Re: The issue about adding multipath device's targets into qemu-pr-helper's namespace

On 7/14/20 3:41 PM, Lin Ma wrote: > Hi all, > > I have a namespace question about passthrough disk(multipath device). > In case of enabling namespace and cgroups in qemu.conf, The target(s) > of the > multipath device won't be added into qemu-pr-helper's namespace under > certain > situation, It causes the PERSISTENT RESERVE command failure in guest. > Yeah, this is expected. I mean, the failure is expected if not all devices are added to the namespace. > While user starts a vm, > To build namespace, The qemuDomainSetupDisk() will be invoked via > threadA(this > thread id will be the qemu's pid), > To build cgroup, The qemuSetupImagePathCgroup() will be invoked via > threadB. > > Both of the functions invoke the virDevMapperGetTargets() trying to > parse a > multipath device to target paths string, Then fill the targetPaths[]. > > The issue I experienced is: > After libvirtd started, Everything works well for the first booted vm > which has > the passthrough multipath device. > But If I shut it down & start it again, OR keep it running & start > another vm > which has other passthrough multipath device, Then the target(s) of > the fresh > started vm won't be added into the related qemu-pr-helper's namespace > and it > causes PERSISTENT RESERVE command failure in the corresponding guest. > I digged into code, In this situation, The targetPaths[] in > qemuDomainSetupDisk() > won't be filled, it keeps NULL after virDevMapperGetTargets() returns. > The virDevMapperGetTargets doesn't fill targetPaths[] because the > dm_task_run() > of libdevmapper returns 0 with errno 9(Bad file descriptor). > So far, I don't understand why the dm_task_run() return 0 in this > situation. > BTW, The virDevMapperGetTargets() can always successfully fill the > targetPaths[] > in qemuSetupImagePathCgroup(). What is your libvirt version? I've merged a fix for something similar not a long ago: v6.5.0-rc1~190 Can you please check v6.5.0?