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add pfn_valid_within helper for sub-MAX_ORDER hole detection

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Generally we work under the assumption that memory the mem_map array is
contigious and valid out to MAX_ORDER_NR_PAGES block of pages, ie.  that if we
have validated any page within this MAX_ORDER_NR_PAGES block we need not check
any other.  This is not true when CONFIG_HOLES_IN_ZONE is set and we must
check each and every reference we make from a pfn.

Add a pfn_valid_within() helper which should be used when scanning pages
within a MAX_ORDER_NR_PAGES block when we have already checked the validility
of the block normally with pfn_valid().  This can then be optimised away when
we do not have holes within a MAX_ORDER_NR_PAGES block of pages.

Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Bob Picco <bob.picco@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andy Whitcroft 2007-05-06 14:49:14 -07:00 • committed by Linus Torvalds
parent ac267728f1
commit 14e0729841
2 changed files with 14 additions and 6 deletions
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12
include/linux/mmzone.h
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@ -784,6 +784,18 @@ void sparse_init(void);
void memory_present(int nid, unsigned long start, unsigned long end);
unsigned long __init node_memmap_size_bytes(int, unsigned long, unsigned long);
/*
* If it is possible to have holes within a MAX_ORDER_NR_PAGES, then we
* need to check pfn validility within that MAX_ORDER_NR_PAGES block.
* pfn_valid_within() should be used in this case; we optimise this away
* when we have no holes within a MAX_ORDER_NR_PAGES block.
*/
#ifdef CONFIG_HOLES_IN_ZONE
#define pfn_valid_within(pfn) pfn_valid(pfn)
#else
#define pfn_valid_within(pfn) (1)
#endif
#endif /* !__ASSEMBLY__ */
#endif /* __KERNEL__ */
#endif /* _LINUX_MMZONE_H */