blktrace: print out BLK_TN_MESSAGE properly

Impact: improve ftrace plugin output

Before this patch:

 # cat trace
         make-5383  [001]   741.240059:   8,7    P   N [make]
 __trace_note_message: cfq1074

 # echo 1 > options/blk_classic
 # cat trace
   8,7    1     0.692221252     0  C   W 130411392 + 1024 [0]
 Bad pc action 6361
 Bad pc action 283d

 # echo 0 > options/blk_classic
 # echo bin > trace_options
 # cat trace_pipe | blkparse -i -
 (can't parse messages generated by blk_add_trace_msg())

After this patch:
 # cat trace
      <idle>-0     [001]   187.600933:   8,7    C   W 145220224 + 8 [0]
      <idle>-0     [001]   187.600946:   8,7    m   N cfq1076 complete

 # echo 1 > options/blk_classic
 # cat trace
   8,7    1     0.256378996   238  I   W 113190728 + 8 [pdflush]
   8,7    1     0.256378998   238  m   N cfq1076 insert_request

 # echo 0 > options/blk_classic
 # echo bin > trace_options
 # cat trace_pipe | blkparse -i -
  8,7    1        0    22.973250293     0  C   W 102770576 + 8 [0]
  8,7    1        0    22.973259213     0  m   N cfq1076 complete

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Jens Axboe <jens.axboe@oracle.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index c103b0c..947c5b3 100644 (file)
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -59,22 +59,39 @@ static void trace_note(struct blk_trace *bt, pid_t pid, int action,
                       const void *data, size_t len)
 {
        struct blk_io_trace *t;
+       struct ring_buffer_event *event = NULL;
+       int pc = 0;
+       int cpu = smp_processor_id();
+       bool blk_tracer = blk_tracer_enabled;
+
+       if (blk_tracer) {
+               pc = preempt_count();
+               event = trace_buffer_lock_reserve(blk_tr, TRACE_BLK,
+                                                 sizeof(*t) + len,
+                                                 0, pc);
+               if (!event)
+                       return;
+               t = ring_buffer_event_data(event);
+               goto record_it;
+       }
 
        if (!bt->rchan)
                return;
 
        t = relay_reserve(bt->rchan, sizeof(*t) + len);
        if (t) {
-               const int cpu = smp_processor_id();
-
                t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
                t->time = ktime_to_ns(ktime_get());
+record_it:
                t->device = bt->dev;
                t->action = action;
                t->pid = pid;
                t->cpu = cpu;
                t->pdu_len = len;
                memcpy((void *) t + sizeof(*t), data, len);
+
+               if (blk_tracer)
+                       trace_buffer_unlock_commit(blk_tr, event, 0, pc);
        }
 }
 
@@ -110,14 +127,8 @@ void __trace_note_message(struct blk_trace *bt, const char *fmt, ...)
        unsigned long flags;
        char *buf;
 
-       if (blk_tracer_enabled) {
-               va_start(args, fmt);
-               ftrace_vprintk(fmt, args);
-               va_end(args);
-               return;
-       }
-
-       if (!bt->msg_data)
+       if (unlikely(bt->trace_state != Blktrace_running &&
+                    !blk_tracer_enabled))
                return;
 
        local_irq_save(flags);
@@ -168,9 +179,9 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
        unsigned long *sequence;
        pid_t pid;
        int cpu, pc = 0;
+       bool blk_tracer = blk_tracer_enabled;
 
-       if (unlikely(bt->trace_state != Blktrace_running &&
-                    !blk_tracer_enabled))
+       if (unlikely(bt->trace_state != Blktrace_running && !blk_tracer))
                return;
 
        what |= ddir_act[rw & WRITE];
@@ -185,7 +196,7 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
                return;
        cpu = raw_smp_processor_id();
 
-       if (blk_tracer_enabled) {
+       if (blk_tracer) {
                tracing_record_cmdline(current);
 
                pc = preempt_count();
@@ -235,7 +246,7 @@ record_it:
                if (pdu_len)
                        memcpy((void *) t + sizeof(*t), pdu_data, pdu_len);
 
-               if (blk_tracer_enabled) {
+               if (blk_tracer) {
                        trace_buffer_unlock_commit(blk_tr, event, 0, pc);
                        return;
                }
@@ -922,6 +933,11 @@ static void fill_rwbs(char *rwbs, const struct blk_io_trace *t)
        int i = 0;
        int tc = t->action >> BLK_TC_SHIFT;
 
+       if (t->action == BLK_TN_MESSAGE) {
+               rwbs[i++] = 'N';
+               goto out;
+       }
+
        if (tc & BLK_TC_DISCARD)
                rwbs[i++] = 'D';
        else if (tc & BLK_TC_WRITE)
@@ -939,7 +955,7 @@ static void fill_rwbs(char *rwbs, const struct blk_io_trace *t)
                rwbs[i++] = 'S';
        if (tc & BLK_TC_META)
                rwbs[i++] = 'M';
-
+out:
        rwbs[i] = '\0';
 }
 
@@ -1074,6 +1090,17 @@ static int blk_log_split(struct trace_seq *s, const struct trace_entry *ent)
                                get_pdu_int(ent), cmd);
 }
 
+static int blk_log_msg(struct trace_seq *s, const struct trace_entry *ent)
+{
+       int ret;
+       const struct blk_io_trace *t = te_blk_io_trace(ent);
+
+       ret = trace_seq_putmem(s, t + 1, t->pdu_len);
+       if (ret)
+               return trace_seq_putc(s, '\n');
+       return ret;
+}
+
 /*
  * struct tracer operations
  */
@@ -1146,6 +1173,13 @@ static enum print_line_t print_one_line(struct trace_iterator *iter,
        long_act   = !!(trace_flags & TRACE_ITER_VERBOSE);
        log_action = classic ? &blk_log_action_classic : &blk_log_action;
 
+       if (t->action == BLK_TN_MESSAGE) {
+               ret = log_action(iter, long_act ? "message" : "m");
+               if (ret)
+                       ret = blk_log_msg(s, iter->ent);
+               goto out;
+       }
+
        if (unlikely(what == 0 || what >= ARRAY_SIZE(what2act)))
                ret = trace_seq_printf(s, "Bad pc action %x\n", what);
        else {
@@ -1153,7 +1187,7 @@ static enum print_line_t print_one_line(struct trace_iterator *iter,
                if (ret)
                        ret = what2act[what].print(s, iter->ent);
        }
-
+out:
        return ret ? TRACE_TYPE_HANDLED : TRACE_TYPE_PARTIAL_LINE;
 }
 
@@ -1253,11 +1287,16 @@ static int blk_trace_remove_queue(struct request_queue *q)
 static int blk_trace_setup_queue(struct request_queue *q, dev_t dev)
 {
        struct blk_trace *old_bt, *bt = NULL;
+       int ret = -ENOMEM;
 
        bt = kzalloc(sizeof(*bt), GFP_KERNEL);
        if (!bt)
                return -ENOMEM;
 
+       bt->msg_data = __alloc_percpu(BLK_TN_MAX_MSG, __alignof__(char));
+       if (!bt->msg_data)
+               goto free_bt;
+
        bt->dev = dev;
        bt->act_mask = (u16)-1;
        bt->end_lba = -1ULL;
@@ -1265,14 +1304,17 @@ static int blk_trace_setup_queue(struct request_queue *q, dev_t dev)
        old_bt = xchg(&q->blk_trace, bt);
        if (old_bt != NULL) {
                (void)xchg(&q->blk_trace, old_bt);
-               kfree(bt);
-               return -EBUSY;
+               ret = -EBUSY;
+               goto free_bt;
        }
 
        if (atomic_inc_return(&blk_probes_ref) == 1)
                blk_register_tracepoints();
-
        return 0;
+
+free_bt:
+       blk_trace_free(bt);
+       return ret;
 }
 
 /*