mm: add kernel_migrate_pages() helper, move compat syscall to mm/mempolicy.c

Move compat_sys_migrate_pages() to mm/mempolicy.c and make it call a newly
introduced helper -- kernel_migrate_pages() -- instead of the 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/kernel/compat.c b/kernel/compat.c
index 3f5fa89..51bdf18 100644 (file)
--- a/kernel/compat.c
+++ b/kernel/compat.c
@@ -508,39 +508,6 @@ COMPAT_SYSCALL_DEFINE6(move_pages, pid_t, pid, compat_ulong_t, nr_pages,
        }
        return sys_move_pages(pid, nr_pages, pages, nodes, status, flags);
 }
-
-COMPAT_SYSCALL_DEFINE4(migrate_pages, compat_pid_t, pid,
-                      compat_ulong_t, maxnode,
-                      const compat_ulong_t __user *, old_nodes,
-                      const compat_ulong_t __user *, new_nodes)
-{
-       unsigned long __user *old = NULL;
-       unsigned long __user *new = NULL;
-       nodemask_t tmp_mask;
-       unsigned long nr_bits;
-       unsigned long size;
-
-       nr_bits = min_t(unsigned long, maxnode - 1, MAX_NUMNODES);
-       size = ALIGN(nr_bits, BITS_PER_LONG) / 8;
-       if (old_nodes) {
-               if (compat_get_bitmap(nodes_addr(tmp_mask), old_nodes, nr_bits))
-                       return -EFAULT;
-               old = compat_alloc_user_space(new_nodes ? size * 2 : size);
-               if (new_nodes)
-                       new = old + size / sizeof(unsigned long);
-               if (copy_to_user(old, nodes_addr(tmp_mask), size))
-                       return -EFAULT;
-       }
-       if (new_nodes) {
-               if (compat_get_bitmap(nodes_addr(tmp_mask), new_nodes, nr_bits))
-                       return -EFAULT;
-               if (new == NULL)
-                       new = compat_alloc_user_space(size);
-               if (copy_to_user(new, nodes_addr(tmp_mask), size))
-                       return -EFAULT;
-       }
-       return sys_migrate_pages(pid, nr_bits + 1, old, new);
-}
 #endif
 
 /*

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index d879f1d..7399ede 100644 (file)
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1377,9 +1377,9 @@ SYSCALL_DEFINE3(set_mempolicy, int, mode, const unsigned long __user *, nmask,
        return do_set_mempolicy(mode, flags, &nodes);
 }
 
-SYSCALL_DEFINE4(migrate_pages, pid_t, pid, unsigned long, maxnode,
-               const unsigned long __user *, old_nodes,
-               const unsigned long __user *, new_nodes)
+static int kernel_migrate_pages(pid_t pid, unsigned long maxnode,
+                               const unsigned long __user *old_nodes,
+                               const unsigned long __user *new_nodes)
 {
        struct mm_struct *mm = NULL;
        struct task_struct *task;
@@ -1469,6 +1469,13 @@ out_put:
 
 }
 
+SYSCALL_DEFINE4(migrate_pages, pid_t, pid, unsigned long, maxnode,
+               const unsigned long __user *, old_nodes,
+               const unsigned long __user *, new_nodes)
+{
+       return kernel_migrate_pages(pid, maxnode, old_nodes, new_nodes);
+}
+
 
 /* Retrieve NUMA policy */
 SYSCALL_DEFINE5(get_mempolicy, int __user *, policy,
@@ -1571,7 +1578,40 @@ COMPAT_SYSCALL_DEFINE6(mbind, compat_ulong_t, start, compat_ulong_t, len,
        return sys_mbind(start, len, mode, nm, nr_bits+1, flags);
 }
 
-#endif
+COMPAT_SYSCALL_DEFINE4(migrate_pages, compat_pid_t, pid,
+                      compat_ulong_t, maxnode,
+                      const compat_ulong_t __user *, old_nodes,
+                      const compat_ulong_t __user *, new_nodes)
+{
+       unsigned long __user *old = NULL;
+       unsigned long __user *new = NULL;
+       nodemask_t tmp_mask;
+       unsigned long nr_bits;
+       unsigned long size;
+
+       nr_bits = min_t(unsigned long, maxnode - 1, MAX_NUMNODES);
+       size = ALIGN(nr_bits, BITS_PER_LONG) / 8;
+       if (old_nodes) {
+               if (compat_get_bitmap(nodes_addr(tmp_mask), old_nodes, nr_bits))
+                       return -EFAULT;
+               old = compat_alloc_user_space(new_nodes ? size * 2 : size);
+               if (new_nodes)
+                       new = old + size / sizeof(unsigned long);
+               if (copy_to_user(old, nodes_addr(tmp_mask), size))
+                       return -EFAULT;
+       }
+       if (new_nodes) {
+               if (compat_get_bitmap(nodes_addr(tmp_mask), new_nodes, nr_bits))
+                       return -EFAULT;
+               if (new == NULL)
+                       new = compat_alloc_user_space(size);
+               if (copy_to_user(new, nodes_addr(tmp_mask), size))
+                       return -EFAULT;
+       }
+       return kernel_migrate_pages(pid, nr_bits + 1, old, new);
+}
+
+#endif /* CONFIG_COMPAT */
 
 struct mempolicy *__get_vma_policy(struct vm_area_struct *vma,
                                                unsigned long addr)