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Date:   Tue, 18 Oct 2022 07:26:06 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Dan Williams <dan.j.williams@intel.com>
Cc:     Jason Gunthorpe <jgg@nvidia.com>, linux-mm@kvack.org,
        Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>,
        "Darrick J. Wong" <djwong@kernel.org>,
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        John Hubbard <jhubbard@nvidia.com>, david@fromorbit.com,
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        linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v3 07/25] fsdax: Hold dax lock over mapping insertion
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On Mon, Oct 17, 2022 at 01:17:23PM -0700, Dan Williams wrote:
> Historically, no. The block-device is allowed to disappear while inodes
> are still live.

Btw, while I agree with what you wrote below this sentence is at least
a bit confusing.  Struct block_device/gendisk/request_queue will always
be valid as long as a file system is mounted and inodes are live due
to refcounting.  It's just as you correctly pointed out del_gendisk
might have aready been called and they are dead.