Re: [libvirt PATCH v2 4/5] nodedev: handle mdevctl errors consistently

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On 6/22/21 9:53 PM, Jonathon Jongsma wrote:
Currently, we have three different types of mdevctl errors:
  1. the command cannot be constructed ecause of unsatisfied
     preconditions
  2. the command cannot be executed due to some error
  3. the command is executed, but returns an error status

These different failures are handled differently. Some cases set an
error and return and error status, and some return a error message but
do not set an error.

This means that the caller has to check both whether the return value is
negative and whether the errmsg parameter is non-NULL before deciding
whether to report the error or not. The situation is further complicated
by the fact that there are occasional instances where mdevctl exits with
an error status but does not print an error message.  This results in
errmsg being an empty string "" (i.e. non-NULL).

Simplify the situation by ensuring that virReportError() is called for
all error conditions rather than returning an error message back to the
calling function.

Signed-off-by: Jonathon Jongsma <jjongsma@xxxxxxxxxx>
---
  src/node_device/node_device_driver.c | 114 +++++++++++++++------------
  1 file changed, 65 insertions(+), 49 deletions(-)

diff --git a/src/node_device/node_device_driver.c b/src/node_device/node_device_driver.c
index eb85cc0439..497db0006a 100644
--- a/src/node_device/node_device_driver.c
+++ b/src/node_device/node_device_driver.c
@@ -746,6 +746,8 @@ nodeDeviceGetMdevctlCommand(virNodeDeviceDef *def,
      case MDEVCTL_CMD_LAST:
      default:
          /* SHOULD NEVER HAPPEN */
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("Unknown Command '%i'"), cmd_type);
          return NULL;
      }
@@ -795,48 +797,62 @@ nodeDeviceGetMdevctlCommand(virNodeDeviceDef *def, static int
-virMdevctlCreate(virNodeDeviceDef *def, char **uuid, char **errmsg)
+virMdevctlCreate(virNodeDeviceDef *def, char **uuid)
  {
      int status;
+    g_autofree char *errmsg = NULL;
      g_autoptr(virCommand) cmd = nodeDeviceGetMdevctlCommand(def,
                                                              MDEVCTL_CMD_CREATE,
                                                              uuid,
-                                                            errmsg);
+                                                            &errmsg);
if (!cmd)
          return -1;
/* an auto-generated uuid is returned via stdout if no uuid is specified in
       * the mdevctl args */
-    if (virCommandRun(cmd, &status) < 0 || status != 0)
+    if (virCommandRun(cmd, &status) < 0)
+        return -1;
+
+    if (status != 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("Unable to start mediated device: %s"),
+                       MDEVCTL_ERROR(errmsg));
          return -1;
+    }
/* remove newline */
      *uuid = g_strstrip(*uuid);
-
      return 0;
  }
static int
-virMdevctlDefine(virNodeDeviceDef *def, char **uuid, char **errmsg)
+virMdevctlDefine(virNodeDeviceDef *def, char **uuid)
  {
      int status;
+    g_autofree char *errmsg = NULL;
      g_autoptr(virCommand) cmd = nodeDeviceGetMdevctlCommand(def,
                                                              MDEVCTL_CMD_DEFINE,
-                                                            uuid, errmsg);
+                                                            uuid, &errmsg);
if (!cmd)
          return -1;
/* an auto-generated uuid is returned via stdout if no uuid is specified in
       * the mdevctl args */
-    if (virCommandRun(cmd, &status) < 0 || status != 0)
+    if (virCommandRun(cmd, &status) < 0)
          return -1;
+ if (status != 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("Unable to define mediated device: %s"),
+                       MDEVCTL_ERROR(errmsg));
+        return -1;
+    }
+
      /* remove newline */
      *uuid = g_strstrip(*uuid);
-
      return 0;
  }
@@ -846,7 +862,6 @@ nodeDeviceCreateXMLMdev(virConnectPtr conn,
                          virNodeDeviceDef *def)
  {
      g_autofree char *uuid = NULL;
-    g_autofree char *errmsg = NULL;
if (!def->parent) {
          virReportError(VIR_ERR_XML_ERROR, "%s",
@@ -854,11 +869,7 @@ nodeDeviceCreateXMLMdev(virConnectPtr conn,
          return NULL;
      }
- if (virMdevctlCreate(def, &uuid, &errmsg) < 0) {
-        if (errmsg)
-            virReportError(VIR_ERR_INTERNAL_ERROR,
-                           _("Unable to start mediated device: %s"),
-                           errmsg);
+    if (virMdevctlCreate(def, &uuid) < 0) {
          return NULL;
      }
@@ -928,55 +939,79 @@ nodeDeviceCreateXML(virConnectPtr conn, static int
-virMdevctlStop(virNodeDeviceDef *def, char **errmsg)
+virMdevctlStop(virNodeDeviceDef *def)
  {
      int status;
      g_autoptr(virCommand) cmd = NULL;
+    g_autofree char *errmsg = NULL;
- cmd = nodeDeviceGetMdevctlCommand(def, MDEVCTL_CMD_STOP, NULL, errmsg);
+    cmd = nodeDeviceGetMdevctlCommand(def, MDEVCTL_CMD_STOP, NULL, &errmsg);
if (!cmd)
          return -1;
- if (virCommandRun(cmd, &status) < 0 || status != 0)
+    if (virCommandRun(cmd, &status) < 0)
          return -1;
+ if (status != 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("Unable to destroy '%s': %s"), def->name,
+                       MDEVCTL_ERROR(errmsg));
+        return -1;
+    }
+
      return 0;
  }
static int
-virMdevctlUndefine(virNodeDeviceDef *def, char **errmsg)
+virMdevctlUndefine(virNodeDeviceDef *def)
  {
      int status;
      g_autoptr(virCommand) cmd = NULL;
+    g_autofree char *errmsg = NULL;
- cmd = nodeDeviceGetMdevctlCommand(def, MDEVCTL_CMD_UNDEFINE, NULL, errmsg);
+    cmd = nodeDeviceGetMdevctlCommand(def, MDEVCTL_CMD_UNDEFINE, NULL, &errmsg);
if (!cmd)
          return -1;
- if (virCommandRun(cmd, &status) < 0 || status != 0)
+    if (virCommandRun(cmd, &status) < 0)
          return -1;
+ if (status != 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("Unable to undefine mediated device: %s"),
+                       MDEVCTL_ERROR(errmsg));
+        return -1;
+    }
+
      return 0;
  }
static int
-virMdevctlStart(virNodeDeviceDef *def, char **errmsg)
+virMdevctlStart(virNodeDeviceDef *def)
  {
      int status;
      g_autoptr(virCommand) cmd = NULL;
+    g_autofree char *errmsg = NULL;
- cmd = nodeDeviceGetMdevctlCommand(def, MDEVCTL_CMD_START, NULL, errmsg);
+    cmd = nodeDeviceGetMdevctlCommand(def, MDEVCTL_CMD_START, NULL, &errmsg);
if (!cmd)
          return -1;
- if (virCommandRun(cmd, &status) < 0 || status != 0)
+    if (virCommandRun(cmd, &status) < 0)
          return -1;
+ if (status != 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("Unable to create mediated device: %s"),
+                       MDEVCTL_ERROR(errmsg));
+        return -1;
+    }
+
      return 0;
  }
@@ -1204,7 +1239,6 @@ nodeDeviceDestroy(virNodeDevicePtr device)
          g_autofree char *vfiogroup =
              virMediatedDeviceGetIOMMUGroupDev(def->caps->data.mdev.uuid);
          VIR_AUTOCLOSE fd = -1;
-        g_autofree char *errmsg = NULL;
if (!vfiogroup)
              goto cleanup;
@@ -1218,13 +1252,9 @@ nodeDeviceDestroy(virNodeDevicePtr device)
              goto cleanup;
          }
- if (virMdevctlStop(def, &errmsg) < 0) {
-            if (errmsg)
-                virReportError(VIR_ERR_INTERNAL_ERROR,
-                               _("Unable to destroy '%s': %s"), def->name,
-                               errmsg);
+        if (virMdevctlStop(def) < 0)
              goto cleanup;
-        }
+
          ret = 0;
      } else {
          virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
@@ -1299,7 +1329,6 @@ nodeDeviceDefineXML(virConnect *conn,
      g_autoptr(virNodeDeviceDef) def = NULL;
      const char *virt_type = NULL;
      g_autofree char *uuid = NULL;
-    g_autofree char *errmsg = NULL;
      g_autofree char *name = NULL;
virCheckFlags(0, NULL);
@@ -1327,10 +1356,7 @@ nodeDeviceDefineXML(virConnect *conn,
          return NULL;
      }
- if (virMdevctlDefine(def, &uuid, &errmsg) < 0) {
-        if (errmsg)
-            virReportError(VIR_ERR_INTERNAL_ERROR,
-                           _("Unable to define mediated device: %s"), errmsg);
+    if (virMdevctlDefine(def, &uuid) < 0) {
          return NULL;
      }
@@ -1385,14 +1411,9 @@ nodeDeviceUndefine(virNodeDevice *device,
      }
if (nodeDeviceHasCapability(def, VIR_NODE_DEV_CAP_MDEV)) {
-        g_autofree char *errmsg = NULL;
-
-        if (virMdevctlUndefine(def, &errmsg) < 0) {
-            virReportError(VIR_ERR_INTERNAL_ERROR,
-                           _("Unable to undefine mediated device: %s"),
-                           MDEVCTL_ERROR(errmsg));
+        if (virMdevctlUndefine(def) < 0)
              goto cleanup;
-        }
+
          ret = 0;
      } else {
          virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
@@ -1432,14 +1453,9 @@ nodeDeviceCreate(virNodeDevice *device,
          goto cleanup;
if (nodeDeviceHasCapability(def, VIR_NODE_DEV_CAP_MDEV)) {
-        g_autofree char *errmsg = NULL;
-
-        if (virMdevctlStart(def, &errmsg) < 0) {
-            virReportError(VIR_ERR_INTERNAL_ERROR,
-                           _("Unable to create mediated device: %s"),
-                           MDEVCTL_ERROR(errmsg));
+        if (virMdevctlStart(def) < 0)
              goto cleanup;
-        }
+
          ret = 0;
      } else {
          virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",


Just wondering... after reading method "create" throwing "start" and method "start" throwing "create"... I created these tables

Method			=> New error message
===============================================================
virMdevctlCreate	=> "Unable to start mediated device: %s"
virMdevctlDefine	=> "Unable to define mediated device: %s"
virMdevctlStop		=> "Unable to destroy '%s': %s"
virMdevctlUndefine	=> "Unable to undefine mediated device: %s"
virMdevctlStart		=> "Unable to create mediated device: %s"


Method		 	=> Old error message
	=> Calls now
===============================================================
nodeDeviceCreateXMLMdev	=> "Unable to start mediated device: %s"
	=> virMdevctlCreate
nodeDeviceDestroy	=> "Unable to destroy '%s': %s"
	=> virMdevctlStop
nodeDeviceDefineXML	=> "Unable to define mediated device: %s"
	=> virMdevctlDefine
nodeDeviceUndefine	=> "Unable to undefine mediated device: %s"
	=> virMdevctlUndefine
nodeDeviceCreate 	=> "Unable to create mediated device: %s"
	=> virMdevctlStart


Overall all messages remain as before... just the "method name" - "error message"-matching is sometimes a bit strange.

Anyway
Reviewed-by: Boris Fiuczynski <fiuczy@xxxxxxxxxxxxx>

--
Mit freundlichen Grüßen/Kind regards
   Boris Fiuczynski

IBM Deutschland Research & Development GmbH
Vorsitzender des Aufsichtsrats: Gregor Pillen
Geschäftsführung: Dirk Wittkopp
Sitz der Gesellschaft: Böblingen
Registergericht: Amtsgericht Stuttgart, HRB 243294





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