linux-kernel - Re: [4.10, panic, regression] iscsi: null pointer deref at iscsi_tcp_segment

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Message-ID: <60385463-d6e6-3880-029e-93965f1fc940@fb.com>
Date:   Thu, 22 Dec 2016 17:16:23 -0700
From:   Jens Axboe <axboe@...com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Dave Chinner <david@...morbit.com>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Peter Anvin <hpa@...or.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [4.10, panic, regression] iscsi: null pointer deref at
 iscsi_tcp_segment_done+0x20d/0x2e0

On 12/22/2016 02:10 PM, 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@...morbit.com> 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?
> 
> 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.

We have it running on thousands of machines at Facebook, and I've used
it in all of my testing, haven't seen any issues. It's been run pretty
damn hard.

-- 
Jens Axboe