mount folder in android 6

Hi all.
Can you help me. I need mount folder in internal_sd to external_sd how can see in all app. I tried use app Folder_mount, but this app don't work in my rom.
I have:
Android 6.0.1 (Lenovo K3 Note)
SuperSU Pro v2.76 (mount namespace separation is disabled)
BusyBox v1.21.1-jb static
mount symlinked to toolbox, umount symlinked to toybox

storage/E690-B8B6 - external_sd
/storage/emulated/0 - internal_sd

I am tried it for test

Code:

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shell@aio_otfp_m:/ $ su
su
root@aio_otfp_m:/ # id
id
uid=0(root) gid=0(root) groups=0(root) context=u:r:init:s0
root@aio_otfp_m:/ # su -m
su -m
root@aio_otfp_m:/ # id
id
uid=0(root) gid=0(root) groups=0(root) context=u:r:init:s0
root@aio_otfp_m:/ # getenforce
getenforce
Permissive
root@aio_otfp_m:/ # grep -A5 debuggerd /init.rc
grep -A5 debuggerd /init.rc
service debuggerd /system/bin/debuggerd
    class main

service debuggerd64 /system/bin/debuggerd64
    class main

service ril-daemon /system/bin/rild
    class main
    socket rild stream 660 root radio
root@aio_otfp_m:/ # mkdir /storage/emulated/0/a
mkdir /storage/emulated/0/a
root@aio_otfp_m:/ # mkdir /storage/E690-B8B6/b
mkdir /storage/E690-B8B6/b
root@aio_otfp_m:/ # echo >/storage/emulated/0/a/1
echo >/storage/emulated/0/a/1
root@aio_otfp_m:/ # ls /storage/emulated/0/a
ls /storage/emulated/0/a
1
root@aio_otfp_m:/ # ls /storage/E690-B8B6/b
ls /storage/E690-B8B6/b
root@aio_otfp_m:/ # busybox mount -o bind /storage/emulated/0/a /storage/E690-B8B6/b
ox mount -o bind /storage/emulated/0/a /storage/E690-B8B6/b                  <
root@aio_otfp_m:/ # grep ' /storage/E690-B8B6/b ' /proc/mounts
grep ' /storage/E690-B8B6/b ' /proc/mounts
/data/media /storage/E690-B8B6/b sdcardfs rw,nosuid,nodev,noexec,noatime,uid=1023,gid=1023,upper=0:1015:0660:0771,derive=multi 0 0
root@aio_otfp_m:/ # ls -ld /storage/E690-B8B6/b
ls -ld /storage/E690-B8B6/b
drwxrwx--x root    sdcard_rw          2016-07-04 18:30 b
root@aio_otfp_m:/ # ls -l /storage/E690-B8B6/b
ls -l /storage/E690-B8B6/b
-rw-rw---- root    sdcard_rw        1 2016-07-04 18:30 1
root@aio_otfp_m:/ # busybox umount /storage/E690-B8B6/b
busybox umount /storage/E690-B8B6/b
root@aio_otfp_m:/ #

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mounting works, but only in one namespace. How can I need to mount for all app can see the mounting?
Thank you and sorry for my English.