migration: Add direct-io parameter

Add the direct-io migration parameter that tells the migration code to
use O_DIRECT when opening the migration stream file whenever possible.

This is currently only used with the mapped-ram migration that has a
clear window guaranteed to perform aligned writes.

Acked-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>

1 files changed, 11 insertions, 0 deletions

diff --git a/migration/migration-hmp-cmds.c b/migration/migration-hmp-cmds.c
index 9f0e8029e0..7d608d26e1 100644
--- a/migration/migration-hmp-cmds.c
+++ b/migration/migration-hmp-cmds.c
@@ -351,6 +351,13 @@ void hmp_info_migrate_parameters(Monitor *mon, const QDict *qdict)
         monitor_printf(mon, "%s: %s\n",
             MigrationParameter_str(MIGRATION_PARAMETER_MODE),
             qapi_enum_lookup(&MigMode_lookup, params->mode));
+
+        if (params->has_direct_io) {
+            monitor_printf(mon, "%s: %s\n",
+                           MigrationParameter_str(
+                               MIGRATION_PARAMETER_DIRECT_IO),
+                           params->direct_io ? "on" : "off");
+        }
     }
 
     qapi_free_MigrationParameters(params);
@@ -624,6 +631,10 @@ void hmp_migrate_set_parameter(Monitor *mon, const QDict *qdict)
         p->has_mode = true;
         visit_type_MigMode(v, param, &p->mode, &err);
         break;
+    case MIGRATION_PARAMETER_DIRECT_IO:
+        p->has_direct_io = true;
+        visit_type_bool(v, param, &p->direct_io, &err);
+        break;
     default:
         assert(0);
     }