cachefiles: Add auxiliary data trace

Add a display of the first 8 bytes of the downloaded auxiliary data and of
the on-disk stored auxiliary data as these are used in coherency
management. In the case of afs, this holds the data version number.

Signed-off-by: David Howells <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
cc: Jeff Layton <[e-mail]>
cc: [e-mail]
cc: [e-mail]
Signed-off-by: Christian Brauner <[e-mail]>

fs/cachefiles/xattr.c

···
 		trace_cachefiles_vfs_error(object, file_inode(file), ret,
 					   cachefiles_trace_setxattr_error);
 		trace_cachefiles_coherency(object, file_inode(file)->i_ino,
+					   be64_to_cpup((__be64 *)buf->data),
 					   buf->content,
 					   cachefiles_coherency_set_fail);
 		if (ret != -ENOMEM)
···
 				"Failed to set xattr with error %d", ret);
 	} else {
 		trace_cachefiles_coherency(object, file_inode(file)->i_ino,
+					   be64_to_cpup((__be64 *)buf->data),
 					   buf->content,
 					   cachefiles_coherency_set_ok);
 	}
···
 				object,
 				"Failed to read aux with error %zd", xlen);
 		why = cachefiles_coherency_check_xattr;
-	} else if (buf->type != CACHEFILES_COOKIE_TYPE_DATA) {
+		goto out;
+	}
+
+	if (buf->type != CACHEFILES_COOKIE_TYPE_DATA) {
 		why = cachefiles_coherency_check_type;
 	} else if (memcmp(buf->data, p, len) != 0) {
 		why = cachefiles_coherency_check_aux;
···
 		ret = 0;
 	}
 
+out:
 	trace_cachefiles_coherency(object, file_inode(file)->i_ino,
+				   be64_to_cpup((__be64 *)buf->data),
 				   buf->content, why);
 	kfree(buf);
 	return ret;

include/trace/events/cachefiles.h

···
 TRACE_EVENT(cachefiles_coherency,
 	    TP_PROTO(struct cachefiles_object *obj,
 		     ino_t ino,
+		     u64 disk_aux,
 		     enum cachefiles_content content,
 		     enum cachefiles_coherency_trace why),
 
-	    TP_ARGS(obj, ino, content, why),
+	    TP_ARGS(obj, ino, disk_aux, content, why),
 
 	    /* Note that obj may be NULL */
 	    TP_STRUCT__entry(
···
 		    __field(enum cachefiles_coherency_trace,	why)
 		    __field(enum cachefiles_content,		content)
 		    __field(u64,				ino)
+		    __field(u64,				aux)
+		    __field(u64,				disk_aux)
 			     ),
 
 	    TP_fast_assign(
···
 		    __entry->why	= why;
 		    __entry->content	= content;
 		    __entry->ino	= ino;
+		    __entry->aux	= be64_to_cpup((__be64 *)obj->cookie->inline_aux);
+		    __entry->disk_aux	= disk_aux;
 			   ),
 
-	    TP_printk("o=%08x %s B=%llx c=%u",
+	    TP_printk("o=%08x %s B=%llx c=%u aux=%llx dsk=%llx",
 		      __entry->obj,
 		      __print_symbolic(__entry->why, cachefiles_coherency_traces),
 		      __entry->ino,
-		      __entry->content)
+		      __entry->content,
+		      __entry->aux,
+		      __entry->disk_aux)
 	    );
 
 TRACE_EVENT(cachefiles_vol_coherency,