[PATCH] page migration cleanup: move fallback handling into special function
Move the fallback code into a new fallback function and make the function
behave like any other migration function. This requires retaking the lock if
pageout() drops it.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
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 f65e69d..5a340f4 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -349,6 +349,42 @@
}
EXPORT_SYMBOL(buffer_migrate_page);
+static int fallback_migrate_page(struct address_space *mapping,
+ struct page *newpage, struct page *page)
+{
+ /*
+ * Default handling if a filesystem does not provide
+ * a migration function. We can only migrate clean
+ * pages so try to write out any dirty pages first.
+ */
+ if (PageDirty(page)) {
+ switch (pageout(page, mapping)) {
+ case PAGE_KEEP:
+ case PAGE_ACTIVATE:
+ return -EAGAIN;
+
+ case PAGE_SUCCESS:
+ /* Relock since we lost the lock */
+ lock_page(page);
+ /* Must retry since page state may have changed */
+ return -EAGAIN;
+
+ case PAGE_CLEAN:
+ ; /* try to migrate the page below */
+ }
+ }
+
+ /*
+ * Buffers may be managed in a filesystem specific way.
+ * We must have no buffers or drop them.
+ */
+ if (page_has_buffers(page) &&
+ !try_to_release_page(page, GFP_KERNEL))
+ return -EAGAIN;
+
+ return migrate_page(mapping, newpage, page);
+}
+
/*
* migrate_pages
*
@@ -478,7 +514,7 @@
if (!mapping)
goto unlock_both;
- if (mapping->a_ops->migratepage) {
+ if (mapping->a_ops->migratepage)
/*
* Most pages have a mapping and most filesystems
* should provide a migration function. Anonymous
@@ -488,56 +524,8 @@
*/
rc = mapping->a_ops->migratepage(mapping,
newpage, page);
- goto unlock_both;
- }
-
- /*
- * Default handling if a filesystem does not provide
- * a migration function. We can only migrate clean
- * pages so try to write out any dirty pages first.
- */
- if (PageDirty(page)) {
- switch (pageout(page, mapping)) {
- case PAGE_KEEP:
- case PAGE_ACTIVATE:
- goto unlock_both;
-
- case PAGE_SUCCESS:
- unlock_page(newpage);
- goto next;
-
- case PAGE_CLEAN:
- ; /* try to migrate the page below */
- }
- }
-
- /*
- * Buffers are managed in a filesystem specific way.
- * We must have no buffers or drop them.
- */
- if (!page_has_buffers(page) ||
- try_to_release_page(page, GFP_KERNEL)) {
- rc = migrate_page(mapping, newpage, page);
- goto unlock_both;
- }
-
- /*
- * On early passes with mapped pages simply
- * retry. There may be a lock held for some
- * buffers that may go away. Later
- * swap them out.
- */
- if (pass > 4) {
- /*
- * Persistently unable to drop buffers..... As a
- * measure of last resort we fall back to
- * swap_page().
- */
- unlock_page(newpage);
- newpage = NULL;
- rc = swap_page(page);
- goto next;
- }
+ else
+ rc = fallback_migrate_page(mapping, newpage, page);
unlock_both:
unlock_page(newpage);