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Date:   Wed, 27 Apr 2022 14:46:53 -0400
From:   "J. Bruce Fields" <bfields@fieldses.org>
To:     Dai Ngo <dai.ngo@oracle.com>
Cc:     chuck.lever@oracle.com, jlayton@redhat.com,
        viro@zeniv.linux.org.uk, linux-nfs@vger.kernel.org,
        linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH RFC v22 1/7] NFSD: add courteous server support for
 thread with only delegation
Message-ID: <20220427184653.GE13471@fieldses.org>
References: <1651049573-29552-1-git-send-email-dai.ngo@oracle.com>
 <1651049573-29552-2-git-send-email-dai.ngo@oracle.com>
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On Wed, Apr 27, 2022 at 01:52:47AM -0700, Dai Ngo wrote:
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 234e852fcdfa..216bd77a8764 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -125,6 +125,8 @@ static void free_session(struct nfsd4_session *);
>  static const struct nfsd4_callback_ops nfsd4_cb_recall_ops;
>  static const struct nfsd4_callback_ops nfsd4_cb_notify_lock_ops;
>  
> +static struct workqueue_struct *laundry_wq;
> +
>  static bool is_session_dead(struct nfsd4_session *ses)
>  {
>  	return ses->se_flags & NFS4_SESSION_DEAD;
> @@ -152,6 +154,7 @@ static __be32 get_client_locked(struct nfs4_client *clp)
>  	if (is_client_expired(clp))
>  		return nfserr_expired;
>  	atomic_inc(&clp->cl_rpc_users);
> +	clp->cl_state = NFSD4_ACTIVE;
>  	return nfs_ok;
>  }
>  
> @@ -172,6 +175,7 @@ renew_client_locked(struct nfs4_client *clp)
>  
>  	list_move_tail(&clp->cl_lru, &nn->client_lru);
>  	clp->cl_time = ktime_get_boottime_seconds();
> +	clp->cl_state = NFSD4_ACTIVE;
>  }

We shouldn't need that assignment in both places.

The laundromat really shouldn't let a client go to COURTESY while there
are rpc's in process for that client.  So, let's just add that check to
the laundromat (see below), and then the assignment in
renew_client_locked becomes unnecessary.

> +static void
> +nfs4_get_client_reaplist(struct nfsd_net *nn, struct list_head *reaplist,
> +				struct laundry_time *lt)
> +{
> +	struct list_head *pos, *next;
> +	struct nfs4_client *clp;
> +	bool cour;
> +
> +	INIT_LIST_HEAD(reaplist);
> +	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_state == NFSD4_EXPIRABLE)
> +			goto exp_client;
> +		if (!state_expired(lt, clp->cl_time))
> +			break;
> +		if (!client_has_state_tmp(clp))
> +			goto exp_client;
> +		cour = (clp->cl_state == NFSD4_COURTESY);
> +		if (cour && ktime_get_boottime_seconds() >=
> +				(clp->cl_time + NFSD_COURTESY_CLIENT_TIMEOUT)) {
> +			goto exp_client;
> +		}
> +		if (nfs4_anylock_blockers(clp)) {
> +exp_client:
> +			if (mark_client_expired_locked(clp))
> +				continue;
> +			list_add(&clp->cl_lru, reaplist);
> +			continue;
> +		}
> +		if (!cour)
> +			cmpxchg(&clp->cl_state, NFSD4_ACTIVE, NFSD4_COURTESY);

So, as in mark_client_expired_locked, we should only be doing this if
clp_cl_rpc_users is 0.

Also, it should just be a simple assignment, the cmpxchg isn't necessary
here.

--b.