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block: pm: Fix possible unbalanced nr_pending

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When someone calls blk_get_request() and blk_put_request()
without invoking blk_execute_rq() in between, nr_pending
will be unbalanced. Fix this by adding a flag, namely the
RQF_PM_ADDED, to track the usage of nr_pending, so that
blk_pm_put_request() won't touch nr_pending if the flag is
not set. Extra care should be given to blk_pm_requeue_request(),
because blk-flush.c inserts flush requests into queue without
calling blk_pm_add_request(), if the flush requests get requeued
by LLD, blk_pm_requeue_request() should anyways decrease
nr_pending in this situation to keep it balanced.

Change-Id: I7baa2049ac532e4fd22a0ce358133ba88266a314
Signed-off-by: Ziqi Chen <ziqichen@codeaurora.org>
Signed-off-by: Can Guo <cang@codeaurora.org>
This commit is contained in:
Can Guo 2021-04-06 03:31:49 -07:00 committed by Ziqi Chen
parent ef299a6053
commit 36a7bd907c
3 changed files with 19 additions and 6 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

8
block/blk-core.c
View file

@ -1741,8 +1741,12 @@ EXPORT_SYMBOL_GPL(part_round_stats);
#ifdef CONFIG_PM
static void blk_pm_put_request(struct request *rq)
{
if (rq->q->dev && !(rq->rq_flags & RQF_PM) && !--rq->q->nr_pending)
pm_runtime_mark_last_busy(rq->q->dev);
if (rq->q->dev && !(rq->rq_flags & RQF_PM) &&
(rq->rq_flags & RQF_PM_ADDED)) {
rq->rq_flags &= ~RQF_PM_ADDED;
if (!--rq->q->nr_pending)
pm_runtime_mark_last_busy(rq->q->dev);
}
}
#else
static inline void blk_pm_put_request(struct request *rq) {}

15
block/elevator.c
View file

@ -560,15 +560,22 @@ void elv_bio_merged(struct request_queue *q, struct request *rq,
#ifdef CONFIG_PM
static void blk_pm_requeue_request(struct request *rq)
{
if (rq->q->dev && !(rq->rq_flags & RQF_PM))
if (rq->q->dev && !(rq->rq_flags & RQF_PM) &&
(rq->rq_flags & (RQF_PM_ADDED | RQF_FLUSH_SEQ))) {
rq->rq_flags &= ~RQF_PM_ADDED;
rq->q->nr_pending--;
}
}
static void blk_pm_add_request(struct request_queue *q, struct request *rq)
{
if (q->dev && !(rq->rq_flags & RQF_PM) && q->nr_pending++ == 0 &&
(q->rpm_status == RPM_SUSPENDED || q->rpm_status == RPM_SUSPENDING))
pm_request_resume(q->dev);
if (q->dev && !(rq->rq_flags & RQF_PM)) {
rq->rq_flags |= RQF_PM_ADDED;
if (q->nr_pending++ == 0 &&
(q->rpm_status == RPM_SUSPENDED ||
q->rpm_status == RPM_SUSPENDING))
pm_request_resume(q->dev);
}
}
#else
static inline void blk_pm_requeue_request(struct request *rq) {}

2
include/linux/blkdev.h
View file

@ -128,6 +128,8 @@ typedef __u32 __bitwise req_flags_t;
#define RQF_MQ_POLL_SLEPT ((__force req_flags_t)(1 << 20))
/* ->timeout has been called, don't expire again */
#define RQF_TIMED_OUT ((__force req_flags_t)(1 << 21))
/* increased nr_pending for this request */
#define RQF_PM_ADDED ((__force req_flags_t)(1 << 22))
/* flags that prevent us from merging requests: */
#define RQF_NOMERGE_FLAGS \