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



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


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