[Xen-devel] [PATCH 1/1] xen-netback: add reference from xenvif to backend_info to facilitate coredump analysis

[Dongli Zhang <dongli.zhang@xxxxxxxxxx>]

During coredump analysis, it is not easy to obtain the address of
backend_info in xen-netback.

So far there are two ways to obtain backend_info:

1. Do what xenbus_device_find() does for vmcore to find the xenbus_device
and then derive it from dev_get_drvdata().

2. Extract backend_info from callstack of xenwatch (e.g., netback_remove()
or frontend_changed()).

This patch adds a reference from xenvif to backend_info so that it would be
much more easier to obtain backend_info during coredump analysis.

Signed-off-by: Dongli Zhang <dongli.zhang@xxxxxxxxxx>
---
 drivers/net/xen-netback/common.h | 18 ++++++++++++++++++
 drivers/net/xen-netback/xenbus.c | 17 +----------------
 2 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index 936c0b3..05847eb 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -248,6 +248,22 @@ struct xenvif_hash {
        struct xenvif_hash_cache cache;
 };
 
+struct backend_info {
+       struct xenbus_device *dev;
+       struct xenvif *vif;
+
+       /* This is the state that will be reflected in xenstore when any
+        * active hotplug script completes.
+        */
+       enum xenbus_state state;
+
+       enum xenbus_state frontend_state;
+       struct xenbus_watch hotplug_status_watch;
+       u8 have_hotplug_status_watch:1;
+
+       const char *hotplug_script;
+};
+
 struct xenvif {
        /* Unique identifier for this interface. */
        domid_t          domid;
@@ -283,6 +299,8 @@ struct xenvif {
        struct xenbus_watch credit_watch;
        struct xenbus_watch mcast_ctrl_watch;
 
+       struct backend_info *be;
+
        spinlock_t lock;
 
 #ifdef CONFIG_DEBUG_FS
diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
index 330ddb6..41c9e8f 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c
@@ -22,22 +22,6 @@
 #include <linux/vmalloc.h>
 #include <linux/rtnetlink.h>
 
-struct backend_info {
-       struct xenbus_device *dev;
-       struct xenvif *vif;
-
-       /* This is the state that will be reflected in xenstore when any
-        * active hotplug script completes.
-        */
-       enum xenbus_state state;
-
-       enum xenbus_state frontend_state;
-       struct xenbus_watch hotplug_status_watch;
-       u8 have_hotplug_status_watch:1;
-
-       const char *hotplug_script;
-};
-
 static int connect_data_rings(struct backend_info *be,
                              struct xenvif_queue *queue);
 static void connect(struct backend_info *be);
@@ -472,6 +456,7 @@ static int backend_create_xenvif(struct backend_info *be)
                return err;
        }
        be->vif = vif;
+       vif->be = be;
 
        kobject_uevent(&dev->dev.kobj, KOBJ_ONLINE);
        return 0;
-- 
2.7.4


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