Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley
        Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United
        Kingdom.
        Registered in England and Wales under Company Registration No. 3798903
From:   David Howells <dhowells@redhat.com>
In-Reply-To: <CALF+zOkvC7kZ9LFQyjsRduQq+-gmaD4bLWc7H=AtVi6=NuC_dA@mail.gmail.com>
References: <CALF+zOkvC7kZ9LFQyjsRduQq+-gmaD4bLWc7H=AtVi6=NuC_dA@mail.gmail.com> <163967073889.1823006.12237147297060239168.stgit@warthog.procyon.org.uk> <163967182112.1823006.7791504655391213379.stgit@warthog.procyon.org.uk>
To:     David Wysochanski <dwysocha@redhat.com>
Cc:     dhowells@redhat.com, linux-cachefs <linux-cachefs@redhat.com>,
        Trond Myklebust <trond.myklebust@hammerspace.com>,
        Anna Schumaker <anna.schumaker@netapp.com>,
        linux-nfs <linux-nfs@vger.kernel.org>,
        Trond Myklebust <trondmy@hammerspace.com>,
        Jeff Layton <jlayton@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 63/68] nfs: Convert to new fscache volume/cookie API
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <1958025.1639747261.1@warthog.procyon.org.uk>
Content-Transfer-Encoding: quoted-printable
Date:   Fri, 17 Dec 2021 13:21:01 +0000
Message-ID: <1958026.1639747261@warthog.procyon.org.uk>
Precedence: bulk

David Wysochanski <dwysocha@redhat.com> wrote:

> >
> >  (4) fscache_enable/disable_cookie() have been removed.
> >
> >      Call fscache_use_cookie() and fscache_unuse_cookie() when a file =
is
> >      opened or closed to prevent a cache file from being culled and to=
 keep
> >      resources to hand that are needed to do I/O.
> >
> >      Unuse the cookie when a file is opened for writing.  This is gate=
d by
> >      the NFS_INO_FSCACHE flag on the nfs_inode.
> >
> >      A better way might be to invalidate it with FSCACHE_INVAL_DIO_WRI=
TE
> >      which will keep it unused until all open files are closed.
> >
> =

> Comment still out of date here, reference
> https://marc.info/?l=3Dlinux-nfs&m=3D163922984027745&w=3D4

Okay, how about:

 (4) fscache_enable/disable_cookie() have been removed.

     Call fscache_use_cookie() and fscache_unuse_cookie() when a file is
     opened or closed to prevent a cache file from being culled and to kee=
p
     resources to hand that are needed to do I/O.

     If a file is opened for writing, we invalidate it with
     FSCACHE_INVAL_DIO_WRITE in lieu of doing writeback to the cache,
     thereby making it cease caching until all currently open files are
     closed.  This should give the same behaviour as the uptream code.
     Making the cache store local modifications isn't straightforward for
     NFS, so that's left for future patches.

David