David Howells wrote: > Willem de Bruijn <willemdebruijn.kernel@xxxxxxxxx> wrote: > > > The commit message mentions MSG_SPLICE_PAGES as an internal flag. > > > > It can be passed from userspace. The code anticipates that and checks > > preconditions. > > Should I add a separate field in the in-kernel msghdr struct for such internal > flags? That would also avoid putting an internal flag in the same space as > the uapi flags. That would work, if no cost to common paths that don't need it. A not very pretty alternative would be to add an an extra arg to each sendmsg handler that is used only when called from sendpage. There are a few other internal MSG_.. flags, such as MSG_SENDPAGE_NOPOLICY. Those are all limited to sendpage, and ignored in sendmsg, I think. Which would explain why it was clearly safe to add them.
