[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>

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) {
+	try_to_unmap(page, 1);
 	if (!page_mapped(page))
 		rc = move_to_new_page(newpage, page);
-	} else
-		/* A vma has VM_LOCKED set -> permanent failure */
-		rc = -EPERM;
 
 	if (rc)
 		remove_migration_ptes(page, page);
+
 unlock:
 	unlock_page(page);
 

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 &&