On Thu, 14 Feb 2008, Pekka Enberg wrote: > Hi Nishanth, > > On Thu, Feb 14, 2008 at 7:38 PM, Nishanth Aravamudan <[EMAIL PROTECTED]> > wrote: > > Is it just me, or does > > > > ((user_addr + iov[seg].iov_len + PAGE_SIZE - 1)/PAGE_SIZE - > > user_addr/PAGE_SIZE) > > > > not simplify to > > > > = ((iov[seg].iov_len + PAGE_SIZE - 1)/PAGE_SIZE + > > user_addr/PAGE_SIZE - user_addr/PAGE_SIZE) > > > > = ((iov[seg].iov_len + PAGE_SIZE - 1)/PAGE_SIZE) > > > > = DIV_ROUND_UP(iov[seg].iov_len, PAGE_SIZE) > > > > CMIIW. > > I double-checked this and I believe you're correct. It's simpler to > see when you do: > > x = user_addr > y = iov[seg].iov_len > z = PAGE_SIZE > > So > > (x + y + z - 1)/z - x/z > > = [x + (y + z - 1)]/z - x/z > > = [xz + z(y + z - 1)]/z^2 - x/z > > = x/z + (y + z - 1)/z - x/z > > And the rest follows from your simplifications.
It doesn't work: ((3+4+5-1)/5) - (3/5) = 2 ((4+5-1)/5) = 1 julia -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
