From 1669a71fd8a4bd570f09fc2df67279d6936cc5ad Mon Sep 17 00:00:00 2001

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Date: Fri, 22 Jun 2018 19:00:03 +0200

Subject: [PATCH 15/21] migration: Don't activate block devices if using -S

RH-Author: Dr. David Alan Gilbert <dgilbert@redhat.com>

Message-id: <20180801135522.11658-17-dgilbert@redhat.com>

Patchwork-id: 81576

O-Subject: [qemu-kvm RHEL8/virt212 PATCH 16/18] migration: Don't activate block devices if using -S

Bugzilla: 1594384

RH-Acked-by: Peter Xu <peterx@redhat.com>

RH-Acked-by: John Snow <jsnow@redhat.com>

RH-Acked-by: Juan Quintela <quintela@redhat.com>

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Activating the block devices causes the locks to be taken on

the backing file.  If we're running with -S and the destination libvirt

hasn't started the destination with 'cont', it's expecting the locks are

still untaken.

Don't activate the block devices if we're not going to autostart the VM;

'cont' already will do that anyway.   This change is tied to the new

migration capability 'late-block-activate' that defaults to off, keeping

the old behaviour by default.

bz: https://bugzilla.redhat.com/show_bug.cgi?id=1560854

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

Signed-off-by: Juan Quintela <quintela@redhat.com>

(cherry picked from commit 0f073f44df109ea0910d67caede70dec95956ff6)

---

 migration/migration.c | 34 +++++++++++++++++++++++++++-------

 qapi/migration.json   |  5 ++++-

 2 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c

index b6294f6..edf1c06 100644

--- a/migration/migration.c

+++ b/migration/migration.c

@@ -199,6 +199,16 @@ static void migrate_generate_event(int new_state)

     }

 }

+static bool migrate_late_block_activate(void)

+{

+    MigrationState *s;

+

+    s = migrate_get_current();

+

+    return s->enabled_capabilities[

+        MIGRATION_CAPABILITY_LATE_BLOCK_ACTIVATE];

+}

+

 /*

  * Called on -incoming with a defer: uri.

  * The migration can be started later after any parameters have been

@@ -308,13 +318,23 @@ static void process_incoming_migration_bh(void *opaque)

     Error *local_err = NULL;

     MigrationIncomingState *mis = opaque;

-    /* 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);

-        local_err = NULL;

-        autostart = false;

+    /* If capability late_block_activate is set:

+     * Only fire up the block code now if we're going to restart the

+     * VM, else 'cont' will do it.

+     * This causes file locking to happen; so we don't want it to happen

+     * unless we really are starting the VM.

+     */

+    if (!migrate_late_block_activate() ||

+         (autostart && (!global_state_received() ||

+            global_state_get_runstate() == RUN_STATE_RUNNING))) {

+        /* 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);

+            local_err = NULL;

+            autostart = false;

+        }

     }

     /*

diff --git a/qapi/migration.json b/qapi/migration.json

index 9d0bf82..618d2de 100644

--- a/qapi/migration.json

+++ b/qapi/migration.json

@@ -357,13 +357,16 @@

 # @dirty-bitmaps: If enabled, QEMU will migrate named dirty bitmaps.

 #                 (since 2.12)

 #

+# @late-block-activate: If enabled, the destination will not activate block

+#           devices (and thus take locks) immediately at the end of migration.

+#           (since 3.0)

 # Since: 1.2

 ##

 { 'enum': 'MigrationCapability',

   'data': ['xbzrle', 'rdma-pin-all', 'auto-converge', 'zero-blocks',

            'compress', 'events', 'postcopy-ram', 'x-colo', 'release-ram',

            'block', 'return-path', 'pause-before-switchover', 'x-multifd',

-           'dirty-bitmaps' ] }

+           'dirty-bitmaps', 'late-block-activate' ] }

 ##

 # @MigrationCapabilityStatus:

-- 

1.8.3.1