[PATCH 13/29] libxl: domain create: Do not destroy on cancellation

[Ian Jackson <ian.jackson@eu.citrix.com>]

If we cancelled the domain creation, do not try to tear it down again
Document this.

This is a backwards-compatible API change since old libxl users will
never cancel any operations.

In the current code, there is no functional change, because
ERROR_CANCELLED is never generated anywhere yet.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
 tools/libxl/libxl.h        |    4 ++++
 tools/libxl/libxl_create.c |    6 ++++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index c219f59..9385e82 100644
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -914,6 +914,10 @@ int libxl_ctx_free(libxl_ctx *ctx /* 0 is OK */);
 
 /* domain related functions */
 
+/* If the result is ERROR_CANCELLED, the domain may or may not exist
+ * (in a half-created state).  *domid will be valid and will be the
+ * domain id, or -1, as appropriate */
+
 int libxl_domain_create_new(libxl_ctx *ctx, libxl_domain_config *d_config,
                             uint32_t *domid,
                             const libxl_asyncop_how *ao_how,
diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
index 98687bd..f12ed72 100644
--- a/tools/libxl/libxl_create.c
+++ b/tools/libxl/libxl_create.c
@@ -1446,7 +1446,9 @@ static void domcreate_complete(libxl__egc *egc,
     if (!rc && d_config->b_info.exec_ssidref)
         rc = xc_flask_relabel_domain(CTX->xch, dcs->guest_domid, d_config->b_info.exec_ssidref);
 
-    if (!rc) {
+    bool retain_domain = !rc || rc == ERROR_CANCELLED;
+
+    if (retain_domain) {
         libxl__domain_userdata_lock *lock;
 
         /* Note that we hold CTX lock at this point so only need to
@@ -1465,7 +1467,7 @@ static void domcreate_complete(libxl__egc *egc,
 
     libxl_domain_config_dispose(d_config_saved);
 
-    if (rc) {
+    if (!retain_domain) {
         if (dcs->guest_domid) {
             dcs->dds.ao = ao;
             dcs->dds.domid = dcs->guest_domid;
-- 
1.7.10.4