Re: [Qemu-devel] Abnormal function exit message in Qemu block drivers code

[Cao,Bing Bu]

On 10/27/2011 02:16 PM, shu ming wrote:
> Hi,
>   After reading the block driver code in,  it was found that the error 
> exit code behaved in different ways.  Here are some examples.  It 
> seems that way 3 is a better way to log the error message.  In fact,  
> It is pretty important for a administrator to know what is going on 
> and be informed the error when that happens. I believe  we should 
> convert all the error exit code to way 3 gradually and make all the 
> new code to follow an unique standard.
>   Further more, really, some errors can be ignored while others can 
> not.  So we can have a more flexible function to classify the level of 
> the error message like
> error_report(log_level,  "string format", string);
>
> 1)The error code exited silently.
>
> case QCOW2_EXT_MAGIC_BACKING_FORMAT:
>             if (ext.len >= sizeof(bs->backing_format)) {
>                 fprintf(stderr, "ERROR: ext_backing_format: len=%u too 
> large"
>                         " (>=%zu)\n",
>                         ext.len, sizeof(bs->backing_format));
>                 return 2;
>             }

The example of the first way looks like not correct.

    case QCOW2_EXT_MAGIC_BACKING_FORMAT:
        if (ext.len >= sizeof(bs->backing_format)) {
-           fprintf(stderr, "ERROR: ext_backing_format: len=%u too large"
-                      " (>=%zu)\n",
-                       ext.len, sizeof(bs->backing_format));
            return 2;
        }

> 2)  fprintf() to emit the error message
>
> case QCOW2_EXT_MAGIC_BACKING_FORMAT:
>             if (ext.len >= sizeof(bs->backing_format)) {
>                 fprintf(stderr, "ERROR: ext_backing_format: len=%u too 
> large"
>                         " (>=%zu)\n",
>                         ext.len, sizeof(bs->backing_format));
>                 return 2;
> 3) A error_report() function to emit the error message.
>
> /* Find driver and parse its options */
>     drv = bdrv_find_format(fmt);
>     if (!drv) {
>         error_report("Unknown file format '%s'", fmt);
>         ret = -EINVAL;
>         goto out;
>     }