Date:   Tue, 10 Nov 2020 09:52:40 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
CC:     <linux-kernel@...r.kernel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>
Subject: Re: [f2fs-dev] [PATCH] f2fs: compress: support chksum

On 2020/11/10 1:06, Jaegeuk Kim wrote:
> On 11/09, Chao Yu wrote:
>> On 2020/11/7 5:12, Jaegeuk Kim wrote:
>>> On 11/03, Chao Yu wrote:
>>>> On 2020/11/3 10:02, Chao Yu wrote:
>>>>> On 2020/11/3 0:31, Jaegeuk Kim wrote:
>>>>>> On 11/02, Chao Yu wrote:
>>>>>>> This patch supports to store chksum value with compressed
>>>>>>> data, and verify the integrality of compressed data while
>>>>>>> reading the data.
>>>>>>>
>>>>>>> The feature can be enabled through specifying mount option
>>>>>>> 'compress_chksum'.
>>>>>>>
>>>>>>> Signed-off-by: Chao Yu <yuchao0@...wei.com>
>>>>>>> ---
>>>>>>>      Documentation/filesystems/f2fs.rst |  1 +
>>>>>>>      fs/f2fs/compress.c                 | 20 ++++++++++++++++++++
>>>>>>>      fs/f2fs/f2fs.h                     | 13 ++++++++++++-
>>>>>>>      fs/f2fs/inode.c                    |  3 +++
>>>>>>>      fs/f2fs/super.c                    |  9 +++++++++
>>>>>>>      include/linux/f2fs_fs.h            |  2 +-
>>>>>>>      6 files changed, 46 insertions(+), 2 deletions(-)
>>>>>>>
>>>>>>> diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst
>>>>>>> index b8ee761c9922..985ae7d35066 100644
>>>>>>> --- a/Documentation/filesystems/f2fs.rst
>>>>>>> +++ b/Documentation/filesystems/f2fs.rst
>>>>>>> @@ -260,6 +260,7 @@ compress_extension=%s	 Support adding specified extension, so that f2fs can enab
>>>>>>>      			 For other files, we can still enable compression via ioctl.
>>>>>>>      			 Note that, there is one reserved special extension '*', it
>>>>>>>      			 can be set to enable compression for all files.
>>>>>>> +compress_chksum		 Support verifying chksum of raw data in compressed cluster.
>>>>>>>      inlinecrypt		 When possible, encrypt/decrypt the contents of encrypted
>>>>>>>      			 files using the blk-crypto framework rather than
>>>>>>>      			 filesystem-layer encryption. This allows the use of
>>>>>>> diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
>>>>>>> index 14262e0f1cd6..a4e0d2c745b6 100644
>>>>>>> --- a/fs/f2fs/compress.c
>>>>>>> +++ b/fs/f2fs/compress.c
>>>>>>> @@ -602,6 +602,7 @@ static int f2fs_compress_pages(struct compress_ctx *cc)
>>>>>>>      				f2fs_cops[fi->i_compress_algorithm];
>>>>>>>      	unsigned int max_len, new_nr_cpages;
>>>>>>>      	struct page **new_cpages;
>>>>>>> +	u32 chksum = 0;
>>>>>>>      	int i, ret;
>>>>>>>      	trace_f2fs_compress_pages_start(cc->inode, cc->cluster_idx,
>>>>>>> @@ -655,6 +656,11 @@ static int f2fs_compress_pages(struct compress_ctx *cc)
>>>>>>>      	cc->cbuf->clen = cpu_to_le32(cc->clen);
>>>>>>> +	if (fi->i_compress_flag & 1 << COMPRESS_CHKSUM)
>>>>>>> +		chksum = f2fs_crc32(F2FS_I_SB(cc->inode),
>>>>>>> +					cc->cbuf->cdata, cc->clen);
>>>>>>> +	cc->cbuf->chksum = cpu_to_le32(chksum);
>>>>>>> +
>>>>>>>      	for (i = 0; i < COMPRESS_DATA_RESERVED_SIZE; i++)
>>>>>>>      		cc->cbuf->reserved[i] = cpu_to_le32(0);
>>>>>>> @@ -721,6 +727,7 @@ void f2fs_decompress_pages(struct bio *bio, struct page *page, bool verity)
>>>>>>>      			(struct decompress_io_ctx *)page_private(page);
>>>>>>>      	struct f2fs_sb_info *sbi = F2FS_I_SB(dic->inode);
>>>>>>>      	struct f2fs_inode_info *fi= F2FS_I(dic->inode);
>>>>>>> +	struct f2fs_sb_info *sbi = F2FS_I_SB(dic->inode);
>>>>>>>      	const struct f2fs_compress_ops *cops =
>>>>>>>      			f2fs_cops[fi->i_compress_algorithm];
>>>>>>>      	int ret;
>>>>>>> @@ -790,6 +797,19 @@ void f2fs_decompress_pages(struct bio *bio, struct page *page, bool verity)
>>>>>>>      	ret = cops->decompress_pages(dic);
>>>>>>> +	if (!ret && fi->i_compress_flag & 1 << COMPRESS_CHKSUM) {
>>>>>>> +		u32 provided = le32_to_cpu(dic->cbuf->chksum);
>>>>>>> +		u32 calculated = f2fs_crc32(sbi, dic->cbuf->cdata, dic->clen);
>>>>>>> +
>>>>>>> +		if (provided != calculated) {
>>>>>>> +			printk_ratelimited(
>>>>>>> +				"%sF2FS-fs (%s): checksum invalid, nid = %lu, %x vs %x",
>>>>>>> +				KERN_INFO, sbi->sb->s_id, dic->inode->i_ino,
>>>>>>> +				provided, calculated);
>>>>>>> +			ret = -EFSCORRUPTED;
>>>>>>
>>>>>> Do we need to change fsck.f2fs to recover this?
>>>>
>>>> However, we don't know which one is correct, compressed data or chksum value?
>>>> if compressed data was corrupted, repairing chksum value doesn't help.
>>>>
>>>> Or how about adding chksum values for both raw data and compressed data.
>>>>
>>>> #define COMPRESS_DATA_RESERVED_SIZE	3
>>>> struct compress_data {
>>>> 	__le32 clen;			/* compressed data size */
>>>> +	__le32 raw_chksum;		/* raw data chksum */
>>>> +	__le32 compress_chksum;		/* compressed data chksum */
>>>> 	__le32 reserved[COMPRESS_DATA_RESERVED_SIZE];	/* reserved */
>>>> 	u8 cdata[];			/* compressed data */
>>>> };
>>>>
>>>> 	raw_chksum	compress_chksum
>>>> 	match		match			-> data is verified, pass
>>>> 	not match	match			-> repair raw_chksum
>>>> 	matcth		not match		-> repair compress_chksum
>>>
>>> I think only compress_chksum would be enough. BTW, can we give WARN_ON and
>>> marking a FSCK flag without returning EFSCORRUPTED, since we don't really
>>> know who was corrupted. If data was corrupted, we should be able to see app
>>> corruption. In that case, we can check the kernel log. If checksum was simply
>>
>> I don't think that app will always corrupt once data was corrupted, I doubt its
>> behavior could be slightly abnormal in some cases, e.g. it can just cause apps to
>> show wrong number in interaction interface.
> 
> I didn't say we can always get it. But, it's likely to happen with something
> like that.
> 
>>
>> In this case, if we fix chksum in fsck, the wrong data will never be found due to
>> data's chksum matches data itself after repair.
> 
> At least, we should see that log as a hint.
> 
>>
>> IMO, the chksum and data was a whole dataset, once they are mismatch, we can
>> not trust either of them, fsck should do nothing on them unless we store parity
>> bits or replica.
> 
> Yeah, the point is those are not written as a transaction. Three concerns to me:

Just to confirm:

> 1) agreed to see compressed data corruption by checksum

return EFSBADCRC always like we did as inode chksum feature.

2) I don't want to see the error messages all the time

Something like below?

if (provided != calculated) {
	if (!is_inode_flag_set(,FI_DATA_CORRUPTED)) {
		printk_ratelimited();
		WARN_ON()
		set_inode_flag(, FI_DATA_CORRUPTED);
	}
	return EFSBADCRC;
}

3) don't touch the data, even if it was corrupted, since there's no way to fix it.

It seems that we don't need to change fsck.f2fs finally...

Thanks,

> 
>>
>> Thanks,
>>
>>> corrupted, next fsck will fix the checksum. So, in general, I hope to keep
>>> the data as is and raise a flag by the checksum.
>>>
>>>> 	not match	not match		-> corrupted, can not repair
>>>>
>>>> Thanks,
>>>>
>>>>>
>>>>> Yes, prepared to update inode layout in fsck.f2fs w/ kernel side change. >
>>>>> Thanks,
>>>>>
>>>>>>
>>>>>>> +		}
>>>>>>> +	}
>>>>>>> +
>>>>>>>      out_vunmap_cbuf:
>>>>>>>      	vm_unmap_ram(dic->cbuf, dic->nr_cpages);
>>>>>>>      out_vunmap_rbuf:
>>>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>>>> index 99bcf4b44a9c..2ae254ab7b7d 100644
>>>>>>> --- a/fs/f2fs/f2fs.h
>>>>>>> +++ b/fs/f2fs/f2fs.h
>>>>>>> @@ -147,7 +147,8 @@ struct f2fs_mount_info {
>>>>>>>      	/* For compression */
>>>>>>>      	unsigned char compress_algorithm;	/* algorithm type */
>>>>>>> -	unsigned compress_log_size;		/* cluster log size */
>>>>>>> +	unsigned char compress_log_size;	/* cluster log size */
>>>>>>> +	bool compress_chksum;			/* compressed data chksum */
>>>>>>>      	unsigned char compress_ext_cnt;		/* extension count */
>>>>>>>      	unsigned char extensions[COMPRESS_EXT_NUM][F2FS_EXTENSION_LEN];	/* extensions */
>>>>>>>      };
>>>>>>> @@ -731,6 +732,7 @@ struct f2fs_inode_info {
>>>>>>>      	atomic_t i_compr_blocks;		/* # of compressed blocks */
>>>>>>>      	unsigned char i_compress_algorithm;	/* algorithm type */
>>>>>>>      	unsigned char i_log_cluster_size;	/* log of cluster size */
>>>>>>> +	unsigned short i_compress_flag;		/* compress flag */
>>>>>>>      	unsigned int i_cluster_size;		/* cluster size */
>>>>>>>      };
>>>>>>> @@ -1270,9 +1272,15 @@ enum compress_algorithm_type {
>>>>>>>      	COMPRESS_MAX,
>>>>>>>      };
>>>>>>> +enum compress_flag {
>>>>>>> +	COMPRESS_CHKSUM,
>>>>>>> +	COMPRESS_MAX_FLAG,
>>>>>>> +};
>>>>>>> +
>>>>>>>      #define COMPRESS_DATA_RESERVED_SIZE		5
>>>>>>>      struct compress_data {
>>>>>>>      	__le32 clen;			/* compressed data size */
>>>>>>> +	__le32 chksum;			/* compressed data chksum */
>>>>>>>      	__le32 reserved[COMPRESS_DATA_RESERVED_SIZE];	/* reserved */
>>>>>>>      	u8 cdata[];			/* compressed data */
>>>>>>>      };
>>>>>>> @@ -3882,6 +3890,9 @@ static inline void set_compress_context(struct inode *inode)
>>>>>>>      			F2FS_OPTION(sbi).compress_algorithm;
>>>>>>>      	F2FS_I(inode)->i_log_cluster_size =
>>>>>>>      			F2FS_OPTION(sbi).compress_log_size;
>>>>>>> +	F2FS_I(inode)->i_compress_flag =
>>>>>>> +			F2FS_OPTION(sbi).compress_chksum ?
>>>>>>> +				1 << COMPRESS_CHKSUM : 0;
>>>>>>>      	F2FS_I(inode)->i_cluster_size =
>>>>>>>      			1 << F2FS_I(inode)->i_log_cluster_size;
>>>>>>>      	F2FS_I(inode)->i_flags |= F2FS_COMPR_FL;
>>>>>>> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
>>>>>>> index 657db2fb6739..de8f7fc89efa 100644
>>>>>>> --- a/fs/f2fs/inode.c
>>>>>>> +++ b/fs/f2fs/inode.c
>>>>>>> @@ -456,6 +456,7 @@ static int do_read_inode(struct inode *inode)
>>>>>>>      					le64_to_cpu(ri->i_compr_blocks));
>>>>>>>      			fi->i_compress_algorithm = ri->i_compress_algorithm;
>>>>>>>      			fi->i_log_cluster_size = ri->i_log_cluster_size;
>>>>>>> +			fi->i_compress_flag = ri->i_compress_flag;
>>>>>>>      			fi->i_cluster_size = 1 << fi->i_log_cluster_size;
>>>>>>>      			set_inode_flag(inode, FI_COMPRESSED_FILE);
>>>>>>>      		}
>>>>>>> @@ -634,6 +635,8 @@ void f2fs_update_inode(struct inode *inode, struct page *node_page)
>>>>>>>      					&F2FS_I(inode)->i_compr_blocks));
>>>>>>>      			ri->i_compress_algorithm =
>>>>>>>      				F2FS_I(inode)->i_compress_algorithm;
>>>>>>> +			ri->i_compress_flag =
>>>>>>> +				cpu_to_le16(F2FS_I(inode)->i_compress_flag);
>>>>>>>      			ri->i_log_cluster_size =
>>>>>>>      				F2FS_I(inode)->i_log_cluster_size;
>>>>>>>      		}
>>>>>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>>>>>>> index 00eff2f51807..f8de4d83a5be 100644
>>>>>>> --- a/fs/f2fs/super.c
>>>>>>> +++ b/fs/f2fs/super.c
>>>>>>> @@ -146,6 +146,7 @@ enum {
>>>>>>>      	Opt_compress_algorithm,
>>>>>>>      	Opt_compress_log_size,
>>>>>>>      	Opt_compress_extension,
>>>>>>> +	Opt_compress_chksum,
>>>>>>>      	Opt_atgc,
>>>>>>>      	Opt_err,
>>>>>>>      };
>>>>>>> @@ -214,6 +215,7 @@ static match_table_t f2fs_tokens = {
>>>>>>>      	{Opt_compress_algorithm, "compress_algorithm=%s"},
>>>>>>>      	{Opt_compress_log_size, "compress_log_size=%u"},
>>>>>>>      	{Opt_compress_extension, "compress_extension=%s"},
>>>>>>> +	{Opt_compress_chksum, "compress_chksum"},
>>>>>>>      	{Opt_atgc, "atgc"},
>>>>>>>      	{Opt_err, NULL},
>>>>>>>      };
>>>>>>> @@ -934,10 +936,14 @@ static int parse_options(struct super_block *sb, char *options, bool is_remount)
>>>>>>>      			F2FS_OPTION(sbi).compress_ext_cnt++;
>>>>>>>      			kfree(name);
>>>>>>>      			break;
>>>>>>> +		case Opt_compress_chksum:
>>>>>>> +			F2FS_OPTION(sbi).compress_chksum = true;
>>>>>>> +			break;
>>>>>>>      #else
>>>>>>>      		case Opt_compress_algorithm:
>>>>>>>      		case Opt_compress_log_size:
>>>>>>>      		case Opt_compress_extension:
>>>>>>> +		case Opt_compress_chksum:
>>>>>>>      			f2fs_info(sbi, "compression options not supported");
>>>>>>>      			break;
>>>>>>>      #endif
>>>>>>> @@ -1523,6 +1529,9 @@ static inline void f2fs_show_compress_options(struct seq_file *seq,
>>>>>>>      		seq_printf(seq, ",compress_extension=%s",
>>>>>>>      			F2FS_OPTION(sbi).extensions[i]);
>>>>>>>      	}
>>>>>>> +
>>>>>>> +	if (F2FS_OPTION(sbi).compress_chksum)
>>>>>>> +		seq_puts(seq, ",compress_chksum");
>>>>>>>      }
>>>>>>>      static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
>>>>>>> diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
>>>>>>> index a5dbb57a687f..7dc2a06cf19a 100644
>>>>>>> --- a/include/linux/f2fs_fs.h
>>>>>>> +++ b/include/linux/f2fs_fs.h
>>>>>>> @@ -273,7 +273,7 @@ struct f2fs_inode {
>>>>>>>      			__le64 i_compr_blocks;	/* # of compressed blocks */
>>>>>>>      			__u8 i_compress_algorithm;	/* compress algorithm */
>>>>>>>      			__u8 i_log_cluster_size;	/* log of cluster size */
>>>>>>> -			__le16 i_padding;		/* padding */
>>>>>>> +			__le16 i_compress_flag;		/* compress flag */
>>>>>>>      			__le32 i_extra_end[0];	/* for attribute size calculation */
>>>>>>>      		} __packed;
>>>>>>>      		__le32 i_addr[DEF_ADDRS_PER_INODE];	/* Pointers to data blocks */
>>>>>>> -- 
>>>>>>> 2.26.2
>>>>>> .
>>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Linux-f2fs-devel mailing list
>>>>> Linux-f2fs-devel@...ts.sourceforge.net
>>>>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
>>>>> .
>>>>>
>>> .
>>>
> .
> 

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