Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753259Ab1BVCOS (ORCPT ); Mon, 21 Feb 2011 21:14:18 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:56389 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751972Ab1BVCOR (ORCPT ); Mon, 21 Feb 2011 21:14:17 -0500 Message-ID: <4D631C54.1080703@cn.fujitsu.com> Date: Tue, 22 Feb 2011 10:15:48 +0800 From: Li Zefan User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.9) Gecko/20100921 Fedora/3.1.4-1.fc14 Thunderbird/3.1.4 MIME-Version: 1.0 To: David Rientjes CC: Andrew Morton , LKML , Paul Menage , miaox@cn.fujitsu.com, linux-mm@kvack.org Subject: Re: [PATCH 3/4] cpuset: Fix unchecked calls to NODEMASK_ALLOC() References: <4D5C7EA7.1030409@cn.fujitsu.com> <4D5C7ED1.2070601@cn.fujitsu.com> <4D61DA04.4060007@cn.fujitsu.com> In-Reply-To: X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.1FP4|July 25, 2010) at 2011-02-22 10:13:14, Serialize by Router on mailserver/fnst(Release 8.5.1FP4|July 25, 2010) at 2011-02-22 10:13:14, Serialize complete at 2011-02-22 10:13:14 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5548 Lines: 177 David Rientjes wrote: > On Mon, 21 Feb 2011, Li Zefan wrote: > >> Unfortunately, as I looked into the code again I found cpuset_change_nodemask() >> is called by other functions that use the global cpuset_mems, so I >> think we'd better check the refcnt of cpuset_mems. >> >> How about this: >> >> [PATCH 3/4] cpuset: Fix unchecked calls to NODEMASK_ALLOC() >> >> Those functions that use NODEMASK_ALLOC() can't propogate errno >> to users, so might fail silently. >> >> Based on the fact that all of them are called with cgroup_mutex >> held, we fix this by using a global nodemask. >> > > If all of the functions that require a nodemask are protected by > cgroup_mutex, then I think it would be much better to just statically > allocate them within the function and avoid any nodemask in file scope. > cpuset_mems cannot be shared so introducing it with a refcount would > probably just be confusing. > I'll repost the patchset after you ack this patch. [PATCH 3/4] cpuset: Fix unchecked calls to NODEMASK_ALLOC() Those functions that use NODEMASK_ALLOC() can't propogate errno to users, so might fail silently. Fix it by using one static nodemask_t variable for each function, and those variables are protected by cgroup_mutex. Signed-off-by: Li Zefan --- kernel/cpuset.c | 50 ++++++++++++++++---------------------------------- 1 files changed, 16 insertions(+), 34 deletions(-) diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 8fef8c6..073ce91 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -1015,17 +1015,12 @@ static void cpuset_change_nodemask(struct task_struct *p, struct cpuset *cs; int migrate; const nodemask_t *oldmem = scan->data; - NODEMASK_ALLOC(nodemask_t, newmems, GFP_KERNEL); - - if (!newmems) - return; + static nodemask_t newmems; /* protected by cgroup_mutex */ cs = cgroup_cs(scan->cg); - guarantee_online_mems(cs, newmems); - - cpuset_change_task_nodemask(p, newmems); + guarantee_online_mems(cs, &newmems); - NODEMASK_FREE(newmems); + cpuset_change_task_nodemask(p, &newmems); mm = get_task_mm(p); if (!mm) @@ -1438,41 +1433,35 @@ static void cpuset_attach(struct cgroup_subsys *ss, struct cgroup *cont, struct mm_struct *mm; struct cpuset *cs = cgroup_cs(cont); struct cpuset *oldcs = cgroup_cs(oldcont); - NODEMASK_ALLOC(nodemask_t, to, GFP_KERNEL); - - if (to == NULL) - goto alloc_fail; + static nodemask_t to; /* protected by cgroup_mutex */ if (cs == &top_cpuset) { cpumask_copy(cpus_attach, cpu_possible_mask); } else { guarantee_online_cpus(cs, cpus_attach); } - guarantee_online_mems(cs, to); + guarantee_online_mems(cs, &to); /* do per-task migration stuff possibly for each in the threadgroup */ - cpuset_attach_task(tsk, to, cs); + cpuset_attach_task(tsk, &to, cs); if (threadgroup) { struct task_struct *c; rcu_read_lock(); list_for_each_entry_rcu(c, &tsk->thread_group, thread_group) { - cpuset_attach_task(c, to, cs); + cpuset_attach_task(c, &to, cs); } rcu_read_unlock(); } /* change mm; only needs to be done once even if threadgroup */ - *to = cs->mems_allowed; + to = cs->mems_allowed; mm = get_task_mm(tsk); if (mm) { - mpol_rebind_mm(mm, to); + mpol_rebind_mm(mm, &to); if (is_memory_migrate(cs)) - cpuset_migrate_mm(mm, &oldcs->mems_allowed, to); + cpuset_migrate_mm(mm, &oldcs->mems_allowed, &to); mmput(mm); } - -alloc_fail: - NODEMASK_FREE(to); } /* The various types of files and directories in a cpuset file system */ @@ -2051,10 +2040,7 @@ static void scan_for_empty_cpusets(struct cpuset *root) struct cpuset *cp; /* scans cpusets being updated */ struct cpuset *child; /* scans child cpusets of cp */ struct cgroup *cont; - NODEMASK_ALLOC(nodemask_t, oldmems, GFP_KERNEL); - - if (oldmems == NULL) - return; + static nodemask_t oldmems; /* protected by cgroup_mutex */ list_add_tail((struct list_head *)&root->stack_list, &queue); @@ -2071,7 +2057,7 @@ static void scan_for_empty_cpusets(struct cpuset *root) nodes_subset(cp->mems_allowed, node_states[N_HIGH_MEMORY])) continue; - *oldmems = cp->mems_allowed; + oldmems = cp->mems_allowed; /* Remove offline cpus and mems from this cpuset. */ mutex_lock(&callback_mutex); @@ -2087,10 +2073,9 @@ static void scan_for_empty_cpusets(struct cpuset *root) remove_tasks_in_empty_cpuset(cp); else { update_tasks_cpumask(cp, NULL); - update_tasks_nodemask(cp, oldmems, NULL); + update_tasks_nodemask(cp, &oldmems, NULL); } } - NODEMASK_FREE(oldmems); } /* @@ -2132,19 +2117,16 @@ void cpuset_update_active_cpus(void) static int cpuset_track_online_nodes(struct notifier_block *self, unsigned long action, void *arg) { - NODEMASK_ALLOC(nodemask_t, oldmems, GFP_KERNEL); - - if (oldmems == NULL) - return NOTIFY_DONE; + static nodemask_t oldmems; /* protected by cgroup_mutex */ cgroup_lock(); switch (action) { case MEM_ONLINE: - *oldmems = top_cpuset.mems_allowed; + oldmems = top_cpuset.mems_allowed; mutex_lock(&callback_mutex); top_cpuset.mems_allowed = node_states[N_HIGH_MEMORY]; mutex_unlock(&callback_mutex); - update_tasks_nodemask(&top_cpuset, oldmems, NULL); + update_tasks_nodemask(&top_cpuset, &oldmems, NULL); break; case MEM_OFFLINE: /* -- 1.7.3.1 -- 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/