In particular the virt-rescue --scratch option makes it very easy to
add huge numbers of drives. Since the per-backend max_disks limit was
never checked anywhere you could get peculiar failures. Now you'll
get a clear error message:
$ virt-rescue --scratch=256
libguestfs: error: too many drives have been added, the current backend only supports 255
drives
---
lib/launch.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/lib/launch.c b/lib/launch.c
index 7f06c69..37ab024 100644
--- a/lib/launch.c
+++ b/lib/launch.c
@@ -55,12 +55,27 @@ static struct backend {
int
guestfs_impl_launch (guestfs_h *g)
{
+ int r;
+
/* Configured? */
if (g->state != CONFIG) {
error (g, _("the libguestfs handle has already been launched"));
return -1;
}
+ /* Too many drives?
+ *
+ * Some backends such as ‘unix:’ don't allow us to query max_disks.
+ * Don't fail in this case.
+ */
+ guestfs_push_error_handler (g, NULL, NULL);
+ r = guestfs_max_disks (g);
+ guestfs_pop_error_handler (g);
+ if (r >= 0 && g->nr_drives > (size_t) r) {
+ error (g, _("too many drives have been added, the current backend only supports
%d drives"), r);
+ return -1;
+ }
+
/* Start the clock ... */
gettimeofday (&g->launch_t, NULL);
TRACE0 (launch_start);
--
2.9.3