Messages in this thread Patch in this message | | | Date | Wed, 5 Jan 2011 13:00:20 +0900 | From | Daisuke Nishimura <> | Subject | [BUGFIX][PATCH] memcg: fix memory migration of shmem swapcache |
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Hi.
This is a fix for a problem which has bothered me for a month.
=== From: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
In current implimentation, 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> --- include/linux/memcontrol.h | 5 ++--- mm/memcontrol.c | 5 ++--- mm/migrate.c | 2 +- 3 files changed, 5 insertions(+), 7 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 159a076..275157b 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -93,7 +93,7 @@ extern int 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, int result); /* * For memory reclaim. @@ -231,8 +231,7 @@ mem_cgroup_prepare_migration(struct page *page, struct page *newpage, } static inline void mem_cgroup_end_migration(struct mem_cgroup *mem, - struct page *oldpage, - struct page *newpage) + struct page *oldpage, struct page *newpage, int result) { } diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 61678be..632d3bc 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2856,7 +2856,7 @@ int mem_cgroup_prepare_migration(struct page *page, /* 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, int result) { struct page *used, *unused; struct page_cgroup *pc; @@ -2865,8 +2865,7 @@ void mem_cgroup_end_migration(struct mem_cgroup *mem, return; /* blocks rmdir() */ cgroup_exclude_rmdir(&mem->css); - /* at migration success, oldpage->mapping is NULL. */ - if (oldpage->mapping) { + if (result) { used = oldpage; unused = newpage; } else { diff --git a/mm/migrate.c b/mm/migrate.c index 6ae8a66..9a5704a 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -756,7 +756,7 @@ rcu_unlock: rcu_read_unlock(); uncharge: if (!charge) - mem_cgroup_end_migration(mem, page, newpage); + mem_cgroup_end_migration(mem, page, newpage, rc); unlock: unlock_page(page); -- 1.7.1
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