`On 2018/2/3 18:35, Gao Xiang wrote:> Hi Chao and YunLei,>>> On 2018/2/3 17:44, Chao Yu wrote:>> There is no checksum in node block now, so bit-transition from hardware>> can make node_footer.next_blkaddr being corrupted w/o any detection,>> result in node chain becoming looped one.>>>> For this condition, during recovery, in order to avoid running into dead>> loop, let's detect it and just skip out.>>>> Signed-off-by: Yunlei He <heyunlei@huawei.com>>> Signed-off-by: Chao Yu <yuchao0@huawei.com>>> --->>   fs/f2fs/recovery.c | 14 ++++++++++++++>>   1 file changed, 14 insertions(+)>>>> diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c>> index b6d1ec620a8c..60dd0cee4820 100644>> --- a/fs/f2fs/recovery.c>> +++ b/fs/f2fs/recovery.c>> @@ -243,6 +243,9 @@ static int find_fsync_dnodes(struct f2fs_sb_info >> *sbi, struct list_head *head,>>       struct curseg_info *curseg;>>       struct page *page = NULL;>>       block_t blkaddr;>> +    unsigned int loop_cnt = 0;>> +    unsigned int free_blocks = sbi->user_block_count ->> +                    valid_user_blocks(sbi);> There exists another way to detect loop more faster but only using two > variables.> The algorithm is described as simply "B goes forward a steps only A > goes forwards 2 steps"."B goes forward a step only when A goes forward 2(or constant x, more than 1) steps".> For example:> 1)>    1   2  3  4   5   6     7>    |             \             />    |                \------/>   A, B> 2)>    1  2  3  4   5   6     7>     |   |        \             />    B   A        \------/>  3)>    1  2  3  4   5   6     7>        |    |     \             />       B   A      \------/>   4)>    1  2  3  4   5   6     7>        |       |\             />       B      A \------/> 5)....>Sorry, it seems the encoded diagram is in a mess, I try again.1)    1 -> 2 -> 3 -> 4 -> 5 ->  6 -> 7    |               \             /    |                \-----<-----/   A, B2)    1 -> 2 -> 3 -> 4 -> 5 ->  6 -> 7    |    |          \             /    |    |           \-----<-----/    B    A3)    1 -> 2 -> 3 -> 4 -> 5 ->  6 -> 7         |    |     \             /         |    |      \-----<-----/         B    A4)    1 -> 2 -> 3 -> 4 -> 5 ->  6 -> 7         |         |\             /         |         | \-----<-----/         B         A5)....if B catchs up A, there exists a cycle.Thanks,> B will equal A or beyoud A if and only if there has a cycle.> It's a more faster algorithm. :D>> Thanks,>>>       int err = 0;>>         /* get node pages in the current segment */>> @@ -295,6 +298,17 @@ static int find_fsync_dnodes(struct f2fs_sb_info >> *sbi, struct list_head *head,>>           if (IS_INODE(page) && is_dent_dnode(page))>>               entry->last_dentry = blkaddr;>>   next:>> +        /* sanity check in order to detect looped node chain */>> +        if (++loop_cnt >= free_blocks ||>> +            blkaddr == next_blkaddr_of_node(page)) {>> +            f2fs_msg(sbi->sb, KERN_NOTICE,>> +                "%s: detect looped node chain, ">> +                "blkaddr:%u, next:%u",>> +                __func__, blkaddr, next_blkaddr_of_node(page));>> +            err = -EINVAL;>> +            break;>> +        }>> +>>           /* check next segment */>>           blkaddr = next_blkaddr_of_node(page);>>           f2fs_put_page(page, 1);>`