Re: [libvirt] [Qemu-devel] [PATCH v4 7/7] osdep: Enable qemu_open to dup pre-opened fd
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?
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.
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).
--
Eric Blake eblake(a)redhat.com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
Attachments:
- signature.asc (application/pgp-signature — 620 bytes)