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Date:   Wed, 18 Nov 2020 10:10:59 +0100
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Coly Li <colyli@suse.de>
Cc:     Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
        Tejun Heo <tj@kernel.org>, Josef Bacik <josef@toxicpanda.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Mike Snitzer <snitzer@redhat.com>, dm-devel@redhat.com,
        Richard Weinberger <richard@nod.at>, Jan Kara <jack@suse.com>,
        linux-block@vger.kernel.org, xen-devel@lists.xenproject.org,
        linux-bcache@vger.kernel.org, linux-mtd@lists.infradead.org,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 19/20] bcache: remove a superflous lookup_bdev all
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References: <20201118084800.2339180-1-hch@lst.de>
 <20201118084800.2339180-20-hch@lst.de>
 <e7f826fd-cb9c-b4ab-fae8-dad398c14eed@suse.de>
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On Wed, Nov 18, 2020 at 04:54:51PM +0800, Coly Li wrote:
> On 11/18/20 4:47 PM, Christoph Hellwig wrote:
> > Don't bother to call lookup_bdev for just a slightly different error
> > message without any functional change.
> > 
> > Signed-off-by: Christoph Hellwig <hch@lst.de>ist
> 
> Hi Christoph,
> 
> NACK. This removing error message is frequently triggered and observed,
> and distinct a busy device and an already registered device is important
> (the first one is critical error and second one is not).
> 
> Remove such error message will be a functional regression.

What normal operation causes this error message to be emitted?  And what
can a user do with it?

thanks,

greg k-h