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>

4 files changed, 21 insertions, 23 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 {};
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index e10a90a93b5d..03aea612d284 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -3,28 +3,10 @@
 
 #include <linux/mm.h>
 #include <linux/mempolicy.h>
-#include <linux/pagemap.h>
 
 typedef struct page *new_page_t(struct page *, unsigned long private, int **);
 
 #ifdef CONFIG_MIGRATION
-/* 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;
-}
-
 extern int isolate_lru_page(struct page *p, struct list_head *pagelist);
 extern int putback_lru_pages(struct list_head *l);
 extern int migrate_page(struct address_space *,
@@ -39,9 +21,6 @@ extern int migrate_vmas(struct mm_struct *mm,
                 const nodemask_t *from, const nodemask_t *to,
                 unsigned long flags);
 #else
-static inline int vma_migratable(struct vm_area_struct *vma)
-                                        { return 0; }
-
 static inline int isolate_lru_page(struct page *p, struct list_head *list)
                                         { return -ENOSYS; }
 static inline int putback_lru_pages(struct list_head *l) { return 0; }
diff --git a/mm/Kconfig b/mm/Kconfig
index c4de85285bb4..aa799007a11b 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -174,7 +174,7 @@ config SPLIT_PTLOCK_CPUS
 config MIGRATION
         bool "Page migration"
         def_bool y
-        depends on NUMA
+        depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE
         help
           Allows the migration of the physical location of pages of processes
           while the virtual addresses are not changed. This is useful for
diff --git a/mm/migrate.c b/mm/migrate.c
index e7d13a708da0..376cceba82f9 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1071,7 +1071,6 @@ out2:
         mmput(mm);
         return err;
 }
-#endif
 
 /*
  * Call migration functions in the vma_ops that may prepare
@@ -1093,3 +1092,4 @@ int migrate_vmas(struct mm_struct *mm, const nodemask_t *to,
         }
         return err;
 }
+#endif