Re: [PATCH v2 2/2] lockd: while grace prefer to fail with nlm_lck_denied_grace_period

[Chuck Lever <chuck.lever@oracle.com>]

On 8/21/25 9:56 AM, Olga Kornievskaia wrote:
> On Wed, Aug 20, 2025 at 7:15 PM NeilBrown <neil@brown.name> wrote:
>>
>> On Thu, 14 Aug 2025, Olga Kornievskaia wrote:
>>> On Tue, Aug 12, 2025 at 8:05 PM NeilBrown <neil@brown.name> wrote:
>>>>
>>>> On Wed, 13 Aug 2025, Olga Kornievskaia wrote:
>>>>> When nfsd is in grace and receives an NLM LOCK request which turns
>>>>> out to have a conflicting delegation, return that the server is in
>>>>> grace.
>>>>>
>>>>> Reviewed-by: Jeff Layton <jlayton@redhat.com>
>>>>> Signed-off-by: Olga Kornievskaia <okorniev@redhat.com>
>>>>> ---
>>>>>  fs/lockd/svc4proc.c | 15 +++++++++++++--
>>>>>  1 file changed, 13 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/fs/lockd/svc4proc.c b/fs/lockd/svc4proc.c
>>>>> index 109e5caae8c7..7ac4af5c9875 100644
>>>>> --- a/fs/lockd/svc4proc.c
>>>>> +++ b/fs/lockd/svc4proc.c
>>>>> @@ -141,8 +141,19 @@ __nlm4svc_proc_lock(struct svc_rqst *rqstp, struct nlm_res *resp)
>>>>>       resp->cookie = argp->cookie;
>>>>>
>>>>>       /* Obtain client and file */
>>>>> -     if ((resp->status = nlm4svc_retrieve_args(rqstp, argp, &host, &file)))
>>>>> -             return resp->status == nlm_drop_reply ? rpc_drop_reply :rpc_success;
>>>>> +     resp->status = nlm4svc_retrieve_args(rqstp, argp, &host, &file);
>>>>> +     switch (resp->status) {
>>>>> +     case 0:
>>>>> +             break;
>>>>> +     case nlm_drop_reply:
>>>>> +             if (locks_in_grace(SVC_NET(rqstp))) {
>>>>> +                     resp->status = nlm_lck_denied_grace_period;
>>>>
>>>> I think this is wrong.  If the lock request has the "reclaim" flag set,
>>>> then nlm_lck_denied_grace_period is not a meaningful error.
>>>> nlm4svc_retrieve_args() returns nlm_drop_reply when there is a delay
>>>> getting a response to an upcall to mountd.  For NLM the request really
>>>> must be dropped.
>>>
>>> Thank you for pointing out this case so we are suggesting to.
>>>
>>> if (locks_in_grace(SVC_NET(rqstp)) && !argp->reclaim)
>>>
>>> However, I've been looking and looking but I cannot figure out how
>>> nlm4svc_retrieve_args() would ever get nlm_drop_reply. You say it can
>>> happen during the upcall to mountd. So that happens within nfsd_open()
>>> call and a part of fh_verify().
>>> To return nlm_drop_reply, nlm_fopen() must have gotten nfserr_dropit
>>> from the nfsd_open().  I have searched and searched but I don't see
>>> anything that ever sets nfserr_dropit (NFSERR_DROPIT).
>>>
>>> I searched the logs and nfserr_dropit was an error that was EAGAIN
>>> translated into but then removed by the following patch.
>>
>> Oh.  I didn't know that.
>> We now use RQ_DROPME instead.
>> I guess we should remove NFSERR_DROPIT completely as it not used at all
>> any more.
>>
>> Though returning nfserr_jukebox to an v2 client isn't a good idea....
> 
> I'll take your word for you.
> 
>> So I guess my main complaint isn't valid, but I still don't like this
>> patch.  It seems an untidy place to put the locks_in_grace test.
>> Other callers of nlm4svc_retrieve_args() check locks_in_grace() before
>> making that call.  __nlm4svc_proc_lock probably should too.  Or is there
>> a reason that it is delayed until the middle of nlmsvc_lock()..
> 
> I thought the same about why not adding the in_grace check and decided
> that it was probably because you dont want to deny a lock if there are
> no conflicts. If we add it, somebody might notice and will complain
> that they can't get their lock when there are no conflicts.
> 
>> The patch is not needed and isn't clearly an improvement, so I would
>> rather it were dropped.
> 
> I'm not against dropping this patch if the conclusion is that dropping
> the packet is no worse than returning in_grace error.

I dropped both of these from nfsd-testing. If a fix is still needed,
let's start again with fresh patches.


>> Thanks,
>> NeilBrown
>>
>>
>>>
>>> commit 062304a815fe10068c478a4a3f28cf091c55cb82
>>> Author: J. Bruce Fields <bfields@fieldses.org>
>>> Date:   Sun Jan 2 22:05:33 2011 -0500
>>>
>>>     nfsd: stop translating EAGAIN to nfserr_dropit
>>>
>>> diff --git a/fs/nfsd/nfsproc.c b/fs/nfsd/nfsproc.c
>>> index dc9c2e3fd1b8..fd608a27a8d5 100644
>>> --- a/fs/nfsd/nfsproc.c
>>> +++ b/fs/nfsd/nfsproc.c
>>> @@ -735,7 +735,8 @@ nfserrno (int errno)
>>>                 { nfserr_stale, -ESTALE },
>>>                 { nfserr_jukebox, -ETIMEDOUT },
>>>                 { nfserr_jukebox, -ERESTARTSYS },
>>> -               { nfserr_dropit, -EAGAIN },
>>> +               { nfserr_jukebox, -EAGAIN },
>>> +               { nfserr_jukebox, -EWOULDBLOCK },
>>>                 { nfserr_jukebox, -ENOMEM },
>>>                 { nfserr_badname, -ESRCH },
>>>                 { nfserr_io, -ETXTBSY },
>>>
>>> so if fh_verify is failing whatever it is returning, it is not
>>> nfserr_dropit nor is it nfserr_jukebox which means nlm_fopen() would
>>> translate it to nlm_failed which with my patch would not trigger
>>> nlm_lck_denied_grace_period error but resp->status would be set to
>>> nlm_failed.
>>>
>>> So I circle back to I hope that convinces you that we don't need a
>>> check for the reclaim lock.
>>>
>>> I believe nlm_drop_reply is nfsd_open's jukebox error, one of which is
>>> delegation recall. it can be a memory failure. But I'm sure when
>>> EWOULDBLOCK occurs.
>>>
>>>> At the very least we need to guard against the reclaim flag being set in
>>>> the above test.  But I would much rather a more clear distinction were
>>>> made between "drop because of a conflicting delegation" and "drop
>>>> because of a delay getting upcall response".
>>>> Maybe a new "nlm_conflicting_delegtion" return from ->fopen which nlm4
>>>> (and ideally nlm2) handles appropriately.
>>>
>>>
>>>> NeilBrown
>>>>
>>>>
>>>>> +                     return rpc_success;
>>>>> +             }
>>>>> +             return nlm_drop_reply;
>>>>> +     default:
>>>>> +             return rpc_success;
>>>>> +     }
>>>>>
>>>>>       /* Now try to lock the file */
>>>>>       resp->status = nlmsvc_lock(rqstp, file, host, &argp->lock,
>>>>> --
>>>>> 2.47.1
>>>>>
>>>>>
>>>>
>>>>
>>>
>>


-- 
Chuck Lever