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Revert "blk-mq, percpu_ref: implement a kludge for SCSI blk-mq stall during probe"

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This reverts commit 0a30288da1aec914e158c2d7a3482a85f632750f, which
was a temporary fix for SCSI blk-mq stall issue.  The following
patches will fix the issue properly by introducing atomic mode to
percpu_ref.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Kent Overstreet <kmo@daterainc.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Tejun Heo 2014-09-24 13:07:33 -04:00
parent d06efebf0c
commit 9eca80461a
3 changed files with 1 additions and 27 deletions
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11
block/blk-mq.c
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@ -119,16 +119,7 @@ void blk_mq_freeze_queue(struct request_queue *q)
spin_unlock_irq(q->queue_lock); spin_unlock_irq(q->queue_lock);
if (freeze) { if (freeze) {
/* percpu_ref_kill(&q->mq_usage_counter);
* XXX: Temporary kludge to work around SCSI blk-mq stall.
* SCSI synchronously creates and destroys many queues
* back-to-back during probe leading to lengthy stalls.
* This will be fixed by keeping ->mq_usage_counter in
* atomic mode until genhd registration, but, for now,
* let's work around using expedited synchronization.
*/
__percpu_ref_kill_expedited(&q->mq_usage_counter);
blk_mq_run_queues(q, false); blk_mq_run_queues(q, false);
} }
wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->mq_usage_counter)); wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->mq_usage_counter));

1
include/linux/percpu-refcount.h
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@ -72,7 +72,6 @@ void percpu_ref_reinit(struct percpu_ref *ref);
void percpu_ref_exit(struct percpu_ref *ref); void percpu_ref_exit(struct percpu_ref *ref);
void percpu_ref_kill_and_confirm(struct percpu_ref *ref, void percpu_ref_kill_and_confirm(struct percpu_ref *ref,
percpu_ref_func_t *confirm_kill); percpu_ref_func_t *confirm_kill);
void __percpu_ref_kill_expedited(struct percpu_ref *ref);
/** /**
* percpu_ref_kill - drop the initial ref * percpu_ref_kill - drop the initial ref

16
lib/percpu-refcount.c
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@ -189,19 +189,3 @@ void percpu_ref_kill_and_confirm(struct percpu_ref *ref,
call_rcu_sched(&ref->rcu, percpu_ref_kill_rcu); call_rcu_sched(&ref->rcu, percpu_ref_kill_rcu);
} }
EXPORT_SYMBOL_GPL(percpu_ref_kill_and_confirm); EXPORT_SYMBOL_GPL(percpu_ref_kill_and_confirm);
/*
* XXX: Temporary kludge to work around SCSI blk-mq stall. Used only by
* block/blk-mq.c::blk_mq_freeze_queue(). Will be removed during v3.18
* devel cycle. Do not use anywhere else.
*/
void __percpu_ref_kill_expedited(struct percpu_ref *ref)
{
WARN_ONCE(ref->pcpu_count_ptr & PCPU_REF_DEAD,
"percpu_ref_kill() called more than once on %pf!",
ref->release);
ref->pcpu_count_ptr |= PCPU_REF_DEAD;
synchronize_sched_expedited();
percpu_ref_kill_rcu(&ref->rcu);
}