[PATCH 05/29] libxl: suspend: Return correct error from callbacks

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

If a suspend callback fails, it has a libxl error code in its hand.
However we must return to libxc the values that libxc expects.  So we
stash the libxl error code in dss->rc and fish it out again after
libxc returns from the suspend call.

While we're here, abolish the now-redundant `ok' variable in
remus_devices_postsuspend_cb.

The overall functional change is that libxl_domain_save now completes
with the correct error code as determined when the underlying failure
happened.  (Usually this is, still, ERROR_FAIL.)

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
v2: Add cleanup in remus_devices_postsuspend_cb.
---
 tools/libxl/libxl_dom.c      |   22 ++++++++++++++++------
 tools/libxl/libxl_internal.h |    1 +
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index 9971cdc..90877d6 100644
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -1041,6 +1041,7 @@ static void domain_suspend_switch_qemu_xen_logdirty
         libxl__xc_domain_saverestore_async_callback_done(egc, shs, 0);
     } else {
         LOG(ERROR,"logdirty switch failed (rc=%d), aborting suspend",rc);
+        dss->rc = rc;
         libxl__xc_domain_saverestore_async_callback_done(egc, shs, -1);
     }
 }
@@ -1063,6 +1064,7 @@ void libxl__domain_suspend_common_switch_qemu_logdirty
     default:
         LOG(ERROR,"logdirty switch failed"
             ", no valid device model version found, aborting suspend");
+        dss->rc = ERROR_FAIL;
         libxl__xc_domain_saverestore_async_callback_done(egc, shs, -1);
     }
 }
@@ -1144,6 +1146,7 @@ static void switch_logdirty_done(libxl__egc *egc,
     int broke;
     if (rc) {
         broke = -1;
+        dss->rc = rc;
     } else {
         broke = 0;
     }
@@ -1587,6 +1590,7 @@ static void libxl__domain_suspend_callback(void *data)
 static void domain_suspend_callback_common_done(libxl__egc *egc,
                                 libxl__domain_suspend_state *dss, int rc)
 {
+    dss->rc = rc;
     libxl__xc_domain_saverestore_async_callback_done(egc, &dss->shs, !rc);
 }
 
@@ -1622,6 +1626,7 @@ static void remus_domain_suspend_callback_common_done(libxl__egc *egc,
     return;
 
 out:
+    dss->rc = rc;
     libxl__xc_domain_saverestore_async_callback_done(egc, &dss->shs, !rc);
 }
 
@@ -1629,16 +1634,17 @@ static void remus_devices_postsuspend_cb(libxl__egc *egc,
                                          libxl__remus_devices_state *rds,
                                          int rc)
 {
-    int ok = 0;
     libxl__domain_suspend_state *dss = CONTAINER_OF(rds, *dss, rds);
 
     if (rc)
         goto out;
 
-    ok = 1;
+    rc = 0;
 
 out:
-    libxl__xc_domain_saverestore_async_callback_done(egc, &dss->shs, ok);
+    if (rc)
+        dss->rc = rc;
+    libxl__xc_domain_saverestore_async_callback_done(egc, &dss->shs, !rc);
 }
 
 static void libxl__remus_domain_resume_callback(void *data)
@@ -1657,7 +1663,6 @@ static void remus_devices_preresume_cb(libxl__egc *egc,
                                        libxl__remus_devices_state *rds,
                                        int rc)
 {
-    int ok = 0;
     libxl__domain_suspend_state *dss = CONTAINER_OF(rds, *dss, rds);
     STATE_AO_GC(dss->ao);
 
@@ -1669,10 +1674,12 @@ static void remus_devices_preresume_cb(libxl__egc *egc,
     if (rc)
         goto out;
 
-    ok = 1;
+    rc = 0;
 
 out:
-    libxl__xc_domain_saverestore_async_callback_done(egc, &dss->shs, ok);
+    if (rc)
+        dss->rc = rc;
+    libxl__xc_domain_saverestore_async_callback_done(egc, &dss->shs, !rc);
 }
 
 /*----- remus asynchronous checkpoint callback -----*/
@@ -1790,6 +1797,7 @@ void libxl__domain_suspend(libxl__egc *egc, libxl__domain_suspend_state *dss)
     libxl__srm_save_autogen_callbacks *const callbacks =
         &dss->shs.callbacks.save.a;
 
+    dss->rc = 0;
     logdirty_init(&dss->logdirty);
     libxl__xswait_init(&dss->pvcontrol);
     libxl__ev_evtchn_init(&dss->guest_evtchn);
@@ -1877,6 +1885,8 @@ void libxl__xc_domain_save_done(libxl__egc *egc, void *dss_void,
                          "domain did not respond to suspend request");
         if ( !dss->guest_responded )
             rc = ERROR_GUEST_TIMEDOUT;
+        else if (dss->rc)
+            rc = dss->rc;
         else
             rc = ERROR_FAIL;
         goto out;
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 99db92a..2862c69 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -2800,6 +2800,7 @@ struct libxl__domain_suspend_state {
     int debug;
     const libxl_domain_remus_info *remus;
     /* private */
+    int rc;
     libxl__ev_evtchn guest_evtchn;
     int guest_evtchn_lockfd;
     int hvm;
-- 
1.7.10.4