Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley
        Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United
        Kingdom.
        Registered in England and Wales under Company Registration No. 3798903
From:   David Howells <dhowells@redhat.com>
In-Reply-To: <1b1eb3d8-c6b4-b264-1baa-1b3eb088173d@redhat.com>
References: <1b1eb3d8-c6b4-b264-1baa-1b3eb088173d@redhat.com> <20230123173007.325544-1-dhowells@redhat.com> <20230123173007.325544-3-dhowells@redhat.com>
To:     David Hildenbrand <david@redhat.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>,
        John Hubbard <jhubbard@nvidia.com>, linux-mm@kvack.org
Subject: Re: [PATCH v8 02/10] iov_iter: Add a function to extract a page list from an iterator
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <874092.1674570959.1@warthog.procyon.org.uk>
Content-Transfer-Encoding: quoted-printable
Date:   Tue, 24 Jan 2023 14:35:59 +0000
Message-ID: <874093.1674570959@warthog.procyon.org.uk>
Precedence: bulk

David Hildenbrand <david@redhat.com> wrote:

> > +#define iov_iter_extract_mode(iter) (user_backed_iter(iter) ? FOLL_PI=
N : 0)
> > +
> =

> Does it make sense to move that to the patch where it is needed? (do we =
need
> it at all anymore?)

Yes, we need something.  Granted, there are now only two alternatives, not
three: either the pages are going to be pinned or they're not going to be
pinned, but I would rather have a specific function that tells you than ju=
st
use, say, user_backed_iter() to make it easier to adjust it later if we ne=
ed
to - and easier to find the places where we need to adjust.

But if it's preferred we could require people to use user_backed_iter()
instead.

David