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    SubjectRe: [PATCH 1/4] mm: introduce debug_pagealloc_map_pages() helper
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    On 25.10.20 11:15, Mike Rapoport wrote:
    > From: Mike Rapoport <rppt@linux.ibm.com>
    >
    > When CONFIG_DEBUG_PAGEALLOC is enabled, it unmaps pages from the
    > kernel direct mapping after free_pages(). The pages than need to be
    > mapped back before they could be used. Theese mapping operations use
    > __kernel_map_pages() guarded with with debug_pagealloc_enabled().
    >
    > The only place that calls __kernel_map_pages() without checking
    > whether DEBUG_PAGEALLOC is enabled is the hibernation code that
    > presumes availability of this function when ARCH_HAS_SET_DIRECT_MAP
    > is set. Still, on arm64, __kernel_map_pages() will bail out when
    > DEBUG_PAGEALLOC is not enabled but set_direct_map_invalid_noflush()
    > may render some pages not present in the direct map and hibernation
    > code won't be able to save such pages.
    >
    > To make page allocation debugging and hibernation interaction more
    > robust, the dependency on DEBUG_PAGEALLOC or ARCH_HAS_SET_DIRECT_MAP
    > has to be made more explicit.
    >
    > Start with combining the guard condition and the call to
    > __kernel_map_pages() into a single debug_pagealloc_map_pages()
    > function to emphasize that __kernel_map_pages() should not be called
    > without DEBUG_PAGEALLOC and use this new function to map/unmap pages
    > when page allocation debug is enabled.
    >
    > As the only remaining user of kernel_map_pages() is the hibernation
    > code, mode that function into kernel/power/snapshot.c closer to a
    > caller.

    s/mode/move/

    >
    > Signed-off-by: Mike Rapoport <rppt@linux.ibm.com> ---
    > include/linux/mm.h | 16 +++++++--------- kernel/power/snapshot.c
    > | 11 +++++++++++ mm/memory_hotplug.c | 3 +-- mm/page_alloc.c
    > | 6 ++---- mm/slab.c | 8 +++----- 5 files changed, 24
    > insertions(+), 20 deletions(-)
    >
    > diff --git a/include/linux/mm.h b/include/linux/mm.h index
    > ef360fe70aaf..14e397f3752c 100644 --- a/include/linux/mm.h +++
    > b/include/linux/mm.h @@ -2927,21 +2927,19 @@ static inline bool
    > debug_pagealloc_enabled_static(void) #if
    > defined(CONFIG_DEBUG_PAGEALLOC) ||
    > defined(CONFIG_ARCH_HAS_SET_DIRECT_MAP) extern void
    > __kernel_map_pages(struct page *page, int numpages, int enable);
    >
    > -/* - * When called in DEBUG_PAGEALLOC context, the call should most
    > likely be - * guarded by debug_pagealloc_enabled() or
    > debug_pagealloc_enabled_static() - */ -static inline void
    > -kernel_map_pages(struct page *page, int numpages, int enable)
    > +static inline void debug_pagealloc_map_pages(struct page *page, +
    > int numpages, int enable) { - __kernel_map_pages(page, numpages,
    > enable); + if (debug_pagealloc_enabled_static()) +
    > __kernel_map_pages(page, numpages, enable); } + #ifdef
    > CONFIG_HIBERNATION extern bool kernel_page_present(struct page
    > *page); #endif /* CONFIG_HIBERNATION */ #else /*
    > CONFIG_DEBUG_PAGEALLOC || CONFIG_ARCH_HAS_SET_DIRECT_MAP */ -static
    > inline void -kernel_map_pages(struct page *page, int numpages, int
    > enable) {} +static inline void debug_pagealloc_map_pages(struct page
    > *page, + int numpages, int enable) {} #ifdef
    > CONFIG_HIBERNATION static inline bool kernel_page_present(struct page
    > *page) { return true; } #endif /* CONFIG_HIBERNATION */ diff --git
    > a/kernel/power/snapshot.c b/kernel/power/snapshot.c index
    > 46b1804c1ddf..fa499466f645 100644 --- a/kernel/power/snapshot.c +++
    > b/kernel/power/snapshot.c @@ -76,6 +76,17 @@ static inline void
    > hibernate_restore_protect_page(void *page_address) {} static inline
    > void hibernate_restore_unprotect_page(void *page_address) {} #endif
    > /* CONFIG_STRICT_KERNEL_RWX && CONFIG_ARCH_HAS_SET_MEMORY */
    >
    > +#if defined(CONFIG_DEBUG_PAGEALLOC) ||
    > defined(CONFIG_ARCH_HAS_SET_DIRECT_MAP) +static inline void
    > +kernel_map_pages(struct page *page, int numpages, int enable) +{ +
    > __kernel_map_pages(page, numpages, enable); +} +#else +static inline
    > void +kernel_map_pages(struct page *page, int numpages, int enable)
    > {} +#endif +

    That change should go into a separate patch.


    For the debug_pagealloc_map_pages() parts

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


    --
    Thanks,

    David / dhildenb

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