nilfs2: implement resize ioctl

This adds resize ioctl which makes online resize possible.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
diff --git a/fs/nilfs2/nilfs.h b/fs/nilfs2/nilfs.h
index a8dd344..09af009 100644
--- a/fs/nilfs2/nilfs.h
+++ b/fs/nilfs2/nilfs.h
@@ -298,6 +298,7 @@
 					       int flip);
 int nilfs_commit_super(struct super_block *sb, int flag);
 int nilfs_cleanup_super(struct super_block *sb);
+int nilfs_resize_fs(struct super_block *sb, __u64 newsize);
 int nilfs_attach_checkpoint(struct super_block *sb, __u64 cno, int curr_mnt,
 			    struct nilfs_root **root);
 int nilfs_checkpoint_is_mounted(struct super_block *sb, __u64 cno);