Re: Lots of SCSI-disks, how?!

David Woodhouse (Dave@imladris.demon.co.uk)
Wed, 22 Apr 1998 05:01:12 +0200


> David Woodhouse writes:
> > Richard.Gooch@atnf.CSIRO.AU said:
> > > 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.
> >
> > Translate it on syscall entry/exit iff current->personality == PER_LIBC5
>
> > Given that most programs which require such low level access are
> > available in source form, it'll be rare that this overhead is
> > incurred - most processes which use the affected syscalls will be
> > recompiled with glibc.
>
> Once again, you don't have to do any of this at all with devfs.

Don't you? I didn't think that devfs removed the need for more space in device
numbers internally - I simply thought it made the user interface far easier.

> > Add a second major # for the SCSI system, following one of the more sensible
> > schemes suggested. Keep the old major/minor numbers, but deprecate them in
> > much the same way as the cua devices.
>
> This does look a bit painful.

Perhaps, but it's not that bad, and similar things have been done before, with
the tty devices.

> So why not use devfs? The work is done.

Even with devfs, you need a sensible internal representation of the device
major and minor numbers, yes? How does devfs handle the case where you've got
a room full of SCSI drives, each with 63 partitions?

devfs provides an extremely useful way of presenting the extended devices to
libc[45] programs, and also for making them usable without an extension to
ext2fs, but can it really remove the need for a larger __kernel_dev_t, too?

(I ask this without having studied the source or the README, for which I
apologise.)

---- ---- ----
David Woodhouse, Robinson College, CB3 9AN, England. (+44) 0976 658355
Dave@imladris.demon.co.uk http://www.imladris.demon.co.uk
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