[PATCH] page migration: use allocator function for migrate_pages()

Instead of passing a list of new pages, pass a function to allocate a new
page.  This allows the correct placement of MPOL_INTERLEAVE pages during page
migration.  It also further simplifies the callers of migrate pages.
migrate_pages() becomes similar to migrate_pages_to() so drop
migrate_pages_to().  The batching of new page allocations becomes unnecessary.

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>

2 files changed, 53 insertions, 85 deletions

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 244f3f130e4a..f432642e9e66 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -87,6 +87,7 @@
 #include <linux/seq_file.h>
 #include <linux/proc_fs.h>
 #include <linux/migrate.h>
+#include <linux/rmap.h>
 
 #include <asm/tlbflush.h>
 #include <asm/uaccess.h>
@@ -587,6 +588,11 @@ static void migrate_page_add(struct page *page, struct list_head *pagelist,
                 isolate_lru_page(page, pagelist);
 }
 
+static struct page *new_node_page(struct page *page, unsigned long node)
+{
+        return alloc_pages_node(node, GFP_HIGHUSER, 0);
+}
+
 /*
  * Migrate pages from one node to a target node.
  * Returns error or the number of pages not migrated.
@@ -604,7 +610,8 @@ int migrate_to_node(struct mm_struct *mm, int source, int dest, int flags)
                         flags | MPOL_MF_DISCONTIG_OK, &pagelist);
 
         if (!list_empty(&pagelist))
-                err = migrate_pages_to(&pagelist, NULL, dest);
+                err = migrate_pages(&pagelist, new_node_page, dest);
+
         return err;
 }
 
@@ -691,6 +698,12 @@ int do_migrate_pages(struct mm_struct *mm,
 
 }
 
+static struct page *new_vma_page(struct page *page, unsigned long private)
+{
+        struct vm_area_struct *vma = (struct vm_area_struct *)private;
+
+        return alloc_page_vma(GFP_HIGHUSER, vma, page_address_in_vma(page, vma));
+}
 #else
 
 static void migrate_page_add(struct page *page, struct list_head *pagelist,
@@ -703,6 +716,11 @@ int do_migrate_pages(struct mm_struct *mm,
 {
         return -ENOSYS;
 }
+
+static struct page *new_vma_page(struct page *page, unsigned long private)
+{
+        return NULL;
+}
 #endif
 
 long do_mbind(unsigned long start, unsigned long len,
@@ -764,7 +782,8 @@ long do_mbind(unsigned long start, unsigned long len,
                 err = mbind_range(vma, start, end, new);
 
                 if (!list_empty(&pagelist))
-                        nr_failed = migrate_pages_to(&pagelist, vma, -1);
+                        nr_failed = migrate_pages(&pagelist, new_vma_page,
+                                                (unsigned long)vma);
 
                 if (!err && nr_failed && (flags & MPOL_MF_STRICT))
                         err = -EIO;
diff --git a/mm/migrate.c b/mm/migrate.c
index d3a1810a4c9f..251a8d158257 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -28,9 +28,6 @@
 
 #include "internal.h"
 
-/* The maximum number of pages to take off the LRU for migration */
-#define MIGRATE_CHUNK_SIZE 256
-
 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
 
 /*
@@ -587,18 +584,23 @@ static int move_to_new_page(struct page *newpage, struct page *page)
  * 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)
+static int unmap_and_move(new_page_t get_new_page, unsigned long private,
+                        struct page *page, int force)
 {
         int rc = 0;
+        struct page *newpage = get_new_page(page, private);
+
+        if (!newpage)
+                return -ENOMEM;
 
         if (page_count(page) == 1)
                 /* page was freed from under us. So we are done. */
-                goto ret;
+                goto move_newpage;
 
         rc = -EAGAIN;
         if (TestSetPageLocked(page)) {
                 if (!force)
-                        goto ret;
+                        goto move_newpage;
                 lock_page(page);
         }
 
@@ -622,7 +624,7 @@ static int unmap_and_move(struct page *newpage, struct page *page, int force)
                 remove_migration_ptes(page, page);
 unlock:
         unlock_page(page);
-ret:
+
         if (rc != -EAGAIN) {
                 /*
                  * A page that has been migrated has all references
@@ -632,29 +634,33 @@ ret:
                  */
                 list_del(&page->lru);
                 move_to_lru(page);
-
-                list_del(&newpage->lru);
-                move_to_lru(newpage);
         }
+
+move_newpage:
+        /*
+         * Move the new page to the LRU. If migration was not successful
+         * then this will free the page.
+         */
+        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 isolated pages
- * can be moved to.
+ * The function takes one list of pages to migrate and a function
+ * that determines from the page to be migrated and the private data
+ * the target of the move and allocates the page.
  *
  * The function returns after 10 attempts or if no pages
  * are movable anymore because to has become empty
  * or no retryable pages exist anymore. All pages will be
  * retruned to the LRU or freed.
  *
- * Return: Number of pages not migrated.
+ * Return: Number of pages not migrated or error code.
  */
-int migrate_pages(struct list_head *from, struct list_head *to)
+int migrate_pages(struct list_head *from,
+                new_page_t get_new_page, unsigned long private)
 {
         int retry = 1;
         int nr_failed = 0;
@@ -671,15 +677,14 @@ int migrate_pages(struct list_head *from, struct list_head *to)
                 retry = 0;
 
                 list_for_each_entry_safe(page, page2, from, lru) {
-
-                        if (list_empty(to))
-                                break;
-
                         cond_resched();
 
-                        rc = unmap_and_move(lru_to_page(to), page, pass > 2);
+                        rc = unmap_and_move(get_new_page, private,
+                                                page, pass > 2);
 
                         switch(rc) {
+                        case -ENOMEM:
+                                goto out;
                         case -EAGAIN:
                                 retry++;
                                 break;
@@ -692,72 +697,16 @@ int migrate_pages(struct list_head *from, struct list_head *to)
                         }
                 }
         }
-
+        rc = 0;
+out:
         if (!swapwrite)
                 current->flags &= ~PF_SWAPWRITE;
 
         putback_lru_pages(from);
-        return nr_failed + retry;
-}
 
-/*
- * Migrate the list 'pagelist' of pages to a certain destination.
- *
- * Specify destination with either non-NULL vma or dest_node >= 0
- * Return the number of pages not migrated or error code
- */
-int migrate_pages_to(struct list_head *pagelist,
-                        struct vm_area_struct *vma, int dest)
-{
-        LIST_HEAD(newlist);
-        int err = 0;
-        unsigned long offset = 0;
-        int nr_pages;
-        int nr_failed = 0;
-        struct page *page;
-        struct list_head *p;
-
-redo:
-        nr_pages = 0;
-        list_for_each(p, pagelist) {
-                if (vma) {
-                        /*
-                         * The address passed to alloc_page_vma is used to
-                         * generate the proper interleave behavior. We fake
-                         * the address here by an increasing offset in order
-                         * to get the proper distribution of pages.
-                         *
-                         * No decision has been made as to which page
-                         * a certain old page is moved to so we cannot
-                         * specify the correct address.
-                         */
-                        page = alloc_page_vma(GFP_HIGHUSER, vma,
-                                        offset + vma->vm_start);
-                        offset += PAGE_SIZE;
-                }
-                else
-                        page = alloc_pages_node(dest, GFP_HIGHUSER, 0);
-
-                if (!page) {
-                        err = -ENOMEM;
-                        goto out;
-                }
-                list_add_tail(&page->lru, &newlist);
-                nr_pages++;
-                if (nr_pages > MIGRATE_CHUNK_SIZE)
-                        break;
-        }
-        err = migrate_pages(pagelist, &newlist);
-
-        if (err >= 0) {
-                nr_failed += err;
-                if (list_empty(&newlist) && !list_empty(pagelist))
-                        goto redo;
-        }
-out:
+        if (rc)
+                return rc;
 
-        /* Calculate number of leftover pages */
-        list_for_each(p, pagelist)
-                nr_failed++;
-        return nr_failed;
+        return nr_failed + retry;
 }
+