linux-kernel - Re: [PATCH v3 4/6] Fix read / write data offsets in read / write loops

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Message-ID: <20170621092914.3f653151@gandalf.local.home>
Date:   Wed, 21 Jun 2017 09:29:14 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Michael Sartain <mikesart@...tmail.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/6] Fix read / write data offsets in read / write
 loops

On Wed, 14 Jun 2017 18:27:59 -0600
Michael Sartain <mikesart@...tmail.com> wrote:

> The tot variable in __do_write and do_read is incremented with the amount read
> / written, but subsequent times through the loop the calls continue to use the
> original data pointer.
> 
> Signed-off-by: Michael Sartain <mikesart@...tmail.com>
> ---
>  trace-cmd-local.h | 2 +-
>  trace-input.c     | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/trace-cmd-local.h b/trace-cmd-local.h
> index 8595a8a..b8ab35b 100644
> --- a/trace-cmd-local.h
> +++ b/trace-cmd-local.h
> @@ -31,7 +31,7 @@ static ssize_t __do_write(int fd, const void *data, size_t size)
>  	ssize_t w;
>  
>  	do {
> -		w = TEMP_FAILURE_RETRY(write(fd, data, size - tot));
> +		w = TEMP_FAILURE_RETRY(write(fd, data + tot, size - tot));

Good catch. I'm going to modify this to remove the TEMP_FAILURE_RETRY()
though. I'll hopefully get this pushed out later today, and we could
add the write_intr() and friends later.

-- Steve

>  		tot += w;
>  
>  		if (!w)
> diff --git a/trace-input.c b/trace-input.c
> index 251d32b..8395917 100644
> --- a/trace-input.c
> +++ b/trace-input.c
> @@ -202,7 +202,7 @@ static ssize_t do_read(struct tracecmd_input *handle, void *data, size_t size)
>  	ssize_t r;
>  
>  	do {
> -		r = TEMP_FAILURE_RETRY(read(handle->fd, data, size - tot));
> +		r = TEMP_FAILURE_RETRY(read(handle->fd, data + tot, size - tot));
>  		tot += r;
>  
>  		if (!r)