linux-ext4 - Re: [PATCH] ext4: reserve codepoints used by the ext4 encryption feature

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Message-ID: <20150123194125.GC9976@birch.djwong.org>
Date:	Fri, 23 Jan 2015 11:41:25 -0800
From:	"Darrick J. Wong" <darrick.wong@...cle.com>
To:	"Theodore Ts'o" <tytso@....edu>
Cc:	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	mhalcrow@...gle.com, savagaon@...gle.com, muslukhovi@...il.com
Subject: Re: [PATCH] ext4: reserve codepoints used by the ext4 encryption
 feature

On Fri, Jan 23, 2015 at 02:36:21PM -0500, Theodore Ts'o wrote:
> Signed-off-by: Theodore Ts'o <tytso@....edu>
> ---
>  fs/ext4/ext4.h | 17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index a75fba6..b7f393d 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -364,7 +364,8 @@ struct flex_groups {
>  #define EXT4_DIRTY_FL			0x00000100
>  #define EXT4_COMPRBLK_FL		0x00000200 /* One or more compressed clusters */
>  #define EXT4_NOCOMPR_FL			0x00000400 /* Don't compress */
> -#define EXT4_ECOMPR_FL			0x00000800 /* Compression error */
> +	/* nb: was previously EXT2_ECOMPR_FL */
> +#define EXT4_ENCRYPT_FL			0x00000800 /* encrypted file */
>  /* End compression flags --- maybe not all used */
>  #define EXT4_INDEX_FL			0x00001000 /* hash-indexed directory */
>  #define EXT4_IMAGIC_FL			0x00002000 /* AFS directory */
> @@ -421,7 +422,7 @@ enum {
>  	EXT4_INODE_DIRTY	= 8,
>  	EXT4_INODE_COMPRBLK	= 9,	/* One or more compressed clusters */
>  	EXT4_INODE_NOCOMPR	= 10,	/* Don't compress */
> -	EXT4_INODE_ECOMPR	= 11,	/* Compression error */
> +	EXT4_INODE_ENCRYPT	= 11,	/* Compression error */

Encryption error?

>  /* End compression flags --- maybe not all used */
>  	EXT4_INODE_INDEX	= 12,	/* hash-indexed directory */
>  	EXT4_INODE_IMAGIC	= 13,	/* AFS directory */
> @@ -466,7 +467,7 @@ static inline void ext4_check_flag_values(void)
>  	CHECK_FLAG_VALUE(DIRTY);
>  	CHECK_FLAG_VALUE(COMPRBLK);
>  	CHECK_FLAG_VALUE(NOCOMPR);
> -	CHECK_FLAG_VALUE(ECOMPR);
> +	CHECK_FLAG_VALUE(ENCRYPT);
>  	CHECK_FLAG_VALUE(INDEX);
>  	CHECK_FLAG_VALUE(IMAGIC);
>  	CHECK_FLAG_VALUE(JOURNAL_DATA);
> @@ -1043,6 +1044,12 @@ extern void ext4_set_bits(void *bm, int cur, int len);
>  /* Metadata checksum algorithm codes */
>  #define EXT4_CRC32C_CHKSUM		1
>  
> +/* Encryption algorithms */
> +#define EXT4_ENCRYPTION_MODE_INVALID		0
> +#define EXT4_ENCRYPTION_MODE_AES_256_XTS	1
> +#define EXT4_ENCRYPTION_MODE_AES_256_GCM	2
> +#define EXT4_ENCRYPTION_MODE_AES_256_CBC	3
> +
>  /*
>   * Structure of the super block
>   */
> @@ -1156,7 +1163,8 @@ struct ext4_super_block {
>  	__le32	s_grp_quota_inum;	/* inode for tracking group quota */
>  	__le32	s_overhead_clusters;	/* overhead blocks/clusters in fs */
>  	__le32	s_backup_bgs[2];	/* groups with sparse_super2 SBs */
> -	__le32	s_reserved[106];	/* Padding to the end of the block */
> +	__u8	s_encrypt_algos[4];	/* Encryption algorithms in use  */

Does this imply that one can have up to 4 algorithms in use at once?

Are there any other disk format changes that the wiki documentation should be
aware of?

--D

> +	__le32	s_reserved[105];	/* Padding to the end of the block */
>  	__le32	s_checksum;		/* crc32c(superblock) */
>  };
>  
> @@ -1537,6 +1545,7 @@ static inline void ext4_clear_state_flags(struct ext4_inode_info *ei)
>  #define EXT4_FEATURE_INCOMPAT_BG_USE_META_CSUM	0x2000 /* use crc32c for bg */
>  #define EXT4_FEATURE_INCOMPAT_LARGEDIR		0x4000 /* >2GB or 3-lvl htree */
>  #define EXT4_FEATURE_INCOMPAT_INLINE_DATA	0x8000 /* data in inode */
> +#define EXT4_FEATURE_INCOMPAT_ENCRYPT		0x10000
>  
>  #define EXT2_FEATURE_COMPAT_SUPP	EXT4_FEATURE_COMPAT_EXT_ATTR
>  #define EXT2_FEATURE_INCOMPAT_SUPP	(EXT4_FEATURE_INCOMPAT_FILETYPE| \
> -- 
> 2.1.0
> 
> --
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