linux-ext4 - Re: [Ext4 Secure Delete 2/7v4] ext4: Secure Delete: Add ext4_ind_hole

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Date:	Fri, 07 Oct 2011 16:10:09 -0700
From:	Allison Henderson <achender@...ux.vnet.ibm.com>
To:	djwong@...ibm.com
CC:	linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [Ext4 Secure Delete 2/7v4] ext4: Secure Delete: Add ext4_ind_hole_lookup
 function

On 10/07/2011 10:47 AM, Darrick J. Wong wrote:
> On Fri, Oct 07, 2011 at 12:11:00AM -0700, Allison Henderson wrote:
>> This patch adds a new ext4_ind_hole_lookup function that
>> will be used to identify and skip over holes during a
>> secure delete operation
>>
>> Signed-off-by: Allison Henderson<achender@...ux.vnet.ibm.com>
>> ---
>> :100644 100644 db54ce4... 5c9f88c... M	fs/ext4/ext4.h
>> :100644 100644 0962642... 2fe9dfd... M	fs/ext4/indirect.c
>> :100644 100644 c4da98a... 9dc8c14... M	fs/ext4/inode.c
>>   fs/ext4/ext4.h     |    5 +++
>>   fs/ext4/indirect.c |    2 +-
>>   fs/ext4/inode.c    |   73 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>>   3 files changed, 79 insertions(+), 1 deletions(-)
>>
>> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
>> index db54ce4..5c9f88c 100644
>> --- a/fs/ext4/ext4.h
>> +++ b/fs/ext4/ext4.h
>> @@ -2241,6 +2241,11 @@ extern int ext4_bio_write_page(struct ext4_io_submit *io,
>>   /* mmp.c */
>>   extern int ext4_multi_mount_protect(struct super_block *, ext4_fsblk_t);
>>
>> +/* indirects.c */
>> +extern int ext4_block_to_path(struct inode *inode,
>> +			ext4_lblk_t i_block,
>> +			ext4_lblk_t offsets[4], int *boundary);
>> +
>>   /* BH_Uninit flag: blocks are allocated but uninitialized on disk */
>>   enum ext4_state_bits {
>>   	BH_Uninit	/* blocks are allocated but uninitialized on disk */
>> diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
>> index 0962642..2fe9dfd 100644
>> --- a/fs/ext4/indirect.c
>> +++ b/fs/ext4/indirect.c
>> @@ -69,7 +69,7 @@ static inline void add_chain(Indirect *p, struct buffer_head *bh, __le32 *v)
>>    * get there at all.
>>    */
>>
>> -static int ext4_block_to_path(struct inode *inode,
>> +int ext4_block_to_path(struct inode *inode,
>>   			      ext4_lblk_t i_block,
>>   			      ext4_lblk_t offsets[4], int *boundary)
>>   {
>> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
>> index c4da98a..9dc8c14 100644
>> --- a/fs/ext4/inode.c
>> +++ b/fs/ext4/inode.c
>> @@ -640,6 +640,79 @@ struct buffer_head *ext4_getblk(handle_t *handle, struct inode *inode,
>>   	return bh;
>>   }
>>
>> +/*
>> + * ext4_in_hole_lookup
>> + *
>> + * Returns the size of the hole located at the given block up to
>> + * the first boundry, or 0 if there is no hole. Returns negative on err.
>
> boundary
>
>> + */
>> +static int ext4_ind_hole_lookup(struct inode *inode, ext4_lblk_t block)
>> +{
>> +	struct super_block *sb = inode->i_sb;
>> +	struct buffer_head *bh;
>> +	ext4_lblk_t offsets[4];
>> +	ext4_lblk_t offset;
>> +	__le32 *children;
>> +	__le32 blk;
>> +	int blocks_to_boundary = 0;
>> +	int depth = 0;
>> +	int hole_size = 0;
>> +	unsigned int i, j;
>> +
>> +	depth = ext4_block_to_path(inode, block, offsets,&blocks_to_boundary);
>> +
>> +	if (depth == 0)
>> +		return 0;
>> +
>> +	offset = offsets[0];
>> +	blk = EXT4_I(inode)->i_data[offset];
>> +	if (blk == 0) {
>> +		for (i = *offsets; i<  EXT4_NDIR_BLOCKS; i++) {
>> +			if (EXT4_I(inode)->i_data[i] == 0)
>> +				hole_size++;
>> +			else
>> +				break;
>> +		}
>> +		return hole_size;
>> +	}
>> +
>> +
>> +	for (j = 1; j<  depth; j++) {
>> +		offset = offsets[j];
>> +		bh = sb_getblk(sb, le32_to_cpu(blk));
>> +		if (unlikely(!bh))
>> +			return -EIO;
>> +
>> +		if (!bh_uptodate_or_lock(bh)) {
>> +			if (bh_submit_read(bh)<  0) {
>> +				put_bh(bh);
>> +				return -EIO;
>> +			}
>> +			/* validate block references */
>> +			if (ext4_check_indirect_blockref(inode, bh)) {
>> +				put_bh(bh);
>> +				return -EIO;
>> +			}
>> +		}
>> +
>> +		blk = ((__le32 *)bh->b_data)[offset];
>> +		/* Reader: end */
>> +		if (blk == 0) {
>> +			children = (__le32 *)(bh->b_data);
>> +			for (i = offset; i<  offset +
>> +					blocks_to_boundary; i++) {
>> +				if (children[i] == 0)
>> +					hole_size++;
>> +				else
>> +					break;
>> +			}
>
> Do you need a put_bh here somewhere?
>
> --D

I think you're right, I will add that in somewhere, thx!

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