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um: Implement a custom pte_same() function

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commit f15b9000eb upstream.

UML uses the _PAGE_NEWPAGE flag to mark pages which are not jet
installed on the host side using mmap().
pte_same() has to ignore this flag, otherwise unuse_pte_range()
is unable to unuse the page because two identical
page tables entries with different _PAGE_NEWPAGE flags would not
match and swapoff() would never return.

Analyzed-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Richard Weinberger 2012-04-14 17:29:30 +02:00 committed by Greg Kroah-Hartman
parent ec58eb2b33
commit a044b505aa
1 changed files with 6 additions and 0 deletions
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6
arch/um/include/asm/pgtable.h
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@ -271,6 +271,12 @@ static inline void set_pte(pte_t *pteptr, pte_t pteval)
}
#define set_pte_at(mm,addr,ptep,pteval) set_pte(ptep,pteval)
#define __HAVE_ARCH_PTE_SAME
static inline int pte_same(pte_t pte_a, pte_t pte_b)
{
return !((pte_val(pte_a) ^ pte_val(pte_b)) & ~_PAGE_NEWPAGE);
}
/*
* Conversion functions: convert a page and protection to a page entry,
* and a page entry and page directory to the page they refer to.