[Qemu-devel] [PATCH RFC v7 6/9] migration: fix the multifd code when receiving less channels

[Fei Li <fli@suse.com>]

In our current code, when multifd is used during migration, if there
is an error before the destination receives all new channels, the
source keeps running, however the destination does not exit but keeps
waiting until the source is killed deliberately.

Fix this by dumping the specific error and let users decide whether
to quit from the destination side when failing to receive packet via
some channel.

Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Fei Li <fli@suse.com>
---
 migration/channel.c   | 11 ++++++-----
 migration/migration.c |  9 +++++++--
 migration/migration.h |  2 +-
 migration/ram.c       |  6 +++++-
 migration/ram.h       |  2 +-
 5 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/migration/channel.c b/migration/channel.c
index 33e0e9b82f..20e4c8e2dc 100644
--- a/migration/channel.c
+++ b/migration/channel.c
@@ -30,6 +30,7 @@
 void migration_channel_process_incoming(QIOChannel *ioc)
 {
     MigrationState *s = migrate_get_current();
+    Error *local_err = NULL;
 
     trace_migration_set_incoming_channel(
         ioc, object_get_typename(OBJECT(ioc)));
@@ -38,13 +39,13 @@ void migration_channel_process_incoming(QIOChannel *ioc)
         *s->parameters.tls_creds &&
         !object_dynamic_cast(OBJECT(ioc),
                              TYPE_QIO_CHANNEL_TLS)) {
-        Error *local_err = NULL;
         migration_tls_channel_process_incoming(s, ioc, &local_err);
-        if (local_err) {
-            error_report_err(local_err);
-        }
     } else {
-        migration_ioc_process_incoming(ioc);
+        migration_ioc_process_incoming(ioc, &local_err);
+    }
+
+    if (local_err) {
+        error_report_err(local_err);
     }
 }
 
diff --git a/migration/migration.c b/migration/migration.c
index 8b36e7f184..87dfc7374f 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -541,7 +541,7 @@ void migration_fd_process_incoming(QEMUFile *f)
     migration_incoming_process();
 }
 
-void migration_ioc_process_incoming(QIOChannel *ioc)
+void migration_ioc_process_incoming(QIOChannel *ioc, Error **errp)
 {
     MigrationIncomingState *mis = migration_incoming_get_current();
     bool start_migration;
@@ -563,9 +563,14 @@ void migration_ioc_process_incoming(QIOChannel *ioc)
          */
         start_migration = !migrate_use_multifd();
     } else {
+        Error *local_err = NULL;
         /* Multiple connections */
         assert(migrate_use_multifd());
-        start_migration = multifd_recv_new_channel(ioc);
+        start_migration = multifd_recv_new_channel(ioc, &local_err);
+        if (local_err) {
+            error_propagate(errp, local_err);
+            return;
+        }
     }
 
     if (start_migration) {
diff --git a/migration/migration.h b/migration/migration.h
index f7813f8261..7df4d426d0 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -229,7 +229,7 @@ struct MigrationState
 void migrate_set_state(int *state, int old_state, int new_state);
 
 void migration_fd_process_incoming(QEMUFile *f);
-void migration_ioc_process_incoming(QIOChannel *ioc);
+void migration_ioc_process_incoming(QIOChannel *ioc, Error **errp);
 void migration_incoming_process(void);
 
 bool  migration_has_all_channels(void);
diff --git a/migration/ram.c b/migration/ram.c
index c84d164fc8..5008a9ab02 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1339,7 +1339,7 @@ bool multifd_recv_all_channels_created(void)
 }
 
 /* Return true if multifd is ready for the migration, otherwise false */
-bool multifd_recv_new_channel(QIOChannel *ioc)
+bool multifd_recv_new_channel(QIOChannel *ioc, Error **errp)
 {
     MultiFDRecvParams *p;
     Error *local_err = NULL;
@@ -1347,6 +1347,9 @@ bool multifd_recv_new_channel(QIOChannel *ioc)
 
     id = multifd_recv_initial_packet(ioc, &local_err);
     if (id < 0) {
+        error_propagate_prepend(errp, local_err,
+                        "failed to receive packet via multifd channel %x: ",
+                        multifd_recv_state->count);
         multifd_recv_terminate_threads(local_err, false);
         return false;
     }
@@ -1356,6 +1359,7 @@ bool multifd_recv_new_channel(QIOChannel *ioc)
         error_setg(&local_err, "multifd: received id '%d' already setup'",
                    id);
         multifd_recv_terminate_threads(local_err, true);
+        error_propagate(errp, local_err);
         return false;
     }
     p->c = ioc;
diff --git a/migration/ram.h b/migration/ram.h
index 83ff1bc11a..046d3074be 100644
--- a/migration/ram.h
+++ b/migration/ram.h
@@ -47,7 +47,7 @@ int multifd_save_cleanup(Error **errp);
 int multifd_load_setup(void);
 int multifd_load_cleanup(Error **errp);
 bool multifd_recv_all_channels_created(void);
-bool multifd_recv_new_channel(QIOChannel *ioc);
+bool multifd_recv_new_channel(QIOChannel *ioc, Error **errp);
 
 uint64_t ram_pagesize_summary(void);
 int ram_save_queue_pages(const char *rbname, ram_addr_t start, ram_addr_t len);
-- 
2.13.7