[i-g-t,v2,1/4] runner/executor: Check for error at writing dmesg dump

[Ryszard Knop]

On Wed, 2024-11-20 at 19:32 +0100, Kamil Konieczny wrote:
> In processing kernel dmesg there are checks for error at reading
> so add also one for writing.
> 
> Signed-off-by: Kamil Konieczny <kamil.konieczny at linux.intel.com>
> Reviewed-by: Krzysztof Karas <krzysztof.karas at intel.com>
> ---
>  runner/executor.c | 29 ++++++++++++++++++++++++++---
>  1 file changed, 26 insertions(+), 3 deletions(-)
> 
> diff --git a/runner/executor.c b/runner/executor.c
> index ac73e1dde..e4d1fc323 100644
> --- a/runner/executor.c
> +++ b/runner/executor.c
> @@ -600,7 +600,7 @@ static long dump_dmesg(int kmsgfd, int outfd)
>  	bool underflow_once = false;
>  	char cont;
>  	char buf[2048];
> -	ssize_t r;
> +	ssize_t r, w;
>  	long written = 0;
>  
>  	if (kmsgfd < 0)
> @@ -654,9 +654,32 @@ static long dump_dmesg(int kmsgfd, int outfd)
>  			return written;
>  		}
>  
> -		write(outfd, buf, r);
> -		written += r;
> +		w = write(outfd, buf, r);
> +		if (w < r) {

You could rewrite this entire block to have a single write call, or to handle multiple
interrupts/better error messages:

int encountered_errors = 0;
while (written < r) {
  int w = write(outfd, buf + written, r - written);
  if (w > 0) {
    written += w;
    continue;
  }

  encountered_errors += 1;
  if (encountered_errors >= 100) {
    errf("Too many errors while writing out dmesg, aborting\n");
    break;
  }

  // Recoverable errors:
  if ((errno == EINTR) || (errno == EAGAIN)) continue;

  // Non-recoverable:
  errf("Error writing out dmesg (written %ld < %ld bytes): %s\n", written, r, strerror(errno));
  break;
}

> +			if (w == -1 && errno == EINTR)
> +				w = write(outfd, buf, r);
> +
> +			if (w < r && w >= 0)
> +				w += write(outfd, buf + w, r - w);
> +
> +			if (w < r) {
> +				long err = -errno;
> +
> +				if (err) {
> +					errf("Write error while processing dmesg, errno=%d %ld <
> %ld\n", errno, w, r);
> +				} else {
> +					errf("Cannot write dmesg chunk: %ld < %ld\n", w, r);
> +					err = -1;
> +				}
>  
> +				if (comparefd >= 0)
> +					close(comparefd);
> +
> +				return err;
> +			}
> +		}
> +
> +		written += r;
>  		if (comparefd < 0 && sscanf(buf, "%u,%llu,%llu,%c;",
>  					    &flags, &seq, &usec, &cont) == 4) {
>  			/*