Re: CONFIG_DM_MQ_DEFAULT makes my kernel unhappy..

[Christoph Hellwig <hch@infradead.org>]

On Sat, Apr 25, 2015 at 08:37:32AM -0700, Christoph Hellwig wrote:
> I'll give it a spin.
> 
> > What were you actually testing when this happened?  Were you failing
> > paths under IO load or something?
> 
> This happened on the initial udev-direct scan of the devices.
> 
> > Also, which upstream commit was your tree based on?  Did you have any
> > non-upstream patches applied that I should be aware of?
> 
> Latest Linus tree as of this morning.

Seems like the first warning goes away without CONFIG_DEBUG_OBJECTS.
Note that in either way I/O over dm-mpath actually works fine.

Btw, this is the script used to reproduce it, you need
CONFIG_TARGET_CORE, CONFIG_TCM_IBLOCK and CONFIG_LOOPBACK_TARGET
enabled.  It jsut creates two different targets with a lun each,
pointing to the same device.  The target code automatically supports
ALUA in this case.

---
#!/bin/bash

# add your own device
#DEV=/dev/sda

mount -t configfs none /sys/kernel/config/

tcm_node --block iblock_0/array /dev/sda

line=$(tcm_loop --createnexus=0)
wwn=$(echo $line | awk '{print $15}')
tcm_loop --addlun=$wwn 0 0 iblock_0/array

line=$(tcm_loop --createnexus=1)
wwn=$(echo $line | awk '{print $15}')
tcm_loop --addlun=$wwn 1 0 iblock_0/array