linux-kernel - Re: [PATCH v1] f2fs: avoid victim selection from previous victim section

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Date:   Tue, 22 Nov 2022 16:01:54 +0800
From:   Chao Yu <chao@...nel.org>
To:     yonggil.song@...sung.com,
        "jaegeuk@...nel.org" <jaegeuk@...nel.org>,
        "linux-f2fs-devel@...ts.sourceforge.net" 
        <linux-f2fs-devel@...ts.sourceforge.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
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 <yonggil.song@...sung.com>
> ---
>   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