/*

   * Copyright (C) 2006 Jens Axboe <axboe@kernel.dk>

   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
   *
   */

  #include <linux/kernel.h>
  #include <linux/blkdev.h>
  #include <linux/blktrace_api.h>
  #include <linux/percpu.h>
  #include <linux/init.h>
  #include <linux/mutex.h>

  #include <linux/slab.h>

  #include <linux/debugfs.h>

  #include <linux/export.h>

  #include <linux/time.h>

  #include <linux/uaccess.h>

  #include <linux/list.h>

  
  #include <trace/events/block.h>

  #include "trace_output.h"

  #ifdef CONFIG_BLK_DEV_IO_TRACE

  static unsigned int blktrace_seq __read_mostly = 1;

  static struct trace_array *blk_tr;

  static bool blk_tracer_enabled __read_mostly;

  static LIST_HEAD(running_trace_list);
  static __cacheline_aligned_in_smp DEFINE_SPINLOCK(running_trace_lock);

  /* Select an alternative, minimalistic output than the original one */

  #define TRACE_BLK_OPT_CLASSIC	0x1

  
  static struct tracer_opt blk_tracer_opts[] = {
  	/* Default disable the minimalistic output */

  	{ TRACER_OPT(blk_classic, TRACE_BLK_OPT_CLASSIC) },

  	{ }
  };
  
  static struct tracer_flags blk_tracer_flags = {
  	.val  = 0,
  	.opts = blk_tracer_opts,
  };

  /* Global reference count of probes */

  static atomic_t blk_probes_ref = ATOMIC_INIT(0);

  static void blk_register_tracepoints(void);

  static void blk_unregister_tracepoints(void);

  /*

   * Send out a notify message.
   */

  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;

  	struct ring_buffer *buffer = NULL;

  	int pc = 0;
  	int cpu = smp_processor_id();
  	bool blk_tracer = blk_tracer_enabled;
  
  	if (blk_tracer) {

  		buffer = blk_tr->trace_buffer.buffer;

  		pc = preempt_count();

  		event = trace_buffer_lock_reserve(buffer, 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) {

  		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(buffer, event, 0, pc);

  	}

  }
  
  /*

   * Send out a notify for this process, if we haven't done so since a trace
   * started
   */

  static void trace_note_tsk(struct task_struct *tsk)

  {

  	unsigned long flags;
  	struct blk_trace *bt;

  	tsk->btrace_seq = blktrace_seq;

  	spin_lock_irqsave(&running_trace_lock, flags);
  	list_for_each_entry(bt, &running_trace_list, running_list) {
  		trace_note(bt, tsk->pid, BLK_TN_PROCESS, tsk->comm,
  			   sizeof(tsk->comm));
  	}
  	spin_unlock_irqrestore(&running_trace_lock, flags);

  }

  static void trace_note_time(struct blk_trace *bt)
  {
  	struct timespec now;
  	unsigned long flags;
  	u32 words[2];
  
  	getnstimeofday(&now);
  	words[0] = now.tv_sec;
  	words[1] = now.tv_nsec;
  
  	local_irq_save(flags);
  	trace_note(bt, 0, BLK_TN_TIMESTAMP, words, sizeof(words));
  	local_irq_restore(flags);

  }

  void __trace_note_message(struct blk_trace *bt, const char *fmt, ...)
  {
  	int n;
  	va_list args;

  	unsigned long flags;

  	char *buf;

  	if (unlikely(bt->trace_state != Blktrace_running &&
  		     !blk_tracer_enabled))

  		return;

  	/*
  	 * If the BLK_TC_NOTIFY action mask isn't set, don't send any note
  	 * message to the trace.
  	 */
  	if (!(bt->act_mask & BLK_TC_NOTIFY))
  		return;

  	local_irq_save(flags);

  	buf = this_cpu_ptr(bt->msg_data);

  	va_start(args, fmt);

  	n = vscnprintf(buf, BLK_TN_MAX_MSG, fmt, args);

  	va_end(args);

  	trace_note(bt, 0, BLK_TN_MESSAGE, buf, n);

  	local_irq_restore(flags);

  }
  EXPORT_SYMBOL_GPL(__trace_note_message);

  static int act_log_check(struct blk_trace *bt, u32 what, sector_t sector,
  			 pid_t pid)
  {
  	if (((bt->act_mask << BLK_TC_SHIFT) & what) == 0)
  		return 1;

  	if (sector && (sector < bt->start_lba || sector > bt->end_lba))

  		return 1;
  	if (bt->pid && pid != bt->pid)
  		return 1;
  
  	return 0;
  }
  
  /*
   * Data direction bit lookup
   */

  static const u32 ddir_act[2] = { BLK_TC_ACT(BLK_TC_READ),
  				 BLK_TC_ACT(BLK_TC_WRITE) };

  #define BLK_TC_RAHEAD		BLK_TC_AHEAD

  /* The ilog2() calls fall out because they're constant */

  #define MASK_TC_BIT(rw, __name) ((rw & REQ_ ## __name) << \
  	  (ilog2(BLK_TC_ ## __name) + BLK_TC_SHIFT - __REQ_ ## __name))

  
  /*
   * The worker for the various blk_add_trace*() types. Fills out a
   * blk_io_trace structure and places it in a per-cpu subbuffer.
   */

  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 ring_buffer *buffer = NULL;

  	struct blk_io_trace *t;

  	unsigned long flags = 0;

  	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))

  		return;
  
  	what |= ddir_act[rw & WRITE];

  	what |= MASK_TC_BIT(rw, SYNC);
  	what |= MASK_TC_BIT(rw, RAHEAD);

  	what |= MASK_TC_BIT(rw, META);
  	what |= MASK_TC_BIT(rw, DISCARD);

  	what |= MASK_TC_BIT(rw, FLUSH);
  	what |= MASK_TC_BIT(rw, FUA);

  
  	pid = tsk->pid;

  	if (act_log_check(bt, what, sector, pid))

  		return;

  	cpu = raw_smp_processor_id();

  	if (blk_tracer) {

  		tracing_record_cmdline(current);

  		buffer = blk_tr->trace_buffer.buffer;

  		pc = preempt_count();

  		event = trace_buffer_lock_reserve(buffer, TRACE_BLK,

  						  sizeof(*t) + pdu_len,
  						  0, pc);

  		if (!event)
  			return;

  		t = ring_buffer_event_data(event);

  		goto record_it;
  	}

  	if (unlikely(tsk->btrace_seq != blktrace_seq))
  		trace_note_tsk(tsk);

  	/*
  	 * A word about the locking here - we disable interrupts to reserve
  	 * some space in the relay per-cpu buffer, to prevent an irq

  	 * from coming in and stepping on our toes.

  	 */
  	local_irq_save(flags);

  	t = relay_reserve(bt->rchan, sizeof(*t) + pdu_len);
  	if (t) {

  		sequence = per_cpu_ptr(bt->sequence, cpu);
  
  		t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
  		t->sequence = ++(*sequence);

  		t->time = ktime_to_ns(ktime_get());

  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;

  		t->device = bt->dev;

  		t->error = error;
  		t->pdu_len = pdu_len;
  
  		if (pdu_len)
  			memcpy((void *) t + sizeof(*t), pdu_data, pdu_len);

  		if (blk_tracer) {

  			trace_buffer_unlock_commit(buffer, event, 0, pc);

  			return;
  		}

  	}
  
  	local_irq_restore(flags);
  }

  static struct dentry *blk_tree_root;

  static DEFINE_MUTEX(blk_tree_mutex);

  static void blk_trace_free(struct blk_trace *bt)

  {

  	debugfs_remove(bt->msg_file);

  	debugfs_remove(bt->dropped_file);

  	relay_close(bt->rchan);

  	debugfs_remove(bt->dir);

  	free_percpu(bt->sequence);

  	free_percpu(bt->msg_data);

  	kfree(bt);

  }
  
  static void blk_trace_cleanup(struct blk_trace *bt)
  {
  	blk_trace_free(bt);

  	if (atomic_dec_and_test(&blk_probes_ref))
  		blk_unregister_tracepoints();

  }

  int blk_trace_remove(struct request_queue *q)

  {
  	struct blk_trace *bt;
  
  	bt = xchg(&q->blk_trace, NULL);
  	if (!bt)
  		return -EINVAL;

  	if (bt->trace_state != Blktrace_running)

  		blk_trace_cleanup(bt);
  
  	return 0;
  }

  EXPORT_SYMBOL_GPL(blk_trace_remove);

  static ssize_t blk_dropped_read(struct file *filp, char __user *buffer,
  				size_t count, loff_t *ppos)
  {
  	struct blk_trace *bt = filp->private_data;
  	char buf[16];
  
  	snprintf(buf, sizeof(buf), "%u
  ", atomic_read(&bt->dropped));
  
  	return simple_read_from_buffer(buffer, count, ppos, buf, strlen(buf));
  }

  static const struct file_operations blk_dropped_fops = {

  	.owner =	THIS_MODULE,

  	.open =		simple_open,

  	.read =		blk_dropped_read,

  	.llseek =	default_llseek,

  };

  static ssize_t blk_msg_write(struct file *filp, const char __user *buffer,
  				size_t count, loff_t *ppos)
  {
  	char *msg;
  	struct blk_trace *bt;

  	if (count >= BLK_TN_MAX_MSG)

  		return -EINVAL;

  	msg = kmalloc(count + 1, GFP_KERNEL);

  	if (msg == NULL)
  		return -ENOMEM;
  
  	if (copy_from_user(msg, buffer, count)) {
  		kfree(msg);
  		return -EFAULT;
  	}

  	msg[count] = '\0';

  	bt = filp->private_data;
  	__trace_note_message(bt, "%s", msg);
  	kfree(msg);
  
  	return count;
  }
  
  static const struct file_operations blk_msg_fops = {
  	.owner =	THIS_MODULE,

  	.open =		simple_open,

  	.write =	blk_msg_write,

  	.llseek =	noop_llseek,

  };

  /*
   * Keep track of how many times we encountered a full subbuffer, to aid
   * the user space app in telling how many lost events there were.
   */
  static int blk_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
  				     void *prev_subbuf, size_t prev_padding)
  {
  	struct blk_trace *bt;
  
  	if (!relay_buf_full(buf))
  		return 1;
  
  	bt = buf->chan->private_data;
  	atomic_inc(&bt->dropped);
  	return 0;
  }
  
  static int blk_remove_buf_file_callback(struct dentry *dentry)
  {
  	debugfs_remove(dentry);

  	return 0;
  }
  
  static struct dentry *blk_create_buf_file_callback(const char *filename,
  						   struct dentry *parent,

  						   umode_t mode,

  						   struct rchan_buf *buf,
  						   int *is_global)
  {
  	return debugfs_create_file(filename, mode, parent, buf,
  					&relay_file_operations);
  }
  
  static struct rchan_callbacks blk_relay_callbacks = {
  	.subbuf_start		= blk_subbuf_start_callback,
  	.create_buf_file	= blk_create_buf_file_callback,
  	.remove_buf_file	= blk_remove_buf_file_callback,
  };

  static void blk_trace_setup_lba(struct blk_trace *bt,
  				struct block_device *bdev)
  {
  	struct hd_struct *part = NULL;
  
  	if (bdev)
  		part = bdev->bd_part;
  
  	if (part) {
  		bt->start_lba = part->start_sect;
  		bt->end_lba = part->start_sect + part->nr_sects;
  	} else {
  		bt->start_lba = 0;
  		bt->end_lba = -1ULL;
  	}
  }

  /*
   * Setup everything required to start tracing
   */

  int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,

  		       struct block_device *bdev,
  		       struct blk_user_trace_setup *buts)

  {

  	struct blk_trace *old_bt, *bt = NULL;
  	struct dentry *dir = NULL;

  	int ret, i;

  	if (!buts->buf_size || !buts->buf_nr)

  		return -EINVAL;

  	strncpy(buts->name, name, BLKTRACE_BDEV_SIZE);
  	buts->name[BLKTRACE_BDEV_SIZE - 1] = '\0';

  
  	/*
  	 * some device names have larger paths - convert the slashes
  	 * to underscores for this to work as expected
  	 */

  	for (i = 0; i < strlen(buts->name); i++)
  		if (buts->name[i] == '/')
  			buts->name[i] = '_';

  	bt = kzalloc(sizeof(*bt), GFP_KERNEL);
  	if (!bt)

  		return -ENOMEM;

  	ret = -ENOMEM;

  	bt->sequence = alloc_percpu(unsigned long);
  	if (!bt->sequence)
  		goto err;

  	bt->msg_data = __alloc_percpu(BLK_TN_MAX_MSG, __alignof__(char));

  	if (!bt->msg_data)
  		goto err;

  	ret = -ENOENT;

  	mutex_lock(&blk_tree_mutex);

  	if (!blk_tree_root) {
  		blk_tree_root = debugfs_create_dir("block", NULL);

  		if (!blk_tree_root) {
  			mutex_unlock(&blk_tree_mutex);

  			goto err;

  		}

  	}

  	mutex_unlock(&blk_tree_mutex);

  
  	dir = debugfs_create_dir(buts->name, blk_tree_root);

  	if (!dir)
  		goto err;
  
  	bt->dir = dir;

  	bt->dev = dev;

  	atomic_set(&bt->dropped, 0);

  	INIT_LIST_HEAD(&bt->running_list);

  
  	ret = -EIO;

  	bt->dropped_file = debugfs_create_file("dropped", 0444, dir, bt,
  					       &blk_dropped_fops);

  	if (!bt->dropped_file)
  		goto err;

  	bt->msg_file = debugfs_create_file("msg", 0222, dir, bt, &blk_msg_fops);
  	if (!bt->msg_file)
  		goto err;

  	bt->rchan = relay_open("trace", dir, buts->buf_size,
  				buts->buf_nr, &blk_relay_callbacks, bt);

  	if (!bt->rchan)
  		goto err;

  	bt->act_mask = buts->act_mask;

  	if (!bt->act_mask)
  		bt->act_mask = (u16) -1;

  	blk_trace_setup_lba(bt, bdev);

  	/* overwrite with user settings */
  	if (buts->start_lba)
  		bt->start_lba = buts->start_lba;
  	if (buts->end_lba)
  		bt->end_lba = buts->end_lba;

  	bt->pid = buts->pid;

  	bt->trace_state = Blktrace_setup;
  
  	ret = -EBUSY;
  	old_bt = xchg(&q->blk_trace, bt);
  	if (old_bt) {
  		(void) xchg(&q->blk_trace, old_bt);
  		goto err;
  	}

  	if (atomic_inc_return(&blk_probes_ref) == 1)

  		blk_register_tracepoints();

  	return 0;
  err:

  	blk_trace_free(bt);

  	return ret;
  }

  int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,

  		    struct block_device *bdev,

  		    char __user *arg)

  {
  	struct blk_user_trace_setup buts;
  	int ret;
  
  	ret = copy_from_user(&buts, arg, sizeof(buts));
  	if (ret)
  		return -EFAULT;

  	ret = do_blk_trace_setup(q, name, dev, bdev, &buts);

  	if (ret)
  		return ret;

  	if (copy_to_user(arg, &buts, sizeof(buts))) {
  		blk_trace_remove(q);

  		return -EFAULT;

  	}

  	return 0;
  }

  EXPORT_SYMBOL_GPL(blk_trace_setup);

  #if defined(CONFIG_COMPAT) && defined(CONFIG_X86_64)
  static int compat_blk_trace_setup(struct request_queue *q, char *name,
  				  dev_t dev, struct block_device *bdev,
  				  char __user *arg)
  {
  	struct blk_user_trace_setup buts;
  	struct compat_blk_user_trace_setup cbuts;
  	int ret;
  
  	if (copy_from_user(&cbuts, arg, sizeof(cbuts)))
  		return -EFAULT;
  
  	buts = (struct blk_user_trace_setup) {
  		.act_mask = cbuts.act_mask,
  		.buf_size = cbuts.buf_size,
  		.buf_nr = cbuts.buf_nr,
  		.start_lba = cbuts.start_lba,
  		.end_lba = cbuts.end_lba,
  		.pid = cbuts.pid,
  	};

  
  	ret = do_blk_trace_setup(q, name, dev, bdev, &buts);
  	if (ret)
  		return ret;

  	if (copy_to_user(arg, &buts.name, ARRAY_SIZE(buts.name))) {

  		blk_trace_remove(q);
  		return -EFAULT;
  	}
  
  	return 0;
  }
  #endif

  int blk_trace_startstop(struct request_queue *q, int start)

  {

  	int ret;

  	struct blk_trace *bt = q->blk_trace;

  	if (bt == NULL)

  		return -EINVAL;
  
  	/*
  	 * For starting a trace, we can transition from a setup or stopped
  	 * trace. For stopping a trace, the state must be running
  	 */
  	ret = -EINVAL;
  	if (start) {
  		if (bt->trace_state == Blktrace_setup ||
  		    bt->trace_state == Blktrace_stopped) {
  			blktrace_seq++;
  			smp_mb();
  			bt->trace_state = Blktrace_running;

  			spin_lock_irq(&running_trace_lock);
  			list_add(&bt->running_list, &running_trace_list);
  			spin_unlock_irq(&running_trace_lock);

  
  			trace_note_time(bt);

  			ret = 0;
  		}
  	} else {
  		if (bt->trace_state == Blktrace_running) {
  			bt->trace_state = Blktrace_stopped;

  			spin_lock_irq(&running_trace_lock);
  			list_del_init(&bt->running_list);
  			spin_unlock_irq(&running_trace_lock);

  			relay_flush(bt->rchan);
  			ret = 0;
  		}
  	}
  
  	return ret;
  }

  EXPORT_SYMBOL_GPL(blk_trace_startstop);

  
  /**
   * blk_trace_ioctl: - handle the ioctls associated with tracing
   * @bdev:	the block device

   * @cmd:	the ioctl cmd

   * @arg:	the argument data, if any
   *
   **/
  int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
  {

  	struct request_queue *q;

  	int ret, start = 0;

  	char b[BDEVNAME_SIZE];

  
  	q = bdev_get_queue(bdev);
  	if (!q)
  		return -ENXIO;
  
  	mutex_lock(&bdev->bd_mutex);
  
  	switch (cmd) {
  	case BLKTRACESETUP:

  		bdevname(bdev, b);

  		ret = blk_trace_setup(q, b, bdev->bd_dev, bdev, arg);

  		break;

  #if defined(CONFIG_COMPAT) && defined(CONFIG_X86_64)
  	case BLKTRACESETUP32:
  		bdevname(bdev, b);
  		ret = compat_blk_trace_setup(q, b, bdev->bd_dev, bdev, arg);
  		break;
  #endif

  	case BLKTRACESTART:
  		start = 1;
  	case BLKTRACESTOP:
  		ret = blk_trace_startstop(q, start);
  		break;
  	case BLKTRACETEARDOWN:
  		ret = blk_trace_remove(q);
  		break;
  	default:
  		ret = -ENOTTY;
  		break;
  	}
  
  	mutex_unlock(&bdev->bd_mutex);
  	return ret;
  }
  
  /**
   * blk_trace_shutdown: - stop and cleanup trace structures
   * @q:    the request queue associated with the device
   *
   **/

  void blk_trace_shutdown(struct request_queue *q)

  {

  	if (q->blk_trace) {
  		blk_trace_startstop(q, 0);
  		blk_trace_remove(q);
  	}

  }

  
  /*
   * blktrace probes
   */
  
  /**
   * blk_add_trace_rq - Add a trace for a request oriented action
   * @q:		queue the io is for
   * @rq:		the source request

   * @nr_bytes:	number of completed bytes

   * @what:	the action
   *
   * Description:
   *     Records an action against a request. Will log the bio offset + size.
   *
   **/
  static void blk_add_trace_rq(struct request_queue *q, struct request *rq,

  			     unsigned int nr_bytes, u32 what)

  {
  	struct blk_trace *bt = q->blk_trace;

  
  	if (likely(!bt))
  		return;

  	if (rq->cmd_type == REQ_TYPE_BLOCK_PC) {

  		what |= BLK_TC_ACT(BLK_TC_PC);

  		__blk_add_trace(bt, 0, nr_bytes, rq->cmd_flags,

  				what, rq->errors, rq->cmd_len, rq->cmd);

  	} else  {
  		what |= BLK_TC_ACT(BLK_TC_FS);

  		__blk_add_trace(bt, blk_rq_pos(rq), nr_bytes,

  				rq->cmd_flags, what, rq->errors, 0, NULL);

  	}
  }

  static void blk_add_trace_rq_abort(void *ignore,
  				   struct request_queue *q, struct request *rq)

  {

  	blk_add_trace_rq(q, rq, blk_rq_bytes(rq), BLK_TA_ABORT);

  }

  static void blk_add_trace_rq_insert(void *ignore,
  				    struct request_queue *q, struct request *rq)

  {

  	blk_add_trace_rq(q, rq, blk_rq_bytes(rq), BLK_TA_INSERT);

  }

  static void blk_add_trace_rq_issue(void *ignore,
  				   struct request_queue *q, struct request *rq)

  {

  	blk_add_trace_rq(q, rq, blk_rq_bytes(rq), BLK_TA_ISSUE);

  }

  static void blk_add_trace_rq_requeue(void *ignore,
  				     struct request_queue *q,

  				     struct request *rq)

  {

  	blk_add_trace_rq(q, rq, blk_rq_bytes(rq), BLK_TA_REQUEUE);

  }

  static void blk_add_trace_rq_complete(void *ignore,
  				      struct request_queue *q,

  				      struct request *rq,
  				      unsigned int nr_bytes)

  {

  	blk_add_trace_rq(q, rq, nr_bytes, BLK_TA_COMPLETE);

  }
  
  /**
   * blk_add_trace_bio - Add a trace for a bio oriented action
   * @q:		queue the io is for
   * @bio:	the source bio
   * @what:	the action

   * @error:	error, if any

   *
   * Description:
   *     Records an action against a bio. Will log the bio offset + size.
   *
   **/
  static void blk_add_trace_bio(struct request_queue *q, struct bio *bio,

  			      u32 what, int error)

  {
  	struct blk_trace *bt = q->blk_trace;
  
  	if (likely(!bt))
  		return;

  	if (!error && !bio_flagged(bio, BIO_UPTODATE))
  		error = EIO;

  	__blk_add_trace(bt, bio->bi_iter.bi_sector, bio->bi_iter.bi_size,
  			bio->bi_rw, what, error, 0, NULL);

  }

  static void blk_add_trace_bio_bounce(void *ignore,
  				     struct request_queue *q, struct bio *bio)

  {

  	blk_add_trace_bio(q, bio, BLK_TA_BOUNCE, 0);

  }

  static void blk_add_trace_bio_complete(void *ignore,
  				       struct request_queue *q, struct bio *bio,
  				       int error)

  {

  	blk_add_trace_bio(q, bio, BLK_TA_COMPLETE, error);

  }

  static void blk_add_trace_bio_backmerge(void *ignore,
  					struct request_queue *q,

  					struct request *rq,

  					struct bio *bio)

  {

  	blk_add_trace_bio(q, bio, BLK_TA_BACKMERGE, 0);

  }

  static void blk_add_trace_bio_frontmerge(void *ignore,
  					 struct request_queue *q,

  					 struct request *rq,

  					 struct bio *bio)

  {

  	blk_add_trace_bio(q, bio, BLK_TA_FRONTMERGE, 0);

  }

  static void blk_add_trace_bio_queue(void *ignore,
  				    struct request_queue *q, struct bio *bio)

  {

  	blk_add_trace_bio(q, bio, BLK_TA_QUEUE, 0);

  }

  static void blk_add_trace_getrq(void *ignore,
  				struct request_queue *q,

  				struct bio *bio, int rw)

  {
  	if (bio)

  		blk_add_trace_bio(q, bio, BLK_TA_GETRQ, 0);

  	else {
  		struct blk_trace *bt = q->blk_trace;
  
  		if (bt)
  			__blk_add_trace(bt, 0, 0, rw, BLK_TA_GETRQ, 0, 0, NULL);
  	}
  }

  static void blk_add_trace_sleeprq(void *ignore,
  				  struct request_queue *q,

  				  struct bio *bio, int rw)

  {
  	if (bio)

  		blk_add_trace_bio(q, bio, BLK_TA_SLEEPRQ, 0);

  	else {
  		struct blk_trace *bt = q->blk_trace;
  
  		if (bt)

  			__blk_add_trace(bt, 0, 0, rw, BLK_TA_SLEEPRQ,
  					0, 0, NULL);

  	}
  }

  static void blk_add_trace_plug(void *ignore, struct request_queue *q)

  {
  	struct blk_trace *bt = q->blk_trace;
  
  	if (bt)
  		__blk_add_trace(bt, 0, 0, 0, BLK_TA_PLUG, 0, 0, NULL);
  }

  static void blk_add_trace_unplug(void *ignore, struct request_queue *q,
  				    unsigned int depth, bool explicit)

  {
  	struct blk_trace *bt = q->blk_trace;
  
  	if (bt) {

  		__be64 rpdu = cpu_to_be64(depth);

  		u32 what;

  		if (explicit)
  			what = BLK_TA_UNPLUG_IO;
  		else
  			what = BLK_TA_UNPLUG_TIMER;
  
  		__blk_add_trace(bt, 0, 0, 0, what, 0, sizeof(rpdu), &rpdu);

  	}
  }

  static void blk_add_trace_split(void *ignore,
  				struct request_queue *q, struct bio *bio,

  				unsigned int pdu)
  {
  	struct blk_trace *bt = q->blk_trace;
  
  	if (bt) {
  		__be64 rpdu = cpu_to_be64(pdu);

  		__blk_add_trace(bt, bio->bi_iter.bi_sector,
  				bio->bi_iter.bi_size, bio->bi_rw, BLK_TA_SPLIT,
  				!bio_flagged(bio, BIO_UPTODATE),

  				sizeof(rpdu), &rpdu);
  	}
  }
  
  /**

   * blk_add_trace_bio_remap - Add a trace for a bio-remap operation

   * @ignore:	trace callback data parameter (not used)

   * @q:		queue the io is for
   * @bio:	the source bio
   * @dev:	target device

   * @from:	source sector

   *
   * Description:
   *     Device mapper or raid target sometimes need to split a bio because
   *     it spans a stripe (or similar). Add a trace for that action.
   *
   **/

  static void blk_add_trace_bio_remap(void *ignore,
  				    struct request_queue *q, struct bio *bio,
  				    dev_t dev, sector_t from)

  {
  	struct blk_trace *bt = q->blk_trace;
  	struct blk_io_trace_remap r;
  
  	if (likely(!bt))
  		return;

  	r.device_from = cpu_to_be32(dev);
  	r.device_to   = cpu_to_be32(bio->bi_bdev->bd_dev);
  	r.sector_from = cpu_to_be64(from);

  	__blk_add_trace(bt, bio->bi_iter.bi_sector, bio->bi_iter.bi_size,
  			bio->bi_rw, BLK_TA_REMAP,
  			!bio_flagged(bio, BIO_UPTODATE), sizeof(r), &r);

  }
  
  /**

   * blk_add_trace_rq_remap - Add a trace for a request-remap operation

   * @ignore:	trace callback data parameter (not used)

   * @q:		queue the io is for
   * @rq:		the source request
   * @dev:	target device
   * @from:	source sector
   *
   * Description:
   *     Device mapper remaps request to other devices.
   *     Add a trace for that action.
   *
   **/

  static void blk_add_trace_rq_remap(void *ignore,
  				   struct request_queue *q,

  				   struct request *rq, dev_t dev,
  				   sector_t from)
  {
  	struct blk_trace *bt = q->blk_trace;
  	struct blk_io_trace_remap r;
  
  	if (likely(!bt))
  		return;
  
  	r.device_from = cpu_to_be32(dev);
  	r.device_to   = cpu_to_be32(disk_devt(rq->rq_disk));
  	r.sector_from = cpu_to_be64(from);
  
  	__blk_add_trace(bt, blk_rq_pos(rq), blk_rq_bytes(rq),
  			rq_data_dir(rq), BLK_TA_REMAP, !!rq->errors,
  			sizeof(r), &r);
  }
  
  /**

   * blk_add_driver_data - Add binary message with driver-specific data
   * @q:		queue the io is for
   * @rq:		io request
   * @data:	driver-specific data
   * @len:	length of driver-specific data
   *
   * Description:
   *     Some drivers might want to write driver-specific data per request.
   *
   **/
  void blk_add_driver_data(struct request_queue *q,
  			 struct request *rq,
  			 void *data, size_t len)
  {
  	struct blk_trace *bt = q->blk_trace;
  
  	if (likely(!bt))
  		return;

  	if (rq->cmd_type == REQ_TYPE_BLOCK_PC)

  		__blk_add_trace(bt, 0, blk_rq_bytes(rq), 0,
  				BLK_TA_DRV_DATA, rq->errors, len, data);

  	else

  		__blk_add_trace(bt, blk_rq_pos(rq), blk_rq_bytes(rq), 0,
  				BLK_TA_DRV_DATA, rq->errors, len, data);

  }
  EXPORT_SYMBOL_GPL(blk_add_driver_data);

  static void blk_register_tracepoints(void)

  {
  	int ret;

  	ret = register_trace_block_rq_abort(blk_add_trace_rq_abort, NULL);

  	WARN_ON(ret);

  	ret = register_trace_block_rq_insert(blk_add_trace_rq_insert, NULL);

  	WARN_ON(ret);

  	ret = register_trace_block_rq_issue(blk_add_trace_rq_issue, NULL);

  	WARN_ON(ret);

  	ret = register_trace_block_rq_requeue(blk_add_trace_rq_requeue, NULL);

  	WARN_ON(ret);

  	ret = register_trace_block_rq_complete(blk_add_trace_rq_complete, NULL);

  	WARN_ON(ret);

  	ret = register_trace_block_bio_bounce(blk_add_trace_bio_bounce, NULL);

  	WARN_ON(ret);

  	ret = register_trace_block_bio_complete(blk_add_trace_bio_complete, NULL);

  	WARN_ON(ret);

  	ret = register_trace_block_bio_backmerge(blk_add_trace_bio_backmerge, NULL);

  	WARN_ON(ret);

  	ret = register_trace_block_bio_frontmerge(blk_add_trace_bio_frontmerge, NULL);

  	WARN_ON(ret);

  	ret = register_trace_block_bio_queue(blk_add_trace_bio_queue, NULL);

  	WARN_ON(ret);

  	ret = register_trace_block_getrq(blk_add_trace_getrq, NULL);

  	WARN_ON(ret);

  	ret = register_trace_block_sleeprq(blk_add_trace_sleeprq, NULL);

  	WARN_ON(ret);

  	ret = register_trace_block_plug(blk_add_trace_plug, NULL);

  	WARN_ON(ret);

  	ret = register_trace_block_unplug(blk_add_trace_unplug, NULL);

  	WARN_ON(ret);

  	ret = register_trace_block_split(blk_add_trace_split, NULL);

  	WARN_ON(ret);

  	ret = register_trace_block_bio_remap(blk_add_trace_bio_remap, NULL);

  	WARN_ON(ret);

  	ret = register_trace_block_rq_remap(blk_add_trace_rq_remap, NULL);

  	WARN_ON(ret);

  }
  
  static void blk_unregister_tracepoints(void)
  {

  	unregister_trace_block_rq_remap(blk_add_trace_rq_remap, NULL);

  	unregister_trace_block_bio_remap(blk_add_trace_bio_remap, NULL);

  	unregister_trace_block_split(blk_add_trace_split, NULL);

  	unregister_trace_block_unplug(blk_add_trace_unplug, NULL);

  	unregister_trace_block_plug(blk_add_trace_plug, NULL);
  	unregister_trace_block_sleeprq(blk_add_trace_sleeprq, NULL);
  	unregister_trace_block_getrq(blk_add_trace_getrq, NULL);
  	unregister_trace_block_bio_queue(blk_add_trace_bio_queue, NULL);
  	unregister_trace_block_bio_frontmerge(blk_add_trace_bio_frontmerge, NULL);
  	unregister_trace_block_bio_backmerge(blk_add_trace_bio_backmerge, NULL);
  	unregister_trace_block_bio_complete(blk_add_trace_bio_complete, NULL);
  	unregister_trace_block_bio_bounce(blk_add_trace_bio_bounce, NULL);
  	unregister_trace_block_rq_complete(blk_add_trace_rq_complete, NULL);
  	unregister_trace_block_rq_requeue(blk_add_trace_rq_requeue, NULL);
  	unregister_trace_block_rq_issue(blk_add_trace_rq_issue, NULL);
  	unregister_trace_block_rq_insert(blk_add_trace_rq_insert, NULL);
  	unregister_trace_block_rq_abort(blk_add_trace_rq_abort, NULL);

  
  	tracepoint_synchronize_unregister();
  }

  
  /*
   * struct blk_io_tracer formatting routines
   */
  
  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_FLUSH)
  		rwbs[i++] = 'F';

  	if (tc & BLK_TC_DISCARD)

  		rwbs[i++] = 'D';

  	else if (tc & BLK_TC_WRITE)

  		rwbs[i++] = 'W';
  	else if (t->bytes)
  		rwbs[i++] = 'R';
  	else
  		rwbs[i++] = 'N';

  	if (tc & BLK_TC_FUA)
  		rwbs[i++] = 'F';

  	if (tc & BLK_TC_AHEAD)

  		rwbs[i++] = 'A';

  	if (tc & BLK_TC_SYNC)

  		rwbs[i++] = 'S';

  	if (tc & BLK_TC_META)

  		rwbs[i++] = 'M';

  out:

  	rwbs[i] = '\0';

  }
  
  static inline
  const struct blk_io_trace *te_blk_io_trace(const struct trace_entry *ent)
  {
  	return (const struct blk_io_trace *)ent;
  }
  
  static inline const void *pdu_start(const struct trace_entry *ent)
  {
  	return te_blk_io_trace(ent) + 1;
  }

  static inline u32 t_action(const struct trace_entry *ent)
  {
  	return te_blk_io_trace(ent)->action;
  }
  
  static inline u32 t_bytes(const struct trace_entry *ent)
  {
  	return te_blk_io_trace(ent)->bytes;
  }

  static inline u32 t_sec(const struct trace_entry *ent)
  {
  	return te_blk_io_trace(ent)->bytes >> 9;
  }
  
  static inline unsigned long long t_sector(const struct trace_entry *ent)
  {
  	return te_blk_io_trace(ent)->sector;
  }
  
  static inline __u16 t_error(const struct trace_entry *ent)
  {

  	return te_blk_io_trace(ent)->error;

  }
  
  static __u64 get_pdu_int(const struct trace_entry *ent)
  {
  	const __u64 *val = pdu_start(ent);
  	return be64_to_cpu(*val);
  }
  
  static void get_pdu_remap(const struct trace_entry *ent,
  			  struct blk_io_trace_remap *r)
  {
  	const struct blk_io_trace_remap *__r = pdu_start(ent);

  	__u64 sector_from = __r->sector_from;

  	r->device_from = be32_to_cpu(__r->device_from);

  	r->device_to   = be32_to_cpu(__r->device_to);
  	r->sector_from = be64_to_cpu(sector_from);

  }

  typedef void (blk_log_action_t) (struct trace_iterator *iter, const char *act);

  static void blk_log_action_classic(struct trace_iterator *iter, const char *act)

  {

  	char rwbs[RWBS_LEN];

  	unsigned long long ts  = iter->ts;
  	unsigned long nsec_rem = do_div(ts, NSEC_PER_SEC);

  	unsigned secs	       = (unsigned long)ts;

  	const struct blk_io_trace *t = te_blk_io_trace(iter->ent);

  
  	fill_rwbs(rwbs, t);

  	trace_seq_printf(&iter->seq,
  			 "%3d,%-3d %2d %5d.%09lu %5u %2s %3s ",
  			 MAJOR(t->device), MINOR(t->device), iter->cpu,
  			 secs, nsec_rem, iter->ent->pid, act, rwbs);

  }

  static void blk_log_action(struct trace_iterator *iter, const char *act)

  {

  	char rwbs[RWBS_LEN];

  	const struct blk_io_trace *t = te_blk_io_trace(iter->ent);

  	fill_rwbs(rwbs, t);

  	trace_seq_printf(&iter->seq, "%3d,%-3d %2s %3s ",
  			 MAJOR(t->device), MINOR(t->device), act, rwbs);

  }

  static void blk_log_dump_pdu(struct trace_seq *s, const struct trace_entry *ent)

  {

  	const unsigned char *pdu_buf;

  	int pdu_len;

  	int i, end;

  
  	pdu_buf = pdu_start(ent);
  	pdu_len = te_blk_io_trace(ent)->pdu_len;
  
  	if (!pdu_len)

  		return;

  
  	/* find the last zero that needs to be printed */
  	for (end = pdu_len - 1; end >= 0; end--)
  		if (pdu_buf[end])
  			break;
  	end++;

  	trace_seq_putc(s, '(');

  
  	for (i = 0; i < pdu_len; i++) {

  		trace_seq_printf(s, "%s%02x",
  				 i == 0 ? "" : " ", pdu_buf[i]);

  
  		/*
  		 * stop when the rest is just zeroes and indicate so
  		 * with a ".." appended
  		 */

  		if (i == end && end != pdu_len - 1) {
  			trace_seq_puts(s, " ..) ");
  			return;
  		}

  	}

  	trace_seq_puts(s, ") ");

  }

  static void blk_log_generic(struct trace_seq *s, const struct trace_entry *ent)

  {

  	char cmd[TASK_COMM_LEN];
  
  	trace_find_cmdline(ent->pid, cmd);

  	if (t_action(ent) & BLK_TC_ACT(BLK_TC_PC)) {

  		trace_seq_printf(s, "%u ", t_bytes(ent));
  		blk_log_dump_pdu(s, ent);
  		trace_seq_printf(s, "[%s]
  ", cmd);

  	} else {
  		if (t_sec(ent))

  			trace_seq_printf(s, "%llu + %u [%s]
  ",

  						t_sector(ent), t_sec(ent), cmd);

  		else
  			trace_seq_printf(s, "[%s]
  ", cmd);

  	}

  }

  static void blk_log_with_error(struct trace_seq *s,

  			      const struct trace_entry *ent)

  {

  	if (t_action(ent) & BLK_TC_ACT(BLK_TC_PC)) {

  		blk_log_dump_pdu(s, ent);
  		trace_seq_printf(s, "[%d]
  ", t_error(ent));

  	} else {
  		if (t_sec(ent))

  			trace_seq_printf(s, "%llu + %u [%d]
  ",
  					 t_sector(ent),
  					 t_sec(ent), t_error(ent));
  		else
  			trace_seq_printf(s, "%llu [%d]
  ",
  					 t_sector(ent), t_error(ent));

  	}

  }

  static void blk_log_remap(struct trace_seq *s, const struct trace_entry *ent)

  {

  	struct blk_io_trace_remap r = { .device_from = 0, };

  
  	get_pdu_remap(ent, &r);

  	trace_seq_printf(s, "%llu + %u <- (%d,%d) %llu
  ",
  			 t_sector(ent), t_sec(ent),
  			 MAJOR(r.device_from), MINOR(r.device_from),
  			 (unsigned long long)r.sector_from);

  }

  static void blk_log_plug(struct trace_seq *s, const struct trace_entry *ent)

  {

  	char cmd[TASK_COMM_LEN];
  
  	trace_find_cmdline(ent->pid, cmd);

  	trace_seq_printf(s, "[%s]
  ", cmd);

  }

  static void blk_log_unplug(struct trace_seq *s, const struct trace_entry *ent)

  {

  	char cmd[TASK_COMM_LEN];
  
  	trace_find_cmdline(ent->pid, cmd);

  	trace_seq_printf(s, "[%s] %llu
  ", cmd, get_pdu_int(ent));

  }

  static void blk_log_split(struct trace_seq *s, const struct trace_entry *ent)

  {

  	char cmd[TASK_COMM_LEN];
  
  	trace_find_cmdline(ent->pid, cmd);

  	trace_seq_printf(s, "%llu / %llu [%s]
  ", t_sector(ent),
  			 get_pdu_int(ent), cmd);

  }

  static void blk_log_msg(struct trace_seq *s, const struct trace_entry *ent)

  {

  	const struct blk_io_trace *t = te_blk_io_trace(ent);

  	trace_seq_putmem(s, t + 1, t->pdu_len);
  	trace_seq_putc(s, '
  ');

  }

  /*
   * struct tracer operations
   */
  
  static void blk_tracer_print_header(struct seq_file *m)
  {
  	if (!(blk_tracer_flags.val & TRACE_BLK_OPT_CLASSIC))
  		return;
  	seq_puts(m, "# DEV   CPU TIMESTAMP     PID ACT FLG
  "
  		    "#  |     |     |           |   |   |
  ");
  }
  
  static void blk_tracer_start(struct trace_array *tr)
  {

  	blk_tracer_enabled = true;

  }
  
  static int blk_tracer_init(struct trace_array *tr)
  {
  	blk_tr = tr;
  	blk_tracer_start(tr);

  	return 0;
  }
  
  static void blk_tracer_stop(struct trace_array *tr)
  {

  	blk_tracer_enabled = false;

  }
  
  static void blk_tracer_reset(struct trace_array *tr)
  {

  	blk_tracer_stop(tr);
  }

  static const struct {

  	const char *act[2];

  	void	   (*print)(struct trace_seq *s, const struct trace_entry *ent);

  } what2act[] = {

  	[__BLK_TA_QUEUE]	= {{  "Q", "queue" },	   blk_log_generic },

  	[__BLK_TA_BACKMERGE]	= {{  "M", "backmerge" },  blk_log_generic },
  	[__BLK_TA_FRONTMERGE]	= {{  "F", "frontmerge" }, blk_log_generic },
  	[__BLK_TA_GETRQ]	= {{  "G", "getrq" },	   blk_log_generic },
  	[__BLK_TA_SLEEPRQ]	= {{  "S", "sleeprq" },	   blk_log_generic },
  	[__BLK_TA_REQUEUE]	= {{  "R", "requeue" },	   blk_log_with_error },
  	[__BLK_TA_ISSUE]	= {{  "D", "issue" },	   blk_log_generic },
  	[__BLK_TA_COMPLETE]	= {{  "C", "complete" },   blk_log_with_error },
  	[__BLK_TA_PLUG]		= {{  "P", "plug" },	   blk_log_plug },
  	[__BLK_TA_UNPLUG_IO]	= {{  "U", "unplug_io" },  blk_log_unplug },

  	[__BLK_TA_UNPLUG_TIMER]	= {{ "UT", "unplug_timer" }, blk_log_unplug },

  	[__BLK_TA_INSERT]	= {{  "I", "insert" },	   blk_log_generic },
  	[__BLK_TA_SPLIT]	= {{  "X", "split" },	   blk_log_split },
  	[__BLK_TA_BOUNCE]	= {{  "B", "bounce" },	   blk_log_generic },
  	[__BLK_TA_REMAP]	= {{  "A", "remap" },	   blk_log_remap },
  };

  static enum print_line_t print_one_line(struct trace_iterator *iter,
  					bool classic)

  {

  	struct trace_seq *s = &iter->seq;

  	const struct blk_io_trace *t;
  	u16 what;

  	bool long_act;
  	blk_log_action_t *log_action;

  	t	   = te_blk_io_trace(iter->ent);
  	what	   = t->action & ((1 << BLK_TC_SHIFT) - 1);
  	long_act   = !!(trace_flags & TRACE_ITER_VERBOSE);
  	log_action = classic ? &blk_log_action_classic : &blk_log_action;

  	if (t->action == BLK_TN_MESSAGE) {

  		log_action(iter, long_act ? "message" : "m");
  		blk_log_msg(s, iter->ent);

  	}

  	if (unlikely(what == 0 || what >= ARRAY_SIZE(what2act)))

  		trace_seq_printf(s, "Unknown action %x
  ", what);

  	else {

  		log_action(iter, what2act[what].act[long_act]);
  		what2act[what].print(s, iter->ent);

  	}

  
  	return trace_handle_return(s);

  }

  static enum print_line_t blk_trace_event_print(struct trace_iterator *iter,

  					       int flags, struct trace_event *event)

  {

  	return print_one_line(iter, false);
  }

  static void 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     = iter->ts,

  	};

  	trace_seq_putmem(s, &old, offset);
  	trace_seq_putmem(s, &t->sector,
  			 sizeof(old) - offset + t->pdu_len);

  }

  static enum print_line_t

  blk_trace_event_print_binary(struct trace_iterator *iter, int flags,
  			     struct trace_event *event)

  {

  	blk_trace_synthesize_old_trace(iter);
  
  	return trace_handle_return(&iter->seq);

  }

  static enum print_line_t blk_tracer_print_line(struct trace_iterator *iter)
  {

  	if (!(blk_tracer_flags.val & TRACE_BLK_OPT_CLASSIC))
  		return TRACE_TYPE_UNHANDLED;

  	return print_one_line(iter, true);

  }

  static int
  blk_tracer_set_flag(struct trace_array *tr, 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,
  	.reset		= blk_tracer_reset,
  	.start		= blk_tracer_start,
  	.stop		= blk_tracer_stop,
  	.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_functions trace_blk_event_funcs = {

  	.trace		= blk_trace_event_print,

  	.binary		= blk_trace_event_print_binary,

  };

  static struct trace_event trace_blk_event = {
  	.type		= TRACE_BLK,
  	.funcs		= &trace_blk_event_funcs,
  };

  static int __init init_blk_tracer(void)
  {
  	if (!register_ftrace_event(&trace_blk_event)) {
  		pr_warning("Warning: could not register block events
  ");
  		return 1;
  	}
  
  	if (register_tracer(&blk_tracer) != 0) {
  		pr_warning("Warning: could not register the block tracer
  ");
  		unregister_ftrace_event(&trace_blk_event);
  		return 1;
  	}
  
  	return 0;
  }
  
  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;

  	if (atomic_dec_and_test(&blk_probes_ref))
  		blk_unregister_tracepoints();

  	blk_trace_free(bt);

  	return 0;
  }
  
  /*
   * Setup everything required to start tracing
   */

  static int blk_trace_setup_queue(struct request_queue *q,
  				 struct block_device *bdev)

  {
  	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 = bdev->bd_dev;

  	bt->act_mask = (u16)-1;

  
  	blk_trace_setup_lba(bt, bdev);

  
  	old_bt = xchg(&q->blk_trace, bt);
  	if (old_bt != NULL) {
  		(void)xchg(&q->blk_trace, old_bt);

  		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;

  }
  
  /*
   * sysfs interface to enable and configure tracing
   */

  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 BLK_TRACE_DEVICE_ATTR(enable);

  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 const struct {
  	int mask;
  	const char *str;
  } mask_maps[] = {
  	{ BLK_TC_READ,		"read"		},
  	{ BLK_TC_WRITE,		"write"		},

  	{ BLK_TC_FLUSH,		"flush"		},

  	{ BLK_TC_SYNC,		"sync"		},
  	{ BLK_TC_QUEUE,		"queue"		},
  	{ BLK_TC_REQUEUE,	"requeue"	},
  	{ BLK_TC_ISSUE,		"issue"		},
  	{ BLK_TC_COMPLETE,	"complete"	},
  	{ BLK_TC_FS,		"fs"		},
  	{ BLK_TC_PC,		"pc"		},
  	{ BLK_TC_AHEAD,		"ahead"		},
  	{ BLK_TC_META,		"meta"		},
  	{ BLK_TC_DISCARD,	"discard"	},
  	{ BLK_TC_DRV_DATA,	"drv_data"	},

  	{ BLK_TC_FUA,		"fua"		},

  };
  
  static int blk_trace_str2mask(const char *str)

  {

  	int i;

  	int mask = 0;

  	char *buf, *s, *token;

  	buf = kstrdup(str, GFP_KERNEL);
  	if (buf == NULL)

  		return -ENOMEM;

  	s = strstrip(buf);

  
  	while (1) {

  		token = strsep(&s, ",");
  		if (token == NULL)

  			break;

  		if (*token == '\0')
  			continue;
  
  		for (i = 0; i < ARRAY_SIZE(mask_maps); i++) {
  			if (strcasecmp(token, mask_maps[i].str) == 0) {
  				mask |= mask_maps[i].mask;
  				break;
  			}
  		}
  		if (i == ARRAY_SIZE(mask_maps)) {
  			mask = -EINVAL;
  			break;
  		}

  	}

  	kfree(buf);

  
  	return mask;
  }

  static ssize_t blk_trace_mask2str(char *buf, int mask)
  {
  	int i;
  	char *p = buf;
  
  	for (i = 0; i < ARRAY_SIZE(mask_maps); i++) {
  		if (mask & mask_maps[i].mask) {
  			p += sprintf(p, "%s%s",
  				    (p == buf) ? "" : ",", mask_maps[i].str);
  		}
  	}
  	*p++ = '
  ';
  
  	return p - buf;
  }

  static struct request_queue *blk_trace_get_queue(struct block_device *bdev)
  {
  	if (bdev->bd_disk == NULL)
  		return NULL;
  
  	return bdev_get_queue(bdev);
  }

  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;

  	bdev = bdget(part_devt(p));
  	if (bdev == NULL)

  		goto out;

  	q = blk_trace_get_queue(bdev);

  	if (q == NULL)
  		goto out_bdput;

  	mutex_lock(&bdev->bd_mutex);

  
  	if (attr == &dev_attr_enable) {
  		ret = sprintf(buf, "%u
  ", !!q->blk_trace);
  		goto out_unlock_bdev;
  	}

  	if (q->blk_trace == NULL)
  		ret = sprintf(buf, "disabled
  ");
  	else if (attr == &dev_attr_act_mask)