[libvirt] [PATCH] qemuDomainGetPreservedMounts: Fetch list of /dev/* mounts dynamically

[Martin Kletzander]

On Fri, Jan 06, 2017 at 02:57:21AM +0000, Qiao, Liyong wrote:
>Hi Michal
>
>☹ Nothing changes with your patch(without workaround and with /dev/mqueue mounted)
>

The workaround is turning off namespaces?

>root at s2600wt:~/linux# cat /proc/mounts | grep mqueue
>none /dev/mqueue mqueue rw,relatime 0 0
>root at s2600wt:~/linux# vim /etc/libvirt/qemu.conf
>root at s2600wt:~/linux# grep namespace /etc/libvirt/qemu.conf
># To enhance security, QEMU driver is capable of creating private namespaces
># for each domain started. Well, so far only "mount" namespace is supported. If
># devices entries throughout the domain lifetime. This namespace is turned on
>#namespaces = [ "mount" ]
>#namespaces = []
>root at s2600wt:~/linux# virsh start kvm02
>error: Failed to start domain kvm02
>error: An error occurred, but the cause is unknown
>
>Attach kvm02.log, but seems nothing debug information helpful.
>
>2017-01-06 02:47:37.544+0000: 74279: debug : virCommandHandshakeChild:435 : Notifying parent for handshake start on 26
>2017-01-06 02:47:37.544+0000: 74279: debug : virCommandHandshakeChild:443 : Waiting on parent for handshake complete on 27
>libvirt:  error : libvirtd quit during handshake: Input/output error
>

So, if I'm reading it correctly, this means that there was no problem in
qemuProcessHook, but probably there was a problem in the main thread
running qemuProcessLaunch.  Would you mind looking at the libvirtd.log
as well, please?  Since I can't reproduce it and neither there is error
set, it is pretty hard to find where the problem is.  The log _might_ be
helpful in this regard.

Thanks,
Martin

>
>
>Best Regards
>
>Eli Qiao(乔立勇）OpenStack Core team OTC Intel.
>--
>
>
>On 05/01/2017, 10:46 PM, "Martin Kletzander" <mkletzan at redhat.com> wrote:
>
>    On Thu, Jan 05, 2017 at 02:41:02PM +0100, Michal Privoznik wrote:
>    >With my namespace patches, we are spawning qemu in its own
>    >namespace so that we can manage /dev entries ourselves. However,
>    >some filesystems mounted under /dev needs to be preserved in
>    >order to be shared with the parent namespace (e.g. /dev/pts).
>    >Currently, the list of mount points to preserve is hardcoded
>    >which ain't right - on some systems there might be less or more
>    >items under real /dev that on our list. The solution is to parse
>    >/proc/mounts and fetch the list from there.
>    >
>
>    Works for me, ACK.  I still wonder whether we should mark the mounts as
>    slaves.  I was also wondering if there are multiple sub-subtrees and
>    from the code it looks like it will 'just work'.  Nice.
>
>    Martin
>
>
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