[libvirt] [Qemu-devel] [PATCH v4 7/7] osdep: Enable qemu_open to dup pre-opened fd

[Corey Bryant]

On 06/25/2012 10:34 AM, Eric Blake wrote:
> On 06/25/2012 08:24 AM, Corey Bryant wrote:
>
>>>> +            if (fcntl_setfl(ret, O_CLOEXEC, (flags & O_CLOEXEC) ? 1
>>>> : 0) < 0) {
>>>
>>> Broken.  O_CLOEXEC _only_ affects open(); to change it on an existing
>>> fd, you have to use fcntl(F_GETFD/F_SETFD) (not F_GETFL/F_SETFL).
>>>
>>>
>>
>> I'll fix this in v5.
>
> Don't we already have qemu_set_cloexec() for this purpose?
>

Yes, it looks that way.  I'll use qemu_set_cloexec().

>>
>> I see your point.  I'll call fcntl(F_GETFL) once to get the current
>> flags, determine what needs to be set on/off, and then call
>> fnctl(F_SETFL) once.  In this case I won't be using fcntl_setfl()
>> anymore.  Do you want me to drop the fcntl_setfl() changes I made?
>
> Or maybe make fcntl_setfl() take a mask of bits to alter?  You're right
> that it's not worth changing if you won't take advantage of the changes.
>

Good idea.  I'll modify fcntl_setfl() to take a mask of bits to turn on 
or off.

>>
>> Also, I noticed in the fnctl man page that F_SETFL:  "On Linux this
>> command can change only the O_APPEND, O_ASYNC, O_DIRECT, O_NOATIME, and
>> O_NONBLOCK flags."  So I'll only set/unset these flags.
>
> O_NDELAY is the obsolete spelling of O_NONBLOCK; which means the only
> other flags in your list not supported by Linux are O_LARGEFILE (which I
> said was pointless), O_NOCTTY (which only has an impact at open() and
> not later on, so it is not worth worrying about), and O_SYNC (so for
> that one, you should error out if not set correctly, as the difference
> between O_SYNC on vs. off is significant).
>

Ok I'll take this into account.  Thanks.

-- 
Regards,
Corey