On 9/16/25 16:26, wangzijie wrote:
>> On 9/16/25 15:09, wangzijie wrote:
>>>> 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".
>>
>> Oh, I was testing below patch..., does this what you want to do?
>>
>> I think we can keep all your patches, and appending below patch to detect any
>> potential cases who will update a zero-sized extent.
>>
>> >From 439d61ef3715fafa5c9f2d1b7f8026cdd2564ca7 Mon Sep 17 00:00:00 2001
>> From: Chao Yu <[email protected]>
>> Date: Tue, 16 Sep 2025 11:52:30 +0800
>> Subject: [PATCH] f2fs: add sanity check on ei.len in
>> __update_extent_tree_range()
>>
>> Add a sanity check in __update_extent_tree_range() to detect any
>> zero-sized extent update.
>>
>> Signed-off-by: Chao Yu <[email protected]>
>> ---
>> fs/f2fs/extent_cache.c | 9 +++++++++
>> 1 file changed, 9 insertions(+)
>>
>> diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
>> index 199c1e7a83ef..9544323767be 100644
>> --- a/fs/f2fs/extent_cache.c
>> +++ b/fs/f2fs/extent_cache.c
>> @@ -664,6 +664,15 @@ static void __update_extent_tree_range(struct inode
>> *inode,
>> if (!et)
>> return;
>>
>> + if (unlikely(len == 0)) {
>> + f2fs_bug_on(sbi, 1);
>> + f2fs_err_ratelimited(sbi, "%s: extent len is zero, type: %d, "
>> + "extent [%u, %u, %u], age [%llu, %llu]",
>> + __func__, type, tei->fofs, tei->blk, tei->len,
>> + tei->age, tei->last_blocks);
>> + return;
>> + }
>> +
>> if (type == EX_READ)
>> trace_f2fs_update_read_extent_tree_range(inode, fofs, len,
>> tei->blk, 0);
>> --
>> 2.49.0
>
> Yes, that's exactly what I want to do.
> Maybe we should relocate f2fs_bug_on()?
>
> if (unlikely(len == 0)) {
> f2fs_err_ratelimited(sbi, "%s: extent len is zero, type: %d, "
> "extent [%u, %u, %u], age [%llu, %llu]",
> __func__, type, tei->fofs, tei->blk, tei->len,
> tei->age, tei->last_blocks);
> f2fs_bug_on(sbi, 1);
> return;
> }
Yeah, looks better.
I don't see any problem in my test, will send a formal patch, let me add
Signed-off-by of you if you don't mind. :)
Thanks,
>
>>>
>>>
>>>
>>>>>
>>>>>
>>>>>>>
>>>>>>> Signed-off-by: wangzijie <[email protected]>
>>>>>>> ---
>>>>>>> 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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