From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Weiner Subject: Re: [PATCH v3] memcg: return -EINTR at bypassing try_charge(). Date: Wed, 21 Dec 2011 13:28:15 +0100 Message-ID: <20111221122815.GF3870@cmpxchg.org> References: <20111219165146.4d72f1bb.kamezawa.hiroyu@jp.fujitsu.com> <20111221172423.5d036cdd.kamezawa.hiroyu@jp.fujitsu.com> <20111221192934.2751f8f1.kamezawa.hiroyu@jp.fujitsu.com> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <20111221192934.2751f8f1.kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: KAMEZAWA Hiroyuki Cc: "akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org" , "linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org" , cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Michal Hocko , Hugh Dickins On Wed, Dec 21, 2011 at 07:29:34PM +0900, KAMEZAWA Hiroyuki wrote: > Thank you for review. > I'm sorry if my response is delayed. > == > >From 1e8c917c64b3947d2e54c6e5073d53d80bd97c30 Mon Sep 17 00:00:00 2001 > From: KAMEZAWA Hiroyuki > Date: Wed, 21 Dec 2011 16:27:25 +0900 > Subject: [PATCH] memcg: return -EINTR at bypassing try_charge(). > > This patch is a fix for memcg-simplify-lru-handling-by-new-rule.patch > When running testprogram and stop it by Ctrl-C, add_lru/del_lru > will find pc->mem_cgroup is NULL and get panic. The reason > is bypass code in try_charge(). > > At try_charge(), it checks the thread is fatal or not as.. > fatal_signal_pending() or TIF_MEMDIE. In this case, __try_charge() > returns 0(success) with setting *ptr as NULL. > > Now, lruvec are deteremined by pc->mem_cgroup. So, it's better > to reset pc->mem_cgroup as root_mem_cgroup. This patch does > following change in try_charge() > 1. return -EINTR at bypassing. > 2. set *ptr = root_mem_cgroup at bypassing. > > By this change, in page fault / radix-tree-insert path, > the page will be charged against root_mem_cgroup and the thread's > operations will go ahead without trouble. In other path, > migration or move_account etc..., -EINTR will stop the operation. > (may need some cleanup later..) > > After this change, pc->mem_cgroup will have valid pointer if > the page is used. > > Changelog: v2 -> v3 > - handle !mm case in another way. > - removed redundant commments > - fixed move_parent bug of uninitialized pointer > Changelog: v1 -> v2 > - returns -EINTR at bypassing. > - change error code handling at callers. > - changed the name of patch. > > Signed-off-by: KAMEZAWA Hiroyuki Looks good now, thanks. Acked-by: Johannes Weiner