diff options
author | KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> | 2011-01-25 23:07:29 (GMT) |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-01-26 00:50:04 (GMT) |
commit | 52dbb9050936fd33ceb45f10529dbc992507c058 (patch) | |
tree | 1c3663f50b7dec0bd852b02d76095b9a5618d7b7 | |
parent | 3d37c4a9199920964ffdfaec6335d93b9dcf9ca5 (diff) | |
download | linux-fsl-qoriq-52dbb9050936fd33ceb45f10529dbc992507c058.tar.xz |
memcg: fix race at move_parent around compound_order()
A fix up mem_cgroup_move_parent() which use compound_order() in
asynchronous manner. This compound_order() may return unknown value
because we don't take lock. Use PageTransHuge() and HPAGE_SIZE instead
of it.
Also clean up for mem_cgroup_move_parent().
- remove unnecessary initialization of local variable.
- rename charge_size -> page_size
- remove unnecessary (wrong) comment.
- added a comment about THP.
Note:
Current design take compound_page_lock() in caller of move_account().
This should be revisited when we implement direct move_task of hugepage
without splitting.
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r-- | mm/memcontrol.c | 25 |
1 files changed, 16 insertions, 9 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 8ab1d42..3878cfe 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2236,7 +2236,12 @@ static int mem_cgroup_move_account(struct page_cgroup *pc, { int ret = -EINVAL; unsigned long flags; - + /* + * The page is isolated from LRU. So, collapse function + * will not handle this page. But page splitting can happen. + * Do this check under compound_page_lock(). The caller should + * hold it. + */ if ((charge_size > PAGE_SIZE) && !PageTransHuge(pc->page)) return -EBUSY; @@ -2268,7 +2273,7 @@ static int mem_cgroup_move_parent(struct page_cgroup *pc, struct cgroup *cg = child->css.cgroup; struct cgroup *pcg = cg->parent; struct mem_cgroup *parent; - int charge = PAGE_SIZE; + int page_size = PAGE_SIZE; unsigned long flags; int ret; @@ -2281,22 +2286,24 @@ static int mem_cgroup_move_parent(struct page_cgroup *pc, goto out; if (isolate_lru_page(page)) goto put; - /* The page is isolated from LRU and we have no race with splitting */ - charge = PAGE_SIZE << compound_order(page); + + if (PageTransHuge(page)) + page_size = HPAGE_SIZE; parent = mem_cgroup_from_cont(pcg); - ret = __mem_cgroup_try_charge(NULL, gfp_mask, &parent, false, charge); + ret = __mem_cgroup_try_charge(NULL, gfp_mask, + &parent, false, page_size); if (ret || !parent) goto put_back; - if (charge > PAGE_SIZE) + if (page_size > PAGE_SIZE) flags = compound_lock_irqsave(page); - ret = mem_cgroup_move_account(pc, child, parent, true, charge); + ret = mem_cgroup_move_account(pc, child, parent, true, page_size); if (ret) - mem_cgroup_cancel_charge(parent, charge); + mem_cgroup_cancel_charge(parent, page_size); - if (charge > PAGE_SIZE) + if (page_size > PAGE_SIZE) compound_unlock_irqrestore(page, flags); put_back: putback_lru_page(page); |