memcg: make page->mapping NULL before uncharge

This patch tries to make page->mapping to be NULL before
mem_cgroup_uncharge_cache_page() is called.

"page->mapping == NULL" is a good check for "whether the page is still
radix-tree or not".  This patch also adds BUG_ON() to
mem_cgroup_uncharge_cache_page();

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/filemap.c b/mm/filemap.c
index e1b23fd..ab85536 100644 (file)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -116,12 +116,12 @@ void __remove_from_page_cache(struct page *page)
 {
        struct address_space *mapping = page->mapping;
 
-       mem_cgroup_uncharge_cache_page(page);
        radix_tree_delete(&mapping->page_tree, page->index);
        page->mapping = NULL;
        mapping->nrpages--;
        __dec_zone_page_state(page, NR_FILE_PAGES);
        BUG_ON(page_mapped(page));
+       mem_cgroup_uncharge_cache_page(page);
 
        /*
         * Some filesystems seem to re-dirty the page even after

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e93a4db..6f8b5b3 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -734,6 +734,7 @@ void mem_cgroup_uncharge_page(struct page *page)
 void mem_cgroup_uncharge_cache_page(struct page *page)
 {
        VM_BUG_ON(page_mapped(page));
+       VM_BUG_ON(page->mapping);
        __mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_CACHE);
 }
 

diff --git a/mm/migrate.c b/mm/migrate.c
index 11c6c56..6602941 100644 (file)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -330,8 +330,6 @@ static int migrate_page_move_mapping(struct address_space *mapping,
        __inc_zone_page_state(newpage, NR_FILE_PAGES);
 
        spin_unlock_irq(&mapping->tree_lock);
-       if (!PageSwapCache(newpage))
-               mem_cgroup_uncharge_cache_page(page);
 
        return 0;
 }
@@ -341,6 +339,8 @@ static int migrate_page_move_mapping(struct address_space *mapping,
  */
 static void migrate_page_copy(struct page *newpage, struct page *page)
 {
+       int anon;
+
        copy_highpage(newpage, page);
 
        if (PageError(page))
@@ -378,8 +378,13 @@ static void migrate_page_copy(struct page *newpage, struct page *page)
 #endif
        ClearPagePrivate(page);
        set_page_private(page, 0);
+       /* page->mapping contains a flag for PageAnon() */
+       anon = PageAnon(page);
        page->mapping = NULL;
 
+       if (!anon) /* This page was removed from radix-tree. */
+               mem_cgroup_uncharge_cache_page(page);
+
        /*
         * If any waiters have accumulated on the new page then
         * wake them up.