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?
>
> 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
>
