[syslinux] extlinux and block loopbacks

[branen salmon]

Hello--

I'm trying to use extlinux to make a bootable disk image, but I've hit
a wall.  I've got a partitioned hard disk image with one ext2
partition in it.  I've mounted the partition through a block loopback
device (/dev/loop1 on the host) and chrooted into it in order to run
extlinux.  Within the chroot environment, /etc/mtab says:

  /dev/hda1 / ext2 rw 0 0

...and within the chroot, /dev/hda1 is a device node for the loopback.

But when I run extlinux, it complains:

  extlinux: cannot find device for path /boot

I'm confused.  I know that extlinux is reading /etc/mtab, and I know
that the loopback node (/dev/hda1) works.  Furthermore, if I copy the
entire disk image onto a USB keydrive, change the /dev/hda1 device
node to point to the appropriate device, chroot, and run extlinux,
everything goes happily.

Is there some intrinsic incompatibility between extlinux and the block
loopback device?  I'm at a loss.

Thanks!

--branen