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Date: Tue, 22 Feb 2011 10:15:48 +0800
From: Li Zefan <lizf@...fujitsu.com>
To: David Rientjes <rientjes@...gle.com>
CC: Andrew Morton <akpm@...ux-foundation.org>,
LKML <linux-kernel@...r.kernel.org>,
Paul Menage <menage@...gle.com>, miaox@...fujitsu.com,
linux-mm@...ck.org
Subject: Re: [PATCH 3/4] cpuset: Fix unchecked calls to NODEMASK_ALLOC()
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 <lizf@...fujitsu.com>
---
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
--
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