scoutfs-utils: hidden and indexed xattrs

Add support for the xattr tags which can hide or index xattrs by their
name.  We get an item that indexes inodes by the presence of an xattr, a
listxattr_raw ioctl which can show hidden xattrs, and an ioctl that
finds inodes which have an xattr.

Signed-off-by: Zach Brown <zab@versity.com>

utils/src/format.h

@@ -108,6 +108,11 @@ struct scoutfs_key {
 #define skii_major	_sk_second
 #define skii_ino	_sk_third
 
+/* xattr index */
+#define skxi_hash	_sk_first
+#define skxi_ino	_sk_second
+#define skxi_id		_sk_third
+
 /* node free extent */
 #define sknf_node_id	_sk_first
 #define sknf_major	_sk_second
@@ -351,9 +356,10 @@ struct scoutfs_segment_block {
  * Keys are first sorted by major key zones.
  */
 #define SCOUTFS_INODE_INDEX_ZONE		1
-#define SCOUTFS_NODE_ZONE			2
-#define SCOUTFS_FS_ZONE				3
-#define SCOUTFS_LOCK_ZONE			4
+#define SCOUTFS_XATTR_INDEX_ZONE		2
+#define SCOUTFS_NODE_ZONE			3
+#define SCOUTFS_FS_ZONE				4
+#define SCOUTFS_LOCK_ZONE			5
 #define SCOUTFS_MAX_ZONE			8 /* power of 2 is efficient */
 
 /* inode index zone */
@@ -361,6 +367,9 @@ struct scoutfs_segment_block {
 #define SCOUTFS_INODE_INDEX_DATA_SEQ_TYPE	2
 #define SCOUTFS_INODE_INDEX_NR			3 /* don't forget to update */
 
+/* xattr index zone */
+#define SCOUTFS_XATTR_INDEX_NAME_TYPE		1
+
 /* node zone (also used in server alloc btree) */
 #define SCOUTFS_FREE_EXTENT_BLKNO_TYPE		1
 #define SCOUTFS_FREE_EXTENT_BLOCKS_TYPE		2