Remove GRUB restrictions

The GRUB restrictions are based around the pool's bootfs property.
Given the current situation where GRUB is not staying current with
OpenZFS pool features, having either a non-ZFS /boot or a separate
pool with limited features are pretty much the only long-term answers
for GRUB support.  Only the second case matters in this context.  For
the restrictions to be useful, the bootfs property would have to be set
on the boot pool, because that is where we need the restrictions, as
that is the pool that GRUB reads from. The documentation for bootfs
describes it as pointing to the root pool. That's also how it's used in
the initramfs. ZFS does not allow setting bootfs to point to a dataset
in another pool. (If it did, it'd be difficult-to-impossible to enforce
these restrictions cross-pool). Accordingly, bootfs is pretty much
useless for GRUB scenarios moving forward.

Even for users who have only one pool, the existing restrictions for
GRUB are incomplete. They don't prevent you from enabling the
unsupported checksums, for example. For that reason, I have ripped out
all the GRUB restrictions.

A little longer-term, I think extending the proposed features=portable
system to define a features=grub is a much more useful approach. The
user could set that on the boot pool at creation, and things would
Just Work.

Signed-off-by: Richard Laager <rlaager@wiktel.com>

lib/libzfs/libzfs_pool.c

@@ -3104,7 +3104,6 @@ zpool_vdev_attach(zpool_handle_t *zhp,
 	uint_t children;
 	nvlist_t *config_root;
 	libzfs_handle_t *hdl = zhp->zpool_hdl;
-	boolean_t rootpool = zpool_is_bootable(zhp);
 
 	if (replacing)
 		(void) snprintf(msg, sizeof (msg), dgettext(TEXT_DOMAIN,
@@ -3164,18 +3163,8 @@ zpool_vdev_attach(zpool_handle_t *zhp,
 
 	zcmd_free_nvlists(&zc);
 
-	if (ret == 0) {
-		if (rootpool) {
-			/*
-			 * XXX need a better way to prevent user from
-			 * booting up a half-baked vdev.
-			 */
-			(void) fprintf(stderr, dgettext(TEXT_DOMAIN, "Make "
-			    "sure to wait until resilver is done "
-			    "before rebooting.\n"));
-		}
+	if (ret == 0)
 		return (0);
-	}
 
 	switch (errno) {
 	case ENOTSUP:
@@ -3594,13 +3583,6 @@ zpool_vdev_remove(zpool_handle_t *zhp, const char *path)
 		return (zfs_error(hdl, EZFS_BADVERSION, msg));
 	}
 
-	if (!islog && !avail_spare && !l2cache && zpool_is_bootable(zhp)) {
-		zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
-		    "root pool can not have removed devices, "
-		    "because GRUB does not understand them"));
-		return (zfs_error(hdl, EINVAL, msg));
-	}
-
 	zc.zc_guid = fnvlist_lookup_uint64(tgt, ZPOOL_CONFIG_GUID);
 
 	if (zfs_ioctl(hdl, ZFS_IOC_VDEV_REMOVE, &zc) == 0)

man/man8/zfs.8

@@ -1191,9 +1191,6 @@ The
 and
 .Sy edonr
 checksum algorithms require enabling the appropriate features on the pool.
-These algorithms are not supported by GRUB and should not be set on the
-.Sy bootfs
-filesystem when using GRUB to boot the system.
 Please see
 .Xr zpool-features 5
 for more information on these algorithms.

module/zfs/spa.c

@@ -609,27 +609,9 @@ spa_prop_validate(spa_t *spa, nvlist_t *props)
 				if (error != 0)
 					break;
 
-				/*
-				 * Must be ZPL, and its property settings
-				 * must be supported by GRUB (compression
-				 * is not gzip, and large blocks or large
-				 * dnodes are not used).
-				 */
-
+				/* Must be ZPL. */
 				if (dmu_objset_type(os) != DMU_OST_ZFS) {
 					error = SET_ERROR(ENOTSUP);
-				} else if ((error =
-				    dsl_prop_get_int_ds(dmu_objset_ds(os),
-				    zfs_prop_to_name(ZFS_PROP_COMPRESSION),
-				    &propval)) == 0 &&
-				    !BOOTFS_COMPRESS_VALID(propval)) {
-					error = SET_ERROR(ENOTSUP);
-				} else if ((error =
-				    dsl_prop_get_int_ds(dmu_objset_ds(os),
-				    zfs_prop_to_name(ZFS_PROP_DNODESIZE),
-				    &propval)) == 0 &&
-				    propval != ZFS_DNSIZE_LEGACY) {
-					error = SET_ERROR(ENOTSUP);
 				} else {
 					objnum = dmu_objset_id(os);
 				}

module/zfs/zfs_ioctl.c

@@ -346,23 +346,6 @@ history_str_get(zfs_cmd_t *zc)
 	return (buf);
 }
 
-/*
- * Check to see if the named dataset is currently defined as bootable
- */
-static boolean_t
-zfs_is_bootfs(const char *name)
-{
-	objset_t *os;
-
-	if (dmu_objset_hold(name, FTAG, &os) == 0) {
-		boolean_t ret;
-		ret = (dmu_objset_id(os) == spa_bootfs(dmu_objset_spa(os)));
-		dmu_objset_rele(os, FTAG);
-		return (ret);
-	}
-	return (B_FALSE);
-}
-
 /*
  * Return non-zero if the spa version is less than requested version.
  */
@@ -4285,18 +4268,6 @@ zfs_check_settable(const char *dsname, nvpair_t *pair, cred_t *cr)
 				}
 				spa_close(spa, FTAG);
 			}
-
-			/*
-			 * If this is a bootable dataset then
-			 * verify that the compression algorithm
-			 * is supported for booting. We must return
-			 * something other than ENOTSUP since it
-			 * implies a downrev pool version.
-			 */
-			if (zfs_is_bootfs(dsname) &&
-			    !BOOTFS_COMPRESS_VALID(intval)) {
-				return (SET_ERROR(ERANGE));
-			}
 		}
 		break;
 
@@ -4338,16 +4309,6 @@ zfs_check_settable(const char *dsname, nvpair_t *pair, cred_t *cr)
 		    intval != ZFS_DNSIZE_LEGACY) {
 			spa_t *spa;
 
-			/*
-			 * If this is a bootable dataset then
-			 * we don't allow large (>512B) dnodes,
-			 * because GRUB doesn't support them.
-			 */
-			if (zfs_is_bootfs(dsname) &&
-			    intval != ZFS_DNSIZE_LEGACY) {
-				return (SET_ERROR(EDOM));
-			}
-
 			if ((err = spa_open(dsname, &spa, FTAG)) != 0)
 				return (err);