nbd: Merge nbd_export_bitmap into nbd_export_new

We only have one caller that wants to export a bitmap name,
which it does right after creation of the export. But there is
still a brief window of time where an NBD client could see the
export but not the dirty bitmap, which a robust client would
have to interpret as meaning the entire image should be treated
as dirty.  Better is to eliminate the window entirely, by
inlining nbd_export_bitmap() into nbd_export_new(), and refusing
to create the bitmap in the first place if the requested bitmap
can't be located.

We also no longer need logic for setting a different bitmap
name compared to the bitmap being exported.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20190111194720.15671-8-eblake@redhat.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/qemu-nbd.c b/qemu-nbd.c
index b93fa19..1552274 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -1016,8 +1016,9 @@ int main(int argc, char **argv)
     }
 
     export = nbd_export_new(bs, dev_offset, fd_size, export_name,
-                            export_description, nbdflags, nbd_export_closed,
-                            writethrough, NULL, &error_fatal);
+                            export_description, NULL, nbdflags,
+                            nbd_export_closed, writethrough, NULL,
+                            &error_fatal);
 
     if (device) {
 #if HAVE_NBD_DEVICE