Re: [PATCH v4 1/1] NFSv4.2: Fix NFS4ERR_STALE error when doing inter server copy

["J. Bruce Fields" <bfields@fieldses.org>]

On Wed, Nov 11, 2020 at 03:02:19PM -0800, Dai Ngo wrote:
> 
> On 11/10/20 2:21 PM, J. Bruce Fields wrote:
> >On Tue, Nov 10, 2020 at 05:08:59PM -0500, Olga Kornievskaia wrote:
> >>On Tue, Nov 10, 2020 at 4:52 PM J. Bruce Fields <bfields@fieldses.org> wrote:
> >>>On Tue, Nov 10, 2020 at 04:07:41PM -0500, Olga Kornievskaia wrote:
> >>>>On Tue, Nov 10, 2020 at 3:14 PM J. Bruce Fields <bfields@fieldses.org> wrote:
> >>>>>On Mon, Nov 09, 2020 at 10:46:12PM -0800, Dai Ngo wrote:
> >>>>>>On 11/9/20 2:26 PM, Dai Ngo wrote:
> >>>>>>>On 11/9/20 12:42 PM, J. Bruce Fields wrote:
> >>>>>>>>On Mon, Nov 09, 2020 at 11:34:08AM -0800, Dai Ngo wrote:
> >>>>>>>>>On 11/9/20 10:30 AM, J. Bruce Fields wrote:
> >>>>>>>>>>On Tue, Oct 20, 2020 at 11:34:35AM -0700, Dai Ngo wrote:
> >>>>>>>>>>>On 10/20/20 10:01 AM, J. Bruce Fields wrote:
> >>>>>>>>>>>>On Sun, Oct 18, 2020 at 11:42:49PM -0400, Dai Ngo wrote:
> >>>>>>>>>>>>>NFS_FS=y as dependency of CONFIG_NFSD_V4_2_INTER_SSC still have
> >>>>>>>>>>>>>build errors and some configs with NFSD=m to get NFS4ERR_STALE
> >>>>>>>>>>>>>error when doing inter server copy.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>Added ops table in nfs_common for knfsd to access NFS
> >>>>>>>>>>>>>client modules.
> >>>>>>>>>>>>OK, looks reasonable to me, applying.  Does this resolve all the
> >>>>>>>>>>>>problems you've seen, or is there any bad case left?
> >>>>>>>>>>>Thanks Bruce.
> >>>>>>>>>>>
> >>>>>>>>>>>With this patch, I no longer see the NFS4ERR_STALE in any config.
> >>>>>>>>>>>
> >>>>>>>>>>>The problem with NFS4ERR_STALE was because of a bug in
> >>>>>>>>>>>nfs42_ssc_open.
> >>>>>>>>>>>When CONFIG_NFSD_V4_2_INTER_SSC is not defined, nfs42_ssc_open
> >>>>>>>>>>>returns NULL which is incorrect allowing the operation to continue
> >>>>>>>>>>>until nfsd4_putfh which does not have the code to handle
> >>>>>>>>>>>nfserr_stale.
> >>>>>>>>>>>
> >>>>>>>>>>>With this patch, when CONFIG_NFSD_V4_2_INTER_SSC is not defined the
> >>>>>>>>>>>new nfs42_ssc_open returns ERR_PTR(-EIO) which causes the NFS client
> >>>>>>>>>>>to switch over to the split copying (read src and write to dst).
> >>>>>>>>>>That sounds reasonable, but I don't see any of the patches you've sent
> >>>>>>>>>>changing that error return.  Did I overlook something, or did you mean
> >>>>>>>>>>to append a patch to this message?
> >>>>>>>>>Since with the patch, I did not run into the condition where
> >>>>>>>>>NFS4ERR_STALE
> >>>>>>>>>is returned so I did not fix this return error code. Do you want me to
> >>>>>>>>>submit another patch to change the returned error code from
> >>>>>>>>>NFS4ERR_STALE
> >>>>>>>>>to NFS4ERR_NOTSUPP if it ever runs into that condition?
> >>>>>>>>That would be great, thanks.  (I mean, it is still possible to hit that
> >>>>>>>>case, right?  You just didn't test with !CONFIG_NFSD_V4_2_INTER_SSC ?)
> >>>>>>>will do. I did tested with (!CONFIG_NFSD_V4_2_INTER_SSC) but did not hit
> >>>>>>>this case.
> >>>>>>I need to qualify this, the copy_file_range syscall did not return
> >>>>>>ESTALE in the test.
> >>>>>>
> >>>>>>>Because with this patch, when CONFIG_NFSD_V4_2_INTER_SSC is not
> >>>>>>>defined the new nfs42_ssc_open returns ERR_PTR(-EIO), instead of NULL in
> >>>>>>>the old code, which causes the NFS client to switch over to the split
> >>>>>>>copying (read src and write to dst).
> >>>>>>This is not the reason why the client switches to generic_copy_file_range.
> >>>>>>
> >>>>>>>Returning NULL in the old nfs42_ssc_open is not correct, it allows
> >>>>>>>the copy
> >>>>>>>operation to proceed and hits the NFS4ERR_STALE case in the COPY
> >>>>>>>operation.
> >>>>>>I retested with (!CONFIG_NFSD_V4_2_INTER_SSC) and saw NFS4ERR_STALE
> >>>>>>returned for the PUTFH of the SRC in the COPY compound. However on the
> >>>>>>client nfs42_proc_copy (with commit 7e350197a1c10) replaced the ESTALE
> >>>>>>with EOPNOTSUPP causing nfs4_copy_file_range to use generic_copy_file_range
> >>>>>>to do the copy.
> >>>>>>
> >>>>>>The ESTALE error is only returned by copy_file_range if the client
> >>>>>>does not have commit 7e350197a1c10. So I think there is no need to
> >>>>>>make any change on the source server for the NFS4ERR_STALE error.
> >>>>>I don't believe NFS4ERR_STALE is the correct error for the server to
> >>>>>return.  It's nice that the client is able to do the right thing despite
> >>>>>the server returning the wrong error, but we should still try to get
> >>>>>this right on the server.
> >>>>Hi Bruce,
> >>>>
> >>>>ERR_STALE is the appropriate error to be returned by the server that
> >>>>gets a COPY compound when it doesn't support COPY. Since server can't
> >>>>understand the filehandle so it can't process it so we can't get to
> >>>>processing COPY opcode where the server could have returned
> >>>>EOPNOTSUPP.
> >>>The case we're discussing is the case where we support COPY but not
> >>>server-to-server copy.
> >>My point is still the same, that's an appropriate error for when
> >>server-to-server copy is not supported.
> >Uh, OK, if it backs up and returns it to the PUTFH, I guess?
> >
> >Was it really the intention of nfsd4_do_async_copy() that it return
> >STALE in the case NFS42_ssc_open() returns NULL?  That's pretty
> >confusing.
> 
> In this scenario, the COPY compound fails at the PUTFH op and
> NFS4ERR_NOTSUPP is not a valid error code for PUTFH, NFS4ERR_STALE is.

OK, makes sense.

I've lost track of what's left to apply.

--b.