Re: [PATCH] nfsd: don't abort copies early

From: Chuck Lever <chuck.lever@oracle.com>
To: Bruce Fields <bfields@fieldses.org>
Cc: Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
	Olga Kornievskaia <kolga@netapp.com>
Subject: Re: [PATCH] nfsd: don't abort copies early
Date: Thu, 25 Feb 2021 15:28:08 +0000	[thread overview]
Message-ID: <CDFF4F84-1A0C-4E4C-A18B-AC39F715E6D8@oracle.com> (raw)
In-Reply-To: <20210224223349.GB25689@fieldses.org>

> On Feb 24, 2021, at 5:33 PM, Bruce Fields <bfields@fieldses.org> wrote:
> 
> On Wed, Feb 24, 2021 at 07:34:10PM +0000, Chuck Lever wrote:
>> 
>> 
>>> On Feb 24, 2021, at 2:31 PM, J. Bruce Fields <bfields@fieldses.org> wrote:
>>> 
>>> I confess I always have to stare at these comparisons for a minute to
>>> figure out which way they should go.  And the logic in each of these
>>> loops is a little repetitive.
>>> 
>>> Would it be worth creating a little state_expired() helper to work out
>>> the comparison and the new timeout?
>> 
>> That's better, but aren't there already operators on time64_t data objects
>> that can be used for this?
> 
> No idea.

I was thinking of jiffies, I guess. time_before() and time_after().

Checking the definition of time64_t, from include/linux/time64.h:

typedef __s64 time64_t;

Signed, hrm. And no comparison helpers.

I might be a little concerned about wrapping time values. But any
concerns can be addressed in the new common helper state_expired(),
possibly as a subsequent patch.

If you feel it's ready, can you send me the below clean-up as an
official patch with description and SoB?

> --b.
> 
>> 
>> 
>>> --b.
>>> 
>>> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
>>> index 61552e89bd89..00fb3603c29e 100644
>>> --- a/fs/nfsd/nfs4state.c
>>> +++ b/fs/nfsd/nfs4state.c
>>> @@ -5363,6 +5363,22 @@ static bool clients_still_reclaiming(struct nfsd_net *nn)
>>> 	return true;
>>> }
>>> 
>>> +struct laundry_time {
>>> +	time64_t cutoff;
>>> +	time64_t new_timeo;
>>> +};
>>> +
>>> +bool state_expired(struct laundry_time *lt, time64_t last_refresh)
>>> +{
>>> +	time64_t time_remaining;
>>> +
>>> +	if (last_refresh > lt->cutoff)
>>> +		return true;
>>> +	time_remaining = lt->cutoff - last_refresh;
>>> +	lt->new_timeo = min(lt->new_timeo, time_remaining);
>>> +	return false;
>>> +}
>>> +
>>> static time64_t
>>> nfs4_laundromat(struct nfsd_net *nn)
>>> {
>>> @@ -5372,14 +5388,16 @@ nfs4_laundromat(struct nfsd_net *nn)
>>> 	struct nfs4_ol_stateid *stp;
>>> 	struct nfsd4_blocked_lock *nbl;
>>> 	struct list_head *pos, *next, reaplist;
>>> -	time64_t cutoff = ktime_get_boottime_seconds() - nn->nfsd4_lease;
>>> -	time64_t t, new_timeo = nn->nfsd4_lease;
>>> +	struct laundry_time lt = {
>>> +		.cutoff = ktime_get_boottime_seconds() - nn->nfsd4_lease,
>>> +		.new_timeo = nn->nfsd4_lease
>>> +	};
>>> 	struct nfs4_cpntf_state *cps;
>>> 	copy_stateid_t *cps_t;
>>> 	int i;
>>> 
>>> 	if (clients_still_reclaiming(nn)) {
>>> -		new_timeo = 0;
>>> +		lt.new_timeo = 0;
>>> 		goto out;
>>> 	}
>>> 	nfsd4_end_grace(nn);
>>> @@ -5389,7 +5407,7 @@ nfs4_laundromat(struct nfsd_net *nn)
>>> 	idr_for_each_entry(&nn->s2s_cp_stateids, cps_t, i) {
>>> 		cps = container_of(cps_t, struct nfs4_cpntf_state, cp_stateid);
>>> 		if (cps->cp_stateid.sc_type == NFS4_COPYNOTIFY_STID &&
>>> -				cps->cpntf_time < cutoff)
>>> +				state_expired(&lt, cps->cpntf_time))
>>> 			_free_cpntf_state_locked(nn, cps);
>>> 	}
>>> 	spin_unlock(&nn->s2s_cp_lock);
>>> @@ -5397,11 +5415,8 @@ nfs4_laundromat(struct nfsd_net *nn)
>>> 	spin_lock(&nn->client_lock);
>>> 	list_for_each_safe(pos, next, &nn->client_lru) {
>>> 		clp = list_entry(pos, struct nfs4_client, cl_lru);
>>> -		if (clp->cl_time > cutoff) {
>>> -			t = clp->cl_time - cutoff;
>>> -			new_timeo = min(new_timeo, t);
>>> +		if (!state_expired(&lt, clp->cl_time))
>>> 			break;
>>> -		}
>>> 		if (mark_client_expired_locked(clp)) {
>>> 			trace_nfsd_clid_expired(&clp->cl_clientid);
>>> 			continue;
>>> @@ -5418,11 +5433,8 @@ nfs4_laundromat(struct nfsd_net *nn)
>>> 	spin_lock(&state_lock);
>>> 	list_for_each_safe(pos, next, &nn->del_recall_lru) {
>>> 		dp = list_entry (pos, struct nfs4_delegation, dl_recall_lru);
>>> -		if (dp->dl_time > cutoff) {
>>> -			t = dp->dl_time - cutoff;
>>> -			new_timeo = min(new_timeo, t);
>>> +		if (!state_expired(&lt, clp->cl_time))
>>> 			break;
>>> -		}
>>> 		WARN_ON(!unhash_delegation_locked(dp));
>>> 		list_add(&dp->dl_recall_lru, &reaplist);
>>> 	}
>>> @@ -5438,11 +5450,8 @@ nfs4_laundromat(struct nfsd_net *nn)
>>> 	while (!list_empty(&nn->close_lru)) {
>>> 		oo = list_first_entry(&nn->close_lru, struct nfs4_openowner,
>>> 					oo_close_lru);
>>> -		if (oo->oo_time > cutoff) {
>>> -			t = oo->oo_time - cutoff;
>>> -			new_timeo = min(new_timeo, t);
>>> +		if (!state_expired(&lt, oo->oo_time))
>>> 			break;
>>> -		}
>>> 		list_del_init(&oo->oo_close_lru);
>>> 		stp = oo->oo_last_closed_stid;
>>> 		oo->oo_last_closed_stid = NULL;
>>> @@ -5468,11 +5477,8 @@ nfs4_laundromat(struct nfsd_net *nn)
>>> 	while (!list_empty(&nn->blocked_locks_lru)) {
>>> 		nbl = list_first_entry(&nn->blocked_locks_lru,
>>> 					struct nfsd4_blocked_lock, nbl_lru);
>>> -		if (nbl->nbl_time > cutoff) {
>>> -			t = nbl->nbl_time - cutoff;
>>> -			new_timeo = min(new_timeo, t);
>>> +		if (!state_expired(&lt, oo->oo_time))
>>> 			break;
>>> -		}
>>> 		list_move(&nbl->nbl_lru, &reaplist);
>>> 		list_del_init(&nbl->nbl_list);
>>> 	}
>>> @@ -5485,8 +5491,7 @@ nfs4_laundromat(struct nfsd_net *nn)
>>> 		free_blocked_lock(nbl);
>>> 	}
>>> out:
>>> -	new_timeo = max_t(time64_t, new_timeo, NFSD_LAUNDROMAT_MINTIMEOUT);
>>> -	return new_timeo;
>>> +	return max_t(time64_t, lt.new_timeo, NFSD_LAUNDROMAT_MINTIMEOUT);
>>> }
>>> 
>>> static struct workqueue_struct *laundry_wq;
>> 
>> --
>> Chuck Lever
>> 
>> 

--
Chuck Lever