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Message-ID: <CACOAw_wAYCmpzRA=uXWFSTNrsMFcctJ7Ee1HUf0HmjfTFmPFdw@mail.gmail.com>
Date: Tue, 9 Jun 2020 10:30:23 +0900
From: Daeho Jeong <daeho43@...il.com>
To: Chao Yu <yuchao0@...wei.com>
Cc: Jaegeuk Kim <jaegeuk@...nel.org>,
Daeho Jeong <daehojeong@...gle.com>, kernel-team@...roid.com,
linux-kernel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH] f2fs: add F2FS_IOC_TRIM_FILE ioctl
Like the discussion, I'll add a flag to select discard and/or zero out.
We need to send the discard first between those, because we'll send
the discard to a zero-ed new block, if we zero out first.
2020년 6월 9일 (화) 오전 10:16, Chao Yu <yuchao0@...wei.com>님이 작성:
>
> On 2020/6/8 21:07, Jaegeuk Kim wrote:
> > On 06/08, Chao Yu wrote:
> >> On 2020/6/8 15:19, Daeho Jeong wrote:
> >>> Yes, I agree with you about each vendor has different implementation on discard.
> >>> So, we might be gonna use the combination of zeroing and send discards
> >>> for a more
> >>> secure solution. :)
> >>
> >> IIRC, current solution is:
> >>
> >> - pin file
> >> - get all block addresses of file
> >> - write zero to block addresses
> >> - issue discard
> >>
> >> Is that correct?
> >>
> >> Could we handle those logic (zero out & discard) in new interface
> >> (may be named as {F2FS,EXT4}_IOC_SEC_TRIM_FILE)? then userspace logic
> >> could be quite simple later, and also memcpy could be avoid to make
> >> destruction process more efficient.
> >
> > What about adding a flag to determine calling unmap and/or zero out?
>
> Better. :)
>
> Thanks,
>
> >
> >>
> >> Just raw proposal. :)
> >>
> >> Thanks,
> >>
> >>> I think we still need a discard interface to unmap from the mapping
> >>> table of the storage device side.
> >>>
> >>> Thanks,
> >>>
> >>> 2020년 6월 8일 (월) 오후 3:57, Chao Yu <yuchao0@...wei.com>님이 작성:
> >>>>
> >>>> On 2020/6/8 11:36, Daeho Jeong wrote:
> >>>>> Yes, this is for security key destruction.
> >>>>>
> >>>>> AFAIK, discard will unmap the data block and, after done it,
> >>>>> we can read either zero data or garbage data from that block depending
> >>>>> on eMMC/UFS.
> >>>>
> >>>> Since spec didn't restrict how vendor implement the erase interface, so
> >>>> in order to enhance performance of discard interface, vendor could implement
> >>>> it as an async one, which may not zero mapping entry(L1 table), instead, it
> >>>> could set related bitmap to invalid that mapping entry, than later if device
> >>>> allow user to access that invalid mapping entry, key info may be explosed,
> >>>>
> >>>> It's completely up to how vendor implement the interface, so I think there is
> >>>> still risk to use discard.
> >>>>
> >>>> Thanks,
> >>>>
> >>>>> In a view point of read data, it might be the same with zeroing the data block.
> >>>>> However, since we can even unmap that block, I believe discard is
> >>>>> safer than zeroing out.
> >>>>>
> >>>>> 2020년 6월 8일 (월) 오전 11:46, Chao Yu <yuchao0@...wei.com>님이 작성:
> >>>>>>
> >>>>>> On 2020/6/5 12:27, Daeho Jeong wrote:
> >>>>>>> From: Daeho Jeong <daehojeong@...gle.com>
> >>>>>>>
> >>>>>>> Added a new ioctl to send discard commands to whole data area of
> >>>>>>> a regular file for security reason.
> >>>>>>
> >>>>>> I guess this interface is introduced for security key destruction, if I'm
> >>>>>> right, however, IIRC, discard(erase) semantics in eMMC/UFS spec won't
> >>>>>> guarantee that data which was discard could be zeroed out, so after discard,
> >>>>>> the key still have risk of exposure. So instead, should we use sb_issue_zeroout()?
> >>>>>>
> >>>>>> Thanks,
> >>>>>>
> >>>>>>>
> >>>>>>> Signed-off-by: Daeho Jeong <daehojeong@...gle.com>
> >>>>>>> ---
> >>>>>>> fs/f2fs/f2fs.h | 1 +
> >>>>>>> fs/f2fs/file.c | 129 +++++++++++++++++++++++++++++++++++++++++++++++++
> >>>>>>> 2 files changed, 130 insertions(+)
> >>>>>>>
> >>>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> >>>>>>> index c812fb8e2d9c..9ae81d0fefa0 100644
> >>>>>>> --- a/fs/f2fs/f2fs.h
> >>>>>>> +++ b/fs/f2fs/f2fs.h
> >>>>>>> @@ -434,6 +434,7 @@ static inline bool __has_cursum_space(struct f2fs_journal *journal,
> >>>>>>> _IOR(F2FS_IOCTL_MAGIC, 18, __u64)
> >>>>>>> #define F2FS_IOC_RESERVE_COMPRESS_BLOCKS \
> >>>>>>> _IOR(F2FS_IOCTL_MAGIC, 19, __u64)
> >>>>>>> +#define F2FS_IOC_TRIM_FILE _IO(F2FS_IOCTL_MAGIC, 20)
> >>>>>>>
> >>>>>>> #define F2FS_IOC_GET_VOLUME_NAME FS_IOC_GETFSLABEL
> >>>>>>> #define F2FS_IOC_SET_VOLUME_NAME FS_IOC_SETFSLABEL
> >>>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> >>>>>>> index dfa1ac2d751a..58507bb5649c 100644
> >>>>>>> --- a/fs/f2fs/file.c
> >>>>>>> +++ b/fs/f2fs/file.c
> >>>>>>> @@ -3749,6 +3749,132 @@ static int f2fs_reserve_compress_blocks(struct file *filp, unsigned long arg)
> >>>>>>> return ret;
> >>>>>>> }
> >>>>>>>
> >>>>>>> +static int f2fs_trim_file(struct file *filp)
> >>>>>>> +{
> >>>>>>> + struct inode *inode = file_inode(filp);
> >>>>>>> + struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> >>>>>>> + struct address_space *mapping = inode->i_mapping;
> >>>>>>> + struct bio *bio = NULL;
> >>>>>>> + struct block_device *prev_bdev = NULL;
> >>>>>>> + loff_t file_size;
> >>>>>>> + pgoff_t index, pg_start = 0, pg_end;
> >>>>>>> + block_t prev_block = 0, len = 0;
> >>>>>>> + int ret = 0;
> >>>>>>> +
> >>>>>>> + if (!f2fs_hw_support_discard(sbi))
> >>>>>>> + return -EOPNOTSUPP;
> >>>>>>> +
> >>>>>>> + if (!S_ISREG(inode->i_mode) || f2fs_is_atomic_file(inode) ||
> >>>>>>> + f2fs_compressed_file(inode))
> >>>>>>> + return -EINVAL;
> >>>>>>> +
> >>>>>>> + if (f2fs_readonly(sbi->sb))
> >>>>>>> + return -EROFS;
> >>>>>>> +
> >>>>>>> + ret = mnt_want_write_file(filp);
> >>>>>>> + if (ret)
> >>>>>>> + return ret;
> >>>>>>> +
> >>>>>>> + inode_lock(inode);
> >>>>>>> +
> >>>>>>> + file_size = i_size_read(inode);
> >>>>>>> + if (!file_size)
> >>>>>>> + goto err;
> >>>>>>> + pg_end = (pgoff_t)round_up(file_size, PAGE_SIZE) >> PAGE_SHIFT;
> >>>>>>> +
> >>>>>>> + ret = f2fs_convert_inline_inode(inode);
> >>>>>>> + if (ret)
> >>>>>>> + goto err;
> >>>>>>> +
> >>>>>>> + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> >>>>>>> + down_write(&F2FS_I(inode)->i_mmap_sem);
> >>>>>>> +
> >>>>>>> + ret = filemap_write_and_wait(mapping);
> >>>>>>> + if (ret)
> >>>>>>> + goto out;
> >>>>>>> +
> >>>>>>> + truncate_inode_pages(mapping, 0);
> >>>>>>> +
> >>>>>>> + for (index = pg_start; index < pg_end;) {
> >>>>>>> + struct dnode_of_data dn;
> >>>>>>> + unsigned int end_offset;
> >>>>>>> +
> >>>>>>> + set_new_dnode(&dn, inode, NULL, NULL, 0);
> >>>>>>> + ret = f2fs_get_dnode_of_data(&dn, index, LOOKUP_NODE);
> >>>>>>> + if (ret)
> >>>>>>> + goto out;
> >>>>>>> +
> >>>>>>> + end_offset = ADDRS_PER_PAGE(dn.node_page, inode);
> >>>>>>> + if (pg_end < end_offset + index)
> >>>>>>> + end_offset = pg_end - index;
> >>>>>>> +
> >>>>>>> + for (; dn.ofs_in_node < end_offset;
> >>>>>>> + dn.ofs_in_node++, index++) {
> >>>>>>> + struct block_device *cur_bdev;
> >>>>>>> + block_t blkaddr = f2fs_data_blkaddr(&dn);
> >>>>>>> +
> >>>>>>> + if (__is_valid_data_blkaddr(blkaddr)) {
> >>>>>>> + if (!f2fs_is_valid_blkaddr(F2FS_I_SB(inode),
> >>>>>>> + blkaddr, DATA_GENERIC_ENHANCE)) {
> >>>>>>> + ret = -EFSCORRUPTED;
> >>>>>>> + goto out;
> >>>>>>> + }
> >>>>>>> + } else
> >>>>>>> + continue;
> >>>>>>> +
> >>>>>>> + cur_bdev = f2fs_target_device(sbi, blkaddr, NULL);
> >>>>>>> + if (f2fs_is_multi_device(sbi)) {
> >>>>>>> + int i = f2fs_target_device_index(sbi, blkaddr);
> >>>>>>> +
> >>>>>>> + blkaddr -= FDEV(i).start_blk;
> >>>>>>> + }
> >>>>>>> +
> >>>>>>> + if (len) {
> >>>>>>> + if (prev_bdev == cur_bdev &&
> >>>>>>> + blkaddr == prev_block + len) {
> >>>>>>> + len++;
> >>>>>>> + } else {
> >>>>>>> + ret = __blkdev_issue_discard(prev_bdev,
> >>>>>>> + SECTOR_FROM_BLOCK(prev_block),
> >>>>>>> + SECTOR_FROM_BLOCK(len),
> >>>>>>> + GFP_NOFS, 0, &bio);
> >>>>>>> + if (ret)
> >>>>>>> + goto out;
> >>>>>>> +> + len = 0;
> >>>>>>> + }
> >>>>>>> + }
> >>>>>>> +
> >>>>>>> + if (!len) {
> >>>>>>> + prev_bdev = cur_bdev;
> >>>>>>> + prev_block = blkaddr;
> >>>>>>> + len = 1;
> >>>>>>> + }
> >>>>>>> + }
> >>>>>>> +
> >>>>>>> + f2fs_put_dnode(&dn);
> >>>>>>> + }
> >>>>>>> +
> >>>>>>> + if (len)
> >>>>>>> + ret = __blkdev_issue_discard(prev_bdev,
> >>>>>>> + SECTOR_FROM_BLOCK(prev_block),
> >>>>>>> + SECTOR_FROM_BLOCK(len),
> >>>>>>> + GFP_NOFS, 0, &bio);
> >>>>>>> +out:
> >>>>>>> + if (bio) {
> >>>>>>> + ret = submit_bio_wait(bio);
> >>>>>>> + bio_put(bio);
> >>>>>>> + }
> >>>>>>> +
> >>>>>>> + up_write(&F2FS_I(inode)->i_mmap_sem);
> >>>>>>> + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> >>>>>>> +err:
> >>>>>>> + inode_unlock(inode);
> >>>>>>> + mnt_drop_write_file(filp);
> >>>>>>> +
> >>>>>>> + return ret;
> >>>>>>> +}
> >>>>>>> +
> >>>>>>> long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
> >>>>>>> {
> >>>>>>> if (unlikely(f2fs_cp_error(F2FS_I_SB(file_inode(filp)))))
> >>>>>>> @@ -3835,6 +3961,8 @@ long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
> >>>>>>> return f2fs_release_compress_blocks(filp, arg);
> >>>>>>> case F2FS_IOC_RESERVE_COMPRESS_BLOCKS:
> >>>>>>> return f2fs_reserve_compress_blocks(filp, arg);
> >>>>>>> + case F2FS_IOC_TRIM_FILE:
> >>>>>>> + return f2fs_trim_file(filp);
> >>>>>>> default:
> >>>>>>> return -ENOTTY;
> >>>>>>> }
> >>>>>>> @@ -4004,6 +4132,7 @@ long f2fs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> >>>>>>> case F2FS_IOC_GET_COMPRESS_BLOCKS:
> >>>>>>> case F2FS_IOC_RELEASE_COMPRESS_BLOCKS:
> >>>>>>> case F2FS_IOC_RESERVE_COMPRESS_BLOCKS:
> >>>>>>> + case F2FS_IOC_TRIM_FILE:
> >>>>>>> break;
> >>>>>>> default:
> >>>>>>> return -ENOIOCTLCMD;
> >>>>>>>
> >>>>> .
> >>>>>
> >>> .
> >>>
> >>
> >>
> >> _______________________________________________
> >> Linux-f2fs-devel mailing list
> >> Linux-f2fs-devel@...ts.sourceforge.net
> >> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
> > .
> >
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