opi3 sdcard hotplug via udev, but fail. Why?

I have move system to emmc, and want to use sdcard to storage videos from camera. So I want to sdcard can automount/umount after hotplug.

I have try to use udev to fulfill it. But it seems not work.

I add a rules for udev at /etc/udev/rules.d:

ACTION=="add",KERNEL=="mmcblk2p1",RUN+="/etc/udev/sdcard_hotplug.sh add /home/opi/Videos/sdcard %k"
ACTION=="remove",KERNEL=="mmcblk2p1",RUN+="/etc/udev/sdcard_hotplug.sh remove /home/opi/Videos/sdcard %k"

And add a shell file at /etc/udev/sdcard_hotplug.sh

#!/bin/bash
case $1 in
	add)
		mkdir -p $2
		mount -t exfat -o iocharset=utf8,rw,sync,umask=0000,dmask=0000,fmask=0000 /dev/$3 $2
		;;
	remove)
		umount $2
		rm -rf $2
		;;
esac

Add chmod a+x for it. Test it ok.

But udev seems not work!

I have use udev monitor to test if remove and insert sdcard can generate event. It works. 

And use udevadm test, and it also ok.

Anybody can help me?