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Commit 5b5c7120 authored by Christoph Lameter's avatar Christoph Lameter Committed by Linus Torvalds
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[PATCH] page migration cleanup: drop nr_refs in remove_references() 



Drop nr_refs parameter from migrate_page_remove_references()

The nr_refs parameter is not really useful since the number of remaining
references is always

1 for anonymous pages without a mapping
2 for pages with a mapping
3 for pages with a mapping and PagePrivate set.

Remove the early check for the number of references since we are checking
page_mapcount() earlier.  Ultimately only the refcount matters after the
tree_lock has been obtained.

Signed-off-by: default avatarChristoph Lameter <clameter@sgi.coim>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent e7340f73

mm/migrate.c

+11 −10
Original line number Diff line number Diff line
@@ -168,19 +168,19 @@ static int swap_page(struct page *page) 
/*

 * Remove references for a page and establish the new page with the correct

 * basic settings to be able to stop accesses to the page.

 *

 * 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)

				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))

	if (!mapping)

		return -EAGAIN;



	/*
@@ -218,7 +218,8 @@ static int migrate_page_remove_references(struct page *newpage, 
						&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;
@@ -309,7 +310,7 @@ int migrate_page(struct page *newpage, struct page *page) 


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



	rc = migrate_page_remove_references(newpage, page, 2);

	rc = migrate_page_remove_references(newpage, page);



	if (rc)

		return rc;
@@ -348,7 +349,7 @@ int buffer_migrate_page(struct page *newpage, struct page *page) 


	head = page_buffers(page);



	rc = migrate_page_remove_references(newpage, page, 3);

	rc = migrate_page_remove_references(newpage, page);



	if (rc)

		return rc;