Re: [PATCH RFC v6 2/2] nfsd: Initial implementation of NFSv4 Courteous Server

[dai.ngo@oracle.com]

On 12/8/21 8:39 AM, bfields@fieldses.org wrote:
> On Wed, Dec 08, 2021 at 08:25:28AM -0800, dai.ngo@oracle.com wrote:
>> On 12/8/21 8:16 AM, Trond Myklebust wrote:
>>> On Wed, 2021-12-08 at 07:54 -0800, dai.ngo@oracle.com wrote:
>>>> On 12/6/21 11:55 AM, Chuck Lever III wrote:
>>>>
>>>>>> +
>>>>>> +/*
>>>>>> + * Function to check if the nfserr_share_denied error for 'fp'
>>>>>> resulted
>>>>>> + * from conflict with courtesy clients then release their state to
>>>>>> resolve
>>>>>> + * the conflict.
>>>>>> + *
>>>>>> + * Function returns:
>>>>>> + *      0 -  no conflict with courtesy clients
>>>>>> + *     >0 -  conflict with courtesy clients resolved, try
>>>>>> access/deny check again
>>>>>> + *     -1 -  conflict with courtesy clients being resolved in
>>>>>> background
>>>>>> + *            return nfserr_jukebox to NFS client
>>>>>> + */
>>>>>> +static int
>>>>>> +nfs4_destroy_clnts_with_sresv_conflict(struct svc_rqst *rqstp,
>>>>>> +                       struct nfs4_file *fp, struct
>>>>>> nfs4_ol_stateid *stp,
>>>>>> +                       u32 access, bool share_access)
>>>>>> +{
>>>>>> +       int cnt = 0;
>>>>>> +       int async_cnt = 0;
>>>>>> +       bool no_retry = false;
>>>>>> +       struct nfs4_client *cl;
>>>>>> +       struct list_head *pos, *next, reaplist;
>>>>>> +       struct nfsd_net *nn = net_generic(SVC_NET(rqstp),
>>>>>> nfsd_net_id);
>>>>>> +
>>>>>> +       INIT_LIST_HEAD(&reaplist);
>>>>>> +       spin_lock(&nn->client_lock);
>>>>>> +       list_for_each_safe(pos, next, &nn->client_lru) {
>>>>>> +               cl = list_entry(pos, struct nfs4_client, cl_lru);
>>>>>> +               /*
>>>>>> +                * check all nfs4_ol_stateid of this client
>>>>>> +                * for conflicts with 'access'mode.
>>>>>> +                */
>>>>>> +               if (nfs4_check_deny_bmap(cl, fp, stp, access,
>>>>>> share_access)) {
>>>>>> +                       if (!test_bit(NFSD4_COURTESY_CLIENT, &cl-
>>>>>>> cl_flags)) {
>>>>>> +                               /* conflict with non-courtesy
>>>>>> client */
>>>>>> +                               no_retry = true;
>>>>>> +                               cnt = 0;
>>>>>> +                               goto out;
>>>>>> +                       }
>>>>>> +                       /*
>>>>>> +                        * if too many to resolve synchronously
>>>>>> +                        * then do the rest in background
>>>>>> +                        */
>>>>>> +                       if (cnt > 100) {
>>>>>> +                               set_bit(NFSD4_DESTROY_COURTESY_CLIE
>>>>>> NT, &cl->cl_flags);
>>>>>> +                               async_cnt++;
>>>>>> +                               continue;
>>>>>> +                       }
>>>>>> +                       if (mark_client_expired_locked(cl))
>>>>>> +                               continue;
>>>>>> +                       cnt++;
>>>>>> +                       list_add(&cl->cl_lru, &reaplist);
>>>>>> +               }
>>>>>> +       }
>>>>> Bruce suggested simply returning NFS4ERR_DELAY for all cases.
>>>>> That would simplify this quite a bit for what is a rare edge
>>>>> case.
>>>> If we always do this asynchronously by returning NFS4ERR_DELAY
>>>> for all cases then the following pynfs tests need to be modified
>>>> to handle the error:
>>>>
>>>> RENEW3   st_renew.testExpired                                     :
>>>> FAILURE
>>>> LKU10    st_locku.testTimedoutUnlock                              :
>>>> FAILURE
>>>> CLOSE9   st_close.testTimedoutClose2                              :
>>>> FAILURE
>>>>
>>>> and any new tests that opens file have to be prepared to handle
>>>> NFS4ERR_DELAY due to the lack of destroy_clientid in 4.0.
>>>>
>>>> Do we still want to take this approach?
>>> NFS4ERR_DELAY is a valid error for both CLOSE and LOCKU (see RFC7530
>>> section 13.2 https://urldefense.com/v3/__https://datatracker.ietf.org/doc/html/rfc7530*section-13.2__;Iw!!ACWV5N9M2RV99hQ!f8vZHAJophxXdSSJvnxDCSBSRpWFxEOZBo2ZLvjPzXLVrvMYR8RKcc0_Jvjhng$
>>> ) so if pynfs complains, then it needs fixing regardless.
>>>
>>> RENEW, on the other hand, cannot return NFS4ERR_DELAY, but why would it
>>> need to? Either the lease is still valid, or else someone is already
>>> trying to tear it down due to an expiration event. I don't see why
>>> courtesy locks need to add any further complexity to that test.
>> RENEW fails in the 2nd open:
>>
>>      c.create_confirm(t.word(), access=OPEN4_SHARE_ACCESS_BOTH,
>>                       deny=OPEN4_SHARE_DENY_BOTH)     <<======   DENY_BOTH
>>      sleeptime = c.getLeaseTime() * 2
>>      env.sleep(sleeptime)
>>      c2 = env.c2
>>      c2.init_connection()
>>      c2.open_confirm(t.word(), access=OPEN4_SHARE_ACCESS_READ,    <<=== needs to handle NFS4ERR_DELAY
>>                      deny=OPEN4_SHARE_DENY_NONE)
>>
>> CLOSE and LOCKU also fail in the OPEN, similar to the RENEW test.
>> Any new pynfs 4.0 test that does open might get NFS4ERR_DELAY.
> So it's a RENEW test, not the RENEW operation.
>
> A general-purpose client always has to be prepared for DELAY on OPEN.
> But pynfs isn't a general-purpose client, and it assumes that it's the
> only one touching the files and directories it creates.
>
> Within pynfs we've got a problem that the tests don't necessarily clean
> up after themselves completely, so in theory a test could interfere with
> later results.
>
> But each test uses its own files--e.g. in the fragment above note that
> the file it's testing gets the name t.word(), which is by design unique
> to that test.  So it shouldn't be hitting any conflicts with state held
> by previous tests.  Am I missing something?

Both calls, c.create_confirm and c2.open_confirm, use the same file name
t.word().

However, it's strange that if I run RENEW3 by itself then it passes.
 From the network trace, env.c2/c2.init_connection generates a SETCLIENTID
which might get rid off all the states of the previous client since
they're the same.

I will investigate why it fails when running 'all' with NFS4ERR_DELAY.

Do you know if there is an option to specify a list of tests to run,
instead of 'all'?

-Dai