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SubjectRe: [PATCH v3] mm: page_alloc: ignore init_on_free=1 for debug_pagealloc=1
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On 30.03.21 00:25, Sergei Trofimovich wrote:
> On !ARCH_SUPPORTS_DEBUG_PAGEALLOC (like ia64) debug_pagealloc=1
> implies page_poison=on:
>
> if (page_poisoning_enabled() ||
> (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
> debug_pagealloc_enabled()))
> static_branch_enable(&_page_poisoning_enabled);
>
> page_poison=on needs to override init_on_free=1.
>
> Before the change it did not work as expected for the following case:
> - have PAGE_POISONING=y
> - have page_poison unset
> - have !ARCH_SUPPORTS_DEBUG_PAGEALLOC arch (like ia64)
> - have init_on_free=1
> - have debug_pagealloc=1
>
> That way we get both keys enabled:
> - static_branch_enable(&init_on_free);
> - static_branch_enable(&_page_poisoning_enabled);
>
> which leads to poisoned pages returned for __GFP_ZERO pages.
>
> After the change we execute only:
> - static_branch_enable(&_page_poisoning_enabled);
> and ignore init_on_free=1.
>
> Acked-by: Vlastimil Babka <vbabka@suse.cz>
> Fixes: 8db26a3d4735 ("mm, page_poison: use static key more efficiently")
> Cc: <stable@vger.kernel.org>
> CC: Andrew Morton <akpm@linux-foundation.org>
> CC: linux-mm@kvack.org
> CC: David Hildenbrand <david@redhat.com>
> CC: Andrey Konovalov <andreyknvl@gmail.com>
> Link: https://lkml.org/lkml/2021/3/26/443
>
> Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
> ---
> Change since v2:
> - Added 'Fixes:' and 'CC: stable@' suggested by Vlastimil and David
> - Renamed local variable to 'page_poisoning_requested' for
> consistency suggested by David
> - Simplified initialization of page_poisoning_requested suggested
> by David
> - Added 'Acked-by: Vlastimil'
>
> mm/page_alloc.c | 30 +++++++++++++++++-------------
> 1 file changed, 17 insertions(+), 13 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index cfc72873961d..4bb3cdfc47f8 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -764,32 +764,36 @@ static inline void clear_page_guard(struct zone *zone, struct page *page,
> */
> void init_mem_debugging_and_hardening(void)
> {
> + bool page_poisoning_requested = false;
> +
> +#ifdef CONFIG_PAGE_POISONING
> + /*
> + * Page poisoning is debug page alloc for some arches. If
> + * either of those options are enabled, enable poisoning.
> + */
> + if (page_poisoning_enabled() ||
> + (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
> + debug_pagealloc_enabled())) {
> + static_branch_enable(&_page_poisoning_enabled);
> + page_poisoning_requested = true;
> + }
> +#endif
> +
> if (_init_on_alloc_enabled_early) {
> - if (page_poisoning_enabled())
> + if (page_poisoning_requested)
> pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
> "will take precedence over init_on_alloc\n");
> else
> static_branch_enable(&init_on_alloc);
> }
> if (_init_on_free_enabled_early) {
> - if (page_poisoning_enabled())
> + if (page_poisoning_requested)
> pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
> "will take precedence over init_on_free\n");
> else
> static_branch_enable(&init_on_free);
> }
>
> -#ifdef CONFIG_PAGE_POISONING
> - /*
> - * Page poisoning is debug page alloc for some arches. If
> - * either of those options are enabled, enable poisoning.
> - */
> - if (page_poisoning_enabled() ||
> - (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
> - debug_pagealloc_enabled()))
> - static_branch_enable(&_page_poisoning_enabled);
> -#endif
> -
> #ifdef CONFIG_DEBUG_PAGEALLOC
> if (!debug_pagealloc_enabled())
> return;
>

Thanks!

Reviewed-by: David Hildenbrand <david@redhat.com>

--
Thanks,

David / dhildenb

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