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From:   Miklos Szeredi <miklos@szeredi.hu>
Date:   Thu, 1 Jun 2023 13:50:49 +0200
Message-ID: <CAJfpegswePPhVrDrwjZHbHb91iOkbfObnxFqzJU88U7pH86Row@mail.gmail.com>
Subject: Re: [PATCH v5 0/3] FUSE: Implement atomic lookup + open/create
To:     Bernd Schubert <bschubert@ddn.com>
Cc:     Dharmendra Singh <dharamhans87@gmail.com>,
        Vivek Goyal <vgoyal@redhat.com>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        fuse-devel <fuse-devel@lists.sourceforge.net>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Horst Birthelmer <horst@birthelmer.com>
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On Thu, 1 Jun 2023 at 13:17, Bernd Schubert <bschubert@ddn.com> wrote:
>
> Hi Miklos,
>
> On 5/19/22 11:39, Miklos Szeredi wrote:
> > On Tue, 17 May 2022 at 12:08, Dharmendra Singh <dharamhans87@gmail.com> wrote:
> >>
> >> In FUSE, as of now, uncached lookups are expensive over the wire.
> >> E.g additional latencies and stressing (meta data) servers from
> >> thousands of clients. These lookup calls possibly can be avoided
> >> in some cases. Incoming three patches address this issue.
> >>
> >>
> >> Fist patch handles the case where we are creating a file with O_CREAT.
> >> Before we go for file creation, we do a lookup on the file which is most
> >> likely non-existent. After this lookup is done, we again go into libfuse
> >> to create file. Such lookups where file is most likely non-existent, can
> >> be avoided.
> >
> > I'd really like to see a bit wider picture...
> >
> > We have several cases, first of all let's look at plain O_CREAT
> > without O_EXCL (assume that there were no changes since the last
> > lookup for simplicity):
> >
> > [not cached, negative]
> >     ->atomic_open()
> >        LOOKUP
> >        CREATE
> >
>
> [...]
>
> > [not cached]
> >     ->atomic_open()
> >         OPEN_ATOMIC
>
> new patch version is eventually going through xfstests (and it finds
> some issues), but I have a question about wording here. Why
> "OPEN_ATOMIC" and not "ATOMIC_OPEN". Based on your comment  @Dharmendra
> renamed all functions and this fuse op "open atomic" instead of "atomic
> open" - for my non native English this sounds rather weird. At best it
> should be "open atomically"?

FUSE_OPEN_ATOMIC is a specialization of FUSE_OPEN.  Does that explain
my thinking?

Thanks,
Miklos