On 12/18/2017 02:56 PM, Stefan Haberland wrote:
> On 07.12.2017 00:29, Christoph Hellwig wrote:
>> On Wed, Dec 06, 2017 at 01:25:11PM +0100, Christian Borntraeger wrote:
>> t > commit 11b2025c3326f7096ceb588c3117c7883850c068 -> bad
>>> blk-mq: create a blk_mq_ctx for each possible CPU
>>> does not boot on DASD and
>>> commit 9c6ae239e01ae9a9f8657f05c55c4372e9fc8bcc -> good
>>> genirq/affinity: assign vectors to all possible CPUs
>>> does boot with DASD disks.
>>>
>>> Also adding Stefan Haberland if he has an idea why this fails on DASD and
>>> adding Martin (for the
>>> s390 irq handling code).
>> That is interesting as it really isn't related to interrupts at all,
>> it just ensures that possible CPUs are set in ->cpumask.
>>
>> I guess we'd really want:
>>
>> e005655c389e3d25bf3e43f71611ec12f3012de0
>> "blk-mq: only select online CPUs in blk_mq_hctx_next_cpu"
>>
>> before this commit, but it seems like the whole stack didn't work for
>> your either.
>>
>> I wonder if there is some weird thing about nr_cpu_ids in s390?
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>
> I tried this on my system and the blk-mq-hotplug-fix branch does not boot for
> me as well.
> The disks get up and running and I/O works fine. At least the partition
> detection and EXT4-fs mount works.
>
> But at some point in time the disk do not get any requests.
>
> I currently have no clue why.
> I took a dump and had a look at the disk states and they are fine. No error
> in the logs or in our debug entrys. Just empty DASD devices waiting to be
> called for I/O requests.
>
> Do you have anything I could have a look at?
Jens, Christoph, so what do we do about this?
To summarize:
- commit 4b855ad37194f7 ("blk-mq: Create hctx for each present CPU") broke CPU
hotplug.
- Jens' quick revert did fix the issue and did not broke DASD support but has
some issues
with interrupt affinity.
- Christoph patch set fixes the hotplug issue for virtio blk but causes I/O
hangs on DASDs (even
without hotplug).
Christian
