2022-11-22 03:52:50

by Yonggil Song

Subject: [PATCH v1] f2fs: avoid victim selection from previous victim section

When f2fs chooses GC victim in large section & LFS mode,
next_victim_seg[gc_type] is referenced first. After segment is freed,
next_victim_seg[gc_type] has the next segment number.
However, next_victim_seg[gc_type] still has the last segment number
even after the last segment of section is freed. In this case, when f2fs
chooses a victim for the next GC round, the last segment of previous victim
section is chosen as a victim.

Initialize next_victim_seg[gc_type] to NULL_SEGNO for the last segment in
large section.

Fixes: e3080b0120a1 ("f2fs: support subsectional garbage collection")
Signed-off-by: Yonggil Song <[email protected]>
---
 fs/f2fs/gc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 4546e01b2ee0..10677d53ef0e 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -1744,8 +1744,9 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
                                 get_valid_blocks(sbi, segno, false) == 0)
                         seg_freed++;
 
-                if (__is_large_section(sbi) && segno + 1 < end_segno)
-                        sbi->next_victim_seg[gc_type] = segno + 1;
+                if (__is_large_section(sbi))
+                        sbi->next_victim_seg[gc_type] =
+                                (segno + 1 < end_segno) ? segno + 1 : NULL_SEGNO;
 skip:
                 f2fs_put_page(sum_page, 0);
         }
-- 
2.34.1

2022-11-22 09:19:10

by Chao Yu

Subject: Re: [PATCH v1] f2fs: avoid victim selection from previous victim section

Hi Yonggil,

I guess your email client forces converting tab and space characters of
patch, please check that.

On 2022/11/22 10:36, Yonggil Song wrote:
> When f2fs chooses GC victim in large section & LFS mode,
> next_victim_seg[gc_type] is referenced first. After segment is freed,
> next_victim_seg[gc_type] has the next segment number.
> However, next_victim_seg[gc_type] still has the last segment number
> even after the last segment of section is freed. In this case, when f2fs
> chooses a victim for the next GC round, the last segment of previous victim
> section is chosen as a victim.
>
> Initialize next_victim_seg[gc_type] to NULL_SEGNO for the last segment in
> large section.
>
> Fixes: e3080b0120a1 ("f2fs: support subsectional garbage collection")

Good catch, I'm fine with this fix.

Thanks,

> Signed-off-by: Yonggil Song <[email protected]>
> ---
>  fs/f2fs/gc.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index 4546e01b2ee0..10677d53ef0e 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -1744,8 +1744,9 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>                                  get_valid_blocks(sbi, segno, false) == 0)
>                          seg_freed++;
>
> -                if (__is_large_section(sbi) && segno + 1 < end_segno)
> -                        sbi->next_victim_seg[gc_type] = segno + 1;
> +                if (__is_large_section(sbi))
> +                        sbi->next_victim_seg[gc_type] =
> +                                (segno + 1 < end_segno) ? segno + 1 : NULL_SEGNO;
>  skip:
>                  f2fs_put_page(sum_page, 0);
>          }
> --
> 2.34.1

2022-11-22 10:45:48

by Yonggil Song

Subject: RE:(2) [PATCH v1] f2fs: avoid victim selection from previous victim section

Hi Chao,

Thanks for your review.
I'll fix this and resend a mail.

Thanks

>Hi Yonggil,
>
>I guess your email client forces converting tab and space characters of
>patch, please check that.
>
>On 2022/11/22 10:36, Yonggil Song wrote:
>> When f2fs chooses GC victim in large section & LFS mode,
>> next_victim_seg[gc_type] is referenced first. After segment is freed,
>> next_victim_seg[gc_type] has the next segment number.
>> However, next_victim_seg[gc_type] still has the last segment number
>> even after the last segment of section is freed. In this case, when f2fs
>> chooses a victim for the next GC round, the last segment of previous victim
>> section is chosen as a victim.
>>
>> Initialize next_victim_seg[gc_type] to NULL_SEGNO for the last segment in
>> large section.
>>
>> Fixes: e3080b0120a1 ("f2fs: support subsectional garbage collection")
>
>Good catch, I'm fine with this fix.
>
>Thanks,
>
>> Signed-off-by: Yonggil Song <[email protected]>
>> ---
>> fs/f2fs/gc.c | 5 +++--
>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>> index 4546e01b2ee0..10677d53ef0e 100644
>> --- a/fs/f2fs/gc.c
>> +++ b/fs/f2fs/gc.c
>> @@ -1744,8 +1744,9 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>> get_valid_blocks(sbi, segno, false) == 0)
>> seg_freed++;
>>
>> - if (__is_large_section(sbi) && segno + 1 < end_segno)
>> - sbi->next_victim_seg[gc_type] = segno + 1;
>> + if (__is_large_section(sbi))
>> + sbi->next_victim_seg[gc_type] =
>> + (segno + 1 < end_segno) ? segno + 1 : NULL_SEGNO;
>> skip:
>> f2fs_put_page(sum_page, 0);
>> }
>> --
>> 2.34.1