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 18:35:53 +0800 |
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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". 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)....
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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