[PATCH 6.1.y 1/2] block: set the disk capacity to 0 in blk_mark_disk_dead

[Sasha Levin <sashal@kernel.org>]

From: Christoph Hellwig <hch@lst.de>

[ Upstream commit 71b26083d59cd4ab22489829ffe7d4ead93f5546 ]

nvme and xen-blkfront are already doing this to stop buffered writes from
creating dirty pages that can't be written out later.  Move it to the
common code.

This also removes the comment about the ordering from nvme, as bd_mutex
not only is gone entirely, but also hasn't been used for locking updates
to the disk size long before that, and thus the ordering requirement
documented there doesn't apply any more.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Chao Leng <lengchao@huawei.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20221101150050.3510-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Stable-dep-of: 61b6d1df1d62 ("xen-blkfront: Fix IO race during unplug")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 block/genhd.c                | 5 +++++
 drivers/block/xen-blkfront.c | 1 -
 drivers/nvme/host/core.c     | 7 +------
 3 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index ee6dc7feccc6f..f06195e53571c 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -595,6 +595,11 @@ void blk_mark_disk_dead(struct gendisk *disk)
 	blk_queue_flag_set(QUEUE_FLAG_DYING, disk->queue);
 	set_bit(GD_DEAD, &disk->state);
 	blk_queue_start_drain(disk->queue);
+
+	/*
+	 * Stop buffered writers from dirtying pages that can't be written out.
+	 */
+	set_capacity_and_notify(disk, 0);
 }
 EXPORT_SYMBOL_GPL(blk_mark_disk_dead);
 
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index df0eaf15a4ddd..7ad03bcd9f274 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -2134,7 +2134,6 @@ static void blkfront_closing(struct blkfront_info *info)
 	if (info->rq && info->gd) {
 		blk_mq_stop_hw_queues(info->rq);
 		blk_mark_disk_dead(info->gd);
-		set_capacity(info->gd, 0);
 	}
 
 	for_each_rinfo(info, rinfo, i) {
diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 26233e6a50da9..ecaba784e593d 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -5339,10 +5339,7 @@ static void nvme_stop_ns_queue(struct nvme_ns *ns)
 /*
  * Prepare a queue for teardown.
  *
- * This must forcibly unquiesce queues to avoid blocking dispatch, and only set
- * the capacity to 0 after that to avoid blocking dispatchers that may be
- * holding bd_butex.  This will end buffered writers dirtying pages that can't
- * be synced.
+ * This must forcibly unquiesce queues to avoid blocking dispatch.
  */
 static void nvme_set_queue_dying(struct nvme_ns *ns)
 {
@@ -5351,8 +5348,6 @@ static void nvme_set_queue_dying(struct nvme_ns *ns)
 
 	blk_mark_disk_dead(ns->disk);
 	nvme_start_ns_queue(ns);
-
-	set_capacity_and_notify(ns->disk, 0);
 }
 
 /**
-- 
2.53.0