Commit d0d96328 authored Jan 08, 2006 by Christoph Lameter Committed by Linus Torvalds Jan 08, 2006

[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>

parent d4984711

mm/vmscan.c

+34 −22

Original line number	Diff line number	Diff line
		@@ -606,10 +606,6 @@ int putback_lru_pages(struct list_head *l)
		/*
		* 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 @@ static int swap_page(struct page *page)
		unlock_page(page);

		retry:
		return 1;
		return -EAGAIN;
		}
		/*
		* migrate_pages
		@@ -669,6 +665,8 @@ static int swap_page(struct page *page)
		* 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 @@ int migrate_pages(struct list_head from, struct list_head to,
		struct page *page;
		struct page *page2;
		int swapwrite = current->flags & PF_SWAPWRITE;
		int rc;

		if (!swapwrite)
		current->flags \|= PF_SWAPWRITE;
		@@ -689,22 +688,23 @@ int migrate_pages(struct list_head from, struct list_head to,
		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 @@ int migrate_pages(struct list_head from, struct list_head to,
		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 @@ int migrate_pages(struct list_head from, struct list_head to,
		* 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;