Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20220517100744.26849-1-dharamhans87@gmail.com>
 <CAJfpegsDxsMsyfP4a_5H1q91xFtwcEdu9-WBnzWKwjUSrPNdmw@mail.gmail.com> <f3555e3c-06d9-4d19-d3a2-9a2779937e83@ddn.com>
In-Reply-To: <f3555e3c-06d9-4d19-d3a2-9a2779937e83@ddn.com>
From:   Miklos Szeredi <miklos@szeredi.hu>
Date:   Thu, 19 May 2022 20:16:11 +0200
Message-ID: <CAJfpegsJijCeNZ9ES72e=gDNDisK5itG67GK8xNWRar=HMm6gA@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,
        fuse-devel <fuse-devel@lists.sourceforge.net>,
        linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Thu, 19 May 2022 at 19:42, Bernd Schubert <bschubert@ddn.com> wrote:

> Can you help me a bit to understand what we should change? I had also
> already thought to merge CREATE_EXT and OPEN_ATOMIC - so agreed.
> Shall we make the other cases more visible?

Make it clear in the code flow if we are using the new request or the
old; e.g. rename current fuse_atomic_open() to fuse_open_nonatomic()
and do

static int fuse_open_atomic(...)
{
    ...
    args.opcode = FUSE_OPEN_ATOMIC;
    ...
    err = fuse_simple_request(...);
    if (err == -ENOSYS)
        goto fallback;
    ...
fallback:
    return fuse_open_nonatomic();
}

static int fuse_atomic_open(...)
{
    if (fc->no_open_atomic)
        return fuse_open_nonatomic();
    else
        return fuse_open_atomic();
}

Also we can tweak fuse_dentry_revalidate() so it always invalidates
negative dentries if the new atomic open is available, and possibly
for positive dentries as well, if the rfc patch makes it.

Thanks,
Miklos