linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: change the method of calculating the number summary blocks

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Date:	Mon, 28 Oct 2013 19:34:36 +0900
From:	Jaegeuk Kim <jaegeuk.kim@...sung.com>
To:	fanofcode.li@...sung.com
Cc:	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-f2fs-devel@...ts.sourceforge.net" 
	<linux-f2fs-devel@...ts.sourceforge.net>
Subject: Re: [f2fs-dev] [PATCH] f2fs: change the method of calculating the
 number summary blocks

Hi,

2013-10-28 (월), 08:54 +0000, Fan Li:
> "There is a HTML error in the previous email, so I send this one.If you already received this before, please ignore it.Sorry for the inconvenience"
> 
> This patch change the method of calculating the number of summary blocks in function  npages_for_summary_flush.
> npages_for_summary_flush uses (SUMMARY_SIZE + 1) as the size of a f2fs_summary while the actual size is just SUMMARY_SIZE.
> As a result, occasionally the return value of npages_for_summary_flush will be bigger than the actual number by one, and the checkpoint won't be written contiguously  into disk.
> Besides, struct f2fs_summary can't be split to two pages, so it could take more space than the sum of its size, the current version seems not to take it into account.
> 

Again. Please write a description not to exceed 80 columns.

> Signed-off-by: Fan Li <fanofcode.li@...sung.com>
> ---
>  fs/f2fs/segment.c |   14 ++++++--------
>  1 file changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c index 487af61..ba2930f 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -279,9 +279,8 @@ static void __add_sum_entry(struct f2fs_sb_info *sbi, int type,
>   */
>  int npages_for_summary_flush(struct f2fs_sb_info *sbi)  {
> -	int total_size_bytes = 0;
>  	int valid_sum_count = 0;
> -	int i, sum_space;
> +	int i, sum_in_page;
>  
>  	for (i = CURSEG_HOT_DATA; i <= CURSEG_COLD_DATA; i++) {
>  		if (sbi->ckpt->alloc_type[i] == SSR)
> @@ -290,13 +289,12 @@ int npages_for_summary_flush(struct f2fs_sb_info *sbi)
>  			valid_sum_count += curseg_blkoff(sbi, i);
>  	}
>  
> -	total_size_bytes = valid_sum_count * (SUMMARY_SIZE + 1)
> -			+ sizeof(struct nat_journal) + 2
> -			+ sizeof(struct sit_journal) + 2;
> -	sum_space = PAGE_CACHE_SIZE - SUM_FOOTER_SIZE;
> -	if (total_size_bytes < sum_space)
> +	sum_in_page = (PAGE_CACHE_SIZE - 2*SUM_JOURNAL_SIZE - SUM_FOOTER_SIZE)/

	sum_in_page = (PAGE_CACHE_SIZE - 2 * SUM_JOURNAL_SIZE -
SUM_FOOTER_SIZE) / SUMMARY_SIZE;

Coding style.

> +			SUMMARY_SIZE;
> +	if (valid_sum_count <= sum_in_page)
>  		return 1;
> -	else if (total_size_bytes < 2 * sum_space)
> +	else if (valid_sum_count-sum_in_page <=
> +			(PAGE_CACHE_SIZE-SUM_FOOTER_SIZE)/SUMMARY_SIZE)

ditto.

>  		return 2;
>  	return 3;
>  }
> --
> 1.7.9.5

-- 
Jaegeuk Kim
Samsung

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