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@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Wang Yugui <wangyugui@e16-tech.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 7c05046..8f972b0 100644 (file)
--- a/mm/page_vma_mapped.c
+++ b/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);