linux-kernel - Re: [PATCH v12 01/16] tracing: Use str_has_prefix() in synth_event

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Message-ID: <7c07519607d08c0afe448a03fb2010bce13cd77f.camel@perches.com>
Date:   Tue, 15 Jan 2019 20:59:16 -0800
From:   Joe Perches <joe@...ches.com>
To:     Tom Zanussi <zanussi@...nel.org>, rostedt@...dmis.org
Cc:     tglx@...utronix.de, mhiramat@...nel.org, namhyung@...nel.org,
        vedang.patel@...el.com, bigeasy@...utronix.de,
        joel@...lfernandes.org, mathieu.desnoyers@...icios.com,
        julia@...com, linux-kernel@...r.kernel.org,
        linux-rt-users@...r.kernel.org
Subject: Re: [PATCH v12 01/16] tracing: Use str_has_prefix() in
 synth_event_create()

On Tue, 2019-01-15 at 16:05 -0600, Tom Zanussi wrote:
> Since we now have a str_has_prefix() that returns the length, we can
> use that instead of explicitly calculating it.
[]
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
[]
> @@ -1200,8 +1200,7 @@ static int synth_event_create(int argc, const char **argv)
>  
>  	/* This interface accepts group name prefix */
>  	if (strchr(name, '/')) {
> -		len = sizeof(SYNTH_SYSTEM "/") - 1;
> -		if (strncmp(name, SYNTH_SYSTEM "/", len))
> +		if ((len = str_has_prefix(name, SYNTH_SYSTEM "/")) == 0)

Since this is a single test, and not multiple if/else if
blocks, I believe this would read better on two lines

		len = str_has_prefix(name, SYNTH_SYSTEM "/");
		if (len == 0)

>  			return -EINVAL;
>  		name += len;
>  	}