mm: simplify lock_page_memcg()

Now that migration doesn't clear page->mem_cgroup of live pages anymore,
it's safe to make lock_page_memcg() and the memcg stat functions take
pages, and spare the callers from memcg objects.

[akpm@linux-foundation.org: fix warnings]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Suggested-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 11 insertions, 14 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index dc991510bb06..33be29675358 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -624,14 +624,14 @@ EXPORT_SYMBOL(mark_buffer_dirty_inode);
  * The caller must hold lock_page_memcg().
  */
 static void __set_page_dirty(struct page *page, struct address_space *mapping,
-                             struct mem_cgroup *memcg, int warn)
+                             int warn)
 {
         unsigned long flags;
 
         spin_lock_irqsave(&mapping->tree_lock, flags);
         if (page->mapping) {    /* Race with truncate? */
                 WARN_ON_ONCE(warn && !PageUptodate(page));
-                account_page_dirtied(page, mapping, memcg);
+                account_page_dirtied(page, mapping);
                 radix_tree_tag_set(&mapping->page_tree,
                                 page_index(page), PAGECACHE_TAG_DIRTY);
         }
@@ -666,7 +666,6 @@ static void __set_page_dirty(struct page *page, struct address_space *mapping,
 int __set_page_dirty_buffers(struct page *page)
 {
         int newly_dirty;
-        struct mem_cgroup *memcg;
         struct address_space *mapping = page_mapping(page);
 
         if (unlikely(!mapping))
@@ -686,14 +685,14 @@ int __set_page_dirty_buffers(struct page *page)
          * Lock out page->mem_cgroup migration to keep PageDirty
          * synchronized with per-memcg dirty page counters.
          */
-        memcg = lock_page_memcg(page);
+        lock_page_memcg(page);
         newly_dirty = !TestSetPageDirty(page);
         spin_unlock(&mapping->private_lock);
 
         if (newly_dirty)
-                __set_page_dirty(page, mapping, memcg, 1);
+                __set_page_dirty(page, mapping, 1);
 
-        unlock_page_memcg(memcg);
+        unlock_page_memcg(page);
 
         if (newly_dirty)
                 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
@@ -1167,15 +1166,14 @@ void mark_buffer_dirty(struct buffer_head *bh)
         if (!test_set_buffer_dirty(bh)) {
                 struct page *page = bh->b_page;
                 struct address_space *mapping = NULL;
-                struct mem_cgroup *memcg;
 
-                memcg = lock_page_memcg(page);
+                lock_page_memcg(page);
                 if (!TestSetPageDirty(page)) {
                         mapping = page_mapping(page);
                         if (mapping)
-                                __set_page_dirty(page, mapping, memcg, 0);
+                                __set_page_dirty(page, mapping, 0);
                 }
-                unlock_page_memcg(memcg);
+                unlock_page_memcg(page);
                 if (mapping)
                         __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
         }
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 5f85ebc52a98..5c57b7b40728 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -1957,7 +1957,6 @@ xfs_vm_set_page_dirty(
         loff_t                  end_offset;
         loff_t                  offset;
         int                     newly_dirty;
-        struct mem_cgroup       *memcg;
 
         if (unlikely(!mapping))
                 return !TestSetPageDirty(page);
@@ -1981,7 +1980,7 @@ xfs_vm_set_page_dirty(
          * Lock out page->mem_cgroup migration to keep PageDirty
          * synchronized with per-memcg dirty page counters.
          */
-        memcg = lock_page_memcg(page);
+        lock_page_memcg(page);
         newly_dirty = !TestSetPageDirty(page);
         spin_unlock(&mapping->private_lock);
 
@@ -1992,13 +1991,13 @@ xfs_vm_set_page_dirty(
                 spin_lock_irqsave(&mapping->tree_lock, flags);
                 if (page->mapping) {    /* Race with truncate? */
                         WARN_ON_ONCE(!PageUptodate(page));
-                        account_page_dirtied(page, mapping, memcg);
+                        account_page_dirtied(page, mapping);
                         radix_tree_tag_set(&mapping->page_tree,
                                         page_index(page), PAGECACHE_TAG_DIRTY);
                 }
                 spin_unlock_irqrestore(&mapping->tree_lock, flags);
         }
-        unlock_page_memcg(memcg);
+        unlock_page_memcg(page);
         if (newly_dirty)
                 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
         return newly_dirty;