On 11/17/20 2:42 AM, Zihao Chang wrote:
On 2020/11/16 23:10, Michal Privoznik wrote:
On 11/16/20 3:22 PM, Zihao Chang wrote:
Hi all,
When using qemu-pr-helper，"sg_persist" in guest return Aborted Command after
iscsiadm logout & login.
My confusion:
Is this problem caused by bugs of libvirt/qemu-pr-helper?
Or iscsiadm logout & login should be forbidden when using qemu-pr-helper?
Or There is something wrong with my config.
Steps to Reproduce:
1. setup multipath env
1) set /etc/iscsi/initiatorname.iscsi
2) iscsiadm discovery & login
3) start multipathd
2. add the following xml to guest
<disk type='block' device='lun'>
<driver name='qemu' type='raw' cache='none' io='native'/>
<source dev='/dev/mapper/XXXXXXXXXXXXXXXXX'>
**<reservations managed='yes'/>**
</source>
<target dev='sdc' bus='scsi'/>
</disk>
3. start the guest
1) "sg_persist -v -i -n -k -d /dev/sdc" works well in the guest
2) here /dev/sdc(guest) -> /dev/sdht(host)
4. iscsiadm logout & login on host
1) iscsiadm -m node -u (host)
2) iscsiadm -m node -l (host)
3) here /dev/sdc(guest) -(change)-> /dev/sdfo(host)
5. exec "sg_persist -v -i -n -k -d /dev/sdc" in the guest
1) command return:
Persistent Reservation In cmd: 5e 00 00 00 00 00 00 20 00 00
persistent reservation in:
Fixed format, current; Sense key: Aborted Command
Additional sense: Logical unit communication failure
PR in (Read keys): Aborted command sense key, other than protection
related (asc=0x10)
2) strace qemu-pr-helper show:
openat(AT_FDCWD, "/dev/sdht", O_RDONLY) = -1 ENOENT (No such file or
directory)
Additional info:
1. strace qemu-pr-helper show:
openat(AT_FDCWD, "/dev/sdht", O_RDONLY) = -1 ENOENT (No such file or
directory)
2. This problem may be related to mnt(namespace). I try to set mnt of
qemu-pr-helper as pid 1, sg_persist works well after logout & login.
Yeah, this smells like a libvirt bug. But I'm not sure how to solve it. Because
from security POV we want to run qemu-pr-helper inside the same namespace as
qemu is running (so that it doesn't see more devices than needed). But at the
same time, when a /dev node changes from outside libvirt does not reflect that
in the namespace.
BTW: is /dev/mapper/XXX updated on re-login? Becuase if not, then you'd get the
same error in qemu, if it wasn't for pr-helper hitting the issue first.
A possible work around might be to use unmanaged pr-helper (reservations
managed='no') and just start it by hand.
Michal
.
Actually, if use unmanaged pr-helper (reservations managed='no'), "sg_persist"
work well without starting pr-helper by
hand in this case. After logout & login qemu does not meet openat() ENOENT (No
such file or directory), and qemu even
does not use openat() according to the result of "strace" command. But the
source code of libvirt shows that it start
pr-helper inside the same namespace as qemu is running. It really confused me.
Can it be that qemu is running privileged and thus can do the
reservation itself? Otherwise I don't understand what's going on.
Michal
