jbd2: use kmem_cache_zalloc instead of kmem_cache_alloc/memset

The jbd2_alloc_handle() function is only called by new_handle().  So
this commit uses kmem_cache_zalloc() instead of
kmem_cache_alloc()/memset().
Signed-off-by: NZheng Liu <wenqing.lz@taobao.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

fs/jbd2/transaction.c

@@ -332,7 +332,6 @@ static handle_t *new_handle(int nblocks)
 	handle_t *handle = jbd2_alloc_handle(GFP_NOFS);
 	if (!handle)
 		return NULL;
-	memset(handle, 0, sizeof(*handle));
 	handle->h_buffer_credits = nblocks;
 	handle->h_ref = 1;
 

include/linux/jbd2.h

@@ -1145,7 +1145,7 @@ extern struct kmem_cache *jbd2_handle_cache;
 
 static inline handle_t *jbd2_alloc_handle(gfp_t gfp_flags)
 {
-	return kmem_cache_alloc(jbd2_handle_cache, gfp_flags);
+	return kmem_cache_zalloc(jbd2_handle_cache, gfp_flags);
 }
 
 static inline void jbd2_free_handle(handle_t *handle)