[PATCH -next] block: use DEFINE_MUTEX() for mutex lock

[Zheng Yongjun <zhengyongjun3@xxxxxxxxxx>]

mutex lock can be initialized automatically with DEFINE_MUTEX()
rather than explicitly calling mutex_init().

Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
Signed-off-by: Zheng Yongjun <zhengyongjun3@xxxxxxxxxx>
---
 drivers/block/null_blk/main.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index d6c821d48090..b15df944cde2 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -67,7 +67,7 @@ struct nullb_page {
 #define NULLB_PAGE_FREE (MAP_SZ - 2)
 
 static LIST_HEAD(nullb_list);
-static struct mutex lock;
+static DEFINE_MUTEX(lock);
 static int null_major;
 static DEFINE_IDA(nullb_indexes);
 static struct blk_mq_tag_set tag_set;
@@ -1961,8 +1961,6 @@ static int __init null_init(void)
 	if (ret)
 		goto err_tagset;
 
-	mutex_init(&lock);
-
 	null_major = register_blkdev(0, "nullb");
 	if (null_major < 0) {
 		ret = null_major;