Noticed this while reviewing the extensions-write-zeroes branch: we
probably ought to audit errno usage, as I spotted several places that
use an undefined value of errno. For example:
if(expwrite(req->from, pkg->data, req->len, client, fua)) {
DEBUG("Write failed: %m");
rep.error = nbd_errno(errno);
This is assuming that expwrite() left a sane errno value, and that
DEBUG() didn't clobber it. But a quick look at DEBUG() shows that it
(can) call printf() (which can clobber errno), and a close look at
expwrite() shows that there are error paths where errno is indeterminate
(for example, expwrite() can return -1 if rawread_fully() fails, but
rawread_fully() can call close() in between read() and returning a
value, where close() can clobber errno).
It may be smarter to have functions return an actual error value (or
negative error value) instead of -1 on failure, rather than relying on
errno remaining unchanged through all the interim code.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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