Re: [RFC PATCH v2] mkfs.f2fs: recalculate sit_segments by max_sit_bitmap_size

[Chao Yu <chao2.yu@samsung.com>]

Hi all,

> -----Original Message-----
> From: Junling Zheng [mailto:zhengjunling@huawei.com]
> Sent: Tuesday, February 23, 2016 11:47 AM
> To: linux-f2fs-devel@lists.sourceforge.net; jaegeuk@kernel.org
> Subject: [f2fs-dev] [RFC PATCH v2] mkfs.f2fs: recalculate sit_segments by max_sit_bitmap_size
> 
> In most cases, sit_bitmap_size is smaller than MAX_SIT_BITMAP_SIZE.
> 
> However, in some extreme scenarios, such as 16TB, sit_bitmap_size
> could be larger than MAX_SIT_BITMAP_SIZE.
> 
> In this case, we should recalculate the sit_segments through
> max_sit_bitmap_size to prevent sit_ver_bitmap_bytesize got from
> segment_count_sit in f2fs_write_check_point_pack() being over
> MAX_SIT_BITMAP_SIZE.
> 
> Signed-off-by: Junling Zheng <zhengjunling@huawei.com>
> ---
>  mkfs/f2fs_format.c | 23 ++++++++++++++++-------
>  1 file changed, 16 insertions(+), 7 deletions(-)
> 
> diff --git a/mkfs/f2fs_format.c b/mkfs/f2fs_format.c
> index 645c2aa..3a050e0 100644
> --- a/mkfs/f2fs_format.c
> +++ b/mkfs/f2fs_format.c
> @@ -191,6 +191,22 @@ static int f2fs_prepare_super_block(void)
> 
>  	sit_segments = SEG_ALIGN(blocks_for_sit);
> 
> +	/*
> +	 * In most cases, sit_bitmap_size is smaller than MAX_SIT_BITMAP_SIZE.
> +	 * However, in an extreme scenario(16TB), sit_bitmap_size could be larger
> +	 * than MAX_SIT_BITMAP_SIZE. Thus, we should recalculate the sit_segments
> +	 * to prevent sit_ver_bitmap_bytesize got from segment_count_sit in
> +	 * f2fs_write_check_point_pack() being over MAX_SIT_BITMAP_SIZE.
> +	 */
> +	sit_bitmap_size = (sit_segments << log_blks_per_seg) / 8;
> +
> +	if (sit_bitmap_size > MAX_SIT_BITMAP_SIZE) {
> +		max_sit_bitmap_size = MAX_SIT_BITMAP_SIZE;
> +		sit_segments = max_sit_bitmap_size * 8 >> log_blks_per_seg;
> +		blocks_for_sit = sit_segments << log_blks_per_seg;
> +	} else

Still the minor coding style problem.

IMO, maybe it would be better to limit config.total_sectors with 16TB at
very beginning, so more fields in sb like block_count, segment_count could
be set correctly when we try to format a huge size image. Right?

Thanks,

> +		max_sit_bitmap_size = sit_bitmap_size;
> +
>  	set_sb(segment_count_sit, sit_segments * 2);
> 
>  	set_sb(nat_blkaddr, get_sb(sit_blkaddr) + get_sb(segment_count_sit) *
> @@ -208,13 +224,6 @@ static int f2fs_prepare_super_block(void)
>  	 * This number resizes NAT bitmap area in a CP page.
>  	 * So the threshold is determined not to overflow one CP page
>  	 */
> -	sit_bitmap_size = ((get_sb(segment_count_sit) / 2) <<
> -				log_blks_per_seg) / 8;
> -
> -	if (sit_bitmap_size > MAX_SIT_BITMAP_SIZE)
> -		max_sit_bitmap_size = MAX_SIT_BITMAP_SIZE;
> -	else
> -		max_sit_bitmap_size = sit_bitmap_size;
> 
>  	/*
>  	 * It should be reserved minimum 1 segment for nat.
> --
> 1.9.1
> 
> 
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