无法写入EMMC，提示无法卸载分区

[rule2c]

AMLOGIC_SOC Value[ s905d ] FDTFILE Value [meson-gxl-s905d-phicomm-n1.dtb ] MAINLINE UBOOT Value []UBOOT_OVERLOAD Value [u-boot-n1.bin ] K510[0] ANDROID_UBooT Value [/lib/u-boot/u-boot-2015-phicomm-n1.bin ] /mnt/mmcblk2p4 umount -f /mnt/mmcblk2p4 umount: /mnt/mmcblk2p4: target is busy. /mnt/mmcblk2p4 Cannot be uninstalled, the installation process is aborted.

求大佬指点，谢谢。