svn commit: r340635 - head/lib/libbe

[Kyle Evans]

Author: kevans
Date: Mon Nov 19 16:47:21 2018
New Revision: 340635
URL: https://svnweb.freebsd.org/changeset/base/340635

Log:
  libbe(3): Handle non-ZFS rootfs better
  
  If rootfs isn't ZFS, current version will emit an error claiming so and fail
  to initialize libbe. As a consumer, bectl -r (undocumented) can be specified
  to operate on a BE independently of whether on a UFS or ZFS root.
  
  Unbreak this for the UFS case by only erroring out the init if we can't
  determine a ZFS dataset for rootfs and no BE root was specified. Consumers
  of libbe should take care to ensure that rootfs is non-empty if they're
  trying to use it, because this could certainly be the case.
  
  Some check is needed before zfs_path_to_zhandle because it will
  unconditionally emit to stderr if the path isn't a ZFS filesystem, which is
  unhelpful for our purposes.
  
  This should also unbreak the bectl(8) tests on a UFS root, as is the case in
  Jenkins' -test runs.
  
  MFC after:	3 days

Modified:
  head/lib/libbe/be.c

Modified: head/lib/libbe/be.c
==============================================================================
--- head/lib/libbe/be.c	Mon Nov 19 16:40:19 2018	(r340634)
+++ head/lib/libbe/be.c	Mon Nov 19 16:47:21 2018	(r340635)
@@ -58,8 +58,22 @@ static int be_create_child_cloned(libbe_handle_t *lbh,
 static int
 be_locate_rootfs(libbe_handle_t *lbh)
 {
+	struct statfs sfs;
+	struct extmnttab entry;
 	zfs_handle_t *zfs;
 
+	/*
+	 * Check first if root is ZFS; if not, we'll bail on rootfs capture.
+	 * Unfortunately needed because zfs_path_to_zhandle will emit to
+	 * stderr if / isn't actually a ZFS filesystem, which we'd like
+	 * to avoid.
+	 */
+	if (statfs("/", &sfs) == 0) {
+		statfs2mnttab(&sfs, &entry);
+		if (strcmp(entry.mnt_fstype, MNTTYPE_ZFS) != 0)
+			return (1);
+	} else
+		return (1);
 	zfs = zfs_path_to_zhandle(lbh->lzh, "/", ZFS_TYPE_FILESYSTEM);
 	if (zfs == NULL)
 		return (1);
@@ -93,8 +107,11 @@ libbe_init(const char *root)
 	 * Grab rootfs, we'll work backwards from there if an optional BE root
 	 * has not been passed in.
 	 */
-	if (be_locate_rootfs(lbh) != 0)
-		goto err;
+	if (be_locate_rootfs(lbh) != 0) {
+		if (root == NULL)
+			goto err;
+		*lbh->rootfs = '\0';
+	}
 	if (root == NULL) {
 		/* Strip off the final slash from rootfs to get the be root */
 		strlcpy(lbh->root, lbh->rootfs, sizeof(lbh->root));