I had a look at this bug and I seem to have prevented it, i.e.:
njo...@fantail:~$ cat /tmp/455832.xml
<disk type='block'>
<driver name='virtio'/>
<source dev='/dev/sdd'/>
<target dev='vdc' bus='virtio'/>
</disk>
(sdd is a USB stick)
Before patch:
njo...@fantail:~$ virsh list; virsh destroy lucid-test; virsh start lucid-test;
virsh attach-device lucid-test /tmp/455832.xml; virsh attach-device lucid-test
/tmp/455832.xml
Id Name State
----------------------------------
9 lucid-test running
Domain lucid-test destroyed
Domain lucid-test started
Device attached successfully
error: Failed to attach device from /tmp/455832.xml
error: server closed connection
After patch:
njo...@fantail:~$ virsh list; virsh destroy lucid-test; virsh start lucid-test;
virsh attach-device lucid-test /tmp/455832.xml; virsh attach-device lucid-test
/tmp/455832.xml
Id Name State
----------------------------------
10 lucid-test running
Domain lucid-test destroyed
Domain lucid-test started
Device attached successfully
error: Failed to attach device from /tmp/455832.xml
error: operation failed: target vdc already exists
>From GDB w/o patch:
Core was generated by `libvirtd -v'.
Program terminated with signal 11, Segmentation fault.
#0 0x00007f3cbe516402 in virCgroupPathOfController (group=0x0, controller=4,
key=0x7f3cbe5d6d7c "devices.deny", path=0x7f3cb7fc88d8) at util/cgroup.c:246
246 if (group->controllers[controller].mountPoint == NULL)
(gdb) p
The history is empty.
(gdb) bt
#0 0x00007f3cbe516402 in virCgroupPathOfController (group=0x0, controller=4,
key=0x7f3cbe5d6d7c "devices.deny", path=0x7f3cb7fc88d8) at util/cgroup.c:246
#1 0x00007f3cbe51661c in virCgroupSetValueStr (group=0x0, controller=4,
key=0x7f3cbe5d6d7c "devices.deny", value=0x7f3cb0049b40 "b 8:16 rwm") at
util/cgroup.c:271
#2 0x00007f3cbe516914 in virCgroupDenyDevice (group=0x0, type=<value optimized
out>, major=<value optimized out>, minor=<value optimized out>) at
util/cgroup.c:882
#3 0x00007f3cbe516bf4 in virCgroupDenyDevicePath (group=0x0, path=<value
optimized out>) at util/cgroup.c:932
#4 0x000000000043ce2b in qemudDomainAttachDevice (dom=0x7f3cb0028920,
xml=0x7f3cb006a9d8 "\340\244u") at qemu/qemu_driver.c:5505
#5 0x00007f3cbe551e81 in virDomainAttachDevice (domain=0x7f3cb0028920,
xml=0x7f3cb000f080 "<disk type='block'>\n <driver name='virtio'/>\n
<source dev='/dev/sdb'/>\n <target dev='vdc' bus='virtio'/>\n</disk>\n") at
libvirt.c:5093
#6 0x000000000042296f in remoteDispatchDomainAttachDevice (server=<value
optimized out>, client=<value optimized out>, conn=0x758bc0, hdr=<value
optimized out>, rerr=0x7f3cb7fc8b80, args=0x7f3cb7fc8c10,
ret=0x7f3cb7fc8c60) at remote.c:883
#7 0x0000000000424421 in remoteDispatchClientCall (server=<value optimized
out>, client=0x762110, msg=0x7a30f0) at dispatch.c:506
#8 0x00000000004247d3 in remoteDispatchClientRequest (server=0x74f110,
client=0x762110, msg=0x7a30f0) at dispatch.c:388
#9 0x000000000041768c in qemudWorker (data=<value optimized out>) at
libvirtd.c:1522
#10 0x00007f3cbca0b9ca in start_thread (arg=<value optimized out>) at
pthread_create.c:300
#11 0x00007f3cbc76969d in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#12 0x0000000000000000 in ?? ()
Basically, it appears that qemudDomainAttachDevice calls
virCgroupDenyDevicePath using a NULL pointer, the attached patch will
not call cgroup if the pointer is NULL.
I'm not sure if this requires any more tidying up.
** Patch added: "Patch to not run virCgroupDenyDevicePath if cgroup pointer is
NULL"
http://launchpadlibrarian.net/49053293/9025-do-not-deny-cgroup-if-null.patch
--
segfault when attaching disk with same physical device
https://bugs.launchpad.net/bugs/455832
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