lib: fs: implement file cleanup using disconnect and detach events

lib/libfs/context.c

@@ -141,6 +141,28 @@ kern_handle_t fs_context_get_vm_controller(const struct fs_context *ctx)
 	return ctx->ctx_vm_controller;
 }
 
+static enum fs_status handle_event(struct fs_context *ctx, xpc_msg_t *msg)
+{
+	switch (msg->msg_event) {
+	case KERN_MSG_EVENT_CONNECTION:
+		kern_logf("received connection");
+		break;
+	case KERN_MSG_EVENT_DISCONNECTION: {
+		struct fs_file *f
+			= fs_context_get_file(ctx, msg->msg_sender.e_port);
+		if (f) {
+			fs_context_close_file(ctx, f);
+		}
+		break;
+	}
+	default:
+		kern_logf("received unknown event");
+		break;
+	}
+
+	return FS_SUCCESS;
+}
+
 static enum fs_status handle_msg(struct fs_context *ctx)
 {
 	xpc_msg_t msg;
@@ -154,6 +176,10 @@ static enum fs_status handle_msg(struct fs_context *ctx)
 		return FS_ERR_INTERNAL_FAILURE;
 	}
 
+	if (msg.msg_type != KERN_MSG_TYPE_DATA) {
+		return handle_event(ctx, &msg);
+	}
+
 	switch (msg.msg_header.hdr_interface) {
 	case INTERFACE_FS:
 		status = fs_context_dispatch_msg(ctx, &msg);
@@ -169,18 +195,43 @@ static enum fs_status handle_msg(struct fs_context *ctx)
 	return FS_SUCCESS;
 }
 
-static enum fs_status handle_page_request(struct fs_context *ctx)
+static enum fs_status handle_page_request_detach(
+	struct fs_context *ctx,
+	equeue_packet_page_request_t *packet,
+	struct file_mapping *mapping)
 {
-	equeue_packet_page_request_t packet;
-	vm_controller_recv(ctx->ctx_vm_controller, &packet);
-	struct file_mapping *mapping = (struct file_mapping *)packet.req_vmo;
-	kern_tracef(
-		"received page request [%zx-%zx] for file %s",
-		packet.req_offset,
-		packet.req_offset + packet.req_length,
+	kern_logf(
+		"received page request (detach) for file %s",
 		mapping->m_file->f_dent->d_name);
 
-	size_t length = packet.req_length;
+	struct fs_file *f = mapping->m_file;
+	switch (mapping->m_type) {
+	case FILE_MAPPING_PRIVATE:
+		queue_delete(&f->f_mappings, &mapping->m_entry);
+		break;
+	default:
+		break;
+	}
+
+	kern_handle_close(mapping->m_vmo);
+	fs_context_free(ctx, mapping);
+
+	fs_context_close_file(ctx, f);
+	return FS_SUCCESS;
+}
+
+static enum fs_status handle_page_request_read(
+	struct fs_context *ctx,
+	equeue_packet_page_request_t *packet,
+	struct file_mapping *mapping)
+{
+	kern_tracef(
+		"received page request (read) [%zx-%zx] for file %s",
+		packet->req_offset,
+		packet->req_offset + packet->req_length,
+		mapping->m_file->f_dent->d_name);
+
+	size_t length = packet->req_length;
 	if (length > TEMP_OBJECT_SIZE) {
 		length = TEMP_OBJECT_SIZE;
 	}
@@ -190,7 +241,7 @@ static enum fs_status handle_page_request(struct fs_context *ctx)
 	enum fs_status status = fs_file_read_at(
 		mapping->m_file,
 		&buf,
-		packet.req_offset,
+		packet->req_offset,
 		length);
 	if (status != FS_SUCCESS) {
 		kern_tracef("map-read failed with code %d", status);
@@ -200,10 +251,34 @@ static enum fs_status handle_page_request(struct fs_context *ctx)
 	vm_controller_supply_pages(
 		ctx->ctx_vm_controller,
 		mapping->m_vmo,
-		packet.req_offset,
+		packet->req_offset,
 		ctx->ctx_temp_object,
 		0,
-		packet.req_length);
+		packet->req_length);
+	return FS_SUCCESS;
+}
+
+static enum fs_status handle_page_request(struct fs_context *ctx)
+{
+	equeue_packet_page_request_t packet;
+	kern_status_t status
+		= vm_controller_recv(ctx->ctx_vm_controller, &packet);
+
+	if (status != KERN_OK) {
+		return KERN_BAD_STATE;
+	}
+
+	struct file_mapping *mapping = (struct file_mapping *)packet.req_vmo;
+
+	switch (packet.req_type) {
+	case PAGE_REQUEST_READ:
+		return handle_page_request_read(ctx, &packet, mapping);
+	case PAGE_REQUEST_DETACH:
+		return handle_page_request_detach(ctx, &packet, mapping);
+	default:
+		kern_logf("unknown page request type %zx", packet.req_type);
+		break;
+	}
 	return FS_SUCCESS;
 }
 
@@ -262,6 +337,16 @@ struct fs_file *fs_context_get_file(struct fs_context *ctx, unsigned long id)
 
 void fs_context_close_file(struct fs_context *ctx, struct fs_file *f)
 {
+	if (f->f_ref > 1) {
+		kern_logf(
+			"reference to file '%s' has been closed",
+			f->f_dent->d_name);
+		f->f_ref--;
+		return;
+	}
+
+	kern_logf("file '%s' has been closed", f->f_dent->d_name);
+	btree_delete(&ctx->ctx_filelist, &f->f_node);
 }
 
 static size_t get_first_path_component(const char *in, char *out, size_t max)

lib/libfs/file.h

@@ -9,6 +9,9 @@
 #include <fs/inode.h>
 
 struct fs_file {
+	/* reference count includes the file descriptor, and any vm-objects
+	 * attached to the file */
+	unsigned int f_ref;
 	/* id of the open file, equal to the koid of the port being used to
 	 * access the file */
 	unsigned long f_id;

lib/libfs/interface/map.c

@@ -105,6 +105,7 @@ extern kern_status_t fs_msg_map(
 
 	kern_handle_t vmo;
 	kern_handle_duplicate(mapping->m_vmo, &vmo);
+	f->f_ref++;
 
 	*out_err = SUCCESS;
 	*out_vmo = vmo;

lib/libfs/interface/open.c

@@ -45,6 +45,7 @@ extern kern_status_t fs_msg_open(
 		return KERN_OK;
 	}
 
+	f->f_ref = 1;
 	f->f_seek = 0;
 	f->f_dent = dent;
 	f->f_inode = dent->d_inode;