On Fri, 8 Apr 2022 23:08:29 -0700 (PDT) Hugh Dickins <hughd@xxxxxxxxxx> 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. > > 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). We do need something to get 5.18 fixed. Christoph, do you think we should proceed with this patch for 5.18?
