The patch titled
page migration: simplify migrate_pages()
has been added to the -mm tree. Its filename is
page-migration-simplify-migrate_pages.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: page migration: simplify migrate_pages()
From: Christoph Lameter <clameter@xxxxxxx>
Currently migrate_pages() is mess with lots of goto. Extract two functions
from migrate_pages() and get rid of the gotos.
Plus we can just unconditionally set the locked bit on the new page since we
are the only one holding a reference. Locking is to stop others from
accessing the page once we establish references to the new page.
Remove the list_del from move_to_lru in order to have finer control over list
processing.
Signed-off-by: Christoph Lameter <clameter@xxxxxxx>
Cc: Hugh Dickins <hugh@xxxxxxxxxxx>
Cc: Jes Sorensen <jes@xxxxxxxxxxxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Lee Schermerhorn <lee.schermerhorn@xxxxxx>
Cc: Andi Kleen <ak@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
mm/migrate.c | 218 +++++++++++++++++++++++++------------------------
1 files changed, 115 insertions(+), 103 deletions(-)
diff -puN mm/migrate.c~page-migration-simplify-migrate_pages mm/migrate.c
--- 25/mm/migrate.c~page-migration-simplify-migrate_pages Fri May 19 12:28:08 2006
+++ 25-akpm/mm/migrate.c Fri May 19 12:28:08 2006
@@ -84,7 +84,6 @@ int migrate_prep(void)
static inline void move_to_lru(struct page *page)
{
- list_del(&page->lru);
if (PageActive(page)) {
/*
* lru_cache_add_active checks that
@@ -110,6 +109,7 @@ int putback_lru_pages(struct list_head *
int count = 0;
list_for_each_entry_safe(page, page2, l, lru) {
+ list_del(&page->lru);
move_to_lru(page);
count++;
}
@@ -534,11 +534,108 @@ static int fallback_migrate_page(struct
}
/*
+ * Move a page to a newly allocated page
+ * The page is locked and all ptes have been successfully removed.
+ *
+ * The new page will have replaced the old page if this function
+ * is successful.
+ */
+static int move_to_new_page(struct page *newpage, struct page *page)
+{
+ struct address_space *mapping;
+ int rc;
+
+ /*
+ * Block others from accessing the page when we get around to
+ * establishing additional references. We are the only one
+ * holding a reference to the new page at this point.
+ */
+ SetPageLocked(newpage);
+
+ /* Prepare mapping for the new page.*/
+ newpage->index = page->index;
+ newpage->mapping = page->mapping;
+
+ mapping = page_mapping(page);
+ if (!mapping)
+ rc = migrate_page(mapping, newpage, page);
+
+ else if (mapping->a_ops->migratepage)
+ /*
+ * Most pages have a mapping and most filesystems
+ * should provide a migration function. Anonymous
+ * pages are part of swap space which also has its
+ * own migration function. This is the most common
+ * path for page migration.
+ */
+ rc = mapping->a_ops->migratepage(mapping,
+ newpage, page);
+ else
+ rc = fallback_migrate_page(mapping, newpage, page);
+
+ if (!rc)
+ remove_migration_ptes(page, newpage);
+ else
+ newpage->mapping = NULL;
+
+ unlock_page(newpage);
+
+ return rc;
+}
+
+/*
+ * Obtain the lock on page, remove all ptes and migrate the page
+ * to the newly allocated page in newpage.
+ */
+static int unmap_and_move(struct page *newpage, struct page *page, int force)
+{
+ int rc = 0;
+
+ if (page_count(page) == 1)
+ /* page was freed from under us. So we are done. */
+ goto ret;
+
+ rc = -EAGAIN;
+ if (TestSetPageLocked(page)) {
+ if (!force)
+ goto ret;
+ lock_page(page);
+ }
+
+ if (PageWriteback(page)) {
+ if (!force)
+ goto unlock;
+ wait_on_page_writeback(page);
+ }
+
+ /*
+ * Establish migration ptes or remove ptes
+ */
+ if (try_to_unmap(page, 1) != SWAP_FAIL) {
+ if (!page_mapped(page))
+ rc = move_to_new_page(newpage, page);
+ } else
+ /* A vma has VM_LOCKED set -> permanent failure */
+ rc = -EPERM;
+
+ if (rc)
+ remove_migration_ptes(page, page);
+unlock:
+ unlock_page(page);
+ret:
+ if (rc != -EAGAIN) {
+ list_del(&newpage->lru);
+ move_to_lru(newpage);
+ }
+ return rc;
+}
+
+/*
* migrate_pages
*
* Two lists are passed to this function. The first list
* contains the pages isolated from the LRU to be migrated.
- * The second list contains new pages that the pages isolated
+ * The second list contains new pages that the isolated pages
* can be moved to.
*
* The function returns after 10 attempts or if no pages
@@ -550,7 +647,7 @@ static int fallback_migrate_page(struct
int migrate_pages(struct list_head *from, struct list_head *to,
struct list_head *moved, struct list_head *failed)
{
- int retry;
+ int retry = 1;
int nr_failed = 0;
int pass = 0;
struct page *page;
@@ -561,118 +658,33 @@ int migrate_pages(struct list_head *from
if (!swapwrite)
current->flags |= PF_SWAPWRITE;
-redo:
- retry = 0;
+ for(pass = 0; pass < 10 && retry; pass++) {
+ retry = 0;
- list_for_each_entry_safe(page, page2, from, lru) {
- struct page *newpage = NULL;
- struct address_space *mapping;
-
- cond_resched();
-
- rc = 0;
- if (page_count(page) == 1)
- /* page was freed from under us. So we are done. */
- goto next;
+ list_for_each_entry_safe(page, page2, from, lru) {
- if (to && list_empty(to))
- break;
+ if (list_empty(to))
+ break;
- /*
- * 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 next;
-
- /*
- * Only wait on writeback if we have already done a pass where
- * we we may have triggered writeouts for lots of pages.
- */
- if (pass > 0)
- wait_on_page_writeback(page);
- else
- if (PageWriteback(page))
- goto unlock_page;
-
- /*
- * Establish migration ptes or remove ptes
- */
- rc = -EPERM;
- if (try_to_unmap(page, 1) == SWAP_FAIL)
- /* A vma has VM_LOCKED set -> permanent failure */
- goto unlock_page;
-
- rc = -EAGAIN;
- if (page_mapped(page))
- goto unlock_page;
-
- newpage = lru_to_page(to);
- lock_page(newpage);
- /* Prepare mapping for the new page.*/
- newpage->index = page->index;
- newpage->mapping = page->mapping;
+ cond_resched();
- /*
- * Pages are properly locked and writeback is complete.
- * Try to migrate the page.
- */
- mapping = page_mapping(page);
- if (!mapping)
- rc = migrate_page(mapping, newpage, page);
-
- else if (mapping->a_ops->migratepage)
- /*
- * Most pages have a mapping and most filesystems
- * should provide a migration function. Anonymous
- * pages are part of swap space which also has its
- * own migration function. This is the most common
- * path for page migration.
- */
- rc = mapping->a_ops->migratepage(mapping,
- newpage, page);
- else
- rc = fallback_migrate_page(mapping, newpage, page);
-
- if (!rc)
- remove_migration_ptes(page, newpage);
-
- unlock_page(newpage);
-
-unlock_page:
- if (rc)
- remove_migration_ptes(page, page);
-
- unlock_page(page);
-
-next:
- if (rc) {
- if (newpage)
- newpage->mapping = NULL;
+ rc = unmap_and_move(lru_to_page(to), page, pass > 2);
- if (rc == -EAGAIN)
+ switch(rc) {
+ case -EAGAIN:
retry++;
- else {
+ break;
+ case 0:
+ list_move(&page->lru, moved);
+ break;
+ default:
/* Permanent failure */
list_move(&page->lru, failed);
nr_failed++;
+ break;
}
- } else {
- if (newpage) {
- /* Successful migration. Return page to LRU */
- move_to_lru(newpage);
- }
- list_move(&page->lru, moved);
}
}
- if (retry && pass++ < 10)
- goto redo;
if (!swapwrite)
current->flags &= ~PF_SWAPWRITE;
_
Patches currently in -mm which might be from clameter@xxxxxxx are
origin.patch
page-migration-make-do_swap_page-redo-the-fault.patch
slab-extract-cache_free_alien-from-__cache_free.patch
migration-remove-unnecessary-pageswapcache-checks.patch
page-migration-cleanup-rename-ignrefs-to-migration.patch
page-migration-cleanup-group-functions.patch
page-migration-cleanup-remove-useless-definitions.patch
page-migration-cleanup-drop-nr_refs-in-remove_references.patch
page-migration-cleanup-extract-try_to_unmap-from-migration-functions.patch
page-migration-cleanup-extract-try_to_unmap-from-migration-functions-update-comments-7.patch
page-migration-cleanup-pass-mapping-to-migration-functions.patch
page-migration-cleanup-move-fallback-handling-into-special-function.patch
page-migration-cleanup-move-fallback-handling-into-special-function-update-comments-9.patch
swapless-pm-add-r-w-migration-entries.patch
swapless-pm-add-r-w-migration-entries-ifdefs.patch
swapless-pm-add-r-w-migration-entries-update-comments.patch
swapless-pm-add-r-w-migration-entries-update-comments-4.patch
swapless-pm-add-r-w-migration-entries-update-comments-6.patch
swapless-page-migration-rip-out-swap-based-logic.patch
swapless-page-migration-modify-core-logic.patch
swapless-page-migration-modify-core-logic-remove-useless-mapping-checks.patch
more-page-migration-do-not-inc-dec-rss-counters.patch
more-page-migration-use-migration-entries-for-file-pages.patch
more-page-migration-use-migration-entries-for-file-pages-fix.patch
more-page-migration-use-migration-entries-for-file-pages-update-comments-5.patch
more-page-migration-use-migration-entries-for-file-pages-update-comments-8.patch
more-page-migration-use-migration-entries-for-file-pages-remove_migration_ptes.patch
more-page-migration-use-migration-entries-for-file-pages-replace-call-to-pageout-with-writepage-2.patch
page-migration-update-documentation.patch
page-migration-simplify-migrate_pages.patch
page-migration-simplify-migrate_pages-tweaks.patch
page-migration-handle-freeing-of-pages-in-migrate_pages.patch
page-migration-use-allocator-function-for-migrate_pages.patch
page-migration-support-moving-of-individual-pages.patch
page-migration-detailed-status-for-moving-of-individual-pages.patch
page-migration-support-a-vma-migration-function.patch
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