From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 727796B004F for ; Thu, 8 Jan 2009 05:18:22 -0500 (EST) Date: Thu, 8 Jan 2009 19:15:01 +0900 From: Daisuke Nishimura Subject: [RFC][PATCH 3/4] memcg: fix for mem_cgroup_hierarchical_reclaim Message-Id: <20090108191501.dc469a51.nishimura@mxp.nes.nec.co.jp> In-Reply-To: <20090108190818.b663ce20.nishimura@mxp.nes.nec.co.jp> References: <20090108190818.b663ce20.nishimura@mxp.nes.nec.co.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, kamezawa.hiroyu@jp.fujitsu.com, balbir@linux.vnet.ibm.com, lizf@cn.fujitsu.com, menage@google.com, nishimura@mxp.nes.nec.co.jp List-ID: 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 --- mm/memcontrol.c | 37 +++++++++++++++++++++---------------- 1 files changed, 21 insertions(+), 16 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 288e22c..dc38a0e 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -622,7 +622,7 @@ unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan, * called with hierarchy_mutex held */ static struct mem_cgroup * -mem_cgroup_get_next_node(struct mem_cgroup *curr, struct mem_cgroup *root_mem) +__mem_cgroup_get_next_node(struct mem_cgroup *curr, struct mem_cgroup *root_mem) { struct cgroup *cgroup, *curr_cgroup, *root_cgroup; @@ -644,8 +644,8 @@ mem_cgroup_get_next_node(struct mem_cgroup *curr, struct mem_cgroup *root_mem) visit_parent: if (curr_cgroup == root_cgroup) { mem_cgroup_put(curr); - curr = root_mem; - mem_cgroup_get(curr); + /* caller handles NULL case */ + curr = NULL; goto done; } @@ -668,7 +668,6 @@ visit_parent: goto visit_parent; done: - root_mem->last_scanned_child = curr; return curr; } @@ -678,20 +677,29 @@ done: * that to reclaim free pages from. */ static struct mem_cgroup * -mem_cgroup_get_first_node(struct mem_cgroup *root_mem) +mem_cgroup_get_next_node(struct mem_cgroup *root_mem) { struct cgroup *cgroup; struct mem_cgroup *ret; bool obsolete; - 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); + + obsolete = mem_cgroup_is_obsolete(root_mem->last_scanned_child); + if (list_empty(&root_mem->css.cgroup->children)) { - ret = root_mem; + /* + * root_mem might have children before and last_scanned_child + * may point to one of them. + */ + if (root_mem->last_scanned_child) { + VM_BUG_ON(!obsolete); + mem_cgroup_put(root_mem->last_scanned_child); + } + ret = NULL; goto done; } @@ -705,13 +713,13 @@ mem_cgroup_get_first_node(struct mem_cgroup *root_mem) ret = mem_cgroup_from_cont(cgroup); mem_cgroup_get(ret); } else - ret = mem_cgroup_get_next_node(root_mem->last_scanned_child, + 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; + return (ret) ? ret : root_mem; } static bool mem_cgroup_check_under_limit(struct mem_cgroup *mem) @@ -769,21 +777,18 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem, if (!root_mem->use_hierarchy) return ret; - next_mem = mem_cgroup_get_first_node(root_mem); + next_mem = mem_cgroup_get_next_node(root_mem); while (next_mem != root_mem) { if (mem_cgroup_is_obsolete(next_mem)) { - mem_cgroup_put(next_mem); - next_mem = mem_cgroup_get_first_node(root_mem); + next_mem = mem_cgroup_get_next_node(root_mem); continue; } ret = try_to_free_mem_cgroup_pages(next_mem, gfp_mask, noswap, get_swappiness(next_mem)); if (mem_cgroup_check_under_limit(root_mem)) return 0; - mutex_lock(&mem_cgroup_subsys.hierarchy_mutex); - next_mem = mem_cgroup_get_next_node(next_mem, root_mem); - mutex_unlock(&mem_cgroup_subsys.hierarchy_mutex); + next_mem = mem_cgroup_get_next_node(root_mem); } return ret; } -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org