diff options
| -rw-r--r-- | arch/x86/mm/gup.c | 13 |
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)) |