[dm-devel] queue_if_no_path question

[Maxim Kozover]

Hi!
I have a question regarding queue_if_no_path behavior.
I tried either Red Hat 5.0 2.6.18-8.el5 kernel and more or less recent multipath-tools.
Set no_path_retry queue in multipath.conf and tried losing all paths
to a SAN device, while I'm dd-ing from /dev/zero to /dev/mapper/...

What's strange is that not only ios to that device got blocked, but
also ios to /tmp and /var/log/messages etc that reside on local drive.
When I return some paths to the SAN device, all ios resume, both ios
to that device and those unexpectedly blocked.
HBA used is QLE2462, I'm not sure if this happened with 2Gb QLogic
also.

Please tell me if this is an expected behavior and if not, how could
we find a source of the problem and fix it?

# ps aux | grep D
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root      2872  0.0  0.0  10064   748 ?        Ds   21:58   0:00 syslogd -m 0
root      3800 24.9  0.0  63300  1592 ttyS0    D    22:01   0:22 dd if
/dev/zero of /dev/mapper/...
root      3990  0.0  0.0  58020   476 ttyS0    D    22:02   0:00 tail -f /var/log/messages

Thanks much,

Maxim.