On Wed, Mar 21, 2012 at 5:34 PM, Nicholas A. Bellinger <nab@xxxxxxxxxxxxxxx> wrote: > - tmp = rounddown((max_sectors * block_size), PAGE_SIZE); > - aligned_max_sectors = (tmp / block_size); > + aligned_max_sectors = rounddown(max_sectors, PAGE_SIZE / block_size); > > The PAGE_SIZE / block_size calculation looks bogus to me here.. What's bogus about it? As long as block_size is a power of 2 (which I believe we assume many other places), it should be fine. As a concrete example, if block_size is 512, instead of multiplying max_sectors by 512, rounding down to the nearest 4096 and then dividing by 512 again, we just round down to the nearest (4096/512) == 8 directly. Basically if we want to limit the size of the IO to a PAGE_SIZE multiple, and we are dealing in block_size sectors, we should make sure that the IO size is limited to be a multiple of PAGE_SIZE/block_size sectors. It's hard to explain but I if you think about it, it becomes pretty clear. Clearer to me than a 64-bit multiple followed by do_div, at least. - R. -- To unsubscribe from this list: send the line "unsubscribe target-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
