mm: mlock: add new mlock system call

With the refactored mlock code, introduce a new system call for mlock. 
The new call will allow the user to specify what lock states are being
added.  mlock2 is trivial at the moment, but a follow on patch will add a
new mlock state making it useful.

Signed-off-by: Eric B Munson <emunson@akamai.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arch/x86/entry/syscalls/syscall_32.tbl

@@ -366,3 +366,4 @@
 357	i386	bpf			sys_bpf
 358	i386	execveat		sys_execveat			stub32_execveat
 359	i386	userfaultfd		sys_userfaultfd
+360	i386	mlock2			sys_mlock2

arch/x86/entry/syscalls/syscall_64.tbl

@@ -330,6 +330,7 @@
 321	common	bpf			sys_bpf
 322	64	execveat		stub_execveat
 323	common	userfaultfd		sys_userfaultfd
+324	common	mlock2			sys_mlock2
 
 #
 # x32-specific system call numbers start at 512 to avoid cache impact

include/linux/syscalls.h

@@ -885,4 +885,6 @@ asmlinkage long sys_execveat(int dfd, const char __user *filename,
 			const char __user *const __user *argv,
 			const char __user *const __user *envp, int flags);
 
+asmlinkage long sys_mlock2(unsigned long start, size_t len, int flags);
+
 #endif

include/uapi/asm-generic/unistd.h

@@ -709,9 +709,11 @@ __SYSCALL(__NR_memfd_create, sys_memfd_create)
 __SYSCALL(__NR_bpf, sys_bpf)
 #define __NR_execveat 281
 __SC_COMP(__NR_execveat, sys_execveat, compat_sys_execveat)
+#define __NR_mlock2 282
+__SYSCALL(__NR_mlock2, sys_mlock2)
 
 #undef __NR_syscalls
-#define __NR_syscalls 282
+#define __NR_syscalls 283
 
 /*
  * All syscalls below here should go away really,

kernel/sys_ni.c

@@ -193,6 +193,7 @@ cond_syscall(sys_mlock);
 cond_syscall(sys_munlock);
 cond_syscall(sys_mlockall);
 cond_syscall(sys_munlockall);
+cond_syscall(sys_mlock2);
 cond_syscall(sys_mincore);
 cond_syscall(sys_madvise);
 cond_syscall(sys_mremap);

mm/mlock.c

@@ -644,6 +644,15 @@ SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
 	return do_mlock(start, len, VM_LOCKED);
 }
 
+SYSCALL_DEFINE3(mlock2, unsigned long, start, size_t, len, int, flags)
+{
+	vm_flags_t vm_flags = VM_LOCKED;
+	if (flags)
+		return -EINVAL;
+
+	return do_mlock(start, len, vm_flags);
+}
+
 SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
 {
 	int ret;