block/dirty-bitmaps: allow clear on disabled bitmaps

Similarly to merge, it's OK to allow clear operations on disabled
bitmaps, as this condition only means that they are not recording
new writes. We are free to clear it if the user requests it.
Signed-off-by: NJohn Snow <jsnow@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20181002230218.13949-4-jsnow@redhat.com
Signed-off-by: NJohn Snow <jsnow@redhat.com>

block/dirty-bitmap.c

@@ -625,7 +625,6 @@ void bdrv_reset_dirty_bitmap(BdrvDirtyBitmap *bitmap,
 
 void bdrv_clear_dirty_bitmap(BdrvDirtyBitmap *bitmap, HBitmap **out)
 {
-    assert(bdrv_dirty_bitmap_enabled(bitmap));
     assert(!bdrv_dirty_bitmap_readonly(bitmap));
     bdrv_dirty_bitmap_lock(bitmap);
     if (!out) {

blockdev.c

@@ -2013,9 +2013,6 @@ static void block_dirty_bitmap_clear_prepare(BlkActionState *common,
     if (bdrv_dirty_bitmap_user_locked(state->bitmap)) {
         error_setg(errp, "Cannot modify a bitmap in use by another operation");
         return;
-    } else if (!bdrv_dirty_bitmap_enabled(state->bitmap)) {
-        error_setg(errp, "Cannot clear a disabled bitmap");
-        return;
     } else if (bdrv_dirty_bitmap_readonly(state->bitmap)) {
         error_setg(errp, "Cannot clear a readonly bitmap");
         return;
@@ -2918,11 +2915,6 @@ void qmp_block_dirty_bitmap_clear(const char *node, const char *name,
                    "Bitmap '%s' is currently in use by another operation"
                    " and cannot be cleared", name);
         return;
-    } else if (!bdrv_dirty_bitmap_enabled(bitmap)) {
-        error_setg(errp,
-                   "Bitmap '%s' is currently disabled and cannot be cleared",
-                   name);
-        return;
     } else if (bdrv_dirty_bitmap_readonly(bitmap)) {
         error_setg(errp, "Bitmap '%s' is readonly and cannot be cleared", name);
         return;