commit 62cccb8c8e7a3ca233f49d5e7dcb1557d25465cd
author Johannes Weiner <hannes@cmpxchg.org> Tue Mar 15 14:57:22 2016 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> Tue Mar 15 16:55:16 2016 -0700
tree 43a902faf461c65393a4efebf9ff9622017b92b1
parent 6a93ca8fde3cfce0f00f02281139a377c83e8d8c

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>

mm/truncate.c

diff --git a/mm/truncate.c b/mm/truncate.c
index 51a24f6..87311af 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -519,7 +519,6 @@
 static int
 invalidate_complete_page2(struct address_space *mapping, struct page *page)
 {
-	struct mem_cgroup *memcg;
 	unsigned long flags;
 
 	if (page->mapping != mapping)
@@ -528,15 +527,15 @@
 	if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL))
 		return 0;
 
-	memcg = lock_page_memcg(page);
+	lock_page_memcg(page);
 	spin_lock_irqsave(&mapping->tree_lock, flags);
 	if (PageDirty(page))
 		goto failed;
 
 	BUG_ON(page_has_private(page));
-	__delete_from_page_cache(page, NULL, memcg);
+	__delete_from_page_cache(page, NULL);
 	spin_unlock_irqrestore(&mapping->tree_lock, flags);
-	unlock_page_memcg(memcg);
+	unlock_page_memcg(page);
 
 	if (mapping->a_ops->freepage)
 		mapping->a_ops->freepage(page);
@@ -545,7 +544,7 @@
 	return 1;
 failed:
 	spin_unlock_irqrestore(&mapping->tree_lock, flags);
-	unlock_page_memcg(memcg);
+	unlock_page_memcg(page);
 	return 0;
 }