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: <fc18c4c9-09f2-0ca1-8525-5ce671db36c5@redhat.com>
References: <fc18c4c9-09f2-0ca1-8525-5ce671db36c5@redhat.com> <20230123173007.325544-1-dhowells@redhat.com> <20230123173007.325544-4-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>,
        linux-mm@kvack.org
Subject: Re: [PATCH v8 03/10] mm: Provide a helper to drop a pin/ref on a page
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <874545.1674571293.1@warthog.procyon.org.uk>
Content-Transfer-Encoding: quoted-printable
Date:   Tue, 24 Jan 2023 14:41:33 +0000
Message-ID: <874546.1674571293@warthog.procyon.org.uk>
Precedence: bulk

David Hildenbrand <david@redhat.com> wrote:

> > Provide a helper in the get_user_pages code to drop a pin or a ref on =
a
> > page based on being given FOLL_GET or FOLL_PIN in its flags argument o=
r do
> > nothing if neither is set.
> =

> Does the FOLL_GET part still apply to this patch set?

Yes.  Christoph insisted that the bio conversion patch be split up.  That
means there's an interval where you can get FOLL_GET from that.  However,
since Jason wants to hide FOLL_PUT, this is going to have to be removed an=
d
the switching done in the bio code for the bio case (until that reduces to
just pinning) and the skbuff cleanup code (when that is eventually done - =
that
will have the possibility of skbuffs comprising a mix of ref'd, pinned and
unpinned data, albeit in separate fragments; I've posted patches that
illustrate this[1]).

David

https://lore.kernel.org/all/167391047703.2311931.8115712773222260073.stgit=
@warthog.procyon.org.uk/ [1] Patches 33-34