FreeBSD NFS client goes into infinite retry loop

[Steve Polyack]

On 03/22/10 10:52, Steve Polyack wrote:
> On 3/19/2010 11:27 PM, Rick Macklem wrote:
>> On Fri, 19 Mar 2010, Steve Polyack wrote:
>>
>> [good stuff snipped]
>>>
>>> This makes sense.  According to wireshark, the server is indeed 
>>> transmitting "Status: NFS3ERR_IO (5)".  Perhaps this should be STALE 
>>> instead; it sounds more correct than marking it a general IO error.  
>>> Also, the NFS server is serving its share off of a ZFS filesystem, 
>>> if it makes any difference.  I suppose ZFS could be talking to the 
>>> NFS server threads with some mismatched language, but I doubt it.
>>>
>> Ok, now I think we're making progress. If VFS_FHTOVP() doesn't return
>> ESTALE when the file no longer exists, the NFS server returns whatever
>> error it has returned.
>>
>> So, either VFS_FHTOVP() succeeds after the file has been deleted, which
>> would be a problem that needs to be fixed within ZFS
>> OR
>> ZFS returns an error other than ESTALE when it doesn't exist.
>>
>> Try the following patch on the server (which just makes any error
>> returned by VFS_FHTOVP() into ESTALE) and see if that helps.
>>
>> --- nfsserver/nfs_srvsubs.c.sav    2010-03-19 22:06:43.000000000 -0400
>> +++ nfsserver/nfs_srvsubs.c    2010-03-19 22:07:22.000000000 -0400
>> @@ -1127,6 +1127,8 @@
>>          }
>>      }
>>      error = VFS_FHTOVP(mp, &fhp->fh_fid, vpp);
>> +    if (error != 0)
>> +        error = ESTALE;
>>      vfs_unbusy(mp);
>>      if (error)
>>          goto out;
>>
>> Please let me know if the patch helps, rick
>>
>>
> The patch seems to fix the bad behavior.  Running with the patch, I 
> see the following output from my patch (return code of nfs_doio from 
> within nfsiod):
> nfssvc_iod: iod 0 nfs_doio returned errno: 70
>
> Furthermore, when inspecting the transaction with Wireshark, after 
> deleting the file on the NFS server it looks like there is only a 
> single error.  This time there it is a reply to a V3 Lookup call that 
> contains a status of "NFS3ERR_NOENT (2)" coming from the NFS server.  
> The client also does not repeatedly try to complete the failed request.
>
> Any suggestions on the next step here?  Based on what you said it 
> looks like ZFS is falsely reporting an IO error to VFS instead of 
> ESTALE / NOENT.  I tried looking around zfs_fhtovp() and only saw 
> returns of EINVAL, but I'm not even sure I'm looking in the right place.

Further on down the rabbit hole... here's the piece in zfs_fhtovp() 
where it's kicking out EINVAL instead of ESTALE - the following patch 
corrects the behavior, but of course also suggests further digging 
within the zfs_zget() function to ensure that _it_ is returning the 
correct thing and whether or not it needs to be handled there or within 
zfs_fhtovp().

--- 
src-orig/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c    
2010-03-22 11:41:21.000000000 -0400
+++ src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c    
2010-03-22 16:25:21.000000000 -0400
@@ -1246,7 +1246,7 @@
      dprintf("getting %llu [%u mask %llx]\n", object, fid_gen, gen_mask);
      if (err = zfs_zget(zfsvfs, object, &zp)) {
          ZFS_EXIT(zfsvfs);
-        return (err);
+        return (ESTALE);
      }
      zp_gen = zp->z_phys->zp_gen & gen_mask;
      if (zp_gen == 0)