1 files changed, 651 insertions, 5 deletions

diff --git a/block/blktrace.c b/block/blktrace.c
index 39cc3bfe56e4..3f25425ade12 100644
--- a/block/blktrace.c
+++ b/block/blktrace.c
@@ -25,9 +25,27 @@
 #include <linux/time.h>
 #include <trace/block.h>
 #include <asm/uaccess.h>
+#include <../kernel/trace/trace_output.h>
 
 static unsigned int blktrace_seq __read_mostly = 1;
 
+static struct trace_array *blk_tr;
+static int __read_mostly  blk_tracer_enabled;
+
+/* 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 DEFINE_MUTEX(blk_probe_mutex);
 static atomic_t blk_probes_ref = ATOMIC_INIT(0);
@@ -43,6 +61,9 @@ static void trace_note(struct blk_trace *bt, pid_t pid, int action,
 {
         struct blk_io_trace *t;
 
+        if (!bt->rchan)
+                return;
+
         t = relay_reserve(bt->rchan, sizeof(*t) + len);
         if (t) {
                 const int cpu = smp_processor_id();
@@ -90,6 +111,16 @@ void __trace_note_message(struct blk_trace *bt, const char *fmt, ...)
         unsigned long flags;
         char *buf;
 
+        if (blk_tr) {
+                va_start(args, fmt);
+                ftrace_vprintk(fmt, args);
+                va_end(args);
+                return;
+        }
+
+        if (!bt->msg_data)
+                return;
+
         local_irq_save(flags);
         buf = per_cpu_ptr(bt->msg_data, smp_processor_id());
         va_start(args, fmt);
@@ -131,13 +162,15 @@ 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;
         unsigned long *sequence;
         pid_t pid;
-        int cpu;
+        int cpu, pc = 0;
 
-        if (unlikely(bt->trace_state != Blktrace_running))
+        if (unlikely(bt->trace_state != Blktrace_running ||
+                     !blk_tracer_enabled))
                 return;
 
         what |= ddir_act[rw & WRITE];
@@ -150,6 +183,24 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
         pid = tsk->pid;
         if (unlikely(act_log_check(bt, what, sector, pid)))
                 return;
+        cpu = raw_smp_processor_id();
+
+        if (blk_tr) {
+                struct trace_entry *ent;
+                tracing_record_cmdline(current);
+
+                event = ring_buffer_lock_reserve(blk_tr->buffer,
+                                                 sizeof(*t) + pdu_len, &flags);
+                if (!event)
+                        return;
+
+                ent = ring_buffer_event_data(event);
+                t = (struct blk_io_trace *)ent;
+                pc = preempt_count();
+                tracing_generic_entry_update(ent, 0, pc);
+                ent->type = TRACE_BLK;
+                goto record_it;
+        }
 
         /*
          * A word about the locking here - we disable interrupts to reserve
@@ -163,23 +214,33 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
 
         t = relay_reserve(bt->rchan, sizeof(*t) + pdu_len);
         if (t) {
-                cpu = smp_processor_id();
                 sequence = per_cpu_ptr(bt->sequence, cpu);
 
                 t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
                 t->sequence = ++(*sequence);
                 t->time = ktime_to_ns(ktime_get());
+                t->cpu = cpu;
+                t->pid = pid;
+record_it:
                 t->sector = sector;
                 t->bytes = bytes;
                 t->action = what;
-                t->pid = pid;
                 t->device = bt->dev;
-                t->cpu = cpu;
                 t->error = error;
                 t->pdu_len = pdu_len;
 
                 if (pdu_len)
                         memcpy((void *) t + sizeof(*t), pdu_data, pdu_len);
+
+                if (blk_tr) {
+                        ring_buffer_unlock_commit(blk_tr->buffer, event, flags);
+                        if (pid != 0 &&
+                            !(blk_tracer_flags.val & TRACE_BLK_OPT_CLASSIC) &&
+                            (trace_flags & TRACE_ITER_STACKTRACE) != 0)
+                                __trace_stack(blk_tr, NULL, flags, 5, pc);
+                        trace_wake_up();
+                        return;
+                }
         }
 
         local_irq_restore(flags);
@@ -858,3 +919,588 @@ static void blk_unregister_tracepoints(void)
 
         tracepoint_synchronize_unregister();
 }
+
+/*
+ * struct blk_io_tracer formatting routines
+ */
+
+static void fill_rwbs(char *rwbs, const struct blk_io_trace *t)
+{
+        int i = 0;
+
+        if (t->action & BLK_TC_DISCARD)
+                rwbs[i++] = 'D';
+        else if (t->action & BLK_TC_WRITE)
+                rwbs[i++] = 'W';
+        else if (t->bytes)
+                rwbs[i++] = 'R';
+        else
+                rwbs[i++] = 'N';
+
+        if (t->action & BLK_TC_AHEAD)
+                rwbs[i++] = 'A';
+        if (t->action & BLK_TC_BARRIER)
+                rwbs[i++] = 'B';
+        if (t->action & BLK_TC_SYNC)
+                rwbs[i++] = 'S';
+        if (t->action & BLK_TC_META)
+                rwbs[i++] = 'M';
+
+        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)->sector;
+}
+
+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);
+}
+
+static int blk_log_action_iter(struct trace_iterator *iter, const char *act)
+{
+        char rwbs[6];
+        unsigned long long ts  = ns2usecs(iter->ts);
+        unsigned long usec_rem = do_div(ts, USEC_PER_SEC);
+        unsigned secs          = (unsigned long)ts;
+        const struct trace_entry *ent = iter->ent;
+        const struct blk_io_trace *t = (const struct blk_io_trace *)ent;
+
+        fill_rwbs(rwbs, t);
+
+        return trace_seq_printf(&iter->seq,
+                                "%3d,%-3d %2d %5d.%06lu %5u %2s %3s ",
+                                MAJOR(t->device), MINOR(t->device), iter->cpu,
+                                secs, usec_rem, ent->pid, act, rwbs);
+}
+
+static int blk_log_action_seq(struct trace_seq *s, const struct blk_io_trace *t,
+                              const char *act)
+{
+        char rwbs[6];
+        fill_rwbs(rwbs, t);
+        return trace_seq_printf(s, "%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)
+{
+        const char *cmd = trace_find_cmdline(ent->pid);
+
+        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)
+{
+        return trace_seq_printf(s, "[%s]\n", trace_find_cmdline(ent->pid));
+}
+
+static int blk_log_unplug(struct trace_seq *s, const struct trace_entry *ent)
+{
+        return trace_seq_printf(s, "[%s] %llu\n", trace_find_cmdline(ent->pid),
+                                get_pdu_int(ent));
+}
+
+static int blk_log_split(struct trace_seq *s, const struct trace_entry *ent)
+{
+        return trace_seq_printf(s, "%llu / %llu [%s]\n", t_sector(ent),
+                                get_pdu_int(ent), trace_find_cmdline(ent->pid));
+}
+
+/*
+ * 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)
+{
+        tracing_reset_online_cpus(tr);
+
+        mutex_lock(&blk_probe_mutex);
+        if (atomic_add_return(1, &blk_probes_ref) == 1)
+                if (blk_register_tracepoints())
+                        atomic_dec(&blk_probes_ref);
+        mutex_unlock(&blk_probe_mutex);
+}
+
+static int blk_tracer_init(struct trace_array *tr)
+{
+        blk_tr = tr;
+        blk_tracer_start(tr);
+        mutex_lock(&blk_probe_mutex);
+        blk_tracer_enabled++;
+        mutex_unlock(&blk_probe_mutex);
+        return 0;
+}
+
+static void blk_tracer_stop(struct trace_array *tr)
+{
+        mutex_lock(&blk_probe_mutex);
+        if (atomic_dec_and_test(&blk_probes_ref))
+                blk_unregister_tracepoints();
+        mutex_unlock(&blk_probe_mutex);
+}
+
+static void blk_tracer_reset(struct trace_array *tr)
+{
+        if (!atomic_read(&blk_probes_ref))
+                return;
+
+        mutex_lock(&blk_probe_mutex);
+        blk_tracer_enabled--;
+        WARN_ON(blk_tracer_enabled < 0);
+        mutex_unlock(&blk_probe_mutex);
+
+        blk_tracer_stop(tr);
+}
+
+static struct {
+        const char *act[2];
+        int        (*print)(struct trace_seq *s, const struct trace_entry *ent);
+} what2act[] __read_mostly = {
+        [__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 int blk_trace_event_print(struct trace_seq *s, struct trace_entry *ent,
+                                 int flags)
+{
+        const struct blk_io_trace *t = (struct blk_io_trace *)ent;
+        const u16 what = t->action & ((1 << BLK_TC_SHIFT) - 1);
+        int ret;
+
+        if (unlikely(what == 0 || what > ARRAY_SIZE(what2act)))
+                ret = trace_seq_printf(s, "Bad pc action %x\n", what);
+        else {
+                const bool long_act = !!(trace_flags & TRACE_ITER_VERBOSE);
+                ret = blk_log_action_seq(s, t, what2act[what].act[long_act]);
+                if (ret)
+                        ret = what2act[what].print(s, ent);
+        }
+
+        return ret ? TRACE_TYPE_HANDLED : TRACE_TYPE_PARTIAL_LINE;
+}
+
+static enum print_line_t blk_tracer_print_line(struct trace_iterator *iter)
+{
+        const struct blk_io_trace *t;
+        u16 what;
+        int ret;
+
+        if (!(blk_tracer_flags.val & TRACE_BLK_OPT_CLASSIC))
+                return TRACE_TYPE_UNHANDLED;
+
+        t = (const struct blk_io_trace *)iter->ent;
+        what = t->action & ((1 << BLK_TC_SHIFT) - 1);
+
+        if (unlikely(what == 0 || what > ARRAY_SIZE(what2act)))
+                ret = trace_seq_printf(&iter->seq, "Bad pc action %x\n", what);
+        else {
+                const bool long_act = !!(trace_flags & TRACE_ITER_VERBOSE);
+                ret = blk_log_action_iter(iter, what2act[what].act[long_act]);
+                if (ret)
+                        ret = what2act[what].print(&iter->seq, iter->ent);
+        }
+
+        return ret ? TRACE_TYPE_HANDLED : TRACE_TYPE_PARTIAL_LINE;
+}
+
+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,
+        .latency_trace  = blk_trace_event_print,
+        .raw            = trace_nop_print,
+        .hex            = trace_nop_print,
+        .binary         = trace_nop_print,
+};
+
+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;
+
+        kfree(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;
+
+        ret = -ENOMEM;
+        bt = kzalloc(sizeof(*bt), GFP_KERNEL);
+        if (!bt)
+                goto err;
+
+        bt->dev = dev;
+        bt->act_mask = (u16)-1;
+        bt->end_lba = -1ULL;
+        bt->trace_state = Blktrace_running;
+
+        old_bt = xchg(&q->blk_trace, bt);
+        if (old_bt != NULL) {
+                (void)xchg(&q->blk_trace, old_bt);
+                kfree(bt);
+                ret = -EBUSY;
+        }
+        return 0;
+err:
+        return ret;
+}
+
+/*
+ * sysfs interface to enable and configure tracing
+ */
+
+static ssize_t sysfs_blk_trace_enable_show(struct device *dev,
+                                           struct device_attribute *attr,
+                                           char *buf)
+{
+        struct hd_struct *p = dev_to_part(dev);
+        struct block_device *bdev;
+        ssize_t ret = -ENXIO;
+
+        lock_kernel();
+        bdev = bdget(part_devt(p));
+        if (bdev != NULL) {
+                struct request_queue *q = bdev_get_queue(bdev);
+
+                if (q != NULL) {
+                        mutex_lock(&bdev->bd_mutex);
+                        ret = sprintf(buf, "%u\n", !!q->blk_trace);
+                        mutex_unlock(&bdev->bd_mutex);
+                }
+
+                bdput(bdev);
+        }
+
+        unlock_kernel();
+        return ret;
+}
+
+static ssize_t sysfs_blk_trace_enable_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;
+        int value;
+        ssize_t ret = -ENXIO;
+
+        if (count == 0 || sscanf(buf, "%d", &value) != 1)
+                goto out;
+
+        lock_kernel();
+        p = dev_to_part(dev);
+        bdev = bdget(part_devt(p));
+        if (bdev == NULL)
+                goto out_unlock_kernel;
+
+        q = bdev_get_queue(bdev);
+        if (q == NULL)
+                goto out_bdput;
+
+        mutex_lock(&bdev->bd_mutex);
+        if (value)
+                ret = blk_trace_setup_queue(q, bdev->bd_dev);
+        else
+                ret = blk_trace_remove_queue(q);
+        mutex_unlock(&bdev->bd_mutex);
+
+        if (ret == 0)
+                ret = count;
+out_bdput:
+        bdput(bdev);
+out_unlock_kernel:
+        unlock_kernel();
+out:
+        return ret;
+}
+
+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 DEVICE_ATTR(enable, S_IRUGO | S_IWUSR,
+                   sysfs_blk_trace_enable_show, sysfs_blk_trace_enable_store);
+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 int blk_str2act_mask(const char *str)
+{
+        int mask = 0;
+        char *copy = kstrdup(str, GFP_KERNEL), *s;
+
+        if (copy == NULL)
+                return -ENOMEM;
+
+        s = strstrip(copy);
+
+        while (1) {
+                char *sep = strchr(s, ',');
+
+                if (sep != NULL)
+                        *sep = '\0';
+
+                if (strcasecmp(s, "barrier") == 0)
+                        mask |= BLK_TC_BARRIER;
+                else if (strcasecmp(s, "complete") == 0)
+                        mask |= BLK_TC_COMPLETE;
+                else if (strcasecmp(s, "fs") == 0)
+                        mask |= BLK_TC_FS;
+                else if (strcasecmp(s, "issue") == 0)
+                        mask |= BLK_TC_ISSUE;
+                else if (strcasecmp(s, "pc") == 0)
+                        mask |= BLK_TC_PC;
+                else if (strcasecmp(s, "queue") == 0)
+                        mask |= BLK_TC_QUEUE;
+                else if (strcasecmp(s, "read") == 0)
+                        mask |= BLK_TC_READ;
+                else if (strcasecmp(s, "requeue") == 0)
+                        mask |= BLK_TC_REQUEUE;
+                else if (strcasecmp(s, "sync") == 0)
+                        mask |= BLK_TC_SYNC;
+                else if (strcasecmp(s, "write") == 0)
+                        mask |= BLK_TC_WRITE;
+
+                if (sep == NULL)
+                        break;
+
+                s = sep + 1;
+        }
+        kfree(copy);
+
+        return mask;
+}
+
+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 = bdev_get_queue(bdev);
+        if (q == NULL)
+                goto out_bdput;
+        mutex_lock(&bdev->bd_mutex);
+        if (q->blk_trace == NULL)
+                ret = sprintf(buf, "disabled\n");
+        else if (attr == &dev_attr_act_mask)
+                ret = sprintf(buf, "%#x\n", 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);
+        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 = -ENXIO;
+
+        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 */
+                        value = blk_str2act_mask(buf);
+                        if (value < 0)
+                                goto out;
+                }
+        } else if (sscanf(buf, "%llu", &value) != 1)
+                goto out;
+
+        lock_kernel();
+        p = dev_to_part(dev);
+        bdev = bdget(part_devt(p));
+        if (bdev == NULL)
+                goto out_unlock_kernel;
+
+        q = bdev_get_queue(bdev);
+        if (q == NULL)
+                goto out_bdput;
+
+        mutex_lock(&bdev->bd_mutex);
+        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;
+                ret = count;
+        }
+        mutex_unlock(&bdev->bd_mutex);
+out_bdput:
+        bdput(bdev);
+out_unlock_kernel:
+        unlock_kernel();
+out:
+        return ret;
+}