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authorHugh Dickins <hugh@veritas.com>2008-03-04 14:29:12 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-03-04 16:35:15 -0800
commit6d48ff8bcfd403ec8d3ef7a56538ea9e6f773b9c (patch)
tree9331ed70405f4933ac923a7595268ee7e773018e
parentb9c565d5a29a795f970b4a1340393d8fc6722fb9 (diff)
downloadkernel-6d48ff8bcfd403ec8d3ef7a56538ea9e6f773b9c.tar.gz
memcg: css_put after remove_list
mem_cgroup_uncharge_page does css_put on the mem_cgroup before uncharging from it, and before removing page_cgroup from one of its lru lists: isn't there a danger that struct mem_cgroup memory could be freed and reused before completing that, so corrupting something? Never seen it, and for all I know there may be other constraints which make it impossible; but let's be defensive and reverse the ordering there. mem_cgroup_force_empty_list is safe because there's an extra css_get around all its works; but even so, change its ordering the same way round, to help get in the habit of doing it like this. Signed-off-by: Hugh Dickins <hugh@veritas.com> Cc: David Rientjes <rientjes@google.com> Cc: Balbir Singh <balbir@linux.vnet.ibm.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Hirokazu Takahashi <taka@valinux.co.jp> Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp> Cc: Paul Menage <menage@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/memcontrol.c12
1 files changed, 6 insertions, 6 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 13e9e7d8e49e..66d0e84cefa6 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -665,15 +665,15 @@ void mem_cgroup_uncharge_page(struct page *page)
page_assign_page_cgroup(page, NULL);
unlock_page_cgroup(page);
- mem = pc->mem_cgroup;
- css_put(&mem->css);
- res_counter_uncharge(&mem->res, PAGE_SIZE);
-
mz = page_cgroup_zoneinfo(pc);
spin_lock_irqsave(&mz->lru_lock, flags);
__mem_cgroup_remove_list(pc);
spin_unlock_irqrestore(&mz->lru_lock, flags);
+ mem = pc->mem_cgroup;
+ res_counter_uncharge(&mem->res, PAGE_SIZE);
+ css_put(&mem->css);
+
kfree(pc);
return;
}
@@ -774,9 +774,9 @@ retry:
if (page_get_page_cgroup(page) == pc) {
page_assign_page_cgroup(page, NULL);
unlock_page_cgroup(page);
- css_put(&mem->css);
- res_counter_uncharge(&mem->res, PAGE_SIZE);
__mem_cgroup_remove_list(pc);
+ res_counter_uncharge(&mem->res, PAGE_SIZE);
+ css_put(&mem->css);
kfree(pc);
} else {
/* racing uncharge: let page go then retry */