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authorAndrea Arcangeli <aarcange@redhat.com>2011-01-13 15:46:42 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2011-01-13 17:32:40 -0800
commit64cc6ae001d70bc59e5f854e6b5678f59110df16 (patch)
tree929358dabd522330ea145755ab0d0d7d27ac85b3 /arch/x86
parentdb3eb96f4e6281b84dd33c8980dacc27f2efe177 (diff)
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>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/mm/gup.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c
index 06f56fcf9a77..269aa53932e0 100644
--- a/arch/x86/mm/gup.c
+++ b/arch/x86/mm/gup.c
@@ -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))