Messages in this thread | | | Date | Mon, 24 Jan 2011 19:15:35 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH 1/7] memcg : comment, style fixes for recent patch of move_parent |
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On Mon, 24 Jan 2011 11:14:02 +0100 Johannes Weiner <hannes@cmpxchg.org> wrote:
> On Fri, Jan 21, 2011 at 03:37:26PM +0900, KAMEZAWA Hiroyuki wrote: > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> > > > > A fix for 987eba66e0e6aa654d60881a14731a353ee0acb4 > > > > A clean up for mem_cgroup_move_parent(). > > - remove unnecessary initialization of local variable. > > - rename charge_size -> page_size > > - remove unnecessary (wrong) comment. > > > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> > > --- > > mm/memcontrol.c | 17 +++++++++-------- > > 1 file changed, 9 insertions(+), 8 deletions(-) > > > > Index: mmotm-0107/mm/memcontrol.c > > =================================================================== > > --- mmotm-0107.orig/mm/memcontrol.c > > +++ mmotm-0107/mm/memcontrol.c > > @@ -2265,7 +2265,7 @@ static int mem_cgroup_move_parent(struct > > struct cgroup *cg = child->css.cgroup; > > struct cgroup *pcg = cg->parent; > > struct mem_cgroup *parent; > > - int charge = PAGE_SIZE; > > + int page_size; > > unsigned long flags; > > int ret; > > > > @@ -2278,22 +2278,23 @@ static int mem_cgroup_move_parent(struct > > 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); > > + > > + page_size = PAGE_SIZE << compound_order(page); > > Okay, so you remove the wrong comment, but that does not make the code > right. What protects compound_order from reading garbage because the > page is currently splitting? >
== static int mem_cgroup_move_account(struct page_cgroup *pc, struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge, int charge_size) { int ret = -EINVAL; unsigned long flags;
if ((charge_size > PAGE_SIZE) && !PageTransHuge(pc->page)) return -EBUSY; ==
This is called under compound_lock(). Then, if someone breaks THP, -EBUSY and retry.
Thanks, -Kame
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