linux-kernel - Re: [PATCHSET v6] blk-mq scheduling framework

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Message-ID: <67fdc091-443d-2180-2af9-5bda96356d18@kernel.dk>
Date:   Mon, 16 Jan 2017 08:47:18 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Hannes Reinecke <hare@...e.de>, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org
Cc:     osandov@...ndov.com, bart.vanassche@...disk.com
Subject: Re: [PATCHSET v6] blk-mq scheduling framework

On 01/16/2017 08:16 AM, Jens Axboe wrote:
> On 01/16/2017 08:12 AM, Jens Axboe wrote:
>> On 01/16/2017 01:11 AM, Hannes Reinecke wrote:
>>> On 01/13/2017 05:02 PM, Jens Axboe wrote:
>>>> On 01/13/2017 09:00 AM, Jens Axboe wrote:
>>>>> On 01/13/2017 08:59 AM, Hannes Reinecke wrote:
>>>>>> On 01/13/2017 04:34 PM, Jens Axboe wrote:
>>>>>>> On 01/13/2017 08:33 AM, Hannes Reinecke wrote:
>>>>>> [ .. ]
>>>>>>>> Ah, indeed.
>>>>>>>> There is an ominous udev rule here, trying to switch to 'deadline'.
>>>>>>>>
>>>>>>>> # cat 60-ssd-scheduler.rules
>>>>>>>> # do not edit this file, it will be overwritten on update
>>>>>>>>
>>>>>>>> ACTION!="add", GOTO="ssd_scheduler_end"
>>>>>>>> SUBSYSTEM!="block", GOTO="ssd_scheduler_end"
>>>>>>>>
>>>>>>>> IMPORT{cmdline}="elevator"
>>>>>>>> ENV{elevator}=="*?", GOTO="ssd_scheduler_end"
>>>>>>>>
>>>>>>>> KERNEL=="sd*[!0-9]", ATTR{queue/rotational}=="0",
>>>>>>>> ATTR{queue/scheduler}="deadline"
>>>>>>>>
>>>>>>>> LABEL="ssd_scheduler_end"
>>>>>>>>
>>>>>>>> Still shouldn't crash the kernel, though ...
>>>>>>>
>>>>>>> Of course not, and it's not a given that it does, it could just be
>>>>>>> triggering after the device load and failing like expected. But just in
>>>>>>> case, can you try and disable that rule and see if it still crashes with
>>>>>>> MQ_DEADLINE set as the default?
>>>>>>>
>>>>>> Yes, it does.
>>>>>> Same stacktrace as before.
>>>>>
>>>>> Alright, that's as expected. I've tried with your rule and making
>>>>> everything modular, but it still boots fine for me. Very odd. Can you
>>>>> send me your .config? And are all the SCSI disks hanging off ahci? Or
>>>>> sdb specifically, is that ahci or something else?
>>>>
>>>> Also, would be great if you could pull:
>>>>
>>>> git://git.kernel.dk/linux-block blk-mq-sched
>>>>
>>>> into current 'master' and see if it still reproduces. I expect that it
>>>> will, but just want to ensure that it's a problem in the current code
>>>> base as well.
>>>>
>>> Actually, it doesn't. Seems to have resolved itself with the latest drop.
>>>
>>> However, not I've got a lockdep splat:
>>>
>>> Jan 16 09:05:02 lammermuir kernel: ------------[ cut here ]------------
>>> Jan 16 09:05:02 lammermuir kernel: WARNING: CPU: 29 PID: 5860 at
>>> kernel/locking/lockdep.c:3514 lock_release+0x2a7/0x490
>>> Jan 16 09:05:02 lammermuir kernel: DEBUG_LOCKS_WARN_ON(depth <= 0)
>>> Jan 16 09:05:02 lammermuir kernel: Modules linked in: raid0 mpt3sas
>>> raid_class rpcsec_gss_krb5 auth_rpcgss nfsv4 nfs lockd grace fscache e
>>> Jan 16 09:05:02 lammermuir kernel:  fb_sys_fops ahci uhci_hcd ttm
>>> ehci_pci libahci ehci_hcd serio_raw crc32c_intel drm libata usbcore hpsa
>>> Jan 16 09:05:02 lammermuir kernel: CPU: 29 PID: 5860 Comm: fio Not
>>> tainted 4.10.0-rc3+ #540
>>> Jan 16 09:05:02 lammermuir kernel: Hardware name: HP ProLiant ML350p
>>> Gen8, BIOS P72 09/08/2013
>>> Jan 16 09:05:02 lammermuir kernel: Call Trace:
>>> Jan 16 09:05:02 lammermuir kernel:  dump_stack+0x85/0xc9
>>> Jan 16 09:05:02 lammermuir kernel:  __warn+0xd1/0xf0
>>> Jan 16 09:05:02 lammermuir kernel:  ? aio_write+0x118/0x170
>>> Jan 16 09:05:02 lammermuir kernel:  warn_slowpath_fmt+0x4f/0x60
>>> Jan 16 09:05:02 lammermuir kernel:  lock_release+0x2a7/0x490
>>> Jan 16 09:05:02 lammermuir kernel:  ? blkdev_write_iter+0x89/0xd0
>>> Jan 16 09:05:02 lammermuir kernel:  aio_write+0x138/0x170
>>> Jan 16 09:05:02 lammermuir kernel:  do_io_submit+0x4d2/0x8f0
>>> Jan 16 09:05:02 lammermuir kernel:  ? do_io_submit+0x413/0x8f0
>>> Jan 16 09:05:02 lammermuir kernel:  SyS_io_submit+0x10/0x20
>>> Jan 16 09:05:02 lammermuir kernel:  entry_SYSCALL_64_fastpath+0x23/0xc6
>>
>> Odd, not sure that's me. What did you pull my branch into? And what is the
>> sha of the stuff you pulled in?
> 
> Forgot to ask, please send me the fio job you ran here.

Nevermind, it's a mainline bug that's fixed in -rc4:

commit a12f1ae61c489076a9aeb90bddca7722bf330df3
Author: Shaohua Li <shli@...com>
Date:   Tue Dec 13 12:09:56 2016 -0800

    aio: fix lock dep warning

-- 
Jens Axboe