linux-kernel - Re: [PATCH 2/3] nfsd: new tracepoint for check_slot

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Message-ID: <ZhBLBEIgKxChNBAY@tissot.1015granger.net>
Date: Fri, 5 Apr 2024 15:03:32 -0400
From: Chuck Lever <chuck.lever@...cle.com>
To: Jeff Layton <jlayton@...nel.org>
Cc: Neil Brown <neilb@...e.de>, Olga Kornievskaia <kolga@...app.com>,
        Dai Ngo <Dai.Ngo@...cle.com>, Tom Talpey <tom@...pey.com>,
        linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] nfsd: new tracepoint for check_slot_seqid

On Fri, Apr 05, 2024 at 02:40:50PM -0400, Jeff Layton wrote:
> Replace a dprintk in check_slot_seqid with a new tracepoint.  Add a
> nfs4_client argument to check_slot_seqid so that we can pass the
> appropriate info to the tracepoint.
> 
> Signed-off-by: Jeffrey Layton <jlayton@...hat.com>
> ---
>  fs/nfsd/nfs4state.c | 12 ++++++------
>  fs/nfsd/trace.h     | 34 ++++++++++++++++++++++++++++++++++
>  2 files changed, 40 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 3cef81e196c6..5891bc3e2b0b 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -3642,10 +3642,9 @@ nfsd4_exchange_id(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>  }
>  
>  static __be32
> -check_slot_seqid(u32 seqid, u32 slot_seqid, int slot_inuse)
> +check_slot_seqid(struct nfs4_client *clp, u32 seqid, u32 slot_seqid, bool slot_inuse)
>  {
> -	dprintk("%s enter. seqid %d slot_seqid %d\n", __func__, seqid,
> -		slot_seqid);
> +	trace_check_slot_seqid(clp, seqid, slot_seqid, slot_inuse);

Getting rid of the dprintk: +1

Tracing slot seqid checks: +1

But I'd like something a little different for the tracepoint
itself. I can make these changes if you like to just hand this off.

Let's make this trace point into three separate trace events, one
at the nfsd4_sequence check_slot_seqid() call site, and two in
nfsd4_create_session(), like below.

Two reasons for this change:

1. Separate tracepoints in nfsd4_create_session will show whether
   the client is confirmed or not

2. The tracepoint in nfsd4_sequence will normally be noisy, so
   having a separate tracepoint for that case makes it easy to
   disable that one while leaving the create_session tracepoints
   enabled.

And, bonus: you won't have to change the synopsis of
check_slot_seqid().


>  	/* The slot is in use, and no response has been sent. */
>  	if (slot_inuse) {
> @@ -3827,7 +3826,8 @@ nfsd4_create_session(struct svc_rqst *rqstp,
>  		cs_slot = &conf->cl_cs_slot;
		trace_nfsd_slot_seqid_confirmed
>  	else
>  		cs_slot = &unconf->cl_cs_slot;
		trace_nfsd_slot_seqid_unconfirmed
> -	status = check_slot_seqid(cr_ses->seqid, cs_slot->sl_seqid, 0);
> +	status = check_slot_seqid(conf ? conf : unconf, cr_ses->seqid,
> +				  cs_slot->sl_seqid, false);
>  	switch (status) {
>  	case nfs_ok:
>  		cs_slot->sl_seqid++;
> @@ -4221,8 +4221,8 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>  	 * sr_highest_slotid and the sr_target_slot id to maxslots */
>  	seq->maxslots = session->se_fchannel.maxreqs;
>  
	trace_nfsd_slot_seqid_sequence
> -	status = check_slot_seqid(seq->seqid, slot->sl_seqid,
> -					slot->sl_flags & NFSD4_SLOT_INUSE);
> +	status = check_slot_seqid(clp, seq->seqid, slot->sl_seqid,
> +				  slot->sl_flags & NFSD4_SLOT_INUSE);
>  	if (status == nfserr_replay_cache) {
>  		status = nfserr_seq_misordered;
>  		if (!(slot->sl_flags & NFSD4_SLOT_INITIALIZED))
> diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
> index 7f1a6d568bdb..ec00ca7ecfc8 100644
> --- a/fs/nfsd/trace.h
> +++ b/fs/nfsd/trace.h
> @@ -1542,6 +1542,40 @@ TRACE_EVENT(nfsd_cb_seq_status,
>  	)
>  );
>  
> +TRACE_EVENT(check_slot_seqid,

Nit: NFSD tracepoint names should start with "nfsd_".


> +	TP_PROTO(
> +		const struct nfs4_client *clp,
> +		u32 seqid,
> +		u32 slot_seqid,
> +		bool inuse
> +	),
> +	TP_ARGS(clp, seqid, slot_seqid, inuse),
> +	TP_STRUCT__entry(
> +		__field(u32, seqid)
> +		__field(u32, slot_seqid)
> +		__field(u32, cl_boot)
> +		__field(u32, cl_id)
> +		__sockaddr(addr, clp->cl_cb_conn.cb_addrlen)
> +		__field(bool, conf)
> +		__field(bool, inuse)
> +	),
> +	TP_fast_assign(
> +		__entry->cl_boot = clp->cl_clientid.cl_boot;
> +		__entry->cl_id = clp->cl_clientid.cl_id;
> +		__assign_sockaddr(addr, &clp->cl_cb_conn.cb_addr,
> +				  clp->cl_cb_conn.cb_addrlen);
> +		__entry->seqid = seqid;
> +		__entry->slot_seqid = slot_seqid;
> +		__entry->conf = test_bit(NFSD4_CLIENT_CONFIRMED, &clp->cl_flags);
> +		__entry->inuse = inuse;
> +	),
> +	TP_printk("addr=%pISpc %s client %08x:%08x seqid=%u slot_seqid=%u inuse=%d",
> +		__get_sockaddr(addr), __entry->conf ? "conf" : "unconf",
> +		__entry->cl_boot, __entry->cl_id,
> +		__entry->seqid, __entry->slot_seqid, __entry->inuse

Nit: How about: __entry->in_use ? "(in use)" : "(not in use)"

Since TP_printk is for human readers.


> +	)
> +);
> +
>  TRACE_EVENT(nfsd_cb_free_slot,
>  	TP_PROTO(
>  		const struct rpc_task *task,
> 
> -- 
> 2.44.0
> 

-- 
Chuck Lever