block: add QUEUE_FLAG_NOWAIT

Add QUEUE_FLAG_NOWAIT to allow a block device to advertise support for
REQ_NOWAIT. Bio-based devices may set QUEUE_FLAG_NOWAIT where
applicable.

Update QUEUE_FLAG_MQ_DEFAULT to include QUEUE_FLAG_NOWAIT.  Also
update submit_bio_checks() to verify it is set for REQ_NOWAIT bios.

Reported-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-core.c b/block/blk-core.c
index 1cc4fa6..4884f1e 100644 (file)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -814,9 +814,9 @@ static noinline_for_stack bool submit_bio_checks(struct bio *bio)
 
        /*
         * For a REQ_NOWAIT based request, return -EOPNOTSUPP
-        * if queue is not a request based queue.
+        * if queue does not support NOWAIT.
         */
-       if ((bio->bi_opf & REQ_NOWAIT) && !queue_is_mq(q))
+       if ((bio->bi_opf & REQ_NOWAIT) && !blk_queue_nowait(q))
                goto not_supported;
 
        if (should_fail_bio(bio))

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 33f2838..d5a3e1a 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -619,10 +619,12 @@ struct request_queue {
 #define QUEUE_FLAG_PCI_P2PDMA  25      /* device supports PCI p2p requests */
 #define QUEUE_FLAG_ZONE_RESETALL 26    /* supports Zone Reset All */
 #define QUEUE_FLAG_RQ_ALLOC_TIME 27    /* record rq->alloc_time_ns */
-#define QUEUE_FLAG_HCTX_ACTIVE 28      /* at least one blk-mq hctx is active */
+#define QUEUE_FLAG_HCTX_ACTIVE 28      /* at least one blk-mq hctx is active */
+#define QUEUE_FLAG_NOWAIT       29     /* device supports NOWAIT */
 
 #define QUEUE_FLAG_MQ_DEFAULT  ((1 << QUEUE_FLAG_IO_STAT) |            \
-                                (1 << QUEUE_FLAG_SAME_COMP))
+                                (1 << QUEUE_FLAG_SAME_COMP) |          \
+                                (1 << QUEUE_FLAG_NOWAIT))
 
 void blk_queue_flag_set(unsigned int flag, struct request_queue *q);
 void blk_queue_flag_clear(unsigned int flag, struct request_queue *q);
@@ -664,6 +666,7 @@ bool blk_queue_flag_test_and_set(unsigned int flag, struct request_queue *q);
 #define blk_queue_pm_only(q)   atomic_read(&(q)->pm_only)
 #define blk_queue_fua(q)       test_bit(QUEUE_FLAG_FUA, &(q)->queue_flags)
 #define blk_queue_registered(q)        test_bit(QUEUE_FLAG_REGISTERED, &(q)->queue_flags)
+#define blk_queue_nowait(q)    test_bit(QUEUE_FLAG_NOWAIT, &(q)->queue_flags)
 
 extern void blk_set_pm_only(struct request_queue *q);
 extern void blk_clear_pm_only(struct request_queue *q);