>On 9/16/25 13:22, wangzijie wrote:
>>> On 09/15, wangzijie wrote:
>>>> When we get wrong extent info data, and look up extent_node in rb tree,
>>>> it will cause infinite loop (CONFIG_F2FS_CHECK_FS=n). Avoiding this by
>>>> return NULL.
>>>
>>> This is the exact buggy case which we should fix the original one. Have
>>> you seen this error? In that case, can we consider writing some kernel
>>> message and handle the error properly?
>>
>> Hi Jaegeuk,
>> The original one is the bug I mentioned in the first patch of this patch set
>> ("f2fs: fix zero-sized extent for precache extents").
>
>Zijie,
>
>Did you suffer this problem in product? right?
Hi Chao,
Yes, and I can confirm that infinite loop cases I suffered are caused by the
bug I
mentioned in the first patch of this patch set. But I'm not sure if there are
other cases that can cause this infinite loop.
>>
>> When we use a wrong extent_info(zero-sized) to do update, and there exists a
>> extent_node which has same fofs as the wrong one, we will skip "invalidate
>> all extent
>> nodes in range [fofs, fofs + len - 1]"(en->ei.fofs = end = tei->fofs +
>> tei->len = tei->fofs),
>> which cause the infinite loop in __insert_extent_tree().
>>
>> So we can add f2fs_bug_on() when there occurs zero-sized extent
>> in f2fs_update_read_extent_cache_range(), and give up this zero-sized
>> extent update to handle other unknown buggy cases. Do you think this will be
>> better?
>>
>> And do we need to solve this infinite loop?
>
>IMO, it's worth to end such loop if there is any corrupted extent in rbtree to
>avoid kernel hang, no matter it is caused by software bug or hardware flaw
>potentially.
>
>Thanks,
And do you think we need this?
"add f2fs_bug_on() when there occurs zero-sized extent in
f2fs_update_read_extent_cache_range(),
and give up this zero-sized extent update to handle other unknown buggy cases".
>>
>>
>>>>
>>>> Signed-off-by: wangzijie <wangzij...@honor.com>
>>>> ---
>>>> fs/f2fs/extent_cache.c | 1 +
>>>> 1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
>>>> index 199c1e7a8..6ed6f3d1d 100644
>>>> --- a/fs/f2fs/extent_cache.c
>>>> +++ b/fs/f2fs/extent_cache.c
>>>> @@ -605,6 +605,7 @@ static struct extent_node *__insert_extent_tree(struct
>>>> f2fs_sb_info *sbi,
>>>> leftmost = false;
>>>> } else {
>>>> f2fs_bug_on(sbi, 1);
>>>> + return NULL;
>>>> }
>>>> }
>>>>
>>>> --
>>>> 2.25.1
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