mm/swap_slots.c: simplify alloc_swap_slot_cache()

Patch series "clean up some functions in mm/swap_slots.c".

When I studied the code of mm/swap_slots.c, I found some places can be
improved.

This patch (of 3):

Both "slots" and "slots_ret" are only need to be freed when cache already
allocated.  Make them closer, seems more clear.

No functional change.

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Tim Chen <tim.c.chen@linux.intel.com>
Link: http://lkml.kernel.org/r/20200430061143.450-1-thunder.leizhen@huawei.com
Link: http://lkml.kernel.org/r/20200430061143.450-2-thunder.leizhen@huawei.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/swap_slots.c

@@ -136,9 +136,16 @@ static int alloc_swap_slot_cache(unsigned int cpu)
 
 	mutex_lock(&swap_slots_cache_mutex);
 	cache = &per_cpu(swp_slots, cpu);
-	if (cache->slots || cache->slots_ret)
+	if (cache->slots || cache->slots_ret) {
 		/* cache already allocated */
-		goto out;
+		mutex_unlock(&swap_slots_cache_mutex);
+
+		kvfree(slots);
+		kvfree(slots_ret);
+
+		return 0;
+	}
+
 	if (!cache->lock_initialized) {
 		mutex_init(&cache->alloc_lock);
 		spin_lock_init(&cache->free_lock);
@@ -155,15 +162,8 @@ static int alloc_swap_slot_cache(unsigned int cpu)
 	 */
 	mb();
 	cache->slots = slots;
-	slots = NULL;
 	cache->slots_ret = slots_ret;
-	slots_ret = NULL;
-out:
 	mutex_unlock(&swap_slots_cache_mutex);
-	if (slots)
-		kvfree(slots);
-	if (slots_ret)
-		kvfree(slots_ret);
 	return 0;
 }