cpuset: fix unchecked calls to NODEMASK_ALLOC()

Those functions that use NODEMASK_ALLOC() can't propagate errno
to users, but will fail silently.

Fix it by using a static nodemask_t variable for each function, and
those variables are protected by cgroup_mutex;

[akpm@linux-foundation.org: fix comment spelling, strengthen cgroup_lock comment]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 16 insertions, 35 deletions

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 7f384f4013b2..e472fe139192 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);
+        guarantee_online_mems(cs, &newmems);
 
-        cpuset_change_task_nodemask(p, 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 */
@@ -2055,10 +2044,7 @@ 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);
 
@@ -2075,7 +2061,7 @@ 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);
@@ -2091,10 +2077,9 @@ 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);
 }
 
 /*
@@ -2136,19 +2121,16 @@ 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:
                 /*
@@ -2162,7 +2144,6 @@ static int cpuset_track_online_nodes(struct notifier_block *self,
         }
         cgroup_unlock();
 
-        NODEMASK_FREE(oldmems);
         return NOTIFY_OK;
 }
 #endif