On Wed, Jan 27, 2016 at 05:30:45PM +0300, Vladimir Davydov wrote:

On Tue, Jan 26, 2016 at 04:00:02PM -0500, Johannes Weiner wrote:

quoted

@@ -683,17 +683,17 @@ int __set_page_dirty_buffers(struct page *page)
 		} while (bh != head);
 	}
 	/*
-	 * Use mem_group_begin_page_stat() to keep PageDirty synchronized with
-	 * per-memcg dirty page counters.
+	 * Lock out page->mem_cgroup migration to keep PageDirty
+	 * synchronized with per-memcg dirty page counters.
 	 */
-	memcg = mem_cgroup_begin_page_stat(page);
+	memcg = lock_page_memcg(page);
 	newly_dirty = !TestSetPageDirty(page);
 	spin_unlock(&mapping->private_lock);
 
 	if (newly_dirty)
 		__set_page_dirty(page, mapping, memcg, 1);

Do we really want to pass memcg to __set_page_dirty and then to
account_page_dirtied, increasing stack/regs usage even in case memory
cgroup is disabled? May be, it'd be better to make
mem_cgroup_update_page_stat take a page instead of a memcg?

I'll look into that. It will need changing migration to leave the
page->mem_cgroup binding of live pages alone, but that's something
worth doing anyway. It's beyond the scope of these patches, though.

Thanks

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