linux-kernel - Re: [PATCH v2 3/5] kernel/power: allow hibernation with page

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Date:   Thu, 5 Nov 2020 19:36:55 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Alexander Potapenko <glider@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Michal Hocko <mhocko@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        Mateusz Nosek <mateusznosek0@...il.com>,
        Laura Abbott <labbott@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v2 3/5] kernel/power: allow hibernation with page_poison
 sanity checking

On Tue, Nov 3, 2020 at 4:24 PM Vlastimil Babka <vbabka@...e.cz> 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>
> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> Cc: Len Brown <len.brown@...el.com>
> Cc: Pavel Machek <pavel@....cz>
> Cc: <linux-pm@...r.kernel.org>

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

for the hibernation part and I'm assuming that this patch will be
routed through the mm tree.

> ---
>  kernel/power/hibernate.c |  2 +-
>  kernel/power/power.h     |  2 +-
>  kernel/power/snapshot.c  | 14 ++++++++++----
>  mm/Kconfig.debug         |  1 -
>  4 files changed, 12 insertions(+), 7 deletions(-)
>
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index 2fc7d509a34f..da0b41914177 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -326,7 +326,7 @@ 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 46b1804c1ddf..6b1c84afa891 100644
> --- a/kernel/power/snapshot.c
> +++ b/kernel/power/snapshot.c
> @@ -1144,7 +1144,7 @@ void free_basic_memory_bitmaps(void)
>         pr_debug("Basic memory bitmaps freed\n");
>  }
>
> -void clear_free_pages(void)
> +void clear_or_poison_free_pages(void)
>  {
>         struct memory_bitmap *bm = free_pages_map;
>         unsigned long pfn;
> @@ -1152,12 +1152,18 @@ 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()) {
>                 memory_bm_position_reset(bm);
>                 pfn = memory_bm_next_pfn(bm);
>                 while (pfn != BM_END_OF_MAP) {
> -                       if (pfn_valid(pfn))
> -                               clear_highpage(pfn_to_page(pfn));
> +                       if (pfn_valid(pfn)) {
> +                               struct page *page = pfn_to_page(pfn);
> +                               if (page_poisoning_enabled_static())
> +                                       kernel_poison_pages(page, 1);
> +                               else if (want_init_on_free())
> +                                       clear_highpage(page);
> +
> +                       }
>
>                         pfn = memory_bm_next_pfn(bm);
>                 }
> diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
> index 864f129f1937..c57786ad5be9 100644
> --- a/mm/Kconfig.debug
> +++ b/mm/Kconfig.debug
> @@ -64,7 +64,6 @@ config PAGE_OWNER
>
>  config PAGE_POISONING
>         bool "Poison pages after freeing"
> -       select PAGE_POISONING_NO_SANITY if HIBERNATION
>         help
>           Fill the pages with poison patterns after free_pages() and verify
>           the patterns before alloc_pages. The filling of the memory helps
> --
> 2.29.1
>