mmc: block: Fix unsupported parallel dispatch of requests

The mmc block driver does not support parallel dispatch of requests. In
normal circumstances, all requests are anyway funneled through a single
work item, so parallel dispatch never happens. However it can happen if
there is no elevator.

Fix that by detecting if a dispatch is in progress and returning busy
(BLK_STS_RESOURCE) in that case

Fixes: 81196976ed94 ("mmc: block: Add blk-mq support")
Cc: stable@vger.kernel.org # v4.16+
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

2 files changed, 8 insertions, 5 deletions

diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
index 648eb6743ed5..6edffeed9953 100644
--- a/drivers/mmc/core/queue.c
+++ b/drivers/mmc/core/queue.c
@@ -238,10 +238,6 @@ static void mmc_mq_exit_request(struct blk_mq_tag_set *set, struct request *req,
         mmc_exit_request(mq->queue, req);
 }
 
-/*
- * We use BLK_MQ_F_BLOCKING and have only 1 hardware queue, which means requests
- * will not be dispatched in parallel.
- */
 static blk_status_t mmc_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
                                     const struct blk_mq_queue_data *bd)
 {
@@ -264,7 +260,7 @@ static blk_status_t mmc_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
 
         spin_lock_irq(q->queue_lock);
 
-        if (mq->recovery_needed) {
+        if (mq->recovery_needed || mq->busy) {
                 spin_unlock_irq(q->queue_lock);
                 return BLK_STS_RESOURCE;
         }
@@ -291,6 +287,9 @@ static blk_status_t mmc_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
                 break;
         }
 
+        /* Parallel dispatch of requests is not supported at the moment */
+        mq->busy = true;
+
         mq->in_flight[issue_type] += 1;
         get_card = (mmc_tot_in_flight(mq) == 1);
         cqe_retune_ok = (mmc_cqe_qcnt(mq) == 1);
@@ -333,9 +332,12 @@ static blk_status_t mmc_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
                 mq->in_flight[issue_type] -= 1;
                 if (mmc_tot_in_flight(mq) == 0)
                         put_card = true;
+                mq->busy = false;
                 spin_unlock_irq(q->queue_lock);
                 if (put_card)
                         mmc_put_card(card, &mq->ctx);
+        } else {
+                WRITE_ONCE(mq->busy, false);
         }
 
         return ret;
diff --git a/drivers/mmc/core/queue.h b/drivers/mmc/core/queue.h
index 17e59d50b496..9bf3c9245075 100644
--- a/drivers/mmc/core/queue.h
+++ b/drivers/mmc/core/queue.h
@@ -81,6 +81,7 @@ struct mmc_queue {
         unsigned int            cqe_busy;
 #define MMC_CQE_DCMD_BUSY       BIT(0)
 #define MMC_CQE_QUEUE_FULL      BIT(1)
+        bool                    busy;
         bool                    use_cqe;
         bool                    recovery_needed;
         bool                    in_recovery;