linux/block/blktrace.c
Jens Axboe 64565911cd block: make blktrace use per-cpu buffers for message notes
Currently it uses a single static char array, but that risks
being corrupted when multiple users issue message notes at the
same time. Make the buffers dynamically allocated when the trace
is setup and make them per-cpu instead.

The default max message size of 1k is also very large, the
interface is mainly for small text notes. So shrink it to 128 bytes.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-05-28 14:49:27 +02:00

533 lines
12 KiB
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;
char *buf;
preempt_disable();
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);
preempt_enable();
}
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);
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);
}
}