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 <heyun...@huawei.com>
Signed-off-by: Chao Yu <yuch...@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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