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| author | Hugh Dickins <hugh@veritas.com> | 2008-03-04 14:29:12 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2008-03-04 16:35:15 -0800 |
| commit | 6d48ff8bcfd403ec8d3ef7a56538ea9e6f773b9c (patch) | |
| tree | 9331ed70405f4933ac923a7595268ee7e773018e /mm/memcontrol.c | |
| parent | b9c565d5a29a795f970b4a1340393d8fc6722fb9 (diff) | |
| download | lwn-6d48ff8bcfd403ec8d3ef7a56538ea9e6f773b9c.tar.gz lwn-6d48ff8bcfd403ec8d3ef7a56538ea9e6f773b9c.zip | |
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>
Diffstat (limited to 'mm/memcontrol.c')
| -rw-r--r-- | mm/memcontrol.c | 12 |
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 */ |