[PATCH 20/23][SRU][OEM-5.14] block: keep q_usage_counter in atomic mode after del_gendisk

[Koba Ko]

From: Christoph Hellwig <hch at lst.de>

BugLink: https://bugs.launchpad.net/bugs/1958850 

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 at redhat.com>
Signed-off-by: Christoph Hellwig <hch at lst.de>
Tested-by: Darrick J. Wong <djwong at kernel.org>
Link: https://lore.kernel.org/r/20210929071241.934472-6-hch@lst.de
Tested-by: Yi Zhang <yi.zhang at redhat.com>
Signed-off-by: Jens Axboe <axboe at kernel.dk>
(cherry picked from commit aec89dc5d421200b353d99a2bfff9e0967f67037)
Signed-off-by: Koba Ko <koba.ko at canonical.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 d051f3ae04491..024b8c3940ad1 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 bb2193fe8aea9..dccd7fb69c121 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 f8cc2476f8ee6..96198319ee8d9 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -629,7 +629,8 @@ 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");
-- 
2.25.1