So let's say I have a file attached to a loop device /dev/loop1 how could I mount that using fuse (filesystem in user space) ?
If you're using fuse, you don't need a loop device at all, and can directly mount the file itself. So, you can do either this:
$ sudo fuseext2 -o rw+ test.ext2 /mnt
Or, if for some bizarre reason you really want to use a loop device, this:
$ sudo losetup test.ext2 /dev/loop0 $ sudo fuseext2 -o rw+ /dev/loop0 /mnt