mm: make CONFIG_MIGRATION available w/o CONFIG_NUMA

We'd like to support CONFIG_MEMORY_HOTREMOVE on s390, which depends on
CONFIG_MIGRATION.  So far, CONFIG_MIGRATION is only available with NUMA
support.

This patch makes CONFIG_MIGRATION selectable for architectures that define
ARCH_ENABLE_MEMORY_HOTREMOVE.  When MIGRATION is enabled w/o NUMA, the
kernel won't compile because migrate_vmas() does not know about
vm_ops->migrate() and vma_migratable() does not know about policy_zone.
To fix this, those two functions can be restricted to '#ifdef CONFIG_NUMA'
because they are not being used w/o NUMA.  vma_migratable() is moved over
from migrate.h to mempolicy.h.

[kosaki.motohiro@jp.fujitsu.com: build fix]
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: KOSAKI Motorhiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
index 3a39570b81b8..085c903fe0f1 100644
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -59,6 +59,7 @@ enum {
 #include <linux/rbtree.h>
 #include <linux/spinlock.h>
 #include <linux/nodemask.h>
+#include <linux/pagemap.h>
 
 struct mm_struct;
 
@@ -220,6 +221,24 @@ extern int mpol_parse_str(char *str, struct mempolicy **mpol, int no_context);
 extern int mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol,
                         int no_context);
 #endif
+
+/* Check if a vma is migratable */
+static inline int vma_migratable(struct vm_area_struct *vma)
+{
+        if (vma->vm_flags & (VM_IO|VM_HUGETLB|VM_PFNMAP|VM_RESERVED))
+                return 0;
+        /*
+         * Migration allocates pages in the highest zone. If we cannot
+         * do so then migration (at least from node to node) is not
+         * possible.
+         */
+        if (vma->vm_file &&
+                gfp_zone(mapping_gfp_mask(vma->vm_file->f_mapping))
+                                                                < policy_zone)
+                        return 0;
+        return 1;
+}
+
 #else
 
 struct mempolicy {};