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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 /include
parent116354d177ba2da37e91cf884e3d11e67f825efd (diff)
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 'include')
-rw-r--r--include/linux/page_cgroup.h6
1 files changed, 6 insertions, 0 deletions
diff --git a/include/linux/page_cgroup.h b/include/linux/page_cgroup.h
index 30b08136fdf..aef22ae2af4 100644
--- a/include/linux/page_cgroup.h
+++ b/include/linux/page_cgroup.h
@@ -39,6 +39,7 @@ enum {
PCG_CACHE, /* charged as cache */
PCG_USED, /* this object is in use. */
PCG_ACCT_LRU, /* page has been accounted for */
+ PCG_FILE_MAPPED, /* page is accounted as "mapped" */
};
#define TESTPCGFLAG(uname, lname) \
@@ -73,6 +74,11 @@ CLEARPCGFLAG(AcctLRU, ACCT_LRU)
TESTPCGFLAG(AcctLRU, ACCT_LRU)
TESTCLEARPCGFLAG(AcctLRU, ACCT_LRU)
+
+SETPCGFLAG(FileMapped, FILE_MAPPED)
+CLEARPCGFLAG(FileMapped, FILE_MAPPED)
+TESTPCGFLAG(FileMapped, FILE_MAPPED)
+
static inline int page_cgroup_nid(struct page_cgroup *pc)
{
return page_to_nid(pc->page);