linux-kernel - Re: [PATCH] f2fs: fix to do sanity check on total_data

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Date:   Wed, 4 May 2022 08:42:05 +0800
From:   Chao Yu <chao@...nel.org>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Ming Yan <yanming@....edu.cn>, Chao Yu <chao.yu@...o.com>
Subject: Re: [PATCH] f2fs: fix to do sanity check on total_data_blocks



On 2022/5/4 5:47, Jaegeuk Kim wrote:
> On 04/29, Chao Yu wrote:
>> As Yanming reported in bugzilla:
>>
>> https://bugzilla.kernel.org/show_bug.cgi?id=215916
>>
>> The kernel message is shown below:
>>
>> kernel BUG at fs/f2fs/segment.c:2560!
>> Call Trace:
>>   allocate_segment_by_default+0x228/0x440
>>   f2fs_allocate_data_block+0x13d1/0x31f0
>>   do_write_page+0x18d/0x710
>>   f2fs_outplace_write_data+0x151/0x250
>>   f2fs_do_write_data_page+0xef9/0x1980
>>   move_data_page+0x6af/0xbc0
>>   do_garbage_collect+0x312f/0x46f0
>>   f2fs_gc+0x6b0/0x3bc0
>>   f2fs_balance_fs+0x921/0x2260
>>   f2fs_write_single_data_page+0x16be/0x2370
>>   f2fs_write_cache_pages+0x428/0xd00
>>   f2fs_write_data_pages+0x96e/0xd50
>>   do_writepages+0x168/0x550
>>   __writeback_single_inode+0x9f/0x870
>>   writeback_sb_inodes+0x47d/0xb20
>>   __writeback_inodes_wb+0xb2/0x200
>>   wb_writeback+0x4bd/0x660
>>   wb_workfn+0x5f3/0xab0
>>   process_one_work+0x79f/0x13e0
>>   worker_thread+0x89/0xf60
>>   kthread+0x26a/0x300
>>   ret_from_fork+0x22/0x30
>> RIP: 0010:new_curseg+0xe8d/0x15f0
>>
>> The root cause is: ckpt.valid_block_count is inconsistent with SIT table,
>> stat info indicates filesystem has free blocks, but SIT table indicates
>> filesystem has no free segment.
>>
>> So that during garbage colloection, it triggers panic when LFS allocator
>> fails to find free segment.
>>
>> This patch tries to fix this issue by checking consistency in between
>> ckpt.valid_block_count and block accounted from SIT.
>>
>> Cc: stable@...r.kernel.org
>> Reported-by: Ming Yan <yanming@....edu.cn>
>> Signed-off-by: Chao Yu <chao.yu@...o.com>
>> ---
>>   fs/f2fs/segment.c | 24 +++++++++++++++++++++---
>>   1 file changed, 21 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>> index 8c17fed8987e..eddaf3b45b25 100644
>> --- a/fs/f2fs/segment.c
>> +++ b/fs/f2fs/segment.c
>> @@ -4462,6 +4462,7 @@ static int build_sit_entries(struct f2fs_sb_info *sbi)
>>   	unsigned int readed, start_blk = 0;
>>   	int err = 0;
>>   	block_t total_node_blocks = 0;
>> +	block_t total_data_blocks = 0;
>>   
>>   	do {
>>   		readed = f2fs_ra_meta_pages(sbi, start_blk, BIO_MAX_VECS,
>> @@ -4488,6 +4489,8 @@ static int build_sit_entries(struct f2fs_sb_info *sbi)
>>   			seg_info_from_raw_sit(se, &sit);
>>   			if (IS_NODESEG(se->type))
>>   				total_node_blocks += se->valid_blocks;
>> +			else
>> +				total_data_blocks += se->valid_blocks;
>>   
>>   			if (f2fs_block_unit_discard(sbi)) {
>>   				/* build discard map only one time */
>> @@ -4529,6 +4532,8 @@ static int build_sit_entries(struct f2fs_sb_info *sbi)
>>   		old_valid_blocks = se->valid_blocks;
>>   		if (IS_NODESEG(se->type))
>>   			total_node_blocks -= old_valid_blocks;
>> +		else
>> +			total_data_blocks -= old_valid_blocks;
>>   
>>   		err = check_block_count(sbi, start, &sit);
>>   		if (err)
>> @@ -4536,6 +4541,8 @@ static int build_sit_entries(struct f2fs_sb_info *sbi)
>>   		seg_info_from_raw_sit(se, &sit);
>>   		if (IS_NODESEG(se->type))
>>   			total_node_blocks += se->valid_blocks;
>> +		else
>> +			total_data_blocks += se->valid_blocks;
>>   
>>   		if (f2fs_block_unit_discard(sbi)) {
>>   			if (is_set_ckpt_flags(sbi, CP_TRIMMED_FLAG)) {
>> @@ -4557,13 +4564,24 @@ static int build_sit_entries(struct f2fs_sb_info *sbi)
>>   	}
>>   	up_read(&curseg->journal_rwsem);
>>   
>> -	if (!err && total_node_blocks != valid_node_count(sbi)) {
>> +	if (err)
>> +		return err;
>> +
>> +	if (total_node_blocks != valid_node_count(sbi)) {
>>   		f2fs_err(sbi, "SIT is corrupted node# %u vs %u",
>>   			 total_node_blocks, valid_node_count(sbi));
>> -		err = -EFSCORRUPTED;
>> +		return -EFSCORRUPTED;
>>   	}
>>   
>> -	return err;
>> +	if (total_data_blocks + total_node_blocks !=
>> +				valid_user_blocks(sbi)) {
>> +		f2fs_err(sbi, "SIT is corrupted data# %u vs %u",
>> +			 total_data_blocks,
>> +			 valid_user_blocks(sbi) - total_node_blocks);
> 
> This doesn't work, since some NEW_ADDR is not counted from SIT.

Yup, so how about updating check condition as below? it means image
may be corrupted if blocks counted from SIT is more than the one counted
from CKPT.

if (total_data_blocks + total_node_blocks >
			valid_user_blocks(sbi))

Thanks,

> 
>> +		return -EFSCORRUPTED;
>> +	}
>> +
>> +	return 0;
>>   }
>>   
>>   static void init_free_segmap(struct f2fs_sb_info *sbi)
>> -- 
>> 2.25.1