[PATCH v2 4/4] minios: fix xenbus_rm() calls in frontend drivers

[Matt Wilson <msw@linux.com>]

From: Ben Cressey <bcressey@amazon.com>

The commit "minios: refactor xenbus state machine" caused "/state" to
be appended to the local value of nodename. Previously the nodename
variable pointed to dev->nodename.

The xenbus_rm() calls were not updated to reflect this change, and
refer to paths that do not exist.

For example, shutdown_blkfront() for vbd 2049 would issue these calls:
    xenbus_rm(XBT_NIL, "device/vbd/2049/state/ring-ref");
    xenbus_rm(XBT_NIL, "device/vbd/2049/state/event-channel");

This patch restores the previous behavior, issuing these calls
instead:
    xenbus_rm(XBT_NIL, "device/vbd/2049/ring-ref");
    xenbus_rm(XBT_NIL, "device/vbd/2049/event-channel");

This causes frontend drivers to not be properly reset when PV-GRUB
exists. Some PV Linux drivers fail to re-initialize frontend devices
if PV-GRUB leaves them in this state.

Signed-off-by: Ben Cressey <bcressey@amazon.com>
Reviewed-by: Matt Wilson <msw@amazon.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
[msw: adjusted commit message to include consequences, split out
 changes into separate patches]
Signed-off-by: Matt Wilson <msw@amazon.com>

---
Changes since v1:
- adjusted commit message to include consequences
- split out changes into separate patches
---
 extras/mini-os/blkfront.c |    8 ++++----
 extras/mini-os/fbfront.c  |   28 ++++++++++++++--------------
 extras/mini-os/netfront.c |   16 ++++++++--------
 extras/mini-os/pcifront.c |    8 ++++----
 4 files changed, 30 insertions(+), 30 deletions(-)

diff --git a/extras/mini-os/blkfront.c b/extras/mini-os/blkfront.c
index dd5e95f..ddcf665 100644
--- a/extras/mini-os/blkfront.c
+++ b/extras/mini-os/blkfront.c
@@ -297,10 +297,10 @@ close:
     if (err) free(err);
     xenbus_unwatch_path_token(XBT_NIL, path, path);
 
-    snprintf(path, sizeof(path), "%s/ring-ref", nodename);
-    xenbus_rm(XBT_NIL, path);
-    snprintf(path, sizeof(path), "%s/event-channel", nodename);
-    xenbus_rm(XBT_NIL, path);
+    snprintf(nodename, sizeof(nodename), "%s/ring-ref", dev->nodename);
+    xenbus_rm(XBT_NIL, nodename);
+    snprintf(nodename, sizeof(nodename), "%s/event-channel", dev->nodename);
+    xenbus_rm(XBT_NIL, nodename);
 
     if (!err)
         free_blkfront(dev);
diff --git a/extras/mini-os/fbfront.c b/extras/mini-os/fbfront.c
index 8b4466a..3d0b8f5 100644
--- a/extras/mini-os/fbfront.c
+++ b/extras/mini-os/fbfront.c
@@ -280,12 +280,12 @@ close_kbdfront:
     if (err) free(err);
     xenbus_unwatch_path_token(XBT_NIL, path, path);
 
-    snprintf(path, sizeof(path), "%s/page-ref", nodename);
-    xenbus_rm(XBT_NIL, path);
-    snprintf(path, sizeof(path), "%s/event-channel", nodename);
-    xenbus_rm(XBT_NIL, path);
-    snprintf(path, sizeof(path), "%s/request-abs-pointer", nodename);
-    xenbus_rm(XBT_NIL, path);
+    snprintf(nodename, sizeof(nodename), "%s/page-ref", dev->nodename);
+    xenbus_rm(XBT_NIL, nodename);
+    snprintf(nodename, sizeof(nodename), "%s/event-channel", dev->nodename);
+    xenbus_rm(XBT_NIL, nodename);
+    snprintf(nodename, sizeof(nodename), "%s/request-abs-pointer", dev->nodename);
+    xenbus_rm(XBT_NIL, nodename);
 
     if (!err)
         free_kbdfront(dev);
@@ -671,14 +671,14 @@ close_fbfront:
     if (err) free(err);
     xenbus_unwatch_path_token(XBT_NIL, path, path);
 
-    snprintf(path, sizeof(path), "%s/page-ref", nodename);
-    xenbus_rm(XBT_NIL, path);
-    snprintf(path, sizeof(path), "%s/event-channel", nodename);
-    xenbus_rm(XBT_NIL, path);
-    snprintf(path, sizeof(path), "%s/protocol", nodename);
-    xenbus_rm(XBT_NIL, path);
-    snprintf(path, sizeof(path), "%s/feature-update", nodename);
-    xenbus_rm(XBT_NIL, path);
+    snprintf(nodename, sizeof(nodename), "%s/page-ref", dev->nodename);
+    xenbus_rm(XBT_NIL, nodename);
+    snprintf(nodename, sizeof(nodename), "%s/event-channel", dev->nodename);
+    xenbus_rm(XBT_NIL, nodename);
+    snprintf(nodename, sizeof(nodename), "%s/protocol", dev->nodename);
+    xenbus_rm(XBT_NIL, nodename);
+    snprintf(nodename, sizeof(nodename), "%s/feature-update", dev->nodename);
+    xenbus_rm(XBT_NIL, nodename);
 
     if (!err)
         free_fbfront(dev);
diff --git a/extras/mini-os/netfront.c b/extras/mini-os/netfront.c
index dc29f14..4e087a5 100644
--- a/extras/mini-os/netfront.c
+++ b/extras/mini-os/netfront.c
@@ -549,14 +549,14 @@ close:
     if (err) free(err);
     xenbus_unwatch_path_token(XBT_NIL, path, path);
 
-    snprintf(path, sizeof(path), "%s/tx-ring-ref", nodename);
-    xenbus_rm(XBT_NIL, path);
-    snprintf(path, sizeof(path), "%s/rx-ring-ref", nodename);
-    xenbus_rm(XBT_NIL, path);
-    snprintf(path, sizeof(path), "%s/event-channel", nodename);
-    xenbus_rm(XBT_NIL, path);
-    snprintf(path, sizeof(path), "%s/request-rx-copy", nodename);
-    xenbus_rm(XBT_NIL, path);
+    snprintf(nodename, sizeof(nodename), "%s/tx-ring-ref", dev->nodename);
+    xenbus_rm(XBT_NIL, nodename);
+    snprintf(nodename, sizeof(nodename), "%s/rx-ring-ref", dev->nodename);
+    xenbus_rm(XBT_NIL, nodename);
+    snprintf(nodename, sizeof(nodename), "%s/event-channel", dev->nodename);
+    xenbus_rm(XBT_NIL, nodename);
+    snprintf(nodename, sizeof(nodename), "%s/request-rx-copy", dev->nodename);
+    xenbus_rm(XBT_NIL, nodename);
 
     if (!err)
         free_netfront(dev);
diff --git a/extras/mini-os/pcifront.c b/extras/mini-os/pcifront.c
index df300b5..cdf9c9b 100644
--- a/extras/mini-os/pcifront.c
+++ b/extras/mini-os/pcifront.c
@@ -363,10 +363,10 @@ close_pcifront:
     if (err) free(err);
     xenbus_unwatch_path_token(XBT_NIL, path, path);
 
-    snprintf(path, sizeof(path), "%s/info-ref", nodename);
-    xenbus_rm(XBT_NIL, path);
-    snprintf(path, sizeof(path), "%s/event-channel", nodename);
-    xenbus_rm(XBT_NIL, path);
+    snprintf(nodename, sizeof(nodename), "%s/info-ref", dev->nodename);
+    xenbus_rm(XBT_NIL, nodename);
+    snprintf(nodename, sizeof(nodename), "%s/event-channel", dev->nodename);
+    xenbus_rm(XBT_NIL, nodename);
 
     if (!err)
         free_pcifront(dev);
-- 
1.7.9.5