jbd2: Convert jbd2_slab_create_sem to mutex

jbd2_slab_create_sem is used as a mutex, so make it one.

[ akpm muttered: We may as well make it local to
jbd2_journal_create_slab() also. ]
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Ted Ts'o <tytso@mit.edu>
Cc: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <alpine.LFD.2.00.1010162231480.2496@localhost6.localdomain6>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

fs/jbd2/journal.c

@@ -1838,7 +1838,6 @@ size_t journal_tag_bytes(journal_t *journal)
  */
 #define JBD2_MAX_SLABS 8
 static struct kmem_cache *jbd2_slab[JBD2_MAX_SLABS];
-static DECLARE_MUTEX(jbd2_slab_create_sem);
 
 static const char *jbd2_slab_names[JBD2_MAX_SLABS] = {
 	"jbd2_1k", "jbd2_2k", "jbd2_4k", "jbd2_8k",
@@ -1859,6 +1858,7 @@ static void jbd2_journal_destroy_slabs(void)
 
 static int jbd2_journal_create_slab(size_t size)
 {
+	static DEFINE_MUTEX(jbd2_slab_create_mutex);
 	int i = order_base_2(size) - 10;
 	size_t slab_size;
 
@@ -1870,16 +1870,16 @@ static int jbd2_journal_create_slab(size_t size)
 
 	if (unlikely(i < 0))
 		i = 0;
-	down(&jbd2_slab_create_sem);
+	mutex_lock(&jbd2_slab_create_mutex);
 	if (jbd2_slab[i]) {
-		up(&jbd2_slab_create_sem);
+		mutex_unlock(&jbd2_slab_create_mutex);
 		return 0;	/* Already created */
 	}
 
 	slab_size = 1 << (i+10);
 	jbd2_slab[i] = kmem_cache_create(jbd2_slab_names[i], slab_size,
 					 slab_size, 0, NULL);
-	up(&jbd2_slab_create_sem);
+	mutex_unlock(&jbd2_slab_create_mutex);
 	if (!jbd2_slab[i]) {
 		printk(KERN_EMERG "JBD2: no memory for jbd2_slab cache\n");
 		return -ENOMEM;