mount: remount doesn't care about loop=

mount: remount doesn't care about loop=

The command

   # mount -oremount <spec> <dir>

doesn't read fstab or mtab. This is expected behaviour. Unfortunately,
we have to care about the internal loop= option which is generated and
maintained by mount(8)/umount(8). The loop= option has to be persistent.

How to reproduce this bug:

 # mount -o loop       /home/images/vfat.img /mnt/img; grep vfat /etc/mtab; \
   mount -o remount,ro /home/images/vfat.img /mnt/img; grep vfat /etc/mtab;

 /home/images/vfat.img /mnt/img vfat rw,loop=/dev/loop0 0 0
 /home/images/vfat.img /mnt/img vfat ro 0 0

Reported-By: David Chinner <dgc@sgi.com>
Signed-off-by: Karel Zak <kzak@redhat.com>