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

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Message-ID: <87bo5ywzqm.fsf@sejong.aot.lge.com>
Date:	Fri, 19 Jul 2013 20:33:37 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Jiri Olsa <jolsa@...hat.com>
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 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.

Thanks,
Namhyung
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