vm: object: add prefetch function to fetch missing pages

include/kernel/vm-object.h

@@ -98,6 +98,16 @@ extern kern_status_t vm_object_attach_cow(
 	struct vm_object *vmo,
 	unsigned long *irq_flags);
 
+/* prefetch any missing pages in the specified range of a vm-object.
+ * any lazy-allocated pages will be allocated.
+ * any missing pages will be requested from the vm-controller, if one is
+ * attached. */
+extern kern_status_t vm_object_prefetch(
+	struct vm_object *vo,
+	off_t offset,
+	size_t length,
+	unsigned long *irq_flags);
+
 extern struct vm_page *vm_object_get_page(
 	struct vm_object *vo,
 	off_t offset,

syscall/vm-object.c

@@ -58,20 +58,31 @@ kern_status_t sys_vm_object_read(
 
 	struct object *obj = NULL;
 	handle_flags_t flags = 0;
+	unsigned long irq_flags = 0;
+	task_lock_irqsave(self, &irq_flags);
 	kern_status_t status = task_resolve_handle(self, object, &obj, &flags);
+	task_unlock_irqrestore(self, irq_flags);
+	put_current_task(self);
+
 	if (status != KERN_OK) {
-		put_current_task(self);
 		return status;
 	}
 
 	struct vm_object *vmo = vm_object_cast(obj);
 	if (!vmo) {
-		put_current_task(self);
+		object_unref(obj);
 		return KERN_INVALID_ARGUMENT;
 	}
 
-	status = vm_object_read(vmo, dst, offset, count, nr_read);
-	put_current_task(self);
+	vm_object_lock_irqsave(vmo, &irq_flags);
+	status = vm_object_prefetch(vmo, offset, count, &irq_flags);
+	if (status == KERN_OK) {
+		status = vm_object_read(vmo, dst, offset, count, nr_read);
+	}
+
+	vm_object_unlock_irqrestore(vmo, irq_flags);
+	object_unref(obj);
+
 	return status;
 }
 
@@ -97,20 +108,25 @@ kern_status_t sys_vm_object_write(
 
 	struct object *obj = NULL;
 	handle_flags_t flags = 0;
+	unsigned long irq_flags = 0;
+	task_lock_irqsave(self, &irq_flags);
 	kern_status_t status = task_resolve_handle(self, object, &obj, &flags);
+	task_unlock_irqrestore(self, irq_flags);
+	put_current_task(self);
+
 	if (status != KERN_OK) {
-		put_current_task(self);
 		return status;
 	}
 
 	struct vm_object *vmo = vm_object_cast(obj);
 	if (!vmo) {
-		put_current_task(self);
 		return KERN_INVALID_ARGUMENT;
 	}
 
+	vm_object_lock_irqsave(vmo, &irq_flags);
 	status = vm_object_write(vmo, src, offset, count, nr_written);
-	put_current_task(self);
+	vm_object_unlock_irqrestore(vmo, irq_flags);
+
 	return status;
 }
 
@@ -162,13 +178,28 @@ kern_status_t sys_vm_object_copy(
 	put_current_task(self);
 
 	struct vm_object *dst_vmo = vm_object_cast(dst_obj);
+	if (!dst_vmo) {
+		return KERN_INVALID_ARGUMENT;
+	}
+
 	struct vm_object *src_vmo = vm_object_cast(src_obj);
-	if (!dst_vmo || !src_vmo) {
-		object_unref(src_obj);
+	if (!src_vmo) {
 		object_unref(dst_obj);
 		return KERN_INVALID_ARGUMENT;
 	}
 
+	unsigned long irq_flags = 0;
+	vm_object_lock_irqsave(src_vmo, &irq_flags);
+	status = vm_object_prefetch(src_vmo, src_offset, count, &irq_flags);
+	vm_object_unlock_irqrestore(src_vmo, irq_flags);
+
+	if (status != KERN_OK) {
+		object_unref(src_obj);
+		object_unref(dst_obj);
+		return status;
+	}
+
+	vm_object_lock_pair_irqsave(src_vmo, dst_vmo, &irq_flags);
 	status = vm_object_copy(
 		dst_vmo,
 		dst_offset,
@@ -176,6 +207,7 @@ kern_status_t sys_vm_object_copy(
 		src_offset,
 		count,
 		nr_copied);
+	vm_object_unlock_pair_irqrestore(src_vmo, dst_vmo, irq_flags);
 
 	object_unref(src_obj);
 	object_unref(dst_obj);

vm/vm-object.c

@@ -516,6 +516,33 @@ static kern_status_t request_page(
 	return status;
 }
 
+kern_status_t vm_object_prefetch(
+	struct vm_object *vo,
+	off_t offset,
+	size_t length,
+	unsigned long *irq_flags)
+{
+	offset &= ~VM_PAGE_MASK;
+	if (length & VM_PAGE_MASK) {
+		length &= ~VM_PAGE_MASK;
+		length += VM_PAGE_SIZE;
+	}
+
+	for (off_t i = offset; i < offset + length; i += VM_PAGE_SIZE) {
+		struct vm_page *pg = vm_object_get_page(
+			vo,
+			i,
+			VMO_ALLOCATE_MISSING_PAGE | VMO_REQUEST_MISSING_PAGE,
+			irq_flags);
+		if (!pg) {
+			/* TODO get error code from vm_object_get_page */
+			return KERN_NO_MEMORY;
+		}
+	}
+
+	return KERN_OK;
+}
+
 struct vm_page *vm_object_get_page(
 	struct vm_object *vo,
 	off_t offset,