From: Hugh Dickins <hughd@xxxxxxxxxx> Subject: mm: page_vma_mapped_walk(): use pmde for *pvmw->pmd page_vma_mapped_walk() cleanup: re-evaluate pmde after taking lock, then use it in subsequent tests, instead of repeatedly dereferencing pointer. Link: https://lkml.kernel.org/r/53fbc9d-891e-46b2-cb4b-468c3b19238e@xxxxxxxxxx Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx> Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Reviewed-by: Peter Xu <peterx@xxxxxxxxxx> Cc: Alistair Popple <apopple@xxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Ralph Campbell <rcampbell@xxxxxxxxxx> Cc: Wang Yugui <wangyugui@xxxxxxxxxxxx> Cc: Will Deacon <will@xxxxxxxxxx> Cc: Yang Shi <shy828301@xxxxxxxxx> Cc: Zi Yan <ziy@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/page_vma_mapped.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) --- a/mm/page_vma_mapped.c~mm-page_vma_mapped_walk-use-pmde-for-pvmw-pmd +++ a/mm/page_vma_mapped.c @@ -191,18 +191,19 @@ restart: pmde = READ_ONCE(*pvmw->pmd); if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde)) { pvmw->ptl = pmd_lock(mm, pvmw->pmd); - if (likely(pmd_trans_huge(*pvmw->pmd))) { + pmde = *pvmw->pmd; + if (likely(pmd_trans_huge(pmde))) { if (pvmw->flags & PVMW_MIGRATION) return not_found(pvmw); - if (pmd_page(*pvmw->pmd) != page) + if (pmd_page(pmde) != page) return not_found(pvmw); return true; - } else if (!pmd_present(*pvmw->pmd)) { + } else if (!pmd_present(pmde)) { if (thp_migration_supported()) { if (!(pvmw->flags & PVMW_MIGRATION)) return not_found(pvmw); - if (is_migration_entry(pmd_to_swp_entry(*pvmw->pmd))) { - swp_entry_t entry = pmd_to_swp_entry(*pvmw->pmd); + if (is_migration_entry(pmd_to_swp_entry(pmde))) { + swp_entry_t entry = pmd_to_swp_entry(pmde); if (migration_entry_to_page(entry) != page) return not_found(pvmw); _
