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

[Jaegeuk Kim <jaegeuk@kernel.org>]

Hi Junling,

On Thu, Feb 18, 2016 at 04:59:04PM +0800, Junling Zheng wrote:
> 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 | 24 +++++++++++++++++-------
>  1 file changed, 17 insertions(+), 7 deletions(-)
> 
> diff --git a/mkfs/f2fs_format.c b/mkfs/f2fs_format.c
> index 645c2aa..24b2cc1 100644
> --- a/mkfs/f2fs_format.c
> +++ b/mkfs/f2fs_format.c
> @@ -191,6 +191,23 @@ 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
> +		max_sit_bitmap_size = sit_bitmap_size;

Codling style.
if {
} else {
}

Anyway, what about just redefining MAX_SIT_BITMAP_SIZE as
(ALIGN(F2FS_MAX_SEGMENT, SIT_ENTRY_PER_BLOCK) / 8) ?

Thanks,

> +
>  	set_sb(segment_count_sit, sit_segments * 2);
>  
>  	set_sb(nat_blkaddr, get_sb(sit_blkaddr) + get_sb(segment_count_sit) *
> @@ -208,13 +225,6 @@ 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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