blk-mq: support at_head inserations for blk_execute_rq

This is neede for proper SG_IO operation as well as various uses of
blk_execute_rq from the SCSI midlayer.

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

2 files changed, 11 insertions, 8 deletions

diff --git a/block/blk-exec.c b/block/blk-exec.c
index bbfc072a79c2..c68613bb4c79 100644
--- a/block/blk-exec.c
+++ b/block/blk-exec.c
@@ -65,7 +65,7 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk,
          * be resued after dying flag is set
          */
         if (q->mq_ops) {
-                blk_mq_insert_request(q, rq, true);
+                blk_mq_insert_request(q, rq, at_head, true);
                 return;
         }
 
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 9072d0ab184f..c9306e3403fe 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -714,13 +714,16 @@ static void blk_mq_work_fn(struct work_struct *work)
 }
 
 static void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx,
-                                    struct request *rq)
+                                    struct request *rq, bool at_head)
 {
         struct blk_mq_ctx *ctx = rq->mq_ctx;
 
         trace_block_rq_insert(hctx->queue, rq);
 
-        list_add_tail(&rq->queuelist, &ctx->rq_list);
+        if (at_head)
+                list_add(&rq->queuelist, &ctx->rq_list);
+        else
+                list_add_tail(&rq->queuelist, &ctx->rq_list);
         blk_mq_hctx_mark_pending(hctx, ctx);
 
         /*
@@ -730,7 +733,7 @@ static void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx,
 }
 
 void blk_mq_insert_request(struct request_queue *q, struct request *rq,
-                           bool run_queue)
+                           bool at_head, bool run_queue)
 {
         struct blk_mq_hw_ctx *hctx;
         struct blk_mq_ctx *ctx, *current_ctx;
@@ -749,7 +752,7 @@ void blk_mq_insert_request(struct request_queue *q, struct request *rq,
                         rq->mq_ctx = ctx;
                 }
                 spin_lock(&ctx->lock);
-                __blk_mq_insert_request(hctx, rq);
+                __blk_mq_insert_request(hctx, rq, at_head);
                 spin_unlock(&ctx->lock);
 
                 blk_mq_put_ctx(current_ctx);
@@ -781,7 +784,7 @@ void blk_mq_run_request(struct request *rq, bool run_queue, bool async)
 
         /* ctx->cpu might be offline */
         spin_lock(&ctx->lock);
-        __blk_mq_insert_request(hctx, rq);
+        __blk_mq_insert_request(hctx, rq, false);
         spin_unlock(&ctx->lock);
 
         blk_mq_put_ctx(current_ctx);
@@ -819,7 +822,7 @@ static void blk_mq_insert_requests(struct request_queue *q,
                 rq = list_first_entry(list, struct request, queuelist);
                 list_del_init(&rq->queuelist);
                 rq->mq_ctx = ctx;
-                __blk_mq_insert_request(hctx, rq);
+                __blk_mq_insert_request(hctx, rq, false);
         }
         spin_unlock(&ctx->lock);
 
@@ -971,7 +974,7 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
                 __blk_mq_free_request(hctx, ctx, rq);
         else {
                 blk_mq_bio_to_request(rq, bio);
-                __blk_mq_insert_request(hctx, rq);
+                __blk_mq_insert_request(hctx, rq, false);
         }
 
         spin_unlock(&ctx->lock);