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Date: Mon, 26 Oct 2020 12:05:13 +0100
From: David Hildenbrand <david@...hat.com>
To: Mike Rapoport <rppt@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>
Cc: Albert Ou <aou@...s.berkeley.edu>,
Andy Lutomirski <luto@...nel.org>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Borislav Petkov <bp@...en8.de>,
Catalin Marinas <catalin.marinas@....com>,
Christian Borntraeger <borntraeger@...ibm.com>,
Christoph Lameter <cl@...ux.com>,
"David S. Miller" <davem@...emloft.net>,
Dave Hansen <dave.hansen@...ux.intel.com>,
David Rientjes <rientjes@...gle.com>,
"Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
"H. Peter Anvin" <hpa@...or.com>,
Heiko Carstens <hca@...ux.ibm.com>,
Ingo Molnar <mingo@...hat.com>,
Joonsoo Kim <iamjoonsoo.kim@....com>,
"Kirill A. Shutemov" <kirill@...temov.name>,
Len Brown <len.brown@...el.com>,
Michael Ellerman <mpe@...erman.id.au>,
Mike Rapoport <rppt@...ux.ibm.com>,
Palmer Dabbelt <palmer@...belt.com>,
Paul Mackerras <paulus@...ba.org>,
Paul Walmsley <paul.walmsley@...ive.com>,
Pavel Machek <pavel@....cz>, Pekka Enberg <penberg@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
"Rafael J. Wysocki" <rjw@...ysocki.net>,
Thomas Gleixner <tglx@...utronix.de>,
Vasily Gorbik <gor@...ux.ibm.com>,
Will Deacon <will@...nel.org>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, linux-pm@...r.kernel.org,
linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
linuxppc-dev@...ts.ozlabs.org, sparclinux@...r.kernel.org,
x86@...nel.org
Subject: Re: [PATCH 1/4] mm: introduce debug_pagealloc_map_pages() helper
On 25.10.20 11:15, Mike Rapoport wrote:
> From: Mike Rapoport <rppt@...ux.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@...ux.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@...hat.com>
--
Thanks,
David / dhildenb
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