[PATCH 5/6] xenbus: process be_watch events in xenwatch multithreading

[Dongli Zhang <dongli.zhang@oracle.com>]

This is the 5th patch of a (6-patch) patch set.

With this patch, watch event in relative path pattern
'backend/<pvdev>/<domid>i/...' can be processed in per-domU xenwatch
thread.

Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
---
 drivers/xen/xenbus/xenbus_probe.c         |  2 +-
 drivers/xen/xenbus/xenbus_probe_backend.c | 32 +++++++++++++++++++++++++++++++
 include/xen/xenbus.h                      |  2 ++
 3 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index ba0644c..aa1b15a 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -552,7 +552,7 @@ int xenbus_probe_devices(struct xen_bus_type *bus)
 }
 EXPORT_SYMBOL_GPL(xenbus_probe_devices);
 
-static unsigned int char_count(const char *str, char c)
+unsigned int char_count(const char *str, char c)
 {
 	unsigned int i, ret = 0;
 
diff --git a/drivers/xen/xenbus/xenbus_probe_backend.c b/drivers/xen/xenbus/xenbus_probe_backend.c
index b0bed4f..50df86a 100644
--- a/drivers/xen/xenbus/xenbus_probe_backend.c
+++ b/drivers/xen/xenbus/xenbus_probe_backend.c
@@ -211,9 +211,41 @@ static void backend_changed(struct xenbus_watch *watch,
 	xenbus_dev_changed(path, &xenbus_backend);
 }
 
+static domid_t path_to_domid(const char *path)
+{
+	const char *p = path;
+	domid_t domid = 0;
+
+	while (*p) {
+		if (*p < '0' || *p > '9')
+			break;
+		domid = (domid << 3) + (domid << 1) + (*p - '0');
+		p++;
+	}
+
+	return domid;
+}
+
+/* path: backend/<pvdev>/<domid>/... */
+static domid_t be_get_domid(struct xenbus_watch *watch,
+			    const char *path,
+			    const char *token)
+{
+	const char *p = path;
+
+	if (char_count(path, '/') < 2)
+		return 0;
+
+	p = strchr(p, '/') + 1;
+	p = strchr(p, '/') + 1;
+
+	return path_to_domid(p);
+}
+
 static struct xenbus_watch be_watch = {
 	.node = "backend",
 	.callback = backend_changed,
+	.get_domid = be_get_domid,
 };
 
 static int read_frontend_details(struct xenbus_device *xendev)
diff --git a/include/xen/xenbus.h b/include/xen/xenbus.h
index 4ac2cee..79d784e 100644
--- a/include/xen/xenbus.h
+++ b/include/xen/xenbus.h
@@ -241,6 +241,8 @@ extern const struct file_operations xen_xenbus_fops;
 extern struct xenstore_domain_interface *xen_store_interface;
 extern int xen_store_evtchn;
 
+unsigned int char_count(const char *str, char c);
+
 void mtwatch_create_domain(domid_t domid);
 void mtwatch_put_domain(domid_t domid);
 
-- 
2.7.4