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Date: Tue, 15 Sep 2026 08:50:44 +0200
From: Christoph Hellwig <hch@lst.de>
To: Nilay Shroff <nilay@linux.ibm.com>
Cc: Yu Kuai <yukuai@kernel.org>, Jens Axboe <axboe@kernel.dk>,
	Josef Bacik <josef@toxicpanda.com>, Tejun Heo <tj@kernel.org>,
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Subject: Re: [PATCH v2 3/3] blk-cgroup: move async bio punt state to blkcg
Message-ID: <20260915065044.GB13417@lst.de>
References: <cover.1789237876.git.yukuai@fygo.io> <326e4904402440323532168095f2eb0c6f697836.1789237877.git.yukuai@fygo.io> <f27ee89f-5a52-4cfc-a14a-e5019ae61d89@linux.ibm.com>
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On Sun, Sep 13, 2026 at 06:59:25PM +0530, Nilay Shroff wrote:
>> +	/* as long as there are pending bios, @blkcg can't go away */
>> +	{
>> +		guard(spinlock)(&blkcg->async_bio_lock);
>> +		bio_list_merge_init(&bios, &blkcg->async_bios);
>> +	}
>>
> Instead of using guard(spinlock)(...) here, I think we could use the
> simpler spin_lock()/spin_unlock() helpers. IMO, they are easier
> to read and reason about for these short critical sections.

Yes, guard() is a complete mess that makes code unreadable, please
don't use it.  scope_guard is a bit better, but given that it doesn't
mix with goto based unwdinding it still is too dangerous to actually
use.