Willem de Bruijn <willemdebruijn.kernel@xxxxxxxxx> wrote: > 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. Actually, it might be tricky. __ip_append_data() doesn't take a msghdr struct pointer per se. The "void *from" argument *might* point to one - but it depends on seeing a MSG_SPLICE_PAGES or MSG_ZEROCOPY flag, otherwise we don't know. Possibly this changes if sendpage goes away. > 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. Should those be moved across to the internal flags with MSG_SPLICE_PAGES? David
