block/io: turn on dirty_bitmaps for the compressed writes

Previously was added the assert:

  commit 1755da16
  Author: Paolo Bonzini <pbonzini@redhat.com>
  Date:   Thu Oct 18 16:49:18 2012 +0200
  block: introduce new dirty bitmap functionality

Now the compressed write is always in coroutine and setting the bits is
done after the write, so that we can return the dirty_bitmaps for the
compressed writes.
Signed-off-by: NPavel Butsykin <pbutsykin@virtuozzo.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NDenis V. Lunev <den@openvz.org>
CC: Jeff Cody <jcody@redhat.com>
CC: Markus Armbruster <armbru@redhat.com>
CC: Eric Blake <eblake@redhat.com>
CC: John Snow <jsnow@redhat.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/io.c

@@ -896,7 +896,6 @@ bdrv_driver_pwritev_compressed(BlockDriverState *bs, uint64_t offset,
         return -ENOTSUP;
     }
 
-    assert(QLIST_EMPTY(&bs->dirty_bitmaps));
     return drv->bdrv_co_pwritev_compressed(bs, offset, bytes, qiov);
 }
 
@@ -1318,6 +1317,8 @@ static int coroutine_fn bdrv_aligned_pwritev(BlockDriverState *bs,
     } else if (flags & BDRV_REQ_ZERO_WRITE) {
         bdrv_debug_event(bs, BLKDBG_PWRITEV_ZERO);
         ret = bdrv_co_do_pwrite_zeroes(bs, offset, bytes, flags);
+    } else if (flags & BDRV_REQ_WRITE_COMPRESSED) {
+        ret = bdrv_driver_pwritev_compressed(bs, offset, bytes, qiov);
     } else if (bytes <= max_transfer) {
         bdrv_debug_event(bs, BLKDBG_PWRITEV);
         ret = bdrv_driver_pwritev(bs, offset, bytes, qiov, flags);
@@ -1569,14 +1570,9 @@ int coroutine_fn bdrv_co_pwritev(BdrvChild *child,
         bytes = ROUND_UP(bytes, align);
     }
 
-    if (flags & BDRV_REQ_WRITE_COMPRESSED) {
-        ret = bdrv_driver_pwritev_compressed(
-                bs, offset, bytes, use_local_qiov ? &local_qiov : qiov);
-    } else {
-        ret = bdrv_aligned_pwritev(bs, &req, offset, bytes, align,
-                                   use_local_qiov ? &local_qiov : qiov,
-                                   flags);
-    }
+    ret = bdrv_aligned_pwritev(bs, &req, offset, bytes, align,
+                               use_local_qiov ? &local_qiov : qiov,
+                               flags);
 
 fail: