The two APIs are required to allow request allocation of
RQF_PREEMPT when queue is preempt frozen.
We have to guarantee that normal freeze and preempt freeze
are run exclusive. Because for normal freezing, once
blk_freeze_queue_wait() is returned, no request can enter
queue any more.
Another issue we should pay attention to is that the race
of preempt freeze vs. blk_cleanup_queue(), and it is avoided
by not allowing to preempt freeeze after queue becomes dying,
otherwise preempt freeeze may hang forever.
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
block/blk-core.c | 2 +
block/blk-mq.c | 133 +++++++++++++++++++++++++++++++++++++++++++------
block/blk.h | 11 ++++
include/linux/blk-mq.h | 2 +
include/linux/blkdev.h | 6 +++
5 files changed, 140 insertions(+), 14 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 04327a60061e..ade9b5484a6e 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -905,6 +905,8 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
if (blkcg_init_queue(q))
goto fail_ref;
+ spin_lock_init(&q->freeze_lock);
+
return q;
fail_ref:
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 358b2ca33010..096c5f0ea518 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -118,19 +118,6 @@ void blk_mq_in_flight(struct request_queue *q, struct hd_struct *part,
blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);
}
-void blk_freeze_queue_start(struct request_queue *q)
-{
- int freeze_depth;
-
- freeze_depth = atomic_inc_return(&q->freeze_depth);
- if (freeze_depth == 1) {
- percpu_ref_kill(&q->q_usage_counter);
- if (q->mq_ops)
- blk_mq_run_hw_queues(q, false);
- }
-}
-EXPORT_SYMBOL_GPL(blk_freeze_queue_start);
-
void blk_freeze_queue_wait(struct request_queue *q)
{
if (!q->mq_ops)
@@ -148,6 +135,69 @@ int blk_mq_freeze_queue_wait_timeout(struct request_queue *q,
}
EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_wait_timeout);
+static bool queue_freeze_is_over(struct request_queue *q,
+ bool preempt, bool *queue_dying)
+{
+ /*
+ * preempt freeze has to be prevented after queue is set as
+ * dying, otherwise we may hang forever
+ */
+ if (preempt) {
+ spin_lock_irq(q->queue_lock);
+ *queue_dying = !!blk_queue_dying(q);
+ spin_unlock_irq(q->queue_lock);
+
+ return !q->normal_freezing || *queue_dying;
+ }
+ return !q->preempt_freezing;
+}
+
+static void __blk_freeze_queue_start(struct request_queue *q, bool preempt)
+{
+ int freeze_depth;
+ bool queue_dying;
+
+ /*
+ * Make sure normal freeze and preempt freeze are run
+ * exclusively, but each kind itself is allowed to be
+ * run concurrently, even nested.
+ */
+ spin_lock(&q->freeze_lock);
+ wait_event_cmd(q->freeze_wq,
+ queue_freeze_is_over(q, preempt, &queue_dying),
+ spin_unlock(&q->freeze_lock),
+ spin_lock(&q->freeze_lock));
+
+ if (preempt && queue_dying)
+ goto unlock;
+
+ freeze_depth = atomic_inc_return(&q->freeze_depth);
+ if (freeze_depth == 1) {
+ if (preempt) {
+ q->preempt_freezing = 1;
+ q->preempt_unfreezing = 0;
+ } else
+ q->normal_freezing = 1;
+ spin_unlock(&q->freeze_lock);
+
+ percpu_ref_kill(&q->q_usage_counter);
+ if (q->mq_ops)
+ blk_mq_run_hw_queues(q, false);
+
+ /* have to drain I/O here for preempt quiesce */
+ if (preempt)
+ blk_freeze_queue_wait(q);
+ } else
+ unlock:
+ spin_unlock(&q->freeze_lock);
+}
+
+void blk_freeze_queue_start(struct request_queue *q)
+{
+ __blk_freeze_queue_start(q, false);
+}
+EXPORT_SYMBOL_GPL(blk_freeze_queue_start);
+
/*
* Guarantee no request is in use, so we can change any data structure of
* the queue afterward.
@@ -166,20 +216,75 @@ void blk_freeze_queue(struct request_queue *q)
}
EXPORT_SYMBOL_GPL(blk_freeze_queue);
-void blk_unfreeze_queue(struct request_queue *q)
+static void blk_start_unfreeze_queue_preempt(struct request_queue *q)
+{
+ /* no new request can be coming after unfreezing */
+ spin_lock(&q->freeze_lock);
+ q->preempt_unfreezing = 1;
+ spin_unlock(&q->freeze_lock);
+
+ blk_freeze_queue_wait(q);
+}
+
+static void __blk_unfreeze_queue(struct request_queue *q, bool preempt)
{
int freeze_depth;
freeze_depth = atomic_dec_return(&q->freeze_depth);
WARN_ON_ONCE(freeze_depth < 0);
if (!freeze_depth) {
+ if (preempt)
+ blk_start_unfreeze_queue_preempt(q);
+
percpu_ref_reinit(&q->q_usage_counter);
+
+ /*
+ * clearing the freeze flag so that any pending
+ * freeze can move on
+ */
+ spin_lock(&q->freeze_lock);
+ if (preempt)
+ q->preempt_freezing = 0;
+ else
+ q->normal_freezing = 0;
+ spin_unlock(&q->freeze_lock);
wake_up_all(&q->freeze_wq);
}
}
+
+void blk_unfreeze_queue(struct request_queue *q)
+{
+ __blk_unfreeze_queue(q, false);
+}
EXPORT_SYMBOL_GPL(blk_unfreeze_queue);
/*
+ * Once this function is returned, only allow to get request
+ * of RQF_PREEMPT.
+ */
+void blk_freeze_queue_preempt(struct request_queue *q)
+{
+ /*
+ * If queue isn't in preempt_frozen, the queue has
+ * to be dying, so do nothing since no I/O can
+ * succeed any more.
+ */
+ __blk_freeze_queue_start(q, true);
+}
+EXPORT_SYMBOL_GPL(blk_freeze_queue_preempt);
+
+void blk_unfreeze_queue_preempt(struct request_queue *q)
+{
+ /*
+ * If queue isn't in preempt_frozen, the queue should
+ * be dying , so do nothing since no I/O can succeed.
+ */
+ if (blk_queue_is_preempt_frozen(q))
+ __blk_unfreeze_queue(q, true);
+}
+EXPORT_SYMBOL_GPL(blk_unfreeze_queue_preempt);
+
+/*
* FIXME: replace the scsi_internal_device_*block_nowait() calls in the
* mpt3sas driver such that this function can be removed.
*/
diff --git a/block/blk.h b/block/blk.h
index 21eed59d96db..243b2e7e5098 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -79,6 +79,17 @@ static inline void blk_queue_enter_live(struct request_queue *q)
percpu_ref_get(&q->q_usage_counter);
}
+static inline bool blk_queue_is_preempt_frozen(struct request_queue *q)
+{
+ bool preempt_frozen;
+
+ spin_lock(&q->freeze_lock);
+ preempt_frozen = q->preempt_freezing && !q->preempt_unfreezing;
+ spin_unlock(&q->freeze_lock);
+
+ return preempt_frozen;
+}
+
#ifdef CONFIG_BLK_DEV_INTEGRITY
void blk_flush_integrity(void);
bool __bio_integrity_endio(struct bio *);
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 62c3d1f7d12a..54b160bcb6a2 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -255,6 +255,8 @@ void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
busy_tag_iter_fn *fn, void *priv);
void blk_freeze_queue(struct request_queue *q);
void blk_unfreeze_queue(struct request_queue *q);
+void blk_freeze_queue_preempt(struct request_queue *q);
+void blk_unfreeze_queue_preempt(struct request_queue *q);
void blk_freeze_queue_start(struct request_queue *q);
void blk_freeze_queue_wait(struct request_queue *q);
int blk_mq_freeze_queue_wait_timeout(struct request_queue *q,
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 54450715915b..3c14c9588dcf 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -566,6 +566,12 @@ struct request_queue {
int bypass_depth;
atomic_t freeze_depth;
+ /* for run normal freeze and preempt freeze exclusive */
+ spinlock_t freeze_lock;
+ unsigned normal_freezing:1;
+ unsigned preempt_freezing:1;
+ unsigned preempt_unfreezing:1;
+
#if defined(CONFIG_BLK_DEV_BSG)
bsg_job_fn *bsg_job_fn;
struct bsg_class_device bsg_dev;
--
2.9.5
