Re: [f2fs-dev] (3) [PATCH] libf2fs: Fix calculation of usable segments for single zoned

[Yonggil S. <yon...@sa...>]

> > On 2024/10/7 13:21, Yonggil Song wrote:
> > > There was a bug that did not subtract the super block area when calculating
> > > the usable segments for a single zoned device with a conventional zone.
> > > This bug 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 fixes the bug by subtracting the super block area when there is
> > > only one zoned device.
> > > 
> > > Signed-off-by: Yonggil Song <yon...@sa...>
> > > ---
> > >   lib/libf2fs_zoned.c | 5 +++++
> > >   1 file changed, 5 insertions(+)
> > > 
> > > diff --git a/lib/libf2fs_zoned.c b/lib/libf2fs_zoned.c
> > > index 89ba5ad73a76..cc5c064b7e3e 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 we don't format zoned device, it doesn't need to do this?
> > 
> > Thanks,
> > 
> Yes, single zoned block only needs this.
> 
> legacy block just return a segment_count_main.
> 
> thanks.
Sorry, I misunderstood.
I'll resend v2 with zoned block checker.

thanks.
> > > +	if (c.ndevs == 1)
> >  > +		usable_segs -= (get_sb(segment0_blkaddr) >> get_sb(log_blocks_per_seg));> +
> > >   	return usable_segs;
> > >   #endif
> > >   	return get_sb(segment_count_main);