Merge tag 'for-linus-5.11-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen updates from Juergen Gross:
 "Fixes for security issues just having been disclosed:

   - a five patch series for fixing of XSA-349 (DoS via resource
     depletion in Xen dom0)

   - a patch fixing XSA-350 (access of stale pointer in a Xen dom0)"

* tag 'for-linus-5.11-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen-blkback: set ring->xenblkd to NULL after kthread_stop()
  xenbus/xenbus_backend: Disallow pending watch messages
  xen/xenbus: Count pending messages for each watch
  xen/xenbus/xen_bus_type: Support will_handle watch callback
  xen/xenbus: Add 'will_handle' callback support in xenbus_watch_path()
  xen/xenbus: Allow watches discard events before queueing

include/xen/xenbus.h

@@ -61,6 +61,15 @@ struct xenbus_watch
 	/* Path being watched. */
 	const char *node;
 
+	unsigned int nr_pending;
+
+	/*
+	 * Called just before enqueing new event while a spinlock is held.
+	 * The event will be discarded if this callback returns false.
+	 */
+	bool (*will_handle)(struct xenbus_watch *,
+			      const char *path, const char *token);
+
 	/* Callback (executed in a process context with no locks held). */
 	void (*callback)(struct xenbus_watch *,
 			 const char *path, const char *token);
@@ -197,10 +206,14 @@ void xenbus_probe(struct work_struct *);
 
 int xenbus_watch_path(struct xenbus_device *dev, const char *path,
 		      struct xenbus_watch *watch,
+		      bool (*will_handle)(struct xenbus_watch *,
+					  const char *, const char *),
 		      void (*callback)(struct xenbus_watch *,
 				       const char *, const char *));
-__printf(4, 5)
+__printf(5, 6)
 int xenbus_watch_pathfmt(struct xenbus_device *dev, struct xenbus_watch *watch,
+			 bool (*will_handle)(struct xenbus_watch *,
+					     const char *, const char *),
 			 void (*callback)(struct xenbus_watch *,
 					  const char *, const char *),
 			 const char *pathfmt, ...);