/*

   * 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/debugfs.h>

  #include <linux/time.h>

  #include <asm/uaccess.h>
  
  static DEFINE_PER_CPU(unsigned long long, blk_trace_cpu_offset) = { 0, };
  static unsigned int blktrace_seq __read_mostly = 1;
  
  /*

   * 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;

  
  	t = relay_reserve(bt->rchan, sizeof(*t) + len);

  	if (t) {
  		const int cpu = smp_processor_id();
  
  		t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
  		t->time = sched_clock() - per_cpu(blk_trace_cpu_offset, cpu);
  		t->device = bt->dev;
  		t->action = action;
  		t->pid = pid;
  		t->cpu = cpu;
  		t->pdu_len = len;
  		memcpy((void *) t + sizeof(*t), data, len);
  	}

  }
  
  /*

   * Send out a notify for this process, if we haven't done so since a trace
   * started
   */
  static void trace_note_tsk(struct blk_trace *bt, struct task_struct *tsk)
  {

  	tsk->btrace_seq = blktrace_seq;
  	trace_note(bt, tsk->pid, BLK_TN_PROCESS, tsk->comm, sizeof(tsk->comm));

  }

  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);

  }
  
  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 < bt->start_lba || sector > bt->end_lba)
  		return 1;
  	if (bt->pid && pid != bt->pid)
  		return 1;
  
  	return 0;
  }
  
  /*
   * Data direction bit lookup
   */
  static u32 ddir_act[2] __read_mostly = { BLK_TC_ACT(BLK_TC_READ), BLK_TC_ACT(BLK_TC_WRITE) };
  
  /*
   * Bio action bits of interest
   */

  static u32 bio_act[9] __read_mostly = { 0, BLK_TC_ACT(BLK_TC_BARRIER), BLK_TC_ACT(BLK_TC_SYNC), 0, BLK_TC_ACT(BLK_TC_AHEAD), 0, 0, 0, BLK_TC_ACT(BLK_TC_META) };

  
  /*
   * More could be added as needed, taking care to increment the decrementer
   * to get correct indexing
   */
  #define trace_barrier_bit(rw)	\
  	(((rw) & (1 << BIO_RW_BARRIER)) >> (BIO_RW_BARRIER - 0))
  #define trace_sync_bit(rw)	\
  	(((rw) & (1 << BIO_RW_SYNC)) >> (BIO_RW_SYNC - 1))

  #define trace_ahead_bit(rw)	\

  	(((rw) & (1 << BIO_RW_AHEAD)) << (2 - BIO_RW_AHEAD))

  #define trace_meta_bit(rw)	\
  	(((rw) & (1 << BIO_RW_META)) >> (BIO_RW_META - 3))

  
  /*
   * The worker for the various blk_add_trace*() types. Fills out a
   * blk_io_trace structure and places it in a per-cpu subbuffer.
   */
  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 blk_io_trace *t;
  	unsigned long flags;
  	unsigned long *sequence;
  	pid_t pid;
  	int cpu;
  
  	if (unlikely(bt->trace_state != Blktrace_running))
  		return;
  
  	what |= ddir_act[rw & WRITE];
  	what |= bio_act[trace_barrier_bit(rw)];
  	what |= bio_act[trace_sync_bit(rw)];

  	what |= bio_act[trace_ahead_bit(rw)];

  	what |= bio_act[trace_meta_bit(rw)];

  
  	pid = tsk->pid;
  	if (unlikely(act_log_check(bt, what, sector, pid)))
  		return;
  
  	/*
  	 * 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. Once reserved, it's
  	 * enough to get preemption disabled to prevent read of this data
  	 * before we are through filling it. get_cpu()/put_cpu() does this
  	 * for us
  	 */
  	local_irq_save(flags);
  
  	if (unlikely(tsk->btrace_seq != blktrace_seq))
  		trace_note_tsk(bt, tsk);
  
  	t = relay_reserve(bt->rchan, sizeof(*t) + pdu_len);
  	if (t) {
  		cpu = smp_processor_id();
  		sequence = per_cpu_ptr(bt->sequence, cpu);
  
  		t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
  		t->sequence = ++(*sequence);
  		t->time = sched_clock() - per_cpu(blk_trace_cpu_offset, cpu);
  		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);
  	}
  
  	local_irq_restore(flags);
  }
  
  EXPORT_SYMBOL_GPL(__blk_add_trace);
  
  static struct dentry *blk_tree_root;
  static struct mutex blk_tree_mutex;
  static unsigned int root_users;
  
  static inline void blk_remove_root(void)
  {
  	if (blk_tree_root) {
  		debugfs_remove(blk_tree_root);
  		blk_tree_root = NULL;
  	}
  }
  
  static void blk_remove_tree(struct dentry *dir)
  {
  	mutex_lock(&blk_tree_mutex);
  	debugfs_remove(dir);
  	if (--root_users == 0)
  		blk_remove_root();
  	mutex_unlock(&blk_tree_mutex);
  }
  
  static struct dentry *blk_create_tree(const char *blk_name)
  {
  	struct dentry *dir = NULL;
  
  	mutex_lock(&blk_tree_mutex);
  
  	if (!blk_tree_root) {
  		blk_tree_root = debugfs_create_dir("block", NULL);
  		if (!blk_tree_root)
  			goto err;
  	}
  
  	dir = debugfs_create_dir(blk_name, blk_tree_root);
  	if (dir)
  		root_users++;
  	else
  		blk_remove_root();
  
  err:
  	mutex_unlock(&blk_tree_mutex);
  	return dir;
  }
  
  static void blk_trace_cleanup(struct blk_trace *bt)
  {
  	relay_close(bt->rchan);
  	debugfs_remove(bt->dropped_file);
  	blk_remove_tree(bt->dir);
  	free_percpu(bt->sequence);
  	kfree(bt);
  }
  
  static int blk_trace_remove(request_queue_t *q)
  {
  	struct blk_trace *bt;
  
  	bt = xchg(&q->blk_trace, NULL);
  	if (!bt)
  		return -EINVAL;
  
  	if (bt->trace_state == Blktrace_setup ||
  	    bt->trace_state == Blktrace_stopped)
  		blk_trace_cleanup(bt);
  
  	return 0;
  }
  
  static int blk_dropped_open(struct inode *inode, struct file *filp)
  {

  	filp->private_data = inode->i_private;

  
  	return 0;
  }
  
  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 =		blk_dropped_open,
  	.read =		blk_dropped_read,
  };
  
  /*
   * 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,
  						   int 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,
  };
  
  /*
   * Setup everything required to start tracing
   */
  static int blk_trace_setup(request_queue_t *q, struct block_device *bdev,
  			   char __user *arg)
  {
  	struct blk_user_trace_setup buts;
  	struct blk_trace *old_bt, *bt = NULL;
  	struct dentry *dir = NULL;
  	char b[BDEVNAME_SIZE];
  	int ret, i;
  
  	if (copy_from_user(&buts, arg, sizeof(buts)))
  		return -EFAULT;
  
  	if (!buts.buf_size || !buts.buf_nr)
  		return -EINVAL;
  
  	strcpy(buts.name, bdevname(bdev, b));
  
  	/*
  	 * 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] = '_';
  
  	if (copy_to_user(arg, &buts, sizeof(buts)))
  		return -EFAULT;
  
  	ret = -ENOMEM;
  	bt = kzalloc(sizeof(*bt), GFP_KERNEL);
  	if (!bt)
  		goto err;
  
  	bt->sequence = alloc_percpu(unsigned long);
  	if (!bt->sequence)
  		goto err;
  
  	ret = -ENOENT;
  	dir = blk_create_tree(buts.name);
  	if (!dir)
  		goto err;
  
  	bt->dir = dir;
  	bt->dev = bdev->bd_dev;
  	atomic_set(&bt->dropped, 0);
  
  	ret = -EIO;
  	bt->dropped_file = debugfs_create_file("dropped", 0444, dir, bt, &blk_dropped_fops);
  	if (!bt->dropped_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;
  
  	bt->start_lba = buts.start_lba;
  	bt->end_lba = buts.end_lba;
  	if (!bt->end_lba)
  		bt->end_lba = -1ULL;
  
  	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;
  	}
  
  	return 0;
  err:
  	if (dir)
  		blk_remove_tree(dir);
  	if (bt) {
  		if (bt->dropped_file)
  			debugfs_remove(bt->dropped_file);

  		free_percpu(bt->sequence);

  		if (bt->rchan)
  			relay_close(bt->rchan);
  		kfree(bt);
  	}
  	return ret;
  }
  
  static int blk_trace_startstop(request_queue_t *q, int start)
  {
  	struct blk_trace *bt;
  	int ret;
  
  	if ((bt = q->blk_trace) == 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;

  
  			trace_note_time(bt);

  			ret = 0;
  		}
  	} else {
  		if (bt->trace_state == Blktrace_running) {
  			bt->trace_state = Blktrace_stopped;
  			relay_flush(bt->rchan);
  			ret = 0;
  		}
  	}
  
  	return ret;
  }
  
  /**
   * 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)
  {
  	request_queue_t *q;
  	int ret, start = 0;
  
  	q = bdev_get_queue(bdev);
  	if (!q)
  		return -ENXIO;
  
  	mutex_lock(&bdev->bd_mutex);
  
  	switch (cmd) {
  	case BLKTRACESETUP:
  		ret = blk_trace_setup(q, bdev, arg);
  		break;
  	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(request_queue_t *q)
  {

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

  }
  
  /*
   * Average offset over two calls to sched_clock() with a gettimeofday()
   * in the middle
   */
  static void blk_check_time(unsigned long long *t)
  {
  	unsigned long long a, b;
  	struct timeval tv;
  
  	a = sched_clock();
  	do_gettimeofday(&tv);
  	b = sched_clock();
  
  	*t = tv.tv_sec * 1000000000 + tv.tv_usec * 1000;
  	*t -= (a + b) / 2;
  }

  /*
   * calibrate our inter-CPU timings
   */

  static void blk_trace_check_cpu_time(void *data)
  {
  	unsigned long long *t;
  	int cpu = get_cpu();
  
  	t = &per_cpu(blk_trace_cpu_offset, cpu);
  
  	/*
  	 * Just call it twice, hopefully the second call will be cache hot
  	 * and a little more precise
  	 */
  	blk_check_time(t);
  	blk_check_time(t);
  
  	put_cpu();
  }

  static void blk_trace_set_ht_offsets(void)
  {
  #if defined(CONFIG_SCHED_SMT)
  	int cpu, i;
  
  	/*
  	 * now make sure HT siblings have the same time offset
  	 */
  	preempt_disable();
  	for_each_online_cpu(cpu) {
  		unsigned long long *cpu_off, *sibling_off;
  
  		for_each_cpu_mask(i, cpu_sibling_map[cpu]) {
  			if (i == cpu)
  				continue;
  
  			cpu_off = &per_cpu(blk_trace_cpu_offset, cpu);
  			sibling_off = &per_cpu(blk_trace_cpu_offset, i);
  			*sibling_off = *cpu_off;
  		}
  	}
  	preempt_enable();
  #endif
  }
  
  static __init int blk_trace_init(void)
  {
  	mutex_init(&blk_tree_mutex);

  	on_each_cpu(blk_trace_check_cpu_time, NULL, 1, 1);

  	blk_trace_set_ht_offsets();
  
  	return 0;
  }
  
  module_init(blk_trace_init);