Re: Lots of SCSI-disks, how?!

Richard Gooch (Richard.Gooch@atnf.CSIRO.AU)
Wed, 22 Apr 1998 13:17:47 +1000


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

OK, now I see.

> Entry's simple, but translating back from 64-bit to 16-bit on exit may take
> some thought. Which syscalls return an inode?

Offhand, stat, fstat and lstat.

> 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.

> > 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.
>
> 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.

> This way, legacy programs can still have access to the devices, and
> the new system is available for anything which wants to use it. Your
> devfs will also help legacy programs to use new devices, if
> necessary.
>
> Bringing in a more sensible SCSI naming/numbering scheme has moved
> up on my list of priorities - I trashed my MBR earlier this evening
> because I tried to use my hard drive as a scanner :)

So why not use devfs? The work is done.

Regards,

Richard....

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