nbd: change error checking order for bitmaps

Check that the bitmap is not in use prior to it checking if it is
not enabled/recording guest writes. The bitmap being busy was likely
at the behest of the user, so this error has a greater chance of being
understood by the user.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20190223000614.13894-6-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>

diff --git a/nbd/server.c b/nbd/server.c
index 8ddfd3e3198d2d6a2b0528892ecb6656d2c6a8f0..6c6cade12b9fe5d6a4a11b92f9ea0e0314308bd1 100644 (file)
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -1510,6 +1510,11 @@ NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset,
             goto fail;
         }
 
+        if (bdrv_dirty_bitmap_user_locked(bm)) {
+            error_setg(errp, "Bitmap '%s' is in use", bitmap);
+            goto fail;
+        }
+
         if ((nbdflags & NBD_FLAG_READ_ONLY) && bdrv_is_writable(bs) &&
             bdrv_dirty_bitmap_enabled(bm)) {
             error_setg(errp,
@@ -1518,11 +1523,6 @@ NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset,
             goto fail;
         }
 
-        if (bdrv_dirty_bitmap_user_locked(bm)) {
-            error_setg(errp, "Bitmap '%s' is in use", bitmap);
-            goto fail;
-        }
-
         bdrv_dirty_bitmap_set_qmp_locked(bm, true);
         exp->export_bitmap = bm;
         exp->export_bitmap_context = g_strdup_printf("qemu:dirty-bitmap:%s",