rhel8: KVM running, Unplugging the FC cable on hypervisor causes I/O errors on multipass passthrough.
Issue
We use the passthrough of multipath device. The multipath device(mpathab) on the host is recognized as /dev/sda on the guest.
<driver name='qemu' type='raw' cache='none' io='native'/>
<source dev='/dev/mapper/mpathab' index='3'/>
<backingStore/>
<target dev='sda' bus='scsi'/>
<alias name='scsi0-0-0-0'/>
<address type='drive' controller='0' bus='0' target='0' unit='0'/>
We unplugged 3 out of 4 FC cables at the same time for the testing. Then I/O error occurred on /dev/sda on the guest and filesystem became read-only.
kernel: sd 0:0:0:0: [sda] tag#15 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_S>
kernel: sd 0:0:0:0: [sda] tag#15 Sense Key : Aborted Command [current]
kernel: sd 0:0:0:0: [sda] tag#15 Add. Sense: I/O process terminated
kernel: sd 0:0:0:0: [sda] tag#15 CDB: Synchronize Cache(10) 35 00 00 00 00 00 0000>
kernel: EXT4-fs (sda4): Remounting filesystem read-only
From the host log, I/O error occurred on the devices of mpathab, while multipathd detected the pass failure.
So in reality the filesystem went readonly, but we would expect that the remaining path handles the I/O.
Environment
- Red Hat Enterprise Linux (RHEL) 8
- multipath
- KVM guest, passthrough configuration
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