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Date: Wed, 21 May 2025 08:03:57 +0200
From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Nilay Shroff <nilay@linux.ibm.com>, linux-block@vger.kernel.org,
	hch@lst.de, axboe@kernel.dk, sth@linux.ibm.com, gjoyce@ibm.com
Subject: Re: [PATCH] block: fix lock dependency between percpu alloc lock
 and elevator lock
Message-ID: <20250521060357.GA3404@lst.de>
References: <20250520103425.1259712-1-nilay@linux.ibm.com> <aC1Ropdb5x05WCIc@fedora>
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On Wed, May 21, 2025 at 12:08:02PM +0800, Ming Lei wrote:
> Not dig into this implementation, will look into later.
> 
> I guess it should work by extending elv_change_ctx.
> 
> However we have other elevator_queue lifetime issue, that is why
> ->elevator_lock is used almost everywhere.
> 
> Another solution is to move all `sched_data` into 'struct elevator_queue':

With "sched_data" you primarily mean the sched tags here, right?

Anyway, getting scheduler owned items out of the request_queue and into
the elevator data seems like the right thing to do, but it might indeed
be very invasive.