fs: Set the size of empty dirs to 0.

commit 4b75de86 upstream.

Before the make_empty_dir_inode calls were introduce into proc, sysfs,
and sysctl those directories when stated reported an i_size of 0.
make_empty_dir_inode started reporting an i_size of 2.  At least one
userspace application depended on stat returning i_size of 0.  So
modify make_empty_dir_inode to cause an i_size of 0 to be reported for
these directories.
Reported-by: Tejun Heo <tj@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

fs/libfs.c

@@ -1158,7 +1158,7 @@ void make_empty_dir_inode(struct inode *inode)
 	inode->i_uid = GLOBAL_ROOT_UID;
 	inode->i_gid = GLOBAL_ROOT_GID;
 	inode->i_rdev = 0;
-	inode->i_size = 2;
+	inode->i_size = 0;
 	inode->i_blkbits = PAGE_SHIFT;
 	inode->i_blocks = 0;