[PATCH 5.4 58/71] mm: page_vma_mapped_walk(): use pmde for *pvmw->pmd

From: Sasha Levin
Date: Mon Jun 28 2021 - 10:50:01 EST


From: Hugh Dickins <hughd@xxxxxxxxxx>

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>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/page_vma_mapped.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index ebf021d4e68b..76503169c1e2 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -186,18 +186,19 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
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);
--
2.30.2