Commit 64cc6ae0 authored by Andrea Arcangeli's avatar Andrea Arcangeli Committed by Linus Torvalds

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: default avatarAndrea Arcangeli <>
Acked-by: default avatarRik van Riel <>
Acked-by: default avatarMel Gorman <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent db3eb96f
......@@ -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))
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