linux-ext4 - Re: ext4 crypto: Do not select from EXT4_FS

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Date:	Sun, 03 May 2015 15:34:14 +0300
From:	Anssi Hannula <anssi.hannula@....fi>
To:	Herbert Xu <herbert@...dor.apana.org.au>
CC:	Theodore Ts'o <tytso@....edu>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	linux-ext4@...r.kernel.org, Michael Halcrow <mhalcrow@...gle.com>
Subject: Re: ext4 crypto: Do not select from EXT4_FS_ENCRYPTION

Hi,

01.05.2015, 03:18, Herbert Xu kirjoitti:
> This patch adds a tristate EXT4_ENCRYPTION to do the selections
> for EXT4_FS_ENCRYPTION because selecting from a bool causes all
> the selected options to be built-in, even if EXT4 itself is a
> module.

Hmm, are you sure?

Since CONFIG_EXT4_FS_ENCRYPTION itself depends on CONFIG_EXT4_FS, the
selector for the selected options becomes (CONFIG_EXT4_FS_ENCRYPTION &&
CONFIG_EXT4_FS && CONFIG_BLOCK).

Per my testing on git master (without this patch), if EXT4_FS=m and
EXT4_FS_ENCRYPTION=y, both "built-in" and "module" options are allowed
for the selected options (checked CONFIG_ENCRYPTED_KEYS myself).

So selector "(A=y && B=m)" results in requirement ">=m", which seems
reasonable (otherwise even just CONFIG_BLOCK=y would force them to y).

Am I missing something or this patch unneeded?


> Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
> 
> diff --git a/fs/ext4/Kconfig b/fs/ext4/Kconfig
> index 18228c2..024f228 100644
> --- a/fs/ext4/Kconfig
> +++ b/fs/ext4/Kconfig
> @@ -64,8 +64,8 @@ config EXT4_FS_SECURITY
>  	  If you are not using a security module that requires using
>  	  extended attributes for file security labels, say N.
>  
> -config EXT4_FS_ENCRYPTION
> -	bool "Ext4 Encryption"
> +config EXT4_ENCRYPTION
> +	tristate "Ext4 Encryption"
>  	depends on EXT4_FS
>  	select CRYPTO_AES
>  	select CRYPTO_CBC
> @@ -81,6 +81,11 @@ config EXT4_FS_ENCRYPTION
>  	  efficient since it avoids caching the encrypted and
>  	  decrypted pages in the page cache.
>  
> +config EXT4_FS_ENCRYPTION
> +	bool
> +	default y
> +	depends on EXT4_ENCRYPTION
> +
>  config EXT4_DEBUG
>  	bool "EXT4 debugging support"
>  	depends on EXT4_FS
> 


-- 
Anssi Hannula
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