[Yaffs] mount again error

dear all, I do the follow steps flash_eraseall dev/mtd3 nandwrite -a -o dev/mtd3 yaffs2_fs.img mount -t yaffs2 dev/mtdblock3 mnt/yaffs umount mnt/yaffs mount -t yaffs2 dev/mtdblock3 mnt/yaffsPartially written block 6 being set for retirementPartially written block 6 being set for retirementPartially written block 6 being set for retirementPartially written block 6 being set for retirementPartially written block 6 being set for retirementPartially written block 6 being set for retirementPartially written block 6 being set for retirementPartially written block 6 being set for retirementPartially written block 6 being set for retirementPartially written block 6 being set for retirementPartially written block 6 being set for retirementPartially written block 6 being set for retirementPartially written block 6 being set for retirementPartially written block 6 being set for retirementPartially written block 6 being set for retirement.....ls mnt/yaffsonly lost+foundwhy?thanks !