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

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>

3 files changed, 1 insertions, 27 deletions

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 255d79c14dc1..44a78ae3f899 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -119,16 +119,7 @@ void blk_mq_freeze_queue(struct request_queue *q)
         spin_unlock_irq(q->queue_lock);
 
         if (freeze) {
-                /*
-                 * 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);
-
+                percpu_ref_kill(&q->mq_usage_counter);
                 blk_mq_run_queues(q, false);
         }
         wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->mq_usage_counter));
diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
index 11b38ceca7e2..5df6784bd9d2 100644
--- a/include/linux/percpu-refcount.h
+++ b/include/linux/percpu-refcount.h
@@ -72,7 +72,6 @@ void percpu_ref_reinit(struct percpu_ref *ref);
 void percpu_ref_exit(struct percpu_ref *ref);
 void percpu_ref_kill_and_confirm(struct percpu_ref *ref,
                                  percpu_ref_func_t *confirm_kill);
-void __percpu_ref_kill_expedited(struct percpu_ref *ref);
 
 /**
  * percpu_ref_kill - drop the initial ref
diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c
index c6c31e2829b1..559ee0b20318 100644
--- a/lib/percpu-refcount.c
+++ b/lib/percpu-refcount.c
@@ -189,19 +189,3 @@ void percpu_ref_kill_and_confirm(struct percpu_ref *ref,
         call_rcu_sched(&ref->rcu, percpu_ref_kill_rcu);
 }
 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);
-}