Add zfs module feature and property info to sysfs

This extends our sysfs '/sys/module/zfs' entry to include feature 
and property attributes. The primary consumer of this information 
is user processes, like the zfs CLI, that need to know what the 
current loaded ZFS module supports. The libzfs binary will consult 
this information when instantiating the zfs and zpool property 
tables and the pool features table.

This introduces 4 kernel objects (dirs) into '/sys/module/zfs'
with corresponding attributes (files):
  features.runtime
  features.pool
  properties.dataset
  properties.pool

Reviewed-by: Matthew Ahrens <[email protected]>
Reviewed-by: Tony Hutter <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Don Brady <[email protected]>
Closes #7706 

1 files changed, 16 insertions, 0 deletions

diff --git a/lib/libzfs/libzfs_util.c b/lib/libzfs/libzfs_util.c
index a19b34415..d18b582c6 100644
--- a/lib/libzfs/libzfs_util.c
+++ b/lib/libzfs/libzfs_util.c
@@ -1091,6 +1091,22 @@ libzfs_init(void)
 		hdl->libzfs_prop_debug = B_TRUE;
 	}
 
+	/*
+	 * For testing, remove some settable properties and features
+	 */
+	if (libzfs_envvar_is_set("ZFS_SYSFS_PROP_SUPPORT_TEST")) {
+		zprop_desc_t *proptbl;
+
+		proptbl = zpool_prop_get_table();
+		proptbl[ZPOOL_PROP_COMMENT].pd_zfs_mod_supported = B_FALSE;
+
+		proptbl = zfs_prop_get_table();
+		proptbl[ZFS_PROP_DNODESIZE].pd_zfs_mod_supported = B_FALSE;
+
+		zfeature_info_t *ftbl = spa_feature_table;
+		ftbl[SPA_FEATURE_LARGE_BLOCKS].fi_zfs_mod_supported = B_FALSE;
+	}
+
 	return (hdl);
 }