4 files changed, 15 insertions, 5 deletions
diff --git a/block/blk-core.c b/block/blk-core.c
index 3bb9e9f7f87e..9677c6525ed8 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1102,7 +1102,7 @@ static struct request *blk_old_get_request(struct request_queue *q, int rw,
 struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask)
 {
        if (q->mq_ops)
-                return blk_mq_alloc_request(q, rw, gfp_mask);
+                return blk_mq_alloc_request(q, rw, gfp_mask, false);
        else
                return blk_old_get_request(q, rw, gfp_mask);
 }
diff --git a/block/blk-flush.c b/block/blk-flush.c
index 3e4cc9c7890a..331e627301ea 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -286,7 +286,7 @@ static void mq_flush_work(struct work_struct *work)
        /* We don't need set REQ_FLUSH_SEQ, it's for consistency */
        rq = blk_mq_alloc_request(q, WRITE_FLUSH|REQ_FLUSH_SEQ,
-                __GFP_WAIT|GFP_ATOMIC);
+                __GFP_WAIT|GFP_ATOMIC, true);
        rq->cmd_type = REQ_TYPE_FS;
        rq->end_io = flush_end_io;
diff --git a/block/blk-mq.c b/block/blk-mq.c
index ac804c635040..2dc8de86d0d2 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -210,14 +210,15 @@ static struct request *blk_mq_alloc_request_pinned(struct request_queue *q,
        return rq;
 }
-struct request *blk_mq_alloc_request(struct request_queue *q, int rw, gfp_t gfp)
+struct request *blk_mq_alloc_request(struct request_queue *q, int rw,
+                gfp_t gfp, bool reserved)
 {
        struct request *rq;
        if (blk_mq_queue_enter(q))
                return NULL;
-        rq = blk_mq_alloc_request_pinned(q, rw, gfp, false);
+        rq = blk_mq_alloc_request_pinned(q, rw, gfp, reserved);
        blk_mq_put_ctx(rq->mq_ctx);
        return rq;
 }
@@ -1327,6 +1328,15 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_reg *reg,
                reg->queue_depth = BLK_MQ_MAX_DEPTH;
        }
+        /*
+         * Set aside a tag for flush requests.  It will only be used while
+         * another flush request is in progress but outside the driver.
+         *
+         * TODO: only allocate if flushes are supported
+         */
+        reg->queue_depth++;
+        reg->reserved_tags++;
        if (reg->queue_depth < (reg->reserved_tags + BLK_MQ_TAG_MIN))
                return ERR_PTR(-EINVAL);
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 3368b97bee73..ab0e9b2025b3 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -124,7 +124,7 @@ void blk_mq_insert_request(struct request_queue *, struct request *, 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 *);
-struct request *blk_mq_alloc_request(struct request_queue *q, int rw, gfp_t gfp);
+struct request *blk_mq_alloc_request(struct request_queue *q, int rw, gfp_t gfp, bool reserved);
 struct request *blk_mq_alloc_reserved_request(struct request_queue *q, int rw, gfp_t gfp);
 struct request *blk_mq_rq_from_tag(struct request_queue *q, unsigned int tag);