[linux.git] / block / blktrace.c

/*
 * Copyright (C) 2006 Jens Axboe <[email protected]>
 *
 * 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 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 = ktime_to_ns(ktime_get());
		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);
}

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

	local_irq_save(flags);
	buf = per_cpu_ptr(bt->msg_data, smp_processor_id());
	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 < 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.
	 */
	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 = ktime_to_ns(ktime_get());
		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 DEFINE_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;
	int created = 0;

	mutex_lock(&blk_tree_mutex);

	if (!blk_tree_root) {
		blk_tree_root = debugfs_create_dir("block", NULL);
		if (!blk_tree_root)
			goto err;
		created = 1;
	}

	dir = debugfs_create_dir(blk_name, blk_tree_root);
	if (dir)
		root_users++;
	else {
		/* Delete root only if we created it */
		if (created)
			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);
	free_percpu(bt->msg_data);
	kfree(bt);
}

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_setup ||
	    bt->trace_state == Blktrace_stopped)
		blk_trace_cleanup(bt);

	return 0;
}
EXPORT_SYMBOL_GPL(blk_trace_remove);

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\n", 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
 */
int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
			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;

	strcpy(buts->name, name);

	/*
	 * 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] = '_';

	ret = -ENOMEM;
	bt = kzalloc(sizeof(*bt), GFP_KERNEL);
	if (!bt)
		goto err;

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

	bt->msg_data = __alloc_percpu(BLK_TN_MAX_MSG);
	if (!bt->msg_data)
		goto err;

	ret = -ENOENT;
	dir = blk_create_tree(buts->name);
	if (!dir)
		goto err;

	bt->dir = dir;
	bt->dev = 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);
		free_percpu(bt->msg_data);
		if (bt->rchan)
			relay_close(bt->rchan);
		kfree(bt);
	}
	return ret;
}

int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
		    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, &buts);
	if (ret)
		return ret;

	if (copy_to_user(arg, &buts, sizeof(buts)))
		return -EFAULT;

	return 0;
}
EXPORT_SYMBOL_GPL(blk_trace_setup);

int blk_trace_startstop(struct request_queue *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;
}
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, 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(struct request_queue *q)
{
	if (q->blk_trace) {
		blk_trace_startstop(q, 0);
		blk_trace_remove(q);
	}
}
Commit	Line	Data
2056a782	1	/*
0fe23479	2	* Copyright (C) 2006 Jens Axboe <[email protected]>
2056a782 JA	3	*
	4	* This program is free software; you can redistribute it and/or modify
	5	* it under the terms of the GNU General Public License version 2 as
	6	* published by the Free Software Foundation.
	7	*
	8	* This program is distributed in the hope that it will be useful,
	9	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	10	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	11	* GNU General Public License for more details.
	12	*
	13	* You should have received a copy of the GNU General Public License
	14	* along with this program; if not, write to the Free Software
	15	* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
	16	*
	17	*/
2056a782 JA	18	#include <linux/kernel.h>
	19	#include <linux/blkdev.h>
	20	#include <linux/blktrace_api.h>
	21	#include <linux/percpu.h>
	22	#include <linux/init.h>
	23	#include <linux/mutex.h>
	24	#include <linux/debugfs.h>
be1c6341	25	#include <linux/time.h>
2056a782 JA	26	#include <asm/uaccess.h>
2056a782 JA	27
2056a782 JA	28	static unsigned int blktrace_seq __read_mostly = 1;
2056a782 JA	29
be1c6341 OK	30	/*
	31	* Send out a notify message.
	32	*/
a863055b JA	33	static void trace_note(struct blk_trace *bt, pid_t pid, int action,
a863055b JA	34	const void *data, size_t len)
be1c6341 OK	35	{
be1c6341 OK	36	struct blk_io_trace *t;
be1c6341 OK	37
be1c6341 OK	38	t = relay_reserve(bt->rchan, sizeof(*t) + len);
d3d9d2a5 JA	39	if (t) {
	40	const int cpu = smp_processor_id();
	41
	42	t->magic = BLK_IO_TRACE_MAGIC \| BLK_IO_TRACE_VERSION;
2997c8c4	43	t->time = ktime_to_ns(ktime_get());
d3d9d2a5 JA	44	t->device = bt->dev;
	45	t->action = action;
	46	t->pid = pid;
	47	t->cpu = cpu;
	48	t->pdu_len = len;
	49	memcpy((void ) t + sizeof(t), data, len);
	50	}
be1c6341 OK	51	}
be1c6341 OK	52
2056a782 JA	53	/*
	54	* Send out a notify for this process, if we haven't done so since a trace
	55	* started
	56	*/
	57	static void trace_note_tsk(struct blk_trace bt, struct task_struct tsk)
	58	{
a863055b JA	59	tsk->btrace_seq = blktrace_seq;
a863055b JA	60	trace_note(bt, tsk->pid, BLK_TN_PROCESS, tsk->comm, sizeof(tsk->comm));
be1c6341	61	}
2056a782	62
be1c6341 OK	63	static void trace_note_time(struct blk_trace *bt)
	64	{
	65	struct timespec now;
	66	unsigned long flags;
	67	u32 words[2];
	68
	69	getnstimeofday(&now);
	70	words[0] = now.tv_sec;
	71	words[1] = now.tv_nsec;
	72
	73	local_irq_save(flags);
	74	trace_note(bt, 0, BLK_TN_TIMESTAMP, words, sizeof(words));
	75	local_irq_restore(flags);
2056a782 JA	76	}
2056a782 JA	77
9d5f09a4 AB	78	void __trace_note_message(struct blk_trace bt, const char fmt, ...)
	79	{
	80	int n;
	81	va_list args;
14a73f54	82	unsigned long flags;
64565911	83	char *buf;
9d5f09a4	84
14a73f54	85	local_irq_save(flags);
64565911	86	buf = per_cpu_ptr(bt->msg_data, smp_processor_id());
9d5f09a4	87	va_start(args, fmt);
64565911	88	n = vscnprintf(buf, BLK_TN_MAX_MSG, fmt, args);
9d5f09a4 AB	89	va_end(args);
9d5f09a4 AB	90
64565911	91	trace_note(bt, 0, BLK_TN_MESSAGE, buf, n);
14a73f54	92	local_irq_restore(flags);
9d5f09a4 AB	93	}
	94	EXPORT_SYMBOL_GPL(__trace_note_message);
	95
2056a782 JA	96	static int act_log_check(struct blk_trace *bt, u32 what, sector_t sector,
	97	pid_t pid)
	98	{
	99	if (((bt->act_mask << BLK_TC_SHIFT) & what) == 0)
	100	return 1;
	101	if (sector < bt->start_lba \|\| sector > bt->end_lba)
	102	return 1;
	103	if (bt->pid && pid != bt->pid)
	104	return 1;
	105
	106	return 0;
	107	}
	108
	109	/*
	110	* Data direction bit lookup
	111	*/
	112	static u32 ddir_act[2] __read_mostly = { BLK_TC_ACT(BLK_TC_READ), BLK_TC_ACT(BLK_TC_WRITE) };
	113
	114	/*
	115	* Bio action bits of interest
	116	*/
7457e6e2	117	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) };
2056a782 JA	118
	119	/*
	120	* More could be added as needed, taking care to increment the decrementer
	121	* to get correct indexing
	122	*/
	123	#define trace_barrier_bit(rw) \
	124	(((rw) & (1 << BIO_RW_BARRIER)) >> (BIO_RW_BARRIER - 0))
	125	#define trace_sync_bit(rw) \
	126	(((rw) & (1 << BIO_RW_SYNC)) >> (BIO_RW_SYNC - 1))
40359ccb	127	#define trace_ahead_bit(rw) \
ad01b1ca	128	(((rw) & (1 << BIO_RW_AHEAD)) << (2 - BIO_RW_AHEAD))
7457e6e2 JA	129	#define trace_meta_bit(rw) \
7457e6e2 JA	130	(((rw) & (1 << BIO_RW_META)) >> (BIO_RW_META - 3))
2056a782 JA	131
	132	/*
	133	* The worker for the various blk_add_trace*() types. Fills out a
	134	* blk_io_trace structure and places it in a per-cpu subbuffer.
	135	*/
	136	void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
	137	int rw, u32 what, int error, int pdu_len, void *pdu_data)
	138	{
	139	struct task_struct *tsk = current;
	140	struct blk_io_trace *t;
	141	unsigned long flags;
	142	unsigned long *sequence;
	143	pid_t pid;
	144	int cpu;
	145
	146	if (unlikely(bt->trace_state != Blktrace_running))
	147	return;
	148
	149	what \|= ddir_act[rw & WRITE];
	150	what \|= bio_act[trace_barrier_bit(rw)];
	151	what \|= bio_act[trace_sync_bit(rw)];
40359ccb	152	what \|= bio_act[trace_ahead_bit(rw)];
7457e6e2	153	what \|= bio_act[trace_meta_bit(rw)];
2056a782 JA	154
	155	pid = tsk->pid;
	156	if (unlikely(act_log_check(bt, what, sector, pid)))
	157	return;
	158
	159	/*
	160	* A word about the locking here - we disable interrupts to reserve
	161	* some space in the relay per-cpu buffer, to prevent an irq
14a73f54	162	* from coming in and stepping on our toes.
2056a782 JA	163	*/
	164	local_irq_save(flags);
	165
	166	if (unlikely(tsk->btrace_seq != blktrace_seq))
	167	trace_note_tsk(bt, tsk);
	168
	169	t = relay_reserve(bt->rchan, sizeof(*t) + pdu_len);
	170	if (t) {
	171	cpu = smp_processor_id();
	172	sequence = per_cpu_ptr(bt->sequence, cpu);
	173
	174	t->magic = BLK_IO_TRACE_MAGIC \| BLK_IO_TRACE_VERSION;
	175	t->sequence = ++(*sequence);
2997c8c4	176	t->time = ktime_to_ns(ktime_get());
2056a782 JA	177	t->sector = sector;
	178	t->bytes = bytes;
	179	t->action = what;
	180	t->pid = pid;
	181	t->device = bt->dev;
	182	t->cpu = cpu;
	183	t->error = error;
	184	t->pdu_len = pdu_len;
	185
	186	if (pdu_len)
	187	memcpy((void ) t + sizeof(t), pdu_data, pdu_len);
	188	}
	189
	190	local_irq_restore(flags);
	191	}
	192
	193	EXPORT_SYMBOL_GPL(__blk_add_trace);
	194
	195	static struct dentry *blk_tree_root;
11a57153	196	static DEFINE_MUTEX(blk_tree_mutex);
2056a782 JA	197	static unsigned int root_users;
	198
	199	static inline void blk_remove_root(void)
	200	{
	201	if (blk_tree_root) {
	202	debugfs_remove(blk_tree_root);
	203	blk_tree_root = NULL;
	204	}
	205	}
	206
	207	static void blk_remove_tree(struct dentry *dir)
	208	{
	209	mutex_lock(&blk_tree_mutex);
	210	debugfs_remove(dir);
	211	if (--root_users == 0)
	212	blk_remove_root();
	213	mutex_unlock(&blk_tree_mutex);
	214	}
	215
	216	static struct dentry blk_create_tree(const char blk_name)
	217	{
	218	struct dentry *dir = NULL;
35fc51e7	219	int created = 0;
2056a782 JA	220
	221	mutex_lock(&blk_tree_mutex);
	222
	223	if (!blk_tree_root) {
	224	blk_tree_root = debugfs_create_dir("block", NULL);
	225	if (!blk_tree_root)
	226	goto err;
35fc51e7	227	created = 1;
2056a782 JA	228	}
	229
	230	dir = debugfs_create_dir(blk_name, blk_tree_root);
	231	if (dir)
	232	root_users++;
35fc51e7 AK	233	else {
	234	/* Delete root only if we created it */
	235	if (created)
	236	blk_remove_root();
	237	}
2056a782 JA	238
	239	err:
	240	mutex_unlock(&blk_tree_mutex);
	241	return dir;
	242	}
	243
	244	static void blk_trace_cleanup(struct blk_trace *bt)
	245	{
	246	relay_close(bt->rchan);
	247	debugfs_remove(bt->dropped_file);
	248	blk_remove_tree(bt->dir);
	249	free_percpu(bt->sequence);
64565911	250	free_percpu(bt->msg_data);
2056a782 JA	251	kfree(bt);
	252	}
	253
6da127ad	254	int blk_trace_remove(struct request_queue *q)
2056a782 JA	255	{
	256	struct blk_trace *bt;
	257
	258	bt = xchg(&q->blk_trace, NULL);
	259	if (!bt)
	260	return -EINVAL;
	261
	262	if (bt->trace_state == Blktrace_setup \|\|
	263	bt->trace_state == Blktrace_stopped)
	264	blk_trace_cleanup(bt);
	265
	266	return 0;
	267	}
6da127ad	268	EXPORT_SYMBOL_GPL(blk_trace_remove);
2056a782 JA	269
	270	static int blk_dropped_open(struct inode inode, struct file filp)
	271	{
8e18e294	272	filp->private_data = inode->i_private;
2056a782 JA	273
	274	return 0;
	275	}
	276
	277	static ssize_t blk_dropped_read(struct file filp, char __user buffer,
	278	size_t count, loff_t *ppos)
	279	{
	280	struct blk_trace *bt = filp->private_data;
	281	char buf[16];
	282
	283	snprintf(buf, sizeof(buf), "%u\n", atomic_read(&bt->dropped));
	284
	285	return simple_read_from_buffer(buffer, count, ppos, buf, strlen(buf));
	286	}
	287
2b8693c0	288	static const struct file_operations blk_dropped_fops = {
2056a782 JA	289	.owner = THIS_MODULE,
	290	.open = blk_dropped_open,
	291	.read = blk_dropped_read,
	292	};
	293
	294	/*
	295	* Keep track of how many times we encountered a full subbuffer, to aid
	296	* the user space app in telling how many lost events there were.
	297	*/
	298	static int blk_subbuf_start_callback(struct rchan_buf buf, void subbuf,
	299	void *prev_subbuf, size_t prev_padding)
	300	{
	301	struct blk_trace *bt;
	302
	303	if (!relay_buf_full(buf))
	304	return 1;
	305
	306	bt = buf->chan->private_data;
	307	atomic_inc(&bt->dropped);
	308	return 0;
	309	}
	310
	311	static int blk_remove_buf_file_callback(struct dentry *dentry)
	312	{
	313	debugfs_remove(dentry);
	314	return 0;
	315	}
	316
	317	static struct dentry blk_create_buf_file_callback(const char filename,
	318	struct dentry *parent,
	319	int mode,
	320	struct rchan_buf *buf,
	321	int *is_global)
	322	{
	323	return debugfs_create_file(filename, mode, parent, buf,
	324	&relay_file_operations);
	325	}
	326
	327	static struct rchan_callbacks blk_relay_callbacks = {
	328	.subbuf_start = blk_subbuf_start_callback,
	329	.create_buf_file = blk_create_buf_file_callback,
	330	.remove_buf_file = blk_remove_buf_file_callback,
	331	};
	332
	333	/*
	334	* Setup everything required to start tracing
	335	*/
6da127ad	336	int do_blk_trace_setup(struct request_queue q, char name, dev_t dev,
171044d4	337	struct blk_user_trace_setup *buts)
2056a782	338	{
2056a782 JA	339	struct blk_trace old_bt, bt = NULL;
2056a782 JA	340	struct dentry *dir = NULL;
2056a782 JA	341	int ret, i;
2056a782 JA	342
171044d4	343	if (!buts->buf_size \|\| !buts->buf_nr)
2056a782 JA	344	return -EINVAL;
2056a782 JA	345
6da127ad	346	strcpy(buts->name, name);
2056a782 JA	347
	348	/*
	349	* some device names have larger paths - convert the slashes
	350	* to underscores for this to work as expected
	351	*/
171044d4 AB	352	for (i = 0; i < strlen(buts->name); i++)
	353	if (buts->name[i] == '/')
	354	buts->name[i] = '_';
2056a782 JA	355
	356	ret = -ENOMEM;
	357	bt = kzalloc(sizeof(*bt), GFP_KERNEL);
	358	if (!bt)
	359	goto err;
	360
	361	bt->sequence = alloc_percpu(unsigned long);
	362	if (!bt->sequence)
	363	goto err;
	364
64565911 JA	365	bt->msg_data = __alloc_percpu(BLK_TN_MAX_MSG);
	366	if (!bt->msg_data)
	367	goto err;
	368
2056a782	369	ret = -ENOENT;
171044d4	370	dir = blk_create_tree(buts->name);
2056a782 JA	371	if (!dir)
	372	goto err;
	373
	374	bt->dir = dir;
6da127ad	375	bt->dev = dev;
2056a782 JA	376	atomic_set(&bt->dropped, 0);
	377
	378	ret = -EIO;
	379	bt->dropped_file = debugfs_create_file("dropped", 0444, dir, bt, &blk_dropped_fops);
	380	if (!bt->dropped_file)
	381	goto err;
	382
171044d4 AB	383	bt->rchan = relay_open("trace", dir, buts->buf_size,
171044d4 AB	384	buts->buf_nr, &blk_relay_callbacks, bt);
2056a782 JA	385	if (!bt->rchan)
2056a782 JA	386	goto err;
2056a782	387
171044d4	388	bt->act_mask = buts->act_mask;
2056a782 JA	389	if (!bt->act_mask)
	390	bt->act_mask = (u16) -1;
	391
171044d4 AB	392	bt->start_lba = buts->start_lba;
171044d4 AB	393	bt->end_lba = buts->end_lba;
2056a782 JA	394	if (!bt->end_lba)
	395	bt->end_lba = -1ULL;
	396
171044d4	397	bt->pid = buts->pid;
2056a782 JA	398	bt->trace_state = Blktrace_setup;
	399
	400	ret = -EBUSY;
	401	old_bt = xchg(&q->blk_trace, bt);
	402	if (old_bt) {
	403	(void) xchg(&q->blk_trace, old_bt);
	404	goto err;
	405	}
	406
	407	return 0;
	408	err:
	409	if (dir)
	410	blk_remove_tree(dir);
	411	if (bt) {
	412	if (bt->dropped_file)
	413	debugfs_remove(bt->dropped_file);
a1205868	414	free_percpu(bt->sequence);
64565911	415	free_percpu(bt->msg_data);
2056a782 JA	416	if (bt->rchan)
	417	relay_close(bt->rchan);
	418	kfree(bt);
	419	}
	420	return ret;
	421	}
171044d4	422
6da127ad CS	423	int blk_trace_setup(struct request_queue q, char name, dev_t dev,
6da127ad CS	424	char __user *arg)
171044d4 AB	425	{
	426	struct blk_user_trace_setup buts;
	427	int ret;
	428
	429	ret = copy_from_user(&buts, arg, sizeof(buts));
	430	if (ret)
	431	return -EFAULT;
	432
6da127ad	433	ret = do_blk_trace_setup(q, name, dev, &buts);
171044d4 AB	434	if (ret)
	435	return ret;
	436
	437	if (copy_to_user(arg, &buts, sizeof(buts)))
	438	return -EFAULT;
	439
	440	return 0;
	441	}
6da127ad	442	EXPORT_SYMBOL_GPL(blk_trace_setup);
2056a782	443
6da127ad	444	int blk_trace_startstop(struct request_queue *q, int start)
2056a782 JA	445	{
	446	struct blk_trace *bt;
	447	int ret;
	448
	449	if ((bt = q->blk_trace) == NULL)
	450	return -EINVAL;
	451
	452	/*
	453	* For starting a trace, we can transition from a setup or stopped
	454	* trace. For stopping a trace, the state must be running
	455	*/
	456	ret = -EINVAL;
	457	if (start) {
	458	if (bt->trace_state == Blktrace_setup \|\|
	459	bt->trace_state == Blktrace_stopped) {
	460	blktrace_seq++;
	461	smp_mb();
	462	bt->trace_state = Blktrace_running;
be1c6341 OK	463
be1c6341 OK	464	trace_note_time(bt);
2056a782 JA	465	ret = 0;
	466	}
	467	} else {
	468	if (bt->trace_state == Blktrace_running) {
	469	bt->trace_state = Blktrace_stopped;
	470	relay_flush(bt->rchan);
	471	ret = 0;
	472	}
	473	}
	474
	475	return ret;
	476	}
6da127ad	477	EXPORT_SYMBOL_GPL(blk_trace_startstop);
2056a782 JA	478
	479	/**
	480	* blk_trace_ioctl: - handle the ioctls associated with tracing
	481	* @bdev: the block device
	482	* @cmd: the ioctl cmd
	483	* @arg: the argument data, if any
	484	*
	485	**/
	486	int blk_trace_ioctl(struct block_device bdev, unsigned cmd, char __user arg)
	487	{
165125e1	488	struct request_queue *q;
2056a782	489	int ret, start = 0;
6da127ad	490	char b[BDEVNAME_SIZE];
2056a782 JA	491
	492	q = bdev_get_queue(bdev);
	493	if (!q)
	494	return -ENXIO;
	495
	496	mutex_lock(&bdev->bd_mutex);
	497
	498	switch (cmd) {
	499	case BLKTRACESETUP:
f36f21ec	500	bdevname(bdev, b);
6da127ad	501	ret = blk_trace_setup(q, b, bdev->bd_dev, arg);
2056a782 JA	502	break;
	503	case BLKTRACESTART:
	504	start = 1;
	505	case BLKTRACESTOP:
	506	ret = blk_trace_startstop(q, start);
	507	break;
	508	case BLKTRACETEARDOWN:
	509	ret = blk_trace_remove(q);
	510	break;
	511	default:
	512	ret = -ENOTTY;
	513	break;
	514	}
	515
	516	mutex_unlock(&bdev->bd_mutex);
	517	return ret;
	518	}
	519
	520	/**
	521	* blk_trace_shutdown: - stop and cleanup trace structures
	522	* @q: the request queue associated with the device
	523	*
	524	**/
165125e1	525	void blk_trace_shutdown(struct request_queue *q)
2056a782	526	{
6c5c9341 AD	527	if (q->blk_trace) {
	528	blk_trace_startstop(q, 0);
	529	blk_trace_remove(q);
	530	}
2056a782	531	}