[Qemu-devel] [RFC PATCH 1/2] block/dirty-bitmaps: add inconsistent bit

[John Snow <jsnow@redhat.com>]

Add an inconsistent bit to dirty-bitmaps that allows us to report a bitmap as
persistent but potentially inconsistent, i.e. if we find bitmaps on a qcow2
that have been marked as "in use".

Signed-off-by: John Snow <jsnow@redhat.com>
---
 block/dirty-bitmap.c         | 19 +++++++++++++++++++
 include/block/dirty-bitmap.h |  2 ++
 qapi/block-core.json         |  9 +++++++--
 3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
index fc390cae94..b1879d7fbd 100644
--- a/block/dirty-bitmap.c
+++ b/block/dirty-bitmap.c
@@ -47,6 +47,9 @@ struct BdrvDirtyBitmap {
                                    and this bitmap must remain unchanged while
                                    this flag is set. */
     bool persistent;            /* bitmap must be saved to owner disk image */
+    bool inconsistent;          /* bitmap is persistent, but not owned by QEMU.
+                                 * It cannot be used at all in any way, except
+                                 * a QMP user can remove or clear it. */
     bool migration;             /* Bitmap is selected for migration, it should
                                    not be stored on the next inactivation
                                    (persistent flag doesn't matter until next
@@ -461,6 +464,8 @@ BlockDirtyInfoList *bdrv_query_dirty_bitmaps(BlockDriverState *bs)
         info->recording = bdrv_dirty_bitmap_recording(bm);
         info->busy = bdrv_dirty_bitmap_busy(bm);
         info->persistent = bm->persistent;
+        info->has_inconsistent = bm->inconsistent;
+        info->inconsistent = bm->inconsistent;
         entry->value = info;
         *plist = entry;
         plist = &entry->next;
@@ -708,6 +713,15 @@ void bdrv_dirty_bitmap_set_persistance(BdrvDirtyBitmap *bitmap, bool persistent)
     qemu_mutex_unlock(bitmap->mutex);
 }
 
+/* Called with BQL taken. */
+void bdrv_dirty_bitmap_set_inconsistent(BdrvDirtyBitmap *bitmap, bool value)
+{
+    qemu_mutex_lock(bitmap->mutex);
+    bitmap->inconsistent = value;
+    bitmap->disabled = value;
+    qemu_mutex_unlock(bitmap->mutex);
+}
+
 /* Called with BQL taken. */
 void bdrv_dirty_bitmap_set_migration(BdrvDirtyBitmap *bitmap, bool migration)
 {
@@ -721,6 +735,11 @@ bool bdrv_dirty_bitmap_get_persistance(BdrvDirtyBitmap *bitmap)
     return bitmap->persistent && !bitmap->migration;
 }
 
+bool bdrv_dirty_bitmap_inconsistent(BdrvDirtyBitmap *bitmap)
+{
+    return bitmap->inconsistent;
+}
+
 bool bdrv_has_changed_persistent_bitmaps(BlockDriverState *bs)
 {
     BdrvDirtyBitmap *bm;
diff --git a/include/block/dirty-bitmap.h b/include/block/dirty-bitmap.h
index ba8477b73f..c0d37702fd 100644
--- a/include/block/dirty-bitmap.h
+++ b/include/block/dirty-bitmap.h
@@ -68,6 +68,7 @@ void bdrv_dirty_bitmap_deserialize_finish(BdrvDirtyBitmap *bitmap);
 void bdrv_dirty_bitmap_set_readonly(BdrvDirtyBitmap *bitmap, bool value);
 void bdrv_dirty_bitmap_set_persistance(BdrvDirtyBitmap *bitmap,
                                        bool persistent);
+void bdrv_dirty_bitmap_set_inconsistent(BdrvDirtyBitmap *bitmap, bool value);
 void bdrv_dirty_bitmap_set_busy(BdrvDirtyBitmap *bitmap, bool busy);
 void bdrv_merge_dirty_bitmap(BdrvDirtyBitmap *dest, const BdrvDirtyBitmap *src,
                              HBitmap **backup, Error **errp);
@@ -91,6 +92,7 @@ bool bdrv_dirty_bitmap_readonly(const BdrvDirtyBitmap *bitmap);
 bool bdrv_has_readonly_bitmaps(BlockDriverState *bs);
 bool bdrv_dirty_bitmap_get_autoload(const BdrvDirtyBitmap *bitmap);
 bool bdrv_dirty_bitmap_get_persistance(BdrvDirtyBitmap *bitmap);
+bool bdrv_dirty_bitmap_inconsistent(BdrvDirtyBitmap *bitmap);
 bool bdrv_dirty_bitmap_busy(BdrvDirtyBitmap *bitmap);
 bool bdrv_has_changed_persistent_bitmaps(BlockDriverState *bs);
 BdrvDirtyBitmap *bdrv_dirty_bitmap_next(BlockDriverState *bs,
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 5d1d182447..f6b6dc2aff 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -470,12 +470,17 @@
 # @persistent: true if the bitmap will eventually be flushed to persistent
 #              storage (since 4.0)
 #
+# @inconsistent: true if this is a persistent bitmap that QEMU does not own.
+#                Implies @recording to be false and @busy to be true. To
+#                reclaim ownership, see @block-dirty-bitmap-remove or
+#                @block-dirty-bitmap-clear (since 4.0)
+#
 # Since: 1.3
 ##
 { 'struct': 'BlockDirtyInfo',
   'data': {'*name': 'str', 'count': 'int', 'granularity': 'uint32',
-           'recording': 'bool', 'busy': 'bool',
-           'status': 'DirtyBitmapStatus', 'persistent': 'bool' } }
+           'recording': 'bool', 'busy': 'bool', 'status': 'DirtyBitmapStatus',
+           'persistent': 'bool', '*inconsistent': 'bool' } }
 
 ##
 # @Qcow2BitmapInfoFlags:
-- 
2.17.2