[PATCH] SwapMig: Switch error handling in migrate_pages to use -Exx
Use -Exxx instead of numeric return codes and cleanup the code in
migrate_pages() using -Exx error codes.
Consolidate successful migration handling
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/vmscan.c b/mm/vmscan.c
index 5eecb51..bf903b2 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -606,10 +606,6 @@
/*
* swapout a single page
* page is locked upon entry, unlocked on exit
- *
- * return codes:
- * 0 = complete
- * 1 = retry
*/
static int swap_page(struct page *page)
{
@@ -650,7 +646,7 @@
unlock_page(page);
retry:
- return 1;
+ return -EAGAIN;
}
/*
* migrate_pages
@@ -669,6 +665,8 @@
* is only swapping out pages and never touches the second
* list. The direct migration patchset
* extends this function to avoid the use of swap.
+ *
+ * Return: Number of pages not migrated when "to" ran empty.
*/
int migrate_pages(struct list_head *from, struct list_head *to,
struct list_head *moved, struct list_head *failed)
@@ -679,6 +677,7 @@
struct page *page;
struct page *page2;
int swapwrite = current->flags & PF_SWAPWRITE;
+ int rc;
if (!swapwrite)
current->flags |= PF_SWAPWRITE;
@@ -689,22 +688,23 @@
list_for_each_entry_safe(page, page2, from, lru) {
cond_resched();
- if (page_count(page) == 1) {
+ rc = 0;
+ if (page_count(page) == 1)
/* page was freed from under us. So we are done. */
- list_move(&page->lru, moved);
- continue;
- }
+ goto next;
+
/*
* Skip locked pages during the first two passes to give the
* functions holding the lock time to release the page. Later we
* use lock_page() to have a higher chance of acquiring the
* lock.
*/
+ rc = -EAGAIN;
if (pass > 2)
lock_page(page);
else
if (TestSetPageLocked(page))
- goto retry_later;
+ goto next;
/*
* Only wait on writeback if we have already done a pass where
@@ -713,18 +713,19 @@
if (pass > 0) {
wait_on_page_writeback(page);
} else {
- if (PageWriteback(page)) {
- unlock_page(page);
- goto retry_later;
- }
+ 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)) {
- unlock_page(page);
- list_move(&page->lru, failed);
- nr_failed++;
- continue;
+ rc = -ENOMEM;
+ goto unlock_page;
}
}
@@ -732,12 +733,23 @@
* Page is properly locked and writeback is complete.
* Try to migrate the page.
*/
- if (!swap_page(page)) {
+ rc = swap_page(page);
+ goto next;
+
+unlock_page:
+ unlock_page(page);
+
+next:
+ if (rc == -EAGAIN) {
+ retry++;
+ } else if (rc) {
+ /* Permanent failure */
+ list_move(&page->lru, failed);
+ nr_failed++;
+ } else {
+ /* Success */
list_move(&page->lru, moved);
- continue;
}
-retry_later:
- retry++;
}
if (retry && pass++ < 10)
goto redo;