commit 3f9d6e77b0471c844d5050cc71db0863eb4d1b64
author Arun Menon <armenon@redhat.com> Thu Sep 18 20:53:29 2025 +0530
committer Peter Xu <peterx@redhat.com> Fri Oct 03 09:48:02 2025 -0400
tree e6c698c5c3d35344f00113e1331e6e6ff24cd7cd
parent 8b6dad124ba757ba96a3b4456223e53632371bc8

migration: Update qemu_file_get_return_path() docs and remove dead checks

The documentation of qemu_file_get_return_path() states that it can
return NULL on failure. However, a review of the current implementation
reveals that it is guaranteed that it will always succeed and will never
return NULL.

As a result, the NULL checks post calling the function become redundant.
This commit updates the documentation for the function and removes all
NULL checks throughout the migration code.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Arun Menon <armenon@redhat.com>
Tested-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
Link: https://lore.kernel.org/r/20250918-propagate_tpm_error-v14-12-36f11a6fb9d3@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>

migration/colo.c

diff --git a/migration/colo.c b/migration/colo.c
index ad50a3a..db783f6 100644
--- a/migration/colo.c
+++ b/migration/colo.c
@@ -847,10 +847,6 @@
     failover_init_state();
 
     mis->to_src_file = qemu_file_get_return_path(mis->from_src_file);
-    if (!mis->to_src_file) {
-        error_report("COLO incoming thread: Open QEMUFile to_src_file failed");
-        goto out;
-    }
     /*
      * Note: the communication between Primary side and Secondary side
      * should be sequential, we set the fd to unblocked in migration incoming

migration/migration.c

diff --git a/migration/migration.c b/migration/migration.c
index cba2a39..ce17dcc 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -2656,12 +2656,9 @@
     return NULL;
 }
 
-static int open_return_path_on_source(MigrationState *ms)
+static void open_return_path_on_source(MigrationState *ms)
 {
     ms->rp_state.from_dst_file = qemu_file_get_return_path(ms->to_dst_file);
-    if (!ms->rp_state.from_dst_file) {
-        return -1;
-    }
 
     trace_open_return_path_on_source();
 
@@ -2670,8 +2667,6 @@
     ms->rp_state.rp_thread_created = true;
 
     trace_open_return_path_on_source_continue();
-
-    return 0;
 }
 
 /* Return true if error detected, or false otherwise */
@@ -4022,10 +4017,7 @@
      * QEMU uses the return path.
      */
     if (migrate_postcopy_ram() || migrate_return_path()) {
-        if (open_return_path_on_source(s)) {
-            error_setg(&local_err, "Unable to open return-path for postcopy");
-            goto fail;
-        }
+        open_return_path_on_source(s);
     }
 
     /*

migration/qemu-file.c

diff --git a/migration/qemu-file.c b/migration/qemu-file.c
index 0f4280d..0ee0f48 100644
--- a/migration/qemu-file.c
+++ b/migration/qemu-file.c
@@ -125,7 +125,6 @@
 
 /*
  * Result: QEMUFile* for a 'return path' for comms in the opposite direction
- *         NULL if not available
  */
 QEMUFile *qemu_file_get_return_path(QEMUFile *f)
 {

migration/savevm.c

diff --git a/migration/savevm.c b/migration/savevm.c
index c1ae36b..eb2a905 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2588,10 +2588,6 @@
             return 0;
         }
         mis->to_src_file = qemu_file_get_return_path(f);
-        if (!mis->to_src_file) {
-            error_setg(errp, "CMD_OPEN_RETURN_PATH failed");
-            return -1;
-        }
 
         /*
          * Switchover ack is enabled but no device uses it, so send an ACK to