Messages in this thread Patch in this message | | | Date | Thu, 6 Jan 2011 12:34:15 +0900 | From | Daisuke Nishimura <> | Subject | [BUGFIX][PATCH v3] memcg: fix memory migration of shmem swapcache |
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> > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > > index 159a076..cc5a8fd 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, bool success); > > The term "success" implies present or future tense. > The event this variable cares about in the past so "succeed" might be > a more appropriate term. > Sorry to be picky about the English but there is an important > distinction here since we don't have any comment about the variable. > > Am I being too fussy? Not at all. Your comments are very helpful to make the code more readable :)
=== 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> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> --- v2->v3 - s/success/succeed
v1->v2 - pass mem_cgroup_end_migration() "bool" instead of "int".
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..9f52b57 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, bool succeed); /* * 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, bool succeed) { } diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 61678be..71a39bc 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, bool succeed) { 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 (!succeed) { used = oldpage; unused = newpage; } else { diff --git a/mm/migrate.c b/mm/migrate.c index 6ae8a66..be66b23 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 == 0); unlock: unlock_page(page); -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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