// SPDX-License-Identifier: GPL-2.0

  /*

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

   *

   */

  #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 <linux/blk-cgroup.h>

  #include "../../block/blk.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

  #define TRACE_BLK_OPT_CGROUP	0x2

  #define TRACE_BLK_OPT_CGNAME	0x4

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

  	{ TRACER_OPT(blk_classic, TRACE_BLK_OPT_CLASSIC) },

  #ifdef CONFIG_BLK_CGROUP
  	{ TRACER_OPT(blk_cgroup, TRACE_BLK_OPT_CGROUP) },

  	{ TRACER_OPT(blk_cgname, TRACE_BLK_OPT_CGNAME) },

  #endif

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

  /* Global reference count of probes */

  static DEFINE_MUTEX(blk_probe_mutex);
  static int blk_probes_ref;

  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,
  		       union kernfs_node_id *cgid)

  {
  	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;

  	ssize_t cgid_len = cgid ? sizeof(*cgid) : 0;

  
  	if (blk_tracer) {

  		buffer = blk_tr->trace_buffer.buffer;

  		pc = preempt_count();

  		event = trace_buffer_lock_reserve(buffer, TRACE_BLK,

  						  sizeof(*t) + len + cgid_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 + cgid_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 | (cgid ? __BLK_TN_CGROUP : 0);

  		t->pid = pid;
  		t->cpu = cpu;

  		t->pdu_len = len + cgid_len;
  		if (cgid)
  			memcpy((void *)t + sizeof(*t), cgid, cgid_len);
  		memcpy((void *) t + sizeof(*t) + cgid_len, data, len);

  
  		if (blk_tracer)

  			trace_buffer_unlock_commit(blk_tr, 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), NULL);

  	}
  	spin_unlock_irqrestore(&running_trace_lock, flags);

  }

  static void trace_note_time(struct blk_trace *bt)
  {

  	struct timespec64 now;

  	unsigned long flags;
  	u32 words[2];

  	/* need to check user space to see if this breaks in y2038 or y2106 */
  	ktime_get_real_ts64(&now);
  	words[0] = (u32)now.tv_sec;

  	words[1] = now.tv_nsec;
  
  	local_irq_save(flags);

  	trace_note(bt, 0, BLK_TN_TIMESTAMP, words, sizeof(words), NULL);

  	local_irq_restore(flags);

  }

  void __trace_note_message(struct blk_trace *bt, struct blkcg *blkcg,
  	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);

  	if (!(blk_tracer_flags.val & TRACE_BLK_OPT_CGROUP))
  		blkcg = NULL;
  #ifdef CONFIG_BLK_CGROUP
  	trace_note(bt, 0, BLK_TN_MESSAGE, buf, n,
  		blkcg ? cgroup_get_kernfs_id(blkcg->css.cgroup) : NULL);
  #else

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

  #endif

  	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

  #define BLK_TC_PREFLUSH		BLK_TC_FLUSH

  /* 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 op, int op_flags, u32 what, int error, int pdu_len,

  		     void *pdu_data, union kernfs_node_id *cgid)

  {
  	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;

  	ssize_t cgid_len = cgid ? sizeof(*cgid) : 0;

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

  		return;

  	what |= ddir_act[op_is_write(op) ? WRITE : READ];
  	what |= MASK_TC_BIT(op_flags, SYNC);
  	what |= MASK_TC_BIT(op_flags, RAHEAD);
  	what |= MASK_TC_BIT(op_flags, META);

  	what |= MASK_TC_BIT(op_flags, PREFLUSH);

  	what |= MASK_TC_BIT(op_flags, FUA);

  	if (op == REQ_OP_DISCARD || op == REQ_OP_SECURE_ERASE)

  		what |= BLK_TC_ACT(BLK_TC_DISCARD);

  	if (op == REQ_OP_FLUSH)
  		what |= BLK_TC_ACT(BLK_TC_FLUSH);

  	if (cgid)
  		what |= __BLK_TA_CGROUP;

  
  	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 + cgid_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 + cgid_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 + cgid_len;

  		if (cgid_len)
  			memcpy((void *)t + sizeof(*t), cgid, cgid_len);

  		if (pdu_len)

  			memcpy((void *)t + sizeof(*t) + cgid_len, pdu_data, pdu_len);

  		if (blk_tracer) {

  			trace_buffer_unlock_commit(blk_tr, buffer, event, 0, pc);

  			return;
  		}

  	}
  
  	local_irq_restore(flags);
  }

  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 get_probe_ref(void)
  {
  	mutex_lock(&blk_probe_mutex);
  	if (++blk_probes_ref == 1)
  		blk_register_tracepoints();
  	mutex_unlock(&blk_probe_mutex);
  }
  
  static void put_probe_ref(void)
  {
  	mutex_lock(&blk_probe_mutex);
  	if (!--blk_probes_ref)
  		blk_unregister_tracepoints();
  	mutex_unlock(&blk_probe_mutex);
  }

  static void blk_trace_cleanup(struct blk_trace *bt)
  {

  	synchronize_rcu();

  	blk_trace_free(bt);

  	put_probe_ref();

  }

  static 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;
  }

  
  int blk_trace_remove(struct request_queue *q)
  {
  	int ret;
  
  	mutex_lock(&q->blk_trace_mutex);
  	ret = __blk_trace_remove(q);
  	mutex_unlock(&q->blk_trace_mutex);
  
  	return ret;
  }

  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 = memdup_user_nul(buffer, count);
  	if (IS_ERR(msg))
  		return PTR_ERR(msg);

  	bt = filp->private_data;

  	__trace_note_message(bt, NULL, "%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
   */

  static 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 *bt = NULL;

  	struct dentry *dir = NULL;

  	int ret;

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

  		return -EINVAL;

  	if (!blk_debugfs_root)
  		return -ENOENT;

  	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
  	 */

  	strreplace(buts->name, '/', '_');

  	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;

  	dir = debugfs_lookup(buts->name, blk_debugfs_root);
  	if (!dir)
  		bt->dir = dir = debugfs_create_dir(buts->name, blk_debugfs_root);

  	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);

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

  	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;

  	if (cmpxchg(&q->blk_trace, NULL, bt))

  		goto err;

  	get_probe_ref();

  	ret = 0;

  err:

  	if (dir && !bt->dir)
  		dput(dir);
  	if (ret)
  		blk_trace_free(bt);

  	return ret;
  }

  static 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;
  }

  
  int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
  		    struct block_device *bdev,
  		    char __user *arg)
  {
  	int ret;
  
  	mutex_lock(&q->blk_trace_mutex);
  	ret = __blk_trace_setup(q, name, dev, bdev, arg);
  	mutex_unlock(&q->blk_trace_mutex);
  
  	return ret;
  }

  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

  static int __blk_trace_startstop(struct request_queue *q, int start)

  {

  	int ret;

  	struct blk_trace *bt;

  	bt = rcu_dereference_protected(q->blk_trace,
  				       lockdep_is_held(&q->blk_trace_mutex));

  	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;
  }

  
  int blk_trace_startstop(struct request_queue *q, int start)
  {
  	int ret;
  
  	mutex_lock(&q->blk_trace_mutex);
  	ret = __blk_trace_startstop(q, start);
  	mutex_unlock(&q->blk_trace_mutex);
  
  	return ret;
  }

  EXPORT_SYMBOL_GPL(blk_trace_startstop);

  /*
   * When reading or writing the blktrace sysfs files, the references to the
   * opened sysfs or device files should prevent the underlying block device
   * from being removed. So no further delete protection is really needed.
   */

  /**
   * 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(&q->blk_trace_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;

  		/* fall through */

  	case BLKTRACESTOP:

  		ret = __blk_trace_startstop(q, start);

  		break;
  	case BLKTRACETEARDOWN:

  		ret = __blk_trace_remove(q);

  		break;
  	default:
  		ret = -ENOTTY;
  		break;
  	}

  	mutex_unlock(&q->blk_trace_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)

  {

  	mutex_lock(&q->blk_trace_mutex);

  	if (rcu_dereference_protected(q->blk_trace,
  				      lockdep_is_held(&q->blk_trace_mutex))) {

  		__blk_trace_startstop(q, 0);
  		__blk_trace_remove(q);

  	}

  
  	mutex_unlock(&q->blk_trace_mutex);

  }

  #ifdef CONFIG_BLK_CGROUP
  static union kernfs_node_id *
  blk_trace_bio_get_cgid(struct request_queue *q, struct bio *bio)
  {

  	struct blk_trace *bt;

  	/* We don't use the 'bt' value here except as an optimization... */
  	bt = rcu_dereference_protected(q->blk_trace, 1);

  	if (!bt || !(blk_tracer_flags.val & TRACE_BLK_OPT_CGROUP))
  		return NULL;

  	if (!bio->bi_blkg)

  		return NULL;

  	return cgroup_get_kernfs_id(bio_blkcg(bio)->css.cgroup);

  }
  #else
  static union kernfs_node_id *
  blk_trace_bio_get_cgid(struct request_queue *q, struct bio *bio)
  {
  	return NULL;
  }
  #endif
  
  static union kernfs_node_id *
  blk_trace_request_get_cgid(struct request_queue *q, struct request *rq)
  {
  	if (!rq->bio)
  		return NULL;
  	/* Use the first bio */
  	return blk_trace_bio_get_cgid(q, rq->bio);
  }

  /*
   * blktrace probes
   */
  
  /**
   * blk_add_trace_rq - Add a trace for a request oriented action

   * @rq:		the source request

   * @error:	return status to log

   * @nr_bytes:	number of completed bytes

   * @what:	the action

   * @cgid:	the cgroup info

   *
   * Description:
   *     Records an action against a request. Will log the bio offset + size.
   *
   **/

  static void blk_add_trace_rq(struct request *rq, int error,

  			     unsigned int nr_bytes, u32 what,
  			     union kernfs_node_id *cgid)

  {

  	struct blk_trace *bt;

  	rcu_read_lock();
  	bt = rcu_dereference(rq->q->blk_trace);
  	if (likely(!bt)) {
  		rcu_read_unlock();

  		return;

  	}

  	if (blk_rq_is_passthrough(rq))

  		what |= BLK_TC_ACT(BLK_TC_PC);

  	else

  		what |= BLK_TC_ACT(BLK_TC_FS);

  
  	__blk_add_trace(bt, blk_rq_trace_sector(rq), nr_bytes, req_op(rq),

  			rq->cmd_flags, what, error, 0, NULL, cgid);

  	rcu_read_unlock();

  }

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

  {

  	blk_add_trace_rq(rq, 0, blk_rq_bytes(rq), BLK_TA_INSERT,
  			 blk_trace_request_get_cgid(q, rq));

  }

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

  {

  	blk_add_trace_rq(rq, 0, blk_rq_bytes(rq), BLK_TA_ISSUE,
  			 blk_trace_request_get_cgid(q, rq));

  }

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

  				     struct request *rq)

  {

  	blk_add_trace_rq(rq, 0, blk_rq_bytes(rq), BLK_TA_REQUEUE,
  			 blk_trace_request_get_cgid(q, rq));

  }

  static void blk_add_trace_rq_complete(void *ignore, struct request *rq,
  			int error, unsigned int nr_bytes)

  {

  	blk_add_trace_rq(rq, error, nr_bytes, BLK_TA_COMPLETE,
  			 blk_trace_request_get_cgid(rq->q, rq));

  }
  
  /**
   * 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;

  	rcu_read_lock();
  	bt = rcu_dereference(q->blk_trace);
  	if (likely(!bt)) {
  		rcu_read_unlock();

  		return;

  	}

  	__blk_add_trace(bt, bio->bi_iter.bi_sector, bio->bi_iter.bi_size,

  			bio_op(bio), bio->bi_opf, what, error, 0, NULL,
  			blk_trace_bio_get_cgid(q, bio));

  	rcu_read_unlock();

  }

  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;

  		rcu_read_lock();
  		bt = rcu_dereference(q->blk_trace);

  		if (bt)

  			__blk_add_trace(bt, 0, 0, rw, 0, BLK_TA_GETRQ, 0, 0,

  					NULL, NULL);

  		rcu_read_unlock();

  	}
  }

  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;

  		rcu_read_lock();
  		bt = rcu_dereference(q->blk_trace);

  		if (bt)

  			__blk_add_trace(bt, 0, 0, rw, 0, BLK_TA_SLEEPRQ,

  					0, 0, NULL, NULL);

  		rcu_read_unlock();

  	}
  }

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

  {

  	struct blk_trace *bt;

  	rcu_read_lock();
  	bt = rcu_dereference(q->blk_trace);

  	if (bt)

  		__blk_add_trace(bt, 0, 0, 0, 0, BLK_TA_PLUG, 0, 0, NULL, NULL);

  	rcu_read_unlock();

  }

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

  {

  	struct blk_trace *bt;

  	rcu_read_lock();
  	bt = rcu_dereference(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, 0, what, 0, sizeof(rpdu), &rpdu, NULL);

  	}

  	rcu_read_unlock();

  }

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

  				unsigned int pdu)
  {

  	struct blk_trace *bt;

  	rcu_read_lock();
  	bt = rcu_dereference(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_op(bio), bio->bi_opf,

  				BLK_TA_SPLIT, bio->bi_status, sizeof(rpdu),

  				&rpdu, blk_trace_bio_get_cgid(q, bio));

  	}

  	rcu_read_unlock();

  }
  
  /**

   * 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;

  	struct blk_io_trace_remap r;

  	rcu_read_lock();
  	bt = rcu_dereference(q->blk_trace);
  	if (likely(!bt)) {
  		rcu_read_unlock();

  		return;

  	}

  	r.device_from = cpu_to_be32(dev);

  	r.device_to   = cpu_to_be32(bio_dev(bio));

  	r.sector_from = cpu_to_be64(from);

  	__blk_add_trace(bt, bio->bi_iter.bi_sector, bio->bi_iter.bi_size,

  			bio_op(bio), bio->bi_opf, BLK_TA_REMAP, bio->bi_status,

  			sizeof(r), &r, blk_trace_bio_get_cgid(q, bio));

  	rcu_read_unlock();

  }
  
  /**

   * 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;

  	struct blk_io_trace_remap r;

  	rcu_read_lock();
  	bt = rcu_dereference(q->blk_trace);
  	if (likely(!bt)) {
  		rcu_read_unlock();

  		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), 0, BLK_TA_REMAP, 0,

  			sizeof(r), &r, blk_trace_request_get_cgid(q, rq));

  	rcu_read_unlock();

  }
  
  /**

   * 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;

  	rcu_read_lock();
  	bt = rcu_dereference(q->blk_trace);
  	if (likely(!bt)) {
  		rcu_read_unlock();

  		return;

  	}

  	__blk_add_trace(bt, blk_rq_trace_sector(rq), blk_rq_bytes(rq), 0, 0,

  				BLK_TA_DRV_DATA, 0, len, data,
  				blk_trace_request_get_cgid(q, rq));

  	rcu_read_unlock();

  }
  EXPORT_SYMBOL_GPL(blk_add_driver_data);

  static void blk_register_tracepoints(void)

  {
  	int 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);

  
  	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_CGROUP) == 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, bool has_cg)
  {
  	return (void *)(te_blk_io_trace(ent) + 1) +
  		(has_cg ? sizeof(union kernfs_node_id) : 0);
  }
  
  static inline const void *cgid_start(const struct trace_entry *ent)

  {

  	return (void *)(te_blk_io_trace(ent) + 1);
  }
  
  static inline int pdu_real_len(const struct trace_entry *ent, bool has_cg)
  {
  	return te_blk_io_trace(ent)->pdu_len -
  			(has_cg ? sizeof(union kernfs_node_id) : 0);

  }

  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, bool has_cg)

  {

  	const __u64 *val = pdu_start(ent, has_cg);

  	return be64_to_cpu(*val);
  }
  
  static void get_pdu_remap(const struct trace_entry *ent,

  			  struct blk_io_trace_remap *r, bool has_cg)

  {

  	const struct blk_io_trace_remap *__r = pdu_start(ent, has_cg);

  	__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,
  	bool has_cg);

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

  {

  	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,
  	bool has_cg)

  {

  	char rwbs[RWBS_LEN];

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

  	fill_rwbs(rwbs, t);

  	if (has_cg) {
  		const union kernfs_node_id *id = cgid_start(iter->ent);

  		if (blk_tracer_flags.val & TRACE_BLK_OPT_CGNAME) {
  			char blkcg_name_buf[NAME_MAX + 1] = "<...>";
  
  			cgroup_path_from_kernfs_id(id, blkcg_name_buf,
  				sizeof(blkcg_name_buf));
  			trace_seq_printf(&iter->seq, "%3d,%-3d %s %2s %3s ",
  				 MAJOR(t->device), MINOR(t->device),
  				 blkcg_name_buf, act, rwbs);
  		} else
  			trace_seq_printf(&iter->seq,
  				 "%3d,%-3d %x,%-x %2s %3s ",

  				 MAJOR(t->device), MINOR(t->device),
  				 id->ino, id->generation, act, rwbs);
  	} else
  		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, bool has_cg)

  {

  	const unsigned char *pdu_buf;

  	int pdu_len;

  	int i, end;

  	pdu_buf = pdu_start(ent, has_cg);
  	pdu_len = pdu_real_len(ent, has_cg);

  
  	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, bool has_cg)