Before connecting the usb cable and activating mass storage mode:
"lsof | grep mmc1" returns empty

Output of:
"ls -lR /proc/ | grep mmc1> tmp;clear; cat tmp;rm tmp" is empty also:

/proc/irq/86/mmc1:
[root ~]#

Output of:
"lsof /dev/media/" is "lsof: status error on /dev/media: No such file or directory"

Also, as I described in post #31 - after connecting the cable and activating mass storage mode, I can see that there are no files in /media/mmc1(and I also get the error mentioned "Only device storage connected, Memory card already in use")

if I disconnect the cable, I can see the card files again in /media/mmc, which I think shows that the mount/dismount worked correctly by mass storage mode.

I can also freely mount and umount mmc using the following with no errors (which causes the files in /media/mmc1 to be accessible/inaccessible):

mount /dev/mmcblk1p1 /media/mmc1
umount -f -l /media/mmc1