linux-kernel - Re: [PATCH] f2fs: check segment type before recover data

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Date:   Tue, 2 Jan 2018 19:02:38 +0800
From:   Yunlong Song <yunlong.song@...wei.com>
To:     Chao Yu <yuchao0@...wei.com>, <jaegeuk@...nel.org>,
        <chao@...nel.org>, <yunlong.song@...oud.com>
CC:     <miaoxie@...wei.com>, <bintian.wang@...wei.com>,
        <shengyong1@...wei.com>, <heyunlei@...wei.com>,
        <linux-fsdevel@...r.kernel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] f2fs: check segment type before recover data



On 2018/1/2 14:49, Chao Yu wrote:
> On 2017/12/30 15:42, Yunlong Song wrote:
>> In some case, the node blocks has wrong blkaddr whose segment type is
> You mean *data block* has wrong blkaddr whose segment type is NODE?
Yes.
>
>> NODE, e.g., recover inode has missing xattr flag and the blkaddr is in
>> the xattr range. Since fsck.f2fs does not check the recovery nodes, this
>> will cause __f2fs_replace_block change the curseg of node and do the
>> update_sit_entry(sbi, new_blkaddr, 1) with no next_blkoff refresh, as a
> Do you mean the root cause is that __f2fs_replace_block didn't update
> next_blkoff?
No, it's not the root cause. The root cause may be something like DDR flip.
>
>> result, when recovery process write checkpoint and sync nodes, the
>> next_blkoff of curseg is used in the segment bit map, then it will
>> cause f2fs_bug_on. So let's check the segment type before recover data,
>> and stop recover if it is not in DATA segment.
> Sorry, I can't catch the whole cause and effect from you description, if
> possible, could you give an example?
For example, the i_inline flag has F2FS_INLINE_XATTR, and the last 50 
i_addrs have xattr
context. But if DDR flips, the i_inline flag may miss F2FS_INLINE_XATTR, 
and the last 50 i_addrs
are considered as data block addr. If the xattr context is 0x1234, and 
0x1234 happens to be
a valid block addr, and the block 0x1234 happens to be in a warm node 
segment. Then do_recover_data
will call f2fs_replace_block() with dest = 0x1234, which will change 
curseg of warm node to
0x1234's segment, and make update_sit_entry(sbi, 0x1234, 1), the 
curseg->next_blkoff also
points to 0x1234's offset in its segment. When recovery process calls 
write_checkpoint, sync
nodes will write to 0x1234's offset of curseg warm node. The 
update_sit_entry will check that
offset and find the bitmap is already set to 1 and then calls f2fs_bug_on.

>
> Thanks,
>
>> Signed-off-by: Yunlong Song <yunlong.song@...wei.com>
>> ---
>>   fs/f2fs/recovery.c | 3 ++-
>>   fs/f2fs/segment.h  | 3 +++
>>   2 files changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
>> index 7d63faf..e8fee4a 100644
>> --- a/fs/f2fs/recovery.c
>> +++ b/fs/f2fs/recovery.c
>> @@ -478,7 +478,8 @@ static int do_recover_data(struct f2fs_sb_info *sbi, struct inode *inode,
>>   		}
>>   
>>   		/* dest is valid block, try to recover from src to dest */
>> -		if (is_valid_blkaddr(sbi, dest, META_POR)) {
>> +		if (is_valid_blkaddr(sbi, dest, META_POR) &&
>> +			is_data_blkaddr(sbi, dest)) {
>>   
>>   			if (src == NULL_ADDR) {
>>   				err = reserve_new_block(&dn);
>> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
>> index 71a2aaa..5c5a215 100644
>> --- a/fs/f2fs/segment.h
>> +++ b/fs/f2fs/segment.h
>> @@ -115,6 +115,9 @@
>>   #define SECTOR_TO_BLOCK(sectors)					\
>>   	((sectors) >> F2FS_LOG_SECTORS_PER_BLOCK)
>>   
>> +#define is_data_blkaddr(sbi, blkaddr)	\
>> +	(IS_DATASEG(get_seg_entry(sbi, GET_SEGNO(sbi, blkaddr))->type))
>> +
>>   /*
>>    * indicate a block allocation direction: RIGHT and LEFT.
>>    * RIGHT means allocating new sections towards the end of volume.
>>
>
> .
>

-- 
Thanks,
Yunlong Song