migration: Use migrate_has_error() in close_return_path_on_source()

close_return_path_on_source() retrieves the migration error from the
the QEMUFile '->to_dst_file' to know if a shutdown is required. This
shutdown is required to exit the return-path thread.

Avoid relying on '->to_dst_file' and use migrate_has_error() instead.

(using to_dst_file is a heuristic to infer whether
rp_state.from_dst_file might be stuck on a recvmsg(). Using a generic
method for detecting errors is more reliable. We also want to reduce
dependency on QEMUFile::last_error)

Suggested-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
[added some words about the motivation for this patch]
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240226203122.22894-3-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>

diff --git a/migration/migration.c b/migration/migration.c
index 7ba2b60e468240cd275166beee0299ba877df313..bab68bcbef33edc9a78c2f4ebeccee690f4b1786 100644 (file)
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -2429,8 +2429,7 @@ static bool close_return_path_on_source(MigrationState *ms)
      * cause it to unblock if it's stuck waiting for the destination.
      */
     WITH_QEMU_LOCK_GUARD(&ms->qemu_file_lock) {
-        if (ms->to_dst_file && ms->rp_state.from_dst_file &&
-            qemu_file_get_error(ms->to_dst_file)) {
+        if (migrate_has_error(ms) && ms->rp_state.from_dst_file) {
             qemu_file_shutdown(ms->rp_state.from_dst_file);
         }
     }