linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: check all ones or zeros bitmap with integer data type for better mount performance

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Date:	Tue, 22 Oct 2013 21:23:32 +0900
From:	Jaegeuk Kim <jaegeuk.kim@...sung.com>
To:	Chao Yu <chao2.yu@...sung.com>
Cc:	linux-f2fs-devel@...ts.sourceforge.net,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	谭姝 <shu.tan@...sung.com>
Subject: Re: [f2fs-dev] [PATCH] f2fs: check all ones or zeros bitmap with
 integer data type for better mount performance

Hi,

2013-10-22 (화), 17:28 +0800, Chao Yu:
> Previously, check_block_count check valid_map with bit data type in common
> scenario that sit has all ones or zeros bitmap, it makes low mount
> performance.
> So let's check the special bitmap with integer data type instead of the bit
> one.
> 
> Signed-off-by: Tan Shu <shu.tan@...sung.com>
> Signed-off-by: Yu Chao <chao2.yu@...sung.com>
> ---
>  fs/f2fs/segment.h |   13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
> index 7f94d78..d43ab9f 100644
> --- a/fs/f2fs/segment.h
> +++ b/fs/f2fs/segment.h
> @@ -543,6 +543,7 @@ static inline void check_block_count(struct f2fs_sb_info
> *sbi,
>  {
>  	struct f2fs_sm_info *sm_info = SM_I(sbi);
>  	unsigned int end_segno = sm_info->segment_count - 1;
> +	int *valid_map = (int *)raw_sit->valid_map;
>  	int valid_blocks = 0;
>  	int i;
>  
> @@ -552,6 +553,19 @@ static inline void check_block_count(struct
> f2fs_sb_info *sbi,
>  	/* check boundary of a given segment number */
>  	BUG_ON(segno > end_segno);
>  
> +	/* check all ones or zeros valid_map */
> +	if (GET_SIT_VBLOCKS(raw_sit) == 0) {
> +		for (i = 0; i < SIT_VBLOCK_MAP_SIZE / sizeof(int); i++)

We cannot guarantee all the time that SIT_VBLOCK_MAP_SIZE is multiple of
sizeof(int).
How about using memcmp() with __u8?

> +			if (unlikely(valid_map[i] != 0))
> +				BUG();
> +		return;
> +	} else if (GET_SIT_VBLOCKS(raw_sit) == sbi->blocks_per_seg) {
> +		for (i = 0; i < SIT_VBLOCK_MAP_SIZE / sizeof(int); i++)
> +			if (unlikely(valid_map[i] != -1))
> +				BUG();
> +		return;
> +	}
> +
>  	/* check bitmap with valid block count */
>  	for (i = 0; i < sbi->blocks_per_seg; i++)
>  		if (f2fs_test_bit(i, raw_sit->valid_map))
> ---
> 
> --
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-- 
Jaegeuk Kim
Samsung

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