From a37c990a113d5e205d928e629c96d3a82c00d920 Mon Sep 17 00:00:00 2001
From: John Snow <jsnow@redhat.com>
Date: Wed, 18 Jul 2018 22:54:43 +0200
Subject: [PATCH 58/89] dirty-bitmap: fix double lock on bitmap enabling

RH-Author: John Snow <jsnow@redhat.com>
Message-id: <20180718225511.14878-8-jsnow@redhat.com>
Patchwork-id: 81403
O-Subject: [RHEL-7.6 qemu-kvm-rhev PATCH 07/35] dirty-bitmap: fix double lock on bitmap enabling
Bugzilla: 1207657
RH-Acked-by: Eric Blake <eblake@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Fam Zheng <famz@redhat.com>

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Bitmap lock/unlock were added to bdrv_enable_dirty_bitmap in
8b1402ce80d, but some places were not updated correspondingly, which
leads to trying to take this lock twice, which is dead-lock. Fix this.

Actually, iotest 199 (about dirty bitmap postcopy migration) is broken
now, and this fixes it.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20180625165745.25259-3-vsementsov@virtuozzo.com
Signed-off-by: John Snow <jsnow@redhat.com>
(cherry picked from commit 58f72b965e9e1820d246329461216c4d13140122)
Signed-off-by: John Snow <jsnow@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 block/dirty-bitmap.c           | 3 ++-
 migration/block-dirty-bitmap.c | 4 ++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
index 4d6ae8b..f580c1a 100644
--- a/block/dirty-bitmap.c
+++ b/block/dirty-bitmap.c
@@ -259,8 +259,9 @@ void bdrv_enable_dirty_bitmap_locked(BdrvDirtyBitmap *bitmap)
 /* Called with BQL taken. */
 void bdrv_dirty_bitmap_enable_successor(BdrvDirtyBitmap *bitmap)
 {
+    assert(bitmap->mutex == bitmap->successor->mutex);
     qemu_mutex_lock(bitmap->mutex);
-    bdrv_enable_dirty_bitmap(bitmap->successor);
+    bdrv_enable_dirty_bitmap_locked(bitmap->successor);
     qemu_mutex_unlock(bitmap->mutex);
 }
 
diff --git a/migration/block-dirty-bitmap.c b/migration/block-dirty-bitmap.c
index 2c541c9..fefbc6a 100644
--- a/migration/block-dirty-bitmap.c
+++ b/migration/block-dirty-bitmap.c
@@ -511,7 +511,7 @@ void dirty_bitmap_mig_before_vm_start(void)
         DirtyBitmapLoadBitmapState *b = item->data;
 
         if (b->migrated) {
-            bdrv_enable_dirty_bitmap(b->bitmap);
+            bdrv_enable_dirty_bitmap_locked(b->bitmap);
         } else {
             bdrv_dirty_bitmap_enable_successor(b->bitmap);
         }
@@ -547,7 +547,7 @@ static void dirty_bitmap_load_complete(QEMUFile *f, DirtyBitmapLoadState *s)
         if (enabled_bitmaps == NULL) {
             /* in postcopy */
             bdrv_reclaim_dirty_bitmap_locked(s->bs, s->bitmap, &error_abort);
-            bdrv_enable_dirty_bitmap(s->bitmap);
+            bdrv_enable_dirty_bitmap_locked(s->bitmap);
         } else {
             /* target not started, successor must be empty */
             int64_t count = bdrv_get_dirty_count(s->bitmap);
-- 
1.8.3.1