Messages in this thread | | | Subject | Re: [f2fs-dev] [PATCH] f2fs: fix to handle looped node chain during recovery | From | Gao Xiang <> | Date | Sat, 3 Feb 2018 19:36:19 +0800 |
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Sorry, I saw the related code entirely, please ignore these replies.
On 2018/2/3 18:45, Gao Xiang wrote: > > > 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, 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).... > 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); >> >
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