mm: constify nmask argument to set_mempolicy()

The nmask argument to set_mempolicy() is const according to the user-space
header numaif.h, and since the kernel does indeed not modify it, it might
as well be declared const in the kernel.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/syscalls.h

@@ -711,7 +711,7 @@ asmlinkage long sys_keyctl(int cmd, unsigned long arg2, unsigned long arg3,
 
 asmlinkage long sys_ioprio_set(int which, int who, int ioprio);
 asmlinkage long sys_ioprio_get(int which, int who);
-asmlinkage long sys_set_mempolicy(int mode, unsigned long __user *nmask,
+asmlinkage long sys_set_mempolicy(int mode, const unsigned long __user *nmask,
 				unsigned long maxnode);
 asmlinkage long sys_migrate_pages(pid_t pid, unsigned long maxnode,
 				const unsigned long __user *from,

mm/mempolicy.c

@@ -1383,7 +1383,7 @@ SYSCALL_DEFINE6(mbind, unsigned long, start, unsigned long, len,
 }
 
 /* Set the process memory policy */
-SYSCALL_DEFINE3(set_mempolicy, int, mode, unsigned long __user *, nmask,
+SYSCALL_DEFINE3(set_mempolicy, int, mode, const unsigned long __user *, nmask,
 		unsigned long, maxnode)
 {
 	int err;