cgroup/cpuset: Improve temporary cpumasks handling

The limitation that update_parent_subparts_cpumask() can only use
addmask & delmask in the given tmp cpumasks is fragile and may lead to
unexpected error.

Fix this problem by allocating/freeing a struct tmpmasks in
update_cpumask() to avoid reusing the cpumasks in trial_cs.

With this change, we can move the update_tasks_cpumask() for the
parent and update_sibling_cpumasks() for the sibling to inside
update_parent_subparts_cpumask().

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index d8d3b750c1386c333a4ba900896de2a39354596a..c9bb44e50eb21261e781e7e51ba712aa99ef2cc5 100644 (file)
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1277,6 +1277,8 @@ enum subparts_cmd {
 
 static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
                       int turning_on);
+static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,
+                                   struct tmpmasks *tmp);
 
 /*
  * Update partition exclusive flag
@@ -1447,7 +1449,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,
                adding = cpumask_andnot(tmp->addmask, tmp->addmask,
                                        parent->subparts_cpus);
                /*
-                * Empty cpumask is not allewed
+                * Empty cpumask is not allowed
                 */
                if (cpumask_empty(newmask)) {
                        part_error = PERR_CPUSEMPTY;
@@ -1567,8 +1569,11 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,
 
        spin_unlock_irq(&callback_lock);
 
-       if (adding || deleting)
+       if (adding || deleting) {
                update_tasks_cpumask(parent, tmp->addmask);
+               if (parent->child_ecpus_count)
+                       update_sibling_cpumasks(parent, cs, tmp);
+       }
 
        /*
         * For partcmd_update without newmask, it is being called from
@@ -1842,18 +1847,8 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
        if (cpumask_equal(cs->cpus_allowed, trialcs->cpus_allowed))
                return 0;
 
-#ifdef CONFIG_CPUMASK_OFFSTACK
-       /*
-        * Use the cpumasks in trialcs for tmpmasks when they are pointers
-        * to allocated cpumasks.
-        *
-        * Note that update_parent_subparts_cpumask() uses only addmask &
-        * delmask, but not new_cpus.
-        */
-       tmp.addmask  = trialcs->subparts_cpus;
-       tmp.delmask  = trialcs->effective_cpus;
-       tmp.new_cpus = NULL;
-#endif
+       if (alloc_cpumasks(NULL, &tmp))
+               return -ENOMEM;
 
        retval = validate_change(cs, trialcs);
 
@@ -1882,7 +1877,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
                retval = 0;
        }
        if (retval < 0)
-               return retval;
+               goto out_free;
 
        if (cs->partition_root_state) {
                if (invalidate)
@@ -1917,11 +1912,6 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
        }
        spin_unlock_irq(&callback_lock);
 
-#ifdef CONFIG_CPUMASK_OFFSTACK
-       /* Now trialcs->cpus_allowed is available */
-       tmp.new_cpus = trialcs->cpus_allowed;
-#endif
-
        /* effective_cpus will be updated here */
        update_cpumasks_hier(cs, &tmp, false);
 
@@ -1938,6 +1928,8 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
                /* Update CS_SCHED_LOAD_BALANCE and/or sched_domains */
                update_partition_sd_lb(cs, old_prs);
        }
+out_free:
+       free_cpumasks(NULL, &tmp);
        return 0;
 }
 
@@ -2346,13 +2338,11 @@ static int update_prstate(struct cpuset *cs, int new_prs)
 
                err = update_parent_subparts_cpumask(cs, partcmd_enable,
                                                     NULL, &tmpmask);
-               if (err)
-                       goto out;
        } else if (old_prs && new_prs) {
                /*
                 * A change in load balance state only, no change in cpumasks.
                 */
-               goto out;
+               ;
        } else {
                /*
                 * Switching back to member is always allowed even if it
@@ -2372,12 +2362,6 @@ static int update_prstate(struct cpuset *cs, int new_prs)
                        spin_unlock_irq(&callback_lock);
                }
        }
-
-       update_tasks_cpumask(parent, tmpmask.new_cpus);
-
-       if (parent->child_ecpus_count)
-               update_sibling_cpumasks(parent, cs, &tmpmask);
-
 out:
        /*
         * Make partition invalid & disable CS_CPU_EXCLUSIVE if an error