[PATCH] Allow migration of mlocked pages

Hugh clarified the role of VM_LOCKED.  So we can now implement page
migration for mlocked pages.

Allow the migration of mlocked pages.  This means that try_to_unmap must
unmap mlocked pages in the migration case.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Acked-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 8 insertions, 11 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index 0576c0535988..3f1e0c2c942c 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -616,15 +616,13 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
         /*
          * Establish migration ptes or remove ptes
          */
-        if (try_to_unmap(page, 1) != SWAP_FAIL) {
-                if (!page_mapped(page))
-                        rc = move_to_new_page(newpage, page);
-        } else
-                /* A vma has VM_LOCKED set -> permanent failure */
-                rc = -EPERM;
+        try_to_unmap(page, 1);
+        if (!page_mapped(page))
+                rc = move_to_new_page(newpage, page);
 
         if (rc)
                 remove_migration_ptes(page, page);
+
 unlock:
         unlock_page(page);
 
diff --git a/mm/rmap.c b/mm/rmap.c
index 882a85826bb2..e76909e880ca 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -562,9 +562,8 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
          * If it's recently referenced (perhaps page_referenced
          * skipped over this mm) then we should reactivate it.
          */
-        if ((vma->vm_flags & VM_LOCKED) ||
-                        (ptep_clear_flush_young(vma, address, pte)
-                                && !migration)) {
+        if (!migration && ((vma->vm_flags & VM_LOCKED) ||
+                        (ptep_clear_flush_young(vma, address, pte)))) {
                 ret = SWAP_FAIL;
                 goto out_unmap;
         }
@@ -771,7 +770,7 @@ static int try_to_unmap_file(struct page *page, int migration)
 
         list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
                                                 shared.vm_set.list) {
-                if (vma->vm_flags & VM_LOCKED)
+                if ((vma->vm_flags & VM_LOCKED) && !migration)
                         continue;
                 cursor = (unsigned long) vma->vm_private_data;
                 if (cursor > max_nl_cursor)
@@ -805,7 +804,7 @@ static int try_to_unmap_file(struct page *page, int migration)
         do {
                 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
                                                 shared.vm_set.list) {
-                        if (vma->vm_flags & VM_LOCKED)
+                        if ((vma->vm_flags & VM_LOCKED) && !migration)
                                 continue;
                         cursor = (unsigned long) vma->vm_private_data;
                         while ( cursor < max_nl_cursor &&