linux-kernel - Re: [PATCH -next 1/3] md/raid10: fix improper BUG_ON() in raise

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Date:   Tue, 30 Aug 2022 08:32:04 +0200
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     John Stoffel <john@...ffel.org>
Cc:     Yu Kuai <yukuai1@...weicloud.com>, song@...nel.org,
        linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
        yukuai3@...wei.com, yi.zhang@...wei.com
Subject: Re: [PATCH -next 1/3] md/raid10: fix improper BUG_ON() in
 raise_barrier()

Dear John,


Am 29.08.22 um 21:53 schrieb John Stoffel:
>>>>>> "Yu" == Yu Kuai <yukuai1@...weicloud.com> writes:
> 
> Yu> From: Yu Kuai <yukuai3@...wei.com>

The quoting style is really confusing, as it does not seem to be the 
standard, and a lot of MUAs won’t mark up the citation.

[…]

> Yu> 'conf->barrier' is protected by 'conf->resync_lock', reading
> Yu> 'conf->barrier' without holding the lock is wrong.
> 
> Yu> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> Yu> ---
> Yu>  drivers/md/raid10.c | 2 +-
> Yu>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Yu> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> Yu> index 9117fcdee1be..b70c207f7932 100644
> Yu> --- a/drivers/md/raid10.c
> Yu> +++ b/drivers/md/raid10.c
> Yu> @@ -930,8 +930,8 @@ static void flush_pending_writes(struct r10conf *conf)
>   
> Yu>  static void raise_barrier(struct r10conf *conf, int force)
> Yu>  {
> Yu> -	BUG_ON(force && !conf->barrier);
> Yu>  	spin_lock_irq(&conf->resync_lock);
> Yu> +	BUG_ON(force && !conf->barrier);
> 
> I don't like this BUG_ON() at all, why are you crashing the system
> here instead of just doing a simple WARN_ONCE() instead?  Is there
> anything the user can do to get into this situation on their own, or
> does it really signify a logic error in the code?  If so, why are you
> killing the system?

As you can see, the BUG_ON() was there before, so it’s unrelated to this 
patch and Yun is not killing anything.

[…]


> Yu>  	/* Wait until no block IO is waiting (unless 'force') */
> Yu>  	wait_event_lock_irq(conf->wait_barrier, force || !conf->nr_waiting,
> Yu> --
> Yu> 2.31.1


Kind regards,

Paul