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Blame SOURCES/kvm-migration-Don-t-activate-block-devices-if-using-S.patch

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From 1669a71fd8a4bd570f09fc2df67279d6936cc5ad Mon Sep 17 00:00:00 2001
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From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
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Date: Fri, 22 Jun 2018 19:00:03 +0200
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Subject: [PATCH 15/21] migration: Don't activate block devices if using -S
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RH-Author: Dr. David Alan Gilbert <dgilbert@redhat.com>
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Message-id: <20180801135522.11658-17-dgilbert@redhat.com>
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Patchwork-id: 81576
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O-Subject: [qemu-kvm RHEL8/virt212 PATCH 16/18] migration: Don't activate block devices if using -S
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Bugzilla: 1594384
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RH-Acked-by: Peter Xu <peterx@redhat.com>
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RH-Acked-by: John Snow <jsnow@redhat.com>
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RH-Acked-by: Juan Quintela <quintela@redhat.com>
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From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
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Activating the block devices causes the locks to be taken on
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the backing file.  If we're running with -S and the destination libvirt
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hasn't started the destination with 'cont', it's expecting the locks are
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still untaken.
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Don't activate the block devices if we're not going to autostart the VM;
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'cont' already will do that anyway.   This change is tied to the new
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migration capability 'late-block-activate' that defaults to off, keeping
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the old behaviour by default.
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bz: https://bugzilla.redhat.com/show_bug.cgi?id=1560854
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Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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Reviewed-by: Juan Quintela <quintela@redhat.com>
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Signed-off-by: Juan Quintela <quintela@redhat.com>
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(cherry picked from commit 0f073f44df109ea0910d67caede70dec95956ff6)
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---
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 migration/migration.c | 34 +++++++++++++++++++++++++++-------
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 qapi/migration.json   |  5 ++++-
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 2 files changed, 31 insertions(+), 8 deletions(-)
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diff --git a/migration/migration.c b/migration/migration.c
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index b6294f6..edf1c06 100644
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--- a/migration/migration.c
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+++ b/migration/migration.c
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@@ -199,6 +199,16 @@ static void migrate_generate_event(int new_state)
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     }
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 }
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+static bool migrate_late_block_activate(void)
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+{
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+    MigrationState *s;
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+
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+    s = migrate_get_current();
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+
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+    return s->enabled_capabilities[
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+        MIGRATION_CAPABILITY_LATE_BLOCK_ACTIVATE];
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+}
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+
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 /*
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  * Called on -incoming with a defer: uri.
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  * The migration can be started later after any parameters have been
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@@ -308,13 +318,23 @@ static void process_incoming_migration_bh(void *opaque)
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     Error *local_err = NULL;
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     MigrationIncomingState *mis = opaque;
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-    /* Make sure all file formats flush their mutable metadata.
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-     * If we get an error here, just don't restart the VM yet. */
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-    bdrv_invalidate_cache_all(&local_err);
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-    if (local_err) {
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-        error_report_err(local_err);
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-        local_err = NULL;
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-        autostart = false;
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+    /* If capability late_block_activate is set:
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+     * Only fire up the block code now if we're going to restart the
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+     * VM, else 'cont' will do it.
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+     * This causes file locking to happen; so we don't want it to happen
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+     * unless we really are starting the VM.
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+     */
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+    if (!migrate_late_block_activate() ||
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+         (autostart && (!global_state_received() ||
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+            global_state_get_runstate() == RUN_STATE_RUNNING))) {
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+        /* Make sure all file formats flush their mutable metadata.
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+         * If we get an error here, just don't restart the VM yet. */
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+        bdrv_invalidate_cache_all(&local_err);
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+        if (local_err) {
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+            error_report_err(local_err);
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+            local_err = NULL;
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+            autostart = false;
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+        }
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     }
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     /*
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diff --git a/qapi/migration.json b/qapi/migration.json
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index 9d0bf82..618d2de 100644
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--- a/qapi/migration.json
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+++ b/qapi/migration.json
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@@ -357,13 +357,16 @@
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 # @dirty-bitmaps: If enabled, QEMU will migrate named dirty bitmaps.
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 #                 (since 2.12)
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 #
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+# @late-block-activate: If enabled, the destination will not activate block
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+#           devices (and thus take locks) immediately at the end of migration.
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+#           (since 3.0)
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 # Since: 1.2
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 ##
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 { 'enum': 'MigrationCapability',
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   'data': ['xbzrle', 'rdma-pin-all', 'auto-converge', 'zero-blocks',
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            'compress', 'events', 'postcopy-ram', 'x-colo', 'release-ram',
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            'block', 'return-path', 'pause-before-switchover', 'x-multifd',
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-           'dirty-bitmaps' ] }
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+           'dirty-bitmaps', 'late-block-activate' ] }
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 ##
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 # @MigrationCapabilityStatus:
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-- 
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1.8.3.1
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