From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id E93016B0087 for ; Wed, 5 Jan 2011 22:37:40 -0500 (EST) Date: Thu, 6 Jan 2011 12:34:15 +0900 From: Daisuke Nishimura Subject: [BUGFIX][PATCH v3] memcg: fix memory migration of shmem swapcache Message-Id: <20110106123415.895d6dfc.nishimura@mxp.nes.nec.co.jp> In-Reply-To: References: <20110105130020.e2a854e4.nishimura@mxp.nes.nec.co.jp> <20110105115840.GD4654@cmpxchg.org> <20110106100923.24b1dd12.nishimura@mxp.nes.nec.co.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org To: Minchan Kim Cc: Daisuke Nishimura , Johannes Weiner , Andrew Morton , Balbir Singh , KAMEZAWA Hiroyuki , LKML , linux-mm List-ID: > > 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 > > A mem_cgroup_prepare_migration(struct page *page, > > A A A A struct page *newpage, struct mem_cgroup **ptr); > > A extern void mem_cgroup_end_migration(struct mem_cgroup *mem, > > - A A A struct page *oldpage, struct page *newpage); > > + A A A 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 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 Reviewed-by: Minchan Kim Acked-by: KAMEZAWA Hiroyuki --- 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org