Message-ID: <5bc85aff-e21e-ab83-d47a-e7b7c1081ab0@redhat.com>
Date:   Tue, 24 Jan 2023 15:37:43 +0100
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Subject: Re: [PATCH v8 02/10] iov_iter: Add a function to extract a page list
 from an iterator
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To:     David Howells <dhowells@redhat.com>
Cc:     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
References: <1b1eb3d8-c6b4-b264-1baa-1b3eb088173d@redhat.com>
 <20230123173007.325544-1-dhowells@redhat.com>
 <20230123173007.325544-3-dhowells@redhat.com>
 <874093.1674570959@warthog.procyon.org.uk>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
In-Reply-To: <874093.1674570959@warthog.procyon.org.uk>
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On 24.01.23 15:35, David Howells wrote:
> David Hildenbrand <david@redhat.com> wrote:
> 
>>> +#define iov_iter_extract_mode(iter) (user_backed_iter(iter) ? FOLL_PIN : 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 just
> use, say, user_backed_iter() to make it easier to adjust it later if we need
> 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.

At least reduces the occurrences of FOLL_PIN :)

-- 
Thanks,

David / dhildenb