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

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

> On Dec 8, 2021, at 10:54 AM, Dai Ngo <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_CLIENT, &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?

I'm still interested, but Bruce should chime in.

Maybe Calum could have a look under the covers of pynfs and see how difficult the change might be.


--
Chuck Lever