Weirdness with discard cmd and get log pages

[Keith Busch]

On Fri, Oct 14, 2016 at 02:33:49PM -0700, Nisha Miller wrote:
> My problem is that I need to make it work on Kernel 2.6.33. For now,
> since blkdiscard and fstrim send only 1 range I'm ok with current
> support for discard cmd.
> 
> However I need to fix the issue for get log pages. Are there any known
> issues with mapping user buffers in older linux-nvme drivers?

I'm pretty sure it works. I tested on a RHEL 6.6 (a 2.6.32 fork), and
I can read all the log pages without issue.

The nvme-cli doesn't align every buffer on page boundaries, so many of
these passthru commands require PRP2. Is your device using this correctly
on non-RW commands?