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Subject[PATCH] blktrace: fix context-info when mixed-using blk tracer and trace events
When set current tracer to blk tracer, TRACE_ITER_CONTEXT_INFO is unset,
but actually context-info is printed:
pdflush-431 [000] 821.181576: 8,0 P N [pdflush]

And then if we enable TRACE_ITER_CONTEXT_INFO:
# echo context-info > trace_options

We'll see context-info is printed twice. What's worse is, when use blk
tracer and trace events at a time, we'll see no context-info for trace
events:
jbd2_commit_logging: dev dm-0:8 transaction 333227
jbd2_end_commit: dev dm-0:8 transaction 333227 head 332814
rm-25433 [001] 9578.307485: 8,18 m N cfq25433 slice expired t=0
rm-25433 [001] 9578.307486: 8,18 m N cfq25433 put_queue

This patch adds blk_tracer->set_flags(), and context-info flag is unset
only when we set the output to classic mode.

Note after this patch, one should unset context-info explicitly if he
wants to get binary output that can be parsed by blkparse:
# echo nocontext-info > trace_options
# echo bin > trace_options
# echo blk > current_tracer
# cat trace_pipe | blkparse -i -

Reported-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
kernel/trace/blktrace.c | 18 +++++++++++++-----
1 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 8e7c5da..c32062b 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -1211,7 +1211,6 @@ static void blk_tracer_print_header(struct seq_file *m)
static void blk_tracer_start(struct trace_array *tr)
{
blk_tracer_enabled = true;
- trace_flags &= ~TRACE_ITER_CONTEXT_INFO;
}

static int blk_tracer_init(struct trace_array *tr)
@@ -1224,7 +1223,6 @@ static int blk_tracer_init(struct trace_array *tr)
static void blk_tracer_stop(struct trace_array *tr)
{
blk_tracer_enabled = false;
- trace_flags |= TRACE_ITER_CONTEXT_INFO;
}

static void blk_tracer_reset(struct trace_array *tr)
@@ -1289,9 +1287,6 @@ out:
static enum print_line_t blk_trace_event_print(struct trace_iterator *iter,
int flags)
{
- if (!trace_print_context(iter))
- return TRACE_TYPE_PARTIAL_LINE;
-
return print_one_line(iter, false);
}

@@ -1326,6 +1321,18 @@ static enum print_line_t blk_tracer_print_line(struct trace_iterator *iter)
return print_one_line(iter, true);
}

+static int blk_tracer_set_flag(u32 old_flags, u32 bit, int set)
+{
+ /* don't output context-info for blk_classic output */
+ if (bit == TRACE_BLK_OPT_CLASSIC) {
+ if (set)
+ trace_flags &= ~TRACE_ITER_CONTEXT_INFO;
+ else
+ trace_flags |= TRACE_ITER_CONTEXT_INFO;
+ }
+ return 0;
+}
+
static struct tracer blk_tracer __read_mostly = {
.name = "blk",
.init = blk_tracer_init,
@@ -1335,6 +1342,7 @@ static struct tracer blk_tracer __read_mostly = {
.print_header = blk_tracer_print_header,
.print_line = blk_tracer_print_line,
.flags = &blk_tracer_flags,
+ .set_flag = blk_tracer_set_flag,
};

static struct trace_event trace_blk_event = {
--
1.5.4.rc3


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