linux-kernel - [PATCH v2 1/2] Revert "xen-netback: remove 'hotplug-status' once it has served its purpose"

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Date:   Tue, 22 Feb 2022 01:18:16 +0100
From:   Marek Marczykowski-Górecki 
        <marmarek@...isiblethingslab.com>
To:     linux-kernel@...r.kernel.org
Cc:     Marek Marczykowski-Górecki 
        <marmarek@...isiblethingslab.com>, stable@...r.kernel.org,
        Michael Brown <mcb30@...e.org>, Wei Liu <wei.liu@...nel.org>,
        Paul Durrant <paul@....org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        xen-devel@...ts.xenproject.org (moderated list:XEN NETWORK BACKEND
        DRIVER),
        netdev@...r.kernel.org (open list:XEN NETWORK BACKEND DRIVER)
Subject: [PATCH v2 1/2] Revert "xen-netback: remove 'hotplug-status' once it has served its purpose"

This reverts commit 1f2565780e9b7218cf92c7630130e82dcc0fe9c2.

The 'hotplug-status' node should not be removed as long as the vif
device remains configured. Otherwise the xen-netback would wait for
re-running the network script even if it was already called (in case of
the frontent re-connecting). But also, it _should_ be removed when the
vif device is destroyed (for example when unbinding the driver) -
otherwise hotplug script would not configure the device whenever it
re-appear.

Moving removal of the 'hotplug-status' node was a workaround for nothing
calling network script after xen-netback module is reloaded. But when
vif interface is re-created (on xen-netback unbind/bind for example),
the script should be called, regardless of who does that - currently
this case is not handled by the toolstack, and requires manual
script call. Keeping hotplug-status=connected to skip the call is wrong
and leads to not configured interface.

More discussion at
https://lore.kernel.org/xen-devel/afedd7cb-a291-e773-8b0d-4db9b291fa98@ipxe.org/T/#u

Cc: stable@...r.kernel.org
Signed-off-by: Marek Marczykowski-Górecki <marmarek@...isiblethingslab.com>
---
Cc: Michael Brown <mcb30@...e.org>
Changes in v2:
 - build fix, reported by kernel test robot <lkp@...el.com>

---
 drivers/net/xen-netback/xenbus.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
index d24b7a7993aa..3fad58d22155 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c
@@ -256,6 +256,7 @@ static void backend_disconnect(struct backend_info *be)
 		unsigned int queue_index;

 		xen_unregister_watchers(vif);
+		xenbus_rm(XBT_NIL, be->dev->nodename, "hotplug-status");
 #ifdef CONFIG_DEBUG_FS
 		xenvif_debugfs_delif(vif);
 #endif /* CONFIG_DEBUG_FS */
@@ -675,7 +676,6 @@ static void hotplug_status_changed(struct xenbus_watch *watch,

 		/* Not interested in this watch anymore. */
 		unregister_hotplug_status_watch(be);
-		xenbus_rm(XBT_NIL, be->dev->nodename, "hotplug-status");
 	}
 	kfree(str);
 }
-- 
2.31.1