> > if (c->gc_stats.in_use <= BCH_WRITEBACK_FRAGMENT_THRESHOLD_MID) {
> > - fp_term = dc->writeback_rate_fp_term_low *
> > + fp_term = (int64_t)dc->writeback_rate_fp_term_low *
> > (c->gc_stats.in_use - BCH_WRITEBACK_FRAGMENT_THRESHOLD_LOW);
> > } else if (c->gc_stats.in_use <= BCH_WRITEBACK_FRAGMENT_THRESHOLD_HIGH) {
> > - fp_term = dc->writeback_rate_fp_term_mid *
> > + fp_term = (int64_t)dc->writeback_rate_fp_term_mid *
> > (c->gc_stats.in_use - BCH_WRITEBACK_FRAGMENT_THRESHOLD_MID);
> > } else {
> > - fp_term = dc->writeback_rate_fp_term_high *
> > + fp_term = (int64_t)dc->writeback_rate_fp_term_high *
> > (c->gc_stats.in_use - BCH_WRITEBACK_FRAGMENT_THRESHOLD_HIGH);
> > }
> > fps = div_s64(dirty, dirty_buckets) * fp_term;
> >
>
> Hmm, should such thing be handled by compiler ? Otherwise this kind of
> potential overflow issue will be endless time to time.
>
> I am not a compiler expert, should we have to do such explicit type cast
> all the time ?
We do to get a 64bit product from two 32bit values.
An alternative for the above would be:
fp_term = c->gc_stats.in_use - BCH_WRITEBACK_FRAGMENT_THRESHOLD_HIGH;
fp_term *= dc->writeback_rate_fp_term_high;
I hope BCH_WRITEBACK_FRAGMENT_THRESHOLD_LOW is zero :-)
David
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