[JFFS2][XATTR] using 'delete marker' for xdatum/xref deletion

- When xdatum is removed, a new xdatum with 'delete marker' is
  written. (version==0xffffffff means 'delete marker')
- When xref is removed, a new xref with 'delete marker' is written.
  (odd-numbered xseqno means 'delete marker')

- delete_xattr_(datum/xref)_delay() are new deletion functions
  are added. We can only use them if we can detect the target
  obsolete xdatum/xref as a orphan or errir one.
  (e.g when inode deletion, or detecting crc error)

[1/3] jffs2-xattr-v6-01-delete_marker.patch

Signed-off-by: KaiGai Kohei <kaigai@ak.jp.nec.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>

include/linux/jffs2.h

@@ -186,6 +186,7 @@ struct jffs2_raw_xref
 	jint32_t hdr_crc;
 	jint32_t ino;		/* inode number */
 	jint32_t xid;		/* XATTR identifier number */
+	jint32_t xseqno;	/* xref sequencial number */
 	jint32_t node_crc;
 } __attribute__((packed));