linux-ext4 - Re: [PATCH 2/3] ext4: add support for INLINE_CRYPT

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Date:   Tue, 22 Oct 2019 09:37:16 -0400
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     linux-fscrypt@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, Satya Tangirala <satyat@...gle.com>,
        Paul Crowley <paulcrowley@...gle.com>,
        Paul Lawrence <paullawrence@...gle.com>,
        Jaegeuk Kim <jaegeuk@...nel.org>
Subject: Re: [PATCH 2/3] ext4: add support for INLINE_CRYPT_OPTIMIZED
 encryption policies

On Mon, Oct 21, 2019 at 04:03:54PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@...gle.com>
> 
> INLINE_CRYPT_OPTIMIZED encryption policies have special requirements
> from the filesystem:
> 
> - Inode numbers must never change, even if the filesystem is resized
> - Inode numbers must be <= 32 bits
> - File logical block numbers must be <= 32 bits

You need to guarantee more than this; you also need to guarantee that
the logical block number may not change.  Fortunately, because the
original per-file key scheme used a logical block tweak, we've
prohibited this already, and we didn't relax this restriction for
files encrpyted using DIRECT_KEY.  So it's a requirement which we
already meet, but we should document this requirement explicitly ---
both here and also in Documentations/filesystems/fscrypt.rst.

Otherwise, looks good.  Feel free to add:

Reviewed-by: Theodore Ts'o <tytso@....edu>

						- Ted