mm: add kernel_mbind() helper; remove in-kernel call to syscall

Using the mm-internal kernel_mbind() helper allows us to get rid of the
mm-internal call to the sys_mbind() syscall.

This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-mm@kvack.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 7399ede02b5f2f8f13271fe59425e77176e4d48f..e4d7d4c0b253157ccfba7905930ff880084a7b6a 100644 (file)
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1336,9 +1336,9 @@ static int copy_nodes_to_user(unsigned long __user *mask, unsigned long maxnode,
        return copy_to_user(mask, nodes_addr(*nodes), copy) ? -EFAULT : 0;
 }
 
-SYSCALL_DEFINE6(mbind, unsigned long, start, unsigned long, len,
-               unsigned long, mode, const unsigned long __user *, nmask,
-               unsigned long, maxnode, unsigned, flags)
+static long kernel_mbind(unsigned long start, unsigned long len,
+                        unsigned long mode, const unsigned long __user *nmask,
+                        unsigned long maxnode, unsigned int flags)
 {
        nodemask_t nodes;
        int err;
@@ -1357,6 +1357,13 @@ SYSCALL_DEFINE6(mbind, unsigned long, start, unsigned long, len,
        return do_mbind(start, len, mode, mode_flags, &nodes, flags);
 }
 
+SYSCALL_DEFINE6(mbind, unsigned long, start, unsigned long, len,
+               unsigned long, mode, const unsigned long __user *, nmask,
+               unsigned long, maxnode, unsigned int, flags)
+{
+       return kernel_mbind(start, len, mode, nmask, maxnode, flags);
+}
+
 /* Set the process memory policy */
 SYSCALL_DEFINE3(set_mempolicy, int, mode, const unsigned long __user *, nmask,
                unsigned long, maxnode)
@@ -1575,7 +1582,7 @@ COMPAT_SYSCALL_DEFINE6(mbind, compat_ulong_t, start, compat_ulong_t, len,
                        return -EFAULT;
        }
 
-       return sys_mbind(start, len, mode, nm, nr_bits+1, flags);
+       return kernel_mbind(start, len, mode, nm, nr_bits+1, flags);
 }
 
 COMPAT_SYSCALL_DEFINE4(migrate_pages, compat_pid_t, pid,