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thp: bail out gup_fast on splitting pmd 

Force gup_fast to take the slow path and block if the pmd is splitting,
not only if it's none.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrea Arcangeli 2011-01-13 15:46:42 -08:00 committed by Linus Torvalds
parent db3eb96f4e
commit 64cc6ae001
1 changed files with 12 additions and 1 deletions
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13
arch/x86/mm/gup.c
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@ -160,7 +160,18 @@ static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
pmd_t pmd = *pmdp;
next = pmd_addr_end(addr, end);
if (pmd_none(pmd))
/*
* The pmd_trans_splitting() check below explains why
* pmdp_splitting_flush has to flush the tlb, to stop
* this gup-fast code from running while we set the
* splitting bit in the pmd. Returning zero will take
* the slow path that will call wait_split_huge_page()
* if the pmd is still in splitting state. gup-fast
* can't because it has irq disabled and
* wait_split_huge_page() would never return as the
* tlb flush IPI wouldn't run.
*/
if (pmd_none(pmd) || pmd_trans_splitting(pmd))
return 0;
if (unlikely(pmd_large(pmd))) {
if (!gup_huge_pmd(pmd, addr, next, write, pages, nr))