Messages in this thread Patch in this message | | | Subject | Re: [f2fs-dev] [PATCH] f2fs: add F2FS_IOC_TRIM_FILE ioctl | From | Chao Yu <> | Date | Mon, 8 Jun 2020 15:43:46 +0800 |
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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.
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@huawei.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@huawei.com>님이 작성: >>>> >>>> On 2020/6/5 12:27, Daeho Jeong wrote: >>>>> From: Daeho Jeong <daehojeong@google.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@google.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; >>>>> >>> . >>> > . >
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