sched: convert sys_sched_getaffinity() to cpumask_var_t.

Impact: stack usage reduction

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

Some jiggling here to make sure we always exit at the bottom (so we hit
the free_cpumask_var there).

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

diff --git a/kernel/sched.c b/kernel/sched.c
index 67383e7..6deff24 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5499,19 +5499,24 @@ asmlinkage long sys_sched_getaffinity(pid_t pid, unsigned int len,
                                      unsigned long __user *user_mask_ptr)
 {
        int ret;
-       cpumask_t mask;
+       cpumask_var_t mask;
 
-       if (len < sizeof(cpumask_t))
+       if (len < cpumask_size())
                return -EINVAL;
 
-       ret = sched_getaffinity(pid, &mask);
-       if (ret < 0)
-               return ret;
+       if (!alloc_cpumask_var(&mask, GFP_KERNEL))
+               return -ENOMEM;
 
-       if (copy_to_user(user_mask_ptr, &mask, sizeof(cpumask_t)))
-               return -EFAULT;
+       ret = sched_getaffinity(pid, mask);
+       if (ret == 0) {
+               if (copy_to_user(user_mask_ptr, mask, cpumask_size()))
+                       ret = -EFAULT;
+               else
+                       ret = cpumask_size();
+       }
+       free_cpumask_var(mask);
 
-       return sizeof(cpumask_t);
+       return ret;
 }
 
 /**