[mirror_ubuntu-artful-kernel.git] / block / blktrace.c

/*
 * 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 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;
	static char bt_msg_buf[BLK_TN_MAX_MSG];

	va_start(args, fmt);
	n = vscnprintf(bt_msg_buf, BLK_TN_MAX_MSG, fmt, args);
	va_end(args);

	trace_note(bt, 0, BLK_TN_MESSAGE, bt_msg_buf, n);
}
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. 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 = 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);
	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;

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