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authorKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>2010-04-06 14:35:05 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-04-07 08:38:05 -0700
commit8725d5416213a145ccc9c236dbd26830ba409e00 (patch)
treeaff10fc98874adfcb7755ec8bc1f2627036e8dc2 /mm/memcontrol.c
parent116354d177ba2da37e91cf884e3d11e67f825efd (diff)
downloadvexpress-lsk-8725d5416213a145ccc9c236dbd26830ba409e00.tar.gz
memcg: fix race in file_mapped accounting
Presently, memcg's FILE_MAPPED accounting has following race with move_account (happens at rmdir()). increment page->mapcount (rmap.c) mem_cgroup_update_file_mapped() move_account() lock_page_cgroup() check page_mapped() if page_mapped(page)>1 { FILE_MAPPED -1 from old memcg FILE_MAPPED +1 to old memcg } ..... overwrite pc->mem_cgroup unlock_page_cgroup() lock_page_cgroup() FILE_MAPPED + 1 to pc->mem_cgroup unlock_page_cgroup() Then, old memcg (-1 file mapped) new memcg (+2 file mapped) This happens because move_account see page_mapped() which is not guarded by lock_page_cgroup(). This patch adds FILE_MAPPED flag to page_cgroup and move account information based on it. Now, all checks are synchronous with lock_page_cgroup(). Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Reviewed-by: Balbir Singh <balbir@in.ibm.com> Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Cc: Andrea Righi <arighi@develer.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memcontrol.c')
-rw-r--r--mm/memcontrol.c18
1 files changed, 9 insertions, 9 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 9ed760dc744..f4ede99c8b9 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1359,16 +1359,19 @@ void mem_cgroup_update_file_mapped(struct page *page, int val)
lock_page_cgroup(pc);
mem = pc->mem_cgroup;
- if (!mem)
- goto done;
-
- if (!PageCgroupUsed(pc))
+ if (!mem || !PageCgroupUsed(pc))
goto done;
/*
* Preemption is already disabled. We can use __this_cpu_xxx
*/
- __this_cpu_add(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED], val);
+ if (val > 0) {
+ __this_cpu_inc(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
+ SetPageCgroupFileMapped(pc);
+ } else {
+ __this_cpu_dec(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
+ ClearPageCgroupFileMapped(pc);
+ }
done:
unlock_page_cgroup(pc);
@@ -1801,16 +1804,13 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
static void __mem_cgroup_move_account(struct page_cgroup *pc,
struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge)
{
- struct page *page;
-
VM_BUG_ON(from == to);
VM_BUG_ON(PageLRU(pc->page));
VM_BUG_ON(!PageCgroupLocked(pc));
VM_BUG_ON(!PageCgroupUsed(pc));
VM_BUG_ON(pc->mem_cgroup != from);
- page = pc->page;
- if (page_mapped(page) && !PageAnon(page)) {
+ if (PageCgroupFileMapped(pc)) {
/* Update mapped_file data for mem_cgroup */
preempt_disable();
__this_cpu_dec(from->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);