A fix for handling dirty bitmaps stored in qcow2 files. This is not

absolutely necessary for 2.12, but if there is an rc4, it should go in.
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Merge remote-tracking branch 'remotes/maxreitz/tags/pull-block-2018-04-16' into staging

A fix for handling dirty bitmaps stored in qcow2 files.  This is not
absolutely necessary for 2.12, but if there is an rc4, it should go in.

# gpg: Signature made Mon 16 Apr 2018 13:35:08 BST
# gpg:                using RSA key F407DB0061D5CF40
# gpg: Good signature from "Max Reitz <mreitz@redhat.com>"
# Primary key fingerprint: 91BE B60A 30DB 3E88 57D1  1829 F407 DB00 61D5 CF40

* remotes/maxreitz/tags/pull-block-2018-04-16:
  iotests: fix 169
  qcow2: try load bitmaps only once

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

block/qcow2.c

@@ -1142,6 +1142,7 @@ static int coroutine_fn qcow2_do_open(BlockDriverState *bs, QDict *options,
     uint64_t ext_end;
     uint64_t l1_vm_state_index;
     bool update_header = false;
+    bool header_updated = false;
 
     ret = bdrv_pread(bs->file, 0, &header, sizeof(header));
     if (ret < 0) {
@@ -1480,10 +1481,9 @@ static int coroutine_fn qcow2_do_open(BlockDriverState *bs, QDict *options,
         s->autoclear_features &= QCOW2_AUTOCLEAR_MASK;
     }
 
-    if (bdrv_dirty_bitmap_next(bs, NULL)) {
+    if (s->dirty_bitmaps_loaded) {
-        /* It's some kind of reopen with already existing dirty bitmaps. There
+        /* It's some kind of reopen. There are no known cases where we need to
-         * are no known cases where we need loading bitmaps in such situation,
+         * reload bitmaps in such a situation, so it's safer to skip them.
-         * so it's safer don't load them.
          *
          * Moreover, if we have some readonly bitmaps and we are reopening for
          * rw we should reopen bitmaps correspondingly.
@@ -1491,13 +1491,13 @@ static int coroutine_fn qcow2_do_open(BlockDriverState *bs, QDict *options,
         if (bdrv_has_readonly_bitmaps(bs) &&
             !bdrv_is_read_only(bs) && !(bdrv_get_flags(bs) & BDRV_O_INACTIVE))
         {
-            bool header_updated = false;
             qcow2_reopen_bitmaps_rw_hint(bs, &header_updated, &local_err);
-            update_header = update_header && !header_updated;
         }
-    } else if (qcow2_load_dirty_bitmaps(bs, &local_err)) {
+    } else {
-        update_header = false;
+        header_updated = qcow2_load_dirty_bitmaps(bs, &local_err);
+        s->dirty_bitmaps_loaded = true;
     }
+    update_header = update_header && !header_updated;
     if (local_err != NULL) {
         error_propagate(errp, local_err);
         ret = -EINVAL;

block/qcow2.h

@@ -298,6 +298,7 @@ typedef struct BDRVQcow2State {
     uint32_t nb_bitmaps;
     uint64_t bitmap_directory_size;
     uint64_t bitmap_directory_offset;
+    bool dirty_bitmaps_loaded;
 
     int flags;
     int qcow_version;

tests/qemu-iotests/169

@@ -31,6 +31,8 @@ disk_a = os.path.join(iotests.test_dir, 'disk_a')
 disk_b = os.path.join(iotests.test_dir, 'disk_b')
 size = '1M'
 mig_file = os.path.join(iotests.test_dir, 'mig_file')
+mig_cmd = 'exec: cat > ' + mig_file
+incoming_cmd = 'exec: cat ' + mig_file
 
 
 class TestDirtyBitmapMigration(iotests.QMPTestCase):
@@ -49,7 +51,6 @@ class TestDirtyBitmapMigration(iotests.QMPTestCase):
         self.vm_a.launch()
 
         self.vm_b = iotests.VM(path_suffix='b')
-        self.vm_b.add_incoming("exec: cat '" + mig_file + "'")
 
     def add_bitmap(self, vm, granularity, persistent):
         params = {'node': 'drive0',
@@ -86,36 +87,30 @@ class TestDirtyBitmapMigration(iotests.QMPTestCase):
                    (0xa0201, 0x1000))
 
         should_migrate = migrate_bitmaps or persistent and shared_storage
+        mig_caps = [{'capability': 'events', 'state': True}]
+        if migrate_bitmaps:
+            mig_caps.append({'capability': 'dirty-bitmaps', 'state': True})
 
+        result = self.vm_a.qmp('migrate-set-capabilities',
+                               capabilities=mig_caps)
+        self.assert_qmp(result, 'return', {})
+
+        self.vm_b.add_incoming(incoming_cmd if online else "defer")
         self.vm_b.add_drive(disk_a if shared_storage else disk_b)
 
         if online:
             os.mkfifo(mig_file)
             self.vm_b.launch()
+            result = self.vm_b.qmp('migrate-set-capabilities',
+                                   capabilities=mig_caps)
+            self.assert_qmp(result, 'return', {})
 
         self.add_bitmap(self.vm_a, granularity, persistent)
         for r in regions:
             self.vm_a.hmp_qemu_io('drive0', 'write %d %d' % r)
         sha256 = self.get_bitmap_hash(self.vm_a)
 
-        if migrate_bitmaps:
+        result = self.vm_a.qmp('migrate', uri=mig_cmd)
-            capabilities = [{'capability': 'dirty-bitmaps', 'state': True}]
-
-            result = self.vm_a.qmp('migrate-set-capabilities',
-                                   capabilities=capabilities)
-            self.assert_qmp(result, 'return', {})
-
-            if online:
-                result = self.vm_b.qmp('migrate-set-capabilities',
-                                       capabilities=capabilities)
-                self.assert_qmp(result, 'return', {})
-
-        result = self.vm_a.qmp('migrate-set-capabilities',
-                               capabilities=[{'capability': 'events',
-                                              'state': True}])
-        self.assert_qmp(result, 'return', {})
-
-        result = self.vm_a.qmp('migrate', uri='exec:cat>' + mig_file)
         while True:
             event = self.vm_a.event_wait('MIGRATION')
             if event['data']['status'] == 'completed':
@@ -124,14 +119,25 @@ class TestDirtyBitmapMigration(iotests.QMPTestCase):
         if not online:
             self.vm_a.shutdown()
             self.vm_b.launch()
-            # TODO enable bitmap capability for vm_b in this case
+            result = self.vm_b.qmp('migrate-set-capabilities',
+                                   capabilities=mig_caps)
+            self.assert_qmp(result, 'return', {})
+            result = self.vm_b.qmp('migrate-incoming', uri=incoming_cmd)
+            self.assert_qmp(result, 'return', {})
 
-        self.vm_b.event_wait("RESUME", timeout=10.0)
+        while True:
+            event = self.vm_b.event_wait('MIGRATION')
+            if event['data']['status'] == 'completed':
+                break
 
         self.check_bitmap(self.vm_b, sha256 if should_migrate else False)
 
         if should_migrate:
             self.vm_b.shutdown()
+            # recreate vm_b, as we don't want -incoming option (this will lead
+            # to "cat" process left alive after test finish)
+            self.vm_b = iotests.VM(path_suffix='b')
+            self.vm_b.add_drive(disk_a if shared_storage else disk_b)
             self.vm_b.launch()
             self.check_bitmap(self.vm_b, sha256 if persistent else False)