cpumask: convert kernel/compat.c

Impact: Reduce stack usage, use new cpumask API.

Straightforward conversion; cpumasks' size is given by cpumask_size() (now
a variable rather than fixed) and on-stack cpu masks use cpumask_var_t.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

kernel/compat.c

@@ -454,16 +454,16 @@ asmlinkage long compat_sys_waitid(int which, compat_pid_t pid,
 }
 
 static int compat_get_user_cpu_mask(compat_ulong_t __user *user_mask_ptr,
-				    unsigned len, cpumask_t *new_mask)
+				    unsigned len, struct cpumask *new_mask)
 {
 	unsigned long *k;
 
-	if (len < sizeof(cpumask_t))
-		memset(new_mask, 0, sizeof(cpumask_t));
-	else if (len > sizeof(cpumask_t))
-		len = sizeof(cpumask_t);
+	if (len < cpumask_size())
+		memset(new_mask, 0, cpumask_size());
+	else if (len > cpumask_size())
+		len = cpumask_size();
 
-	k = cpus_addr(*new_mask);
+	k = cpumask_bits(new_mask);
 	return compat_get_bitmap(k, user_mask_ptr, len * 8);
 }
 
@@ -471,40 +471,51 @@ asmlinkage long compat_sys_sched_setaffinity(compat_pid_t pid,
 					     unsigned int len,
 					     compat_ulong_t __user *user_mask_ptr)
 {
-	cpumask_t new_mask;
+	cpumask_var_t new_mask;
 	int retval;
 
-	retval = compat_get_user_cpu_mask(user_mask_ptr, len, &new_mask);
+	if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
+		return -ENOMEM;
+
+	retval = compat_get_user_cpu_mask(user_mask_ptr, len, new_mask);
 	if (retval)
-		return retval;
+		goto out;
 
-	return sched_setaffinity(pid, &new_mask);
+	retval = sched_setaffinity(pid, new_mask);
+out:
+	free_cpumask_var(new_mask);
+	return retval;
 }
 
 asmlinkage long compat_sys_sched_getaffinity(compat_pid_t pid, unsigned int len,
 					     compat_ulong_t __user *user_mask_ptr)
 {
 	int ret;
-	cpumask_t mask;
+	cpumask_var_t mask;
 	unsigned long *k;
-	unsigned int min_length = sizeof(cpumask_t);
+	unsigned int min_length = cpumask_size();
 
-	if (NR_CPUS <= BITS_PER_COMPAT_LONG)
+	if (nr_cpu_ids <= BITS_PER_COMPAT_LONG)
 		min_length = sizeof(compat_ulong_t);
 
 	if (len < min_length)
 		return -EINVAL;
 
-	ret = sched_getaffinity(pid, &mask);
+	if (!alloc_cpumask_var(&mask, GFP_KERNEL))
+		return -ENOMEM;
+
+	ret = sched_getaffinity(pid, mask);
 	if (ret < 0)
-		return ret;
+		goto out;
 
-	k = cpus_addr(mask);
+	k = cpumask_bits(mask);
 	ret = compat_put_bitmap(user_mask_ptr, k, min_length * 8);
-	if (ret)
-		return ret;
+	if (ret == 0)
+		ret = min_length;
 
-	return min_length;
+out:
+	free_cpumask_var(mask);
+	return ret;
 }
 
 int get_compat_itimerspec(struct itimerspec *dst,