linux-kernel - Re: [PATCH v2] f2fs: clear the remaining prefree

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Date:   Tue, 17 Jul 2018 17:53:44 +0800
From:   Yunlong Song <yunlong.song@...wei.com>
To:     Chao Yu <yuchao0@...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 v2] f2fs: clear the remaining prefree_map of the section



On 2018/7/17 17:05, Chao Yu wrote:
> On 2018/7/16 18:03, Yunlong Song wrote:
>> For the case when sbi->segs_per_sec > 1 with lfs mode, 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 mean:
>
> Subject: [PATCH] f2fs: issue discard align to section in LFS mode
>
> ---
>   fs/f2fs/segment.c | 19 ++++++++++++++++---
>   1 file changed, 16 insertions(+), 3 deletions(-)
>
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index f12dad627fb4..6640c790cf64 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -1761,6 +1761,7 @@ void f2fs_clear_prefree_segments(struct f2fs_sb_info *sbi,
>   	unsigned int start = 0, end = -1;
>   	unsigned int secno, start_segno;
>   	bool force = (cpc->reason & CP_DISCARD);
> +	bool need_align = test_opt(sbi, LFS) && sbi->segs_per_sec > 1;
>
>   	mutex_lock(&dirty_i->seglist_lock);
>
> @@ -1772,10 +1773,15 @@ void f2fs_clear_prefree_segments(struct f2fs_sb_info *sbi,
>   		end = find_next_zero_bit(prefree_map, MAIN_SEGS(sbi),
>   								start + 1);
>
> -		for (i = start; i < end; i++)
> -			clear_bit(i, prefree_map);
> +		if (need_align) {
> +			start = rounddown(start, sbi->segs_per_sec);
> +			end = roundup(start, sbi->segs_per_sec);
> +		}
>
> -		dirty_i->nr_dirty[PRE] -= end - start;
> +		for (i = start; i < end; i++) {
> +			if (test_and_clear_bit(i, prefree_map))
> +				dirty_i->nr_dirty[PRE]--;
> +		}
The above part should be put below if (!test_opt(sbi, DISCARD)), or in 
test_opt(sbi, DISCARD) == 0 case,
the first segment of the next section will be skipped, if only the first 
segment is prefree and all the other
segments of the section are not prefree.

>   		if (!test_opt(sbi, DISCARD))
>   			continue;
> @@ -2564,6 +2570,7 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
>   	struct discard_policy dpolicy;
>   	unsigned long long trimmed = 0;
>   	int err = 0;
> +	bool need_align = test_opt(sbi, LFS) && sbi->segs_per_sec > 1;
>
>   	if (start >= MAX_BLKADDR(sbi) || range->len < sbi->blocksize)
>   		return -EINVAL;
> @@ -2582,6 +2589,12 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
>   	end_segno = (end >= MAX_BLKADDR(sbi)) ? MAIN_SEGS(sbi) - 1 :
>   						GET_SEGNO(sbi, end);
>
> +	if (need_align) {
> +		start_segno = rounddown(start_segno, sbi->segs_per_sec);
> +		end_segno = roundup(end_segno, sbi->segs_per_sec);
> +		end_segno = min(end_segno, MAIN_SEGS(sbi) - 1);
> +	}
> +
>   	cpc.reason = CP_DISCARD;
>   	cpc.trim_minlen = max_t(__u64, 1, F2FS_BYTES_TO_BLK(range->minlen));
>   	cpc.trim_start = start_segno;

-- 
Thanks,
Yunlong Song