Re: [Qemu-devel] qemu : rbd block driver internal snapshot and vm_stop is hanging forever

[Alexandre DERUMIER]

Something is really wrong,

because guest is also freezing, with a simple snapshot, with cache=none / 
rbd_cache=false

qemu monitor : snapshot_blkdev_internal drive-virtio0 snap1

or 

rbd command : rbd --image myrbdvolume snap create --snap snap1 


Then the guest can't read/write to disk anymore.


I have tested with last ceph internalis, same problem



----- Mail original -----
De: "aderumier" <address@hidden>
À: "ceph-devel" <address@hidden>, "qemu-devel" <address@hidden>
Envoyé: Lundi 9 Novembre 2015 04:54:23
Objet: Re: [Qemu-devel] qemu : rbd block driver internal snapshot and vm_stop 
is hanging forever

Also, 

this occur only with rbd_cache=false or qemu drive cache=none. 


If I use rbd_cache=true or qemu drive cache=writeback, I don't have this bug. 


----- Mail original ----- 
De: "aderumier" <address@hidden> 
À: "ceph-devel" <address@hidden>, "qemu-devel" <address@hidden> 
Envoyé: Lundi 9 Novembre 2015 04:23:10 
Objet: Re: qemu : rbd block driver internal snapshot and vm_stop is hanging 
forever 

Some other infos: 

I can reproduce it too with manual snapshot with rbd command 


#rbd --image myrbdvolume snap create --snap snap1 

qemu monitor: 

#stop 


This is with ceph hammer 0.94.5. 


in qemu vm_stop, the only thing related to block driver are 

bdrv_drain_all(); 
ret = bdrv_flush_all(); 


----- Mail original ----- 
De: "aderumier" <address@hidden> 
À: "ceph-devel" <address@hidden>, "qemu-devel" <address@hidden> 
Envoyé: Lundi 9 Novembre 2015 04:10:45 
Objet: qemu : rbd block driver internal snapshot and vm_stop is hanging forever 

Hi, 

with qemu (2.4.1), if I do an internal snapshot of an rbd device, 
then I pause the vm with vm_stop, 

the qemu process is hanging forever 


monitor commands to reproduce: 


# snapshot_blkdev_internal drive-virtio0 yoursnapname 
# stop 




I don't see this with qcow2 or sheepdog block driver for example. 


Regards, 

Alexandre 
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