linux-kernel - Re: [PATCH v10 05/30] tracing: Introduce trace remotes

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Message-ID: <aXvThRcUhuBreMPv@google.com>
Date: Thu, 29 Jan 2026 21:39:17 +0000
From: Vincent Donnefort <vdonnefort@...gle.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: mhiramat@...nel.org, mathieu.desnoyers@...icios.com,
	linux-trace-kernel@...r.kernel.org, maz@...nel.org,
	oliver.upton@...ux.dev, joey.gouly@....com, suzuki.poulose@....com,
	yuzenghui@...wei.com, kvmarm@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, jstultz@...gle.com,
	qperret@...gle.com, will@...nel.org, aneesh.kumar@...nel.org,
	kernel-team@...roid.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10 05/30] tracing: Introduce trace remotes

[...]

> > +static ssize_t buffer_size_kb_write(struct file *filp, const char __user *ubuf, size_t cnt,
> > +				    loff_t *ppos)
> > +{
> > +	struct trace_remote *remote = filp->private_data;
> > +	unsigned long val;
> > +	int ret;
> > +
> > +	ret = kstrtoul_from_user(ubuf, cnt, 10, &val);
> > +	if (ret)
> > +		return ret;
> > +
> > +	/* KiB to Bytes */
> > +	if (!val || check_shl_overflow(val, 10, &val))
> > +		return -EINVAL;
> > +
> > +	guard(mutex)(&remote->lock);
> > +
> > +	remote->trace_buffer_size = val;
> 
> Should this be allowed to change when it is already loaded?

It would only be effective on the next unload/load. 

But now thinking more about it, this is probably not clear to a user and
returning -EBUSY when loaded might be a better solution?

> 
> -- Steve
> 
> > +
> > +	return cnt;
> > +}
> > +
> > +static int buffer_size_kb_show(struct seq_file *s, void *unused)
> > +{
> > +	struct trace_remote *remote = s->private;
> > +
> > +	seq_printf(s, "%lu (%s)\n", remote->trace_buffer_size >> 10,
> > +		   trace_remote_loaded(remote) ? "loaded" : "unloaded");
> > +
> > +	return 0;
> > +}
> > +DEFINE_SHOW_STORE_ATTRIBUTE(buffer_size_kb);
> > +
>