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block: clarify blk_add_timer() use case for blk-mq 

Just a comment update on not needing queue_lock, and that we aren't
really adding the request to a timeout list for !mq.

Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Jens Axboe 2015-11-24 15:58:53 -07:00
parent bd5cecea43
commit 3b627a3f93
1 changed files with 6 additions and 0 deletions
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6
block/blk-timeout.c
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@ -186,6 +186,7 @@ unsigned long blk_rq_timeout(unsigned long timeout)
* Notes:
* Each request has its own timer, and as it is added to the queue, we
* set up the timer. When the request completes, we cancel the timer.
* Queue lock must be held for the non-mq case, mq case doesn't care.
*/
void blk_add_timer(struct request *req)
{
@ -209,6 +210,11 @@ void blk_add_timer(struct request *req)
req->timeout = q->rq_timeout;
req->deadline = jiffies + req->timeout;
/*
* Only the non-mq case needs to add the request to a protected list.
* For the mq case we simply scan the tag map.
*/
if (!q->mq_ops)
list_add_tail(&req->timeout_list, &req->q->timeout_list);