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?
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
