path: root/block/mq-deadline.c
diff options
authorJens Axboe <>2018-01-06 09:23:11 -0700
committerJens Axboe <>2018-01-06 09:23:11 -0700
commitca11f209a4c88743fb4b652fd812470e6fecc598 (patch)
treebfca0db75895b6582233d5a540b62a586d7709bc /block/mq-deadline.c
parent14db49172649aac001fd77a3fd53d12c6df22daf (diff)
mq-deadline: make it clear that __dd_dispatch_request() works on all hw queues
Don't pass in the hardware queue to __dd_dispatch_request(), since it leads the reader to believe that we are returning a request for that specific hardware queue. That's not how mq-deadline works, the state for determining which request to serve next is shared across all hardware queues for a device. Reviewed-by: Omar Sandoval <> Reviewed-by: Ming Lei <> Signed-off-by: Jens Axboe <>
Diffstat (limited to 'block/mq-deadline.c')
1 files changed, 8 insertions, 3 deletions
diff --git a/block/mq-deadline.c b/block/mq-deadline.c
index d56972e8ebda..c56f211c8440 100644
--- a/block/mq-deadline.c
+++ b/block/mq-deadline.c
@@ -267,9 +267,8 @@ deadline_next_request(struct deadline_data *dd, int data_dir)
* deadline_dispatch_requests selects the best request according to
* read/write expire, fifo_batch, etc
-static struct request *__dd_dispatch_request(struct blk_mq_hw_ctx *hctx)
+static struct request *__dd_dispatch_request(struct deadline_data *dd)
- struct deadline_data *dd = hctx->queue->elevator->elevator_data;
struct request *rq, *next_rq;
bool reads, writes;
int data_dir;
@@ -372,13 +371,19 @@ done:
return rq;
+ * One confusing aspect here is that we get called for a specific
+ * hardware queue, but we return a request that may not be for a
+ * different hardware queue. This is because mq-deadline has shared
+ * state for all hardware queues, in terms of sorting, FIFOs, etc.
+ */
static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx)
struct deadline_data *dd = hctx->queue->elevator->elevator_data;
struct request *rq;
- rq = __dd_dispatch_request(hctx);
+ rq = __dd_dispatch_request(dd);
return rq;