linux-kernel - Re: [PATCH 04/10] iov_iter: Add mapping and discard iterator types

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Message-ID: <5764.1537219964@warthog.procyon.org.uk>
Date:   Mon, 17 Sep 2018 22:32:44 +0100
From:   David Howells <dhowells@...hat.com>
To:     Trond Myklebust <trondmy@...merspace.com>
Cc:     dhowells@...hat.com,
        "viro@...IV.linux.org.uk" <viro@...IV.linux.org.uk>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-afs@...ts.infradead.org" <linux-afs@...ts.infradead.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH 04/10] iov_iter: Add mapping and discard iterator types

Trond Myklebust <trondmy@...merspace.com> wrote:

> Another question that is relevant for most networked filesystems
> (including AFS, I believe), is how will you deal with encryption of the
> data you are transmitting? Encrypting and decrypting in-place directly
> in the page cache or in a userspace O_DIRECT mapped buffer might not be
> the best and most secure option, so won't you find yourself wanting to
> copy the data anyway?

For kAFS, the interface between kAFS and AF_RXRPC takes an iterator.

Currently, encryption is done in place on the sk_buffs inside AF_RXRPC, but
the goal I have in mind is to use the crypto operation to replace the copy
between sk_buff and buffer.  This is tricky, however, as the encrypted payload
contains metadata as well as data and on reception I have to read the metadata
to find out how much data there actually is.

David