fs/xfs: fix f_ffree value for statfs when project quota is set

When project is set, we should use inode limit minus the used count

Signed-off-by: Ye Yin <[e-mail]>
Reviewed-by: Darrick J. Wong <[e-mail]>
Signed-off-by: Darrick J. Wong <[e-mail]>

fs/xfs/xfs_qm_bhv.c

···
 		statp->f_files = limit;
 		statp->f_ffree =
 			(statp->f_files > dqp->q_res_icount) ?
-			 (statp->f_ffree - dqp->q_res_icount) : 0;
+			 (statp->f_files - dqp->q_res_icount) : 0;
 	}
 }