[PATCH 4.19 341/346] xen/xenbus/xen_bus_type: Support will_handle watch callback

[Greg Kroah-Hartman]

From: SeongJae Park <sjp...@amazon.de>

commit be987200fbaceaef340872841d4f7af2c5ee8dc3 upstream.

This commit adds support of the 'will_handle' watch callback for
'xen_bus_type' users.

This is part of XSA-349

Cc: sta...@vger.kernel.org
Signed-off-by: SeongJae Park <sjp...@amazon.de>
Reported-by: Michael Kurth <m...@amazon.de>
Reported-by: Pawel Wieczorkiewicz <wipa...@amazon.de>
Reviewed-by: Juergen Gross <jgr...@suse.com>
Signed-off-by: Juergen Gross <jgr...@suse.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/xen/xenbus/xenbus.h       |    2 ++
 drivers/xen/xenbus/xenbus_probe.c |    3 ++-
 2 files changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/xen/xenbus/xenbus.h
+++ b/drivers/xen/xenbus/xenbus.h
@@ -44,6 +44,8 @@ struct xen_bus_type {
        int (*get_bus_id)(char bus_id[XEN_BUS_ID_SIZE], const char *nodename);
        int (*probe)(struct xen_bus_type *bus, const char *type,
                     const char *dir);
+       bool (*otherend_will_handle)(struct xenbus_watch *watch,
+                                    const char *path, const char *token);
        void (*otherend_changed)(struct xenbus_watch *watch, const char *path,
                                 const char *token);
        struct bus_type bus;
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -136,7 +136,8 @@ static int watch_otherend(struct xenbus_
                container_of(dev->dev.bus, struct xen_bus_type, bus);
 
        return xenbus_watch_pathfmt(dev, &dev->otherend_watch,
-                                   NULL, bus->otherend_changed,
+                                   bus->otherend_will_handle,
+                                   bus->otherend_changed,
                                    "%s/%s", dev->otherend, "state");
 }