lib/test_meminit.c: fix -Wmaybe-uninitialized false positive

The conditional logic is too complicated for the compiler to fully
comprehend:

  lib/test_meminit.c: In function 'test_meminit_init':
  lib/test_meminit.c:236:5: error: 'buf_copy' may be used uninitialized in this function [-Werror=maybe-uninitialized]
       kfree(buf_copy);
       ^~~~~~~~~~~~~~~
  lib/test_meminit.c:201:14: note: 'buf_copy' was declared here

Simplify it by splitting out the non-rcu section.

Link: http://lkml.kernel.org/r/20190617131210.2190280-1-arnd@arndb.de
Fixes: af734ee6ec85 ("lib: introduce test_meminit module")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/test_meminit.c

@@ -208,11 +208,16 @@ static int __init do_kmem_cache_size(size_t size, bool want_ctor,
 		/* Check that buf is zeroed, if it must be. */
 		fail = check_buf(buf, size, want_ctor, want_rcu, want_zero);
 		fill_with_garbage_skip(buf, size, want_ctor ? CTOR_BYTES : 0);
+
+		if (!want_rcu) {
+			kmem_cache_free(c, buf);
+			continue;
+		}
+
 		/*
 		 * If this is an RCU cache, use a critical section to ensure we
 		 * can touch objects after they're freed.
 		 */
-		if (want_rcu) {
 		rcu_read_lock();
 		/*
 		 * Copy the buffer to check that it's not wiped on
@@ -221,9 +226,7 @@ static int __init do_kmem_cache_size(size_t size, bool want_ctor,
 		buf_copy = kmalloc(size, GFP_KERNEL);
 		if (buf_copy)
 			memcpy(buf_copy, buf, size);
-		}
-		kmem_cache_free(c, buf);
-		if (want_rcu) {
+
 		/*
 		 * Check that |buf| is intact after kmem_cache_free().
 		 * |want_zero| is false, because we wrote garbage to
@@ -237,7 +240,6 @@ static int __init do_kmem_cache_size(size_t size, bool want_ctor,
 		}
 		rcu_read_unlock();
 	}
-	}
 	kmem_cache_destroy(c);
 
 	*total_failures += fail;