X-Git-Url: https://git.kernelconcepts.de/?a=blobdiff_plain;f=mm%2Fmigrate.c;h=ca71d064bce7c8295362db6127ce22bf3c83d5e0;hb=a67f6f3794586c33e430d8a8e61d0548d33a3abe;hp=d3f3f7f81075eb1eb2e7f5dbe2c0f292a489dacf;hpb=274a24c16fa97a1fc67437b191274db2286c7ac3;p=karo-tx-linux.git

diff --git a/mm/migrate.c b/mm/migrate.c
index d3f3f7f81075..ca71d064bce7 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -40,7 +40,8 @@
 
 /*
  * migrate_prep() needs to be called before we start compiling a list of pages
- * to be migrated using isolate_lru_page().
+ * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
+ * undesirable, use migrate_prep_local()
  */
 int migrate_prep(void)
 {
@@ -55,26 +56,29 @@ int migrate_prep(void)
 	return 0;
 }
 
+/* Do the necessary work of migrate_prep but not if it involves other CPUs */
+int migrate_prep_local(void)
+{
+	lru_add_drain();
+
+	return 0;
+}
+
 /*
  * Add isolated pages on the list back to the LRU under page lock
  * to avoid leaking evictable pages back onto unevictable list.
- *
- * returns the number of pages put back.
  */
-int putback_lru_pages(struct list_head *l)
+void putback_lru_pages(struct list_head *l)
 {
 	struct page *page;
 	struct page *page2;
-	int count = 0;
 
 	list_for_each_entry_safe(page, page2, l, lru) {
 		list_del(&page->lru);
 		dec_zone_page_state(page, NR_ISOLATED_ANON +
 				page_is_file_cache(page));
 		putback_lru_page(page);
-		count++;
 	}
-	return count;
 }
 
 /*
@@ -262,7 +266,7 @@ static int migrate_page_move_mapping(struct address_space *mapping,
 	 */
 	__dec_zone_page_state(page, NR_FILE_PAGES);
 	__inc_zone_page_state(newpage, NR_FILE_PAGES);
-	if (PageSwapBacked(page)) {
+	if (!PageSwapCache(page) && PageSwapBacked(page)) {
 		__dec_zone_page_state(page, NR_SHMEM);
 		__inc_zone_page_state(newpage, NR_SHMEM);
 	}
@@ -490,7 +494,8 @@ static int fallback_migrate_page(struct address_space *mapping,
  *   < 0 - error code
  *  == 0 - success
  */
-static int move_to_new_page(struct page *newpage, struct page *page)
+static int move_to_new_page(struct page *newpage, struct page *page,
+						int remap_swapcache)
 {
 	struct address_space *mapping;
 	int rc;
@@ -525,10 +530,12 @@ static int move_to_new_page(struct page *newpage, struct page *page)
 	else
 		rc = fallback_migrate_page(mapping, newpage, page);
 
-	if (!rc)
-		remove_migration_ptes(page, newpage);
-	else
+	if (rc) {
 		newpage->mapping = NULL;
+	} else {
+		if (remap_swapcache)
+			remove_migration_ptes(page, newpage);
+	}
 
 	unlock_page(newpage);
 
@@ -545,9 +552,11 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
 	int rc = 0;
 	int *result = NULL;
 	struct page *newpage = get_new_page(page, private, &result);
+	int remap_swapcache = 1;
 	int rcu_locked = 0;
 	int charge = 0;
 	struct mem_cgroup *mem = NULL;
+	struct anon_vma *anon_vma = NULL;
 
 	if (!newpage)
 		return -ENOMEM;
@@ -581,7 +590,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
 	}
 
 	/* charge against new page */
-	charge = mem_cgroup_prepare_migration(page, &mem);
+	charge = mem_cgroup_prepare_migration(page, newpage, &mem);
 	if (charge == -ENOMEM) {
 		rc = -ENOMEM;
 		goto unlock;
@@ -604,6 +613,34 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
 	if (PageAnon(page)) {
 		rcu_read_lock();
 		rcu_locked = 1;
+
+		/* Determine how to safely use anon_vma */
+		if (!page_mapped(page)) {
+			if (!PageSwapCache(page))
+				goto rcu_unlock;
+
+			/*
+			 * We cannot be sure that the anon_vma of an unmapped
+			 * swapcache page is safe to use because we don't
+			 * know in advance if the VMA that this page belonged
+			 * to still exists. If the VMA and others sharing the
+			 * data have been freed, then the anon_vma could
+			 * already be invalid.
+			 *
+			 * To avoid this possibility, swapcache pages get
+			 * migrated but are not remapped when migration
+			 * completes
+			 */
+			remap_swapcache = 0;
+		} else {
+			/*
+			 * Take a reference count on the anon_vma if the
+			 * page is mapped so that it is guaranteed to
+			 * exist when the page is remapped later
+			 */
+			anon_vma = page_anon_vma(page);
+			atomic_inc(&anon_vma->external_refcount);
+		}
 	}
 
 	/*
@@ -638,11 +675,20 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
 
 skip_unmap:
 	if (!page_mapped(page))
-		rc = move_to_new_page(newpage, page);
+		rc = move_to_new_page(newpage, page, remap_swapcache);
 
-	if (rc)
+	if (rc && remap_swapcache)
 		remove_migration_ptes(page, page);
 rcu_unlock:
+
+	/* Drop an anon_vma reference if we took one */
+	if (anon_vma && atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->lock)) {
+		int empty = list_empty(&anon_vma->head);
+		spin_unlock(&anon_vma->lock);
+		if (empty)
+			anon_vma_free(anon_vma);
+	}
+
 	if (rcu_locked)
 		rcu_read_unlock();
 uncharge: