From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 28 Apr 2006 20:23:12 -0700 (PDT) From: Christoph Lameter Message-Id: <20060429032312.4999.78688.sendpatchset@schroedinger.engr.sgi.com> In-Reply-To: <20060429032246.4999.21714.sendpatchset@schroedinger.engr.sgi.com> References: <20060429032246.4999.21714.sendpatchset@schroedinger.engr.sgi.com> Subject: [PATCH 5/7] PM cleanup: Extract try_to_unmap from migration functions Sender: owner-linux-mm@kvack.org Return-Path: To: akpm@osdl.org Cc: linux-mm@kvack.org, Hugh Dickins , Lee Schermerhorn , Christoph Lameter , KAMEZAWA Hiroyuki List-ID: page migration: Extract try_to_unmap and rename remove_references -> move_mapping try_to_unmap may significantly change the page state by for example setting the dirty bit. It is therefore best to unmap in migrate_pages() before calling any migration functions. migrate_page_remove_references() will then only move the new page in place of the old page in the mapping. Rename the function to migrate_page_move_mapping(). This allows us to get rid of the special unmapping for the fallback path. Signed-off-by: Christoph Lameter Index: linux-2.6.17-rc3/mm/migrate.c =================================================================== --- linux-2.6.17-rc3.orig/mm/migrate.c 2006-04-28 17:31:10.325193799 -0700 +++ linux-2.6.17-rc3/mm/migrate.c 2006-04-28 17:42:24.342949272 -0700 @@ -166,15 +166,14 @@ } /* - * Remove references for a page and establish the new page with the correct - * basic settings to be able to stop accesses to the page. + * Remove or 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, +static int migrate_page_move_mapping(struct page *newpage, struct page *page) { struct address_space *mapping = page_mapping(page); @@ -183,35 +182,6 @@ if (!mapping) 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( @@ -310,7 +280,7 @@ BUG_ON(PageWriteback(page)); /* Writeback must be complete */ - rc = migrate_page_remove_references(newpage, page); + rc = migrate_page_move_mapping(newpage, page); if (rc) return rc; @@ -349,7 +319,7 @@ head = page_buffers(page); - rc = migrate_page_remove_references(newpage, page); + rc = migrate_page_move_mapping(newpage, page); if (rc) return rc; @@ -482,6 +452,33 @@ lock_page(newpage); /* + * 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_both; + + rc = -EAGAIN; + if (page_mapped(page)) + goto unlock_both; + /* * Pages are properly locked and writeback is complete. * Try to migrate the page. */ @@ -501,17 +498,6 @@ 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . 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