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Commit 8351a6e4 authored by Christoph Lameter's avatar Christoph Lameter Committed by Linus Torvalds
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[PATCH] page migration cleanup: move fallback handling into special function 



Move the fallback code into a new fallback function and make the function
behave like any other migration function.  This requires retaking the lock if
pageout() drops it.

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 2d1db3b1

mm/migrate.c

+39 −51
Original line number Diff line number Diff line
@@ -349,6 +349,42 @@ int buffer_migrate_page(struct address_space *mapping, 
}

EXPORT_SYMBOL(buffer_migrate_page);



static int fallback_migrate_page(struct address_space *mapping,

	struct page *newpage, struct page *page)

{

	/*

	 * Default handling if a filesystem does not provide

	 * a migration function. We can only migrate clean

	 * pages so try to write out any dirty pages first.

	 */

	if (PageDirty(page)) {

		switch (pageout(page, mapping)) {

		case PAGE_KEEP:

		case PAGE_ACTIVATE:

			return -EAGAIN;



		case PAGE_SUCCESS:

			/* Relock since we lost the lock */

			lock_page(page);

			/* Must retry since page state may have changed */

			return -EAGAIN;



		case PAGE_CLEAN:

			; /* try to migrate the page below */

		}

	}



	/*

	 * Buffers may be managed in a filesystem specific way.

	 * We must have no buffers or drop them.

	 */

	if (page_has_buffers(page) &&

	    !try_to_release_page(page, GFP_KERNEL))

		return -EAGAIN;



	return migrate_page(mapping, newpage, page);

}



/*

 * migrate_pages

 *
@@ -478,7 +514,7 @@ int migrate_pages(struct list_head *from, struct list_head *to, 
		if (!mapping)

			goto unlock_both;



		if (mapping->a_ops->migratepage) {

		if (mapping->a_ops->migratepage)

			/*

			 * Most pages have a mapping and most filesystems

			 * should provide a migration function. Anonymous
@@ -488,56 +524,8 @@ int migrate_pages(struct list_head *from, struct list_head *to, 
			 */

			rc = mapping->a_ops->migratepage(mapping,

							newpage, page);

			goto unlock_both;

                }



		/*

		 * Default handling if a filesystem does not provide

		 * a migration function. We can only migrate clean

		 * pages so try to write out any dirty pages first.

		 */

		if (PageDirty(page)) {

			switch (pageout(page, mapping)) {

			case PAGE_KEEP:

			case PAGE_ACTIVATE:

				goto unlock_both;



			case PAGE_SUCCESS:

				unlock_page(newpage);

				goto next;



			case PAGE_CLEAN:

				; /* try to migrate the page below */

			}

                }



		/*

		 * Buffers are managed in a filesystem specific way.

		 * We must have no buffers or drop them.

		 */

		if (!page_has_buffers(page) ||

		    try_to_release_page(page, GFP_KERNEL)) {

			rc = migrate_page(mapping, newpage, page);

			goto unlock_both;

		}



		/*

		 * On early passes with mapped pages simply

		 * retry. There may be a lock held for some

		 * buffers that may go away. Later

		 * swap them out.

		 */

		if (pass > 4) {

			/*

			 * Persistently unable to drop buffers..... As a

			 * measure of last resort we fall back to

			 * swap_page().

			 */

			unlock_page(newpage);

			newpage = NULL;

			rc = swap_page(page);

			goto next;

		}

		else

			rc = fallback_migrate_page(mapping, newpage, page);



unlock_both:

		unlock_page(newpage);