Re: [PATCH v3 63/68] nfs: Convert to new fscache volume/cookie API

[David Wysochanski]

On Fri, Dec 17, 2021 at 8:21 AM David Howells <dhowells@xxxxxxxxxx> wrote:
>
> David Wysochanski <dwysocha@xxxxxxxxxx> 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 gated by
> > >      the NFS_INO_FSCACHE flag on the nfs_inode.
> > >
> > >      A better way might be to invalidate it with FSCACHE_INVAL_DIO_WRITE
> > >      which will keep it unused until all open files are closed.
> > >
> >
> > Comment still out of date here, reference
> > https://marc.info/?l=linux-nfs&m=163922984027745&w=4
>
> 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 keep
>      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.
>

Yes, that is more accurate.