linux-kernel - Re: [PATCH 2/2] f2fs: Enhance the subsequent logic of valid_thresh_ratio to prevent unnecessary background GC

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <c2c7fbdb-f71c-46aa-a47d-8bd4bec688d4@vivo.com>
Date: Sat, 20 Sep 2025 10:49:20 +0800
From: Liao Yuanhong <liaoyuanhong@...o.com>
To: Chao Yu <chao@...nel.org>, Jaegeuk Kim <jaegeuk@...nel.org>,
 "open list:F2FS FILE SYSTEM" <linux-f2fs-devel@...ts.sourceforge.net>,
 open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] f2fs: Enhance the subsequent logic of
 valid_thresh_ratio to prevent unnecessary background GC


On 9/18/2025 10:16 AM, Chao Yu wrote:
> On 9/17/25 16:13, Liao Yuanhong wrote:
>> On 9/17/2025 3:57 PM, Chao Yu wrote:
>>> On 9/17/25 15:08, Liao Yuanhong wrote:
>>>> On 9/15/2025 4:36 PM, Chao Yu wrote:
>>>>> On 9/9/25 21:44, Liao Yuanhong wrote:
>>>>>> When the proportion of dirty segments within a section exceeds the
>>>>>> valid_thresh_ratio, the gc_cost of that section is set to UINT_MAX,
>>>>>> indicating that these sections should not be released. However, if all
>>>>>> section costs within the scanning range of get_victim() are UINT_MAX,
>>>>>> background GC will still occur. Add a condition to prevent this situation.
>>>>> For this case, f2fs_get_victim() will return 0, and f2fs_gc() will use unchanged
>>>>> segno for GC?
>>>>>
>>>>> Thanks,
>>>> You're right, segno won't update in this scenario, and this patch feature is redundant.
>>> Oh, I meant, if f2fs_get_victim() fails to select a valid victim due to the reason you
>>> described, f2fs_get_victim() will return 0, and f2fs_gc() will migrate segment #NULL_SEGNO?
>>> Or am I missing something?
>>>
>>> Thanks,
>> Yes. In this scenario, since it won't enter the|p.min_cost > cost|condition,|p.min_segno|will retain its initial value|||NULL_SEGNO|. This is consistent with what you described.
> Do you have a script to reproduce this bug?
>
> Thanks,

I didn't explain it clearly. What I mean is that this patch is 
redundant, the original code is fine.


Thanks,

Liao

>>
>> Thanks,
>>
>> Liao
>>
>>>> Thanks,
>>>>
>>>> Liao
>>>>
>>>>>> Signed-off-by: Liao Yuanhong <liaoyuanhong@...o.com>
>>>>>> ---
>>>>>>     fs/f2fs/gc.c | 5 +++++
>>>>>>     1 file changed, 5 insertions(+)
>>>>>>
>>>>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>>>>>> index 4a8c08f970e3..ffc3188416f4 100644
>>>>>> --- a/fs/f2fs/gc.c
>>>>>> +++ b/fs/f2fs/gc.c
>>>>>> @@ -936,6 +936,11 @@ int f2fs_get_victim(struct f2fs_sb_info *sbi, unsigned int *result,
>>>>>>             }
>>>>>>         }
>>>>>>     +    if (f2fs_sb_has_blkzoned(sbi) && p.min_cost == UINT_MAX) {
>>>>>> +        ret = -ENODATA;
>>>>>> +        goto out;
>>>>>> +    }
>>>>>> +
>>>>>>         /* get victim for GC_AT/AT_SSR */
>>>>>>         if (is_atgc) {
>>>>>>             lookup_victim_by_age(sbi, &p);