linux-kernel - [PATCH 3.13.y-ckt 007/138] bcache: Fix a lockdep splat in an error path

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Message-Id: <1457565265-15195-8-git-send-email-kamal@canonical.com>
Date:	Wed,  9 Mar 2016 15:12:14 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Kent Overstreet <kmo@...erainc.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.13.y-ckt 007/138] bcache: Fix a lockdep splat in an error path

3.13.11-ckt36 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Kent Overstreet <kmo@...erainc.com>

commit 4fa03402cda2fac1a54248c7578b939d95931dc0 upstream.

Signed-off-by: Kent Overstreet <kmo@...erainc.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/md/bcache/super.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index ccc0133..a4949ce 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1846,7 +1846,10 @@ static void register_cache(struct cache_sb *sb, struct page *sb_page,
 	if (kobject_add(&ca->kobj, &part_to_dev(bdev->bd_part)->kobj, "bcache"))
 		goto err;
 
+	mutex_lock(&bch_register_lock);
 	err = register_cache_set(ca);
+	mutex_unlock(&bch_register_lock);
+
 	if (err)
 		goto err;
 
@@ -1908,8 +1911,6 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
 	if (!try_module_get(THIS_MODULE))
 		return -EBUSY;
 
-	mutex_lock(&bch_register_lock);
-
 	if (!(path = kstrndup(buffer, size, GFP_KERNEL)) ||
 	    !(sb = kmalloc(sizeof(struct cache_sb), GFP_KERNEL)))
 		goto err;
@@ -1946,7 +1947,9 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
 		if (!dc)
 			goto err_close;
 
+		mutex_lock(&bch_register_lock);
 		register_bdev(sb, sb_page, bdev, dc);
+		mutex_unlock(&bch_register_lock);
 	} else {
 		struct cache *ca = kzalloc(sizeof(*ca), GFP_KERNEL);
 		if (!ca)
@@ -1959,7 +1962,6 @@ out:
 		put_page(sb_page);
 	kfree(sb);
 	kfree(path);
-	mutex_unlock(&bch_register_lock);
 	module_put(THIS_MODULE);
 	return ret;
 
-- 
2.7.0