blk-mq: add flag for drivers wanting blocking ->queue_rq()

If a driver sets BLK_MQ_F_BLOCKING, it is allowed to block in its
->queue_rq() handler. For that case, blk-mq ensures that we always
calls it from a safe context.

Signed-off-by: Jens Axboe <axboe@fb.com>
Tested-by: Josef Bacik <jbacik@fb.com>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 80d4838..e9ebe98 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -908,7 +908,7 @@ void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
            !blk_mq_hw_queue_mapped(hctx)))
                return;
 
            !blk_mq_hw_queue_mapped(hctx)))
                return;
 

-       if (!async) {
+       if (!async && !(hctx->flags & BLK_MQ_F_BLOCKING)) {

                int cpu = get_cpu();
                if (cpumask_test_cpu(cpu, hctx->cpumask)) {
                        __blk_mq_run_hw_queue(hctx);
                int cpu = get_cpu();
                if (cpumask_test_cpu(cpu, hctx->cpumask)) {
                        __blk_mq_run_hw_queue(hctx);

diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index fbcfdf3..5daa0ef 100644 (file)
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -155,6 +155,7 @@ enum {
        BLK_MQ_F_TAG_SHARED     = 1 << 1,
        BLK_MQ_F_SG_MERGE       = 1 << 2,
        BLK_MQ_F_DEFER_ISSUE    = 1 << 4,
        BLK_MQ_F_TAG_SHARED     = 1 << 1,
        BLK_MQ_F_SG_MERGE       = 1 << 2,
        BLK_MQ_F_DEFER_ISSUE    = 1 << 4,

+       BLK_MQ_F_BLOCKING       = 1 << 5,

        BLK_MQ_F_ALLOC_POLICY_START_BIT = 8,
        BLK_MQ_F_ALLOC_POLICY_BITS = 1,
 
        BLK_MQ_F_ALLOC_POLICY_START_BIT = 8,
        BLK_MQ_F_ALLOC_POLICY_BITS = 1,