linux-kernel - [PATCH 1/2] md: fix WARN_ON if create symlink fail in bind_rdev_to

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Message-Id: <20231221071109.1562530-2-linan666@huaweicloud.com>
Date: Thu, 21 Dec 2023 15:11:08 +0800
From: linan666@...weicloud.com
To: song@...nel.org,
	yukuai3@...wei.com
Cc: linux-raid@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linan666@...weicloud.com,
	yi.zhang@...wei.com,
	houtao1@...wei.com,
	yangerkun@...wei.com
Subject: [PATCH 1/2] md: fix WARN_ON if create symlink fail in bind_rdev_to_array()

From: Li Nan <linan122@...wei.com>

Removing a device can trigger WARN_ON in bd_unlink_disk_holder() if creating
symlink failed while adding device.

  WARNING: CPU: 0 PID: 742 at block/holder.c:145 bd_unlink_disk_holder+0x17b/0x1a0

Fix it by adding the flag 'SymlinkCreated', which only be set after
creating symlink success.

Signed-off-by: Li Nan <linan122@...wei.com>
---
 drivers/md/md.h | 3 +++
 drivers/md/md.c | 8 ++++++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/md/md.h b/drivers/md/md.h
index 8d881cc59799..427d17713a8c 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -207,6 +207,9 @@ enum flag_bits {
 				 * check if there is collision between raid1
 				 * serial bios.
 				 */
+	SymlinkCreated,		/* This device has created the symlink
+				 * with gendisk.
+				 */
 };
 
 static inline int is_badblock(struct md_rdev *rdev, sector_t s, int sectors,
diff --git a/drivers/md/md.c b/drivers/md/md.c
index e05858653a41..d6612b922c76 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2526,7 +2526,8 @@ static int bind_rdev_to_array(struct md_rdev *rdev, struct mddev *mddev)
 		sysfs_get_dirent_safe(rdev->kobj.sd, "bad_blocks");
 
 	list_add_rcu(&rdev->same_set, &mddev->disks);
-	bd_link_disk_holder(rdev->bdev, mddev->gendisk);
+	if (!bd_link_disk_holder(rdev->bdev, mddev->gendisk))
+		set_bit(SymlinkCreated, &rdev->flags);
 
 	/* May as well allow recovery to be retried once */
 	mddev->recovery_disabled++;
@@ -2561,7 +2562,10 @@ static void md_kick_rdev_from_array(struct md_rdev *rdev)
 {
 	struct mddev *mddev = rdev->mddev;
 
-	bd_unlink_disk_holder(rdev->bdev, rdev->mddev->gendisk);
+	if (test_bit(SymlinkCreated, &rdev->flags)) {
+		bd_unlink_disk_holder(rdev->bdev, rdev->mddev->gendisk);
+		clear_bit(SymlinkCreated, &rdev->flags);
+	}
 	list_del_rcu(&rdev->same_set);
 	pr_debug("md: unbind<%pg>\n", rdev->bdev);
 	mddev_destroy_serial_pool(rdev->mddev, rdev);
-- 
2.39.2