linux-kernel - Re: [PATCH v9 0/3] mm/gup: disallow GUP writing to file-backed mappings by default

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Message-ID: <ZGG/xkIUYK2QMPSv@infradead.org>
Date:   Sun, 14 May 2023 22:14:46 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Lorenzo Stoakes <lstoakes@...il.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jason Gunthorpe <jgg@...pe.ca>, Jens Axboe <axboe@...nel.dk>,
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        Christian Borntraeger <borntraeger@...ux.ibm.com>
Subject: Re: [PATCH v9 0/3] mm/gup: disallow GUP writing to file-backed
 mappings by default

On Sun, May 14, 2023 at 08:20:04PM +0100, Lorenzo Stoakes wrote:
> As discussed at LSF/MM, on the flight over I wrote a little repro [0] which
> reliably triggers the ext4 warning by recreating the scenario described
> above, using a small userland program and kernel module.
> 
> This code is not perfect (plane code :) but does seem to do the job
> adequately, also obviously this should only be run in a VM environment
> where data loss is acceptable (in my case a small qemu instance).

It would be really awesome if you could wire it up with and submit it
to xfstests.