linux-kernel - Re: [PATCH] f2fs: add bug_on when f2fs

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Message-ID: <20171012232308.GA19689@jaegeuk-macbookpro.roam.corp.google.com>
Date:   Thu, 12 Oct 2017 16:23:08 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Yunlong Song <yunlong.song@...wei.com>
Cc:     chao@...nel.org, yuchao0@...wei.com, yunlong.song@...oud.com,
        miaoxie@...wei.com, bintian.wang@...wei.com,
        linux-fsdevel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] f2fs: add bug_on when f2fs_gc even fails to get one
 victim

Hi Yunlong,

On 10/11, Yunlong Song wrote:
> This can help us to debug on some corner case.
> 
> Signed-off-by: Yunlong Song <yunlong.song@...wei.com>
> ---
>  fs/f2fs/gc.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index 197ebf4..960503e 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -986,6 +986,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
>  		.ilist = LIST_HEAD_INIT(gc_list.ilist),
>  		.iroot = RADIX_TREE_INIT(GFP_NOFS),
>  	};
> +	bool need_gc = false;
>  
>  	trace_f2fs_gc_begin(sbi->sb, sync, background,
>  				get_pages(sbi, F2FS_DIRTY_NODES),
> @@ -1018,8 +1019,10 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
>  			if (ret)
>  				goto stop;
>  		}
> -		if (has_not_enough_free_secs(sbi, 0, 0))
> +		if (has_not_enough_free_secs(sbi, 0, 0)) {
>  			gc_type = FG_GC;
> +			need_gc = true;
> +		}
>  	}
>  
>  	/* f2fs_balance_fs doesn't need to do BG_GC in critical path. */
> @@ -1028,6 +1031,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
>  		goto stop;
>  	}
>  	if (!__get_victim(sbi, &segno, gc_type)) {
> +		f2fs_bug_on(sbi, !total_freed && need_gc);

How about this, if this is for debugging purpose?

		if (!total_freed && need_gc)
			f2fs_msg(...);

It's not a good way to define a value for f2fs_bug_on(), since it is only
activated by CHECK_FS config.

Thanks,

>  		ret = -ENODATA;
>  		goto stop;
>  	}
> -- 
> 1.8.5.2