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From:   David Howells <dhowells@redhat.com>
In-Reply-To: <31f7d71d-0eb9-2250-78c0-2e8f31023c66@nvidia.com>
References: <31f7d71d-0eb9-2250-78c0-2e8f31023c66@nvidia.com> <20230123173007.325544-1-dhowells@redhat.com> <20230123173007.325544-11-dhowells@redhat.com>
To:     John Hubbard <jhubbard@nvidia.com>
Cc:     dhowells@redhat.com, Al Viro <viro@zeniv.linux.org.uk>,
        Christoph Hellwig <hch@infradead.org>,
        Matthew Wilcox <willy@infradead.org>,
        Jens Axboe <axboe@kernel.dk>, "Jan Kara" <jack@suse.cz>,
        Jeff Layton <jlayton@kernel.org>,
        Logan Gunthorpe <logang@deltatee.com>,
        linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, "Christoph Hellwig" <hch@lst.de>,
        linux-mm@kvack.org
Subject: Re: [PATCH v8 10/10] mm: Renumber FOLL_PIN and FOLL_GET down
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Date:   Tue, 24 Jan 2023 07:05:56 +0000
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John Hubbard <jhubbard@nvidia.com> wrote:

> > Renumber FOLL_PIN and FOLL_GET down to bit 0 and 1 respectively so tha=
t
> > they are coincidentally the same as BIO_PAGE_PINNED and BIO_PAGE_REFFE=
D and
> > also so that they can be stored in the bottom two bits of a page point=
er
> > (something I'm looking at for zerocopy socket fragments).
> > (Note that BIO_PAGE_REFFED should probably be got rid of at some point=
,
> > hence why FOLL_PIN is at 0.)
> > Also renumber down the other FOLL_* flags to close the gaps.
> =

> Should we also get these sorted into internal-to-mm and public sets?
> Because Jason (+Cc) again was about to split them apart into
> mm/internal.h [1] and that might make that a little cleaner.

My plan was to push this patch by itself through akpm since it's only an
optimisation and not necessary to the rest of the patches here.

David