[BusyBox] [Fwd: Loopback device setup?]

[Hugh Dickins]

On Tue, 17 Feb 2004, vda wrote:
> On Tuesday 17 February 2004 02:20, Tom Guilliams wrote:
> > in /driver/block/loop.c -
> >
> > loop_set_fd()
> >
> > 		/*
> >                   * If we can't read - sorry. If we only can't write -
> >                  		 * well, it's going to be read-only.
> >                   */
> >                  if (!aops->readpage)
> >                          goto out_putf;
> >
> > I confirmed the "if (!aops->readpage)" is true.  I'm not sure what the
> > readpage routine is trying to do (which dev or file) in my command below -
> > # mount -t ext2 -o loop ramdisk.image rootfs
> >
> > Anyone have any thoughts??  This is all being done in the /tmp
> > dircectory which is mounted as "tmpfs".  Not sure if that has anything
> > to do with it.
> 
> I recall that tmpfs cannot do readpage (by design?).
> CCing LKML, maybe someone will pour in more info.

readpage is not straightforward for tmpfs, so it took a long time
to be added, but tmpfs has supported loop since 2.4.22 and 2.5.45.

Hugh