linux-kernel - Re: [PATCH 1/2] block: remove unnecessary ioc nested locking

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Message-ID: <20200623115052.comb37q22kjgzyen@beryllium.lan>
Date:   Tue, 23 Jun 2020 13:50:52 +0200
From:   Daniel Wagner <dwagner@...e.de>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Jens Axboe <axboe@...nel.dk>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] block: remove unnecessary ioc nested locking

On Fri, Jun 19, 2020 at 05:23:17PM +0206, John Ogness wrote:
> The legacy CFQ IO scheduler could call put_io_context() in its exit_icq()
> elevator callback. This led to a lockdep warning, which was fixed in
> commit d8c66c5d5924 ("block: fix lockdep warning on io_context release
> put_io_context()") by using a nested subclass for the ioc spinlock.
> However, with commit f382fb0bcef4 ("block: remove legacy IO schedulers")
> the CFQ IO scheduler no longer exists.
> 
> The BFQ IO scheduler also implements the exit_icq() elevator callback but
> does not call put_io_context().
> 
> The nested subclass for the ioc spinlock is no longer needed. Since it
> existed as an exception and no longer applies, remove the nested subclass
> usage.
> 
> Signed-off-by: John Ogness <john.ogness@...utronix.de>

As far I can tell, looks good.

Reviewed-by: Daniel Wagner <dwagner@...e.de>