[Xen-changelog] Instead of writing errors to

[Xen patchbot -unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User emellor@xxxxxxxxxxxxxxxxxxxxxx
# Node ID 5a728a884242b7aa2a0ab6d998adbc117b0ef917
# Parent  2c0b3b8077564205640952f8919e39ee05872cfd
Instead of writing errors to
/local/domain/0/backend/<devclass>/<dom>/<devid>/error, write them instead to
/local/domain/0/error/backend/<yada>.  This is not the best place for them
perhaps, but it moves them out of the backend directory, on which the drivers
have a watch.  This fixes the problem whereby writing an error will trigger a
watch, causing the error message to be written again, and repeat.  Fixes bug
#286.
 
Signed-off-by: Ewan Mellor <ewan@xxxxxxxxxxxxx>

diff -r 2c0b3b807756 -r 5a728a884242 
linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_xs.c
--- a/linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_xs.c       Sun Oct 23 
15:54:51 2005
+++ b/linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_xs.c       Sun Oct 23 
21:34:13 2005
@@ -516,17 +516,38 @@
 }
 EXPORT_SYMBOL(xenbus_printf);
 
+/**
+ * Return the path to the error node for the given device, or NULL on failure.
+ * If the value returned is non-NULL, then it is the caller's to kfree.
+ */
+static char *error_path(struct xenbus_device *dev)
+{
+       char *path_buffer = kmalloc(strlen("error/") + strlen(dev->nodename) +
+                                   1, GFP_KERNEL);
+       if (path_buffer == NULL) {
+               return NULL;
+       }
+
+       strcpy(path_buffer, "error/");
+       strcpy(path_buffer + strlen("error/"), dev->nodename);
+
+       return path_buffer;
+}
+
 /* Report a (negative) errno into the store, with explanation. */
 void xenbus_dev_error(struct xenbus_device *dev, int err, const char *fmt, ...)
 {
        va_list ap;
        int ret;
        unsigned int len;
-       char *printf_buffer;
+       char *printf_buffer = NULL, *path_buffer = NULL;
 
        printf_buffer = kmalloc(PRINTF_BUFFER_SIZE, GFP_KERNEL);
-       if (printf_buffer == NULL)
+       if (printf_buffer == NULL) {
+               printk("xenbus: failed to write error node for %s (%d): %d\n",
+                      dev->nodename, err, errno);
                goto fail;
+       }
 
        len = sprintf(printf_buffer, "%i ", -err);
        va_start(ap, fmt);
@@ -535,15 +556,26 @@
 
        BUG_ON(len + ret > PRINTF_BUFFER_SIZE-1);
        dev->has_error = 1;
-       if (xenbus_write(NULL, dev->nodename, "error", printf_buffer) != 0)
+
+       path_buffer = error_path(dev);
+
+       if (path_buffer == NULL) {
+               printk("xenbus: failed to write error node for %s (%s): %d\n",
+                      dev->nodename, printf_buffer, errno);
                goto fail;
-
-       kfree(printf_buffer);
-       return;
-
- fail:
-       printk("xenbus: failed to write error node for %s (%s)\n",
-              dev->nodename, printf_buffer);
+       }
+
+       if (xenbus_write(NULL, path_buffer, "error", printf_buffer) != 0) {
+               printk("xenbus: failed to write error node for %s (%s)\n",
+                      dev->nodename, printf_buffer);
+               goto fail;
+       }
+
+fail:
+       if (printf_buffer)
+               kfree(printf_buffer);
+       if (path_buffer)
+               kfree(path_buffer);
 }
 EXPORT_SYMBOL(xenbus_dev_error);
 
@@ -551,11 +583,21 @@
 void xenbus_dev_ok(struct xenbus_device *dev)
 {
        if (dev->has_error) {
-               if (xenbus_rm(NULL, dev->nodename, "error") != 0)
+               char *path_buffer = error_path(dev);
+
+               if (path_buffer == NULL) {
+                       printk("xenbus: failed to clear error node for %s: "
+                              "%d\n", dev->nodename, errno);
+                       return;
+               }
+
+               if (xenbus_rm(NULL, path_buffer, "error") != 0)
                        printk("xenbus: failed to clear error node for %s\n",
                               dev->nodename);
                else
                        dev->has_error = 0;
+
+               kfree(path_buffer);
        }
 }
 EXPORT_SYMBOL(xenbus_dev_ok);
diff -r 2c0b3b807756 -r 5a728a884242 tools/examples/xen-backend.agent
--- a/tools/examples/xen-backend.agent  Sun Oct 23 15:54:51 2005
+++ b/tools/examples/xen-backend.agent  Sun Oct 23 21:34:13 2005
@@ -15,9 +15,13 @@
       vbd)
        /etc/xen/scripts/block unbind
         ;;
+      vif)
+        [ -n "$script" ] && $script down
+        ;;
     esac
     # remove device backend store entries
     xenstore-rm -t "$XENBUS_PATH"
+    xenstore-rm -t "error/$XENBUS_PATH"
     ;;
   online)
     case "$XENBUS_TYPE" in
diff -r 2c0b3b807756 -r 5a728a884242 tools/python/xen/util/diagnose.py
--- a/tools/python/xen/util/diagnose.py Sun Oct 23 15:54:51 2005
+++ b/tools/python/xen/util/diagnose.py Sun Oct 23 21:34:13 2005
@@ -107,7 +107,9 @@
                 print ("Cannot find backend path for device %s, %s." %
                        (deviceClass, device))
             else:
-                backend_error = xstransact.Read(backendPath, 'error')
+                backend_error = xstransact.Read(
+                    backendPath.replace('backend/', 'error/backend/'),
+                    'error')
 
                 if backend_error:
                     diagnose_device_error(backend_error)

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