linux-ext4 - Re: [Ext4 Secure Delete 1/7v4] ext4: Secure Delete: Add new EXT4_SECRM_RANDOM

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Date:	Fri, 7 Oct 2011 10:02:55 -0700
From:	"Darrick J. Wong" <djwong@...ibm.com>
To:	Allison Henderson <achender@...ux.vnet.ibm.com>
Cc:	linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [Ext4 Secure Delete 1/7v4] ext4: Secure Delete: Add new
	EXT4_SECRM_RANDOM_FL flag

On Fri, Oct 07, 2011 at 12:10:59AM -0700, Allison Henderson wrote:
> This patch adds a new attribute flag EXT4_SECRM_RANDOM_FL.
> During a secure delete, this flag will cause blocks to be
> overwritten with random data instead of zeros.
> 
> Signed-off-by: Allison Henderson <achender@...ux.vnet.ibm.com>
> ---
> :100644 100644 e717dfd... db54ce4... M	fs/ext4/ext4.h
>  fs/ext4/ext4.h |    9 ++++++---
>  1 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index e717dfd..db54ce4 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -350,17 +350,18 @@ struct flex_groups {
>  #define EXT4_EXTENTS_FL			0x00080000 /* Inode uses extents */
>  #define EXT4_EA_INODE_FL	        0x00200000 /* Inode used for large EA */
>  #define EXT4_EOFBLOCKS_FL		0x00400000 /* Blocks allocated beyond EOF */
> +#define EXT4_SECRM_RANDOM_FL		0x10000000 /* Use random data instead of zeros */
>  #define EXT4_RESERVED_FL		0x80000000 /* reserved for ext4 lib */
> 
> -#define EXT4_FL_USER_VISIBLE		0x004BDFFF /* User visible flags */
> -#define EXT4_FL_USER_MODIFIABLE		0x004B80FF /* User modifiable flags */
> +#define EXT4_FL_USER_VISIBLE		0x104BDFFF /* User visible flags */
> +#define EXT4_FL_USER_MODIFIABLE		0x104B80FF /* User modifiable flags */

Is there a reason why this #define is 0x104BDFFF instead of a bunch of flags
or'd together in a manner similar to the one below it?

--D
> 
>  /* Flags that should be inherited by new inodes from their parent. */
>  #define EXT4_FL_INHERITED (EXT4_SECRM_FL | EXT4_UNRM_FL | EXT4_COMPR_FL |\
>  			   EXT4_SYNC_FL | EXT4_IMMUTABLE_FL | EXT4_APPEND_FL |\
>  			   EXT4_NODUMP_FL | EXT4_NOATIME_FL |\
>  			   EXT4_NOCOMPR_FL | EXT4_JOURNAL_DATA_FL |\
> -			   EXT4_NOTAIL_FL | EXT4_DIRSYNC_FL)
> +			   EXT4_NOTAIL_FL | EXT4_DIRSYNC_FL | EXT4_SECRM_RANDOM_FL)
> 
>  /* Flags that are appropriate for regular files (all but dir-specific ones). */
>  #define EXT4_REG_FLMASK (~(EXT4_DIRSYNC_FL | EXT4_TOPDIR_FL))
> @@ -407,6 +408,7 @@ enum {
>  	EXT4_INODE_EXTENTS	= 19,	/* Inode uses extents */
>  	EXT4_INODE_EA_INODE	= 21,	/* Inode used for large EA */
>  	EXT4_INODE_EOFBLOCKS	= 22,	/* Blocks allocated beyond EOF */
> +	EXT4_INODE_SECRM_RANDOM = 28,   /* Use random data instead of zeros */
>  	EXT4_INODE_RESERVED	= 31,	/* reserved for ext4 lib */
>  };
> 
> @@ -453,6 +455,7 @@ static inline void ext4_check_flag_values(void)
>  	CHECK_FLAG_VALUE(EXTENTS);
>  	CHECK_FLAG_VALUE(EA_INODE);
>  	CHECK_FLAG_VALUE(EOFBLOCKS);
> +	CHECK_FLAG_VALUE(SECRM_RANDOM);
>  	CHECK_FLAG_VALUE(RESERVED);
>  }
> 
> -- 
> 1.7.1
> 
> --
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