(If you're finding how to move obb to external sdcard and mount it back to internal Finally, here's the right place!) Finally I found the solution ofto this question by myself! The app can't access the obb by itself, it requires media_rw to access it. Found by lsof:
sdcard 340 media_rw 15 ??? ??? ??? ???
/data/media/obb/com.game/com.game.obb
sdcard 340 media_rw 17 ??? ??? ??? ???
/data/media/obb/com.game/com.game.obb
com.game 26335 u0_a266 36 ??? ??? ??? ???
/storage/emulated/0/Android/obb/com.game/com.game.obb
com.game 26335 u0_a266 37 ??? ??? ??? ???
/storage/emulated/0/Android/obb/com.game/com.game.obb
So I have to mount the external sdcard folder to two places and each has to have its right owner:
owner folder
u0_a266 /storage/emulated/legacy/Android/obb/com.game
media_rw /data/media/obb/com.game
But if I mount /storage/sdcard1/Android/obb/com.game to those two places, it will become:
owner folder
u0_a266 /storage/emulated/legacy/Android/obb/com.game
u0_a266 /data/media/obb/com.game
Then I found if I do:
mount -o bind /storage/sdcard1/Android/obb/com.game /storage/emulated/legacy/Android/obb/com.game
mount -o bind /mnt/media_rw/sdcard1/Android/obb/com.game /data/media/obb/com.game
I found this works fine, because the mount command's source and destination is their original owner. The app can run very well!
