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    SubjectRe: [PATCH 03/31] mm: expose gfp_to_alloc_flags()
    On Thursday October 1, rientjes@google.com wrote:
    > On Thu, 1 Oct 2009, Suresh Jayaraman wrote:
    >
    > > From: Peter Zijlstra <a.p.zijlstra@chello.nl>
    > >
    > > Expose the gfp to alloc_flags mapping, so we can use it in other parts
    > > of the vm.
    > >
    > > Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    > > Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
    >
    > Nack, these flags are internal to the page allocator and exporting them to
    > generic VM code is unnecessary.
    >
    > The only bit you actually use in your patchset is ALLOC_NO_WATERMARKS to
    > determine whether a particular allocation can use memory reserves. I'd
    > suggest adding a bool function that returns whether the current context is
    > given access to reserves including your new __GFP_MEMALLOC flag and
    > exporting that instead.

    That sounds like a very appropriate suggestion, thanks.

    So something like this?
    Then change every occurrence of
    + if (!(gfp_to_alloc_flags(gfpflags) & ALLOC_NO_WATERMARKS))
    to
    + if (!(gfp_has_no_watermarks(gfpflags)))

    ??

    Thanks,
    NeilBrown



    diff --git a/mm/internal.h b/mm/internal.h
    index 22ec8d2..7ff78d6 100644
    --- a/mm/internal.h
    +++ b/mm/internal.h
    @@ -195,6 +195,8 @@ static inline struct page *mem_map_next(struct page *iter,
    #define __paginginit __init
    #endif

    +int gfp_has_no_watermarks(gfp_t gfp_mask);
    +
    /* Memory initialisation debug and verification */
    enum mminit_level {
    MMINIT_WARNING,
    diff --git a/mm/page_alloc.c b/mm/page_alloc.c
    index bf72055..4b4292a 100644
    --- a/mm/page_alloc.c
    +++ b/mm/page_alloc.c
    @@ -1782,6 +1782,11 @@ gfp_to_alloc_flags(gfp_t gfp_mask)
    return alloc_flags;
    }

    +int gfp_has_no_watermarks(gfp_t gfp_mask)
    +{
    + return (gfp_to_alloc_flags(gfp_mask) & ALLOC_NO_WATERMARKS);
    +}
    +
    static inline struct page *
    __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
    struct zonelist *zonelist, enum zone_type high_zoneidx,

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