memcg: fix memory migration of shmem swapcache
In the current implementation mem_cgroup_end_migration() decides whether
the page migration has succeeded or not by checking "oldpage->mapping".
But if we are tring to migrate a shmem swapcache, the page->mapping of it
is NULL from the begining, so the check would be invalid. As a result,
mem_cgroup_end_migration() assumes the migration has succeeded even if
it's not, so "newpage" would be freed while it's not uncharged.
This patch fixes it by passing mem_cgroup_end_migration() the result of
the page migration.
Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 067115c..6a576f9 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -98,7 +98,7 @@
mem_cgroup_prepare_migration(struct page *page,
struct page *newpage, struct mem_cgroup **ptr);
extern void mem_cgroup_end_migration(struct mem_cgroup *mem,
- struct page *oldpage, struct page *newpage);
+ struct page *oldpage, struct page *newpage, bool migration_ok);
/*
* For memory reclaim.
@@ -251,8 +251,7 @@
}
static inline void mem_cgroup_end_migration(struct mem_cgroup *mem,
- struct page *oldpage,
- struct page *newpage)
+ struct page *oldpage, struct page *newpage, bool migration_ok)
{
}
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6424ba0..8ab8410 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2896,7 +2896,7 @@
/* remove redundant charge if migration failed*/
void mem_cgroup_end_migration(struct mem_cgroup *mem,
- struct page *oldpage, struct page *newpage)
+ struct page *oldpage, struct page *newpage, bool migration_ok)
{
struct page *used, *unused;
struct page_cgroup *pc;
@@ -2905,8 +2905,7 @@
return;
/* blocks rmdir() */
cgroup_exclude_rmdir(&mem->css);
- /* at migration success, oldpage->mapping is NULL. */
- if (oldpage->mapping) {
+ if (!migration_ok) {
used = oldpage;
unused = newpage;
} else {
diff --git a/mm/migrate.c b/mm/migrate.c
index 5b7d1fd..46fe8cc 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -768,7 +768,7 @@
uncharge:
if (!charge)
- mem_cgroup_end_migration(mem, page, newpage);
+ mem_cgroup_end_migration(mem, page, newpage, rc == 0);
unlock:
unlock_page(page);