libbe: bail out early if the zfs kmod isn't loaded

As noted in the comment, we already know the rest of libbe_init() will
fail because there's no pool imported.  Avoid the side effect by
checking beforehand and bailing out early.

With this, freebsd-update(8) should no longer trigger a load of the zfs
kmod just because it runs `bectl check`.

Reviewed by:	jwmaag_gmail.com, rew

(cherry picked from commit 2f700ca965a04c4a03b6f760da6a210b6ca4df4b)

1 files changed, 11 insertions, 0 deletions

diff --git a/lib/libbe/be.c b/lib/libbe/be.c
index 13f7a59d5215..471a25e6304c 100644
--- a/lib/libbe/be.c
+++ b/lib/libbe/be.c
@@ -29,6 +29,7 @@
 __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
+#include <sys/module.h>
 #include <sys/mount.h>
 #include <sys/stat.h>
 #include <sys/ucred.h>
@@ -119,6 +120,16 @@ libbe_init(const char *root)
 	lbh = NULL;
 	poolname = pos = NULL;
 
+	/*
+	 * If the zfs kmod's not loaded then the later libzfs_init() will load
+	 * the module for us, but that's not desirable for a couple reasons.  If
+	 * the module's not loaded, there's no pool imported and we're going to
+	 * fail anyways.  We also don't really want libbe consumers to have that
+	 * kind of side-effect (module loading) in the general case.
+	 */
+	if (modfind("zfs") < 0)
+		goto err;
+
 	if ((lbh = calloc(1, sizeof(libbe_handle_t))) == NULL)
 		goto err;