[PATCH] Swapless page migration: rip out swap based logic

Rip the page migration logic out.

Remove all code that has to do with swapping during page migration.

This also guts the ability to migrate pages to swap.  No one used that so lets
let it go for good.

Page migration should be a bit broken after this patch.

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

1 files changed, 3 insertions, 72 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index 0a011e421bb4..81721a061d50 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -70,10 +70,6 @@ int isolate_lru_page(struct page *page, struct list_head *pagelist)
  */
 int migrate_prep(void)
 {
-	/* Must have swap device for migration */
-	if (nr_swap_pages <= 0)
-		return -ENODEV;
-
 	/*
 	 * Clear the LRU lists so pages can be isolated.
 	 * Note that pages may be moved off the LRU after we have
@@ -246,52 +242,6 @@ out:
 }
 
 /*
- * swapout a single page
- * page is locked upon entry, unlocked on exit
- */
-static int swap_page(struct page *page)
-{
-	struct address_space *mapping = page_mapping(page);
-
-	if (page_mapped(page) && mapping)
-		if (try_to_unmap(page, 1) != SWAP_SUCCESS)
-			goto unlock_retry;
-
-	if (PageDirty(page)) {
-		/* Page is dirty, try to write it out here */
-		switch(pageout(page, mapping)) {
-		case PAGE_KEEP:
-		case PAGE_ACTIVATE:
-			goto unlock_retry;
-
-		case PAGE_SUCCESS:
-			goto retry;
-
-		case PAGE_CLEAN:
-			; /* try to free the page below */
-		}
-	}
-
-	if (PagePrivate(page)) {
-		if (!try_to_release_page(page, GFP_KERNEL) ||
-		    (!mapping && page_count(page) == 1))
-			goto unlock_retry;
-	}
-
-	if (remove_mapping(mapping, page)) {
-		/* Success */
-		unlock_page(page);
-		return 0;
-	}
-
-unlock_retry:
-	unlock_page(page);
-
-retry:
-	return -EAGAIN;
-}
-
-/*
  * Replace the page in the mapping.
  *
  * The number of remaining references must be:
@@ -517,8 +467,7 @@ static int fallback_migrate_page(struct address_space *mapping,
  * Two lists are passed to this function. The first list
  * contains the pages isolated from the LRU to be migrated.
  * The second list contains new pages that the pages isolated
- * can be moved to. If the second list is NULL then all
- * pages are swapped out.
+ * can be moved to.
  *
  * The function returns after 10 attempts or if no pages
  * are movable anymore because to has become empty
@@ -574,29 +523,11 @@ redo:
 		 * Only wait on writeback if we have already done a pass where
 		 * we we may have triggered writeouts for lots of pages.
 		 */
-		if (pass > 0) {
+		if (pass > 0)
 			wait_on_page_writeback(page);
-		} else {
+		else
 			if (PageWriteback(page))
 				goto unlock_page;
-		}
-
-		/*
-		 * Anonymous pages must have swap cache references otherwise
-		 * the information contained in the page maps cannot be
-		 * preserved.
-		 */
-		if (PageAnon(page) && !PageSwapCache(page)) {
-			if (!add_to_swap(page, GFP_KERNEL)) {
-				rc = -ENOMEM;
-				goto unlock_page;
-			}
-		}
-
-		if (!to) {
-			rc = swap_page(page);
-			goto next;
-		}
 
 		/*
 		 * Establish swap ptes for anonymous pages or destroy pte