[libvirt] [PATCH] virDomainBlockStats(Flags): Produce saner error message on empty disk path

[Michal Privoznik]

As of 0bd2ccdec an empty disk path for virDomainBlockStats (or the one
with Flags) is allowed meaning "get me overall summarized statistics".
However, running 'virsh domblkstat $dom' throws a misleading error:

  # ./tools/virsh domblkstat dom
  error: Failed to get block stats dom
  error: invalid argument: invalid path:

while after this commit

  # virsh domblkstat dom
  error: Operation not supported: summary statistics are not supported yet

Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
---
 src/qemu/qemu_driver.c | 12 ++++++++++++
 src/test/test_driver.c |  6 ++++++
 2 files changed, 18 insertions(+)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index c9a865e..e04a328 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -9434,6 +9434,12 @@ qemuDomainBlockStats(virDomainPtr dom,
     virDomainDiskDefPtr disk = NULL;
     qemuDomainObjPrivatePtr priv;
 
+    if (!*path) {
+        virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
+                       _("summary statistics are not supported yet"));
+        return ret;
+    }
+
     if (!(vm = qemuDomObjFromDomain(dom)))
         goto cleanup;
 
@@ -9507,6 +9513,12 @@ qemuDomainBlockStatsFlags(virDomainPtr dom,
 
     virCheckFlags(VIR_TYPED_PARAM_STRING_OKAY, -1);
 
+    if (!*path) {
+        virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
+                       _("summary statistics are not supported yet"));
+        return ret;
+    }
+
     /* We don't return strings, and thus trivially support this flag.  */
     flags &= ~VIR_TYPED_PARAM_STRING_OKAY;
 
diff --git a/src/test/test_driver.c b/src/test/test_driver.c
index b724f82..6806ffd 100644
--- a/src/test/test_driver.c
+++ b/src/test/test_driver.c
@@ -3362,6 +3362,12 @@ static int testDomainBlockStats(virDomainPtr domain,
     unsigned long long statbase;
     int ret = -1;
 
+    if (!*path) {
+        virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
+                       _("summary statistics are not supported yet"));
+        return ret;
+    }
+
     testDriverLock(privconn);
     privdom = virDomainObjListFindByName(privconn->domains,
                                          domain->name);
-- 
1.9.0