linux-kernel - Re: [PATCH net-next 2/7] netconsole: refactor CPU number formatting into separate function

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Message-ID: <20250225140813.GU1615191@kernel.org>
Date: Tue, 25 Feb 2025 14:08:13 +0000
From: Simon Horman <horms@...nel.org>
To: Breno Leitao <leitao@...ian.org>
Cc: Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Jonathan Corbet <corbet@....net>, Shuah Khan <shuah@...nel.org>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org,
	kernel-team@...a.com
Subject: Re: [PATCH net-next 2/7] netconsole: refactor CPU number formatting
 into separate function

On Tue, Feb 25, 2025 at 03:09:20AM -0800, Breno Leitao wrote:
> Hello Simon,
> 
> On Tue, Feb 25, 2025 at 10:17:48AM +0000, Simon Horman wrote:
> > On Fri, Feb 21, 2025 at 05:52:07AM -0800, Breno Leitao wrote:
> > > Extract CPU number formatting logic from prepare_extradata() into a new
> > > append_cpu_nr() function.
> > > 
> > > This refactoring improves code organization by isolating CPU number
> > > formatting into its own function while reducing the complexity of
> > > prepare_extradata().
> > > 
> > > The change prepares the codebase for the upcoming taskname feature by
> > > establishing a consistent pattern for handling sysdata features.
> > > 
> > > The CPU number formatting logic itself remains unchanged; only its
> > > location has moved to improve maintainability.
> > > 
> > > Signed-off-by: Breno Leitao <leitao@...ian.org>
> > > ---
> > >  drivers/net/netconsole.c | 18 +++++++++++-------
> > >  1 file changed, 11 insertions(+), 7 deletions(-)
> > > 
> > > diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
> > > index c086e2fe51f874812379e6f89c421d7d32980f91..26ff2ed4de16bce58e9eeaf8b5b362dfaafaca0a 100644
> > > --- a/drivers/net/netconsole.c
> > > +++ b/drivers/net/netconsole.c
> > > @@ -1117,13 +1117,21 @@ static void populate_configfs_item(struct netconsole_target *nt,
> > >  	init_target_config_group(nt, target_name);
> > >  }
> > >  
> > > +static int append_cpu_nr(struct netconsole_target *nt, int offset)
> > > +{
> > > +	/* Append cpu=%d at extradata_complete after userdata str */
> > > +	return scnprintf(&nt->extradata_complete[offset],
> > > +			 MAX_EXTRADATA_ENTRY_LEN, " cpu=%u\n",
> > > +			 raw_smp_processor_id());
> > > +}
> > > +
> > >  /*
> > >   * prepare_extradata - append sysdata at extradata_complete in runtime
> > >   * @nt: target to send message to
> > >   */
> > >  static int prepare_extradata(struct netconsole_target *nt)
> > >  {
> > > -	int sysdata_len, extradata_len;
> > > +	int extradata_len;
> > >  
> > >  	/* userdata was appended when configfs write helper was called
> > >  	 * by update_userdata().
> > > @@ -1133,12 +1141,8 @@ static int prepare_extradata(struct netconsole_target *nt)
> > >  	if (!(nt->sysdata_fields & SYSDATA_CPU_NR))
> > >  		goto out;
> > >  
> > > -	/* Append cpu=%d at extradata_complete after userdata str */
> > > -	sysdata_len = scnprintf(&nt->extradata_complete[nt->userdata_length],
> > > -				MAX_EXTRADATA_ENTRY_LEN, " cpu=%u\n",
> > > -				raw_smp_processor_id());
> > > -
> > > -	extradata_len += sysdata_len;
> > > +	if (nt->sysdata_fields & SYSDATA_CPU_NR)
> > > +		extradata_len += append_cpu_nr(nt, nt->userdata_length);
> > 
> > Hi Breno,
> > 
> > As this is the only caller of append_cpu_nr() I'm wondering
> > if it would be nicer if nt was the only argument to append_cpu_nr().
> 
> Yes, I can do it. I just kept both functions the same:
> 
>   static int append_taskname(struct netconsole_target *nt, int offset)
>   static int append_cpu_nr(struct netconsole_target *nt, int offset)
> 
> Another option is to use extradata_len as the second argument, instead
> of nt->userdata_length. That might(?) make the code easier to read? it
> would look like the following:
> 
>           extradata_len = nt->userdata_length;
>           if (nt->sysdata_fields & SYSDATA_CPU_NR)
>                   extradata_len += append_cpu_nr(nt, extradata_len);
>           if (nt->sysdata_fields & SYSDATA_TASKNAME)
>                   extradata_len += append_taskname(nt, extradata_len);
> 
> What would you write yourself?

I think that I would reduce the number of parameters of append_cpu_nr() and
append_taskname(). But really, any of the options, including this patch
as-is, are fine. So please chose whichever you think is best.