linux-kernel - Re: [PATCH v1] f2fs: fix uninitialized skipped_gc

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Date:   Wed, 15 Feb 2023 23:07:00 +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>
Cc:     Seokhwan Kim <sukka.kim@...sung.com>,
        Daejun Park <daejun7.park@...sung.com>
Subject: Re: [PATCH v1] f2fs: fix uninitialized skipped_gc_rwsem

On 2023/2/15 10:48, Yonggil Song wrote:
> When f2fs skipped a gc round during victim migration, there was a bug which
> would skip all upcoming gc rounds unconditionally because skipped_gc_rwsem
> was not initialized. It fixes the bug by correctly initializing the
> skipped_gc_rwsem inside the gc loop.

It makes sense to me.

> 
> Fixes: d147ea4adb96 ("f2fs: introduce f2fs_gc_control to consolidate f2fs_gc parameters")

How does this commits introduce the bug?

Thanks,

> Signed-off-by: Yonggil Song <yonggil.song@...sung.com>
> 
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index b22f49a6f128..81d326abaac1 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -1786,8 +1786,8 @@ int f2fs_gc(struct f2fs_sb_info *sbi, struct f2fs_gc_control *gc_control)
>   				prefree_segments(sbi));
>   
>   	cpc.reason = __get_cp_reason(sbi);
> -	sbi->skipped_gc_rwsem = 0;
>   gc_more:
> +	sbi->skipped_gc_rwsem = 0;
>   	if (unlikely(!(sbi->sb->s_flags & SB_ACTIVE))) {
>   		ret = -EINVAL;
>   		goto stop;