Re: [PATCH 17/20] FRV: Better mmap support in uClinux

[David Howells]

> >  (3) Files (and blockdevs) cannot be mapped shared since it is not
> >  really possible to honour this by writing any changes back to the
> >  backing device.
> 
> [way behind on email]
> 
> I think this could be done at msync, munmap and exit time? You end up
> flushing the entire mapping, but it's still correct (and POSIX
> compliant).

Don't forget write() too. If someone does a write, that would have to be
written over the mapping too. Obviously this is not impossible.

> And, if you wanted to be really clever, you could store a hash of each
> page to detect changes and avoid the extra I/O.

It'd probably have to be something like an md5 sum.

Okay, technically, we could probably emulate it, but is it worth it? I think
it's something to bear in mind for another time.

More to the point, perhaps, is making shared memory stuff work.

David
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