seq_buf: Make trace_seq_putmem_hex() support data longer than 8

Since the raw memory 'data' does not go forward, it will dump repeated
data if the data length is more than 8. If we want to dump longer data
blocks, we need to repeatedly call macro SEQ_PUT_HEX_FIELD. I think it
is a bit redundant, and multiple function calls also affect the performance.

Link: https://lore.kernel.org/lkml/[email protected]/
Link: https://lkml.kernel.org/r/[email protected]

Cc: [email protected]
Fixes: 6d2289f ("tracing: Make trace_seq_putmem_hex() more robust")
Signed-off-by: Yun Zhou <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>

Author: zhouyun1306

lib/seq_buf.c

@@ -245,12 +245,14 @@ int seq_buf_putmem_hex(struct seq_buf *s, const void *mem,
 			break;
 
 		/* j increments twice per loop */
-		len -= j / 2;
 		hex[j++] = ' ';
 
 		seq_buf_putmem(s, hex, j);
 		if (seq_buf_has_overflowed(s))
 			return -1;
+
+		len -= start_len;
+		data += start_len;
 	}
 	return 0;
 }