[PATCH v4 08/25] migration: Always report an error in ram_save_setup()

["Cédric Le Goater" <clg@redhat.com>]

This will prepare ground for future changes adding an Error** argument
to the save_setup() handler. We need to make sure that on failure,
ram_save_setup() sets a new error.

Signed-off-by: Cédric Le Goater <clg@redhat.com>
---

 Changes in v4:

 - Fixed test on error returned by qemu_fflush() 
 
 migration/ram.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/migration/ram.c b/migration/ram.c
index 003c28e1336a5fbe7a3877512b8fc3cf62f1bab3..3ac7f52a5f8e2c0d78a8cf150b3fa6611e12ffcc 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -3057,12 +3057,14 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
     int ret, max_hg_page_size;
 
     if (compress_threads_save_setup()) {
+        error_report("%s: failed to start compress threads", __func__);
         return -1;
     }
 
     /* migration has already setup the bitmap, reuse it. */
     if (!migration_in_colo_state()) {
         if (ram_init_all(rsp) != 0) {
+            error_report("%s: failed to setup RAM for migration", __func__);
             compress_threads_save_cleanup();
             return -1;
         }
@@ -3099,12 +3101,14 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
 
     ret = rdma_registration_start(f, RAM_CONTROL_SETUP);
     if (ret < 0) {
+        error_report("%s: failed to start RDMA registration", __func__);
         qemu_file_set_error(f, ret);
         return ret;
     }
 
     ret = rdma_registration_stop(f, RAM_CONTROL_SETUP);
     if (ret < 0) {
+        error_report("%s: failed to stop RDMA registration", __func__);
         qemu_file_set_error(f, ret);
         return ret;
     }
@@ -3116,6 +3120,7 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
     ret = multifd_send_sync_main();
     bql_lock();
     if (ret < 0) {
+        error_report("%s: multifd synchronization failed", __func__);
         return ret;
     }
 
@@ -3125,7 +3130,11 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
     }
 
     qemu_put_be64(f, RAM_SAVE_FLAG_EOS);
-    return qemu_fflush(f);
+    ret = qemu_fflush(f);
+    if (ret < 0) {
+        error_report("%s failed : %s", __func__, strerror(-ret));
+    }
+    return ret;
 }
 
 static void ram_save_file_bmap(QEMUFile *f)
-- 
2.44.0