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SubjectRe: [REGRESSION] bfq probe failed on 4.19-rc3
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On 9/12/18 2:58 AM, Takashi Iwai wrote:
> On Tue, 11 Sep 2018 18:54:19 +0200,
> Jens Axboe wrote:
>>
>> On 9/11/18 10:51 AM, Jeff Moyer wrote:
>>> Jens Axboe <axboe@kernel.dk> writes:
>>>
>>>> On 9/11/18 10:48 AM, Jeff Moyer wrote:
>>>>> Jens Axboe <axboe@kernel.dk> writes:
>>>>>
>>>>>> On 9/11/18 10:03 AM, Takashi Iwai wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> I noticed that bfq doesn't appear in the I/O scheduler list on
>>>>>>> 4.19-rc3. It seems that blkcg_policy_register() at the beginning of
>>>>>>> bfq_init() returns -ENOSPC, hence the probe aborts silently.
>>>>>>>
>>>>>>> Is this already addressed?
>>>>>>
>>>>>> Haven't heard about this one before. What kernel did you last use that
>>>>>> worked?
>>>>>
>>>>> I'm guessing you just need to update the maximum number of policies:
>>>>>
>>>>> /*
>>>>> * Maximum number of blkcg policies allowed to be registered concurrently.
>>>>> * Defined here to simplify include dependency.
>>>>> */
>>>>> #define BLKCG_MAX_POLS 3
>>>>
>>>> That is my guess too, hence the suggestion to try and disable the
>>>> iolatency policy. Just tried here without, and it works, rebooting
>>>> with to verify that we're running out of policy slots.
>>>
>>> Functions calling this function: blkcg_policy_register
>>>
>>> File Function Line
>>> 0 block/bfq-iosched.c bfq_init 5675 ret =
>>> blkcg_policy_register(&blkcg_pol
>>> icy_bfq);
>>> 1 block/blk-iolatency.c iolatency_init 946 return
>>> blkcg_policy_register(&blkcg_pol
>>> icy_iolatency);
>>> 2 block/blk-throttle.c throtl_init 2511 return
>>> blkcg_policy_register(&blkcg_pol
>>> icy_throtl);
>>> 3 block/cfq-iosched.c cfq_init 4869 ret =
>>> blkcg_policy_register(&blkcg_pol
>>> icy_cfq);
>>>
>>> And then there were 4...
>>
>> Exactly. I'd bump it to 5 to leave room for one more, if we have to grow it
>> again, probably worth it to make it dynamic. So for, not really needed. Takashi,
>> can verify that the below fixes it up for you?
>
> Yes, it works.
>
> Tested-by: Takashi Iwai <tiwai@suse.de>

Thanks for verifying (and reporting), I'll get this in for 4.19-rc4.

--
Jens Axboe

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