percpu: add __percpu sparse annotations to fs

Add __percpu sparse annotations to fs.

These annotations are to make sparse consider percpu variables to be
in a different address space and warn if accessed without going
through percpu accessors.  This patch doesn't affect normal builds.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Alex Elder <aelder@sgi.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
diff --git a/include/linux/mount.h b/include/linux/mount.h
index 5d52753..b5f43a3 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -66,7 +66,7 @@
 	int mnt_pinned;
 	int mnt_ghosts;
 #ifdef CONFIG_SMP
-	int *mnt_writers;
+	int __percpu *mnt_writers;
 #else
 	int mnt_writers;
 #endif