> Date: Mon, 22 Feb 2021 10:10:21 +0100
> From: Martin Pieuchot <m...@openbsd.org>
>
> On 16/02/21(Tue) 11:20, Martin Pieuchot wrote:
> > Start by moving `pgo_fault' handler outside of uvm_fault_lower().
> >
> > If a page has a backing object that prefer to handler to fault itself
> > the locking will be different, so keep it under KERNEL_LOCK() for the
> > moment and make it separate from the rest of uvm_fault_lower().
> >
> > ok?
>
> Anyone?
This diverges from NetBSD; you think that's a good idea?
> > Index: uvm/uvm_fault.c
> > ===================================================================
> > RCS file: /cvs/src/sys/uvm/uvm_fault.c,v
> > retrieving revision 1.115
> > diff -u -p -r1.115 uvm_fault.c
> > --- uvm/uvm_fault.c 16 Feb 2021 09:10:17 -0000 1.115
> > +++ uvm/uvm_fault.c 16 Feb 2021 10:13:58 -0000
> > @@ -598,10 +598,37 @@ uvm_fault(vm_map_t orig_map, vaddr_t vad
> > /* case 1: fault on an anon in our amap */
> > error = uvm_fault_upper(&ufi, &flt, anons, fault_type);
> > } else {
> > - /* case 2: fault on backing object or zero fill */
> > - KERNEL_LOCK();
> > - error = uvm_fault_lower(&ufi, &flt, pages, fault_type);
> > - KERNEL_UNLOCK();
> > + struct uvm_object *uobj = ufi.entry->object.uvm_obj;
> > +
> > + /*
> > + * if the desired page is not shadowed by the amap and
> > + * we have a backing object, then we check to see if
> > + * the backing object would prefer to handle the fault
> > + * itself (rather than letting us do it with the usual
> > + * pgo_get hook). the backing object signals this by
> > + * providing a pgo_fault routine.
> > + */
> > + if (uobj != NULL && uobj->pgops->pgo_fault != NULL) {
> > + KERNEL_LOCK();
> > + error = uobj->pgops->pgo_fault(&ufi,
> > + flt.startva, pages, flt.npages,
> > + flt.centeridx, fault_type, flt.access_type,
> > + PGO_LOCKED);
> > + KERNEL_UNLOCK();
> > +
> > + if (error == VM_PAGER_OK)
> > + error = 0;
> > + else if (error == VM_PAGER_REFAULT)
> > + error = ERESTART;
> > + else
> > + error = EACCES;
> > + } else {
> > + /* case 2: fault on backing obj or zero fill */
> > + KERNEL_LOCK();
> > + error = uvm_fault_lower(&ufi, &flt, pages,
> > + fault_type);
> > + KERNEL_UNLOCK();
> > + }
> > }
> > }
> >
> > @@ -1054,26 +1081,6 @@ uvm_fault_lower(struct uvm_faultinfo *uf
> > struct vm_anon *anon = NULL;
> > vaddr_t currva;
> > voff_t uoff;
> > -
> > - /*
> > - * if the desired page is not shadowed by the amap and we have a
> > - * backing object, then we check to see if the backing object would
> > - * prefer to handle the fault itself (rather than letting us do it
> > - * with the usual pgo_get hook). the backing object signals this by
> > - * providing a pgo_fault routine.
> > - */
> > - if (uobj != NULL && uobj->pgops->pgo_fault != NULL) {
> > - result = uobj->pgops->pgo_fault(ufi, flt->startva, pages,
> > - flt->npages, flt->centeridx, fault_type, flt->access_type,
> > - PGO_LOCKED);
> > -
> > - if (result == VM_PAGER_OK)
> > - return (0); /* pgo_fault did pmap enter */
> > - else if (result == VM_PAGER_REFAULT)
> > - return ERESTART; /* try again! */
> > - else
> > - return (EACCES);
> > - }
> >
> > /*
> > * now, if the desired page is not shadowed by the amap and we have
> >
>
>
