[Bug 1540407] Re: multipathd drops paths of a temporarily lost device

[Ryan Harper]

Hi Thorsten,

The latest version of the multipath-tools package is  0.5.0-7ubuntu14.
Can you confirm you're still seeing the issue?

Meanwhile, I'm hoping to recreate this issue on zKVM shortly.  In the
meantime I'm testing this on in an x86 VM with multipath via virtio-
scsi, using the same multipath.conf as mentioned in the bug.

# dpkg -s multipath-tools| grep ^Version
Version: 0.5.0-7ubuntu14

# multipath -ll
mpatha (0QEMU_QEMU_HARDDISK_0001) dm-0 QEMU,QEMU HARDDISK
size=10G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
  |- 2:0:0:0 sda 8:0  active ready running
  `- 2:0:0:1 sdb 8:16 active ready running


I can mark the device offline with:


# echo "offline" > /sys/class/block/sdb/device/state
# multipath -ll
mpatha (0QEMU_QEMU_HARDDISK_0001) dm-0 QEMU,QEMU HARDDISK
size=10G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
  |- 2:0:0:0 sda 8:0  active ready  running
  `- 2:0:0:1 sdb 8:16 active faulty offline


# sleep 60 && multipath -ll 
mpatha (0QEMU_QEMU_HARDDISK_0001) dm-0 QEMU,QEMU HARDDISK
size=10G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
  |- 2:0:0:0 sda 8:0  active ready  running
  `- 2:0:0:1 sdb 8:16 failed faulty offline

And bring it back online with:

# echo "1" > /sys/block/sdb/device/delete
# for RESCAN in /sys/class/scsi_host/*; do echo "- - -" > $RESCAN/scan; done 
# multipath -v2 
# multipath -ll
mpatha (0QEMU_QEMU_HARDDISK_0001) dm-0 QEMU,QEMU HARDDISK
size=10G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
  |- 2:0:0:0 sda 8:0  active ready running
  `- 2:0:0:1 sdb 8:16 active ready running

It maybe that the underlying device would need to be in error instead of the scsi layer in the kernel.
I'll update this when I get the zKVM instance up with multipath as described in the bug.

Looking at the delta between 0.5.0 in Ubuntu and the newer version in
Debian, there are a number of changes in the area of discovery and path
checking which may resolve this issue if we can confirm we're still
seeing the issue on the latest version in Xenial.

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https://bugs.launchpad.net/bugs/1540407

Title:
  multipathd drops paths of a temporarily lost device

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