[PATCH] page migration: handle freeing of pages in migrate_pages()

Do not leave pages on the lists passed to migrate_pages().  Seems that we will
not need any postprocessing of pages.  This will simplify the handling of
pages by the callers of migrate_pages().

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Jes Sorensen <jes@trained-monkey.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 27 insertions, 36 deletions

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 287c47b5e5df..83af25949fa9 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -8,8 +8,7 @@ extern int isolate_lru_page(struct page *p, struct list_head *pagelist);
 extern int putback_lru_pages(struct list_head *l);
 extern int migrate_page(struct address_space *,
                         struct page *, struct page *);
-extern int migrate_pages(struct list_head *l, struct list_head *t,
-                struct list_head *moved, struct list_head *failed);
+extern int migrate_pages(struct list_head *l, struct list_head *t);
 extern int migrate_pages_to(struct list_head *pagelist,
                         struct vm_area_struct *vma, int dest);
 extern int fail_migrate_page(struct address_space *,
@@ -22,8 +21,8 @@ extern int migrate_prep(void);
 static inline int isolate_lru_page(struct page *p, struct list_head *list)
                                         { return -ENOSYS; }
 static inline int putback_lru_pages(struct list_head *l) { return 0; }
-static inline int migrate_pages(struct list_head *l, struct list_head *t,
-        struct list_head *moved, struct list_head *failed) { return -ENOSYS; }
+static inline int migrate_pages(struct list_head *l, struct list_head *t)
+                                        { return -ENOSYS; }
 
 static inline int migrate_pages_to(struct list_head *pagelist,
                         struct vm_area_struct *vma, int dest) { return 0; }
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 8778f58880c4..244f3f130e4a 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -603,11 +603,8 @@ int migrate_to_node(struct mm_struct *mm, int source, int dest, int flags)
         check_range(mm, mm->mmap->vm_start, TASK_SIZE, &nmask,
                         flags | MPOL_MF_DISCONTIG_OK, &pagelist);
 
-        if (!list_empty(&pagelist)) {
+        if (!list_empty(&pagelist))
                 err = migrate_pages_to(&pagelist, NULL, dest);
-                if (!list_empty(&pagelist))
-                        putback_lru_pages(&pagelist);
-        }
         return err;
 }
 
@@ -773,9 +770,6 @@ long do_mbind(unsigned long start, unsigned long len,
                         err = -EIO;
         }
 
-        if (!list_empty(&pagelist))
-                putback_lru_pages(&pagelist);
-
         up_write(&mm->mmap_sem);
         mpol_free(new);
         return err;
diff --git a/mm/migrate.c b/mm/migrate.c
index 09038163bfec..d3a1810a4c9f 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -624,6 +624,15 @@ unlock:
         unlock_page(page);
 ret:
         if (rc != -EAGAIN) {
+                /*
+                 * A page that has been migrated has all references
+                 * removed and will be freed. A page that has not been
+                 * migrated will have kepts its references and be
+                 * restored.
+                 */
+                list_del(&page->lru);
+                move_to_lru(page);
+
                 list_del(&newpage->lru);
                 move_to_lru(newpage);
         }
@@ -640,12 +649,12 @@ ret:
  *
  * The function returns after 10 attempts or if no pages
  * are movable anymore because to has become empty
- * or no retryable pages exist anymore.
+ * or no retryable pages exist anymore. All pages will be
+ * retruned to the LRU or freed.
  *
- * Return: Number of pages not migrated when "to" ran empty.
+ * Return: Number of pages not migrated.
  */
-int migrate_pages(struct list_head *from, struct list_head *to,
-                  struct list_head *moved, struct list_head *failed)
+int migrate_pages(struct list_head *from, struct list_head *to)
 {
         int retry = 1;
         int nr_failed = 0;
@@ -675,11 +684,9 @@ int migrate_pages(struct list_head *from, struct list_head *to,
                                 retry++;
                                 break;
                         case 0:
-                                list_move(&page->lru, moved);
                                 break;
                         default:
                                 /* Permanent failure */
-                                list_move(&page->lru, failed);
                                 nr_failed++;
                                 break;
                         }
@@ -689,6 +696,7 @@ int migrate_pages(struct list_head *from, struct list_head *to,
         if (!swapwrite)
                 current->flags &= ~PF_SWAPWRITE;
 
+        putback_lru_pages(from);
         return nr_failed + retry;
 }
 
@@ -702,11 +710,10 @@ int migrate_pages_to(struct list_head *pagelist,
                         struct vm_area_struct *vma, int dest)
 {
         LIST_HEAD(newlist);
-        LIST_HEAD(moved);
-        LIST_HEAD(failed);
         int err = 0;
         unsigned long offset = 0;
         int nr_pages;
+        int nr_failed = 0;
         struct page *page;
         struct list_head *p;
 
@@ -740,26 +747,17 @@ redo:
                 if (nr_pages > MIGRATE_CHUNK_SIZE)
                         break;
         }
-        err = migrate_pages(pagelist, &newlist, &moved, &failed);
+        err = migrate_pages(pagelist, &newlist);
 
-        putback_lru_pages(&moved);      /* Call release pages instead ?? */
-
-        if (err >= 0 && list_empty(&newlist) && !list_empty(pagelist))
-                goto redo;
-out:
-        /* Return leftover allocated pages */
-        while (!list_empty(&newlist)) {
-                page = list_entry(newlist.next, struct page, lru);
-                list_del(&page->lru);
-                __free_page(page);
+        if (err >= 0) {
+                nr_failed += err;
+                if (list_empty(&newlist) && !list_empty(pagelist))
+                        goto redo;
         }
-        list_splice(&failed, pagelist);
-        if (err < 0)
-                return err;
+out:
 
         /* Calculate number of leftover pages */
-        nr_pages = 0;
         list_for_each(p, pagelist)
-                nr_pages++;
-        return nr_pages;
+                nr_failed++;
+        return nr_failed;
 }