cpuset: remove unnecessary variable in cpuset_attach()

[~andy/linux] / kernel / cpuset.c

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 64b3f791bbe595905b00e9cf8ecbee763cbacf7d..dbef832e5e2da16b278130738d469247911f59fa 100644 (file)
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -304,53 +304,38 @@ static struct file_system_type cpuset_fs_type = {
 /*
  * Return in pmask the portion of a cpusets's cpus_allowed that
  * are online.  If none are online, walk up the cpuset hierarchy
- * until we find one that does have some online cpus.  If we get
- * all the way to the top and still haven't found any online cpus,
- * return cpu_online_mask.  Or if passed a NULL cs from an exit'ing
- * task, return cpu_online_mask.
+ * until we find one that does have some online cpus.  The top
+ * cpuset always has some cpus online.
  *
  * One way or another, we guarantee to return some non-empty subset
  * of cpu_online_mask.
  *
  * Call with callback_mutex held.
  */
-
 static void guarantee_online_cpus(const struct cpuset *cs,
                                  struct cpumask *pmask)
 {
-       while (cs && !cpumask_intersects(cs->cpus_allowed, cpu_online_mask))
+       while (!cpumask_intersects(cs->cpus_allowed, cpu_online_mask))
                cs = parent_cs(cs);
-       if (cs)
-               cpumask_and(pmask, cs->cpus_allowed, cpu_online_mask);
-       else
-               cpumask_copy(pmask, cpu_online_mask);
-       BUG_ON(!cpumask_intersects(pmask, cpu_online_mask));
+       cpumask_and(pmask, cs->cpus_allowed, cpu_online_mask);
 }
 
 /*
  * Return in *pmask the portion of a cpusets's mems_allowed that
  * are online, with memory.  If none are online with memory, walk
  * up the cpuset hierarchy until we find one that does have some
- * online mems.  If we get all the way to the top and still haven't
- * found any online mems, return node_states[N_MEMORY].
+ * online mems.  The top cpuset always has some mems online.
  *
  * One way or another, we guarantee to return some non-empty subset
  * of node_states[N_MEMORY].
  *
  * Call with callback_mutex held.
  */
-
 static void guarantee_online_mems(const struct cpuset *cs, nodemask_t *pmask)
 {
-       while (cs && !nodes_intersects(cs->mems_allowed,
-                                       node_states[N_MEMORY]))
+       while (!nodes_intersects(cs->mems_allowed, node_states[N_MEMORY]))
                cs = parent_cs(cs);
-       if (cs)
-               nodes_and(*pmask, cs->mems_allowed,
-                                       node_states[N_MEMORY]);
-       else
-               *pmask = node_states[N_MEMORY];
-       BUG_ON(!nodes_intersects(*pmask, node_states[N_MEMORY]));
+       nodes_and(*pmask, cs->mems_allowed, node_states[N_MEMORY]);
 }
 
 /*
@@ -1422,8 +1407,7 @@ static cpumask_var_t cpus_attach;
 
 static void cpuset_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
 {
-       /* static bufs protected by cpuset_mutex */
-       static nodemask_t cpuset_attach_nodemask_from;
+       /* static buf protected by cpuset_mutex */
        static nodemask_t cpuset_attach_nodemask_to;
        struct mm_struct *mm;
        struct task_struct *task;
@@ -1457,13 +1441,12 @@ static void cpuset_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
         * Change mm, possibly for multiple threads in a threadgroup. This is
         * expensive and may sleep.
         */
-       cpuset_attach_nodemask_from = oldcs->mems_allowed;
        cpuset_attach_nodemask_to = cs->mems_allowed;
        mm = get_task_mm(leader);
        if (mm) {
                mpol_rebind_mm(mm, &cpuset_attach_nodemask_to);
                if (is_memory_migrate(cs))
-                       cpuset_migrate_mm(mm, &cpuset_attach_nodemask_from,
+                       cpuset_migrate_mm(mm, &oldcs->mems_allowed,
                                          &cpuset_attach_nodemask_to);
                mmput(mm);
        }
@@ -2253,8 +2236,7 @@ void cpuset_cpus_allowed_fallback(struct task_struct *tsk)
 
        rcu_read_lock();
        cs = task_cs(tsk);
-       if (cs)
-               do_set_cpus_allowed(tsk, cs->cpus_allowed);
+       do_set_cpus_allowed(tsk, cs->cpus_allowed);
        rcu_read_unlock();
 
        /*