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    SubjectRe: [PATCH] Add debugging boundary check to pfn_to_page
    On 06/08/11 12:18, Eric B Munson wrote:
    > Bugzilla 36192 showed a problem where pages were being accessed outside of
    > a node boundary. It would be helpful in diagnosing this kind of problem to
    > have pfn_to_page complain when a page is accessed outside of the node boundary.
    > This patch adds a new debug config option which adds a WARN_ON in pfn_to_page
    > that will complain when pages are accessed outside of the node boundary.
    >
    > Signed-of-by: Eric B Munson <emunson@mgebm.net>
    > ---
    > include/asm-generic/memory_model.h | 19 +++++++++++++++----
    > lib/Kconfig.debug | 10 ++++++++++
    > 2 files changed, 25 insertions(+), 4 deletions(-)
    >
    > diff --git a/include/asm-generic/memory_model.h b/include/asm-generic/memory_model.h
    > index fb2d63f..a0f1d19 100644
    > --- a/include/asm-generic/memory_model.h
    > +++ b/include/asm-generic/memory_model.h
    > @@ -62,11 +62,22 @@
    > (unsigned long)(__pg - __section_mem_map_addr(__nr_to_section(__sec))); \
    > })
    >
    > -#define __pfn_to_page(pfn) \
    > -({ unsigned long __pfn = (pfn); \
    > - struct mem_section *__sec = __pfn_to_section(__pfn); \
    > - __section_mem_map_addr(__sec) + __pfn; \
    > +#ifdef CONFIG_DEBUG_MEMORY_MODEL
    > +#define __pfn_to_page(pfn) \
    > +({ unsigned long __pfn = (pfn); \
    > + struct mem_section *__sec = __pfn_to_section(__pfn); \
    > + struct page *__page = __section_mem_map_addr(__sec) + __pfn; \
    > + WARN_ON(__page->flags == 0); \
    > + __page; \
    > })
    > +#else
    > +#define __pfn_to_page(pfn) \
    > +({ unsigned long __pfn = (pfn); \
    > + struct mem_section *__sec = __pfn_to_section(__pfn); \
    > + __section_mem_map_addr(__sec) + __pfn; \
    > +})
    > +#endif /* CONFIG_DEBUG_MEMORY_MODEL */
    > +
    > #endif /* CONFIG_FLATMEM/DISCONTIGMEM/SPARSEMEM */
    >
    > #define page_to_pfn __page_to_pfn
    > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
    > index dd373c8..d932cbf 100644
    > --- a/lib/Kconfig.debug
    > +++ b/lib/Kconfig.debug
    > @@ -777,6 +777,16 @@ config DEBUG_MEMORY_INIT
    >
    > If unsure, say Y
    >
    > +config DEBUG_MEMORY_MODEL
    > + bool "Debug memory model" if SPARSEMEM || DISCONTIGMEM
    > + depends on SPARSEMEM || DISCONTIGMEM

    bool <prompt> <expr>
    creates the dependency, so the "depends on" line is not needed.

    > + help
    > + Enable this to check that page accesses are done within node
    > + boundaries. The check will warn each time a page is requested
    > + outside node boundaries.
    > +
    > + If unsure, say N
    > +
    > config DEBUG_LIST
    > bool "Debug linked list manipulation"
    > depends on DEBUG_KERNEL


    --
    ~Randy
    *** Remember to use Documentation/SubmitChecklist when testing your code ***


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