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Date:   Wed, 17 May 2023 00:43:34 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Lorenzo Stoakes <lstoakes@gmail.com>
Cc:     Jan Kara <jack@suse.cz>, Jason Gunthorpe <jgg@nvidia.com>,
        "Kirill A . Shutemov" <kirill@shutemov.name>, linux-mm@kvack.org,
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Subject: Re: [PATCH v9 0/3] mm/gup: disallow GUP writing to file-backed
 mappings by default
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On Wed, May 17, 2023 at 08:40:26AM +0100, Lorenzo Stoakes wrote:
> > I'm not sure what you mean by "total flexibility" here. In my opinion it is
> > also about how HW performs checksumming etc.
> 
> I mean to say *_ops allow a lot of flexibility in how things are
> handled. Certainly checksumming is a great example but in theory an
> arbitrary filesystem could be doing, well, anything and always assuming
> that only userland mappings should be modifying the underlying data.

File systems need a wait to track when a page is dirtied so that it can
be written back.  Not much to do with flexbility.