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Message-ID: <20111007180711.GH12447@tux1.beaverton.ibm.com>
Date: Fri, 7 Oct 2011 11:07:11 -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 3/7v4] ext4: Secure Delete: Add secure
delete functions
On Fri, Oct 07, 2011 at 12:11:01AM -0700, Allison Henderson wrote:
> This patch adds two new routines: ext4_secure_delete_pblks
> and ext4_secure_delete_lblks.
>
> ext4_secure_delete_pblks() will write zeros to the specified
> physical blocks or random data if the EXT4_SECRM_RANDOM_FL flag is
> set. If the device supports secure discard, the secure
> discard will be used instead. ext4_secure_delete_lblks handels walking
handles
> the logical blocks of a file and calling ext4_secure_delete_pblks()
> as needed.
>
> Signed-off-by: Allison Henderson <achender@...ux.vnet.ibm.com>
> ---
> v1->v2
> Removed check for discard mount option and replaced with
> check for secure discard and discard_zeroes_data
>
> Added BLKDEV_DISCARD_SECURE to the sb_issue_discard call
>
> v2->v3
> Removed code for discard. A seperate patch will
separate
> be done to add that code in the block layer
>
> v3->v4
> Discard code will be kept in the vfs layer. Code
> for secure delete is now in its own function,
> ext4_secure_delete_pblks and is called
> by a new function ext4_secure_delete_lblks
> before any blocks are released
>
> :100644 100644 5c9f88c... 34f82a1... M fs/ext4/ext4.h
> :100644 100644 095c36f... 10180e3... M fs/ext4/ext4_extents.h
> :100644 100644 57cf568... 40d4e50... M fs/ext4/extents.c
> :100644 100644 9dc8c14... 0a526c4... M fs/ext4/inode.c
> fs/ext4/ext4.h | 5 +
> fs/ext4/ext4_extents.h | 2 +
> fs/ext4/extents.c | 2 +-
> fs/ext4/inode.c | 196 ++++++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 204 insertions(+), 1 deletions(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 5c9f88c..34f82a1 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -2220,6 +2220,11 @@ extern int ext4_map_blocks(handle_t *handle, struct inode *inode,
> struct ext4_map_blocks *map, int flags);
> extern int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> __u64 start, __u64 len);
> +extern int ext4_secure_delete_lblks(struct inode *inode,
> + ext4_lblk_t first_block, unsigned long count);
> +extern int ext4_secure_delete_pblks(struct inode *inode,
> + ext4_fsblk_t block, unsigned long count);
> +
> /* move_extent.c */
> extern int ext4_move_extents(struct file *o_filp, struct file *d_filp,
> __u64 start_orig, __u64 start_donor,
> diff --git a/fs/ext4/ext4_extents.h b/fs/ext4/ext4_extents.h
> index 095c36f..10180e3 100644
> --- a/fs/ext4/ext4_extents.h
> +++ b/fs/ext4/ext4_extents.h
> @@ -290,5 +290,7 @@ extern struct ext4_ext_path *ext4_ext_find_extent(struct inode *, ext4_lblk_t,
> struct ext4_ext_path *);
> extern void ext4_ext_drop_refs(struct ext4_ext_path *);
> extern int ext4_ext_check_inode(struct inode *inode);
> +extern int ext4_ext_check_cache(struct inode *inode, ext4_lblk_t block,
> + struct ext4_ext_cache *ex);
> #endif /* _EXT4_EXTENTS */
>
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 57cf568..40d4e50 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -2034,7 +2034,7 @@ ext4_ext_put_gap_in_cache(struct inode *inode, struct ext4_ext_path *path,
> *
> * Return 0 if cache is invalid; 1 if the cache is valid
> */
> -static int ext4_ext_check_cache(struct inode *inode, ext4_lblk_t block,
> +int ext4_ext_check_cache(struct inode *inode, ext4_lblk_t block,
> struct ext4_ext_cache *ex){
> struct ext4_ext_cache *cex;
> struct ext4_sb_info *sbi;
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 9dc8c14..0a526c4 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -38,6 +38,7 @@
> #include <linux/printk.h>
> #include <linux/slab.h>
> #include <linux/ratelimit.h>
> +#include <linux/random.h>
>
> #include "ext4_jbd2.h"
> #include "xattr.h"
> @@ -713,6 +714,201 @@ static int ext4_ind_hole_lookup(struct inode *inode, ext4_lblk_t block)
> return 0;
> }
>
> +
> +/*
> + * ext4_secure_delete_pblks
> + *
> + * Securely delete physical blocks.
> + * If the devices supports secure discard,
> + * blocks will be discarded. Otherwise
> + * the blocks will be either zeroed or
> + * randomized if the random secure delete
> + * flag is on
The fact that random secure delete produces zeroed blocks on discard devices is
documented somewhere user-visible, right? Just in case someone actually
depends on the randomizing.
> + * inode: The files inode
> + * block: The physical block at which to start deleteing
deleting
> + * count: The number of blocks to delete
> + *
> + * Returns 0 on sucess or negative on error
> + */
> +int ext4_secure_delete_pblks(struct inode *inode, ext4_fsblk_t block,
> + unsigned long count){
> +
> + struct fstrim_range range;
> + ext4_fsblk_t iblock, last_block;
> + struct buffer_head *bh;
> + struct super_block *sb = inode->i_sb;
> + struct request_queue *q = bdev_get_queue(sb->s_bdev);
> + struct ext4_super_block *es = EXT4_SB(inode->i_sb)->s_es;
> + int err = 0;
> +
> + last_block = block + count;
> + /*
> + * Check to see if the device supports secure discard,
> + * And also that read after discard returns zeros
> + */
> + if (blk_queue_secdiscard(q) && q->limits.discard_zeroes_data) {
> + err = sb_issue_discard(sb, block, count,
> + GFP_NOFS, BLKDEV_DISCARD_SECURE);
> + if (err)
> + goto zero_out;
> +
> + range.start = block;
> + range.len = count;
> + range.minlen = 1;
> + err = ext4_trim_fs(sb, &range);
> +
> + if (err)
> + goto zero_out;
> +
> + return 0;
> + }
> +
> + if (EXT4_I(inode)->i_flags & EXT4_SECRM_RANDOM_FL) {
> + for (iblock = block; iblock < last_block; iblock++) {
> + bh = sb_getblk(sb, iblock);
> + get_random_bytes(bh->b_data, bh->b_size);
> + set_buffer_dirty(bh);
> +
> + sync_dirty_buffer(bh);
> + if (buffer_req(bh) && !buffer_uptodate(bh)) {
> + es->s_last_error_block =
> + cpu_to_le64(bh->b_blocknr);
> + ext4_error_inode(inode, __func__,
> + __LINE__, bh->b_blocknr,
> + "IO error syncing itable block");
itable block?
> + err = -EIO;
> + brelse(bh);
> + goto zero_out;
> + }
> + brelse(bh);
> + }
> + return 0;
> + }
> +
> +zero_out:
> + return sb_issue_zeroout(sb, block, count, GFP_NOFS);
> +
> +}
> +
> +/*
> + * ext4_secure_delete_lblks
> + *
> + * Secure deletes the data blocks of a file
> + * starting at the given logical block
> + *
> + * @inode: The files inode
> + * @first_block: Starting logical block
> + * @count: The number of blocks to secure delete
> + *
> + * Returns 0 on sucess or negative on error
> + */
> +int ext4_secure_delete_lblks(struct inode *inode, ext4_lblk_t first_block,
> + unsigned long count){
> + handle_t *handle;
> + struct ext4_map_blocks map;
> + struct ext4_ext_cache cache_ex;
> + ext4_lblk_t num_blocks, max_blocks = 0;
> + ext4_lblk_t last_block = first_block + count;
> + ext4_lblk_t iblock = first_block;
> + int ret, credits, hole_len, err = 0;
> +
> + credits = ext4_writepage_trans_blocks(inode);
> + handle = ext4_journal_start(inode, credits);
> + if (IS_ERR(handle))
> + return PTR_ERR(handle);
> +
> + down_write(&EXT4_I(inode)->i_data_sem);
> + ext4_ext_invalidate_cache(inode);
> + ext4_discard_preallocations(inode);
> +
> + /* Do not allow last_block to wrap when caller passes EXT_MAX_BLOCK */
> + if (last_block < first_block)
> + last_block = EXT_MAX_BLOCKS;
> +
> + while (iblock < last_block) {
> + max_blocks = last_block - iblock;
> + num_blocks = 1;
> + memset(&map, 0, sizeof(map));
> + map.m_lblk = iblock;
> + map.m_len = max_blocks;
> +
> + if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
> + ret = ext4_ext_map_blocks(handle, inode, &map, 0);
> + else
> + ret = ext4_ind_map_blocks(handle, inode, &map, 0);
> +
> + if (ret > 0) {
> + err = ext4_secure_delete_pblks(inode,
> + map.m_pblk, map.m_len);
> + if (err)
> + break;
> + num_blocks = ret;
> + } else if (ret == 0) {
> + if (ext4_test_inode_flag(inode,
> + EXT4_INODE_EXTENTS)) {
> + /*
> + * If map blocks could not find the block,
> + * then it is in a hole. If the hole was
> + * not already cached, then map blocks should
> + * put it in the cache. So we can get the hole
> + * out of the cache
> + */
> + memset(&cache_ex, 0, sizeof(cache_ex));
> + if ((ext4_ext_check_cache(inode, iblock,
> + &cache_ex)) && !cache_ex.ec_start) {
> +
> + /* The hole is cached */
> + num_blocks = cache_ex.ec_block +
> + cache_ex.ec_len - iblock;
> +
> + } else {
> + /* reached EOF of extent file */
> + break;
> + }
> + } else {
> + hole_len = ext4_ind_hole_lookup(inode, iblock);
> +
> + if (hole_len > 0) {
> + /* Skip over the hole */
> + num_blocks = hole_len;
> + } else if (hole_len == 0) {
> + /* No hole, EOF reached */
> + break;
> + } else {
> + /* Hole look up err */
> + err = hole_len;
> + break;
> + }
> + }
> + } else {
> + /* Map blocks error */
> + err = ret;
> + break;
> + }
> +
> + if (num_blocks == 0) {
> + /* This condition should never happen */
> + ext_debug("Block lookup failed");
> + err = -EIO;
> + break;
> + }
> +
> + iblock += num_blocks;
> + }
> +
> + if (IS_SYNC(inode))
> + ext4_handle_sync(handle);
> +
> + up_write(&EXT4_I(inode)->i_data_sem);
> +
> + inode->i_mtime = inode->i_ctime = ext4_current_time(inode);
> + ext4_mark_inode_dirty(handle, inode);
> + ext4_journal_stop(handle);
> +
> + return err;
> +}
> +
> struct buffer_head *ext4_bread(handle_t *handle, struct inode *inode,
> ext4_lblk_t block, int create, int *err)
> {
> --
> 1.7.1
>
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