From: Christoph Hellwig <hch@lst.de>
Date: Wed, 29 Sep 2021 09:12:41 +0200
Subject: [PATCH] block: keep q_usage_counter in atomic mode after del_gendisk
Git-commit: aec89dc5d421200b353d99a2bfff9e0967f67037
Patch-mainline: v5.15-rc6
References: jsc#PED-1183

Don't switch back to percpu mode to avoid the double RCU grace period
when tearing down SCSI devices.  After removing the disk only passthrough
commands can be send anyway.

Suggested-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20210929071241.934472-6-hch@lst.de
Tested-by: Yi Zhang <yi.zhang@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 block/blk-mq.c | 9 ++++++++-
 block/blk.h    | 1 +
 block/genhd.c  | 3 ++-
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 108a352051be..bc026372de43 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -188,9 +188,11 @@ void blk_mq_freeze_queue(struct request_queue *q)
 }
 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue);
 
-void blk_mq_unfreeze_queue(struct request_queue *q)
+void __blk_mq_unfreeze_queue(struct request_queue *q, bool force_atomic)
 {
 	mutex_lock(&q->mq_freeze_lock);
+	if (force_atomic)
+		q->q_usage_counter.data->force_atomic = true;
 	q->mq_freeze_depth--;
 	WARN_ON_ONCE(q->mq_freeze_depth < 0);
 	if (!q->mq_freeze_depth) {
@@ -199,6 +201,11 @@ void blk_mq_unfreeze_queue(struct request_queue *q)
 	}
 	mutex_unlock(&q->mq_freeze_lock);
 }
+
+void blk_mq_unfreeze_queue(struct request_queue *q)
+{
+	__blk_mq_unfreeze_queue(q, false);
+}
 EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue);
 
 /*
diff --git a/block/blk.h b/block/blk.h
index e2ed2257709a..6c3c00a8fe19 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -51,6 +51,7 @@ struct blk_flush_queue *blk_alloc_flush_queue(int node, int cmd_size,
 void blk_free_flush_queue(struct blk_flush_queue *q);
 
 void blk_freeze_queue(struct request_queue *q);
+void __blk_mq_unfreeze_queue(struct request_queue *q, bool force_atomic);
 void blk_queue_start_drain(struct request_queue *q);
 
 #define BIO_INLINE_VECS 4
diff --git a/block/genhd.c b/block/genhd.c
index 1fe816be9bcd..7a766cc613c7 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -596,7 +596,8 @@ void del_gendisk(struct gendisk *disk)
 	/*
 	 * Allow using passthrough request again after the queue is torn down.
 	 */
-	blk_mq_unfreeze_queue(q);
+	blk_queue_flag_clear(QUEUE_FLAG_INIT_DONE, q);
+	__blk_mq_unfreeze_queue(q, true);
 
 	if (!(disk->flags & GENHD_FL_HIDDEN)) {
 		sysfs_remove_link(&disk_to_dev(disk)->kobj, "bdi");
-- 
2.35.3