The patch titled
Subject: mm: page migration use the put_new_page whenever necessary
has been added to the -mm tree. Its filename is
mm-page-migration-use-the-put_new_page-whenever-necessary.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-page-migration-use-the-put_new_page-whenever-necessary.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-page-migration-use-the-put_new_page-whenever-necessary.patch
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------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: mm: page migration use the put_new_page whenever necessary
I don't know of any problem from the way it's used in our current tree,
but there is one defect in page migration's custom put_new_page feature.
An unused newpage is expected to be released with the put_new_page(), but
there was one MIGRATEPAGE_SUCCESS (0) path which released it with
putback_lru_page(): which can be very wrong for a custom pool.
Fixed more easily by resetting put_new_page once it won't be needed, than
by adding a further flag to modify the rc test.
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Sasha Levin <sasha.levin@xxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/migrate.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)
diff -puN mm/migrate.c~mm-page-migration-use-the-put_new_page-whenever-necessary mm/migrate.c
--- a/mm/migrate.c~mm-page-migration-use-the-put_new_page-whenever-necessary
+++ a/mm/migrate.c
@@ -938,10 +938,11 @@ static ICE_noinline int unmap_and_move(n
int force, enum migrate_mode mode,
enum migrate_reason reason)
{
- int rc = 0;
+ int rc = MIGRATEPAGE_SUCCESS;
int *result = NULL;
- struct page *newpage = get_new_page(page, private, &result);
+ struct page *newpage;
+ newpage = get_new_page(page, private, &result);
if (!newpage)
return -ENOMEM;
@@ -955,6 +956,8 @@ static ICE_noinline int unmap_and_move(n
goto out;
rc = __unmap_and_move(page, newpage, force, mode);
+ if (rc == MIGRATEPAGE_SUCCESS)
+ put_new_page = NULL;
out:
if (rc != -EAGAIN) {
@@ -981,7 +984,7 @@ out:
* it. Otherwise, putback_lru_page() will drop the reference grabbed
* during isolation.
*/
- if (rc != MIGRATEPAGE_SUCCESS && put_new_page) {
+ if (put_new_page) {
ClearPageSwapBacked(newpage);
put_new_page(newpage, private);
} else if (unlikely(__is_movable_balloon_page(newpage))) {
@@ -1022,7 +1025,7 @@ static int unmap_and_move_huge_page(new_
struct page *hpage, int force,
enum migrate_mode mode)
{
- int rc = 0;
+ int rc = -EAGAIN;
int *result = NULL;
int page_was_mapped = 0;
struct page *new_hpage;
@@ -1044,8 +1047,6 @@ static int unmap_and_move_huge_page(new_
if (!new_hpage)
return -ENOMEM;
- rc = -EAGAIN;
-
if (!trylock_page(hpage)) {
if (!force || mode != MIGRATE_SYNC)
goto out;
@@ -1070,8 +1071,10 @@ static int unmap_and_move_huge_page(new_
if (anon_vma)
put_anon_vma(anon_vma);
- if (rc == MIGRATEPAGE_SUCCESS)
+ if (rc == MIGRATEPAGE_SUCCESS) {
hugetlb_cgroup_migrate(hpage, new_hpage);
+ put_new_page = NULL;
+ }
unlock_page(hpage);
out:
@@ -1083,7 +1086,7 @@ out:
* it. Otherwise, put_page() will drop the reference grabbed during
* isolation.
*/
- if (rc != MIGRATEPAGE_SUCCESS && put_new_page)
+ if (put_new_page)
put_new_page(new_hpage, private);
else
putback_active_hugepage(new_hpage);
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
memcg-simplify-and-inline-__mem_cgroup_from_kmem-fix-2.patch
mm-documentation-undoc-non-linear-vmas.patch
mm-rmap-use-pte-lock-not-mmap_sem-to-set-pagemlocked.patch
mm-page-migration-fix-pagemlocked-on-migrated-pages.patch
mm-rename-mem_cgroup_migrate-to-mem_cgroup_replace_page.patch
mm-correct-a-couple-of-page-migration-comments.patch
mm-page-migration-use-the-put_new_page-whenever-necessary.patch
mm-page-migration-trylock-newpage-at-same-level-as-oldpage.patch
mm-page-migration-remove_migration_ptes-at-lockunlock-level.patch
mm-simplify-page-migrations-anon_vma-comment-and-flow.patch
mm-page-migration-use-migration-entry-for-swapcache-too.patch
mm-page-migration-avoid-touching-newpage-until-no-going-back.patch
mm-migrate-dirty-page-without-clear_page_dirty_for_io-etc.patch
mm-use-unsigned-int-for-page-order-fix-2.patch
mm-dont-split-thp-page-when-syscall-is-called-fix-4.patch
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