From 149b5fe290b6d8f52b87993d3d27fe5fca806173 Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Fri, 19 May 2017 09:38:59 +0200
Subject: [PATCH 24/27] migration: Unify block node activation error handling

RH-Author: Kevin Wolf <kwolf@redhat.com>
Message-id: <1495186739-13659-3-git-send-email-kwolf@redhat.com>
Patchwork-id: 75377
O-Subject: [RHEL-7.4 qemu-kvm-rhev PATCH v2 2/2] migration: Unify block node activation error handling
Bugzilla: 1452148
RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
RH-Acked-by: Laurent Vivier <lvivier@redhat.com>
RH-Acked-by: Max Reitz <mreitz@redhat.com>

Migration code activates all block driver nodes on the destination when
the migration completes. It does so by calling
bdrv_invalidate_cache_all() and blk_resume_after_migration(). There is
one code path for precopy and one for postcopy migration, resulting in
four function calls, which used to have three different failure modes.

This patch unifies the behaviour so that failure to activate all block
nodes is non-fatal, but the error message is logged and the VM isn't
automatically started. 'cont' will retry activating the block nodes.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
(cherry picked from commit ace21a58751824f9a3d399e332317233e880de3a)
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 migration/migration.c | 16 +++++-----------
 migration/savevm.c    | 12 +++++-------
 qmp.c                 | 18 +++++++++---------
 3 files changed, 19 insertions(+), 27 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index fdc17bc..7a2ee01 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -340,20 +340,14 @@ static void process_incoming_migration_bh(void *opaque)
     Error *local_err = NULL;
     MigrationIncomingState *mis = opaque;
 
-    /* Make sure all file formats flush their mutable metadata */
+    /* Make sure all file formats flush their mutable metadata.
+     * If we get an error here, just don't restart the VM yet. */
     bdrv_invalidate_cache_all(&local_err);
-    if (local_err) {
-        migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
-                          MIGRATION_STATUS_FAILED);
-        error_report_err(local_err);
-        migrate_decompress_threads_join();
-        exit(EXIT_FAILURE);
+    if (!local_err) {
+        blk_resume_after_migration(&local_err);
     }
-
-    /* If we get an error here, just don't restart the VM yet. */
-    blk_resume_after_migration(&local_err);
     if (local_err) {
-        error_free(local_err);
+        error_report_err(local_err);
         local_err = NULL;
         autostart = false;
     }
diff --git a/migration/savevm.c b/migration/savevm.c
index 21d7985..6e2f9e7 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1620,16 +1620,14 @@ static void loadvm_postcopy_handle_run_bh(void *opaque)
 
     qemu_announce_self();
 
-    /* Make sure all file formats flush their mutable metadata */
+    /* Make sure all file formats flush their mutable metadata.
+     * If we get an error here, just don't restart the VM yet. */
     bdrv_invalidate_cache_all(&local_err);
-    if (local_err) {
-        error_report_err(local_err);
+    if (!local_err) {
+        blk_resume_after_migration(&local_err);
     }
-
-    /* If we get an error here, just don't restart the VM yet. */
-    blk_resume_after_migration(&local_err);
     if (local_err) {
-        error_free(local_err);
+        error_report_err(local_err);
         local_err = NULL;
         autostart = false;
     }
diff --git a/qmp.c b/qmp.c
index a744e44..847b13f 100644
--- a/qmp.c
+++ b/qmp.c
@@ -196,15 +196,15 @@ void qmp_cont(Error **errp)
     }
 
     /* Continuing after completed migration. Images have been inactivated to
-     * allow the destination to take control. Need to get control back now. */
-    if (runstate_check(RUN_STATE_FINISH_MIGRATE) ||
-        runstate_check(RUN_STATE_POSTMIGRATE))
-    {
-        bdrv_invalidate_cache_all(&local_err);
-        if (local_err) {
-            error_propagate(errp, local_err);
-            return;
-        }
+     * allow the destination to take control. Need to get control back now.
+     *
+     * If there are no inactive block nodes (e.g. because the VM was just
+     * paused rather than completing a migration), bdrv_inactivate_all() simply
+     * doesn't do anything. */
+    bdrv_invalidate_cache_all(&local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        return;
     }
 
     blk_resume_after_migration(&local_err);
-- 
1.8.3.1