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SubjectRe: [PATCH/RFC] Lustre VFS patch
On Tue, May 25 2004, braam wrote:
> Jens,
>
> I think do answer your question:
> ...
> > > If we were to return errors, (which, I agree, _seems_ much
> > more sane,
> > > and we _did_ try that for a while!) then there is a good chance,
> > > namely immediately when something is flushed to disk, that
> > the system
> > > will detect the errors and not continue to execute
> > transactions making
> > > consistent testing of our replay mechanisms impossible.
>
> So: we can use the flags, but we cannot return the errors.

The generic_make_request() change itself is fine, as long as the proper
error is propagated back. I don't object to that at all, and I outlined
that to Phil last week as well. So in short:

if (bio_data_dir(bio) == WRITE && bdev_read_only(bio->bi_bdev)) {
bio_endio(bio, bio->bi_size, -EROFS);
break;
}
If you want to pass back 0 instead, then that would be a one-liner in
your (private) debugging patch. Ok?

> > And if this it to make sense for inclusion, io _must_ be
> > ended with -EROFS or similar.
> >
> > It seems to me that this probably belongs in your test
> > harness for debugging purposes. At least in its current state
> > it's not acceptable for inclusion.
>
> This is, as I mentioned, only for testing. It is, clearly, NOT ordinary
> system behavior at all since we don't, and won't, return the error.
>
> Some people find it very convenient to have this available, but if the
> opinion is that it is better to let development teams manage their own
> testing infrastructure that is acceptable to me.

I don't think this change makes sense as written for the generic
kernels, not if you want to simply ignore the write. If that is the
case, it's a special case debug entry for a very narrow use (ie lustre).

--
Jens Axboe

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