Improve handling of filesystem versions

Change mount code to diagnose filesystem versions that
are not supported by the current implementation.

Change upgrade code to do likewise and refuse to upgrade
a pool if any filesystems on it are a version which is
not supported by the current implementation.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Dan Swartzendruber <dswartz@druber.com>
Closes: #2616

cmd/mount_zfs/mount_zfs.c

@@ -363,6 +363,7 @@ main(int argc, char **argv)
 {
 	zfs_handle_t *zhp;
 	char prop[ZFS_MAXPROPLEN];
+	uint64_t zfs_version = 0;
 	char mntopts[MNT_LINE_MAX] = { '\0' };
 	char badopt[MNT_LINE_MAX] = { '\0' };
 	char mtabopt[MNT_LINE_MAX] = { '\0' };
@@ -515,6 +516,18 @@ main(int argc, char **argv)
 		(void) zfs_prop_get(zhp, ZFS_PROP_MOUNTPOINT, prop,
 		    sizeof (prop), NULL, NULL, 0, B_FALSE);
 
+	/*
+	 * Fetch the max supported zfs version in case we get ENOTSUP
+	 * back from the mount command, since we need the zfs handle
+	 * to do so.
+	 */
+	zfs_version = zfs_prop_get_int(zhp, ZFS_PROP_VERSION);
+	if (zfs_version == 0) {
+		fprintf(stderr, gettext("unable to fetch "
+		    "ZFS version for filesystem '%s'\n"), dataset);
+		return (MOUNT_SYSERR);
+	}
+
 	zfs_close(zhp);
 	libzfs_fini(g_zfs);
 
@@ -551,6 +564,8 @@ main(int argc, char **argv)
 	if (!fake) {
 		error = mount(dataset, mntpoint, MNTTYPE_ZFS,
 		    mntflags, mntopts);
+	}
+
 	if (error) {
 		switch (errno) {
 		case ENOENT:
@@ -561,6 +576,19 @@ main(int argc, char **argv)
 			(void) fprintf(stderr, gettext("filesystem "
 			    "'%s' is already mounted\n"), dataset);
 			return (MOUNT_BUSY);
+		case ENOTSUP:
+			if (zfs_version > ZPL_VERSION) {
+				(void) fprintf(stderr,
+				    gettext("filesystem '%s' (v%d) is not "
+				    "supported by this implementation of "
+				    "ZFS (max v%d).\n"), dataset,
+				    (int) zfs_version, (int) ZPL_VERSION);
+			} else {
+				(void) fprintf(stderr,
+				    gettext("filesystem '%s' mount "
+				    "failed for unknown reason.\n"), dataset);
+			}
+			return (MOUNT_SYSERR);
 		default:
 			(void) fprintf(stderr, gettext("filesystem "
 			    "'%s' can not be mounted due to error "
@@ -568,7 +596,6 @@ main(int argc, char **argv)
 			return (MOUNT_USAGE);
 		}
 	}
-	}
 
 	if (!nomtab && mtab_is_writeable()) {
 		error = mtab_update(dataset, mntpoint, MNTTYPE_ZFS, mtabopt);

cmd/zpool/zpool_main.c

@@ -4601,12 +4601,33 @@ typedef struct upgrade_cbdata {
 	char	**cb_argv;
 } upgrade_cbdata_t;
 
+static int
+check_unsupp_fs(zfs_handle_t *zhp, void *unsupp_fs)
+{
+	int zfs_version = (int) zfs_prop_get_int(zhp, ZFS_PROP_VERSION);
+	int *count = (int *)unsupp_fs;
+
+	if (zfs_version > ZPL_VERSION) {
+		(void) printf(gettext("%s (v%d) is not supported by this "
+		    "implementation of ZFS.\n"),
+		    zfs_get_name(zhp), zfs_version);
+		(*count)++;
+	}
+
+	zfs_iter_filesystems(zhp, check_unsupp_fs, unsupp_fs);
+
+	zfs_close(zhp);
+
+	return (0);
+}
+
 static int
 upgrade_version(zpool_handle_t *zhp, uint64_t version)
 {
 	int ret;
 	nvlist_t *config;
 	uint64_t oldversion;
+	int unsupp_fs = 0;
 
 	config = zpool_get_config(zhp, NULL);
 	verify(nvlist_lookup_uint64(config, ZPOOL_CONFIG_VERSION,
@@ -4615,6 +4636,17 @@ upgrade_version(zpool_handle_t *zhp, uint64_t version)
 	assert(SPA_VERSION_IS_SUPPORTED(oldversion));
 	assert(oldversion < version);
 
+	ret = zfs_iter_root(zpool_get_handle(zhp), check_unsupp_fs, &unsupp_fs);
+	if (ret != 0)
+		return (ret);
+
+	if (unsupp_fs) {
+		(void) printf(gettext("Upgrade not performed due to %d "
+		    "unsupported filesystems (max v%d).\n"),
+		    unsupp_fs, (int) ZPL_VERSION);
+		return (1);
+	}
+
 	ret = zpool_upgrade(zhp, version);
 	if (ret != 0)
 		return (ret);

module/zfs/zfs_vfsops.c

@@ -679,12 +679,7 @@ zfs_sb_create(const char *osname, zfs_sb_t **zsbp)
 	error = zfs_get_zplprop(os, ZFS_PROP_VERSION, &zsb->z_version);
 	if (error) {
 		goto out;
-	} else if (zsb->z_version >
+	} else if (zsb->z_version > ZPL_VERSION) {
-	    zfs_zpl_version_map(spa_version(dmu_objset_spa(os)))) {
-		(void) printk("Can't mount a version %lld file system "
-		    "on a version %lld pool\n. Pool must be upgraded to mount "
-		    "this file system.", (u_longlong_t)zsb->z_version,
-		    (u_longlong_t)spa_version(dmu_objset_spa(os)));
 		error = SET_ERROR(ENOTSUP);
 		goto out;
 	}