[libvirt] [PATCH v9 6/7] block: Enable qemu_open/close to work with fd sets
Corey Bryant
coreyb at linux.vnet.ibm.com
Mon Aug 13 13:44:38 UTC 2012
I'll send a new version shortly with these updates also.
--
Regards,
Corey
On 08/11/2012 10:28 AM, Eric Blake wrote:
> On 08/11/2012 07:14 AM, Corey Bryant wrote:
>> When qemu_open is passed a filename of the "/dev/fdset/nnn"
>> format (where nnn is the fdset ID), an fd with matching access
>> mode flags will be searched for within the specified monitor
>> fd set. If the fd is found, a dup of the fd will be returned
>> from qemu_open.
>>
>
>> v9:
>> -Drop fdset refcount and check dup_fds instead. (eblake at redhat.com)
>> -Fix dupfd leak in qemu_dup(). (eblake at redhat.com)
>> -Always set O_CLOEXEC in qemu_dup(). (kwolf at redhat.com)
>> -Change name of qemu_dup() to qemu_dup_flags(). (kwolf at redhat.com)
>>
>
>> @@ -87,6 +146,40 @@ int qemu_open(const char *name, int flags, ...)
>> int ret;
>> int mode = 0;
>>
>> +#ifndef _WIN32
>> + const char *fdset_id_str;
>> +
>> + /* Attempt dup of fd from fd set */
>> + if (strstart(name, "/dev/fdset/", &fdset_id_str)) {
>> + int64_t fdset_id;
>> + int fd, dupfd;
>> +
>> + fdset_id = qemu_parse_fdset(fdset_id_str);
>> + if (fdset_id == -1) {
>> + errno = EINVAL;
>> + return -1;
>> + }
>> +
>> + fd = monitor_fdset_get_fd(fdset_id, flags);
>> + if (fd == -1) {
>> + return -1;
>> + }
>> +
>> + dupfd = qemu_dup_flags(fd, flags);
>> + if (fd == -1) {
>
> Checking the wrong condition:
> s/fd/dupfd/
>
>> + return -1;
>> + }
>> +
>> + ret = monitor_fdset_dup_fd_add(fdset_id, dupfd);
>> + if (ret == -1) {
>> + close(dupfd);
>> + return -1;
>
> This function appears to promise a reasonable errno on failure.
> However, I don't think monitor_fdset_dup_fd_add guarantees a reasonable
> errno, and even if it does, close() can corrupt errno. I think that
> prior to returning here, you either need an explicit errno=ENOMEM, or
> fix monitor_fdset_dup_fd to guarantee a nice errno, plus a save and
> restore of errno here. Unless no one cares about errno on failure, in
> which case your earlier errno=EINVAL can be dropped.
>
--
Regards,
Corey
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