Re: FS-Cache for cifs

[Xiaoli Feng <xifeng@redhat.com>]

Thanks Steve for the info. File a bug for cifs fscache.

Bug 208883 - CIFS: kernel BUG at fs/cachefiles/rdwr.c:715!
https://bugzilla.kernel.org/show_bug.cgi?id=208883


----- Original Message -----
> From: "Steve French" <smfrench@gmail.com>
> To: "Xiaoli Feng" <xifeng@redhat.com>
> Cc: "CIFS" <linux-cifs@vger.kernel.org>, "David Howells" <dhowells@redhat.com>
> Sent: Tuesday, August 11, 2020 10:12:28 AM
> Subject: Re: FS-Cache for cifs
> 
> My tests in recent kernels with fscache and cifs.ko worked but didn't
> provide much performance benefit (which would be expected since close
> releases leases )
> 
> On Mon, Aug 10, 2020, 20:51 Steve French <smfrench@gmail.com> wrote:
> 
> > fscache (perhaps more so with the recent rewrite that Dave Howells
> > did) may be most well suited to cifs.ko (SMB3.1.1 mounts) among the
> > various file systems since it would allow offline caching of files and
> > directories leveraging:
> > 1) handle leases and directory leases for "strict caching" models
> > or
> > 2) directory change notification for "loose caching" models
> > (Although file version numbers are not provided, the combination of
> > creation time, 64 bit DiskFileId, and last write time with 100ns time
> > granularity is probably sufficient to use in conjunction with this)
> > In addition the protocol already supports four flags to control
> > whether client side offline caching can/should be done:
> >    SMB2_SHAREFLAG_MANUAL_CACHING
> >    SMB2_SHAREFLAG_AUTO_CACHING
> >    SMB2_SHAREFLAG_VDO_CACHING
> >    SMB2_SHAREFLAG_NO_CACHING
> >
> > So fscache could be very, very useful for cifs.ko, especially for
> > metadata heavy workloads that are largely from one client ... but
> > fscache doesn't have tight integration with many cifs features (like
> > handle leases e.g.) yet.
> >
> > It would make sense to better tie cifs.ko in with fscache (especially
> > as it has shown to be useful on other operating systems over
> > SMB3/SMB3.1.1).
> >
> > On Mon, Aug 10, 2020 at 8:25 PM Xiaoli Feng <xifeng@redhat.com> wrote:
> > >
> > > Hello everyone,
> > >
> > > Recently I'd like to test fs-cache for cifs. But CONFIG_CIFS_FSCACHE is
> > not set defaultly.
> > > Are there any concern to enable it? Test it to enbale fs-cache. It seems
> > work. The file
> > > /proc/fs/fscache/stats is update when do some cp operations.
> > >
> > > Thanks.
> > >
> > > --
> > > Best regards!
> > > XiaoLi Feng 冯小丽
> > >
> >
> >
> > --
> > Thanks,
> >
> > Steve
> >
>