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Date:   Wed, 14 Jun 2023 15:46:17 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Jan Kara <jack@suse.cz>
Cc:     Christoph Hellwig <hch@infradead.org>,
        Colin Walters <walters@verbum.org>,
        Bart Van Assche <bvanassche@acm.org>,
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        Dmitry Vyukov <dvyukov@google.com>,
        Theodore Ts'o <tytso@mit.edu>, yebin <yebin@huaweicloud.com>,
        linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] block: Add config option to not allow writing to mounted
 devices
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On Wed, Jun 14, 2023 at 12:12:56PM +0200, Jan Kara wrote:
> Well, OK, I have not been precise :). Modifying a partition table (or LVM
> description block) is impossible to distinguish from clobbering a
> filesystem on open(2) time. Once we decide we implement arbitration of each
> individual write(2), we can obviously stop writes to area covered by some
> exclusively open partition. But then you are getting at the complexity
> level of tracking used ranges of block devices which Darrick has suggested
> and you didn't seem to like that (and neither do I). Furthermore the
> protection is never going to be perfect as soon as loopback devices, device
> mapper, and similar come into the mix (or it gets really really complex).
> So I'd really prefer to stick with whatever arbitration we can perform on
> open(2).

What a shame we got rid of mandatory file locks in f7e33bdbd6d1 ;-)