[PATCH v2 5/8] tools/ocaml/xenstored: Automatically resume when possible

["Edwin Török" <edvin.torok@citrix.com>]

When a `db` file exists use it to resume oxenstored.
It will contains a xenstore tree, domain reconnection info, and watches.

It is currently missing data about all active socket connections,
so a toolstack should ideally be stopped and restarted too.

Tell systemd about oxenstored's PID and allow it to restart on success.

This should make updating oxenstored as easy as:
`systemctl stop -s SIGTERM xenstored` on a suitable xenstored version.

Signed-off-by: Edwin Török <edvin.torok@citrix.com>
Reviewed-by: Pau Ruiz Safont <pau.safont@citrix.com>
Reviewed-by: Christian Lindig <christian.lindig@citrix.com>

---
Changed since V1:
* post publicly now that the XSA is out
---
 tools/ocaml/xenstored/xenstored.ml | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/tools/ocaml/xenstored/xenstored.ml b/tools/ocaml/xenstored/xenstored.ml
index 6b5381962b..500d96753b 100644
--- a/tools/ocaml/xenstored/xenstored.ml
+++ b/tools/ocaml/xenstored/xenstored.ml
@@ -292,9 +292,8 @@ let _ =
 	List.iter (fun path ->
 		Store.write store Perms.Connection.full_rights path "") Store.Path.specials;
 
-	let filename = Paths.xen_run_stored ^ "/db" in
-	if cf.restart && Sys.file_exists filename then (
-		DB.from_file store domains cons filename;
+	if cf.restart && Sys.file_exists Disk.xs_daemon_database then (
+		DB.from_file store domains cons Disk.xs_daemon_database;
 		Event.bind_dom_exc_virq eventchn
 	) else (
 		if !Disk.enable then (
@@ -320,7 +319,7 @@ let _ =
 	Sys.set_signal Sys.sigpipe Sys.Signal_ignore;
 
 	if cf.activate_access_log then begin
-		let post_rotate () = DB.to_file store cons (Paths.xen_run_stored ^ "/db") in
+		let post_rotate () = DB.to_file store cons Disk.xs_daemon_database in
 		Logging.init_access_log post_rotate
 	end;
 
@@ -494,5 +493,8 @@ let _ =
 				raise exc
 	done;
 	info "stopping xenstored";
-	DB.to_file store cons (Paths.xen_run_stored ^ "/db");
+		DB.to_file store cons Disk.xs_daemon_database;
+		(* unlink pidfile so that launch-xenstore works again *)
+		Unixext.unlink_safe pidfile;
+		(match cf.pidfile with Some pidfile -> Unixext.unlink_safe pidfile | None -> ());
 	()
-- 
2.29.2