linux-kernel - Re: [PATCH 2/5] f2fs: clear the remaining prefree

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Date:   Fri, 13 Jul 2018 11:13:54 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Yunlong Song <yunlong.song@...wei.com>, <jaegeuk@...nel.org>,
        <chao@...nel.org>, <yunlong.song@...oud.com>
CC:     <miaoxie@...wei.com>, <bintian.wang@...wei.com>,
        <shengyong1@...wei.com>, <heyunlei@...wei.com>,
        <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/5] f2fs: clear the remaining prefree_map of the section

On 2018/7/12 23:09, Yunlong Song wrote:
> For the case when sbi->segs_per_sec > 1, take section:segment = 5 for
> example, if the section prefree_map is ...previous section | current
> section (1 1 0 1 1) | next section..., then the start = x, end = x + 1,
> after start = start_segno + sbi->segs_per_sec, start = x + 5, then it
> will skip x + 3 and x + 4, but their bitmap is still set, which will
> cause duplicated f2fs_issue_discard of this same section in the next
> write_checkpoint, so fix it.

I didn't get it, if # 2 segment is not prefree state, so it still has valid
blocks there, so we won't issue discard due to below condition, right?

		if (!IS_CURSEC(sbi, secno) &&
			!get_valid_blocks(sbi, start, true))

Thanks,

> 
> Signed-off-by: Yunlong Song <yunlong.song@...wei.com>
> ---
>  fs/f2fs/segment.c | 19 +++++++++++++++++--
>  1 file changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 47b6595..fd38b61 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -1684,8 +1684,23 @@ void f2fs_clear_prefree_segments(struct f2fs_sb_info *sbi,
>  		start = start_segno + sbi->segs_per_sec;
>  		if (start < end)
>  			goto next;
> -		else
> -			end = start - 1;
> +		else {
> +			start_segno = start;
> +
> +			while (1) {
> +				start = find_next_bit(prefree_map, start_segno,
> +									end + 1);
> +				if (start >= start_segno)
> +					break;
> +				end = find_next_zero_bit(prefree_map, start_segno,
> +										start + 1);
> +				for (i = start; i < end; i++)
> +					clear_bit(i, prefree_map);
> +				dirty_i->nr_dirty[PRE] -= end - start;
> +			}
> +
> +			end = start_segno - 1;
> +		}
>  	}
>  	mutex_unlock(&dirty_i->seglist_lock);
>  
>