linux-kernel - [PATCH v2] bcache: explicitly destroy mutex while exiting

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Date:   Tue, 10 Oct 2017 17:00:49 +0800
From:   Liang Chen <liangchen.linux@...il.com>
To:     linux-bcache@...r.kernel.org
Cc:     mlyle@...e.org, i@...y.li, kent.overstreet@...il.com,
        linux-kernel@...r.kernel.org,
        Liang Chen <liangchen.linux@...il.com>
Subject: [PATCH v2] bcache: explicitly destroy mutex while exiting

mutex_destroy does nothing most of time, but it's better to call
it to make the code future proof and it also has some meaning
for like mutex debug.

As Coly pointed out in a previous review, bcache_exit() may not be
able to handle all the references properly if userspace registers
cache and backing devices right before bch_debug_init runs and
bch_debug_init failes later. So not exposing userspace interface
until everything is ready to avoid that issue.

Signed-off-by: Liang Chen <liangchen.linux@...il.com>
---
 drivers/md/bcache/super.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index fc0a31b..25bf003 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -2085,6 +2085,7 @@ static void bcache_exit(void)
 	if (bcache_major)
 		unregister_blkdev(bcache_major, "bcache");
 	unregister_reboot_notifier(&reboot);
+	mutex_destroy(&bch_register_lock);
 }
 
 static int __init bcache_init(void)
@@ -2103,14 +2104,15 @@ static int __init bcache_init(void)
 	bcache_major = register_blkdev(0, "bcache");
 	if (bcache_major < 0) {
 		unregister_reboot_notifier(&reboot);
+		mutex_destroy(&bch_register_lock);
 		return bcache_major;
 	}
 
 	if (!(bcache_wq = alloc_workqueue("bcache", WQ_MEM_RECLAIM, 0)) ||
 	    !(bcache_kobj = kobject_create_and_add("bcache", fs_kobj)) ||
-	    sysfs_create_files(bcache_kobj, files) ||
 	    bch_request_init() ||
-	    bch_debug_init(bcache_kobj))
+	    bch_debug_init(bcache_kobj) ||
+	    sysfs_create_files(bcache_kobj, files))
 		goto err;
 
 	return 0;
-- 
1.8.3.1