qemu: monitor: Extract 'write-threshold' automatically for -blockdev

In cases when -blockdev is used we need to use 'query-named-block-nodes'
instead of 'query-block'. This means that we can extract the
write-threshold variable right away.

To keep compatibility with old VMs modify the code which was extracting
the value previously so that it updates the stats structure and a single
code path then can be used to extract the data.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

src/qemu/qemu_driver.c

@@ -20027,29 +20027,39 @@ qemuDomainGetStatsOneBlockFallback(virQEMUDriverPtr driver,
 }
 
 
-static int
+/**
-qemuDomainGetStatsOneBlockNode(virDomainStatsRecordPtr record,
+ * qemuDomainGetStatsOneBlockRefreshNamed:
-                               int *maxparams,
+ * @src: disk source structure
-                               virStorageSourcePtr src,
+ * @alias: disk alias
-                               size_t block_idx,
+ * @stats: hash table containing stats for all disks
-                               virHashTablePtr nodedata)
+ * @nodedata: reply containing 'query-named-block-nodes' data
+ *
+ * Refresh disk block stats data (qemuBlockStatsPtr) which are present only
+ * in the reply of 'query-named-block-nodes' in cases when the data was gathered
+ * by using query-block originally.
+ */
+static void
+qemuDomainGetStatsOneBlockRefreshNamed(virStorageSourcePtr src,
+                                       const char *alias,
+                                       virHashTablePtr stats,
+                                       virHashTablePtr nodedata)
 {
+    qemuBlockStatsPtr entry;
+
     virJSONValuePtr data;
     unsigned long long tmp;
-    int ret = -1;
 
-    if (src->nodestorage &&
+    if (!nodedata || !src->nodestorage)
-        (data = virHashLookup(nodedata, src->nodestorage))) {
+        return;
-        if (virJSONValueObjectGetNumberUlong(data, "write_threshold", &tmp) == 0 &&
-            tmp > 0)
-            QEMU_ADD_BLOCK_PARAM_ULL(record, maxparams, block_idx,
-                                     "threshold", tmp);
-    }
 
-    ret = 0;
+    if (!(entry = virHashLookup(stats, alias)))
+        return;
 
- cleanup:
+    if (!(data = virHashLookup(nodedata, src->nodestorage)))
-    return ret;
+        return;
+
+    if (virJSONValueObjectGetNumberUlong(data, "write_threshold", &tmp) == 0)
+        entry->write_threshold = tmp;
 }
 
 
@@ -20063,8 +20073,7 @@ qemuDomainGetStatsOneBlock(virQEMUDriverPtr driver,
                            const char *entryname,
                            virStorageSourcePtr src,
                            size_t block_idx,
-                           virHashTablePtr stats,
+                           virHashTablePtr stats)
-                           virHashTablePtr nodedata)
 {
     qemuBlockStats *entry;
     int ret = -1;
@@ -20129,9 +20138,9 @@ qemuDomainGetStatsOneBlock(virQEMUDriverPtr driver,
         }
     }
 
-    if (qemuDomainGetStatsOneBlockNode(record, maxparams, src, block_idx,
+    if (entry->write_threshold)
-                                       nodedata) < 0)
+        QEMU_ADD_BLOCK_PARAM_ULL(record, maxparams, block_idx, "threshold",
-        goto cleanup;
+                                 entry->write_threshold);
 
     ret = 0;
  cleanup:
@@ -20202,9 +20211,11 @@ qemuDomainGetStatsBlock(virQEMUDriverPtr driver,
                 !(alias = qemuDomainStorageAlias(disk->info.alias, src->id)))
                 goto cleanup;
 
+            qemuDomainGetStatsOneBlockRefreshNamed(src, alias, stats, nodestats);
+
             if (qemuDomainGetStatsOneBlock(driver, cfg, dom, record, maxparams,
                                            disk->dst, alias, src, visited,
-                                           stats, nodestats) < 0)
+                                           stats) < 0)
                 goto cleanup;
 
             VIR_FREE(alias);

src/qemu/qemu_monitor.h

@@ -587,6 +587,9 @@ struct _qemuBlockStats {
      * if wr_highest_offset_valid is true */
     unsigned long long wr_highest_offset;
     bool wr_highest_offset_valid;
+
+    /* write_threshold is valid only if it's non-zero, conforming to qemu semantics */
+    unsigned long long write_threshold;
 };
 
 int qemuMonitorGetAllBlockStatsInfo(qemuMonitorPtr mon,

src/qemu/qemu_monitor_json.c

@@ -2492,7 +2492,8 @@ qemuMonitorJSONGetAllBlockStatsInfo(qemuMonitorPtr mon,
 static int
 qemuMonitorJSONBlockStatsUpdateCapacityData(virJSONValuePtr image,
                                             const char *name,
-                                            virHashTablePtr stats)
+                                            virHashTablePtr stats,
+                                            qemuBlockStatsPtr *entry)
 {
     qemuBlockStatsPtr bstats;
 
@@ -2506,6 +2507,9 @@ qemuMonitorJSONBlockStatsUpdateCapacityData(virJSONValuePtr image,
         }
     }
 
+    if (entry)
+        *entry = bstats;
+
     /* failures can be ignored after this point */
     if (virJSONValueObjectGetNumberUlong(image, "virtual-size",
                                          &bstats->capacity) < 0)
@@ -2531,7 +2535,8 @@ qemuMonitorJSONBlockStatsUpdateCapacityOne(virJSONValuePtr image,
     char *entry_name = qemuDomainStorageAlias(dev_name, depth);
     virJSONValuePtr backing;
 
-    if (qemuMonitorJSONBlockStatsUpdateCapacityData(image, entry_name, stats) < 0)
+    if (qemuMonitorJSONBlockStatsUpdateCapacityData(image, entry_name,
+                                                    stats, NULL) < 0)
         goto cleanup;
 
     if (backingChain &&
@@ -2601,6 +2606,7 @@ qemuMonitorJSONBlockStatsUpdateCapacityBlockdevWorker(size_t pos ATTRIBUTE_UNUSE
     virHashTablePtr stats = opaque;
     virJSONValuePtr image;
     const char *nodename;
+    qemuBlockStatsPtr entry;
 
     if (!(nodename = virJSONValueObjectGetString(val, "node-name")) ||
         !(image = virJSONValueObjectGetObject(val, "image"))) {
@@ -2609,9 +2615,13 @@ qemuMonitorJSONBlockStatsUpdateCapacityBlockdevWorker(size_t pos ATTRIBUTE_UNUSE
         return -1;
     }
 
-    if (qemuMonitorJSONBlockStatsUpdateCapacityData(image, nodename, stats) < 0)
+    if (qemuMonitorJSONBlockStatsUpdateCapacityData(image, nodename, stats, &entry) < 0)
         return -1;
 
+    if (entry)
+        ignore_value(virJSONValueObjectGetNumberUlong(val, "write_threshold",
+                                                      &entry->write_threshold));
+
     return 1; /* we don't want to steal the value from the JSON array */
 }