[Qemu-devel] [Qemu-devel [RFC] [WIP] v1] Adding feature to reconnect with -r option to migrate command

[Md Haris Iqbal <haris.phnx@gmail.com>]

---
 hmp-commands.hx               | 10 +++++---
 hmp.c                         |  4 ++-
 include/migration/migration.h |  1 +
 migration/migration.c         | 60 +++++++++++++++++++++++++++++++++----------
 qapi-schema.json              |  2 +-
 qmp-commands.hx               |  3 ++-
 6 files changed, 60 insertions(+), 20 deletions(-)

diff --git a/hmp-commands.hx b/hmp-commands.hx
index 4f4f60a..2e7aed3 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -893,10 +893,11 @@ ETEXI
 
     {
         .name       = "migrate",
-        .args_type  = "detach:-d,blk:-b,inc:-i,uri:s",
-        .params     = "[-d] [-b] [-i] uri",
+        .args_type  = "detach:-d,recover:-r,blk:-b,inc:-i,uri:s",
+        .params     = "[-d] [-r] [-b] [-i] uri",
         .help       = "migrate to URI (using -d to not wait for completion)"
-		      "\n\t\t\t -b for migration without shared storage with"
+		      "\n\t\t\t -r to recover from a broken migration\n\t\t\t"
+              " -b for migration without shared storage with"
 		      " full copy of disk\n\t\t\t -i for migration without "
 		      "shared storage with incremental copy of disk "
 		      "(base image shared between src and destination)",
@@ -905,9 +906,10 @@ ETEXI
 
 
 STEXI
-@item migrate [-d] [-b] [-i] @var{uri}
+@item migrate [-d] [-r] [-b] [-i] @var{uri}
 @findex migrate
 Migrate to @var{uri} (using -d to not wait for completion).
+    -r to recover from a broken migration
 	-b for migration with full copy of disk
 	-i for migration with incremental copy of disk (base image is shared)
 ETEXI
diff --git a/hmp.c b/hmp.c
index d510236..ec8fab4 100644
--- a/hmp.c
+++ b/hmp.c
@@ -1544,12 +1544,14 @@ static void hmp_migrate_status_cb(void *opaque)
 void hmp_migrate(Monitor *mon, const QDict *qdict)
 {
     bool detach = qdict_get_try_bool(qdict, "detach", false);
+    bool recover = qdict_get_try_bool(qdict, "recover", false);
     bool blk = qdict_get_try_bool(qdict, "blk", false);
     bool inc = qdict_get_try_bool(qdict, "inc", false);
     const char *uri = qdict_get_str(qdict, "uri");
     Error *err = NULL;
 
-    qmp_migrate(uri, !!blk, blk, !!inc, inc, false, false, &err);
+    qmp_migrate(uri, !!recover, recover, !!blk, blk, !!inc, inc, false, false,
+                &err);
     if (err) {
         error_report_err(err);
         return;
diff --git a/include/migration/migration.h b/include/migration/migration.h
index ac2c12c..4a3201b 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -139,6 +139,7 @@ struct MigrationState
 
     int state;
     MigrationParams params;
+    bool in_recovery;
 
     /* State related to return path */
     struct {
diff --git a/migration/migration.c b/migration/migration.c
index 991313a..a77f62e 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -933,6 +933,7 @@ MigrationState *migrate_init(const MigrationParams *params)
     s->xfer_limit = 0;
     s->cleanup_bh = 0;
     s->to_dst_file = NULL;
+    s->in_recovery = false;
     s->state = MIGRATION_STATUS_NONE;
     s->params = *params;
     s->rp_state.from_dst_file = NULL;
@@ -992,13 +993,14 @@ void qmp_migrate_incoming(const char *uri, Error **errp)
     once = false;
 }
 
-void qmp_migrate(const char *uri, bool has_blk, bool blk,
-                 bool has_inc, bool inc, bool has_detach, bool detach,
+void qmp_migrate(const char *uri, bool in_recover, bool recover, bool has_blk,
+                 bool blk, bool has_inc, bool inc, bool has_detach, bool detach,
                  Error **errp)
 {
     Error *local_err = NULL;
     MigrationState *s = migrate_get_current();
     MigrationParams params;
+    bool recovery = in_recover && recover;
     const char *p;
 
     params.blk = has_blk && blk;
@@ -1023,7 +1025,31 @@ void qmp_migrate(const char *uri, bool has_blk, bool blk,
         return;
     }
 
-    s = migrate_init(&params);
+    if (recovery ^ atomic_mb_read(&s->in_recovery)) {
+        if (recovery) {
+            /* No VM is waiting for recovery and
+             * recovery option was set
+             */
+
+            error_setg(errp, QERR_UNDEFINED_ERROR);
+            return;
+        } else {
+            /* A VM is waiting for recovery and
+             * no recovery option is set
+             */
+
+            error_setg(errp, QERR_UNDEFINED_ERROR);
+            return;
+        }
+    } else {
+        if (!recovery) {
+            /* No VM is waiting for recovery and
+             * no recovery option is set
+             */
+            fprintf(stderr, "hello1\n");
+            s = migrate_init(&params);
+        }
+    }
 
     if (strstart(uri, "tcp:", &p)) {
         tcp_start_outgoing_migration(s, p, &local_err);
@@ -1767,16 +1793,6 @@ static void *migration_thread(void *opaque)
 
 void migrate_fd_connect(MigrationState *s)
 {
-    /* This is a best 1st approximation. ns to ms */
-    s->expected_downtime = max_downtime/1000000;
-    s->cleanup_bh = qemu_bh_new(migrate_fd_cleanup, s);
-
-    qemu_file_set_rate_limit(s->to_dst_file,
-                             s->bandwidth_limit / XFER_LIMIT_RATIO);
-
-    /* Notify before starting migration thread */
-    notifier_list_notify(&migration_state_notifiers, s);
-
     /*
      * Open the return path; currently for postcopy but other things might
      * also want it.
@@ -1791,6 +1807,24 @@ void migrate_fd_connect(MigrationState *s)
         }
     }
 
+    if (atomic_mb_read(&s->in_recovery)) {
+        atomic_mb_set(&s->in_recovery, 0);
+
+        fprintf(stderr, "recovered\n");
+        return;
+    }
+
+    /* This is a best 1st approximation. ns to ms */
+    s->expected_downtime = max_downtime/1000000;
+    s->cleanup_bh = qemu_bh_new(migrate_fd_cleanup, s);
+
+    qemu_file_set_rate_limit(s->to_dst_file,
+                             s->bandwidth_limit / XFER_LIMIT_RATIO);
+
+    /* Notify before starting migration thread */
+    notifier_list_notify(&migration_state_notifiers, s);
+
+
     migrate_compress_threads_create();
     qemu_thread_create(&s->thread, "migration", migration_thread, s,
                        QEMU_THREAD_JOINABLE);
diff --git a/qapi-schema.json b/qapi-schema.json
index 54634c4..1b7b1e1 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -2070,7 +2070,7 @@
 # Since: 0.14.0
 ##
 { 'command': 'migrate',
-  'data': {'uri': 'str', '*blk': 'bool', '*inc': 'bool', '*detach': 'bool' } }
+  'data': {'uri': 'str', '*recover': 'bool', '*blk': 'bool', '*inc': 'bool', '*detach': 'bool' } }
 
 ##
 # @migrate-incoming
diff --git a/qmp-commands.hx b/qmp-commands.hx
index de896a5..c8a1a93 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -612,7 +612,7 @@ EQMP
 
     {
         .name       = "migrate",
-        .args_type  = "detach:-d,blk:-b,inc:-i,uri:s",
+        .args_type  = "detach:-d,recover:-r,blk:-b,inc:-i,uri:s",
         .mhandler.cmd_new = qmp_marshal_migrate,
     },
 
@@ -625,6 +625,7 @@ Migrate to URI.
 Arguments:
 
 - "blk": block migration, full disk copy (json-bool, optional)
+- "recover": recover migration (json-bool, optional)
 - "inc": incremental disk copy (json-bool, optional)
 - "uri": Destination URI (json-string)
 
-- 
2.7.4