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SubjectRe: [PATCH v3 3/5] kernel/power: allow hibernation with page_poison sanity checking
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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@suse.cz>
> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.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@redhat.com>


--
Thanks,

David / dhildenb

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