Re: nfs generic/373 failure after "fs: allow cross-vfsmount reflink/dedupe"

[Josef Bacik <josef@toxicpanda.com>]

On Wed, Mar 02, 2022 at 05:42:50PM -0500, J. Bruce Fields wrote:
> On Wed, Mar 02, 2022 at 05:26:08PM -0500, Josef Bacik wrote:
> > On Wed, Mar 02, 2022 at 05:04:50PM -0500, J. Bruce Fields wrote:
> > > I started seeing generic/373 fail on recent linux-next in NFS testing.
> > > 
> > > Bisect lands it on aaf40970b1d0 "fs: allow cross-vfsmount
> > > reflink/dedupe".
> > > 
> > > The test fails because a clone between two mounts is expected to fail,
> > > and no longer does.
> > > 
> > > In my setup both mounts are nfs mounts.  They are mounts of different
> > > exports, and the exports are exports of different filesystems.  So it
> > > does make sense that the clone should fail.
> > > 
> > > I see the NFS client send a CLONE rpc to the server, and the server
> > > return success.  That seems wrong.
> > > 
> > > Both exported filesystems are xfs, and from the code it looks like the
> > > server calls vfs_clone_file_range(), which ends up calling
> > > xfs_file_remap_range().
> > > 
> > > Are we missing a check now in that xfs case?
> > > 
> > > I haven't looked any more closely at what's going on, so I could be
> > > missing something.
> > > 
> > 
> > Yeah there's a few fstests that test this functionality that need to be removed,
> > I have patches pending for this in our fstests staging tree (since we run
> > fstests nightly on our tree)
> > 
> > https://github.com/btrfs/fstests/tree/staging
> > 
> > Right now the patches just remove the tests from auto since that's what we run,
> > I'll remove them properly once the patch lands in linus.  Thanks,
> 
> So, out of curiosity, what is xfs doing in this case?  These are two
> filesystems on separate partitions, is it falling back on a read/write
> loop or something?

I don't think so?  I'm actually kind of confused, because nfsd does
vfs_clone_file_range, and the only place I messed with for CLONE was
ioctl_clone_file, so the patch changed literally nothing, unless you aren't
using nfsd for the server?

And if they are in fact two different file systems the i_sb != i_sb of the
files, so there's something pretty strange going on here, my patch shouldn't
affect your setup.  Thanks,

Josef