On 03/19/2013 07:39 AM, John Ferlan wrote:
> On 03/15/2013 12:32 PM, Daniel P. Berrange wrote:
>> From: "Daniel P. Berrange" <berrange@xxxxxxxxxx>
>>
>> Add a virFileNBDDeviceAssociate method, which given a filename
>> will setup a NBD device, using qemu-nbd as the server.
>>
>> Signed-off-by: Daniel P. Berrange <berrange@xxxxxxxxxx>
>> ---
>> +virFileNBDDeviceFindUnused(void)
>> +{
>> + DIR *dh;
>> + char *ret = NULL;
>> + struct dirent *de;
>> +
>> + if (!(dh = opendir(SYSFS_BLOCK_DIR))) {
>> + virReportSystemError(errno,
>> + _("Cannot read directory %s"),
>> + SYSFS_BLOCK_DIR);
>> + return NULL;
>> + }
>> +
>> + while ((de = readdir(dh)) != NULL) {
readdir() is an annoying interface. To properly distinguish errors, you
have to assign errno to 0 before each iteration, then check if errno is
set when the while loop terminates.
>> + if (STRPREFIX(de->d_name, "nbd")) {
>> + int rv = virFileNBDDeviceIsBusy(de->d_name);
>> + if (rv < 0)
>> + goto cleanup;
>> + if (rv == 0) {
>> + if (virAsprintf(&ret, "/dev/%s", de->d_name) < 0) {
>> + virReportOOMError();
>> + goto cleanup;
>> + }
>> + goto cleanup;
>> + }
>> + }
>> + }
>> +
>> + virReportSystemError(EBUSY, "%s",
>> + _("No free NBD devices"));
Your choice of error reporting is to blindly overwrite any (potential)
error from readdir. That potentially loses information. Then again,
since you normally succeed only by finding a winning existing entry, and
since you are at least giving a reasonable error message, even if you
overwrote the readdir() errno, I can live with it.
>> +int virFileNBDDeviceAssociate(const char *file,
>> + char **dev ATTRIBUTE_UNUSED,
>> + bool readonly ATTRIBUTE_UNUSED)
>> +{
>> + virReportSystemError(ENOSYS,
>> + _("Unable to associate file %s with NBD device"),
>> + file);
>> + *dev = NULL;
>
> Since this is done - should this still be UNUSED in the header?
It doesn't hurt to leave it in, but it also doesn't hurt to take out the
ATTRIBUTE_UNUSED or even drop the '*dev = NULL' line.
> ACK in any case.
Agreed.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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