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





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



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