGE_NONE,
+       BIO_MERGE_FAILED,
+};
+
 extern struct kmem_cache *blk_requestq_cachep;
 extern struct kobj_type blk_queue_ktype;
 extern struct ida blk_queue_ida;
@@ -169,12 +175,15 @@ static inline void blk_integrity_del(struct gendisk *disk)
 unsigned long blk_rq_timeout(unsigned long timeout);
 void blk_add_timer(struct request *req);
 
-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);
+enum bio_merge_status bio_attempt_front_merge(struct request *req,
+                                             struct bio *bio,
+                                             unsigned int nr_segs);
+enum bio_merge_status bio_attempt_back_merge(struct request *req,
+                                            struct bio *bio,
+                                            unsigned int nr_segs);
+enum bio_merge_status 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,
                unsigned int nr_segs, struct request **same_queue_rq);
 bool blk_bio_list_merge(struct request_queue *q, struct list_head *list,