Messages in this thread Patch in this message | | | Subject | Re: [f2fs-dev] [PATCH] f2fs: fix to handle looped node chain during recovery | From | Gao Xiang <> | Date | Sat, 3 Feb 2018 18:45:35 +0800 |
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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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