Re: ufs filesystem cannot mount NetBSD/arm64 partition

[Al Viro <viro@zeniv.linux.org.uk>]

On Mon, Jan 15, 2024 at 10:22:20PM +0000, Al Viro wrote:
> On Mon, Jan 15, 2024 at 11:05:51PM +0100, Bruno Haible wrote:
> 
> > Whereas this partition can be mounted fine on FreeBSD, NetBSD, OpenBSD.
> > FreeBSD 11:
> > # mount -r -t ufs /dev/ada1s2 /mnt
> > NetBSD 9.3:
> > # mount -r -t ffs /dev/wd1a /mnt
> > OpenBSD 7.4:
> > # mount -r -t ffs /dev/wd1j /mnt
> > 
> > The source code line which emits the
> >   ufs: ufs_fill_super(): fragment size 8192 is too large
> > error is obviously linux/fs/ufs/super.c:1083.
> 
> Lovely...  Does it really have 8Kb fragments?  That would be painful
> to deal with - a plenty of places in there assume that fragment fits
> into a page...

FWIW, theoretically it might be possible to make that comparison with
PAGE_SIZE instead of 4096 and require 16K or 64K pages for the kernel
in question; that ought to work, modulo bugs in completely untested
cases ;-/

Support with 4K pages is a different story - that would take much
more surgery in fs/ufs.

Constraints:
	* fragment and block sizes are powers of 2.
	* block:fragment is 1, 2, 4 or 8.
Violating those is not an option for any kernel.
	* fragment fits into page.
Could be worked around, but not easily.

BTW, can NetBSD/i386 mount the same image?