blk-mq: abstract out blk-mq-sched rq list iteration bio merge helper

No functional changes in this patch, just a prep patch for utilizing
this in an IO scheduler.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Omar Sandoval <osandov@fb.com>

1 files changed, 24 insertions, 10 deletions

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 25c14c58385c..b0f2c2a40a0c 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -268,19 +268,16 @@ bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
 EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);
 
 /*
- * Reverse check our software queue for entries that we could potentially
- * merge with. Currently includes a hand-wavy stop count of 8, to not spend
- * too much time checking for merges.
+ * Iterate list of requests and see if we can merge this bio with any
+ * of them.
  */
-static bool blk_mq_attempt_merge(struct request_queue *q,
-                                 struct blk_mq_ctx *ctx, struct bio *bio)
+bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list,
+                           struct bio *bio)
 {
         struct request *rq;
         int checked = 8;
 
-        lockdep_assert_held(&ctx->lock);
-
-        list_for_each_entry_reverse(rq, &ctx->rq_list, queuelist) {
+        list_for_each_entry_reverse(rq, list, queuelist) {
                 bool merged = false;
 
                 if (!checked--)
@@ -305,13 +302,30 @@ static bool blk_mq_attempt_merge(struct request_queue *q,
                         continue;
                 }
 
-                if (merged)
-                        ctx->rq_merged++;
                 return merged;
         }
 
         return false;
 }
+EXPORT_SYMBOL_GPL(blk_mq_bio_list_merge);
+
+/*
+ * Reverse check our software queue for entries that we could potentially
+ * merge with. Currently includes a hand-wavy stop count of 8, to not spend
+ * too much time checking for merges.
+ */
+static bool blk_mq_attempt_merge(struct request_queue *q,
+                                 struct blk_mq_ctx *ctx, struct bio *bio)
+{
+        lockdep_assert_held(&ctx->lock);
+
+        if (blk_mq_bio_list_merge(q, &ctx->rq_list, bio)) {
+                ctx->rq_merged++;
+                return true;
+        }
+
+        return false;
+}
 
 bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)
 {