linux-kernel - Re: [PATCH 2/3] fuse: Add negative_dentry

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Message-ID: <CAD90VcZeoagh7a-0qA1SudJ3v53fvyr7t2iwGx_+dnAL7M=jnw@mail.gmail.com>
Date:   Wed, 21 Jun 2023 18:40:21 +0900
From:   Keiichi Watanabe <keiichiw@...omium.org>
To:     Miklos Szeredi <miklos@...redi.hu>
Cc:     Junichi Uekawa (上川純一) 
        <uekawa@...gle.com>, LKML <linux-kernel@...r.kernel.org>,
        mhiramat@...gle.com, takayas@...omium.org, drosen@...gle.com,
        sarthakkukreti@...gle.com, Jonathan Corbet <corbet@....net>,
        linux-doc@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 2/3] fuse: Add negative_dentry_timeout option

On Wed, Jun 21, 2023 at 1:07 PM Miklos Szeredi <miklos@...redi.hu> wrote:
>
> On Wed, 21 Jun 2023 at 00:53, Junichi Uekawa (上川純一) <uekawa@...gle.com> wrote:
> >
> > Hi
> >
> >
> >
> > 2023年6月21日(水) 4:28 Miklos Szeredi <miklos@...redi.hu>:
> >>
> >> On Tue, 20 Jun 2023 at 17:14, Keiichi Watanabe <keiichiw@...omium.org> wrote:
> >> >
> >> > Add `negative_dentry_timeout` mount option for FUSE to cache negative
> >> > dentries for the specified duration.
> >>
> >> This is already possible, no kernel changes needed.  See e.g.
> >> xmp_init() in libfuse/example/passthrough.c.
> >>
> >
> > Thank you for the pointer!
> >
> > So reading libfuse/fuse.c, fuse_lib_lookup does a reply with e.ino=0 err=0 (instead of ENOENT) with e.entry_timeout=negative_timeout,
> > for each lookup (and there's no global configuration but that's okay) ?
>
> Yes.


Oh, good to know!
I could make it work in our VMM (crosvm) without any kernel changes.
https://crrev.com/c/4630879
Thanks a lot!

Keiichi


>
>
> Thanks,
> Miklos