Re: [PATCH 1/5] blk-mq: Export reading mq request state
From: Bart Van Assche <bvanassche@acm.org>
Date: 2019-03-08 18:07:26
Also in:
linux-nvme
On Fri, 2019-03-08 at 10:40 -0700, Keith Busch wrote:
Drivers may need to know the state of their requets.
Hi Keith, What makes you think that drivers should be able to check the state of their requests? Please elaborate.
quoted hunk ↗ jump to hunk
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index faed9d9eb84c..db113aee48bb 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h@@ -241,6 +241,15 @@ struct request { struct request *next_rq; }; +/** + * blk_mq_rq_state() - read the current MQ_RQ_* state of a request + * @rq: target request. + */ +static inline enum mq_rq_state blk_mq_rq_state(struct request *rq) +{ + return READ_ONCE(rq->state); +}
Please also explain how drivers can use this function without triggering a race condition with the code that modifies rq->state. Thanks, Bart.