sched: convert struct (sys_)sched_setaffinity() to cpumask_var_t.

Impact: stack usage reduction

Dynamically allocating cpumasks (when CONFIG_CPUMASK_OFFSTACK) saves
space on the stack.  cpumask_var_t is just a struct cpumask for
!CONFIG_CPUMASK_OFFSTACK.

Note the removal of the initializer of new_mask: since the first thing
we did was "cpus_and(new_mask, new_mask, cpus_allowed)" I just changed
that to "cpumask_and(new_mask, in_mask, cpus_allowed);".

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 27 insertions, 13 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index f7dee2029e4d..2d4ff91e0c97 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5378,8 +5378,7 @@ out_unlock:
 
 long sched_setaffinity(pid_t pid, const cpumask_t *in_mask)
 {
-        cpumask_t cpus_allowed;
-        cpumask_t new_mask = *in_mask;
+        cpumask_var_t cpus_allowed, new_mask;
         struct task_struct *p;
         int retval;
 
@@ -5401,6 +5400,14 @@ long sched_setaffinity(pid_t pid, const cpumask_t *in_mask)
         get_task_struct(p);
         read_unlock(&tasklist_lock);
 
+        if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
+                retval = -ENOMEM;
+                goto out_put_task;
+        }
+        if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
+                retval = -ENOMEM;
+                goto out_free_cpus_allowed;
+        }
         retval = -EPERM;
         if ((current->euid != p->euid) && (current->euid != p->uid) &&
                         !capable(CAP_SYS_NICE))
@@ -5410,24 +5417,28 @@ long sched_setaffinity(pid_t pid, const cpumask_t *in_mask)
         if (retval)
                 goto out_unlock;
 
-        cpuset_cpus_allowed(p, &cpus_allowed);
-        cpus_and(new_mask, new_mask, cpus_allowed);
+        cpuset_cpus_allowed(p, cpus_allowed);
+        cpumask_and(new_mask, in_mask, cpus_allowed);
  again:
-        retval = set_cpus_allowed_ptr(p, &new_mask);
+        retval = set_cpus_allowed_ptr(p, new_mask);
 
         if (!retval) {
-                cpuset_cpus_allowed(p, &cpus_allowed);
-                if (!cpus_subset(new_mask, cpus_allowed)) {
+                cpuset_cpus_allowed(p, cpus_allowed);
+                if (!cpumask_subset(new_mask, cpus_allowed)) {
                         /*
                          * We must have raced with a concurrent cpuset
                          * update. Just reset the cpus_allowed to the
                          * cpuset's cpus_allowed
                          */
-                        new_mask = cpus_allowed;
+                        cpumask_copy(new_mask, cpus_allowed);
                         goto again;
                 }
         }
 out_unlock:
+        free_cpumask_var(new_mask);
+out_free_cpus_allowed:
+        free_cpumask_var(cpus_allowed);
+out_put_task:
         put_task_struct(p);
         put_online_cpus();
         return retval;
@@ -5453,14 +5464,17 @@ static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
 asmlinkage long sys_sched_setaffinity(pid_t pid, unsigned int len,
                                       unsigned long __user *user_mask_ptr)
 {
-        cpumask_t new_mask;
+        cpumask_var_t new_mask;
         int retval;
 
-        retval = get_user_cpu_mask(user_mask_ptr, len, &new_mask);
-        if (retval)
-                return retval;
+        if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
+                return -ENOMEM;
 
-        return sched_setaffinity(pid, &new_mask);
+        retval = get_user_cpu_mask(user_mask_ptr, len, new_mask);
+        if (retval == 0)
+                retval = sched_setaffinity(pid, new_mask);
+        free_cpumask_var(new_mask);
+        return retval;
 }
 
 long sched_getaffinity(pid_t pid, cpumask_t *mask)