[libvirt] [v2] storage: Ignore dangling symbol link for filesystem pool

[Osier Yang]

于 2010年12月21日 22:40, Eric Blake 写道:
> On 12/20/2010 11:47 PM, Osier Yang wrote:
>>
>> a more efficient solution would be to check if errno
>>> is ELOOP or ENOENT (the only possibilities for a dangling symlink; any
>>> other error should return -1), and in those two cases a successful
>>> lstat() is sufficient to detect a broken symlink without resorting to
>>> reading its contents.
>>>
>>
>> I guess you mean stat, lstat will not work here, as it doesn't follow
>> the *symbolic* link. what we need to do is to determine if the symbolic
>> link is dangling, so use "stat" to update the patch, v3 send, thanks
>> again.
>
> No, I really meant lstat().  If stat() would have failed because of a
> dangling symlink, then open() will fail for the same reasons.
> Therefore, check errno before lstat, and use the successful lstat as
> proof that a symlink is in place but that stat()ing the symlink would
> fail because it is dangling.
>
> if (open(f)<  0) {
>      if ((errno == ENOENT || errno == ELOOP)&&
>          lstat(f, buf) == 0) {
>          /* Dangling symlink, since lstat() passed but open failed. */
>          log message about ignored file
>          return -2;
>      }
>      either an unrelated errno, like EACCES, or we got ENOENT because
>      the file was deleted after readdir but before open/lstat
>      error message about unaccessible file
>      return -1;
> }
>
Eric, thanks for the detailed knowledge..

- Osier