Date:	Fri, 07 Oct 2011 10:07:34 -0700
From:	Allison Henderson <achender@...ux.vnet.ibm.com>
To:	Andreas Dilger <aedilger@...il.com>
CC:	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: Re: [Ext4 Secure Delete 0/7 v4] Ext4 secure delete

On 10/07/2011 08:21 AM, Andreas Dilger wrote:
> On 2011-10-07, at 1:10 AM, Allison Henderson<achender@...ux.vnet.ibm.com>  wrote:
>> Sorry for the delay in getting this next version out.
>> I had some tasks to take care of, and now I'm picking up my
>> secure delete work again. I'm still not quite done yet,
>> but a lot has changed and I wanted to update people so that
>> we have an idea of where its going.  Currently the patch
>> deals with data blocks, meta blocks, directory entries,
>> journal blocks, and also provides an option for secure
>> deleting with random data instead of just zeros.
>> I'm also planning on adding some more patches to
>> deal with inodes and also a mount option that turns
>> on secure delete by default.  Im still not quite done
>> debugging, but Im just sending it out early to get
>> some more eyes on it. Feed back appreciated!  :)
>>
>> v3->v4
>> Added a new file attribute flag EXT4_SECRM_RANDOM_FL
>> This flag causes the secure delete operations to over write
>> blocks with random data instead of zeros.
> 
> Since inode flags are in short supply, and I suspect users that want this want it for all files, this should probably be a superblock flag?
> 
That is a really good point.  The first thing that comes to mind though would be the fact that it is a lot slower when the random flag is on especially for really big files.  So that would be one case where I could imagine a user might want the ability to set different options per file.  But since the flags are a limited resource, I can see where we may not want to spend it so quickly.  I will see if maybe there is some way I can optimize it, but I would like to see more folks weigh in on this topic too.

>> New function ext4_secure_delete_lblks added to walk
>> data blocks and secure delete them before any blocks
>> are removed.
>>
>> Meta blocks are secure deleted before they are
>> released
>>
>> New function added to identify holes in ind files.
>> Used by ext4_secure_delete_lblks to skip over holes
>> during secure delete.
>>
>> Added another list in the journal structure to track
>> journal blocks so that they can be secure deleted later.
>>
>> Added new ext4_secure_delete_jblks that secure deletes
>> journal blocks that were used to journal the specified
>> logical blocks
>>
>> Allison Henderson (7):
>>   ext4: Secure Delete: Add new EXT4_SECRM_RANDOM_FL flag
>>   ext4: Secure Delete: Add ext4_ind_hole_lookup function
>>   ext4: Secure Delete: Add secure delete functions
>>   ext4: Secure Delete: Secure delete file data
>>   ext4: Secure Delete: Secure delete directory entry
>>   ext4: Secure Delete: Secure delete meta data blocks
>>   ext4/jbd2: Secure Delete: Secure delete journal blocks
>>
>> fs/ext4/ext4.h         |   28 +++-
>> fs/ext4/ext4_extents.h |    2 +
>> fs/ext4/extents.c      |   21 +++-
>> fs/ext4/indirect.c     |    2 +-
>> fs/ext4/inode.c        |  391 ++++++++++++++++++++++++++++++++++++++++++++++++
>> fs/ext4/mballoc.c      |    8 +
>> fs/ext4/namei.c        |   64 +++++++-
>> fs/jbd2/commit.c       |    6 +
>> fs/jbd2/journal.c      |  112 ++++++++++++++
>> include/linux/jbd2.h   |   21 +++
>> 10 files changed, 642 insertions(+), 13 deletions(-)
>>
>> --
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