blkftrace: binary tracing, synthesizing old format
Impact: new feature
With this and a blkrawverify modified not to verify the sequence numbers
we can start using the userspace tools to verify that the data produced
with the ftrace plugin works as expected.
Example:
[root@f10-1 ~]# echo 1 > /sys/block/sda/sda1/trace/enable
[root@f10-1 ~]# echo bin > /d/tracing/trace_options
[root@f10-1 ~]# echo blk > /d/tracing/current_tracer
[root@f10-1 ~]# cat /d/tracing/trace_pipe > sda1.blktrace.0
^C
[root@f10-1 ~]# ./blkrawverify --noseq sda1
Verifying sda1
CPU 0
Wrote output to sda1.verify.out
[root@f10-1 ~]# cat sda1.verify.out
---------------
Verifying sda1
---------------------
Summary for cpu 0:
1349 valid + 0 invalid (100.0%) processed
[root@f10-1 ~]#
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/block/blktrace.c b/block/blktrace.c
index 570cd3c..4f45b34 100644
--- a/block/blktrace.c
+++ b/block/blktrace.c
@@ -219,9 +219,16 @@
t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
t->sequence = ++(*sequence);
t->time = ktime_to_ns(ktime_get());
- t->cpu = cpu;
- t->pid = pid;
record_it:
+ /*
+ * These two are not needed in ftrace as they are in the
+ * generic trace_entry, filled by tracing_generic_entry_update,
+ * but for the trace_event->bin() synthesizer benefit we do it
+ * here too.
+ */
+ t->cpu = cpu;
+ t->pid = pid;
+
t->sector = sector;
t->bytes = bytes;
t->action = what;
@@ -1086,6 +1093,7 @@
if (blk_register_tracepoints())
atomic_dec(&blk_probes_ref);
mutex_unlock(&blk_probe_mutex);
+ trace_flags &= ~TRACE_ITER_CONTEXT_INFO;
}
static int blk_tracer_init(struct trace_array *tr)
@@ -1100,6 +1108,7 @@
static void blk_tracer_stop(struct trace_array *tr)
{
+ trace_flags |= TRACE_ITER_CONTEXT_INFO;
mutex_lock(&blk_probe_mutex);
if (atomic_dec_and_test(&blk_probes_ref))
blk_unregister_tracepoints();
@@ -1147,6 +1156,9 @@
const u16 what = t->action & ((1 << BLK_TC_SHIFT) - 1);
int ret;
+ if (trace_print_context(iter))
+ return TRACE_TYPE_PARTIAL_LINE;
+
if (unlikely(what == 0 || what > ARRAY_SIZE(what2act)))
ret = trace_seq_printf(s, "Bad pc action %x\n", what);
else {
@@ -1159,6 +1171,28 @@
return ret ? TRACE_TYPE_HANDLED : TRACE_TYPE_PARTIAL_LINE;
}
+static int blk_trace_synthesize_old_trace(struct trace_iterator *iter)
+{
+ struct trace_seq *s = &iter->seq;
+ struct blk_io_trace *t = (struct blk_io_trace *)iter->ent;
+ const int offset = offsetof(struct blk_io_trace, sector);
+ struct blk_io_trace old = {
+ .magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION,
+ .time = ns2usecs(iter->ts),
+ };
+
+ if (!trace_seq_putmem(s, &old, offset))
+ return 0;
+ return trace_seq_putmem(s, &t->sector,
+ sizeof(old) - offset + t->pdu_len);
+}
+
+static int blk_trace_event_print_binary(struct trace_iterator *iter, int flags)
+{
+ return blk_trace_synthesize_old_trace(iter) ?
+ TRACE_TYPE_HANDLED : TRACE_TYPE_PARTIAL_LINE;
+}
+
static enum print_line_t blk_tracer_print_line(struct trace_iterator *iter)
{
const struct blk_io_trace *t;
@@ -1200,7 +1234,7 @@
.latency_trace = blk_trace_event_print,
.raw = trace_nop_print,
.hex = trace_nop_print,
- .binary = trace_nop_print,
+ .binary = blk_trace_event_print_binary,
};
static int __init init_blk_tracer(void)
