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Date: Thu, 25 May 2017 10:07:24 +0200
From: Jiri Olsa <jolsa@redhat.com>
To: David Carrillo-Cisneros <davidcc@google.com>
Cc: linux-kernel@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Andi Kleen <ak@linux.intel.com>, Simon Que <sque@chromium.org>,
        Wang Nan <wangnan0@huawei.com>, Jiri Olsa <jolsa@kernel.org>,
        He Kuang <hekuang@huawei.com>, Masami Hiramatsu <mhiramat@kernel.org>,
        David Ahern <dsa@cumulusnetworks.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Stephane Eranian <eranian@google.com>, Paul Turner <pjt@google.com>
Subject: Re: [PATCH v2 10/13] perf header: add a buffer to struct feat_fd
Message-ID: <20170525080724.GA14467@krava>
References: <20170523074853.54892-1-davidcc@google.com>
 <20170523074853.54892-11-davidcc@google.com>
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On Tue, May 23, 2017 at 12:48:50AM -0700, David Carrillo-Cisneros wrote:

SNIP

> +
> +	memcpy(addr, fd->buf + fd->offset, size);
> +	fd->offset += size;
>  
> -	if (ret != (ssize_t)size)
> -		return ret < 0 ? (int)ret : -1;
>  	return 0;
>  }
>  
> @@ -187,6 +215,10 @@ static char *do_read_string(struct feat_fd *fd)
>  static int write_tracing_data(struct feat_fd *fd,
>  			      struct perf_evlist *evlist)
>  {
> +	if (fd->buf) {
> +		pr_err("Unsupported write_tracing_data to memory buffer.\n");
> +		return -1;
> +	}

could those messsages mention the pipe mode, this one
does not give clue it's pipe mode related

also together with your following patches, this condition
should never hit right? more like the assert stuff..
WARN_ON/WARN_ON_ONCE maybe

thanks,
jirka