Date:	Fri, 16 Jan 2009 16:16:11 -0200
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	Jens Axboe <jens.axboe@...cle.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org
Subject: [RFC][PATCH] ftrace interface for blktrace

Hi Jens,

	The patch below adds a ftrace interface for blktrace, allowing
people to use it without any required userspace tools, using sysfs to setup the
act_mask, pid, start_lba, end_lba.

	Example usage:

[root@...-1 ~]# mount -t debugfs none /sys/kernel/debug/
[root@...-1 ~]# ls /sys/block/sda/sda1/trace/
act_mask  enable  end_lba  pid  start_lba
[root@...-1 ~]# cat /sys/kernel/debug/tracing/available_tracers 
blk function_graph wakeup function sched_switch nop
[root@...-1 ~]# echo blk > /sys/kernel/debug/tracing/current_tracer 
[root@...-1 ~]# cat /sys/kernel/debug/tracing/trace
# tracer: blk
#
# DEV   CPU TIMESTAMP     PID ACT FLG
#  |     |     |           |   |   |
[root@...-1 ~]# echo 1 > /sys/block/sda/sda1/trace/enable 
[root@...-1 ~]# tail /sys/kernel/debug/tracing/trace
  8,1    0   143.070085  1208  P  NS [tail]
  8,1    0   143.070087  1208  I RBS 4154375 + 8 [tail]
  8,1    0   143.070091  1208  A WBS 4155391 + 16 <- (8,1) 4155328
  8,1    0   143.070091  1208  Q   R 4155391 + 16 [tail]
  8,1    0   143.070094  1208  G  RB 4155391 + 16 [tail]
  8,1    0   143.070094  1208  I RBS 4155391 + 16 [tail]
  8,1    0   143.070097  1208  U  WS [tail] 2
  8,1    0   143.070101  1208  D  WB 4154375 + 8 [tail]
  8,1    0   143.070341  1208  D  WB 4155391 + 16 [tail]
  8,1    0   143.070635     0  C  RS 4154375 + 8 [0]
[root@...-1 ~]#

	Filters can be set using:

[root@...-1 ~]# echo write,sync > /sys/block/sda/sda1/trace/act_mask 
[root@...-1 ~]# cat /sys/block/sda/sda1/trace/act_mask 
0xa

	One can go on interactively adding more filters, for instance:

[root@...-1 ~]# echo `pidof kjournald` > /sys/block/sda/sda1/trace/pid
[root@...-1 ~]# cat /sys/block/sda/sda1/trace/pid
423

	And use the existing ftrace infrastructure to, for instance,
replicate the btrace (blktrace -o - | blkparse) functionality by simply
using cat:

[root@...-1 ~]# cat /sys/kernel/debug/tracing/trace_pipe 
  8,1    0   457.253356   423  A WBS 6335 + 8 <- (8,1) 6272
  8,1    0   457.253360   423  Q   R 6335 + 8 [kjournald]
  8,1    0   457.253367   423  G  RB 6335 + 8 [kjournald]
  8,1    0   457.253372   423  I RBS 6335 + 8 [kjournald]
  8,1    0   457.253376   423  A WBS 6343 + 8 <- (8,1) 6280
  8,1    0   457.253376   423  Q   R 6343 + 8 [kjournald]
  8,1    0   457.253378   423  M   W 6343 + 8 [kjournald]
  8,1    0   457.253380   423  A WBS 6351 + 8 <- (8,1) 6288
CONTROL+C
[root@...-1 ~]#

	This patch was done on Linus tree, I'll now work with it on
linux-tip so that I can experiment with binary tracing, i.e to ask for
the output of /sys/kernel/debug/tracing/trace_pipe to be raw, exactly
the one provide by relayfs based variant, so that we will be able to
continue using blkparse to validate the trace entries, as a debugging
aid.

	Also there are other interesting things that one gets from using
the ftrace infrastructure, such as being able to set see traffic that
happens in just a cpuset (/sys/kernel/debug/tracing/tracing_cpumask),
and others that I plan to add such as what Steve did in "[PATCH 2/2]
ftrace: add stack trace to function tracer", so that we could have
things like (made up example):

[root@...-1 ~]# cat /sys/kernel/debug/tracing/trace_pipe 
  8,1    0   457.253356   423  A WBS 6335 + 8 <- (8,1) 6272
  8,1    0   457.253360   423  Q   R 6335 + 8 [kjournald]
  8,1    0   457.253367   423  G  RB 6335 + 8 [kjournald]
  8,1    0   457.253372   423  I RBS 6335 + 8 [kjournald]
 <= sync_buffer
 <= __wait_on_bit
 <= out_of_line_wait_on_bit
 <= __wait_on_buffer
 <= sync_dirty_buffer
 <= journal_commit_transaction
 <= kjournald
  8,1    0   457.253376   423  A WBS 6343 + 8 <- (8,1) 6280
  8,1    0   457.253376   423  Q   R 6343 + 8 [kjournald]
  8,1    0   457.253378   423  M   W 6343 + 8 [kjournald]
  8,1    0   457.253380   423  A WBS 6351 + 8 <- (8,1) 6288

	More polishing is needed, I wrote the patch this way just to
show where things are different, with new code, for registering the
tracer, bits stolen from the userspace blktrace, allowing config via
sysfs at the bottom.

	Ideally we would move this to kernel/trace/block.c, break it
into smaller self contained patches, etc.

Comments?

- Arnaldo

 block/blktrace.c      |  578 +++++++++++++++++++++++++++++++++++++++++++++++++-
 fs/partitions/check.c |    7 
 2 files changed, 583 insertions(+), 2 deletions(-)

diff --git a/block/blktrace.c b/block/blktrace.c
index b0a2cae..10985f9 100644
--- a/block/blktrace.c
+++ b/block/blktrace.c
@@ -25,9 +25,13 @@
 #include <linux/time.h>
 #include <trace/block.h>
 #include <asm/uaccess.h>
+#include <../kernel/trace/trace.h>
 
 static unsigned int blktrace_seq __read_mostly = 1;
 
+static struct trace_array *blk_tr;
+static int __read_mostly  blk_tracer_enabled;
+
 /* Global reference count of probes */
 static DEFINE_MUTEX(blk_probe_mutex);
 static atomic_t blk_probes_ref = ATOMIC_INIT(0);
@@ -43,6 +47,9 @@ static void trace_note(struct blk_trace *bt, pid_t pid, int action,
 {
 	struct blk_io_trace *t;
 
+	if (!bt->rchan)
+		return;
+
 	t = relay_reserve(bt->rchan, sizeof(*t) + len);
 	if (t) {
 		const int cpu = smp_processor_id();
@@ -90,6 +97,9 @@ void __trace_note_message(struct blk_trace *bt, const char *fmt, ...)
 	unsigned long flags;
 	char *buf;
 
+	if (!bt->msg_data)
+		return;
+
 	local_irq_save(flags);
 	buf = per_cpu_ptr(bt->msg_data, smp_processor_id());
 	va_start(args, fmt);
@@ -131,13 +141,14 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
 		     int rw, u32 what, int error, int pdu_len, void *pdu_data)
 {
 	struct task_struct *tsk = current;
+	struct ring_buffer_event *event = NULL;
 	struct blk_io_trace *t;
 	unsigned long flags;
 	unsigned long *sequence;
 	pid_t pid;
 	int cpu;
 
-	if (unlikely(bt->trace_state != Blktrace_running))
+	if (unlikely(bt->trace_state != Blktrace_running || !blk_tracer_enabled))
 		return;
 
 	what |= ddir_act[rw & WRITE];
@@ -158,6 +169,25 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
 	 */
 	local_irq_save(flags);
 
+	if (blk_tr) {
+		struct trace_array_cpu *data;
+
+		tracing_record_cmdline(current);
+		cpu = raw_smp_processor_id();
+		data = blk_tr->data[cpu];
+
+		if (unlikely(atomic_read(&data->disabled)))
+			goto out_local_irq_restore;
+
+		event = ring_buffer_lock_reserve(blk_tr->buffer,
+						 sizeof(*t) + pdu_len, &flags);
+		if (!event)
+			goto out_local_irq_restore;
+		
+		t = ring_buffer_event_data(event);
+		goto record_it;
+	}
+
 	if (unlikely(tsk->btrace_seq != blktrace_seq))
 		trace_note_tsk(bt, tsk);
 
@@ -169,19 +199,26 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
 		t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
 		t->sequence = ++(*sequence);
 		t->time = ktime_to_ns(ktime_get());
+		t->cpu = cpu;
+record_it:
 		t->sector = sector;
 		t->bytes = bytes;
 		t->action = what;
 		t->pid = pid;
 		t->device = bt->dev;
-		t->cpu = cpu;
 		t->error = error;
 		t->pdu_len = pdu_len;
 
 		if (pdu_len)
 			memcpy((void *) t + sizeof(*t), pdu_data, pdu_len);
+
+		if (blk_tr) {
+			ring_buffer_unlock_commit(blk_tr->buffer, event, flags);
+			trace_wake_up();
+		}
 	}
 
+out_local_irq_restore:
 	local_irq_restore(flags);
 }
 
@@ -888,3 +925,540 @@ static void blk_unregister_tracepoints(void)
 
 	tracepoint_synchronize_unregister();
 }
+
+/*
+ * struct blk_io_tracer formatting routines
+ */
+
+static void fill_rwbs(char *rwbs, struct blk_io_trace *t)
+{
+        int i = 0;
+
+        if (t->action & BLK_TC_DISCARD)	   rwbs[i++] = 'D';
+        else if (t->action & BLK_TC_WRITE) rwbs[i++] = 'W';
+        else if (t->bytes)		   rwbs[i++] = 'R';
+        else				   rwbs[i++] = 'N';
+
+        if (t->action & BLK_TC_AHEAD)	   rwbs[i++] = 'A';
+        if (t->action & BLK_TC_BARRIER)	   rwbs[i++] = 'B';
+        if (t->action & BLK_TC_SYNC)	   rwbs[i++] = 'S';
+        if (t->action & BLK_TC_META)	   rwbs[i++] = 'M';
+
+        rwbs[i] = '\0';
+}
+
+static inline void *pdu_start(struct blk_io_trace *t)
+{
+	return t + 1;
+}
+
+static inline u32 t_sec(const struct blk_io_trace *t)
+{
+	return t->bytes >> 9;
+}
+
+static __u64 get_pdu_int(struct blk_io_trace *t)
+{
+	__u64 *val = pdu_start(t);
+
+	return be64_to_cpu(*val);
+}
+
+static void get_pdu_remap(struct blk_io_trace *t, struct blk_io_trace_remap *r)
+{
+	struct blk_io_trace_remap *__r = pdu_start(t);
+	__u64 sector = __r->sector;
+
+	r->device = be32_to_cpu(__r->device);
+	r->device_from = be32_to_cpu(__r->device_from);
+	r->sector = be64_to_cpu(sector);
+}
+
+static int blk_log_action(struct trace_iterator *iter, struct blk_io_trace *t,
+			  const char *act)
+{
+	char rwbs[6];
+	unsigned long long ts	= ns2usecs(iter->ts);
+	unsigned long usec_rem	= do_div(ts, USEC_PER_SEC);
+	unsigned secs		= (unsigned long)ts;
+
+	fill_rwbs(rwbs, t);
+	return trace_seq_printf(&iter->seq,
+				"%3d,%-3d %2d %5d.%06lu %5u %2s %3s ",
+				MAJOR(t->device), MINOR(t->device), iter->cpu,
+				secs, usec_rem, t->pid, act, rwbs);
+}
+
+static int blk_log_generic(struct trace_iterator *iter, struct blk_io_trace *t,
+			   const char *act)
+{
+	int ret = blk_log_action(iter, t, act);
+	if (ret) {
+		const char *cmd = trace_find_cmdline(t->pid);
+
+		if (t_sec(t))
+			ret = trace_seq_printf(&iter->seq, "%llu + %u [%s]\n",
+					       (unsigned long long)t->sector,
+					       t_sec(t), cmd);
+		else
+			ret = trace_seq_printf(&iter->seq, "[%s]\n", cmd);
+	}
+	return ret;
+}
+
+static int blk_log_with_err(struct trace_iterator *iter, struct blk_io_trace *t,
+			    const char *act)
+{
+	int ret = blk_log_action(iter, t, act);
+	if (ret) {
+		if (t_sec(t))
+			ret = trace_seq_printf(&iter->seq, "%llu + %u [%d]\n",
+					       (unsigned long long)t->sector,
+					       t_sec(t), t->error);
+		else
+			ret = trace_seq_printf(&iter->seq, "%llu [%d]\n",
+					       (unsigned long long)t->sector,
+					       t->error);
+	}
+	return ret;
+}
+
+static int blk_log_remap(struct trace_iterator *iter, struct blk_io_trace *t)
+{
+	int ret = blk_log_action(iter, t, "A");
+	if (ret) {
+		struct blk_io_trace_remap r = { .device = 0, };
+
+		get_pdu_remap(t, &r);
+		t->device = r.device_from;
+		ret = trace_seq_printf(&iter->seq, "%llu + %u <- (%d,%d) %llu\n",
+				       (unsigned long long)t->sector,
+				       t_sec(t), MAJOR(r.device), MINOR(r.device),
+				       (unsigned long long)r.sector);
+	}
+	return ret;
+}
+
+static int blk_log_plug(struct trace_iterator *iter, struct blk_io_trace *t)
+{
+	int ret = blk_log_action(iter, t, "P");
+	if (ret)
+		ret = trace_seq_printf(&iter->seq, "[%s]\n",
+				       trace_find_cmdline(t->pid));
+	return ret;
+}
+
+static int blk_log_unplug(struct trace_iterator *iter, struct blk_io_trace *t,
+			  const char *act)
+{
+	int ret = blk_log_action(iter, t, act);
+	if (ret)
+		ret = trace_seq_printf(&iter->seq, "[%s] %u\n",
+				       trace_find_cmdline(t->pid),
+				       get_pdu_int(t));
+	return ret;
+}
+
+static int blk_log_split(struct trace_iterator *iter, struct blk_io_trace *t,
+			 const char *act)
+{
+	int ret = blk_log_action(iter, t, act);
+	if (ret)
+		ret = trace_seq_printf(&iter->seq, "%llu / %u [%s]\n",
+				       (unsigned long long)t->sector,
+				       get_pdu_int(t),
+				       trace_find_cmdline(t->pid));
+	return ret;
+}
+
+/*
+ * struct tracer operations
+ */
+
+static void blk_tracer_print_header(struct seq_file *m)
+{
+	seq_puts(m, "# DEV   CPU TIMESTAMP     PID ACT FLG\n"
+		    "#  |     |     |           |   |   |\n");
+}
+
+static enum print_line_t blk_tracer_print_line(struct trace_iterator *iter)
+{
+	struct trace_seq *s = &iter->seq;
+	struct blk_io_trace *t = (struct blk_io_trace *)iter->ent;
+	const u16 what = t->action & ((1 << BLK_TC_SHIFT) - 1);
+	int ret;
+
+	switch (what) {
+	case __BLK_TA_ISSUE:	    ret = blk_log_generic(iter, t, "D"); break;
+	case __BLK_TA_INSERT:	    ret = blk_log_generic(iter, t, "I"); break;
+	case __BLK_TA_QUEUE:	    ret = blk_log_generic(iter, t, "Q"); break;
+	case __BLK_TA_BOUNCE:	    ret = blk_log_generic(iter, t, "B"); break;
+	case __BLK_TA_BACKMERGE:    ret = blk_log_generic(iter, t, "M"); break;
+	case __BLK_TA_FRONTMERGE:   ret = blk_log_generic(iter, t, "F"); break;
+	case __BLK_TA_GETRQ:	    ret = blk_log_generic(iter, t, "G"); break;
+	case __BLK_TA_SLEEPRQ:	    ret = blk_log_generic(iter, t, "S"); break;
+	case __BLK_TA_REQUEUE:	    ret = blk_log_with_err(iter, t, "R"); break;
+	case __BLK_TA_COMPLETE:	    ret = blk_log_with_err(iter, t, "C"); break;
+	case __BLK_TA_PLUG:	    ret = blk_log_plug(iter, t); break;
+	case __BLK_TA_UNPLUG_IO:    ret = blk_log_unplug(iter, t, "U"); break;
+	case __BLK_TA_UNPLUG_TIMER: ret = blk_log_unplug(iter, t, "UT"); break;
+	case __BLK_TA_REMAP:	    ret = blk_log_remap(iter, t); break;
+	case __BLK_TA_SPLIT:	    ret = blk_log_split(iter, t, "X"); break;
+	default:
+		ret = trace_seq_printf(s, "Bad pc action %x\n", what);
+		break;
+	}
+
+	if (ret == 0)
+		return TRACE_TYPE_PARTIAL_LINE;
+
+	return TRACE_TYPE_HANDLED;
+}
+
+static void blk_tracer_start(struct trace_array *tr)
+{
+	int cpu;
+
+	tr->time_start = ftrace_now(tr->cpu);
+
+	for_each_online_cpu(cpu)
+		tracing_reset(tr, cpu);
+
+	mutex_lock(&blk_probe_mutex);
+	if (atomic_add_return(1, &blk_probes_ref) == 1)
+		if (blk_register_tracepoints())
+			atomic_dec(&blk_probes_ref);
+	mutex_unlock(&blk_probe_mutex);
+}
+
+static int blk_tracer_init(struct trace_array *tr)
+{
+	blk_tr = tr;
+	blk_tracer_start(tr);
+	mutex_lock(&blk_probe_mutex);
+	blk_tracer_enabled++;
+	mutex_unlock(&blk_probe_mutex);
+	return 0;
+}
+
+static void blk_tracer_stop(struct trace_array *tr)
+{
+	mutex_lock(&blk_probe_mutex);
+	if (atomic_dec_and_test(&blk_probes_ref))
+		blk_unregister_tracepoints();
+	mutex_unlock(&blk_probe_mutex);
+}
+
+static void blk_tracer_reset(struct trace_array *tr)
+{
+	if (!atomic_read(&blk_probes_ref))
+		return;
+
+	mutex_lock(&blk_probe_mutex);
+	blk_tracer_enabled--;
+	WARN_ON(blk_tracer_enabled < 0);
+	mutex_unlock(&blk_probe_mutex);
+
+	blk_tracer_stop(tr);
+}
+
+static struct tracer blk_tracer __read_mostly = {
+	.name		= "blk",
+	.init		= blk_tracer_init,
+	.reset		= blk_tracer_reset,
+	.start		= blk_tracer_start,
+	.stop		= blk_tracer_stop,
+	.print_header	= blk_tracer_print_header,
+	.print_line	= blk_tracer_print_line,
+};
+
+static int __init init_blk_tracer(void)
+{
+	return register_tracer(&blk_tracer);
+}
+
+device_initcall(init_blk_tracer);
+
+static int blk_trace_remove_queue(struct request_queue *q)
+{
+	struct blk_trace *bt;
+
+	bt = xchg(&q->blk_trace, NULL);
+	if (bt == NULL)
+		return -EINVAL;
+
+	kfree(bt);
+	return 0;
+}
+
+/*
+ * Setup everything required to start tracing
+ */
+static int blk_trace_setup_queue(struct request_queue *q, dev_t dev)
+{
+	struct blk_trace *old_bt, *bt = NULL;
+	int ret;
+
+	ret = -ENOMEM;
+	bt = kzalloc(sizeof(*bt), GFP_KERNEL);
+	if (!bt)
+		goto err;
+
+	bt->dev = dev;
+	bt->act_mask = (u16)-1;
+	bt->end_lba = -1ULL;
+	bt->trace_state = Blktrace_running;
+
+	old_bt = xchg(&q->blk_trace, bt);
+	if (old_bt != NULL) {
+		(void)xchg(&q->blk_trace, old_bt);
+		kfree(bt);
+		ret = -EBUSY;
+	}
+	return 0;
+err:
+	return ret;
+}
+
+/*
+ * sysfs interface to enable and configure tracing
+ */
+
+static ssize_t sysfs_blk_trace_enable_show(struct device *dev,
+					   struct device_attribute *attr,
+					   char *buf)
+{
+	struct hd_struct *p = dev_to_part(dev);
+	struct block_device *bdev;
+	ssize_t ret = -ENXIO;
+
+	lock_kernel();
+	bdev = bdget(part_devt(p));
+	if (bdev != NULL) {
+		struct request_queue *q = bdev_get_queue(bdev);
+
+		if (q != NULL) {
+			mutex_lock(&bdev->bd_mutex);
+			ret = sprintf(buf, "%u\n", !!q->blk_trace);
+			mutex_unlock(&bdev->bd_mutex);
+		}
+
+		bdput(bdev);
+	}
+
+	unlock_kernel();
+	return ret;
+}
+
+static ssize_t sysfs_blk_trace_enable_store(struct device *dev,
+					    struct device_attribute *attr,
+					    const char *buf, size_t count)
+{
+	struct block_device *bdev;
+	struct request_queue *q;
+	struct hd_struct *p;
+	int value;
+	ssize_t ret = -ENXIO;
+
+	if (count == 0 || sscanf(buf, "%d", &value) != 1)
+		goto out;
+
+	lock_kernel();
+	p = dev_to_part(dev);
+	bdev = bdget(part_devt(p));
+	if (bdev == NULL)
+		goto out_unlock_kernel;
+
+	q = bdev_get_queue(bdev);
+	if (q == NULL)
+		goto out_bdput;
+
+	mutex_lock(&bdev->bd_mutex);
+	if (value)
+		ret = blk_trace_setup_queue(q, bdev->bd_dev);
+	else
+		ret = blk_trace_remove_queue(q);
+	mutex_unlock(&bdev->bd_mutex);
+
+	if (ret == 0)
+		ret = count;
+out_bdput:
+	bdput(bdev);
+out_unlock_kernel:
+	unlock_kernel();
+out:
+	return ret;
+}
+
+static ssize_t sysfs_blk_trace_attr_show(struct device *dev,
+					 struct device_attribute *attr,
+					 char *buf);
+static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
+					  struct device_attribute *attr,
+					  const char *buf, size_t count);
+#define BLK_TRACE_DEVICE_ATTR(_name) \
+	DEVICE_ATTR(_name, S_IRUGO | S_IWUSR, \
+		    sysfs_blk_trace_attr_show, \
+		    sysfs_blk_trace_attr_store)
+
+static DEVICE_ATTR(enable, S_IRUGO | S_IWUSR,
+		   sysfs_blk_trace_enable_show, sysfs_blk_trace_enable_store);
+static BLK_TRACE_DEVICE_ATTR(act_mask);
+static BLK_TRACE_DEVICE_ATTR(pid);
+static BLK_TRACE_DEVICE_ATTR(start_lba);
+static BLK_TRACE_DEVICE_ATTR(end_lba);
+
+static struct attribute *blk_trace_attrs[] = {
+	&dev_attr_enable.attr,
+	&dev_attr_act_mask.attr,
+	&dev_attr_pid.attr,
+	&dev_attr_start_lba.attr,
+	&dev_attr_end_lba.attr,
+	NULL
+};
+
+struct attribute_group blk_trace_attr_group = {
+	.name  = "trace",
+	.attrs = blk_trace_attrs,
+};
+
+static int blk_str2act_mask(const char *str)
+{
+	int mask = 0;
+	char *copy = kstrdup(str, GFP_KERNEL), *s;
+
+	if (copy == NULL)
+		return -ENOMEM;
+
+	s = strstrip(copy);
+
+	while (1) {
+		char *sep = strchr(s, ',');
+
+		if (sep != NULL)
+			*sep = '\0';
+
+		if (strcasecmp(s, "barrier") == 0)
+			mask |= BLK_TC_BARRIER;
+		else if (strcasecmp(s, "complete") == 0)
+			mask |= BLK_TC_COMPLETE;
+		else if (strcasecmp(s, "fs") == 0)
+			mask |= BLK_TC_FS;
+		else if (strcasecmp(s, "issue") == 0)
+			mask |= BLK_TC_ISSUE;
+		else if (strcasecmp(s, "pc") == 0)
+			mask |= BLK_TC_PC;
+		else if (strcasecmp(s, "queue") == 0)
+			mask |= BLK_TC_QUEUE;
+		else if (strcasecmp(s, "read") == 0)
+			mask |= BLK_TC_READ;
+		else if (strcasecmp(s, "requeue") == 0)
+			mask |= BLK_TC_REQUEUE;
+		else if (strcasecmp(s, "sync") == 0)
+			mask |= BLK_TC_SYNC;
+		else if (strcasecmp(s, "write") == 0)
+			mask |= BLK_TC_WRITE;
+
+		if (sep == NULL)
+			break;
+
+		s = sep + 1;
+	}
+	kfree(copy);
+
+	return mask;
+}
+
+static ssize_t sysfs_blk_trace_attr_show(struct device *dev,
+					 struct device_attribute *attr,
+					 char *buf)
+{
+	struct hd_struct *p = dev_to_part(dev);
+	struct request_queue *q;
+	struct block_device *bdev;
+	ssize_t ret = -ENXIO;
+
+	lock_kernel();
+	bdev = bdget(part_devt(p));
+	if (bdev == NULL)
+		goto out_unlock_kernel;
+
+	q = bdev_get_queue(bdev);
+	if (q == NULL)
+		goto out_bdput;
+	mutex_lock(&bdev->bd_mutex);
+	if (q->blk_trace == NULL)
+		ret = sprintf(buf, "disabled\n");
+	else if (attr == &dev_attr_act_mask)
+		ret = sprintf(buf, "%#x\n", q->blk_trace->act_mask);
+	else if (attr == &dev_attr_pid)
+		ret = sprintf(buf, "%u\n", q->blk_trace->pid);
+	else if (attr == &dev_attr_start_lba)
+		ret = sprintf(buf, "%llu\n", q->blk_trace->start_lba);
+	else if (attr == &dev_attr_end_lba)
+		ret = sprintf(buf, "%llu\n", q->blk_trace->end_lba);
+	mutex_unlock(&bdev->bd_mutex);
+out_bdput:
+	bdput(bdev);
+out_unlock_kernel:
+	unlock_kernel();
+	return ret;
+}
+
+static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
+					  struct device_attribute *attr,
+					  const char *buf, size_t count)
+{
+	struct block_device *bdev;
+	struct request_queue *q;
+	struct hd_struct *p;
+	u64 value;
+	ssize_t ret = -ENXIO;
+
+	if (count == 0)
+		goto out;
+
+	if (attr == &dev_attr_act_mask) {
+		if (sscanf(buf, "%llx", &value) != 1) {
+			/* Assume it is a list of trace category names */
+			value = blk_str2act_mask(buf);
+			if (value < 0)
+				goto out;
+		}
+	} else if (sscanf(buf, "%llu", &value) != 1)
+		goto out;
+
+	lock_kernel();
+	p = dev_to_part(dev);
+	bdev = bdget(part_devt(p));
+	if (bdev == NULL)
+		goto out_unlock_kernel;
+
+	q = bdev_get_queue(bdev);
+	if (q == NULL)
+		goto out_bdput;
+
+	mutex_lock(&bdev->bd_mutex);
+	ret = 0;
+	if (q->blk_trace == NULL)
+		ret = blk_trace_setup_queue(q, bdev->bd_dev);
+
+	if (ret == 0) {
+		if (attr == &dev_attr_act_mask)
+			q->blk_trace->act_mask = value;
+		else if (attr == &dev_attr_pid)
+			q->blk_trace->pid = value;
+		else if (attr == &dev_attr_start_lba)
+			q->blk_trace->start_lba = value;
+		else if (attr == &dev_attr_end_lba)
+			q->blk_trace->end_lba = value;
+		ret = count;
+	}
+	mutex_unlock(&bdev->bd_mutex);
+out_bdput:
+	bdput(bdev);
+out_unlock_kernel:
+	unlock_kernel();
+out:
+	return ret;
+}
diff --git a/fs/partitions/check.c b/fs/partitions/check.c
index 6d72024..01714ef 100644
--- a/fs/partitions/check.c
+++ b/fs/partitions/check.c
@@ -268,6 +268,10 @@ ssize_t part_fail_store(struct device *dev,
 }
 #endif
 
+#ifdef CONFIG_BLK_DEV_IO_TRACE
+extern struct attribute_group blk_trace_attr_group;
+#endif
+
 static DEVICE_ATTR(partition, S_IRUGO, part_partition_show, NULL);
 static DEVICE_ATTR(start, S_IRUGO, part_start_show, NULL);
 static DEVICE_ATTR(size, S_IRUGO, part_size_show, NULL);
@@ -294,6 +298,9 @@ static struct attribute_group part_attr_group = {
 
 static struct attribute_group *part_attr_groups[] = {
 	&part_attr_group,
+#ifdef CONFIG_BLK_DEV_IO_TRACE
+	&blk_trace_attr_group,
+#endif
 	NULL
 };
 
--
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