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

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Message-ID: <3cd3bfb5-857f-4b61-a1c1-55805bed4609@vivo.com>
Date: Wed, 17 Sep 2025 16:13:34 +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 9/17/2025 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.


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);