Merge commit 'v2.6.30-rc1' into core/urgent

Merge reason: need latest upstream to queue up dependent fix

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 1550 insertions, 0 deletions

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
new file mode 100644
index 000000000000..b32ff446c3fb
--- /dev/null
+++ b/kernel/trace/blktrace.c
@@ -0,0 +1,1550 @@
+/*
+ * 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 <trace/block.h>
+#include <linux/uaccess.h>
+#include "trace_output.h"
+
+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;
+        int pc = 0;
+        int cpu = smp_processor_id();
+        bool blk_tracer = blk_tracer_enabled;
+
+        if (blk_tracer) {
+                pc = preempt_count();
+                event = trace_buffer_lock_reserve(blk_tr, 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(blk_tr, 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 < 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 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 (unlikely(act_log_check(bt, what, sector, pid)))
+                return;
+        cpu = raw_smp_processor_id();
+
+        if (blk_tracer) {
+                tracing_record_cmdline(current);
+
+                pc = preempt_count();
+                event = trace_buffer_lock_reserve(blk_tr, 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(blk_tr, 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);
+        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)
+{
+        struct dentry *parent = dentry->d_parent;
+        debugfs_remove(dentry);
+
+        /*
+        * this will fail for all but the last file, but that is ok. what we
+        * care about is the top level buts->name directory going away, when
+        * the last trace file is gone. Then we don't have to rmdir() that
+        * manually on trace stop, so it nicely solves the issue with
+        * force killing of running traces.
+        */
+
+        debugfs_remove(parent);
+        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;
+
+        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;
+
+        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;
+        }
+
+        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,
+                    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)
+{
+        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, 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, rq->data_len, rw, what, rq->errors,
+                                rq->cmd_len, rq->cmd);
+        } else  {
+                what |= BLK_TC_ACT(BLK_TC_FS);
+                __blk_add_trace(bt, rq->hard_sector, rq->hard_nr_sectors << 9,
+                                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
+ * @to:         target 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, sector_t to)
+{
+        struct blk_trace *bt = q->blk_trace;
+        struct blk_io_trace_remap r;
+
+        if (likely(!bt))
+                return;
+
+        r.device = cpu_to_be32(dev);
+        r.device_from = cpu_to_be32(bio->bi_bdev->bd_dev);
+        r.sector = cpu_to_be64(to);
+
+        __blk_add_trace(bt, from, bio->bi_size, bio->bi_rw, BLK_TA_REMAP,
+                        !bio_flagged(bio, BIO_UPTODATE), 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, rq->data_len, 0, BLK_TA_DRV_DATA,
+                                rq->errors, len, data);
+        else
+                __blk_add_trace(bt, rq->hard_sector, rq->hard_nr_sectors << 9,
+                                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);
+}
+
+static void blk_unregister_tracepoints(void)
+{
+        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_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 = __r->sector;
+
+        r->device = be32_to_cpu(__r->device);
+        r->device_from = be32_to_cpu(__r->device_from);
+        r->sector = be64_to_cpu(sector);
+}
+
+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_generic(struct trace_seq *s, const struct trace_entry *ent)
+{
+        char cmd[TASK_COMM_LEN];
+
+        trace_find_cmdline(ent->pid, cmd);
+
+        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_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 = 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), MINOR(r.device),
+                               (unsigned long long)r.sector);
+}
+
+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;
+        trace_flags &= ~TRACE_ITER_CONTEXT_INFO;
+}
+
+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;
+        trace_flags |= TRACE_ITER_CONTEXT_INFO;
+}
+
+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, "Bad pc 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)
+{
+        if (!trace_print_context(iter))
+                return TRACE_TYPE_PARTIAL_LINE;
+
+        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 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,
+};
+
+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, dev_t dev)
+{
+        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 = dev;
+        bt->act_mask = (u16)-1;
+        bt->end_lba = -1ULL;
+
+        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 *s, *token;
+
+        s = kstrdup(str, GFP_KERNEL);
+        if (s == NULL)
+                return -ENOMEM;
+        s = strstrip(s);
+
+        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(s);
+
+        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->bd_dev);
+                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->bd_dev);
+
+        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;
+}
+