Re: [RFC PATCH v4] ceph: use 'copy-from2' operation in copy_file_range

[Luis Henriques]

On Thu, Jan 09, 2020 at 11:05:50AM -0500, Jeff Layton wrote:
> On Thu, 2020-01-09 at 15:53 +0100, Ilya Dryomov wrote:
> > On Thu, Jan 9, 2020 at 3:30 PM Luis Henriques <lhenriques@xxxxxxxx> wrote:
> > > On Thu, Jan 09, 2020 at 08:06:17AM -0500, Jeff Layton wrote:
> > > > On Wed, 2020-01-08 at 10:03 +0000, Luis Henriques wrote:
> > > > > Instead of using the 'copy-from' operation, switch copy_file_range to the
> > > > > new 'copy-from2' operation, which allows to send the truncate_seq and
> > > > > truncate_size parameters.
> > > > > 
> > > > > If an OSD does not support the 'copy-from2' operation it will return
> > > > > -EOPNOTSUPP.  In that case, the kernel client will stop trying to do
> > > > > remote object copies for this fs client and will always use the generic
> > > > > VFS copy_file_range.
> > > > > 
> > > > > Signed-off-by: Luis Henriques <lhenriques@xxxxxxxx>
> > > > > ---
> > > > > Hi Jeff,
> > > > > 
> > > > > This is a follow-up to the discussion in [1].  Since PR [2] has been
> > > > > merged, it's now time to change the kernel client to use the new
> > > > > 'copy-from2'.  And that's what this patch does.
> > > > > 
> > > > > [1] https://lore.kernel.org/lkml/20191118120935.7013-1-lhenriques@xxxxxxxx/
> > > > > [2] https://github.com/ceph/ceph/pull/31728
> > > > > 
> > > > >  fs/ceph/file.c                  | 13 ++++++++++++-
> > > > >  fs/ceph/super.c                 |  1 +
> > > > >  fs/ceph/super.h                 |  3 +++
> > > > >  include/linux/ceph/osd_client.h |  1 +
> > > > >  include/linux/ceph/rados.h      |  2 ++
> > > > >  net/ceph/osd_client.c           | 18 ++++++++++++------
> > > > >  6 files changed, 31 insertions(+), 7 deletions(-)
> > > > > 
> > > > > diff --git a/fs/ceph/file.c b/fs/ceph/file.c
> > > > > index 11929d2bb594..1e6cdf2dfe90 100644
> > > > > --- a/fs/ceph/file.c
> > > > > +++ b/fs/ceph/file.c
> > > > > @@ -1974,6 +1974,10 @@ static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
> > > > >     if (ceph_test_mount_opt(src_fsc, NOCOPYFROM))
> > > > >             return -EOPNOTSUPP;
> > > > > 
> > > > > +   /* Do the OSDs support the 'copy-from2' operation? */
> > > > > +   if (!src_fsc->have_copy_from2)
> > > > > +           return -EOPNOTSUPP;
> > > > > +
> > > > >     /*
> > > > >      * Striped file layouts require that we copy partial objects, but the
> > > > >      * OSD copy-from operation only supports full-object copies.  Limit
> > > > > @@ -2101,8 +2105,15 @@ static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
> > > > >                     CEPH_OSD_OP_FLAG_FADVISE_NOCACHE,
> > > > >                     &dst_oid, &dst_oloc,
> > > > >                     CEPH_OSD_OP_FLAG_FADVISE_SEQUENTIAL |
> > > > > -                   CEPH_OSD_OP_FLAG_FADVISE_DONTNEED, 0);
> > > > > +                   CEPH_OSD_OP_FLAG_FADVISE_DONTNEED,
> > > > > +                   dst_ci->i_truncate_seq, dst_ci->i_truncate_size,
> > > > > +                   CEPH_OSD_COPY_FROM_FLAG_TRUNCATE_SEQ);
> > > > >             if (err) {
> > > > > +                   if (err == -EOPNOTSUPP) {
> > > > > +                           src_fsc->have_copy_from2 = false;
> > > > > +                           pr_notice("OSDs don't support 'copy-from2'; "
> > > > > +                                     "disabling copy_file_range\n");
> > > > > +                   }
> > > > >                     dout("ceph_osdc_copy_from returned %d\n", err);
> > > > >                     if (!ret)
> > > > >                             ret = err;
> > > > 
> > > > The patch itself looks fine to me. I'll not merge yet, since you sent it
> > > > as an RFC, but I don't have any objection to it at first glance.
> > > 
> > > I was going to drop the RFC, but then at the last minute decided to leave.
> > > 
> > > >                                                                    The
> > > > only other comment I'd make is that you should probably split this into
> > > > two patches -- one for the libceph changes and one for cephfs.
> > > 
> > > Hmm... TBH I didn't thought about that, but since the libceph patch would
> > > be changing its API (ceph_osdc_copy_from would have 2 extra parameters), I
> > > don't think that's a good idea.  Bisection would be broken between these 2
> > > patches.
> > 
> 
> In that case, I'll just go ahead and do some testing with this patch and
> will plan to merge it as-is, assuming that goes ok.

Awesome, thanks!

Cheers,
--
Luís