[PATCH] page migration cleanup: drop nr_refs in remove_references()
Drop nr_refs parameter from migrate_page_remove_references()
The nr_refs parameter is not really useful since the number of remaining
references is always
1 for anonymous pages without a mapping
2 for pages with a mapping
3 for pages with a mapping and PagePrivate set.
Remove the early check for the number of references since we are checking
page_mapcount() earlier. Ultimately only the refcount matters after the
tree_lock has been obtained.
Signed-off-by: Christoph Lameter <clameter@sgi.coim>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/mm/migrate.c b/mm/migrate.c
index be3f141..2803a66 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -168,19 +168,19 @@
/*
* Remove references for a page and establish the new page with the correct
* basic settings to be able to stop accesses to the page.
+ *
+ * The number of remaining references must be:
+ * 1 for anonymous pages without a mapping
+ * 2 for pages with a mapping
+ * 3 for pages with a mapping and PagePrivate set.
*/
static int migrate_page_remove_references(struct page *newpage,
- struct page *page, int nr_refs)
+ struct page *page)
{
struct address_space *mapping = page_mapping(page);
struct page **radix_pointer;
- /*
- * Avoid doing any of the following work if the page count
- * indicates that the page is in use or truncate has removed
- * the page.
- */
- if (!mapping || page_mapcount(page) + nr_refs != page_count(page))
+ if (!mapping)
return -EAGAIN;
/*
@@ -218,7 +218,8 @@
&mapping->page_tree,
page_index(page));
- if (!page_mapping(page) || page_count(page) != nr_refs ||
+ if (!page_mapping(page) ||
+ page_count(page) != 2 + !!PagePrivate(page) ||
*radix_pointer != page) {
write_unlock_irq(&mapping->tree_lock);
return -EAGAIN;
@@ -309,7 +310,7 @@
BUG_ON(PageWriteback(page)); /* Writeback must be complete */
- rc = migrate_page_remove_references(newpage, page, 2);
+ rc = migrate_page_remove_references(newpage, page);
if (rc)
return rc;
@@ -348,7 +349,7 @@
head = page_buffers(page);
- rc = migrate_page_remove_references(newpage, page, 3);
+ rc = migrate_page_remove_references(newpage, page);
if (rc)
return rc;