packages/vfs: patch to fix session directory creation

packages/genodelabs/depot-targets.nix

@@ -280,7 +280,10 @@ in {
   vbox5-nova = vbox5';
   verify = { };
   vesa_drv.portInputs = with ports; [ libc x86emu ];
-  vfs.outputs = [ "out" "lib" ];
+  vfs = {
+    outputs = [ "out" "lib" ];
+    patches = [ ./patches/vfs.patch ];
+  };
   vfs_audit = { };
   vfs_block = { };
   vfs_fatfs = { };

packages/genodelabs/patches/vfs.patch

@@ -0,0 +1,78 @@
+From a3063497d9aaf6bf06a3797804135105ad5f3bad Mon Sep 17 00:00:00 2001
+From: Emery Hemingway <ehmry@posteo.net>
+Date: Thu, 3 Dec 2020 12:19:10 +0100
+Subject: [PATCH] vfs: create missing root directories for writeable sessions
+
+This is the expected behavior.
+---
+ repos/os/src/server/vfs/main.cc | 47 ++++++++++++++++++++++++++++++---
+ 1 file changed, 43 insertions(+), 4 deletions(-)
+
+diff --git a/repos/os/src/server/vfs/main.cc b/repos/os/src/server/vfs/main.cc
+index b780b1fdd7..358afd28a9 100644
+--- a/repos/os/src/server/vfs/main.cc
++++ b/repos/os/src/server/vfs/main.cc
+@@ -841,6 +841,41 @@ class Vfs_server::Root : public Genode::Root_component<Session_component>,
+ 				Genode::Signal_transmitter(_reactivate_handler).submit();
+ 		}
+ 
++		/**
++		 * Open a directory, ensuring all parent directories exists.
++		 */
++		void _create_session_dir(Path const &path)
++		{
++			using namespace Genode;
++			typedef Vfs::Directory_service::Opendir_result Result;
++
++			Vfs_handle *handle { nullptr };
++			Vfs::File_system &vfs = _vfs_env.root_dir();
++
++			switch (vfs.opendir(path.string(), true, &handle, _vfs_heap)) {
++			case Result::OPENDIR_OK:
++				handle->close();
++				return;
++			case Result::OPENDIR_ERR_NODE_ALREADY_EXISTS:
++				if (vfs.directory(path.string())) return;
++				break;
++			case Result::OPENDIR_ERR_LOOKUP_FAILED: {
++				Path parent = path;
++				parent.strip_last_element();
++				_create_session_dir(parent.string());
++				auto res = vfs.opendir(path.string(), true, &handle, _vfs_heap);
++				if (res == Result::OPENDIR_OK) {
++					handle->close();
++					return;
++				}
++			}
++			default: break;
++			}
++
++			error("cannot create session root at ", path);
++			throw Service_denied();
++		}
++
+ 	protected:
+ 
+ 		Session_component *_create_session(const char *args) override
+@@ -916,10 +951,14 @@ class Vfs_server::Root : public Genode::Root_component<Session_component>,
+ 			}
+ 
+ 			/* check if the session root exists */
+-			if (!((session_root == "/")
+-			 || _vfs_env.root_dir().directory(session_root.base()))) {
+-				error("session root '", session_root, "' not found for '", label, "'");
+-				throw Service_denied();
++			if (session_root != "/") {
++				if (!_vfs_env.root_dir().directory(session_root.base())) {
++					if (writeable) { _create_session_dir(session_root); }
++					else {
++						error("session root '", session_root, "' not found for '", label, "'");
++						throw Service_denied();
++					}
++				}
+ 			}
+ 
+ 			Session_component *session = new (md_alloc())
+-- 
+2.29.2
+