commit aec89dc5d421200b353d99a2bfff9e0967f67037
author Christoph Hellwig <hch@lst.de> Wed Sep 29 09:12:41 2021 +0200
committer Jens Axboe <axboe@kernel.dk> Fri Oct 15 21:02:54 2021 -0600
tree cfecaf05ddb52c19550291145e7b7bb087744ffd
parent 8e141f9eb803e209714a80aa6ec073893f94c526

block: keep q_usage_counter in atomic mode after del_gendisk

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>

block/blk-mq.c

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 108a352..bc02637 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -188,9 +188,11 @@
 }
 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 @@
 	}
 	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);
 
 /*

block/blk.h

diff --git a/block/blk.h b/block/blk.h
index e2ed225..6c3c00a 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -51,6 +51,7 @@
 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

block/genhd.c

diff --git a/block/genhd.c b/block/genhd.c
index 1fe816be..7a766cc 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -596,7 +596,8 @@
 	/*
 	 * 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");