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authorChristoph Lameter <clameter@sgi.com>2006-06-23 02:03:37 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-06-23 07:42:50 -0700
commit6c5240ae7f48c83fcaa8e24fa63e7eb09aba5651 (patch)
treefede2324f4348701e60758d7f894aae4b09cdc9a
parentd75a0fcda2cfc71b50e16dc89e0c32c57d427e85 (diff)
[PATCH] Swapless page migration: modify core logic
Use the migration entries for page migration This modifies the migration code to use the new migration entries. It now becomes possible to migrate anonymous pages without having to add a swap entry. We add a couple of new functions to replace migration entries with the proper ptes. We cannot take the tree_lock for migrating anonymous pages anymore. However, we know that we hold the only remaining reference to the page when the page count reaches 1. Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--mm/Kconfig4
-rw-r--r--mm/migrate.c53
2 files changed, 23 insertions, 34 deletions
diff --git a/mm/Kconfig b/mm/Kconfig
index 332f5c29b53..66e65ab3942 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -138,8 +138,8 @@ config SPLIT_PTLOCK_CPUS
#
config MIGRATION
bool "Page migration"
- def_bool y if NUMA
- depends on SWAP && NUMA
+ def_bool y
+ depends on NUMA
help
Allows the migration of the physical location of pages of processes
while the virtual addresses are not changed. This is useful for
diff --git a/mm/migrate.c b/mm/migrate.c
index 81721a061d5..8f91463eab4 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -254,14 +254,20 @@ static int migrate_page_move_mapping(struct address_space *mapping,
{
struct page **radix_pointer;
+ if (!mapping) {
+ /* Anonymous page */
+ if (page_count(page) != 1)
+ return -EAGAIN;
+ return 0;
+ }
+
write_lock_irq(&mapping->tree_lock);
radix_pointer = (struct page **)radix_tree_lookup_slot(
&mapping->page_tree,
page_index(page));
- if (!page_mapping(page) ||
- page_count(page) != 2 + !!PagePrivate(page) ||
+ if (page_count(page) != 2 + !!PagePrivate(page) ||
*radix_pointer != page) {
write_unlock_irq(&mapping->tree_lock);
return -EAGAIN;
@@ -271,10 +277,12 @@ static int migrate_page_move_mapping(struct address_space *mapping,
* Now we know that no one else is looking at the page.
*/
get_page(newpage);
+#ifdef CONFIG_SWAP
if (PageSwapCache(page)) {
SetPageSwapCache(newpage);
set_page_private(newpage, page_private(page));
}
+#endif
*radix_pointer = newpage;
__put_page(page);
@@ -308,7 +316,9 @@ static void migrate_page_copy(struct page *newpage, struct page *page)
set_page_dirty(newpage);
}
+#ifdef CONFIG_SWAP
ClearPageSwapCache(page);
+#endif
ClearPageActive(page);
ClearPagePrivate(page);
set_page_private(page, 0);
@@ -353,16 +363,6 @@ int migrate_page(struct address_space *mapping,
return rc;
migrate_page_copy(newpage, page);
-
- /*
- * Remove auxiliary swap entries and replace
- * them with real ptes.
- *
- * Note that a real pte entry will allow processes that are not
- * waiting on the page lock to use the new page via the page tables
- * before the new page is unlocked.
- */
- remove_from_swap(newpage);
return 0;
}
EXPORT_SYMBOL(migrate_page);
@@ -530,23 +530,7 @@ redo:
goto unlock_page;
/*
- * 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.
+ * Establish migration ptes or remove ptes
*/
rc = -EPERM;
if (try_to_unmap(page, 1) == SWAP_FAIL)
@@ -569,9 +553,9 @@ redo:
*/
mapping = page_mapping(page);
if (!mapping)
- goto unlock_both;
+ rc = migrate_page(mapping, newpage, page);
- if (mapping->a_ops->migratepage)
+ else if (mapping->a_ops->migratepage)
/*
* Most pages have a mapping and most filesystems
* should provide a migration function. Anonymous
@@ -584,10 +568,15 @@ redo:
else
rc = fallback_migrate_page(mapping, newpage, page);
-unlock_both:
+ if (!rc)
+ remove_migration_ptes(page, newpage);
+
unlock_page(newpage);
unlock_page:
+ if (rc)
+ remove_migration_ptes(page, page);
+
unlock_page(page);
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