When splitting a huge migrating PMD, we'll transfer the soft dirty bit from the huge page to the small pages. However we're possibly using a wrong data since when fetching the bit we're using pmd_soft_dirty() upon a migration entry. Fix it up.
CC: Andrea Arcangeli <[email protected]> CC: Andrew Morton <[email protected]> CC: "Kirill A. Shutemov" <[email protected]> CC: Matthew Wilcox <[email protected]> CC: Michal Hocko <[email protected]> CC: Dave Jiang <[email protected]> CC: "Aneesh Kumar K.V" <[email protected]> CC: Souptick Joarder <[email protected]> CC: Konstantin Khlebnikov <[email protected]> CC: [email protected] CC: [email protected] Signed-off-by: Peter Xu <[email protected]> --- I noticed this during code reading. Only compile tested. I'm sending a patch directly for review comments since it's relatively straightforward and not easy to test. Please have a look, thanks. --- mm/huge_memory.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index f2d19e4fe854..fb0787c3dd3b 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2161,7 +2161,10 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, SetPageDirty(page); write = pmd_write(old_pmd); young = pmd_young(old_pmd); - soft_dirty = pmd_soft_dirty(old_pmd); + if (unlikely(pmd_migration)) + soft_dirty = pmd_swp_soft_dirty(old_pmd); + else + soft_dirty = pmd_soft_dirty(old_pmd); /* * Withdraw the table only after we mark the pmd entry invalid. -- 2.17.1
