Re: [Ext4 Secure Delete 1/7v4] ext4: Secure Delete: Add new EXT4_SECRM_RANDOM_FL flag

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On 10/07/2011 10:02 AM, Darrick J. Wong wrote:
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@xxxxxxxxxxxxxxxxxx>
---
: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

That's a really good suggestion, and I dont see any reason why it needs to be a hard number like that. I will definitely add that in if we decide to keep the EXT4_SECRM_RANDOM_FL flag. Thx!


  /* 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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