[dm-devel] CONFIG_DM_MQ_DEFAULT makes my kernel unhappy..

[Christoph Hellwig]

On Sat, Apr 25, 2015 at 11:28:57AM -0400, Mike Snitzer wrote:
> On Sat, Apr 25 2015 at  5:23am -0400,
> Christoph Hellwig <hch at infradead.org> wrote:
> 
> > Running dm-mpath against a tcm_loop target with two ALUA paths makes
> > the kernel very unhappy when CONFIG_DM_MQ_DEFAULT is set.  Without it
> > it's perfectly happy.
> 
> Wonder if commit 63a4f065ec ("dm: fix add_disk() NULL pointer due to
> race with free_dev()") left something not quite right relative to
> blk-mq?  Or maybe this is a problem confined to blk-mq itself.

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.