linux-kernel - Re: [PATCH v2] io_uring: Avoid polling configuration errors

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Message-ID: <db1816bc-c3f4-41c0-8946-f8d4a260216a@kernel.dk>
Date: Fri, 12 Jul 2024 09:36:13 -0600
From: Jens Axboe <axboe@...nel.dk>
To: hexue <xue01.he@...sung.com>, hch@...radead.org
Cc: asml.silence@...il.com, io-uring@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] io_uring: Avoid polling configuration errors

On 7/12/24 12:57 AM, hexue wrote:
>> This is wrong for multiple reasons.  One is that we can't simply poke
>> into block device internals like this in a higher layer like io_uring.
>> Second blkdev_get_no_open is in no way available for use outside the
>> block layer.  The fact that the even exist as separate helpers that
>> aren't entirely hidden is a decade old layering violation in blk-cgroup.
> 
> Got it, thanks.
> 
>> If you want to advertize this properly we'll need a flag in struct
>> file or something similar.
> 
> Thanks, I will try to do this.

My stance is still the same - why add all of this junk just to detect a
misuse of polled IO? It doesn't make sense to me, it's the very
definition of "doctor it hurts when I do this" - don't do it.

So unless this has _zero_ overhead or extra code, which obviously isn't
possible, or extraordinary arguments exists for why this should be
added, I don't see this going anywhere.

-- 
Jens Axboe