kasan: clean up __kasan_mempool_poison_object

Reorganize the code and reword the comment in
__kasan_mempool_poison_object to improve the code readability.

Link: https://lkml.kernel.org/r/4f6fc8840512286c1a96e16e86901082c671677d.1703024586.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Alexander Lobakin <alobakin@pm.me>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Breno Leitao <leitao@debian.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 7ebc001d0fcd2c5030718743d6c75dfa998710cb..3f4a1ed69e03ab2643cf24f773c0cba9a0c82999 100644 (file)
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -457,27 +457,22 @@ void __kasan_mempool_unpoison_pages(struct page *page, unsigned int order,
 
 bool __kasan_mempool_poison_object(void *ptr, unsigned long ip)
 {
-       struct folio *folio;
-
-       folio = virt_to_folio(ptr);
+       struct folio *folio = virt_to_folio(ptr);
+       struct slab *slab;
 
        /*
-        * Even though this function is only called for kmem_cache_alloc and
-        * kmalloc backed mempool allocations, those allocations can still be
-        * !PageSlab() when the size provided to kmalloc is larger than
-        * KMALLOC_MAX_SIZE, and kmalloc falls back onto page_alloc.
+        * This function can be called for large kmalloc allocation that get
+        * their memory from page_alloc. Thus, the folio might not be a slab.
         */
        if (unlikely(!folio_test_slab(folio))) {
                if (check_page_allocation(ptr, ip))
                        return false;
                kasan_poison(ptr, folio_size(folio), KASAN_PAGE_FREE, false);
                return true;
-       } else {
-               struct slab *slab = folio_slab(folio);
-
-               return !____kasan_slab_free(slab->slab_cache, ptr, ip,
-                                               false, false);
        }
+
+       slab = folio_slab(folio);
+       return !____kasan_slab_free(slab->slab_cache, ptr, ip, false, false);
 }
 
 void __kasan_mempool_unpoison_object(void *ptr, size_t size, unsigned long ip)