}
/*
- * Remove references for a page and establish the new page with the correct
- * basic settings to be able to stop accesses to the page.
+ * Replace the page in the mapping.
+ *
+ * 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)
+static int migrate_page_move_mapping(struct address_space *mapping,
+ struct page *newpage, 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))
- return -EAGAIN;
-
- /*
- * Establish swap ptes for anonymous pages or destroy pte
- * maps for files.
- *
- * In order to reestablish file backed mappings the fault handlers
- * will take the radix tree_lock which may then be used to stop
- * processses from accessing this page until the new page is ready.
- *
- * A process accessing via a swap pte (an anonymous page) will take a
- * page_lock on the old page which will block the process until the
- * migration attempt is complete. At that time the PageSwapCache bit
- * will be examined. If the page was migrated then the PageSwapCache
- * bit will be clear and the operation to retrieve the page will be
- * retried which will find the new page in the radix tree. Then a new
- * direct mapping may be generated based on the radix tree contents.
- *
- * If the page was not migrated then the PageSwapCache bit
- * is still set and the operation may continue.
- */
- if (try_to_unmap(page, 1) == SWAP_FAIL)
- /* A vma has VM_LOCKED set -> permanent failure */
- return -EPERM;
-
- /*
- * Give up if we were unable to remove all mappings.
- */
- if (page_mapcount(page))
- return -EAGAIN;
-
write_lock_irq(&mapping->tree_lock);
radix_pointer = (struct page **)radix_tree_lookup_slot(
&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;
/*
* Now we know that no one else is looking at the page.
- *
- * Certain minimal information about a page must be available
- * in order for other subsystems to properly handle the page if they
- * find it through the radix tree update before we are finished
- * copying the page.
*/
get_page(newpage);
- newpage->index = page->index;
- newpage->mapping = page->mapping;
if (PageSwapCache(page)) {
SetPageSwapCache(newpage);
set_page_private(newpage, page_private(page));
***********************************************************/
/* Always fail migration. Used for mappings that are not movable */
-int fail_migrate_page(struct page *newpage, struct page *page)
+int fail_migrate_page(struct address_space *mapping,
+ struct page *newpage, struct page *page)
{
return -EIO;
}
*
* Pages are locked upon entry and exit.
*/
-int migrate_page(struct page *newpage, struct page *page)
+int migrate_page(struct address_space *mapping,
+ struct page *newpage, struct page *page)
{
int rc;
BUG_ON(PageWriteback(page)); /* Writeback must be complete */
- rc = migrate_page_remove_references(newpage, page, 2);
+ rc = migrate_page_move_mapping(mapping, newpage, page);
if (rc)
return rc;
* if the underlying filesystem guarantees that no other references to "page"
* exist.
*/
-int buffer_migrate_page(struct page *newpage, struct page *page)
+int buffer_migrate_page(struct address_space *mapping,
+ struct page *newpage, struct page *page)
{
- struct address_space *mapping = page->mapping;
struct buffer_head *bh, *head;
int rc;
- if (!mapping)
- return -EAGAIN;
-
if (!page_has_buffers(page))
- return migrate_page(newpage, page);
+ return migrate_page(mapping, newpage, page);
head = page_buffers(page);
- rc = migrate_page_remove_references(newpage, page, 3);
+ rc = migrate_page_move_mapping(mapping, newpage, page);
if (rc)
return rc;
goto next;
}
+ /*
+ * Establish swap ptes for anonymous pages or destroy pte
+ * maps for files.
+ *
+ * In order to reestablish file backed mappings the fault handlers
+ * will take the radix tree_lock which may then be used to stop
+ * processses from accessing this page until the new page is ready.
+ *
+ * A process accessing via a swap pte (an anonymous page) will take a
+ * page_lock on the old page which will block the process until the
+ * migration attempt is complete. At that time the PageSwapCache bit
+ * will be examined. If the page was migrated then the PageSwapCache
+ * bit will be clear and the operation to retrieve the page will be
+ * retried which will find the new page in the radix tree. Then a new
+ * direct mapping may be generated based on the radix tree contents.
+ *
+ * If the page was not migrated then the PageSwapCache bit
+ * is still set and the operation may continue.
+ */
+ rc = -EPERM;
+ if (try_to_unmap(page, 1) == SWAP_FAIL)
+ /* A vma has VM_LOCKED set -> permanent failure */
+ goto unlock_page;
+
+ rc = -EAGAIN;
+ if (page_mapped(page))
+ goto unlock_page;
+
newpage = lru_to_page(to);
lock_page(newpage);
+ /* Prepare mapping for the new page.*/
+ newpage->index = page->index;
+ newpage->mapping = page->mapping;
/*
* Pages are properly locked and writeback is complete.
* own migration function. This is the most common
* path for page migration.
*/
- rc = mapping->a_ops->migratepage(newpage, page);
+ rc = mapping->a_ops->migratepage(mapping,
+ newpage, page);
goto unlock_both;
}
- /* Make sure the dirty bit is up to date */
- if (try_to_unmap(page, 1) == SWAP_FAIL) {
- rc = -EPERM;
- goto unlock_both;
- }
-
- if (page_mapcount(page)) {
- rc = -EAGAIN;
- goto unlock_both;
- }
-
/*
* Default handling if a filesystem does not provide
* a migration function. We can only migrate clean
*/
if (!page_has_buffers(page) ||
try_to_release_page(page, GFP_KERNEL)) {
- rc = migrate_page(newpage, page);
+ rc = migrate_page(mapping, newpage, page);
goto unlock_both;
}
unlock_page(page);
next:
- if (rc == -EAGAIN) {
- retry++;
- } else if (rc) {
- /* Permanent failure */
- list_move(&page->lru, failed);
- nr_failed++;
+ if (rc) {
+ if (newpage)
+ newpage->mapping = NULL;
+
+ if (rc == -EAGAIN)
+ retry++;
+ else {
+ /* Permanent failure */
+ list_move(&page->lru, failed);
+ nr_failed++;
+ }
} else {
if (newpage) {
/* Successful migration. Return page to LRU */
projects / deliverable / linux.git / blobdiff