[PATCH 1/4] blk-mq: support at_head inserations for blk_execute_rq

[Christoph Hellwig]

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 <h...@lst.de>
---
 block/blk-exec.c       |    2 +-
 block/blk-mq.c         |   17 ++++++++++-------
 include/linux/blk-mq.h |    3 ++-
 3 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/block/blk-exec.c b/block/blk-exec.c
index bbfc072..c68613b 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 57039fc..40fc4dd 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -693,13 +693,16 @@ 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);
 
        /*
@@ -709,7 +712,7 @@ 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;
@@ -728,7 +731,7 @@ 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);
@@ -760,7 +763,7 @@ 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);
@@ -798,7 +801,7 @@ 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);
 
@@ -950,7 +953,7 @@ 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);
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 161b231..8e6e710 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -119,7 +119,8 @@ void blk_mq_init_commands(struct request_queue *, void 
(*init)(void *data, struc
 
 void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule);
 
-void blk_mq_insert_request(struct request_queue *, struct request *, bool);
+void blk_mq_insert_request(struct request_queue *, struct request *,
+               bool, bool);
 void blk_mq_run_queues(struct request_queue *q, bool async);
 void blk_mq_free_request(struct request *rq);
 bool blk_mq_can_queue(struct blk_mq_hw_ctx *);
-- 
1.7.10.4


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