the loop devices don't get disassociated automatically when umounting

[zaoqi]

schuhumi commented: (https://www.mobileread.com/forums/showpost.php?p=3885242&postcount=7)

I found out that the loop devices don't get disassociated automatically when umounting, you can check like this:

[root@kindle kual-linuxdeploy-armhf]# cat /sys/block/loop*/loop/backing_file 
/dev/mmcblk0p4
/mnt/us/extensions/kual-linuxdeploy-armhf/rootfs.img (deleted)
/mnt/us/extensions/kual-linuxdeploy-armhf/rootfs.img
/usr/share/X11/xkb.sqsh
/usr/java/lib/fonts.sqsh
/etc/kdb.src.sqsh
/usr/lib/locale.sqsh
/usr/share/keyboard.sqsh
/opt/var/local.sqsh
/mnt/us/extensions/kual-linuxdeploy-armhf/rootfs.img (deleted)
/mnt/us/extensions/kual-linuxdeploy-armhf/rootfs.img (deleted)

That for me leads to a) running out of loop devices at one point (max 16) b) storage doesn't get freed when deleting the umounted image (df -h). Thus I disassociate it manually:

LOOPDEV="$(mount | grep loop | grep /tmp/alpine | cut -d" " -f1)"
... umounts ...
losetup -d $LOOPDEV