mm: migration: clean up unmap_and_move()

unmap_and_move() is one a big messy function.  Clean it up.

Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 40 insertions, 35 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index 14d0a6a632f6..33358f878111 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -621,38 +621,18 @@ static int move_to_new_page(struct page *newpage, struct page *page,
         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(new_page_t get_new_page, unsigned long private,
-                        struct page *page, int force, bool offlining, bool sync)
+static int __unmap_and_move(struct page *page, struct page *newpage,
+                                int force, bool offlining, bool sync)
 {
-        int rc = 0;
-        int *result = NULL;
-        struct page *newpage = get_new_page(page, private, &result);
+        int rc = -EAGAIN;
         int remap_swapcache = 1;
         int charge = 0;
         struct mem_cgroup *mem;
         struct anon_vma *anon_vma = NULL;
 
-        if (!newpage)
-                return -ENOMEM;
-
-        if (page_count(page) == 1) {
-                /* page was freed from under us. So we are done. */
-                goto move_newpage;
-        }
-        if (unlikely(PageTransHuge(page)))
-                if (unlikely(split_huge_page(page)))
-                        goto move_newpage;
-
-        /* prepare cgroup just returns 0 or -ENOMEM */
-        rc = -EAGAIN;
-
         if (!trylock_page(page)) {
                 if (!force || !sync)
-                        goto move_newpage;
+                        goto out;
 
                 /*
                  * It's not safe for direct compaction to call lock_page.
@@ -668,7 +648,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
                  * altogether.
                  */
                 if (current->flags & PF_MEMALLOC)
-                        goto move_newpage;
+                        goto out;
 
                 lock_page(page);
         }
@@ -785,27 +765,52 @@ uncharge:
                 mem_cgroup_end_migration(mem, page, newpage, rc == 0);
 unlock:
         unlock_page(page);
+out:
+        return rc;
+}
 
-move_newpage:
+/*
+ * Obtain the lock on page, remove all ptes and migrate the page
+ * to the newly allocated page in newpage.
+ */
+static int unmap_and_move(new_page_t get_new_page, unsigned long private,
+                        struct page *page, int force, bool offlining, bool sync)
+{
+        int rc = 0;
+        int *result = NULL;
+        struct page *newpage = get_new_page(page, private, &result);
+
+        if (!newpage)
+                return -ENOMEM;
+
+        if (page_count(page) == 1) {
+                /* page was freed from under us. So we are done. */
+                goto out;
+        }
+
+        if (unlikely(PageTransHuge(page)))
+                if (unlikely(split_huge_page(page)))
+                        goto out;
+
+        rc = __unmap_and_move(page, newpage, force, offlining, sync);
+out:
         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);
+                /*
+                 * 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);
                 dec_zone_page_state(page, NR_ISOLATED_ANON +
                                 page_is_file_cache(page));
                 putback_lru_page(page);
         }
-
         /*
          * Move the new page to the LRU. If migration was not successful
          * then this will free the page.
          */
         putback_lru_page(newpage);
-
         if (result) {
                 if (rc)
                         *result = rc;