Commit 4983da07 authored by Christoph Lameter's avatar Christoph Lameter Committed by Linus Torvalds
Browse files

[PATCH] page migration: fail if page is in a vma flagged VM_LOCKED 



page migration currently simply retries a couple of times if try_to_unmap()
fails without inspecting the return code.

However, SWAP_FAIL indicates that the page is in a vma that has the
VM_LOCKED flag set (if ignore_refs ==1).  We can check for that return code
and avoid retrying the migration.

migrate_page_remove_references() now needs to return a reason why the
failure occured.  So switch migrate_page_remove_references to use -Exx
style error messages.

Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent e843e280

fs/buffer.c

+4 −2
Original line number Diff line number Diff line
@@ -3060,6 +3060,7 @@ int buffer_migrate_page(struct page *newpage, struct page *page) 
{

	struct address_space *mapping = page->mapping;

	struct buffer_head *bh, *head;

	int rc;



	if (!mapping)

		return -EAGAIN;
@@ -3069,8 +3070,9 @@ int buffer_migrate_page(struct page *newpage, struct page *page) 


	head = page_buffers(page);



	if (migrate_page_remove_references(newpage, page, 3))

		return -EAGAIN;

	rc = migrate_page_remove_references(newpage, page, 3);

	if (rc)

		return rc;



	bh = head;

	do {

mm/vmscan.c

+12 −6
Original line number Diff line number Diff line
@@ -700,7 +700,7 @@ int migrate_page_remove_references(struct page *newpage, 
	 * the page.

	 */

	if (!mapping || page_mapcount(page) + nr_refs != page_count(page))

		return 1;

		return -EAGAIN;



	/*

	 * Establish swap ptes for anonymous pages or destroy pte
@@ -721,13 +721,15 @@ int migrate_page_remove_references(struct page *newpage, 
	 * If the page was not migrated then the PageSwapCache bit

	 * is still set and the operation may continue.

	 */

	try_to_unmap(page, 1);

	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 1;

		return -EAGAIN;



	write_lock_irq(&mapping->tree_lock);
@@ -738,7 +740,7 @@ int migrate_page_remove_references(struct page *newpage, 
	if (!page_mapping(page) || page_count(page) != nr_refs ||

			*radix_pointer != page) {

		write_unlock_irq(&mapping->tree_lock);

		return 1;

		return -EAGAIN;

	}



	/*
@@ -813,10 +815,14 @@ EXPORT_SYMBOL(migrate_page_copy); 
 */

int migrate_page(struct page *newpage, struct page *page)

{

	int rc;



	BUG_ON(PageWriteback(page));	/* Writeback must be complete */



	if (migrate_page_remove_references(newpage, page, 2))

		return -EAGAIN;

	rc = migrate_page_remove_references(newpage, page, 2);



	if (rc)

		return rc;



	migrate_page_copy(newpage, page);

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