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).