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From:   Cedric Blancher <cedric.blancher@gmail.com>
Date:   Sun, 19 Nov 2023 18:58:35 +0100
Message-ID: <CALXu0UebE2oGgWLMn-NkfGq5n+2dEFnqrOy617SRMmKF-dGOXg@mail.gmail.com>
Subject: Re: How does READ_PLUS differ from READ?
To:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>
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On Sun, 19 Nov 2023 at 18:48, Anna Schumaker <schumaker.anna@gmail.com> wro=
te:
>
> Hi,
>
> On Sun, Nov 19, 2023 at 12:38=E2=80=AFPM Cedric Blancher
> <cedric.blancher@gmail.com> wrote:
> >
> > Good evening!
> >
> > How does READ_PLUS differ from READ? Has anyone made a simpler
> > presentation (PowerPoint slides) than the RFCs?
>
> No slides, but at a high level READ_PLUS can compress out long ranges
> of zeroes in a read reply by returning a HOLE segment instead of the
> actual zeroes. It's perfectly valid for the server to skip the zero
> detection and return everything as a data segment, however.

So how do you differ between
1. a hole, aka no filesystem blocks allocated
2. a long sequence of valid data with all zero bytes in them

Ced
--=20
Cedric Blancher <cedric.blancher@gmail.com>
[https://plus.google.com/u/0/+CedricBlancher/]
Institute Pasteur