ext4: let getattr report the right blocks in delalloc+bigalloc

In delayed allocation, i_reserved_data_blocks now indicates
clusters, not blocks. So report it in the right number.

This can be easily exposed by the following command:
echo foo > blah; du -hc blah; sync; du -hc blah

Reported-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/inode.c

@@ -4301,7 +4301,8 @@ int ext4_getattr(struct vfsmount *mnt, struct dentry *dentry,
 	 * will return the blocks that include the delayed allocation
 	 * blocks for this file.
 	 */
-	delalloc_blocks = EXT4_I(inode)->i_reserved_data_blocks;
+	delalloc_blocks = EXT4_C2B(EXT4_SB(inode->i_sb),
+				EXT4_I(inode)->i_reserved_data_blocks);
 
 	stat->blocks += (delalloc_blocks << inode->i_sb->s_blocksize_bits)>>9;
 	return 0;