On Fri, Feb 15, 2019 at 03:03:34AM -0000, Cheng Chen wrote:
> When the drive-backup is running, I manually crash the iscsi server（or
> interrupt network, eg. iptables -j DROP）.
>
> Then after less than 1 minute：
> virsh qemu-monitor-command ${DOMAIN} --pretty '{ "execute": "query-block" }'
> will block and no any response, until timeout. This is still excusable.
> But, the disk（drive-virtio-disk0）will occur the same situation：in vm os, the
> disk will block and no any response.
>
> In other words, when qemu and iscsi-server lose contact, It will cause
> the vm unable.
I haven't tried to reproduce this but I guess QEMU reaches a
synchronization point where it waits for all outstanding requests to
complete. Since the iSCSI target is unresponsive QEMU gets stuck.
These issues can sometimes be fixed by avoiding the synchronization
point (a backtrace should reveal where the main loop thread is stuck)
but other times it really is necessary to wait for all requests and the
solution isn't as obvious.
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https://bugs.launchpad.net/bugs/1815993
Title:
drive-backup with iscsi will cause vm disk no response
Status in QEMU:
New
Bug description:
virsh qemu-monitor-command ${DOMAIN} '{ "execute" : "drive-backup" ,
"arguments" : { "device" : "drive-virtio-disk0" , "sync" : "top" ,
"target" : "iscsi://192.168.1.100:3260/iqn.2019-01.com.iaas/0" } }'
When the drive-backup is running, I manually crash the iscsi server（or
interrupt network, eg. iptables -j DROP）.
Then after less than 1 minute：
virsh qemu-monitor-command ${DOMAIN} --pretty '{ "execute": "query-block" }'
will block and no any response, until timeout. This is still excusable.
But, the disk（drive-virtio-disk0）will occur the same situation：in vm os, the
disk will block and no any response.
In other words, when qemu and iscsi-server lose contact, It will cause
the vm unable.
---
Host: centos 7.5
qemu version: ovirt-4.2（qemu-2.12.0）
qemu command line: qemu-system-x86_64 -name guest=test,debug-threads=on -S
-object
secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-190-test./master-key.aes
-machine pc-i440fx-3.1,accel=kvm,usb=off,dump-guest-core=off,mem-merge=off -m
1024 -mem-prealloc -mem-path /dev/hugepages1G/libvirt/qemu/190-test -realtime
mlock=off -smp 1,sockets=1,cores=1,threads=1 -uuid
1c8611c2-a18a-4b1c-b40b-9d82040eafa4 -smbios type=1,manufacturer=IaaS
-no-user-config -nodefaults -chardev socket,id=charmonitor,fd=31,server,nowait
-mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc -no-shutdown
-boot menu=on,strict=on -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2
-device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x3 -drive
file=/opt/vol/sas/fb0c7c37-13e7-41fe-b3f8-f0fbaaeec7ce,format=qcow2,if=none,id=drive-virtio-disk0,cache=writeback
-device
virtio-blk-pci,scsi=off,bus=pci.0,addr=0x5,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1,write-cache=on
-drive
file=/opt/vol/sas/bde66671-536d-49cd-8b46-a4f1ea7be513,format=qcow2,if=none,id=drive-virtio-disk1,cache=writeback
-device
virtio-blk-pci,scsi=off,bus=pci.0,addr=0x7,drive=drive-virtio-disk1,id=virtio-disk1,write-cache=on
-netdev tap,fd=33,id=hostnet0,vhost=on,vhostfd=34 -device
virtio-net-pci,netdev=hostnet0,id=net0,mac=00:85:45:3e:d4:3a,bus=pci.0,addr=0x6
-chardev pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0
-chardev socket,id=charchannel0,fd=35,server,nowait -device
virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=org.qemu.guest_agent.0
-device usb-tablet,id=input0,bus=usb.0,port=1 -vnc 0.0.0.0:0,password -device
cirrus-vga,id=video0,bus=pci.0,addr=0x2 -device
virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x4 -msg timestamp=on
iscsi：
yum -y install targetcli python-rtslib
systemctl start target
systemctl enable target
targetcli /iscsi create iqn.2019-01.com.iaas
targetcli /iscsi/iqn.2019-01.com.iaas/tpg1 set attribute
authentication=0 demo_mode_write_protect=0 generate_node_acls=1
targetcli /iscsi/iqn.2019-01.com.iaas/tpg1/portals create 192.168.1.100 3260
targetcli /backstores/fileio create testfile1 /backup/file1 2G
targetcli /iscsi/iqn.2019-01.com.iaas/tpg1/luns create
/backstores/fileio/testfile1
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