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block: fix peeking requests during PM 

We need to look for an active PM request until the next softbarrier
instead of looking for the first non-PM request.  Otherwise any cause
of request reordering might starve the PM request(s).

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
hifive-unleashed-5.1
Christoph Hellwig 2017-10-20 16:45:23 +02:00 committed by Jens Axboe
parent 21e768b442
commit e4f36b249b
1 changed files with 18 additions and 17 deletions
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35
block/blk-core.c
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@ -2511,20 +2511,22 @@ void blk_account_io_done(struct request *req)
* Don't process normal requests when queue is suspended
* or in the process of suspending/resuming
*/
static struct request *blk_pm_peek_request(struct request_queue *q,
struct request *rq)
static bool blk_pm_allow_request(struct request *rq)
{
if (q->dev && (q->rpm_status == RPM_SUSPENDED ||
(q->rpm_status != RPM_ACTIVE && !(rq->rq_flags & RQF_PM))))
return NULL;
else
return rq;
switch (rq->q->rpm_status) {
case RPM_RESUMING:
case RPM_SUSPENDING:
return rq->rq_flags & RQF_PM;
case RPM_SUSPENDED:
return false;
}
return true;
}
#else
static inline struct request *blk_pm_peek_request(struct request_queue *q,
struct request *rq)
static bool blk_pm_allow_request(struct request *rq)
{
return rq;
return true;
}
#endif
@ -2572,9 +2574,12 @@ static struct request *elv_next_request(struct request_queue *q)
WARN_ON_ONCE(q->mq_ops);
while (1) {
if (!list_empty(&q->queue_head)) {
rq = list_entry_rq(q->queue_head.next);
return rq;
list_for_each_entry(rq, &q->queue_head, queuelist) {
if (blk_pm_allow_request(rq))
return rq;
if (rq->rq_flags & RQF_SOFTBARRIER)
break;
}
/*
@ -2625,10 +2630,6 @@ struct request *blk_peek_request(struct request_queue *q)
WARN_ON_ONCE(q->mq_ops);
while ((rq = elv_next_request(q)) != NULL) {
rq = blk_pm_peek_request(q, rq);
if (!rq)
break;
if (!(rq->rq_flags & RQF_STARTED)) {
/*
* This is the first time the device driver