On Sun, Apr 28, 2013 at 6:29 PM, NeilBrown <neilb@xxxxxxx> wrote: > On Fri, 26 Apr 2013 14:35:27 -0700 Dan Williams <djbw@xxxxxx> wrote: [..] > which looks odd as when that expands out, we add Q_old to Q_old and as '+' > is 'xor', it disappears. Maybe you mean: > > Q_new = Q_sub + g^i * Di_new > ?? > > This is exactly the sort of thing I wanted to see, but I hoped it wouldn't > confuse me like it seems to be doing :-) Sorry, yes for completeness the approach includes all the modified data blocks (Di...Dm) and zero pages for the unmodified blocks in the gen_syndrome. Q_sub = Q_old + g^i * Di_old ... + g^m * Dm_old + (zero blocks) Q_new = Q_sub + g^i *Di_new ... + g^m * Dm_new + (zero blocks) For David, we're using vector processing (SSE) in gen_syndrome() rather than individual multiplications by table lookup. -- Dan -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
