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Date:   Tue, 25 Aug 2020 02:54:28 +0100
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     John Hubbard <jhubbard@nvidia.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Christoph Hellwig <hch@infradead.org>,
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Subject: Re: [PATCH 0/5] bio: Direct IO: convert to pin_user_pages_fast()
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On Fri, Aug 21, 2020 at 09:20:54PM -0700, John Hubbard wrote:

> Direct IO behavior:
> 
>     ITER_IOVEC:
>         pin_user_pages_fast();
>         break;
> 
>     ITER_KVEC:    // already elevated page refcount, leave alone
>     ITER_BVEC:    // already elevated page refcount, leave alone
>     ITER_PIPE:    // just, no :)

Why?  What's wrong with splice to O_DIRECT file?