Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754597AbZAIDF0 (ORCPT ); Thu, 8 Jan 2009 22:05:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751461AbZAIDFM (ORCPT ); Thu, 8 Jan 2009 22:05:12 -0500 Received: from TYO202.gate.nec.co.jp ([202.32.8.206]:58508 "EHLO tyo202.gate.nec.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751003AbZAIDFK (ORCPT ); Thu, 8 Jan 2009 22:05:10 -0500 Date: Fri, 9 Jan 2009 11:51:03 +0900 From: Daisuke Nishimura To: KAMEZAWA Hiroyuki Cc: nishimura@mxp.nes.nec.co.jp, linux-mm@kvack.org, linux-kernel@vger.kernel.org, balbir@linux.vnet.ibm.com, lizf@cn.fujitsu.com, menage@google.com Subject: Re: [RFC][PATCH 3/4] memcg: fix for mem_cgroup_hierarchical_reclaim Message-Id: <20090109115103.e17b18f2.nishimura@mxp.nes.nec.co.jp> In-Reply-To: <20090109100830.3e9c90e0.kamezawa.hiroyu@jp.fujitsu.com> References: <20090108190818.b663ce20.nishimura@mxp.nes.nec.co.jp> <20090108191501.dc469a51.nishimura@mxp.nes.nec.co.jp> <39822.10.75.179.62.1231412881.squirrel@webmail-b.css.fujitsu.com> <20090109100830.3e9c90e0.kamezawa.hiroyu@jp.fujitsu.com> Organization: NEC Soft, Ltd. X-Mailer: Sylpheed 2.4.8 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5634 Lines: 170 On Fri, 9 Jan 2009 10:08:30 +0900, KAMEZAWA Hiroyuki wrote: > On Thu, 8 Jan 2009 20:08:01 +0900 (JST) > "KAMEZAWA Hiroyuki" wrote: > > > Daisuke Nishimura said: > > > If root_mem has no children, last_scaned_child is set to root_mem itself. > > > But after some children added to root_mem, mem_cgroup_get_next_node can > > > mem_cgroup_put the root_mem although root_mem has not been mem_cgroup_get. > > > > > > This patch fixes this behavior by: > > > - Set last_scanned_child to NULL if root_mem has no children or DFS search > > > has returned to root_mem itself(root_mem is not a "child" of root_mem). > > > Make mem_cgroup_get_first_node return root_mem in this case. > > > There are no mem_cgroup_get/put for root_mem. > > > - Rename mem_cgroup_get_next_node to __mem_cgroup_get_next_node, and > > > mem_cgroup_get_first_node to mem_cgroup_get_next_node. > > > Make mem_cgroup_hierarchical_reclaim call only new > > > mem_cgroup_get_next_node. > > > > > > > > > Signed-off-by: Daisuke Nishimura > > > > Hmm, seems necessary fix. Then, it's better to rebase my patch on to this. > > > > Reviewed-by: KAMEZAWA Hiroyuki > > > > Maybe simpler one can be written but my patch remove all this out later.... > > > How about this ? (just an exmaple and not tested, sorry) > > hmm, I don't think it's much simpler than this one(I don't want last_scanned_child to point to the mem itself, because it's not a "child"). This part will be re-written by your patch, but this patch is needed to fix a bug(I saw general protection fault), so let's fix one by one. I'll post my original version. It's well tested :) Thanks, Daisuke Nishimura. > > --- > mm/memcontrol.c | 52 ++++++++++++++++++++++------------------------------ > 1 file changed, 22 insertions(+), 30 deletions(-) > > Index: mmotm-2.6.28-Jan7/mm/memcontrol.c > =================================================================== > --- mmotm-2.6.28-Jan7.orig/mm/memcontrol.c > +++ mmotm-2.6.28-Jan7/mm/memcontrol.c > @@ -621,6 +621,7 @@ static struct mem_cgroup * > mem_cgroup_get_next_node(struct mem_cgroup *curr, struct mem_cgroup *root_mem) > { > struct cgroup *cgroup, *curr_cgroup, *root_cgroup; > + struct mem_cgroup *orig = root_mem->last_scanned_child; > > curr_cgroup = curr->css.cgroup; > root_cgroup = root_mem->css.cgroup; > @@ -629,19 +630,15 @@ mem_cgroup_get_next_node(struct mem_cgro > /* > * Walk down to children > */ > - mem_cgroup_put(curr); > cgroup = list_entry(curr_cgroup->children.next, > struct cgroup, sibling); > curr = mem_cgroup_from_cont(cgroup); > - mem_cgroup_get(curr); > goto done; > } > > visit_parent: > if (curr_cgroup == root_cgroup) { > - mem_cgroup_put(curr); > curr = root_mem; > - mem_cgroup_get(curr); > goto done; > } > > @@ -649,11 +646,9 @@ visit_parent: > * Goto next sibling > */ > if (curr_cgroup->sibling.next != &curr_cgroup->parent->children) { > - mem_cgroup_put(curr); > cgroup = list_entry(curr_cgroup->sibling.next, struct cgroup, > sibling); > curr = mem_cgroup_from_cont(cgroup); > - mem_cgroup_get(curr); > goto done; > } > > @@ -664,7 +659,10 @@ visit_parent: > goto visit_parent; > > done: > + if (orig) > + mem_cgroup_put(orig); > root_mem->last_scanned_child = curr; > + mem_cgroup_get(curr); > return curr; > } > > @@ -677,35 +675,25 @@ static struct mem_cgroup * > mem_cgroup_get_first_node(struct mem_cgroup *root_mem) > { > struct cgroup *cgroup; > - struct mem_cgroup *ret; > - bool obsolete; > + struct mem_cgroup *ret, *orig; > > - obsolete = mem_cgroup_is_obsolete(root_mem->last_scanned_child); > - > - /* > - * Scan all children under the mem_cgroup mem > - */ > mutex_lock(&mem_cgroup_subsys.hierarchy_mutex); > - if (list_empty(&root_mem->css.cgroup->children)) { > - ret = root_mem; > - goto done; > - } > - > - if (!root_mem->last_scanned_child || obsolete) { > - > - if (obsolete && root_mem->last_scanned_child) > - mem_cgroup_put(root_mem->last_scanned_child); > + orig = root_mem->last_scanned_child; > > - cgroup = list_first_entry(&root_mem->css.cgroup->children, > - struct cgroup, sibling); > - ret = mem_cgroup_from_cont(cgroup); > + if (!orig) { > + if (list_empty(&root_mem->css.cgroup->children)) { > + ret = root_mem; > + } else { > + cgroup = > + list_first_entry(&root_mem->css.cgroup->children, > + struct cgroup, sibling); > + ret = mem_cgroup_from_cont(cgroup); > + } > + root_mem->last_scanned_child = ret; > mem_cgroup_get(ret); > - } else > + } else /* get_next_node will manage refcnt */ > ret = mem_cgroup_get_next_node(root_mem->last_scanned_child, > root_mem); > - > -done: > - root_mem->last_scanned_child = ret; > mutex_unlock(&mem_cgroup_subsys.hierarchy_mutex); > return ret; > } > @@ -2232,7 +2220,11 @@ static void mem_cgroup_pre_destroy(struc > static void mem_cgroup_destroy(struct cgroup_subsys *ss, > struct cgroup *cont) > { > - mem_cgroup_put(mem_cgroup_from_cont(cont)); > + struct mem_cgroup *mem = mem_cgroup_from_cont(cont); > + > + if (mem->last_scanned_child == mem) > + mem_cgroup_put(mem); > + mem_cgroup_put(mem); > } > > static int mem_cgroup_populate(struct cgroup_subsys *ss, > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/