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Date:   Wed, 17 Apr 2019 10:07:01 -0400
From:   "Theodore Ts'o" <>
To:     Eric Biggers <>
        Sarthak Kukreti <>,
        Gao Xiang <>
Subject: Re: [PATCH v2 4/5] fscrypt: only set dentry_operations on ciphertext

On Wed, Mar 20, 2019 at 11:39:12AM -0700, Eric Biggers wrote:
> From: Eric Biggers <>
> Plaintext dentries are always valid, so only set fscrypt_d_ops on
> ciphertext dentries.
> Besides marginally improved performance, this allows overlayfs to use an
> fscrypt-encrypted upperdir, provided that all the following are true:
>     (1) The fscrypt encryption key is placed in the keyring before
> 	mounting overlayfs, and remains while the overlayfs is mounted.
>     (2) The overlayfs workdir uses the same encryption policy.
>     (3) No dentries for the ciphertext names of subdirectories have been
> 	created in the upperdir or workdir yet.  (Since otherwise
> 	d_splice_alias() will reuse the old dentry with ->d_op set.)
> One potential use case is using an ephemeral encryption key to encrypt
> all files created or changed by a container, so that they can be
> securely erased ("crypto-shredded") after the container stops.
> Signed-off-by: Eric Biggers <>

Looks good, applied.

					- Ted

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