Re: Lots of SCSI-disks, how?!

Richard Gooch (Richard.Gooch@atnf.CSIRO.AU)
Wed, 22 Apr 1998 13:08:18 +1000


Ulrich Drepper writes:
> Richard Gooch <Richard.Gooch@atnf.CSIRO.AU> writes:
>
> > Correct. We were just using 64 bits as an example.
> > [...]
> > I don't see how you could increase the size of i_rdev in the kernel's
> > struct inode without breaking C library compatibility, since the
> > library expects i_rdev to be 16 bits followed by i_size.
>
> It is possible when all functions passing device numbers to the kernel
> can fall back into 16bit mode. The major/minor/makedev macros would
> always use the new format and the libc makes sure it works.
>
> And I don't speak about splitting the device numbering. It's just
> that some numbers are avoided withthe new numbering scheme and those
> are recognized specially by the kernel.

OK, I don't understand how this could work. Could you please show
exactly what changes you would make to the kernel struct inode?

> > Also, I don't like the idea that libc 5 applications (like <fdisk>
> > and other useful tools) cannot access the new devices/partitions.
>
> Of course not. This will break in any case.
>
> > Finally, I don't see how your scheme can work to support more SCSI
> > minors. Unless you have a whole new SCSI driver on one of the "high"
> > majors. Yuk. That gets back to the problem of "blocking" libc 5 access
> > to some of your discs.
>
> With libc5 you will never be able to change the device numbering. See
> above, you agreed already. So the remaining question is how to keep
> libc5 alive on new kernels which don't need many SCSI IDs etc, i.e.,
> in situations which can be handled now.

That's the point. I don't like blocking libc 5 access to the 17th SCSI
disc. We don't *have* to do that. There is a way of supporting more
than 16 SCSI discs and *still* give access to all those discs with
libc 5. The same scheme would even work for for libc 4.

Regards,

Richard....

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