Re: [libvirt] [PATCH] qemu: Correctly label migration TCP socket passed to qemu
On 08/25/2011 08:30 AM, Jiri Denemark wrote:
>> - VIR_FORCE_CLOSE(spec->dest.fd.qemu);
>
> Unconditional, changed to...
>
>> + if (virSecurityManagerSetImageFDLabel(driver->securityManager, vm,
>> + spec->dest.fd.qemu) == 0) {
>> + ret = qemuMonitorMigrateToFd(priv->mon, migrate_flags,
>> + spec->dest.fd.qemu);
>> + VIR_FORCE_CLOSE(spec->dest.fd.qemu);
>
> ...conditional. Oops - you leak the fd if changing the label fails.
No, there's no leak here. The fd is closed by the caller in any case. Note,
we don't close it here if we fail before we ever get to
qemuMonitorMigrateToFd. This additional close after qemuMonitorMigrateToFd()
is just for better feeling in case migration started to avoid having an fd
open which doesn't technically belong to us anymore for the whole time of
migration.
Ah, makes sense. Until a child process is using the fd, it doesn't
matter if we close early, and you've convinced me that the caller mops
up in the cases where we don't close early. Meanwhile, once a child is
using the fd, then we don't want to get in the way (especially important
on pipes, where having multiple processes open as writers on the same
pipe can prevent readers from seeing EOF), so only closing early after
spawning the child makes sense. So,
ACK to this patch.
--
Eric Blake eblake(a)redhat.com +1-801-349-2682
Libvirt virtualization library http://libvirt.org