[dm-devel] dm: fix dax_dev NULL dereference

[Mike Snitzer]

I staged the fix (which I tweaked) here:
https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-5.3&id=95b9ebb78c4c733f8912a195fbd0bc19960e726e

Also, please note this additional related commit that just serves to
improve a related function name and clean up some whitespace:
https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-5.3&id=f965f935a89bb174fd3f6d6b51bba91c1ed258c5

I'll likely send these to Linus for 5.2-rc3 later this week.

Thanks,
Mike