Re: [RFC 1/1] NFSD add vfs_fsync after async copy is done

[Olga Kornievskaia <olga.kornievskaia@xxxxxxxxx>]

On Thu, Apr 22, 2021 at 12:54 PM <dai.ngo@xxxxxxxxxx> wrote:
>
>
> On 4/22/21 9:19 AM, Olga Kornievskaia wrote:
> > From: Olga Kornievskaia <kolga@xxxxxxxxxx>
> >
> > Currently, the server does all copies as NFS_UNSTABLE. For synchronous
> > copies linux client will append a COMMIT to the COPY compound but for
> > async copies it does not (because COMMIT needs to be done after all
> > bytes are copied and not as a reply to the COPY operation).
> >
> > However, in order to save the client doing a COMMIT as a separate
> > rpc, the server can reply back with NFS_FILE_SYNC copy. This patch
> > proposed to add vfs_fsync() call at the end of the async copy.
> >
> > Signed-off-by: Olga Kornievskaia <kolga@xxxxxxxxxx>
> > ---
> >   fs/nfsd/nfs4proc.c | 22 +++++++++++++++++-----
> >   1 file changed, 17 insertions(+), 5 deletions(-)
> >
> > diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> > index 66dea2f1eed8..c6f45f67d59b 100644
> > --- a/fs/nfsd/nfs4proc.c
> > +++ b/fs/nfsd/nfs4proc.c
> > @@ -1536,19 +1536,21 @@ static const struct nfsd4_callback_ops nfsd4_cb_offload_ops = {
> >       .done = nfsd4_cb_offload_done
> >   };
> >
> > -static void nfsd4_init_copy_res(struct nfsd4_copy *copy, bool sync)
> > +static void nfsd4_init_copy_res(struct nfsd4_copy *copy, bool sync,
> > +                             bool committed)
> >   {
> > -     copy->cp_res.wr_stable_how = NFS_UNSTABLE;
> > +     copy->cp_res.wr_stable_how = committed ? NFS_FILE_SYNC : NFS_UNSTABLE;
> >       copy->cp_synchronous = sync;
> >       gen_boot_verifier(&copy->cp_res.wr_verifier, copy->cp_clp->net);
> >   }
> >
> > -static ssize_t _nfsd_copy_file_range(struct nfsd4_copy *copy)
> > +static ssize_t _nfsd_copy_file_range(struct nfsd4_copy *copy, bool *committed)
> >   {
> >       ssize_t bytes_copied = 0;
> >       size_t bytes_total = copy->cp_count;
> >       u64 src_pos = copy->cp_src_pos;
> >       u64 dst_pos = copy->cp_dst_pos;
> > +     __be32 status;
> >
> >       do {
> >               if (kthread_should_stop())
> > @@ -1563,6 +1565,15 @@ static ssize_t _nfsd_copy_file_range(struct nfsd4_copy *copy)
> >               src_pos += bytes_copied;
> >               dst_pos += bytes_copied;
> >       } while (bytes_total > 0 && !copy->cp_synchronous);
> > +     /* for a non-zero asynchronous copy do a commit of data */
> > +     if (!copy->cp_synchronous && bytes_copied > 0) {
>
> I think (bytes_copied > 0) should be (bytes_total < copy->cp_count).

I don't think so. A successful async copy should never be less the
requested bytes.

>
> -Dai
>
> > +             down_write(&copy->nf_dst->nf_rwsem);
> > +             status = vfs_fsync_range(copy->nf_dst->nf_file,
> > +                                      copy->cp_dst_pos, bytes_copied, 0);
> > +             up_write(&copy->nf_dst->nf_rwsem);
> > +             if (!status)
> > +                     *committed = true;
> > +     }
> >       return bytes_copied;
> >   }
> >
> > @@ -1570,15 +1581,16 @@ static __be32 nfsd4_do_copy(struct nfsd4_copy *copy, bool sync)
> >   {
> >       __be32 status;
> >       ssize_t bytes;
> > +     bool committed = false;
> >
> > -     bytes = _nfsd_copy_file_range(copy);
> > +     bytes = _nfsd_copy_file_range(copy, &committed);
> >       /* for async copy, we ignore the error, client can always retry
> >        * to get the error
> >        */
> >       if (bytes < 0 && !copy->cp_res.wr_bytes_written)
> >               status = nfserrno(bytes);
> >       else {
> > -             nfsd4_init_copy_res(copy, sync);
> > +             nfsd4_init_copy_res(copy, sync, committed);
> >               status = nfs_ok;
> >       }
> >