linux-kernel - Re: [PATCH 10/23] perf tools: Introduce swap

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Date:	Mon, 22 Jul 2013 15:44:34 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	linux-kernel@...r.kernel.org,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>, Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Andi Kleen <ak@...ux.intel.com>,
	David Ahern <dsahern@...il.com>
Subject: Re: [PATCH 10/23] perf tools: Introduce swap_header function

On Fri, Jul 19, 2013 at 08:33:37PM +0900, Namhyung Kim wrote:
> On Wed, 17 Jul 2013 19:49:50 +0200, Jiri Olsa wrote:
> > Introducing swap_header function to make the swapping
> > code more clear and extensible.
> 
> [SNIP]
> >  
> > +static int swap_header(struct perf_file_header *header)
> > +{
> > +	mem_bswap_64(header, offsetof(struct perf_file_header, adds_features));
> > +
> > +	if (header->size != sizeof(*header)) {
> > +		/* Support the previous format */
> > +		if (header->size == offsetof(typeof(*header), adds_features))
> > +			bitmap_zero(header->adds_features, HEADER_FEAT_BITS);
> > +		else
> > +			return -1;
> > +	} else
> > +		swap_features(header->adds_features);
> > +
> > +	return 0;
> > +}
> > +
> >  int perf_file_header__read(struct perf_file_header *header,
> >  			   struct perf_header *ph, int fd)
> >  {
> > @@ -2562,19 +2578,8 @@ int perf_file_header__read(struct perf_file_header *header,
> >  		return -1;
> >  	}
> >  
> > -	if (ph->needs_swap) {
> > -		mem_bswap_64(header, offsetof(struct perf_file_header,
> > -			     adds_features));
> > -	}
> > -
> > -	if (header->size != sizeof(*header)) {
> > -		/* Support the previous format */
> > -		if (header->size == offsetof(typeof(*header), adds_features))
> > -			bitmap_zero(header->adds_features, HEADER_FEAT_BITS);
> > -		else
> > -			return -1;
> > -	} else if (ph->needs_swap)
> > -		swap_features(header->adds_features);
> > +	if (ph->needs_swap && swap_header(header))
> > +		return -1;
> 
> Doesn't it change existing behavior?  It looks like supporting previous
> format on a same endian machines will be removed by this patch.

I'll check and try to add v2 perf.data reading test for both endians

thanks,
jirka
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