linux-ext4 - Re: backup/restore of fscrypt files

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Message-ID: <20201130194228.GA1248532@gmail.com>
Date:   Mon, 30 Nov 2020 11:42:28 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     Andreas Dilger <adilger@...ger.ca>
Cc:     Theodore Ts'o <tytso@....edu>, linux-fscrypt@...r.kernel.org,
        Ext4 Developers List <linux-ext4@...r.kernel.org>,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Sebastien Buisson <sbuisson@....com>
Subject: Re: backup/restore of fscrypt files

On Mon, Nov 30, 2020 at 10:39:10AM -0800, Eric Biggers wrote:
> (Allowing only direct I/O on files that don't have encryption key unavailable
> may help...)

It may sense to only provide the ciphertext when reads are done using
RWF_ENCODED
(https://lkml.kernel.org/linux-fsdevel/cover.1605723568.git.osandov@fb.com),
rather than making normal reads return ciphertext when the key is unavailable.

Ciphertext reads would always be uncached, which would avoid two conflicting
uses of the same address_space.

- Eric