linux-kernel - Re: [PATCH v3 3/5] kernel/power: allow hibernation with page

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Date:   Fri, 13 Nov 2020 13:10:05 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Vlastimil Babka <vbabka@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Alexander Potapenko <glider@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Michal Hocko <mhocko@...nel.org>,
        Mateusz Nosek <mateusznosek0@...il.com>,
        Laura Abbott <labbott@...nel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH v3 3/5] kernel/power: allow hibernation with page_poison
 sanity checking

On 13.11.20 11:40, Vlastimil Babka wrote:
> Page poisoning used to be incompatible with hibernation, as the state of
> poisoned pages was lost after resume, thus enabling CONFIG_HIBERNATION forces
> CONFIG_PAGE_POISONING_NO_SANITY. For the same reason, the poisoning with zeroes
> variant CONFIG_PAGE_POISONING_ZERO used to disable hibernation. The latter
> restriction was removed by commit 1ad1410f632d ("PM / Hibernate: allow
> hibernation with PAGE_POISONING_ZERO") and similarly for init_on_free by commit
> 18451f9f9e58 ("PM: hibernate: fix crashes with init_on_free=1") by making sure
> free pages are cleared after resume.
> 
> We can use the same mechanism to instead poison free pages with PAGE_POISON
> after resume. This covers both zero and 0xAA patterns. Thus we can remove the
> Kconfig restriction that disables page poison sanity checking when hibernation
> is enabled.
> 
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com> # for hibernation
> ---
>   include/linux/mm.h       |  1 +
>   kernel/power/hibernate.c |  2 +-
>   kernel/power/power.h     |  2 +-
>   kernel/power/snapshot.c  | 14 +++++++++++---
>   mm/Kconfig.debug         |  1 -
>   5 files changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 5ab5358be2b3..b15000085ff2 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2891,6 +2891,7 @@ static inline void kernel_unpoison_pages(struct page *page, int numpages)
>   #else
>   static inline bool page_poisoning_enabled(void) { return false; }
>   static inline bool page_poisoning_enabled_static(void) { return false; }
> +static inline void __kernel_poison_pages(struct page *page, int nunmpages) { }
>   static inline void kernel_poison_pages(struct page *page, int numpages) { }
>   static inline void kernel_unpoison_pages(struct page *page, int numpages) { }
>   #endif
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index d5d48404db37..559acef3fddb 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -329,7 +329,7 @@ static int create_image(int platform_mode)
>   
>   	if (!in_suspend) {
>   		events_check_enabled = false;
> -		clear_free_pages();
> +		clear_or_poison_free_pages();
>   	}
>   
>   	platform_leave(platform_mode);
> diff --git a/kernel/power/power.h b/kernel/power/power.h
> index 24f12d534515..778bf431ec02 100644
> --- a/kernel/power/power.h
> +++ b/kernel/power/power.h
> @@ -106,7 +106,7 @@ extern int create_basic_memory_bitmaps(void);
>   extern void free_basic_memory_bitmaps(void);
>   extern int hibernate_preallocate_memory(void);
>   
> -extern void clear_free_pages(void);
> +extern void clear_or_poison_free_pages(void);
>   
>   /**
>    *	Auxiliary structure used for reading the snapshot image data and
> diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
> index af534982062d..64b7aab9aee4 100644
> --- a/kernel/power/snapshot.c
> +++ b/kernel/power/snapshot.c
> @@ -1178,7 +1178,15 @@ void free_basic_memory_bitmaps(void)
>   	pr_debug("Basic memory bitmaps freed\n");
>   }
>   
> -void clear_free_pages(void)
> +static void clear_or_poison_free_page(struct page *page)
> +{
> +	if (page_poisoning_enabled_static())
> +		__kernel_poison_pages(page, 1);
> +	else if (want_init_on_free())
> +		clear_highpage(page);
> +}
> +
> +void clear_or_poison_free_pages(void)
>   {
>   	struct memory_bitmap *bm = free_pages_map;
>   	unsigned long pfn;
> @@ -1186,12 +1194,12 @@ void clear_free_pages(void)
>   	if (WARN_ON(!(free_pages_map)))
>   		return;
>   
> -	if (IS_ENABLED(CONFIG_PAGE_POISONING_ZERO) || want_init_on_free()) {
> +	if (page_poisoning_enabled() || want_init_on_free()) {

Any reason why not to use the static version here?

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


-- 
Thanks,

David / dhildenb