[libvirt] [PATCH] Fix disk stats retrieval with QEMU >= 0.12

[Daniel P. Berrange]

With QEMU >= 0.12 the host and guest side of disks no longer have
the same naming convention. Specifically the host side will now
get a 'drive-' prefix added to its name. The 'info blockstats'
monitor command returns the host side name, so it is neccessary
to strip this off when looking up stats since libvirt stores the
guest side name !

* src/qemu/qemu_conf.c, src/qemu/qemu_conf.h: Move 'drive-' prefix
  string to a defined constant
* src/qemu/qemu_monitor_json.c, src/qemu/qemu_monitor_text.c: Strip
  off 'drive-' prefix (if found) when looking up disk stats
---
 src/qemu/qemu_conf.c         |    4 ++--
 src/qemu/qemu_conf.h         |    2 ++
 src/qemu/qemu_monitor_json.c |    7 +++++++
 src/qemu/qemu_monitor_text.c |    7 +++++++
 4 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/src/qemu/qemu_conf.c b/src/qemu/qemu_conf.c
index 3988582..c1d03cd 100644
--- a/src/qemu/qemu_conf.c
+++ b/src/qemu/qemu_conf.c
@@ -2301,7 +2301,7 @@ qemuBuildDriveStr(virDomainDiskDefPtr disk,
         virBufferAddLit(&opt, ",media=cdrom");
 
     if (qemuCmdFlags & QEMUD_CMD_FLAG_DEVICE) {
-        virBufferVSprintf(&opt, ",id=drive-%s", disk->info.alias);
+        virBufferVSprintf(&opt, ",id=%s%s", QEMU_DRIVE_HOST_PREFIX, disk->info.alias);
     } else {
         if (busid == -1 && unitid == -1) {
             if (idx != -1)
@@ -2390,7 +2390,7 @@ qemuBuildDriveDevStr(virDomainDiskDefPtr disk)
                         _("unsupported disk bus '%s' with device setup"), bus);
         goto error;
     }
-    virBufferVSprintf(&opt, ",drive=drive-%s", disk->info.alias);
+    virBufferVSprintf(&opt, ",drive=%s%s", QEMU_DRIVE_HOST_PREFIX, disk->info.alias);
     virBufferVSprintf(&opt, ",id=%s", disk->info.alias);
 
     if (virBufferError(&opt)) {
diff --git a/src/qemu/qemu_conf.h b/src/qemu/qemu_conf.h
index d26bb90..498f1d1 100644
--- a/src/qemu/qemu_conf.h
+++ b/src/qemu/qemu_conf.h
@@ -157,6 +157,8 @@ typedef qemuDomainPCIAddressSet *qemuDomainPCIAddressSetPtr;
 /* Config type for XML import/export conversions */
 #define QEMU_CONFIG_FORMAT_ARGV "qemu-argv"
 
+#define QEMU_DRIVE_HOST_PREFIX "drive-"
+
 #define qemuReportError(code, fmt...)                                   \
     virReportErrorHelper(NULL, VIR_FROM_QEMU, code, __FILE__,           \
                          __FUNCTION__, __LINE__, fmt)
diff --git a/src/qemu/qemu_monitor_json.c b/src/qemu/qemu_monitor_json.c
index e5288ce..032afef 100644
--- a/src/qemu/qemu_monitor_json.c
+++ b/src/qemu/qemu_monitor_json.c
@@ -754,6 +754,13 @@ int qemuMonitorJSONGetBlockStatsInfo(qemuMonitorPtr mon,
             goto cleanup;
         }
 
+        /* New QEMU has separate names for host & guest side of the disk
+         * and libvirt gives the host side a 'drive-' prefix. The passed
+         * in devname is the guest side though
+         */
+        if (STRPREFIX(thisdev, QEMU_DRIVE_HOST_PREFIX))
+            thisdev += strlen(QEMU_DRIVE_HOST_PREFIX);
+
         if (STRNEQ(thisdev, devname))
             continue;
 
diff --git a/src/qemu/qemu_monitor_text.c b/src/qemu/qemu_monitor_text.c
index 23fc4cf..a6a4598 100644
--- a/src/qemu/qemu_monitor_text.c
+++ b/src/qemu/qemu_monitor_text.c
@@ -649,6 +649,13 @@ int qemuMonitorTextGetBlockStatsInfo(qemuMonitorPtr mon,
     p = info;
 
     while (*p) {
+        /* New QEMU has separate names for host & guest side of the disk
+         * and libvirt gives the host side a 'drive-' prefix. The passed
+         * in devname is the guest side though
+         */
+        if (STRPREFIX(p, QEMU_DRIVE_HOST_PREFIX))
+            p += strlen(QEMU_DRIVE_HOST_PREFIX);
+
         if (STREQLEN (p, devname, devnamelen)
             && p[devnamelen] == ':' && p[devnamelen+1] == ' ') {
 
-- 
1.6.5.2