[Libvir] [PATCH] Allow virDomainDefine to overwrite existing inactive domains for xen 3.0.3 userspace installations

[Richard W.M. Jones]

Hugh Brock wrote:
> virDomainDefineXML should overwrite an existing inactive domain config 
> if it finds one; it does this successfully for later (post 3.0.3) xen 
> versions. However on xen 3.0.3 overwriting an existing config would fail 
> with a name conflict. This patch allows the overwrite, removing the 
> prior config from the config hashes.
> 
> If someone more familiar than I with libvirt error handling and style 
> could look at this and tell me if I've done something horribly wrong, 
> I'd appreciate it.
> 
> Signed-off-by: Hugh Brock <hbrock at redhat.com>

Thinking aloud and trying to untangle the various hashes used ...

> Index: src/xm_internal.c
> ===================================================================
> RCS file: /data/cvs/libvirt/src/xm_internal.c,v
> retrieving revision 1.23
> diff -u -r1.23 xm_internal.c
> --- src/xm_internal.c	4 Apr 2007 14:19:49 -0000	1.23
> +++ src/xm_internal.c	1 May 2007 17:23:05 -0000
> @@ -2072,7 +2072,9 @@
>   */
>  virDomainPtr xenXMDomainDefineXML(virConnectPtr conn, const char *xml) {
>      virDomainPtr ret;
> +    virDomainPtr olddomain;
>      char filename[PATH_MAX];
> +    const char * oldfilename;
>      unsigned char uuid[VIR_UUID_BUFLEN];
>      virConfPtr conf = NULL;
>      xenXMConfCachePtr entry = NULL;
> @@ -2103,8 +2105,44 @@
>      }
>  
>      if (virHashLookup(nameConfigMap, value->str)) {
> -        xenXMError(conn, VIR_ERR_INTERNAL_ERROR, "domain with name already exists");
> -        goto error;
> +        /* domain exists, we will overwrite it */
> +
> +        if (!(oldfilename = (char *)virHashLookup(nameConfigMap, value->str))) {
> +            xenXMError(conn, VIR_ERR_INTERNAL_ERROR, "can't retrieve config filename for domain to overwrite");
> +            goto error;
> +        }

So get the filename from the nameConfigMap.  Looks OK, although you 
could have also got the filename from configDir ++ "/" ++ value->str, 
but no matter.

> +        if (!(entry = virHashLookup(configCache, oldfilename))) {
> +            xenXMError(conn, VIR_ERR_INTERNAL_ERROR, "can't retrieve config entry for domain to overwrite");
> +            goto error;
> +        }

Get the xenXMConfCache object from the configCache keyed on filename. 
Looks OK.

Despite the name, configCache isn't literally a cache.  Rather it's a 
list of filename -> config entries for everything under /etc/xen.

> +        if (xenXMConfigGetUUID(entry->conf, "uuid", uuid) < 0) {
> +            xenXMError(conn, VIR_ERR_INTERNAL_ERROR, "uuid config parameter is missing");
> +            goto error;
> +        }

Get the UUID from the config file.

> +        if (!(olddomain = virGetDomain(conn, value->str, uuid)))
> +            goto error;

Get the old domain, given name & UUID.

> +        if (olddomain->id != -1) {
> +            xenXMError(conn, VIR_ERR_INTERNAL_ERROR, "can't overwrite an active domain");
> +            goto error;
> +        }
> +
> +        /* Remove the name -> filename mapping */
> +        if (virHashRemoveEntry(nameConfigMap, value->str, NULL) < 0) {
> +            xenXMError(conn, VIR_ERR_INTERNAL_ERROR, "failed to remove old domain from config map");
> +            goto error;
> +        }

Remove the old mapping in nameConfigMap.

> +        /* Remove the config record itself */
> +        if (virHashRemoveEntry(configCache, oldfilename, xenXMConfigFree) < 0) {
> +            xenXMError(conn, VIR_ERR_INTERNAL_ERROR, "failed to remove old domain from config map");
> +            goto error;
> +        }

Remove the configCache entry.

> +        entry = NULL;
>      }

>      if ((strlen(configDir) + 1 + strlen(value->str) + 1) > PATH_MAX) {

and then drop through to virConfWriteFile which will blindly overwrite 
the file.

Looks A-OK to me!

Rich.

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