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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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