linux-kernel - [PATCH RFC 08/20] kasan: clean up __kasan_mempool_poison

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Message-Id: <c64f3612c31d4898011a22d10d889730a2ed754b.1699297309.git.andreyknvl@google.com>
Date:   Mon,  6 Nov 2023 21:10:17 +0100
From:   andrey.konovalov@...ux.dev
To:     Marco Elver <elver@...gle.com>,
        Alexander Potapenko <glider@...gle.com>
Cc:     Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        kasan-dev@...glegroups.com, Evgenii Stepanov <eugenis@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH RFC 08/20] kasan: clean up __kasan_mempool_poison_object

From: Andrey Konovalov <andreyknvl@...gle.com>

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

Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
---
 mm/kasan/common.c | 19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 6283f0206ef6..7c28d0a5af2c 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -447,27 +447,22 @@ 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)
-- 
2.25.1