linux-kernel - [PATCH RFC v3 05/10] dm: make sure create and remove dm device won't race with open and close table

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Date:   Tue, 15 Nov 2022 22:10:49 +0800
From:   Yu Kuai <yukuai1@...weicloud.com>
To:     hch@....de, axboe@...nel.dk, agk@...hat.com, snitzer@...nel.org,
        dm-devel@...hat.com
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        yukuai3@...wei.com, yukuai1@...weicloud.com, yi.zhang@...wei.com
Subject: [PATCH RFC v3 05/10] dm: make sure create and remove dm device won't race with open and close table

From: Yu Kuai <yukuai3@...wei.com>

open_table_device() and close_table_device() is protected by
table_devices_lock, hence use it to protect add_disk() and
del_gendisk().

Prepare to track per-add_disk holder relations in dm.

Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 drivers/md/dm.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 2917700b1e15..3728b56b364b 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1952,7 +1952,14 @@ static void cleanup_mapped_device(struct mapped_device *md)
 		spin_unlock(&_minor_lock);
 		if (dm_get_md_type(md) != DM_TYPE_NONE) {
 			dm_sysfs_exit(md);
+
+			/*
+			 * Hold lock to make sure del_gendisk() won't concurrent
+			 * with open/close_table_device().
+			 */
+			mutex_lock(&md->table_devices_lock);
 			del_gendisk(md->disk);
+			mutex_unlock(&md->table_devices_lock);
 		}
 		dm_queue_destroy_crypto_profile(md->queue);
 		put_disk(md->disk);
@@ -2312,15 +2319,24 @@ int dm_setup_md_queue(struct mapped_device *md, struct dm_table *t)
 	if (r)
 		return r;
 
+	/*
+	 * Hold lock to make sure add_disk() and del_gendisk() won't concurrent
+	 * with open_table_device() and close_table_device().
+	 */
+	mutex_lock(&md->table_devices_lock);
 	r = add_disk(md->disk);
+	mutex_unlock(&md->table_devices_lock);
 	if (r)
 		return r;
 
 	r = dm_sysfs_init(md);
 	if (r) {
+		mutex_lock(&md->table_devices_lock);
 		del_gendisk(md->disk);
+		mutex_unlock(&md->table_devices_lock);
 		return r;
 	}
+
 	md->type = type;
 	return 0;
 }
-- 
2.31.1