block: model freeze & enter queue as lock for supporting lockdep

Recently we got several deadlock report[1][2][3] caused by
blk_mq_freeze_queue and blk_enter_queue().

Turns out the two are just like acquiring read/write lock, so model them
as read/write lock for supporting lockdep:

1) model q->q_usage_counter as two locks(io and queue lock)

- queue lock covers sync with blk_enter_queue()

- io lock covers sync with bio_enter_queue()

2) make the lockdep class/key as per-queue:

- different subsystem has very different lock use pattern, shared lock
 class causes false positive easily

- freeze_queue degrades to no lock in case that disk state becomes DEAD
  because bio_enter_queue() won't be blocked any more

- freeze_queue degrades to no lock in case that request queue becomes dying
  because blk_enter_queue() won't be blocked any more

3) model blk_mq_freeze_queue() as acquire_exclusive & try_lock
- it is exclusive lock, so dependency with blk_enter_queue() is covered

- it is trylock because blk_mq_freeze_queue() are allowed to run
  concurrently

4) model blk_enter_queue() & bio_enter_queue() as acquire_read()
- nested blk_enter_queue() are allowed

- dependency with blk_mq_freeze_queue() is covered

- blk_queue_exit() is often called from other contexts(such as irq), and
it can't be annotated as lock_release(), so simply do it in
blk_enter_queue(), this way still covered cases as many as possible

With lockdep support, such kind of reports may be reported asap and
needn't wait until the real deadlock is triggered.

For example, lockdep report can be triggered in the report[3] with this
patch applied.

[1] occasional block layer hang when setting 'echo noop > /sys/block/sda/queue/scheduler'
https://bugzilla.kernel.org/show_bug.cgi?id=219166

[2] del_gendisk() vs blk_queue_enter() race condition
https://lore.kernel.org/linux-block/20241003085610.GK11458@google.com/

[3] queue_freeze & queue_enter deadlock in scsi
https://lore.kernel.org/linux-block/ZxG38G9BuFdBpBHZ@fedora/T/#u

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20241025003722.3630252-4-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 16 insertions, 2 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index bc5e8c5eaac9..09d10bb95fda 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -261,6 +261,8 @@ static void blk_free_queue(struct request_queue *q)
 		blk_mq_release(q);
 
 	ida_free(&blk_queue_ida, q->id);
+	lockdep_unregister_key(&q->io_lock_cls_key);
+	lockdep_unregister_key(&q->q_lock_cls_key);
 	call_rcu(&q->rcu_head, blk_free_queue_rcu);
 }
 
@@ -278,18 +280,20 @@ void blk_put_queue(struct request_queue *q)
 }
 EXPORT_SYMBOL(blk_put_queue);
 
-void blk_queue_start_drain(struct request_queue *q)
+bool blk_queue_start_drain(struct request_queue *q)
 {
 	/*
 	 * When queue DYING flag is set, we need to block new req
 	 * entering queue, so we call blk_freeze_queue_start() to
 	 * prevent I/O from crossing blk_queue_enter().
 	 */
-	blk_freeze_queue_start(q);
+	bool freeze = __blk_freeze_queue_start(q);
 	if (queue_is_mq(q))
 		blk_mq_wake_waiters(q);
 	/* Make blk_queue_enter() reexamine the DYING flag. */
 	wake_up_all(&q->mq_freeze_wq);
+
+	return freeze;
 }
 
 /**
@@ -321,6 +325,8 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags)
 			return -ENODEV;
 	}
 
+	rwsem_acquire_read(&q->q_lockdep_map, 0, 0, _RET_IP_);
+	rwsem_release(&q->q_lockdep_map, _RET_IP_);
 	return 0;
 }
 
@@ -352,6 +358,8 @@ int __bio_queue_enter(struct request_queue *q, struct bio *bio)
 			goto dead;
 	}
 
+	rwsem_acquire_read(&q->io_lockdep_map, 0, 0, _RET_IP_);
+	rwsem_release(&q->io_lockdep_map, _RET_IP_);
 	return 0;
 dead:
 	bio_io_error(bio);
@@ -441,6 +449,12 @@ struct request_queue *blk_alloc_queue(struct queue_limits *lim, int node_id)
 				PERCPU_REF_INIT_ATOMIC, GFP_KERNEL);
 	if (error)
 		goto fail_stats;
+	lockdep_register_key(&q->io_lock_cls_key);
+	lockdep_register_key(&q->q_lock_cls_key);
+	lockdep_init_map(&q->io_lockdep_map, "&q->q_usage_counter(io)",
+			 &q->io_lock_cls_key, 0);
+	lockdep_init_map(&q->q_lockdep_map, "&q->q_usage_counter(queue)",
+			 &q->q_lock_cls_key, 0);
 
 	q->nr_requests = BLKDEV_DEFAULT_RQ;