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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);

    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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