include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit...

[mirror_ubuntu-artful-kernel.git] / kernel / trace / 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/slab.h>
#include <linux/debugfs.h>
#include <linux/smp_lock.h>
#include <linux/time.h>
#include <linux/uaccess.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;

/* Select an alternative, minimalistic output than the original one */
#define TRACE_BLK_OPT_CLASSIC   0x1

static struct tracer_opt blk_tracer_opts[] = {
        /* Default disable the minimalistic output */
        { TRACER_OPT(blk_classic, TRACE_BLK_OPT_CLASSIC) },
        { }
};

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

/* Global reference count of probes */
static atomic_t blk_probes_ref = ATOMIC_INIT(0);

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)
{
        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;

        if (blk_tracer) {
                buffer = blk_tr->buffer;
                pc = preempt_count();
                event = trace_buffer_lock_reserve(buffer, TRACE_BLK,
                                                  sizeof(*t) + 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);
        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;
                t->pid = pid;
                t->cpu = cpu;
                t->pdu_len = len;
                memcpy((void *) t + sizeof(*t), data, len);

                if (blk_tracer)
                        trace_buffer_unlock_commit(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 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;

        if (unlikely(bt->trace_state != Blktrace_running &&
                     !blk_tracer_enabled))
                return;

        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 && (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) };

/* The ilog2() calls fall out because they're constant */
#define MASK_TC_BIT(rw, __name) ((rw & (1 << BIO_RW_ ## __name)) << \
          (ilog2(BLK_TC_ ## __name) + BLK_TC_SHIFT - BIO_RW_ ## __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 rw, u32 what, int error, int pdu_len, void *pdu_data)
{
        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;

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

        what |= ddir_act[rw & WRITE];
        what |= MASK_TC_BIT(rw, BARRIER);
        what |= MASK_TC_BIT(rw, SYNCIO);
        what |= MASK_TC_BIT(rw, AHEAD);
        what |= MASK_TC_BIT(rw, META);
        what |= MASK_TC_BIT(rw, DISCARD);

        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->buffer;
                pc = preempt_count();
                event = trace_buffer_lock_reserve(buffer, TRACE_BLK,
                                                  sizeof(*t) + pdu_len,
                                                  0, pc);
                if (!event)
                        return;
                t = ring_buffer_event_data(event);
                goto record_it;
        }

        /*
         * 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) {
                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;

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

                if (blk_tracer) {
                        trace_buffer_unlock_commit(buffer, event, 0, pc);
                        return;
                }
        }

        local_irq_restore(flags);
}

static struct dentry *blk_tree_root;
static DEFINE_MUTEX(blk_tree_mutex);

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 blk_trace_cleanup(struct blk_trace *bt)
{
        blk_trace_free(bt);
        if (atomic_dec_and_test(&blk_probes_ref))
                blk_unregister_tracepoints();
}

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;
}
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,
};

static int blk_msg_open(struct inode *inode, struct file *filp)
{
        filp->private_data = inode->i_private;

        return 0;
}

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 = kmalloc(count + 1, GFP_KERNEL);
        if (msg == NULL)
                return -ENOMEM;

        if (copy_from_user(msg, buffer, count)) {
                kfree(msg);
                return -EFAULT;
        }

        msg[count] = '\0';
        bt = filp->private_data;
        __trace_note_message(bt, "%s", msg);
        kfree(msg);

        return count;
}

static const struct file_operations blk_msg_fops = {
        .owner =        THIS_MODULE,
        .open =         blk_msg_open,
        .write =        blk_msg_write,
};

/*
 * 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,
};

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
 */
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 *old_bt, *bt = NULL;
        struct dentry *dir = NULL;
        int ret, i;

        if (!buts->buf_size || !buts->buf_nr)
                return -EINVAL;

        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
         */
        for (i = 0; i < strlen(buts->name); i++)
                if (buts->name[i] == '/')
                        buts->name[i] = '_';

        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;

        mutex_lock(&blk_tree_mutex);
        if (!blk_tree_root) {
                blk_tree_root = debugfs_create_dir("block", NULL);
                if (!blk_tree_root) {
                        mutex_unlock(&blk_tree_mutex);
                        goto err;
                }
        }
        mutex_unlock(&blk_tree_mutex);

        dir = debugfs_create_dir(buts->name, blk_tree_root);

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

        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;
        old_bt = xchg(&q->blk_trace, bt);
        if (old_bt) {
                (void) xchg(&q->blk_trace, old_bt);
                goto err;
        }

        if (atomic_inc_return(&blk_probes_ref) == 1)
                blk_register_tracepoints();

        return 0;
err:
        blk_trace_free(bt);
        return ret;
}

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;
}
EXPORT_SYMBOL_GPL(blk_trace_setup);

int blk_trace_startstop(struct request_queue *q, int start)
{
        int ret;
        struct blk_trace *bt = q->blk_trace;

        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;

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

/*
 * blktrace probes
 */

/**
 * blk_add_trace_rq - Add a trace for a request oriented action
 * @q:          queue the io is for
 * @rq:         the source request
 * @what:       the action
 *
 * Description:
 *     Records an action against a request. Will log the bio offset + size.
 *
 **/
static void blk_add_trace_rq(struct request_queue *q, struct request *rq,
                                    u32 what)
{
        struct blk_trace *bt = q->blk_trace;
        int rw = rq->cmd_flags & 0x03;

        if (likely(!bt))
                return;

        if (blk_discard_rq(rq))
                rw |= (1 << BIO_RW_DISCARD);

        if (blk_pc_request(rq)) {
                what |= BLK_TC_ACT(BLK_TC_PC);
                __blk_add_trace(bt, 0, blk_rq_bytes(rq), rw,
                                what, rq->errors, rq->cmd_len, rq->cmd);
        } else  {
                what |= BLK_TC_ACT(BLK_TC_FS);
                __blk_add_trace(bt, blk_rq_pos(rq), blk_rq_bytes(rq), rw,
                                what, rq->errors, 0, NULL);
        }
}

static void blk_add_trace_rq_abort(struct request_queue *q, struct request *rq)
{
        blk_add_trace_rq(q, rq, BLK_TA_ABORT);
}

static void blk_add_trace_rq_insert(struct request_queue *q, struct request *rq)
{
        blk_add_trace_rq(q, rq, BLK_TA_INSERT);
}

static void blk_add_trace_rq_issue(struct request_queue *q, struct request *rq)
{
        blk_add_trace_rq(q, rq, BLK_TA_ISSUE);
}

static void blk_add_trace_rq_requeue(struct request_queue *q,
                                     struct request *rq)
{
        blk_add_trace_rq(q, rq, BLK_TA_REQUEUE);
}

static void blk_add_trace_rq_complete(struct request_queue *q,
                                      struct request *rq)
{
        blk_add_trace_rq(q, rq, BLK_TA_COMPLETE);
}

/**
 * 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
 *
 * 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)
{
        struct blk_trace *bt = q->blk_trace;

        if (likely(!bt))
                return;

        __blk_add_trace(bt, bio->bi_sector, bio->bi_size, bio->bi_rw, what,
                        !bio_flagged(bio, BIO_UPTODATE), 0, NULL);
}

static void blk_add_trace_bio_bounce(struct request_queue *q, struct bio *bio)
{
        blk_add_trace_bio(q, bio, BLK_TA_BOUNCE);
}

static void blk_add_trace_bio_complete(struct request_queue *q, struct bio *bio)
{
        blk_add_trace_bio(q, bio, BLK_TA_COMPLETE);
}

static void blk_add_trace_bio_backmerge(struct request_queue *q,
                                        struct bio *bio)
{
        blk_add_trace_bio(q, bio, BLK_TA_BACKMERGE);
}

static void blk_add_trace_bio_frontmerge(struct request_queue *q,
                                         struct bio *bio)
{
        blk_add_trace_bio(q, bio, BLK_TA_FRONTMERGE);
}

static void blk_add_trace_bio_queue(struct request_queue *q, struct bio *bio)
{
        blk_add_trace_bio(q, bio, BLK_TA_QUEUE);
}

static void blk_add_trace_getrq(struct request_queue *q,
                                struct bio *bio, int rw)
{
        if (bio)
                blk_add_trace_bio(q, bio, BLK_TA_GETRQ);
        else {
                struct blk_trace *bt = q->blk_trace;

                if (bt)
                        __blk_add_trace(bt, 0, 0, rw, BLK_TA_GETRQ, 0, 0, NULL);
        }
}


static void blk_add_trace_sleeprq(struct request_queue *q,
                                  struct bio *bio, int rw)
{
        if (bio)
                blk_add_trace_bio(q, bio, BLK_TA_SLEEPRQ);
        else {
                struct blk_trace *bt = q->blk_trace;

                if (bt)
                        __blk_add_trace(bt, 0, 0, rw, BLK_TA_SLEEPRQ,
                                        0, 0, NULL);
        }
}

static void blk_add_trace_plug(struct request_queue *q)
{
        struct blk_trace *bt = q->blk_trace;

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

static void blk_add_trace_unplug_io(struct request_queue *q)
{
        struct blk_trace *bt = q->blk_trace;

        if (bt) {
                unsigned int pdu = q->rq.count[READ] + q->rq.count[WRITE];
                __be64 rpdu = cpu_to_be64(pdu);

                __blk_add_trace(bt, 0, 0, 0, BLK_TA_UNPLUG_IO, 0,
                                sizeof(rpdu), &rpdu);
        }
}

static void blk_add_trace_unplug_timer(struct request_queue *q)
{
        struct blk_trace *bt = q->blk_trace;

        if (bt) {
                unsigned int pdu = q->rq.count[READ] + q->rq.count[WRITE];
                __be64 rpdu = cpu_to_be64(pdu);

                __blk_add_trace(bt, 0, 0, 0, BLK_TA_UNPLUG_TIMER, 0,
                                sizeof(rpdu), &rpdu);
        }
}

static void blk_add_trace_split(struct request_queue *q, struct bio *bio,
                                unsigned int pdu)
{
        struct blk_trace *bt = q->blk_trace;

        if (bt) {
                __be64 rpdu = cpu_to_be64(pdu);

                __blk_add_trace(bt, bio->bi_sector, bio->bi_size, bio->bi_rw,
                                BLK_TA_SPLIT, !bio_flagged(bio, BIO_UPTODATE),
                                sizeof(rpdu), &rpdu);
        }
}

/**
 * blk_add_trace_remap - Add a trace for a remap operation
 * @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_remap(struct request_queue *q, struct bio *bio,
                                       dev_t dev, sector_t from)
{
        struct blk_trace *bt = q->blk_trace;
        struct blk_io_trace_remap r;

        if (likely(!bt))
                return;

        r.device_from = cpu_to_be32(dev);
        r.device_to   = cpu_to_be32(bio->bi_bdev->bd_dev);
        r.sector_from = cpu_to_be64(from);

        __blk_add_trace(bt, bio->bi_sector, bio->bi_size, bio->bi_rw,
                        BLK_TA_REMAP, !bio_flagged(bio, BIO_UPTODATE),
                        sizeof(r), &r);
}

/**
 * blk_add_trace_rq_remap - Add a trace for a request-remap operation
 * @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(struct request_queue *q,
                                   struct request *rq, dev_t dev,
                                   sector_t from)
{
        struct blk_trace *bt = q->blk_trace;
        struct blk_io_trace_remap r;

        if (likely(!bt))
                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), BLK_TA_REMAP, !!rq->errors,
                        sizeof(r), &r);
}

/**
 * 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 = q->blk_trace;

        if (likely(!bt))
                return;

        if (blk_pc_request(rq))
                __blk_add_trace(bt, 0, blk_rq_bytes(rq), 0,
                                BLK_TA_DRV_DATA, rq->errors, len, data);
        else
                __blk_add_trace(bt, blk_rq_pos(rq), blk_rq_bytes(rq), 0,
                                BLK_TA_DRV_DATA, rq->errors, len, data);
}
EXPORT_SYMBOL_GPL(blk_add_driver_data);

static void blk_register_tracepoints(void)
{
        int ret;

        ret = register_trace_block_rq_abort(blk_add_trace_rq_abort);
        WARN_ON(ret);
        ret = register_trace_block_rq_insert(blk_add_trace_rq_insert);
        WARN_ON(ret);
        ret = register_trace_block_rq_issue(blk_add_trace_rq_issue);
        WARN_ON(ret);
        ret = register_trace_block_rq_requeue(blk_add_trace_rq_requeue);
        WARN_ON(ret);
        ret = register_trace_block_rq_complete(blk_add_trace_rq_complete);
        WARN_ON(ret);
        ret = register_trace_block_bio_bounce(blk_add_trace_bio_bounce);
        WARN_ON(ret);
        ret = register_trace_block_bio_complete(blk_add_trace_bio_complete);
        WARN_ON(ret);
        ret = register_trace_block_bio_backmerge(blk_add_trace_bio_backmerge);
        WARN_ON(ret);
        ret = register_trace_block_bio_frontmerge(blk_add_trace_bio_frontmerge);
        WARN_ON(ret);
        ret = register_trace_block_bio_queue(blk_add_trace_bio_queue);
        WARN_ON(ret);
        ret = register_trace_block_getrq(blk_add_trace_getrq);
        WARN_ON(ret);
        ret = register_trace_block_sleeprq(blk_add_trace_sleeprq);
        WARN_ON(ret);
        ret = register_trace_block_plug(blk_add_trace_plug);
        WARN_ON(ret);
        ret = register_trace_block_unplug_timer(blk_add_trace_unplug_timer);
        WARN_ON(ret);
        ret = register_trace_block_unplug_io(blk_add_trace_unplug_io);
        WARN_ON(ret);
        ret = register_trace_block_split(blk_add_trace_split);
        WARN_ON(ret);
        ret = register_trace_block_remap(blk_add_trace_remap);
        WARN_ON(ret);
        ret = register_trace_block_rq_remap(blk_add_trace_rq_remap);
        WARN_ON(ret);
}

static void blk_unregister_tracepoints(void)
{
        unregister_trace_block_rq_remap(blk_add_trace_rq_remap);
        unregister_trace_block_remap(blk_add_trace_remap);
        unregister_trace_block_split(blk_add_trace_split);
        unregister_trace_block_unplug_io(blk_add_trace_unplug_io);
        unregister_trace_block_unplug_timer(blk_add_trace_unplug_timer);
        unregister_trace_block_plug(blk_add_trace_plug);
        unregister_trace_block_sleeprq(blk_add_trace_sleeprq);
        unregister_trace_block_getrq(blk_add_trace_getrq);
        unregister_trace_block_bio_queue(blk_add_trace_bio_queue);
        unregister_trace_block_bio_frontmerge(blk_add_trace_bio_frontmerge);
        unregister_trace_block_bio_backmerge(blk_add_trace_bio_backmerge);
        unregister_trace_block_bio_complete(blk_add_trace_bio_complete);
        unregister_trace_block_bio_bounce(blk_add_trace_bio_bounce);
        unregister_trace_block_rq_complete(blk_add_trace_rq_complete);
        unregister_trace_block_rq_requeue(blk_add_trace_rq_requeue);
        unregister_trace_block_rq_issue(blk_add_trace_rq_issue);
        unregister_trace_block_rq_insert(blk_add_trace_rq_insert);
        unregister_trace_block_rq_abort(blk_add_trace_rq_abort);

        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_MESSAGE) {
                rwbs[i++] = 'N';
                goto out;
        }

        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_AHEAD)
                rwbs[i++] = 'A';
        if (tc & BLK_TC_BARRIER)
                rwbs[i++] = 'B';
        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)
{
        return te_blk_io_trace(ent) + 1;
}

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)
{
        const __u64 *val = pdu_start(ent);
        return be64_to_cpu(*val);
}

static void get_pdu_remap(const struct trace_entry *ent,
                          struct blk_io_trace_remap *r)
{
        const struct blk_io_trace_remap *__r = pdu_start(ent);
        __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 int (blk_log_action_t) (struct trace_iterator *iter, const char *act);

static int blk_log_action_classic(struct trace_iterator *iter, const char *act)
{
        char rwbs[6];
        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);

        return 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 int blk_log_action(struct trace_iterator *iter, const char *act)
{
        char rwbs[6];
        const struct blk_io_trace *t = te_blk_io_trace(iter->ent);

        fill_rwbs(rwbs, t);
        return trace_seq_printf(&iter->seq, "%3d,%-3d %2s %3s ",
                                MAJOR(t->device), MINOR(t->device), act, rwbs);
}

static int blk_log_dump_pdu(struct trace_seq *s, const struct trace_entry *ent)
{
        const unsigned char *pdu_buf;
        int pdu_len;
        int i, end, ret;

        pdu_buf = pdu_start(ent);
        pdu_len = te_blk_io_trace(ent)->pdu_len;

        if (!pdu_len)
                return 1;

        /* find the last zero that needs to be printed */
        for (end = pdu_len - 1; end >= 0; end--)
                if (pdu_buf[end])
                        break;
        end++;

        if (!trace_seq_putc(s, '('))
                return 0;

        for (i = 0; i < pdu_len; i++) {

                ret = trace_seq_printf(s, "%s%02x",
                                       i == 0 ? "" : " ", pdu_buf[i]);
                if (!ret)
                        return ret;

                /*
                 * stop when the rest is just zeroes and indicate so
                 * with a ".." appended
                 */
                if (i == end && end != pdu_len - 1)
                        return trace_seq_puts(s, " ..) ");
        }

        return trace_seq_puts(s, ") ");
}

static int blk_log_generic(struct trace_seq *s, const struct trace_entry *ent)
{
        char cmd[TASK_COMM_LEN];

        trace_find_cmdline(ent->pid, cmd);

        if (t_action(ent) & BLK_TC_ACT(BLK_TC_PC)) {
                int ret;

                ret = trace_seq_printf(s, "%u ", t_bytes(ent));
                if (!ret)
                        return 0;
                ret = blk_log_dump_pdu(s, ent);
                if (!ret)
                        return 0;
                return trace_seq_printf(s, "[%s]\n", cmd);
        } else {
                if (t_sec(ent))
                        return trace_seq_printf(s, "%llu + %u [%s]\n",
                                                t_sector(ent), t_sec(ent), cmd);
                return trace_seq_printf(s, "[%s]\n", cmd);
        }
}

static int blk_log_with_error(struct trace_seq *s,
                              const struct trace_entry *ent)
{
        if (t_action(ent) & BLK_TC_ACT(BLK_TC_PC)) {
                int ret;

                ret = blk_log_dump_pdu(s, ent);
                if (ret)
                        return trace_seq_printf(s, "[%d]\n", t_error(ent));
                return 0;
        } else {
                if (t_sec(ent))
                        return trace_seq_printf(s, "%llu + %u [%d]\n",
                                                t_sector(ent),
                                                t_sec(ent), t_error(ent));
                return trace_seq_printf(s, "%llu [%d]\n",
                                        t_sector(ent), t_error(ent));
        }
}

static int blk_log_remap(struct trace_seq *s, const struct trace_entry *ent)
{
        struct blk_io_trace_remap r = { .device_from = 0, };

        get_pdu_remap(ent, &r);
        return trace_seq_printf(s, "%llu + %u <- (%d,%d) %llu\n",
                                t_sector(ent), t_sec(ent),
                                MAJOR(r.device_from), MINOR(r.device_from),
                                (unsigned long long)r.sector_from);
}

static int blk_log_plug(struct trace_seq *s, const struct trace_entry *ent)
{
        char cmd[TASK_COMM_LEN];

        trace_find_cmdline(ent->pid, cmd);

        return trace_seq_printf(s, "[%s]\n", cmd);
}

static int blk_log_unplug(struct trace_seq *s, const struct trace_entry *ent)
{
        char cmd[TASK_COMM_LEN];

        trace_find_cmdline(ent->pid, cmd);

        return trace_seq_printf(s, "[%s] %llu\n", cmd, get_pdu_int(ent));
}

static int blk_log_split(struct trace_seq *s, const struct trace_entry *ent)
{
        char cmd[TASK_COMM_LEN];

        trace_find_cmdline(ent->pid, cmd);

        return trace_seq_printf(s, "%llu / %llu [%s]\n", t_sector(ent),
                                get_pdu_int(ent), cmd);
}

static int blk_log_msg(struct trace_seq *s, const struct trace_entry *ent)
{
        int ret;
        const struct blk_io_trace *t = te_blk_io_trace(ent);

        ret = trace_seq_putmem(s, t + 1, t->pdu_len);
        if (ret)
                return trace_seq_putc(s, '\n');
        return ret;
}

/*
 * struct tracer operations
 */

static void blk_tracer_print_header(struct seq_file *m)
{
        if (!(blk_tracer_flags.val & TRACE_BLK_OPT_CLASSIC))
                return;
        seq_puts(m, "# DEV   CPU TIMESTAMP     PID ACT FLG\n"
                    "#  |     |     |           |   |   |\n");
}

static void blk_tracer_start(struct trace_array *tr)
{
        blk_tracer_enabled = true;
}

static int blk_tracer_init(struct trace_array *tr)
{
        blk_tr = tr;
        blk_tracer_start(tr);
        return 0;
}

static void blk_tracer_stop(struct trace_array *tr)
{
        blk_tracer_enabled = false;
}

static void blk_tracer_reset(struct trace_array *tr)
{
        blk_tracer_stop(tr);
}

static const struct {
        const char *act[2];
        int        (*print)(struct trace_seq *s, const struct trace_entry *ent);
} what2act[] = {
        [__BLK_TA_QUEUE]        = {{  "Q", "queue" },      blk_log_generic },
        [__BLK_TA_BACKMERGE]    = {{  "M", "backmerge" },  blk_log_generic },
        [__BLK_TA_FRONTMERGE]   = {{  "F", "frontmerge" }, blk_log_generic },
        [__BLK_TA_GETRQ]        = {{  "G", "getrq" },      blk_log_generic },
        [__BLK_TA_SLEEPRQ]      = {{  "S", "sleeprq" },    blk_log_generic },
        [__BLK_TA_REQUEUE]      = {{  "R", "requeue" },    blk_log_with_error },
        [__BLK_TA_ISSUE]        = {{  "D", "issue" },      blk_log_generic },
        [__BLK_TA_COMPLETE]     = {{  "C", "complete" },   blk_log_with_error },
        [__BLK_TA_PLUG]         = {{  "P", "plug" },       blk_log_plug },
        [__BLK_TA_UNPLUG_IO]    = {{  "U", "unplug_io" },  blk_log_unplug },
        [__BLK_TA_UNPLUG_TIMER] = {{ "UT", "unplug_timer" }, blk_log_unplug },
        [__BLK_TA_INSERT]       = {{  "I", "insert" },     blk_log_generic },
        [__BLK_TA_SPLIT]        = {{  "X", "split" },      blk_log_split },
        [__BLK_TA_BOUNCE]       = {{  "B", "bounce" },     blk_log_generic },
        [__BLK_TA_REMAP]        = {{  "A", "remap" },      blk_log_remap },
};

static enum print_line_t print_one_line(struct trace_iterator *iter,
                                        bool classic)
{
        struct trace_seq *s = &iter->seq;
        const struct blk_io_trace *t;
        u16 what;
        int ret;
        bool long_act;
        blk_log_action_t *log_action;

        t          = te_blk_io_trace(iter->ent);
        what       = t->action & ((1 << BLK_TC_SHIFT) - 1);
        long_act   = !!(trace_flags & TRACE_ITER_VERBOSE);
        log_action = classic ? &blk_log_action_classic : &blk_log_action;

        if (t->action == BLK_TN_MESSAGE) {
                ret = log_action(iter, long_act ? "message" : "m");
                if (ret)
                        ret = blk_log_msg(s, iter->ent);
                goto out;
        }

        if (unlikely(what == 0 || what >= ARRAY_SIZE(what2act)))
                ret = trace_seq_printf(s, "Unknown action %x\n", what);
        else {
                ret = log_action(iter, what2act[what].act[long_act]);
                if (ret)
                        ret = what2act[what].print(s, iter->ent);
        }
out:
        return ret ? TRACE_TYPE_HANDLED : TRACE_TYPE_PARTIAL_LINE;
}

static enum print_line_t blk_trace_event_print(struct trace_iterator *iter,
                                               int flags)
{
        return print_one_line(iter, false);
}

static int blk_trace_synthesize_old_trace(struct trace_iterator *iter)
{
        struct trace_seq *s = &iter->seq;
        struct blk_io_trace *t = (struct blk_io_trace *)iter->ent;
        const int offset = offsetof(struct blk_io_trace, sector);
        struct blk_io_trace old = {
                .magic    = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION,
                .time     = iter->ts,
        };

        if (!trace_seq_putmem(s, &old, offset))
                return 0;
        return trace_seq_putmem(s, &t->sector,
                                sizeof(old) - offset + t->pdu_len);
}

static enum print_line_t
blk_trace_event_print_binary(struct trace_iterator *iter, int flags)
{
        return blk_trace_synthesize_old_trace(iter) ?
                        TRACE_TYPE_HANDLED : TRACE_TYPE_PARTIAL_LINE;
}

static enum print_line_t blk_tracer_print_line(struct trace_iterator *iter)
{
        if (!(blk_tracer_flags.val & TRACE_BLK_OPT_CLASSIC))
                return TRACE_TYPE_UNHANDLED;

        return print_one_line(iter, true);
}

static int blk_tracer_set_flag(u32 old_flags, u32 bit, int set)
{
        /* don't output context-info for blk_classic output */
        if (bit == TRACE_BLK_OPT_CLASSIC) {
                if (set)
                        trace_flags &= ~TRACE_ITER_CONTEXT_INFO;
                else
                        trace_flags |= TRACE_ITER_CONTEXT_INFO;
        }
        return 0;
}

static struct tracer blk_tracer __read_mostly = {
        .name           = "blk",
        .init           = blk_tracer_init,
        .reset          = blk_tracer_reset,
        .start          = blk_tracer_start,
        .stop           = blk_tracer_stop,
        .print_header   = blk_tracer_print_header,
        .print_line     = blk_tracer_print_line,
        .flags          = &blk_tracer_flags,
        .set_flag       = blk_tracer_set_flag,
};

static struct trace_event trace_blk_event = {
        .type           = TRACE_BLK,
        .trace          = blk_trace_event_print,
        .binary         = blk_trace_event_print_binary,
};

static int __init init_blk_tracer(void)
{
        if (!register_ftrace_event(&trace_blk_event)) {
                pr_warning("Warning: could not register block events\n");
                return 1;
        }

        if (register_tracer(&blk_tracer) != 0) {
                pr_warning("Warning: could not register the block tracer\n");
                unregister_ftrace_event(&trace_blk_event);
                return 1;
        }

        return 0;
}

device_initcall(init_blk_tracer);

static int blk_trace_remove_queue(struct request_queue *q)
{
        struct blk_trace *bt;

        bt = xchg(&q->blk_trace, NULL);
        if (bt == NULL)
                return -EINVAL;

        if (atomic_dec_and_test(&blk_probes_ref))
                blk_unregister_tracepoints();

        blk_trace_free(bt);
        return 0;
}

/*
 * Setup everything required to start tracing
 */
static int blk_trace_setup_queue(struct request_queue *q,
                                 struct block_device *bdev)
{
        struct blk_trace *old_bt, *bt = NULL;
        int ret = -ENOMEM;

        bt = kzalloc(sizeof(*bt), GFP_KERNEL);
        if (!bt)
                return -ENOMEM;

        bt->msg_data = __alloc_percpu(BLK_TN_MAX_MSG, __alignof__(char));
        if (!bt->msg_data)
                goto free_bt;

        bt->dev = bdev->bd_dev;
        bt->act_mask = (u16)-1;

        blk_trace_setup_lba(bt, bdev);

        old_bt = xchg(&q->blk_trace, bt);
        if (old_bt != NULL) {
                (void)xchg(&q->blk_trace, old_bt);
                ret = -EBUSY;
                goto free_bt;
        }

        if (atomic_inc_return(&blk_probes_ref) == 1)
                blk_register_tracepoints();
        return 0;

free_bt:
        blk_trace_free(bt);
        return ret;
}

/*
 * sysfs interface to enable and configure tracing
 */

static ssize_t sysfs_blk_trace_attr_show(struct device *dev,
                                         struct device_attribute *attr,
                                         char *buf);
static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
                                          struct device_attribute *attr,
                                          const char *buf, size_t count);
#define BLK_TRACE_DEVICE_ATTR(_name) \
        DEVICE_ATTR(_name, S_IRUGO | S_IWUSR, \
                    sysfs_blk_trace_attr_show, \
                    sysfs_blk_trace_attr_store)

static BLK_TRACE_DEVICE_ATTR(enable);
static BLK_TRACE_DEVICE_ATTR(act_mask);
static BLK_TRACE_DEVICE_ATTR(pid);
static BLK_TRACE_DEVICE_ATTR(start_lba);
static BLK_TRACE_DEVICE_ATTR(end_lba);

static struct attribute *blk_trace_attrs[] = {
        &dev_attr_enable.attr,
        &dev_attr_act_mask.attr,
        &dev_attr_pid.attr,
        &dev_attr_start_lba.attr,
        &dev_attr_end_lba.attr,
        NULL
};

struct attribute_group blk_trace_attr_group = {
        .name  = "trace",
        .attrs = blk_trace_attrs,
};

static const struct {
        int mask;
        const char *str;
} mask_maps[] = {
        { BLK_TC_READ,          "read"          },
        { BLK_TC_WRITE,         "write"         },
        { BLK_TC_BARRIER,       "barrier"       },
        { BLK_TC_SYNC,          "sync"          },
        { BLK_TC_QUEUE,         "queue"         },
        { BLK_TC_REQUEUE,       "requeue"       },
        { BLK_TC_ISSUE,         "issue"         },
        { BLK_TC_COMPLETE,      "complete"      },
        { BLK_TC_FS,            "fs"            },
        { BLK_TC_PC,            "pc"            },
        { BLK_TC_AHEAD,         "ahead"         },
        { BLK_TC_META,          "meta"          },
        { BLK_TC_DISCARD,       "discard"       },
        { BLK_TC_DRV_DATA,      "drv_data"      },
};

static int blk_trace_str2mask(const char *str)
{
        int i;
        int mask = 0;
        char *buf, *s, *token;

        buf = kstrdup(str, GFP_KERNEL);
        if (buf == NULL)
                return -ENOMEM;
        s = strstrip(buf);

        while (1) {
                token = strsep(&s, ",");
                if (token == NULL)
                        break;

                if (*token == '\0')
                        continue;

                for (i = 0; i < ARRAY_SIZE(mask_maps); i++) {
                        if (strcasecmp(token, mask_maps[i].str) == 0) {
                                mask |= mask_maps[i].mask;
                                break;
                        }
                }
                if (i == ARRAY_SIZE(mask_maps)) {
                        mask = -EINVAL;
                        break;
                }
        }
        kfree(buf);

        return mask;
}

static ssize_t blk_trace_mask2str(char *buf, int mask)
{
        int i;
        char *p = buf;

        for (i = 0; i < ARRAY_SIZE(mask_maps); i++) {
                if (mask & mask_maps[i].mask) {
                        p += sprintf(p, "%s%s",
                                    (p == buf) ? "" : ",", mask_maps[i].str);
                }
        }
        *p++ = '\n';

        return p - buf;
}

static struct request_queue *blk_trace_get_queue(struct block_device *bdev)
{
        if (bdev->bd_disk == NULL)
                return NULL;

        return bdev_get_queue(bdev);
}

static ssize_t sysfs_blk_trace_attr_show(struct device *dev,
                                         struct device_attribute *attr,
                                         char *buf)
{
        struct hd_struct *p = dev_to_part(dev);
        struct request_queue *q;
        struct block_device *bdev;
        ssize_t ret = -ENXIO;

        lock_kernel();
        bdev = bdget(part_devt(p));
        if (bdev == NULL)
                goto out_unlock_kernel;

        q = blk_trace_get_queue(bdev);
        if (q == NULL)
                goto out_bdput;

        mutex_lock(&bdev->bd_mutex);

        if (attr == &dev_attr_enable) {
                ret = sprintf(buf, "%u\n", !!q->blk_trace);
                goto out_unlock_bdev;
        }

        if (q->blk_trace == NULL)
                ret = sprintf(buf, "disabled\n");
        else if (attr == &dev_attr_act_mask)
                ret = blk_trace_mask2str(buf, q->blk_trace->act_mask);
        else if (attr == &dev_attr_pid)
                ret = sprintf(buf, "%u\n", q->blk_trace->pid);
        else if (attr == &dev_attr_start_lba)
                ret = sprintf(buf, "%llu\n", q->blk_trace->start_lba);
        else if (attr == &dev_attr_end_lba)
                ret = sprintf(buf, "%llu\n", q->blk_trace->end_lba);

out_unlock_bdev:
        mutex_unlock(&bdev->bd_mutex);
out_bdput:
        bdput(bdev);
out_unlock_kernel:
        unlock_kernel();
        return ret;
}

static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
                                          struct device_attribute *attr,
                                          const char *buf, size_t count)
{
        struct block_device *bdev;
        struct request_queue *q;
        struct hd_struct *p;
        u64 value;
        ssize_t ret = -EINVAL;

        if (count == 0)
                goto out;

        if (attr == &dev_attr_act_mask) {
                if (sscanf(buf, "%llx", &value) != 1) {
                        /* Assume it is a list of trace category names */
                        ret = blk_trace_str2mask(buf);
                        if (ret < 0)
                                goto out;
                        value = ret;
                }
        } else if (sscanf(buf, "%llu", &value) != 1)
                goto out;

        ret = -ENXIO;

        lock_kernel();
        p = dev_to_part(dev);
        bdev = bdget(part_devt(p));
        if (bdev == NULL)
                goto out_unlock_kernel;

        q = blk_trace_get_queue(bdev);
        if (q == NULL)
                goto out_bdput;

        mutex_lock(&bdev->bd_mutex);

        if (attr == &dev_attr_enable) {
                if (value)
                        ret = blk_trace_setup_queue(q, bdev);
                else
                        ret = blk_trace_remove_queue(q);
                goto out_unlock_bdev;
        }

        ret = 0;
        if (q->blk_trace == NULL)
                ret = blk_trace_setup_queue(q, bdev);

        if (ret == 0) {
                if (attr == &dev_attr_act_mask)
                        q->blk_trace->act_mask = value;
                else if (attr == &dev_attr_pid)
                        q->blk_trace->pid = value;
                else if (attr == &dev_attr_start_lba)
                        q->blk_trace->start_lba = value;
                else if (attr == &dev_attr_end_lba)
                        q->blk_trace->end_lba = value;
        }

out_unlock_bdev:
        mutex_unlock(&bdev->bd_mutex);
out_bdput:
        bdput(bdev);
out_unlock_kernel:
        unlock_kernel();
out:
        return ret ? ret : count;
}

int blk_trace_init_sysfs(struct device *dev)
{
        return sysfs_create_group(&dev->kobj, &blk_trace_attr_group);
}

void blk_trace_remove_sysfs(struct device *dev)
{
        sysfs_remove_group(&dev->kobj, &blk_trace_attr_group);
}

#endif /* CONFIG_BLK_DEV_IO_TRACE */

#ifdef CONFIG_EVENT_TRACING

void blk_dump_cmd(char *buf, struct request *rq)
{
        int i, end;
        int len = rq->cmd_len;
        unsigned char *cmd = rq->cmd;

        if (!blk_pc_request(rq)) {
                buf[0] = '\0';
                return;
        }

        for (end = len - 1; end >= 0; end--)
                if (cmd[end])
                        break;
        end++;

        for (i = 0; i < len; i++) {
                buf += sprintf(buf, "%s%02x", i == 0 ? "" : " ", cmd[i]);
                if (i == end && end != len - 1) {
                        sprintf(buf, " ..");
                        break;
                }
        }
}

void blk_fill_rwbs(char *rwbs, u32 rw, int bytes)
{
        int i = 0;

        if (rw & WRITE)
                rwbs[i++] = 'W';
        else if (rw & 1 << BIO_RW_DISCARD)
                rwbs[i++] = 'D';
        else if (bytes)
                rwbs[i++] = 'R';
        else
                rwbs[i++] = 'N';

        if (rw & 1 << BIO_RW_AHEAD)
                rwbs[i++] = 'A';
        if (rw & 1 << BIO_RW_BARRIER)
                rwbs[i++] = 'B';
        if (rw & 1 << BIO_RW_SYNCIO)
                rwbs[i++] = 'S';
        if (rw & 1 << BIO_RW_META)
                rwbs[i++] = 'M';

        rwbs[i] = '\0';
}

void blk_fill_rwbs_rq(char *rwbs, struct request *rq)
{
        int rw = rq->cmd_flags & 0x03;
        int bytes;

        if (blk_discard_rq(rq))
                rw |= (1 << BIO_RW_DISCARD);

        bytes = blk_rq_bytes(rq);

        blk_fill_rwbs(rwbs, rw, bytes);
}

#endif /* CONFIG_EVENT_TRACING */