Re: [PATCH 1/2 v2] f2fs: fix wrong calculation of block age

[Chao Yu]

On 2023/2/1 20:23, qixiaoyu wrote:
> > > How about updating as below to avoid lossing accuracy if new is less than 100?
> > >
> > > return div_u64(new * (100 - LAST_AGE_WEIGHT), 100) +
> > > 		div_u64(old * LAST_AGE_WEIGHT, 100);
> > >
> > > Thanks,
> >
> > We want to avoid overflow by doing the division first. To keep the accuracy, how

Alright,

> > about updating as below:
> >
> > 	res = div_u64_rem(new, 100, &rem_new) * (100 - LAST_AGE_WEIGHT)
> > 		+ div_u64_rem(old, 100, &rem_old) * LAST_AGE_WEIGHT;
> > 	res += rem_new * (100 - LAST_AGE_WEIGHT) / 100 + rem_old * LAST_AGE_WEIGHT / 100;
> > 	return res;

if (rem_new)
	res += rem_new * (100 - LAST_AGE_WEIGHT) / 100;
if (rem_old)
	res += rem_old * LAST_AGE_WEIGHT / 100;

Otherwise, it looks fine to me. :)

Thanks,

> > Thanks,
>
> Friendly ping
>
> > > >    }
> > > >    /* This returns a new age and allocated blocks in ei */