Re: writable swap cache explained (it's weird)

Richard Gooch (Richard.Gooch@atnf.CSIRO.AU)
Fri, 31 Jul 1998 09:14:21 +1000

Linus Torvalds writes:
>
>
> On Thu, 30 Jul 1998, Benjamin C.R. LaHaise wrote:
> >
> > (a) sounds like the Obvious Thing To Do in the mmap method for /proc, but
> > will break xdos. Wtf were they thinking in writing that insane code?
> > Hmmm, this bug probably applies to 2.0 too.... in a much more subtle
> > fashion.
>
> The insane code is indeed insane, but I think I understand why they did
> it: they didn't want to mess around with sysv shared memory regions.
>
> I'd love to just completely get rid of mmap() on /proc/self/mem, because
> it actually is a bad idea completely (not just the shared mappings - even
> a private mapping of another mapping that is shared has simply completely
> untenable logical problems).
>
> I'd much more prefer for somebody to take the time to change dosemu to use
> the standard (and supported) sysv shared memory setup than to make any
> kernel changes..

I think it would be better if they used the new POSIX.4 SHM support
(shm_open(3) and friends). To do that, though, the shmfs patch would
need to be included in the kernel, though. Yeah, yeah, I know: feature
freeze. But when has that ever stopped you? ;-)

Regards,

Richard....

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