[virt-tools-list] [vhostmd PATCH 2/3] Optional global sections.

[Michael Trapp]

From: d032747 <michael.trapp at sap.com>

Mark both global sections, disk and virtio, as optional DTD elements.
Based on that, the configured transport can be either 'disk only' or
'virtio only' or 'disk and virtio'.
But a configuration with disabled disk and disabled virtio is not valid.
This condition can't be validated in the DTD and therefore it is checked
in the vhostmd code.

Due to the optional disk transport 'globals/disk/size' must be handled
as optional element.

In addition a disabled disk transport should not result in an empty
disk file. Because the 'initialized' disk file will never get valid
metrics updates, which might be not that obvious for a client in a vm.
---
 vhostmd.dtd       |  2 +-
 vhostmd/vhostmd.c | 19 +++++++++++--------
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/vhostmd.dtd b/vhostmd.dtd
index 888270e..f58a74a 100644
--- a/vhostmd.dtd
+++ b/vhostmd.dtd
@@ -9,7 +9,7 @@ Virtual Host Metrics Daemon (vhostmd). Configuration file DTD
 -->
 
 <!ELEMENT vhostmd (globals,metrics)>
-<!ELEMENT globals (disk,virtio*,update_period,path,transport+)>
+<!ELEMENT globals (disk*,virtio*,update_period,path,transport+)>
 
 <!ELEMENT disk (name,path,size)>
 <!ELEMENT name (#PCDATA)>
diff --git a/vhostmd/vhostmd.c b/vhostmd/vhostmd.c
index 7e29e6f..1dd739e 100644
--- a/vhostmd/vhostmd.c
+++ b/vhostmd/vhostmd.c
@@ -90,7 +90,7 @@ typedef struct _mdisk_header
 
 /* Global variables */
 static int down = 0;
-static int mdisk_size = MDISK_SIZE_MIN;
+static int mdisk_size = MDISK_SIZE_MIN * 256;
 static int update_period = 5;
 static char *def_mdisk_path = "/dev/shm/vhostmd0";
 static char *mdisk_path = NULL;
@@ -586,10 +586,6 @@ static int parse_config_file(const char *filename)
    if (vu_xpath_long("string(./globals/disk/size[1])", ctxt, &l) == 0) {
       mdisk_size = vu_val_by_unit(unit, (int)l);
    }
-   else {
-      vu_log(VHOSTMD_ERR, "Unable to parse metrics disk size");
-      goto out;
-   }
 
    if (vu_xpath_long("string(./globals/update_period[1])", ctxt, &l) == 0) {
       update_period = (int)l;
@@ -616,6 +612,11 @@ static int parse_config_file(const char *filename)
          virtio_expiration_time = (int)l;
    }
 
+   if ((transports & (VIRTIO | VBD)) == 0) {
+      vu_log(VHOSTMD_ERR, "Neither disk nor virtio activated as transport");
+      goto out;
+   }
+
    /* Parse requested metrics definitions */
    if (parse_metrics(xml, ctxt)) {
       vu_log(VHOSTMD_ERR, "Unable to parse metrics definition "
@@ -1136,9 +1137,11 @@ int main(int argc, char *argv[])
       goto out;
    }
 
-   if ((mdisk_fd = metrics_disk_create()) < 0) {
-      vu_log(VHOSTMD_ERR, "Failed to create metrics disk %s", mdisk_path);
-      goto out;
+   if (transports & VBD) {
+      if ((mdisk_fd = metrics_disk_create()) < 0) {
+         vu_log(VHOSTMD_ERR, "Failed to create metrics disk %s", mdisk_path);
+         goto out;
+      }
    }
 
    /* Drop root privileges if requested.  Note: We do this after
-- 
2.24.0