libxc: Fix xc_tmem_control to return proper error.

The API returns now negative values on error and stashes
the error in errno. Fix the user of this API.

The 'xc_hypercall_bounce_pre' can fail - and if so it will
stash its errno values - no need to over-write it.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

tools/libxc/xc_tmem.c

@@ -73,11 +73,14 @@ int xc_tmem_control(xc_interface *xch,
     if ( subop == TMEMC_LIST && arg1 != 0 )
     {
         if ( buf == NULL )
-            return -EINVAL;
+        {
+            errno = EINVAL;
+            return -1;
+        }
         if ( xc_hypercall_bounce_pre(xch, buf) )
         {
             PERROR("Could not bounce buffer for tmem control hypercall");
-            return -ENOMEM;
+            return -1;
         }
     }
 
@@ -118,11 +121,14 @@ int xc_tmem_control_oid(xc_interface *xch,
     if ( subop == TMEMC_LIST && arg1 != 0 )
     {
         if ( buf == NULL )
-            return -EINVAL;
+        {
+            errno = EINVAL;
+            return -1;
+        }
         if ( xc_hypercall_bounce_pre(xch, buf) )
         {
             PERROR("Could not bounce buffer for tmem control (OID) hypercall");
-            return -ENOMEM;
+            return -1;
         }
     }
 

tools/xenstat/libxenstat/src/xenstat.c

@@ -166,6 +166,7 @@ xenstat_node *xenstat_get_node(xenstat_handle * handle, unsigned int flags)
 	xc_domaininfo_t domaininfo[DOMAIN_CHUNK_SIZE];
 	int new_domains;
 	unsigned int i;
+	int rc;
 
 	/* Create the node */
 	node = (xenstat_node *) calloc(1, sizeof(xenstat_node));
@@ -189,9 +190,9 @@ xenstat_node *xenstat_get_node(xenstat_handle * handle, unsigned int flags)
 	node->free_mem = ((unsigned long long)physinfo.free_pages)
 	    * handle->page_size;
 
-	node->freeable_mb = (long)xc_tmem_control(handle->xc_handle, -1,
-				TMEMC_QUERY_FREEABLE_MB, -1, 0, 0, 0, NULL);
-
+	rc = xc_tmem_control(handle->xc_handle, -1,
+                         TMEMC_QUERY_FREEABLE_MB, -1, 0, 0, 0, NULL);
+	node->freeable_mb = (rc < 0) ? 0 : rc;
 	/* malloc(0) is not portable, so allocate a single domain.  This will
 	 * be resized below. */
 	node->domains = malloc(sizeof(xenstat_domain));