]> nv-tegra.nvidia Code Review - linux-2.6.git/blobdiff - kernel/trace/blktrace.c
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael...
[linux-2.6.git] / kernel / trace / blktrace.c
index a400b861fad3074cff6d7db7a53749793c6cba75..b3bc91a3f510d089d7ce69ad4b294655dce53ac7 100644 (file)
 #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 <trace/block.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;
@@ -60,13 +66,15 @@ static void trace_note(struct blk_trace *bt, pid_t pid, int action,
 {
        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(blk_tr, TRACE_BLK,
+               event = trace_buffer_lock_reserve(buffer, TRACE_BLK,
                                                  sizeof(*t) + len,
                                                  0, pc);
                if (!event)
@@ -91,7 +99,7 @@ record_it:
                memcpy((void *) t + sizeof(*t), data, len);
 
                if (blk_tracer)
-                       trace_buffer_unlock_commit(blk_tr, event, 0, pc);
+                       trace_buffer_unlock_commit(buffer, event, 0, pc);
        }
 }
 
@@ -147,7 +155,7 @@ static int act_log_check(struct blk_trace *bt, u32 what, sector_t sector,
 {
        if (((bt->act_mask << BLK_TC_SHIFT) & what) == 0)
                return 1;
-       if (sector < bt->start_lba || sector > bt->end_lba)
+       if (sector && (sector < bt->start_lba || sector > bt->end_lba))
                return 1;
        if (bt->pid && pid != bt->pid)
                return 1;
@@ -174,6 +182,7 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
 {
        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;
@@ -192,15 +201,16 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
        what |= MASK_TC_BIT(rw, DISCARD);
 
        pid = tsk->pid;
-       if (unlikely(act_log_check(bt, what, sector, 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(blk_tr, TRACE_BLK,
+               event = trace_buffer_lock_reserve(buffer, TRACE_BLK,
                                                  sizeof(*t) + pdu_len,
                                                  0, pc);
                if (!event)
@@ -247,7 +257,7 @@ record_it:
                        memcpy((void *) t + sizeof(*t), pdu_data, pdu_len);
 
                if (blk_tracer) {
-                       trace_buffer_unlock_commit(blk_tr, event, 0, pc);
+                       trace_buffer_unlock_commit(buffer, event, 0, pc);
                        return;
                }
        }
@@ -263,6 +273,7 @@ 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);
@@ -327,7 +338,7 @@ static ssize_t blk_msg_write(struct file *filp, const char __user *buffer,
        char *msg;
        struct blk_trace *bt;
 
-       if (count > BLK_TN_MAX_MSG - 1)
+       if (count >= BLK_TN_MAX_MSG)
                return -EINVAL;
 
        msg = kmalloc(count + 1, GFP_KERNEL);
@@ -372,18 +383,8 @@ static int blk_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
 
 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;
 }
 
@@ -403,11 +404,29 @@ static struct rchan_callbacks blk_relay_callbacks = {
        .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 blk_user_trace_setup *buts)
+                      struct block_device *bdev,
+                      struct blk_user_trace_setup *buts)
 {
        struct blk_trace *old_bt, *bt = NULL;
        struct dentry *dir = NULL;
@@ -480,10 +499,13 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
        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;
+       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;
@@ -505,6 +527,7 @@ err:
 }
 
 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;
@@ -514,13 +537,14 @@ int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
        if (ret)
                return -EFAULT;
 
-       ret = do_blk_trace_setup(q, name, dev, &buts);
+       ret = do_blk_trace_setup(q, name, dev, bdev, &buts);
        if (ret)
                return ret;
 
-       if (copy_to_user(arg, &buts, sizeof(buts)))
+       if (copy_to_user(arg, &buts, sizeof(buts))) {
+               blk_trace_remove(q);
                return -EFAULT;
-
+       }
        return 0;
 }
 EXPORT_SYMBOL_GPL(blk_trace_setup);
@@ -582,7 +606,7 @@ int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
        switch (cmd) {
        case BLKTRACESETUP:
                bdevname(bdev, b);
-               ret = blk_trace_setup(q, b, bdev->bd_dev, arg);
+               ret = blk_trace_setup(q, b, bdev->bd_dev, bdev, arg);
                break;
        case BLKTRACESTART:
                start = 1;
@@ -642,12 +666,12 @@ static void blk_add_trace_rq(struct request_queue *q, struct request *rq,
 
        if (blk_pc_request(rq)) {
                what |= BLK_TC_ACT(BLK_TC_PC);
-               __blk_add_trace(bt, 0, rq->data_len, rw, what, rq->errors,
-                               sizeof(rq->cmd), rq->cmd);
+               __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, rq->hard_sector, rq->hard_nr_sectors << 9,
-                               rw, what, rq->errors, 0, NULL);
+               __blk_add_trace(bt, blk_rq_pos(rq), blk_rq_bytes(rq), rw,
+                               what, rq->errors, 0, NULL);
        }
 }
 
@@ -809,7 +833,6 @@ static void blk_add_trace_split(struct request_queue *q, struct bio *bio,
  * @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
@@ -817,7 +840,7 @@ static void blk_add_trace_split(struct request_queue *q, struct bio *bio,
  *
  **/
 static void blk_add_trace_remap(struct request_queue *q, struct bio *bio,
-                                      dev_t dev, sector_t from, sector_t to)
+                                      dev_t dev, sector_t from)
 {
        struct blk_trace *bt = q->blk_trace;
        struct blk_io_trace_remap r;
@@ -825,12 +848,44 @@ static void blk_add_trace_remap(struct request_queue *q, struct bio *bio,
        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);
+       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, from, bio->bi_size, bio->bi_rw, BLK_TA_REMAP,
-                       !bio_flagged(bio, BIO_UPTODATE), sizeof(r), &r);
+       __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);
 }
 
 /**
@@ -854,11 +909,11 @@ void blk_add_driver_data(struct request_queue *q,
                return;
 
        if (blk_pc_request(rq))
-               __blk_add_trace(bt, 0, rq->data_len, 0, BLK_TA_DRV_DATA,
-                               rq->errors, len, data);
+               __blk_add_trace(bt, 0, blk_rq_bytes(rq), 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);
+               __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);
 
@@ -900,10 +955,13 @@ static void blk_register_tracepoints(void)
        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);
@@ -971,6 +1029,16 @@ 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;
@@ -996,11 +1064,11 @@ 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;
+       __u64 sector_from = __r->sector_from;
 
-       r->device = be32_to_cpu(__r->device);
        r->device_from = be32_to_cpu(__r->device_from);
-       r->sector = be64_to_cpu(sector);
+       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);
@@ -1031,36 +1099,98 @@ static int blk_log_action(struct trace_iterator *iter, const char *act)
                                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_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);
+       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_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));
+       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 = 0, };
+       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), MINOR(r.device),
-                              (unsigned long long)r.sector);
+                               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)
@@ -1117,7 +1247,6 @@ static void blk_tracer_print_header(struct seq_file *m)
 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)
@@ -1130,7 +1259,6 @@ static int blk_tracer_init(struct trace_array *tr)
 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)
@@ -1182,7 +1310,7 @@ static enum print_line_t print_one_line(struct trace_iterator *iter,
        }
 
        if (unlikely(what == 0 || what >= ARRAY_SIZE(what2act)))
-               ret = trace_seq_printf(s, "Bad pc action %x\n", what);
+               ret = trace_seq_printf(s, "Unknown action %x\n", what);
        else {
                ret = log_action(iter, what2act[what].act[long_act]);
                if (ret)
@@ -1195,9 +1323,6 @@ out:
 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);
 }
 
@@ -1232,6 +1357,18 @@ static enum print_line_t blk_tracer_print_line(struct trace_iterator *iter)
        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,
@@ -1241,6 +1378,7 @@ static struct tracer blk_tracer __read_mostly = {
        .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 = {
@@ -1285,7 +1423,8 @@ static int blk_trace_remove_queue(struct request_queue *q)
 /*
  * Setup everything required to start tracing
  */
-static int blk_trace_setup_queue(struct request_queue *q, dev_t dev)
+static int blk_trace_setup_queue(struct request_queue *q,
+                                struct block_device *bdev)
 {
        struct blk_trace *old_bt, *bt = NULL;
        int ret = -ENOMEM;
@@ -1298,9 +1437,10 @@ static int blk_trace_setup_queue(struct request_queue *q, dev_t dev)
        if (!bt->msg_data)
                goto free_bt;
 
-       bt->dev = dev;
+       bt->dev = bdev->bd_dev;
        bt->act_mask = (u16)-1;
-       bt->end_lba = -1ULL;
+
+       blk_trace_setup_lba(bt, bdev);
 
        old_bt = xchg(&q->blk_trace, bt);
        if (old_bt != NULL) {
@@ -1377,12 +1517,12 @@ static int blk_trace_str2mask(const char *str)
 {
        int i;
        int mask = 0;
-       char *s, *token;
+       char *buf, *s, *token;
 
-       s = kstrdup(str, GFP_KERNEL);
-       if (s == NULL)
+       buf = kstrdup(str, GFP_KERNEL);
+       if (buf == NULL)
                return -ENOMEM;
-       s = strstrip(s);
+       s = strstrip(buf);
 
        while (1) {
                token = strsep(&s, ",");
@@ -1403,7 +1543,7 @@ static int blk_trace_str2mask(const char *str)
                        break;
                }
        }
-       kfree(s);
+       kfree(buf);
 
        return mask;
 }
@@ -1517,7 +1657,7 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
 
        if (attr == &dev_attr_enable) {
                if (value)
-                       ret = blk_trace_setup_queue(q, bdev->bd_dev);
+                       ret = blk_trace_setup_queue(q, bdev);
                else
                        ret = blk_trace_remove_queue(q);
                goto out_unlock_bdev;
@@ -1525,7 +1665,7 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
 
        ret = 0;
        if (q->blk_trace == NULL)
-               ret = blk_trace_setup_queue(q, bdev->bd_dev);
+               ret = blk_trace_setup_queue(q, bdev);
 
        if (ret == 0) {
                if (attr == &dev_attr_act_mask)
@@ -1548,3 +1688,82 @@ 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 */
+