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Date: Wed, 27 Mar 2024 12:05:39 -0400
From: Chuck Lever <chuck.lever@oracle.com>
To: Chen Hanxiao <chenhx.fnst@fujitsu.com>
Cc: Jeff Layton <jlayton@kernel.org>, Neil Brown <neilb@suse.de>,
        Olga Kornievskaia <kolga@netapp.com>, Dai Ngo <Dai.Ngo@oracle.com>,
        Tom Talpey <tom@talpey.com>, linux-nfs@vger.kernel.org
Subject: Re: [PATCH] NFSD: trace export root filehandle event
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References: <20240327152737.1411-1-chenhx.fnst@fujitsu.com>
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On Wed, Mar 27, 2024 at 11:27:37PM +0800, Chen Hanxiao wrote:
> Add a tracepoint for obtaining root filehandle event
> 
> Signed-off-by: Chen Hanxiao <chenhx.fnst@fujitsu.com>
> ---
>  fs/nfsd/export.c |  4 +---
>  fs/nfsd/trace.h  | 39 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 40 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
> index 7b641095a665..690721ba42f3 100644
> --- a/fs/nfsd/export.c
> +++ b/fs/nfsd/export.c
> @@ -1027,15 +1027,13 @@ exp_rootfh(struct net *net, struct auth_domain *clp, char *name,
>  	}
>  	inode = d_inode(path.dentry);
>  
> -	dprintk("nfsd: exp_rootfh(%s [%p] %s:%s/%ld)\n",
> -		 name, path.dentry, clp->name,
> -		 inode->i_sb->s_id, inode->i_ino);
>  	exp = exp_parent(cd, clp, &path);
>  	if (IS_ERR(exp)) {
>  		err = PTR_ERR(exp);
>  		goto out;
>  	}
>  
> +	trace_nfsd_exp_rootfh(name, path.dentry, clp->name, inode, exp);

Converting the above dprintk to a tracepoint seems sensible.

I'd like to hear comments from others about whether the new
tracepoint records a useful set of information. We don't need to
record the memory address of the dentry, for example. Recording the
net namespace might be useful, though.


>  	/*
>  	 * fh must be initialized before calling fh_compose
>  	 */
> diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
> index 1cd2076210b1..a11b348f5d6d 100644
> --- a/fs/nfsd/trace.h
> +++ b/fs/nfsd/trace.h
> @@ -396,6 +396,45 @@ TRACE_EVENT(nfsd_export_update,
>  	)
>  );
>  
> +TRACE_EVENT(nfsd_exp_rootfh,
> +	TP_PROTO(
> +		const char *name,
> +		const struct dentry *dentry,
> +		const char *clp_name,
> +		const struct inode *inode,
> +		struct svc_export *exp
> +		),
> +	TP_ARGS(name, dentry, clp_name, inode, exp),
> +	TP_STRUCT__entry(
> +		__string(name, name)
> +		__field(const void *, dentry)
> +		__string(clp_name, clp_name)
> +		__string(s_id, inode->i_sb->s_id)
> +		__field(unsigned long, i_ino)
> +		__array(unsigned char, uuid, 16)
> +		__field(const void *, ex_uuid)
> +	),
> +	TP_fast_assign(
> +		__assign_str(name, name);
> +		__entry->dentry = dentry;
> +		__assign_str(clp_name, clp_name);
> +		__assign_str(s_id, inode->i_sb->s_id);
> +		__entry->i_ino = inode->i_ino;
> +		__entry->ex_uuid = exp->ex_uuid;
> +		if (exp->ex_uuid)
> +			memcpy(__entry->uuid, exp->ex_uuid, 16);
> +	),
> +	TP_printk(
> +		"path=%s dentry=%p domain=%s sid=%s/inode=%ld uuid=%s",
> +		__get_str(name),
> +		__entry->dentry,
> +		__get_str(clp_name),
> +		__get_str(s_id),
> +		__entry->i_ino,
> +		__entry->ex_uuid ? __print_hex_str(__entry->uuid, 16) : "NULL"
> +	)
> +);
> +
>  DECLARE_EVENT_CLASS(nfsd_io_class,
>  	TP_PROTO(struct svc_rqst *rqstp,
>  		 struct svc_fh	*fhp,
> -- 
> 2.39.1
> 

-- 
Chuck Lever