Re: [4.10, panic, regression] iscsi: null pointer deref at iscsi_tcp_segment_done+0x20d/0x2e0

[Dave Chinner]

On Thu, Dec 22, 2016 at 01:10:19PM -0800, Linus Torvalds wrote:
> Ok, so the numa issue was a red herring. With that fixed:
> 
> On Thu, Dec 22, 2016 at 1:06 PM, Dave Chinner <david@xxxxxxxxxxxxx> wrote:
> >
> > Better, but still bad. average files/s is not up to 200k files/s,
> > so still a good 10-15% off where it should be. xfs_repair is back
> > down to 10-15% off where it should be, too. bulkstat still fires off
> > a bad page reference count warning, iscsi still panics immediately.
> 
> Do you have CONFIG_BLK_WBT enabled, perhaps?

Ok, yes, that's enabled. Let me go turn it off and see what happens.

> It's new to this merge window, and I'm not convinced it's been tuned.
> Particularly for your kinds of fairly extreme IO loads.

Well, these aren't extreme IO workloads. Yes, the filesystem does a
lot of work on the CPU, but the IO loads XFS generates aren't
particularly high - maybe 2-3000 IOPS at most, and mostly the
bandwidth is below 100MB/s.

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx