9p/xen: fix init sequence

[ Upstream commit 7ef3ae82a6ebbf4750967d1ce43bcdb7e44ff74b ]

Large amount of mount hangs observed during hotplugging of 9pfs devices. The
9pfs Xen driver attempts to initialize itself more than once, causing the
frontend and backend to disagree: the backend listens on a channel that the
frontend does not send on, resulting in stalled processing.

Only allow initialization of 9p frontend once.

Fixes: c15fe55d14b3b ("9p/xen: fix connection sequence")
Signed-off-by: Alex Zenla <alex@edera.dev>
Signed-off-by: Alexander Merritt <alexander@edera.dev>
Signed-off-by: Ariadne Conill <ariadne@ariadne.space>
Reviewed-by: Juergen Gross <jgross@suse.com>
Message-ID: <20241119211633.38321-1-alexander@edera.dev>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c
index 1fffe2bed5b02f3480b9f074d8b472016708729f..308dae05aa9a1c34da50b12979831fc3a9aed016 100644 (file)
--- a/net/9p/trans_xen.c
+++ b/net/9p/trans_xen.c
@@ -466,6 +466,7 @@ static int xen_9pfs_front_init(struct xenbus_device *dev)
                goto error;
        }
 
+       xenbus_switch_state(dev, XenbusStateInitialised);
        return 0;
 
  error_xenbus:
@@ -513,8 +514,10 @@ static void xen_9pfs_front_changed(struct xenbus_device *dev,
                break;
 
        case XenbusStateInitWait:
-               if (!xen_9pfs_front_init(dev))
-                       xenbus_switch_state(dev, XenbusStateInitialised);
+               if (dev->state != XenbusStateInitialising)
+                       break;
+
+               xen_9pfs_front_init(dev);
                break;
 
        case XenbusStateConnected: