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Subject: Re: [PATCH] f2fs: compress: do sanity check on cluster
To:     Jaegeuk Kim <jaegeuk@kernel.org>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, Chao Yu <chao.yu@linux.dev>
References: <20210803103952.737222-1-chao@kernel.org>
 <YQmKQVxQwJL2GU09@google.com>
 <275b4ec7-d7fd-b169-ff43-3ceec37b47b9@kernel.org>
 <YQn1fchZOJlQeiW+@google.com>
From:   Chao Yu <chao@kernel.org>
Message-ID: <709b3653-372b-e809-d98b-56d18a7544cd@kernel.org>
Date:   Wed, 4 Aug 2021 10:39:21 +0800
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On 2021/8/4 10:03, Jaegeuk Kim wrote:
> On 08/04, Chao Yu wrote:
>> On 2021/8/4 2:26, Jaegeuk Kim wrote:
>>> On 08/03, Chao Yu wrote:
>>>> This patch adds f2fs_sanity_check_cluster() to support doing
>>>> sanity check on cluster of compressed file, it will be triggered
>>>> from below two paths:
>>>>
>>>> - __f2fs_cluster_blocks()
>>>> - f2fs_map_blocks(F2FS_GET_BLOCK_FIEMAP)
>>>>
>>>> And it can detect below three kind of cluster insanity status.
>>>>
>>>> C: COMPRESS_ADDR
>>>> N: NULL_ADDR or NEW_ADDR
>>>> V: valid blkaddr
>>>> *: any value
>>>>
>>>> 1. [*|C|*|*]
>>>> 2. [C|*|C|*]
>>>> 3. [C|N|N|V]
>>>>
>>>> Signed-off-by: Chao Yu <chao@kernel.org>
>>>> ---
>>>>    fs/f2fs/compress.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++
>>>>    fs/f2fs/data.c     | 21 ++++++++++++------
>>>>    fs/f2fs/f2fs.h     |  1 +
>>>>    3 files changed, 68 insertions(+), 7 deletions(-)
>>>>
>>>> diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
>>>> index 455561826c7d..4aa166d3d9bf 100644
>>>> --- a/fs/f2fs/compress.c
>>>> +++ b/fs/f2fs/compress.c
>>>> @@ -898,6 +898,54 @@ static bool cluster_has_invalid_data(struct compress_ctx *cc)
>>>>    	return false;
>>>>    }
>>>> +bool f2fs_sanity_check_cluster(struct dnode_of_data *dn)
>>>> +{
>>>> +	struct f2fs_sb_info *sbi = F2FS_I_SB(dn->inode);
>>>> +	unsigned int cluster_size = F2FS_I(dn->inode)->i_cluster_size;
>>>> +	bool compressed = dn->data_blkaddr == COMPRESS_ADDR;
>>>> +	int cluster_end = 0;
>>>> +	int i;
>>>> +	char *reason = "";
>>>> +
>>>> +	if (!compressed)
>>>> +		return false;
>>>> +
>>>> +	/* [..., COMPR_ADDR, ...] */
>>>> +	if (dn->ofs_in_node % cluster_size) {
>>>> +		reason = "[*|C|*|*]";
>>>> +		goto out;
>>>> +	}
>>>> +
>>>> +	for (i = 1; i < cluster_size; i++) {
>>>> +		block_t blkaddr = data_blkaddr(dn->inode, dn->node_page,
>>>> +							dn->ofs_in_node + i);
>>>> +
>>>> +		/* [COMPR_ADDR, ..., COMPR_ADDR] */
>>>> +		if (blkaddr == COMPRESS_ADDR) {
>>>> +			reason = "[C|*|C|*]";
>>>> +			goto out;
>>>> +		}
>>>> +		if (compressed) {
>>>> +			if (!__is_valid_data_blkaddr(blkaddr)) {
>>>> +				if (!cluster_end)
>>>> +					cluster_end = i;
>>>> +				continue;
>>>> +			}
>>>> +			/* [COMPR_ADDR, NULL_ADDR or NEW_ADDR, valid_blkaddr] */
>>>> +			if (cluster_end) {
>>>> +				reason = "[C|N|N|V]";
>>>> +				goto out;
>>>> +			}
>>>> +		}
>>>> +	}
>>>> +	return false;
>>>> +out:
>>>> +	f2fs_warn(sbi, "access invalid cluster, ino:%lu, nid:%u, ofs_in_node:%u, reason:%s",
>>>> +			dn->inode->i_ino, dn->nid, dn->ofs_in_node, reason);
>>>> +	set_sbi_flag(sbi, SBI_NEED_FSCK);
>>>> +	return true;
>>>> +}
>>>> +
>>>>    static int __f2fs_cluster_blocks(struct inode *inode,
>>>>    				unsigned int cluster_idx, bool compr)
>>>>    {
>>>> @@ -915,6 +963,11 @@ static int __f2fs_cluster_blocks(struct inode *inode,
>>>>    		goto fail;
>>>>    	}
>>>> +	if (f2fs_sanity_check_cluster(&dn)) {
>>>> +		ret = -EFSCORRUPTED;
>>>> +		goto fail;
>>>> +	}
>>>> +
>>>>    	if (dn.data_blkaddr == COMPRESS_ADDR) {
>>>>    		int i;
>>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>>>> index 948083c88d17..75dda2035f68 100644
>>>> --- a/fs/f2fs/data.c
>>>> +++ b/fs/f2fs/data.c
>>>> @@ -1558,13 +1558,20 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
>>>>    			}
>>>>    			if (flag == F2FS_GET_BLOCK_PRECACHE)
>>>>    				goto sync_out;
>>>> -			if (flag == F2FS_GET_BLOCK_FIEMAP &&
>>>> -						blkaddr == NULL_ADDR) {
>>>> -				if (map->m_next_pgofs)
>>>> -					*map->m_next_pgofs = pgofs + 1;
>>>> -				goto sync_out;
>>>> -			}
>>>> -			if (flag != F2FS_GET_BLOCK_FIEMAP) {
>>>> +			if (flag == ) {
>>>> +				if (blkaddr == NULL_ADDR) {
>>>> +					if (map->m_next_pgofs)
>>>> +						*map->m_next_pgofs = pgofs + 1;
>>>> +					goto sync_out;
>>>> +				}
>>>> +#ifdef CONFIG_F2FS_FS_COMPRESSION
>>>> +				if (f2fs_compressed_file(inode) &&
>>>> +					f2fs_sanity_check_cluster(&dn)) {
>>>> +					err = -EFSCORRUPTED;
>>>
>>> I prefer to give the block map as is instead of giving an error, since this\
>>
>> It looks the policy is not consistent with the one we did in
>> f2fs_is_valid_blkaddr().
> 
> Why FIEMAP only? Do we need to check in other cases likewise
> f2fs_is_valid_blkaddr()?

Agreed, let me cover all missing pieces.

> 
>>
>>> takes away to debug the problem from user-land.
>>
>> We can debug through "dump.f2fs -i" command? also once f2fs_sanity_check_cluster()
>> fails, it will print kernel message for further debuging.
> 
> My concern here is how to debug and get out of this endless fiemap error before
> recovered.

Got your concern.

For debug purpose, maybe we can add a new ioctl under CONFIG_F2FS_CHECK_FS to dump
original mapping? or support dump.f2fs -f to dump all blkaddrs of target file?

Thanks

> 
>>
>> Thanks,
>>
>>>
>>>> +					goto sync_out;
>>>> +				}
>>>> +#endif
>>>> +			} else {
>>>>    				/* for defragment case */
>>>>    				if (map->m_next_pgofs)
>>>>    					*map->m_next_pgofs = pgofs + 1;
>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>> index 20389b9b3eac..86d416ffad61 100644
>>>> --- a/fs/f2fs/f2fs.h
>>>> +++ b/fs/f2fs/f2fs.h
>>>> @@ -4060,6 +4060,7 @@ void f2fs_end_read_compressed_page(struct page *page, bool failed,
>>>>    							block_t blkaddr);
>>>>    bool f2fs_cluster_is_empty(struct compress_ctx *cc);
>>>>    bool f2fs_cluster_can_merge_page(struct compress_ctx *cc, pgoff_t index);
>>>> +bool f2fs_sanity_check_cluster(struct dnode_of_data *dn);
>>>>    void f2fs_compress_ctx_add_page(struct compress_ctx *cc, struct page *page);
>>>>    int f2fs_write_multi_pages(struct compress_ctx *cc,
>>>>    						int *submitted,
>>>> -- 
>>>> 2.22.1