With the "never" sync policy, we actually can utilize readonly bitmaps
now. Loosen the check at the QMP level, and tighten it based on
provided arguments down at the job creation level instead.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190709232550.10724-19-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>
---
 block/backup.c | 6 ++++++
 blockdev.c     | 2 +-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/block/backup.c b/block/backup.c
index 2be570c0bfd..f8309be01b3 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -617,6 +617,12 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
             return NULL;
         }
 
+        /* If we need to write to this bitmap, check that we can: */
+        if (bitmap_mode != BITMAP_SYNC_MODE_NEVER &&
+            bdrv_dirty_bitmap_check(sync_bitmap, BDRV_BITMAP_DEFAULT, errp)) {
+            return NULL;
+        }
+
         /* Create a new bitmap, and freeze/disable this one. */
         if (bdrv_dirty_bitmap_create_successor(bs, sync_bitmap, errp) < 0) {
             return NULL;
diff --git a/blockdev.c b/blockdev.c
index 985b6cd75c0..a44ab1f709e 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -3491,7 +3491,7 @@ static BlockJob *do_backup_common(BackupCommon *backup,
                        "when providing a bitmap");
             return NULL;
         }
-        if (bdrv_dirty_bitmap_check(bmap, BDRV_BITMAP_DEFAULT, errp)) {
+        if (bdrv_dirty_bitmap_check(bmap, BDRV_BITMAP_ALLOW_RO, errp)) {
             return NULL;
         }
     }
-- 
2.21.0