On Fri, Apr 08, 2022 at 11:08:29PM -0700, Hugh Dickins wrote: > > > > Either way I'd rather do this optimization in iov_iter_zero rather > > than hiding it in tmpfs. > > Let's see what others say. I think we would all prefer clear_user() to be > enhanced, and hack around it neither here in tmpfs nor in iov_iter_zero(). > But that careful work won't get done by magic, nor by me. I agree with that. > And iov_iter_zero() has to deal with a wider range of possibilities, > when pulling in cache lines of ZERO_PAGE(0) will be less advantageous, > than in tmpfs doing a large dd - the case I'm aiming not to regress here > (tmpfs has been copying ZERO_PAGE(0) like this for years). Maybe. OTOH I'd hate to have iov_iter_zero not used much because it sucks too much. So how can we entice someone with the right knowledge to implement a decent clear_user for x86?
