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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>
 <709b3653-372b-e809-d98b-56d18a7544cd@kernel.org>
 <YQsZv1dqP6XMe1C2@google.com>
From:   Chao Yu <chao@kernel.org>
Message-ID: <0aa2b1ec-8dd9-d15d-87dc-54c0bf068a18@kernel.org>
Date:   Thu, 5 Aug 2021 08:43:01 +0800
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On 2021/8/5 6:50, Jaegeuk Kim wrote:
> On 08/04, Chao Yu wrote:
>> 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?
> 
> How about giving EFSCORRUPTED if CONFIG_F2FS_CHECK_FS is enabled? Sometimes it's

Hmm... if original mapping is useful for debuging, shouldn't we return original one
if CONFIG_F2FS_CHECK_FS is enabled? since commonly we will enable CONFIG_F2FS_CHECK_FS
in eng version of Android to get more debug info.

Thanks,

> useful to ask fiemap to users.
> 
>>
>> 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