Re: [RFC PATCH 25/32] mm/kfence: Convert kfence_guarded_alloc() to struct slab

[Marco Elver <elver@google.com>]

On Tue, 16 Nov 2021 at 01:16, Vlastimil Babka <vbabka@suse.cz> wrote:
> The function sets some fields that are being moved from struct page to struct
> slab so it needs to be converted.
>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> Cc: Alexander Potapenko <glider@google.com>
> Cc: Marco Elver <elver@google.com>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Cc: <kasan-dev@googlegroups.com>

It looks sane. I ran kfence_test with both slab and slub, and all passes:

Tested-by: Marco Elver <elver@google.com>

But should there be other major changes, we should re-test.

Thanks,
-- Marco

> ---
>  mm/kfence/core.c        | 12 ++++++------
>  mm/kfence/kfence_test.c |  6 +++---
>  2 files changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/mm/kfence/core.c b/mm/kfence/core.c
> index 09945784df9e..4eb60cf5ff8b 100644
> --- a/mm/kfence/core.c
> +++ b/mm/kfence/core.c
> @@ -360,7 +360,7 @@ static void *kfence_guarded_alloc(struct kmem_cache *cache, size_t size, gfp_t g
>  {
>         struct kfence_metadata *meta = NULL;
>         unsigned long flags;
> -       struct page *page;
> +       struct slab *slab;
>         void *addr;
>
>         /* Try to obtain a free object. */
> @@ -424,13 +424,13 @@ static void *kfence_guarded_alloc(struct kmem_cache *cache, size_t size, gfp_t g
>
>         alloc_covered_add(alloc_stack_hash, 1);
>
> -       /* Set required struct page fields. */
> -       page = virt_to_page(meta->addr);
> -       page->slab_cache = cache;
> +       /* Set required slab fields. */
> +       slab = virt_to_slab((void *)meta->addr);
> +       slab->slab_cache = cache;
>         if (IS_ENABLED(CONFIG_SLUB))
> -               page->objects = 1;
> +               slab->objects = 1;
>         if (IS_ENABLED(CONFIG_SLAB))
> -               page->s_mem = addr;
> +               slab->s_mem = addr;
>
>         /* Memory initialization. */
>         for_each_canary(meta, set_canary_byte);
> diff --git a/mm/kfence/kfence_test.c b/mm/kfence/kfence_test.c
> index f7276711d7b9..a22b1af85577 100644
> --- a/mm/kfence/kfence_test.c
> +++ b/mm/kfence/kfence_test.c
> @@ -282,7 +282,7 @@ static void *test_alloc(struct kunit *test, size_t size, gfp_t gfp, enum allocat
>                         alloc = kmalloc(size, gfp);
>
>                 if (is_kfence_address(alloc)) {
> -                       struct page *page = virt_to_head_page(alloc);
> +                       struct slab *slab = virt_to_slab(alloc);
>                         struct kmem_cache *s = test_cache ?:
>                                         kmalloc_caches[kmalloc_type(GFP_KERNEL)][__kmalloc_index(size, false)];
>
> @@ -291,8 +291,8 @@ static void *test_alloc(struct kunit *test, size_t size, gfp_t gfp, enum allocat
>                          * even for KFENCE objects; these are required so that
>                          * memcg accounting works correctly.
>                          */
> -                       KUNIT_EXPECT_EQ(test, obj_to_index(s, page_slab(page), alloc), 0U);
> -                       KUNIT_EXPECT_EQ(test, objs_per_slab(s, page_slab(page)), 1);
> +                       KUNIT_EXPECT_EQ(test, obj_to_index(s, slab, alloc), 0U);
> +                       KUNIT_EXPECT_EQ(test, objs_per_slab(s, slab), 1);
>
>                         if (policy == ALLOCATE_ANY)
>                                 return alloc;
> --
> 2.33.1