linux-kernel - Re: [PATCH 1/2] completion: move blk_wait

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Message-ID: <5f3d434b-e05c-445f-bee5-2bb1f11a5946@kernel.dk>
Date: Thu, 18 Apr 2024 08:30:14 -0600
From: Jens Axboe <axboe@...nel.dk>
To: Christoph Hellwig <hch@...radead.org>,
 Mikulas Patocka <mpatocka@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Mike Snitzer
 <msnitzer@...hat.com>, Damien Le Moal <dlemoal@...nel.org>,
 Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
 Waiman Long <longman@...hat.com>, Guangwu Zhang <guazhang@...hat.com>,
 dm-devel@...ts.linux.dev, linux-block@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] completion: move blk_wait_io to
 kernel/sched/completion.c

On 4/17/24 10:57 PM, Christoph Hellwig wrote:
> On Wed, Apr 17, 2024 at 08:00:22PM +0200, Mikulas Patocka wrote:
>>>> +EXPORT_SYMBOL(wait_for_completion_long_io);
>>>
>>> Urgh, why is it a sane thing to circumvent the hang check timer? 
>>
>> The block layer already does it - the bios can have arbitrary size, so 
>> waiting for them takes arbitrary time.
> 
> And as mentioned the last few times around, I think we want a task
> state to say that task can sleep long or even forever and not propagate
> this hack even further.

It certainly is a hack/work-around, but unless there are a lot more that
should be using something like this, I don't think adding extra core
complexity in terms of a special task state (or per-task flag, at least
that would be easier) is really warranted.

-- 
Jens Axboe