Re: [f2fs-dev] [PATCH v2] libf2fs: Fix calculation of usable segments for single

[Jaegeuk Kim via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

On 10/10, Yonggil Song wrote:
> There was a problem that did not subtract the super block area when calculating
> the usable segments for a single zoned device with a conventional zone.
> This resulted in incorrect the overprovision and reserved area.
> 
> 	<256MiB legacy block + zoned block w/ 32MiB zone size>
> 	Info: Overprovision ratio = 3.570%
> 	Info: Overprovision segments = 656 (GC reserved = 560)
> 
> 	<8 conventional zone + 1016 sequential zone w/ 32MiB zone size>
> 	Info: Overprovision ratio = 3.700%
> 	Info: Overprovision segments = 676 (GC reserved = 578)
> 
> This patch addresses the problem by subtracting the super block area when
> there is only one zoned device.
> 
> Signed-off-by: Yonggil Song <yonggil.song@samsung.com>
> ---
>  lib/libf2fs_zoned.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/lib/libf2fs_zoned.c b/lib/libf2fs_zoned.c
> index 89ba5ad73a76..1a0985378789 100644
> --- a/lib/libf2fs_zoned.c
> +++ b/lib/libf2fs_zoned.c
> @@ -555,6 +555,11 @@ uint32_t f2fs_get_usable_segments(struct f2fs_super_block *sb)
>  	}
>  	usable_segs -= (get_sb(main_blkaddr) - get_sb(segment0_blkaddr)) >>
>  						get_sb(log_blocks_per_seg);
> +
> +	/* single zoned device needs to remove a super block area */
> +	if (c.ndevs == 1 && c.devices[0].zoned_model == F2FS_ZONED_HM)

Does this work?

> +		usable_segs -= (get_sb(segment0_blkaddr) >> get_sb(log_blocks_per_seg));
> +
>  	return usable_segs;
>  #endif
>  	return get_sb(segment_count_main);
> -- 
> 2.43.0


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