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mm/gup: Move page table entry dereference into helper function

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This is a preparation patch for the transition of x86 to the generic GUP_fast()
implementation.

On x86 PAE, page table entry is larger than sizeof(long) and we would
need to provide a helper that can read the entry atomically.

Signed-off-by: Kirill A. Shutemov <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Aneesh Kumar K . V <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Dann Frazier <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Steve Capper <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Kirill A. Shutemov 2017-03-16 18:26:51 +03:00 • committed by Ingo Molnar
commit 0005d20b2f
1 changed files with 12 additions and 8 deletions
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20
mm/gup.c
View file

@ -1189,6 +1189,17 @@ struct page *get_dump_page(unsigned long addr)
*/
#ifdef CONFIG_HAVE_GENERIC_RCU_GUP
#ifndef gup_get_pte
/*
* We assume that the PTE can be read atomically. If this is not the case for
* your architecture, please provide the helper.
*/
static inline pte_t gup_get_pte(pte_t *ptep)
{
return READ_ONCE(*ptep);
}
#endif
#ifdef __HAVE_ARCH_PTE_SPECIAL
static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
int write, struct page **pages, int *nr)
@ -1198,14 +1209,7 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
ptem = ptep = pte_offset_map(&pmd, addr);
do {
/*
* In the line below we are assuming that the pte can be read
* atomically. If this is not the case for your architecture,
* please wrap this in a helper function!
*
* for an example see gup_get_pte in arch/x86/mm/gup.c
*/
pte_t pte = READ_ONCE(*ptep);
pte_t pte = gup_get_pte(ptep);
struct page *head, *page;
/*