kernel/trace/blktrace.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2006 Jens Axboe <axboe@kernel.dk>
   4  *
   5  */
   6 #include <linux/kernel.h>
   7 #include <linux/blkdev.h>
   8 #include <linux/blktrace_api.h>
   9 #include <linux/percpu.h>
  10 #include <linux/init.h>
  11 #include <linux/mutex.h>
  12 #include <linux/slab.h>
  13 #include <linux/debugfs.h>
  14 #include <linux/export.h>
  15 #include <linux/time.h>
  16 #include <linux/uaccess.h>
  17 #include <linux/list.h>
  18 #include <linux/blk-cgroup.h>
  19
  20 #include "../../block/blk.h"
  21
  22 #include <trace/events/block.h>
  23
  24 #include "trace_output.h"
  25
  26 #ifdef CONFIG_BLK_DEV_IO_TRACE
  27
  28 static unsigned int blktrace_seq __read_mostly = 1;
  29
  30 static struct trace_array *blk_tr;
  31 static bool blk_tracer_enabled __read_mostly;
  32
  33 static LIST_HEAD(running_trace_list);
  34 static __cacheline_aligned_in_smp DEFINE_SPINLOCK(running_trace_lock);
  35
  36 /* Select an alternative, minimalistic output than the original one */
  37 #define TRACE_BLK_OPT_CLASSIC   0x1
  38 #define TRACE_BLK_OPT_CGROUP    0x2
  39 #define TRACE_BLK_OPT_CGNAME    0x4
  40
  41 static struct tracer_opt blk_tracer_opts[] = {
  42         /* Default disable the minimalistic output */
  43         { TRACER_OPT(blk_classic, TRACE_BLK_OPT_CLASSIC) },
  44 #ifdef CONFIG_BLK_CGROUP
  45         { TRACER_OPT(blk_cgroup, TRACE_BLK_OPT_CGROUP) },
  46         { TRACER_OPT(blk_cgname, TRACE_BLK_OPT_CGNAME) },
  47 #endif
  48         { }
  49 };
  50
  51 static struct tracer_flags blk_tracer_flags = {
  52         .val  = 0,
  53         .opts = blk_tracer_opts,
  54 };
  55
  56 /* Global reference count of probes */
  57 static DEFINE_MUTEX(blk_probe_mutex);
  58 static int blk_probes_ref;
  59
  60 static void blk_register_tracepoints(void);
  61 static void blk_unregister_tracepoints(void);
  62
  63 /*
  64  * Send out a notify message.
  65  */
  66 static void trace_note(struct blk_trace *bt, pid_t pid, int action,
  67                        const void *data, size_t len, u64 cgid)
  68 {
  69         struct blk_io_trace *t;
  70         struct ring_buffer_event *event = NULL;
  71         struct trace_buffer *buffer = NULL;
  72         int pc = 0;
  73         int cpu = smp_processor_id();
  74         bool blk_tracer = blk_tracer_enabled;
  75         ssize_t cgid_len = cgid ? sizeof(cgid) : 0;
  76
  77         if (blk_tracer) {
  78                 buffer = blk_tr->array_buffer.buffer;
  79                 pc = preempt_count();
  80                 event = trace_buffer_lock_reserve(buffer, TRACE_BLK,
  81                                                   sizeof(*t) + len + cgid_len,
  82                                                   0, pc);
  83                 if (!event)
  84                         return;
  85                 t = ring_buffer_event_data(event);
  86                 goto record_it;
  87         }
  88
  89         if (!bt->rchan)
  90                 return;
  91
  92         t = relay_reserve(bt->rchan, sizeof(*t) + len + cgid_len);
  93         if (t) {
  94                 t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
  95                 t->time = ktime_to_ns(ktime_get());
  96 record_it:
  97                 t->device = bt->dev;
  98                 t->action = action | (cgid ? __BLK_TN_CGROUP : 0);
  99                 t->pid = pid;
 100                 t->cpu = cpu;
 101                 t->pdu_len = len + cgid_len;
 102                 if (cgid_len)
 103                         memcpy((void *)t + sizeof(*t), &cgid, cgid_len);
 104                 memcpy((void *) t + sizeof(*t) + cgid_len, data, len);
 105
 106                 if (blk_tracer)
 107                         trace_buffer_unlock_commit(blk_tr, buffer, event, 0, pc);
 108         }
 109 }
 110
 111 /*
 112  * Send out a notify for this process, if we haven't done so since a trace
 113  * started
 114  */
 115 static void trace_note_tsk(struct task_struct *tsk)
 116 {
 117         unsigned long flags;
 118         struct blk_trace *bt;
 119
 120         tsk->btrace_seq = blktrace_seq;
 121         spin_lock_irqsave(&running_trace_lock, flags);
 122         list_for_each_entry(bt, &running_trace_list, running_list) {
 123                 trace_note(bt, tsk->pid, BLK_TN_PROCESS, tsk->comm,
 124                            sizeof(tsk->comm), 0);
 125         }
 126         spin_unlock_irqrestore(&running_trace_lock, flags);
 127 }
 128
 129 static void trace_note_time(struct blk_trace *bt)
 130 {
 131         struct timespec64 now;
 132         unsigned long flags;
 133         u32 words[2];
 134
 135         /* need to check user space to see if this breaks in y2038 or y2106 */
 136         ktime_get_real_ts64(&now);
 137         words[0] = (u32)now.tv_sec;
 138         words[1] = now.tv_nsec;
 139
 140         local_irq_save(flags);
 141         trace_note(bt, 0, BLK_TN_TIMESTAMP, words, sizeof(words), 0);
 142         local_irq_restore(flags);
 143 }
 144
 145 void __trace_note_message(struct blk_trace *bt, struct blkcg *blkcg,
 146         const char *fmt, ...)
 147 {
 148         int n;
 149         va_list args;
 150         unsigned long flags;
 151         char *buf;
 152
 153         if (unlikely(bt->trace_state != Blktrace_running &&
 154                      !blk_tracer_enabled))
 155                 return;
 156
 157         /*
 158          * If the BLK_TC_NOTIFY action mask isn't set, don't send any note
 159          * message to the trace.
 160          */
 161         if (!(bt->act_mask & BLK_TC_NOTIFY))
 162                 return;
 163
 164         local_irq_save(flags);
 165         buf = this_cpu_ptr(bt->msg_data);
 166         va_start(args, fmt);
 167         n = vscnprintf(buf, BLK_TN_MAX_MSG, fmt, args);
 168         va_end(args);
 169
 170         if (!(blk_tracer_flags.val & TRACE_BLK_OPT_CGROUP))
 171                 blkcg = NULL;
 172 #ifdef CONFIG_BLK_CGROUP
 173         trace_note(bt, 0, BLK_TN_MESSAGE, buf, n,
 174                    blkcg ? cgroup_id(blkcg->css.cgroup) : 1);
 175 #else
 176         trace_note(bt, 0, BLK_TN_MESSAGE, buf, n, 0);
 177 #endif
 178         local_irq_restore(flags);
 179 }
 180 EXPORT_SYMBOL_GPL(__trace_note_message);
 181
 182 static int act_log_check(struct blk_trace *bt, u32 what, sector_t sector,
 183                          pid_t pid)
 184 {
 185         if (((bt->act_mask << BLK_TC_SHIFT) & what) == 0)
 186                 return 1;
 187         if (sector && (sector < bt->start_lba || sector > bt->end_lba))
 188                 return 1;
 189         if (bt->pid && pid != bt->pid)
 190                 return 1;
 191
 192         return 0;
 193 }
 194
 195 /*
 196  * Data direction bit lookup
 197  */
 198 static const u32 ddir_act[2] = { BLK_TC_ACT(BLK_TC_READ),
 199                                  BLK_TC_ACT(BLK_TC_WRITE) };
 200
 201 #define BLK_TC_RAHEAD           BLK_TC_AHEAD
 202 #define BLK_TC_PREFLUSH         BLK_TC_FLUSH
 203
 204 /* The ilog2() calls fall out because they're constant */
 205 #define MASK_TC_BIT(rw, __name) ((rw & REQ_ ## __name) << \
 206           (ilog2(BLK_TC_ ## __name) + BLK_TC_SHIFT - __REQ_ ## __name))
 207
 208 /*
 209  * The worker for the various blk_add_trace*() types. Fills out a
 210  * blk_io_trace structure and places it in a per-cpu subbuffer.
 211  */
 212 static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
 213                      int op, int op_flags, u32 what, int error, int pdu_len,
 214                      void *pdu_data, u64 cgid)
 215 {
 216         struct task_struct *tsk = current;
 217         struct ring_buffer_event *event = NULL;
 218         struct trace_buffer *buffer = NULL;
 219         struct blk_io_trace *t;
 220         unsigned long flags = 0;
 221         unsigned long *sequence;
 222         pid_t pid;
 223         int cpu, pc = 0;
 224         bool blk_tracer = blk_tracer_enabled;
 225         ssize_t cgid_len = cgid ? sizeof(cgid) : 0;
 226
 227         if (unlikely(bt->trace_state != Blktrace_running && !blk_tracer))
 228                 return;
 229
 230         what |= ddir_act[op_is_write(op) ? WRITE : READ];
 231         what |= MASK_TC_BIT(op_flags, SYNC);
 232         what |= MASK_TC_BIT(op_flags, RAHEAD);
 233         what |= MASK_TC_BIT(op_flags, META);
 234         what |= MASK_TC_BIT(op_flags, PREFLUSH);
 235         what |= MASK_TC_BIT(op_flags, FUA);
 236         if (op == REQ_OP_DISCARD || op == REQ_OP_SECURE_ERASE)
 237                 what |= BLK_TC_ACT(BLK_TC_DISCARD);
 238         if (op == REQ_OP_FLUSH)
 239                 what |= BLK_TC_ACT(BLK_TC_FLUSH);
 240         if (cgid)
 241                 what |= __BLK_TA_CGROUP;
 242
 243         pid = tsk->pid;
 244         if (act_log_check(bt, what, sector, pid))
 245                 return;
 246         cpu = raw_smp_processor_id();
 247
 248         if (blk_tracer) {
 249                 tracing_record_cmdline(current);
 250
 251                 buffer = blk_tr->array_buffer.buffer;
 252                 pc = preempt_count();
 253                 event = trace_buffer_lock_reserve(buffer, TRACE_BLK,
 254                                                   sizeof(*t) + pdu_len + cgid_len,
 255                                                   0, pc);
 256                 if (!event)
 257                         return;
 258                 t = ring_buffer_event_data(event);
 259                 goto record_it;
 260         }
 261
 262         if (unlikely(tsk->btrace_seq != blktrace_seq))
 263                 trace_note_tsk(tsk);
 264
 265         /*
 266          * A word about the locking here - we disable interrupts to reserve
 267          * some space in the relay per-cpu buffer, to prevent an irq
 268          * from coming in and stepping on our toes.
 269          */
 270         local_irq_save(flags);
 271         t = relay_reserve(bt->rchan, sizeof(*t) + pdu_len + cgid_len);
 272         if (t) {
 273                 sequence = per_cpu_ptr(bt->sequence, cpu);
 274
 275                 t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
 276                 t->sequence = ++(*sequence);
 277                 t->time = ktime_to_ns(ktime_get());
 278 record_it:
 279                 /*
 280                  * These two are not needed in ftrace as they are in the
 281                  * generic trace_entry, filled by tracing_generic_entry_update,
 282                  * but for the trace_event->bin() synthesizer benefit we do it
 283                  * here too.
 284                  */
 285                 t->cpu = cpu;
 286                 t->pid = pid;
 287
 288                 t->sector = sector;
 289                 t->bytes = bytes;
 290                 t->action = what;
 291                 t->device = bt->dev;
 292                 t->error = error;
 293                 t->pdu_len = pdu_len + cgid_len;
 294
 295                 if (cgid_len)
 296                         memcpy((void *)t + sizeof(*t), &cgid, cgid_len);
 297                 if (pdu_len)
 298                         memcpy((void *)t + sizeof(*t) + cgid_len, pdu_data, pdu_len);
 299
 300                 if (blk_tracer) {
 301                         trace_buffer_unlock_commit(blk_tr, buffer, event, 0, pc);
 302                         return;
 303                 }
 304         }
 305
 306         local_irq_restore(flags);
 307 }
 308
 309 static void blk_trace_free(struct blk_trace *bt)
 310 {
 311         debugfs_remove(bt->msg_file);
 312         debugfs_remove(bt->dropped_file);
 313         relay_close(bt->rchan);
 314         debugfs_remove(bt->dir);
 315         free_percpu(bt->sequence);
 316         free_percpu(bt->msg_data);
 317         kfree(bt);
 318 }
 319
 320 static void get_probe_ref(void)
 321 {
 322         mutex_lock(&blk_probe_mutex);
 323         if (++blk_probes_ref == 1)
 324                 blk_register_tracepoints();
 325         mutex_unlock(&blk_probe_mutex);
 326 }
 327
 328 static void put_probe_ref(void)
 329 {
 330         mutex_lock(&blk_probe_mutex);
 331         if (!--blk_probes_ref)
 332                 blk_unregister_tracepoints();
 333         mutex_unlock(&blk_probe_mutex);
 334 }
 335
 336 static void blk_trace_cleanup(struct blk_trace *bt)
 337 {
 338         synchronize_rcu();
 339         blk_trace_free(bt);
 340         put_probe_ref();
 341 }
 342
 343 static int __blk_trace_remove(struct request_queue *q)
 344 {
 345         struct blk_trace *bt;
 346
 347         bt = xchg(&q->blk_trace, NULL);
 348         if (!bt)
 349                 return -EINVAL;
 350
 351         if (bt->trace_state != Blktrace_running)
 352                 blk_trace_cleanup(bt);
 353
 354         return 0;
 355 }
 356
 357 int blk_trace_remove(struct request_queue *q)
 358 {
 359         int ret;
 360
 361         mutex_lock(&q->blk_trace_mutex);
 362         ret = __blk_trace_remove(q);
 363         mutex_unlock(&q->blk_trace_mutex);
 364
 365         return ret;
 366 }
 367 EXPORT_SYMBOL_GPL(blk_trace_remove);
 368
 369 static ssize_t blk_dropped_read(struct file *filp, char __user *buffer,
 370                                 size_t count, loff_t *ppos)
 371 {
 372         struct blk_trace *bt = filp->private_data;
 373         char buf[16];
 374
 375         snprintf(buf, sizeof(buf), "%u\n", atomic_read(&bt->dropped));
 376
 377         return simple_read_from_buffer(buffer, count, ppos, buf, strlen(buf));
 378 }
 379
 380 static const struct file_operations blk_dropped_fops = {
 381         .owner =        THIS_MODULE,
 382         .open =         simple_open,
 383         .read =         blk_dropped_read,
 384         .llseek =       default_llseek,
 385 };
 386
 387 static ssize_t blk_msg_write(struct file *filp, const char __user *buffer,
 388                                 size_t count, loff_t *ppos)
 389 {
 390         char *msg;
 391         struct blk_trace *bt;
 392
 393         if (count >= BLK_TN_MAX_MSG)
 394                 return -EINVAL;
 395
 396         msg = memdup_user_nul(buffer, count);
 397         if (IS_ERR(msg))
 398                 return PTR_ERR(msg);
 399
 400         bt = filp->private_data;
 401         __trace_note_message(bt, NULL, "%s", msg);
 402         kfree(msg);
 403
 404         return count;
 405 }
 406
 407 static const struct file_operations blk_msg_fops = {
 408         .owner =        THIS_MODULE,
 409         .open =         simple_open,
 410         .write =        blk_msg_write,
 411         .llseek =       noop_llseek,
 412 };
 413
 414 /*
 415  * Keep track of how many times we encountered a full subbuffer, to aid
 416  * the user space app in telling how many lost events there were.
 417  */
 418 static int blk_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
 419                                      void *prev_subbuf, size_t prev_padding)
 420 {
 421         struct blk_trace *bt;
 422
 423         if (!relay_buf_full(buf))
 424                 return 1;
 425
 426         bt = buf->chan->private_data;
 427         atomic_inc(&bt->dropped);
 428         return 0;
 429 }
 430
 431 static int blk_remove_buf_file_callback(struct dentry *dentry)
 432 {
 433         debugfs_remove(dentry);
 434
 435         return 0;
 436 }
 437
 438 static struct dentry *blk_create_buf_file_callback(const char *filename,
 439                                                    struct dentry *parent,
 440                                                    umode_t mode,
 441                                                    struct rchan_buf *buf,
 442                                                    int *is_global)
 443 {
 444         return debugfs_create_file(filename, mode, parent, buf,
 445                                         &relay_file_operations);
 446 }
 447
 448 static struct rchan_callbacks blk_relay_callbacks = {
 449         .subbuf_start           = blk_subbuf_start_callback,
 450         .create_buf_file        = blk_create_buf_file_callback,
 451         .remove_buf_file        = blk_remove_buf_file_callback,
 452 };
 453
 454 static void blk_trace_setup_lba(struct blk_trace *bt,
 455                                 struct block_device *bdev)
 456 {
 457         struct hd_struct *part = NULL;
 458
 459         if (bdev)
 460                 part = bdev->bd_part;
 461
 462         if (part) {
 463                 bt->start_lba = part->start_sect;
 464                 bt->end_lba = part->start_sect + part->nr_sects;
 465         } else {
 466                 bt->start_lba = 0;
 467                 bt->end_lba = -1ULL;
 468         }
 469 }
 470
 471 /*
 472  * Setup everything required to start tracing
 473  */
 474 static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
 475                               struct block_device *bdev,
 476                               struct blk_user_trace_setup *buts)
 477 {
 478         struct blk_trace *bt = NULL;
 479         struct dentry *dir = NULL;
 480         int ret;
 481
 482         if (!buts->buf_size || !buts->buf_nr)
 483                 return -EINVAL;
 484
 485         if (!blk_debugfs_root)
 486                 return -ENOENT;
 487
 488         strncpy(buts->name, name, BLKTRACE_BDEV_SIZE);
 489         buts->name[BLKTRACE_BDEV_SIZE - 1] = '\0';
 490
 491         /*
 492          * some device names have larger paths - convert the slashes
 493          * to underscores for this to work as expected
 494          */
 495         strreplace(buts->name, '/', '_');
 496
 497         bt = kzalloc(sizeof(*bt), GFP_KERNEL);
 498         if (!bt)
 499                 return -ENOMEM;
 500
 501         ret = -ENOMEM;
 502         bt->sequence = alloc_percpu(unsigned long);
 503         if (!bt->sequence)
 504                 goto err;
 505
 506         bt->msg_data = __alloc_percpu(BLK_TN_MAX_MSG, __alignof__(char));
 507         if (!bt->msg_data)
 508                 goto err;
 509
 510         ret = -ENOENT;
 511
 512         dir = debugfs_lookup(buts->name, blk_debugfs_root);
 513         if (!dir)
 514                 bt->dir = dir = debugfs_create_dir(buts->name, blk_debugfs_root);
 515
 516         bt->dev = dev;
 517         atomic_set(&bt->dropped, 0);
 518         INIT_LIST_HEAD(&bt->running_list);
 519
 520         ret = -EIO;
 521         bt->dropped_file = debugfs_create_file("dropped", 0444, dir, bt,
 522                                                &blk_dropped_fops);
 523
 524         bt->msg_file = debugfs_create_file("msg", 0222, dir, bt, &blk_msg_fops);
 525
 526         bt->rchan = relay_open("trace", dir, buts->buf_size,
 527                                 buts->buf_nr, &blk_relay_callbacks, bt);
 528         if (!bt->rchan)
 529                 goto err;
 530
 531         bt->act_mask = buts->act_mask;
 532         if (!bt->act_mask)
 533                 bt->act_mask = (u16) -1;
 534
 535         blk_trace_setup_lba(bt, bdev);
 536
 537         /* overwrite with user settings */
 538         if (buts->start_lba)
 539                 bt->start_lba = buts->start_lba;
 540         if (buts->end_lba)
 541                 bt->end_lba = buts->end_lba;
 542
 543         bt->pid = buts->pid;
 544         bt->trace_state = Blktrace_setup;
 545
 546         ret = -EBUSY;
 547         if (cmpxchg(&q->blk_trace, NULL, bt))
 548                 goto err;
 549
 550         get_probe_ref();
 551
 552         ret = 0;
 553 err:
 554         if (dir && !bt->dir)
 555                 dput(dir);
 556         if (ret)
 557                 blk_trace_free(bt);
 558         return ret;
 559 }
 560
 561 static int __blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
 562                              struct block_device *bdev, char __user *arg)
 563 {
 564         struct blk_user_trace_setup buts;
 565         int ret;
 566
 567         ret = copy_from_user(&buts, arg, sizeof(buts));
 568         if (ret)
 569                 return -EFAULT;
 570
 571         ret = do_blk_trace_setup(q, name, dev, bdev, &buts);
 572         if (ret)
 573                 return ret;
 574
 575         if (copy_to_user(arg, &buts, sizeof(buts))) {
 576                 __blk_trace_remove(q);
 577                 return -EFAULT;
 578         }
 579         return 0;
 580 }
 581
 582 int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
 583                     struct block_device *bdev,
 584                     char __user *arg)
 585 {
 586         int ret;
 587
 588         mutex_lock(&q->blk_trace_mutex);
 589         ret = __blk_trace_setup(q, name, dev, bdev, arg);
 590         mutex_unlock(&q->blk_trace_mutex);
 591
 592         return ret;
 593 }
 594 EXPORT_SYMBOL_GPL(blk_trace_setup);
 595
 596 #if defined(CONFIG_COMPAT) && defined(CONFIG_X86_64)
 597 static int compat_blk_trace_setup(struct request_queue *q, char *name,
 598                                   dev_t dev, struct block_device *bdev,
 599                                   char __user *arg)
 600 {
 601         struct blk_user_trace_setup buts;
 602         struct compat_blk_user_trace_setup cbuts;
 603         int ret;
 604
 605         if (copy_from_user(&cbuts, arg, sizeof(cbuts)))
 606                 return -EFAULT;
 607
 608         buts = (struct blk_user_trace_setup) {
 609                 .act_mask = cbuts.act_mask,
 610                 .buf_size = cbuts.buf_size,
 611                 .buf_nr = cbuts.buf_nr,
 612                 .start_lba = cbuts.start_lba,
 613                 .end_lba = cbuts.end_lba,
 614                 .pid = cbuts.pid,
 615         };
 616
 617         ret = do_blk_trace_setup(q, name, dev, bdev, &buts);
 618         if (ret)
 619                 return ret;
 620
 621         if (copy_to_user(arg, &buts.name, ARRAY_SIZE(buts.name))) {
 622                 __blk_trace_remove(q);
 623                 return -EFAULT;
 624         }
 625
 626         return 0;
 627 }
 628 #endif
 629
 630 static int __blk_trace_startstop(struct request_queue *q, int start)
 631 {
 632         int ret;
 633         struct blk_trace *bt;
 634
 635         bt = rcu_dereference_protected(q->blk_trace,
 636                                        lockdep_is_held(&q->blk_trace_mutex));
 637         if (bt == NULL)
 638                 return -EINVAL;
 639
 640         /*
 641          * For starting a trace, we can transition from a setup or stopped
 642          * trace. For stopping a trace, the state must be running
 643          */
 644         ret = -EINVAL;
 645         if (start) {
 646                 if (bt->trace_state == Blktrace_setup ||
 647                     bt->trace_state == Blktrace_stopped) {
 648                         blktrace_seq++;
 649                         smp_mb();
 650                         bt->trace_state = Blktrace_running;
 651                         spin_lock_irq(&running_trace_lock);
 652                         list_add(&bt->running_list, &running_trace_list);
 653                         spin_unlock_irq(&running_trace_lock);
 654
 655                         trace_note_time(bt);
 656                         ret = 0;
 657                 }
 658         } else {
 659                 if (bt->trace_state == Blktrace_running) {
 660                         bt->trace_state = Blktrace_stopped;
 661                         spin_lock_irq(&running_trace_lock);
 662                         list_del_init(&bt->running_list);
 663                         spin_unlock_irq(&running_trace_lock);
 664                         relay_flush(bt->rchan);
 665                         ret = 0;
 666                 }
 667         }
 668
 669         return ret;
 670 }
 671
 672 int blk_trace_startstop(struct request_queue *q, int start)
 673 {
 674         int ret;
 675
 676         mutex_lock(&q->blk_trace_mutex);
 677         ret = __blk_trace_startstop(q, start);
 678         mutex_unlock(&q->blk_trace_mutex);
 679
 680         return ret;
 681 }
 682 EXPORT_SYMBOL_GPL(blk_trace_startstop);
 683
 684 /*
 685  * When reading or writing the blktrace sysfs files, the references to the
 686  * opened sysfs or device files should prevent the underlying block device
 687  * from being removed. So no further delete protection is really needed.
 688  */
 689
 690 /**
 691  * blk_trace_ioctl: - handle the ioctls associated with tracing
 692  * @bdev:       the block device
 693  * @cmd:        the ioctl cmd
 694  * @arg:        the argument data, if any
 695  *
 696  **/
 697 int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
 698 {
 699         struct request_queue *q;
 700         int ret, start = 0;
 701         char b[BDEVNAME_SIZE];
 702
 703         q = bdev_get_queue(bdev);
 704         if (!q)
 705                 return -ENXIO;
 706
 707         mutex_lock(&q->blk_trace_mutex);
 708
 709         switch (cmd) {
 710         case BLKTRACESETUP:
 711                 bdevname(bdev, b);
 712                 ret = __blk_trace_setup(q, b, bdev->bd_dev, bdev, arg);
 713                 break;
 714 #if defined(CONFIG_COMPAT) && defined(CONFIG_X86_64)
 715         case BLKTRACESETUP32:
 716                 bdevname(bdev, b);
 717                 ret = compat_blk_trace_setup(q, b, bdev->bd_dev, bdev, arg);
 718                 break;
 719 #endif
 720         case BLKTRACESTART:
 721                 start = 1;
 722                 /* fall through */
 723         case BLKTRACESTOP:
 724                 ret = __blk_trace_startstop(q, start);
 725                 break;
 726         case BLKTRACETEARDOWN:
 727                 ret = __blk_trace_remove(q);
 728                 break;
 729         default:
 730                 ret = -ENOTTY;
 731                 break;
 732         }
 733
 734         mutex_unlock(&q->blk_trace_mutex);
 735         return ret;
 736 }
 737
 738 /**
 739  * blk_trace_shutdown: - stop and cleanup trace structures
 740  * @q:    the request queue associated with the device
 741  *
 742  **/
 743 void blk_trace_shutdown(struct request_queue *q)
 744 {
 745         mutex_lock(&q->blk_trace_mutex);
 746         if (rcu_dereference_protected(q->blk_trace,
 747                                       lockdep_is_held(&q->blk_trace_mutex))) {
 748                 __blk_trace_startstop(q, 0);
 749                 __blk_trace_remove(q);
 750         }
 751
 752         mutex_unlock(&q->blk_trace_mutex);
 753 }
 754
 755 #ifdef CONFIG_BLK_CGROUP
 756 static u64 blk_trace_bio_get_cgid(struct request_queue *q, struct bio *bio)
 757 {
 758         struct blk_trace *bt;
 759
 760         /* We don't use the 'bt' value here except as an optimization... */
 761         bt = rcu_dereference_protected(q->blk_trace, 1);
 762         if (!bt || !(blk_tracer_flags.val & TRACE_BLK_OPT_CGROUP))
 763                 return 0;
 764
 765         if (!bio->bi_blkg)
 766                 return 0;
 767         return cgroup_id(bio_blkcg(bio)->css.cgroup);
 768 }
 769 #else
 770 u64 blk_trace_bio_get_cgid(struct request_queue *q, struct bio *bio)
 771 {
 772         return 0;
 773 }
 774 #endif
 775
 776 static u64
 777 blk_trace_request_get_cgid(struct request_queue *q, struct request *rq)
 778 {
 779         if (!rq->bio)
 780                 return 0;
 781         /* Use the first bio */
 782         return blk_trace_bio_get_cgid(q, rq->bio);
 783 }
 784
 785 /*
 786  * blktrace probes
 787  */
 788
 789 /**
 790  * blk_add_trace_rq - Add a trace for a request oriented action
 791  * @rq:         the source request
 792  * @error:      return status to log
 793  * @nr_bytes:   number of completed bytes
 794  * @what:       the action
 795  * @cgid:       the cgroup info
 796  *
 797  * Description:
 798  *     Records an action against a request. Will log the bio offset + size.
 799  *
 800  **/
 801 static void blk_add_trace_rq(struct request *rq, int error,
 802                              unsigned int nr_bytes, u32 what, u64 cgid)
 803 {
 804         struct blk_trace *bt;
 805
 806         rcu_read_lock();
 807         bt = rcu_dereference(rq->q->blk_trace);
 808         if (likely(!bt)) {
 809                 rcu_read_unlock();
 810                 return;
 811         }
 812
 813         if (blk_rq_is_passthrough(rq))
 814                 what |= BLK_TC_ACT(BLK_TC_PC);
 815         else
 816                 what |= BLK_TC_ACT(BLK_TC_FS);
 817
 818         __blk_add_trace(bt, blk_rq_trace_sector(rq), nr_bytes, req_op(rq),
 819                         rq->cmd_flags, what, error, 0, NULL, cgid);
 820         rcu_read_unlock();
 821 }
 822
 823 static void blk_add_trace_rq_insert(void *ignore,
 824                                     struct request_queue *q, struct request *rq)
 825 {
 826         blk_add_trace_rq(rq, 0, blk_rq_bytes(rq), BLK_TA_INSERT,
 827                          blk_trace_request_get_cgid(q, rq));
 828 }
 829
 830 static void blk_add_trace_rq_issue(void *ignore,
 831                                    struct request_queue *q, struct request *rq)
 832 {
 833         blk_add_trace_rq(rq, 0, blk_rq_bytes(rq), BLK_TA_ISSUE,
 834                          blk_trace_request_get_cgid(q, rq));
 835 }
 836
 837 static void blk_add_trace_rq_requeue(void *ignore,
 838                                      struct request_queue *q,
 839                                      struct request *rq)
 840 {
 841         blk_add_trace_rq(rq, 0, blk_rq_bytes(rq), BLK_TA_REQUEUE,
 842                          blk_trace_request_get_cgid(q, rq));
 843 }
 844
 845 static void blk_add_trace_rq_complete(void *ignore, struct request *rq,
 846                         int error, unsigned int nr_bytes)
 847 {
 848         blk_add_trace_rq(rq, error, nr_bytes, BLK_TA_COMPLETE,
 849                          blk_trace_request_get_cgid(rq->q, rq));
 850 }
 851
 852 /**
 853  * blk_add_trace_bio - Add a trace for a bio oriented action
 854  * @q:          queue the io is for
 855  * @bio:        the source bio
 856  * @what:       the action
 857  * @error:      error, if any
 858  *
 859  * Description:
 860  *     Records an action against a bio. Will log the bio offset + size.
 861  *
 862  **/
 863 static void blk_add_trace_bio(struct request_queue *q, struct bio *bio,
 864                               u32 what, int error)
 865 {
 866         struct blk_trace *bt;
 867
 868         rcu_read_lock();
 869         bt = rcu_dereference(q->blk_trace);
 870         if (likely(!bt)) {
 871                 rcu_read_unlock();
 872                 return;
 873         }
 874
 875         __blk_add_trace(bt, bio->bi_iter.bi_sector, bio->bi_iter.bi_size,
 876                         bio_op(bio), bio->bi_opf, what, error, 0, NULL,
 877                         blk_trace_bio_get_cgid(q, bio));
 878         rcu_read_unlock();
 879 }
 880
 881 static void blk_add_trace_bio_bounce(void *ignore,
 882                                      struct request_queue *q, struct bio *bio)
 883 {
 884         blk_add_trace_bio(q, bio, BLK_TA_BOUNCE, 0);
 885 }
 886
 887 static void blk_add_trace_bio_complete(void *ignore,
 888                                        struct request_queue *q, struct bio *bio,
 889                                        int error)
 890 {
 891         blk_add_trace_bio(q, bio, BLK_TA_COMPLETE, error);
 892 }
 893
 894 static void blk_add_trace_bio_backmerge(void *ignore,
 895                                         struct request_queue *q,
 896                                         struct request *rq,
 897                                         struct bio *bio)
 898 {
 899         blk_add_trace_bio(q, bio, BLK_TA_BACKMERGE, 0);
 900 }
 901
 902 static void blk_add_trace_bio_frontmerge(void *ignore,
 903                                          struct request_queue *q,
 904                                          struct request *rq,
 905                                          struct bio *bio)
 906 {
 907         blk_add_trace_bio(q, bio, BLK_TA_FRONTMERGE, 0);
 908 }
 909
 910 static void blk_add_trace_bio_queue(void *ignore,
 911                                     struct request_queue *q, struct bio *bio)
 912 {
 913         blk_add_trace_bio(q, bio, BLK_TA_QUEUE, 0);
 914 }
 915
 916 static void blk_add_trace_getrq(void *ignore,
 917                                 struct request_queue *q,
 918                                 struct bio *bio, int rw)
 919 {
 920         if (bio)
 921                 blk_add_trace_bio(q, bio, BLK_TA_GETRQ, 0);
 922         else {
 923                 struct blk_trace *bt;
 924
 925                 rcu_read_lock();
 926                 bt = rcu_dereference(q->blk_trace);
 927                 if (bt)
 928                         __blk_add_trace(bt, 0, 0, rw, 0, BLK_TA_GETRQ, 0, 0,
 929                                         NULL, 0);
 930                 rcu_read_unlock();
 931         }
 932 }
 933
 934
 935 static void blk_add_trace_sleeprq(void *ignore,
 936                                   struct request_queue *q,
 937                                   struct bio *bio, int rw)
 938 {
 939         if (bio)
 940                 blk_add_trace_bio(q, bio, BLK_TA_SLEEPRQ, 0);
 941         else {
 942                 struct blk_trace *bt;
 943
 944                 rcu_read_lock();
 945                 bt = rcu_dereference(q->blk_trace);
 946                 if (bt)
 947                         __blk_add_trace(bt, 0, 0, rw, 0, BLK_TA_SLEEPRQ,
 948                                         0, 0, NULL, 0);
 949                 rcu_read_unlock();
 950         }
 951 }
 952
 953 static void blk_add_trace_plug(void *ignore, struct request_queue *q)
 954 {
 955         struct blk_trace *bt;
 956
 957         rcu_read_lock();
 958         bt = rcu_dereference(q->blk_trace);
 959         if (bt)
 960                 __blk_add_trace(bt, 0, 0, 0, 0, BLK_TA_PLUG, 0, 0, NULL, 0);
 961         rcu_read_unlock();
 962 }
 963
 964 static void blk_add_trace_unplug(void *ignore, struct request_queue *q,
 965                                     unsigned int depth, bool explicit)
 966 {
 967         struct blk_trace *bt;
 968
 969         rcu_read_lock();
 970         bt = rcu_dereference(q->blk_trace);
 971         if (bt) {
 972                 __be64 rpdu = cpu_to_be64(depth);
 973                 u32 what;
 974
 975                 if (explicit)
 976                         what = BLK_TA_UNPLUG_IO;
 977                 else
 978                         what = BLK_TA_UNPLUG_TIMER;
 979
 980                 __blk_add_trace(bt, 0, 0, 0, 0, what, 0, sizeof(rpdu), &rpdu, 0);
 981         }
 982         rcu_read_unlock();
 983 }
 984
 985 static void blk_add_trace_split(void *ignore,
 986                                 struct request_queue *q, struct bio *bio,
 987                                 unsigned int pdu)
 988 {
 989         struct blk_trace *bt;
 990
 991         rcu_read_lock();
 992         bt = rcu_dereference(q->blk_trace);
 993         if (bt) {
 994                 __be64 rpdu = cpu_to_be64(pdu);
 995
 996                 __blk_add_trace(bt, bio->bi_iter.bi_sector,
 997                                 bio->bi_iter.bi_size, bio_op(bio), bio->bi_opf,
 998                                 BLK_TA_SPLIT, bio->bi_status, sizeof(rpdu),
 999                                 &rpdu, blk_trace_bio_get_cgid(q, bio));
1000         }
1001         rcu_read_unlock();
1002 }
1003
1004 /**
1005  * blk_add_trace_bio_remap - Add a trace for a bio-remap operation
1006  * @ignore:     trace callback data parameter (not used)
1007  * @q:          queue the io is for
1008  * @bio:        the source bio
1009  * @dev:        target device
1010  * @from:       source sector
1011  *
1012  * Description:
1013  *     Device mapper or raid target sometimes need to split a bio because
1014  *     it spans a stripe (or similar). Add a trace for that action.
1015  *
1016  **/
1017 static void blk_add_trace_bio_remap(void *ignore,
1018                                     struct request_queue *q, struct bio *bio,
1019                                     dev_t dev, sector_t from)
1020 {
1021         struct blk_trace *bt;
1022         struct blk_io_trace_remap r;
1023
1024         rcu_read_lock();
1025         bt = rcu_dereference(q->blk_trace);
1026         if (likely(!bt)) {
1027                 rcu_read_unlock();
1028                 return;
1029         }
1030
1031         r.device_from = cpu_to_be32(dev);
1032         r.device_to   = cpu_to_be32(bio_dev(bio));
1033         r.sector_from = cpu_to_be64(from);
1034
1035         __blk_add_trace(bt, bio->bi_iter.bi_sector, bio->bi_iter.bi_size,
1036                         bio_op(bio), bio->bi_opf, BLK_TA_REMAP, bio->bi_status,
1037                         sizeof(r), &r, blk_trace_bio_get_cgid(q, bio));
1038         rcu_read_unlock();
1039 }
1040
1041 /**
1042  * blk_add_trace_rq_remap - Add a trace for a request-remap operation
1043  * @ignore:     trace callback data parameter (not used)
1044  * @q:          queue the io is for
1045  * @rq:         the source request
1046  * @dev:        target device
1047  * @from:       source sector
1048  *
1049  * Description:
1050  *     Device mapper remaps request to other devices.
1051  *     Add a trace for that action.
1052  *
1053  **/
1054 static void blk_add_trace_rq_remap(void *ignore,
1055                                    struct request_queue *q,
1056                                    struct request *rq, dev_t dev,
1057                                    sector_t from)
1058 {
1059         struct blk_trace *bt;
1060         struct blk_io_trace_remap r;
1061
1062         rcu_read_lock();
1063         bt = rcu_dereference(q->blk_trace);
1064         if (likely(!bt)) {
1065                 rcu_read_unlock();
1066                 return;
1067         }
1068
1069         r.device_from = cpu_to_be32(dev);
1070         r.device_to   = cpu_to_be32(disk_devt(rq->rq_disk));
1071         r.sector_from = cpu_to_be64(from);
1072
1073         __blk_add_trace(bt, blk_rq_pos(rq), blk_rq_bytes(rq),
1074                         rq_data_dir(rq), 0, BLK_TA_REMAP, 0,
1075                         sizeof(r), &r, blk_trace_request_get_cgid(q, rq));
1076         rcu_read_unlock();
1077 }
1078
1079 /**
1080  * blk_add_driver_data - Add binary message with driver-specific data
1081  * @q:          queue the io is for
1082  * @rq:         io request
1083  * @data:       driver-specific data
1084  * @len:        length of driver-specific data
1085  *
1086  * Description:
1087  *     Some drivers might want to write driver-specific data per request.
1088  *
1089  **/
1090 void blk_add_driver_data(struct request_queue *q,
1091                          struct request *rq,
1092                          void *data, size_t len)
1093 {
1094         struct blk_trace *bt;
1095
1096         rcu_read_lock();
1097         bt = rcu_dereference(q->blk_trace);
1098         if (likely(!bt)) {
1099                 rcu_read_unlock();
1100                 return;
1101         }
1102
1103         __blk_add_trace(bt, blk_rq_trace_sector(rq), blk_rq_bytes(rq), 0, 0,
1104                                 BLK_TA_DRV_DATA, 0, len, data,
1105                                 blk_trace_request_get_cgid(q, rq));
1106         rcu_read_unlock();
1107 }
1108 EXPORT_SYMBOL_GPL(blk_add_driver_data);
1109
1110 static void blk_register_tracepoints(void)
1111 {
1112         int ret;
1113
1114         ret = register_trace_block_rq_insert(blk_add_trace_rq_insert, NULL);
1115         WARN_ON(ret);
1116         ret = register_trace_block_rq_issue(blk_add_trace_rq_issue, NULL);
1117         WARN_ON(ret);
1118         ret = register_trace_block_rq_requeue(blk_add_trace_rq_requeue, NULL);
1119         WARN_ON(ret);
1120         ret = register_trace_block_rq_complete(blk_add_trace_rq_complete, NULL);
1121         WARN_ON(ret);
1122         ret = register_trace_block_bio_bounce(blk_add_trace_bio_bounce, NULL);
1123         WARN_ON(ret);
1124         ret = register_trace_block_bio_complete(blk_add_trace_bio_complete, NULL);
1125         WARN_ON(ret);
1126         ret = register_trace_block_bio_backmerge(blk_add_trace_bio_backmerge, NULL);
1127         WARN_ON(ret);
1128         ret = register_trace_block_bio_frontmerge(blk_add_trace_bio_frontmerge, NULL);
1129         WARN_ON(ret);
1130         ret = register_trace_block_bio_queue(blk_add_trace_bio_queue, NULL);
1131         WARN_ON(ret);
1132         ret = register_trace_block_getrq(blk_add_trace_getrq, NULL);
1133         WARN_ON(ret);
1134         ret = register_trace_block_sleeprq(blk_add_trace_sleeprq, NULL);
1135         WARN_ON(ret);
1136         ret = register_trace_block_plug(blk_add_trace_plug, NULL);
1137         WARN_ON(ret);
1138         ret = register_trace_block_unplug(blk_add_trace_unplug, NULL);
1139         WARN_ON(ret);
1140         ret = register_trace_block_split(blk_add_trace_split, NULL);
1141         WARN_ON(ret);
1142         ret = register_trace_block_bio_remap(blk_add_trace_bio_remap, NULL);
1143         WARN_ON(ret);
1144         ret = register_trace_block_rq_remap(blk_add_trace_rq_remap, NULL);
1145         WARN_ON(ret);
1146 }
1147
1148 static void blk_unregister_tracepoints(void)
1149 {
1150         unregister_trace_block_rq_remap(blk_add_trace_rq_remap, NULL);
1151         unregister_trace_block_bio_remap(blk_add_trace_bio_remap, NULL);
1152         unregister_trace_block_split(blk_add_trace_split, NULL);
1153         unregister_trace_block_unplug(blk_add_trace_unplug, NULL);
1154         unregister_trace_block_plug(blk_add_trace_plug, NULL);
1155         unregister_trace_block_sleeprq(blk_add_trace_sleeprq, NULL);
1156         unregister_trace_block_getrq(blk_add_trace_getrq, NULL);
1157         unregister_trace_block_bio_queue(blk_add_trace_bio_queue, NULL);
1158         unregister_trace_block_bio_frontmerge(blk_add_trace_bio_frontmerge, NULL);
1159         unregister_trace_block_bio_backmerge(blk_add_trace_bio_backmerge, NULL);
1160         unregister_trace_block_bio_complete(blk_add_trace_bio_complete, NULL);
1161         unregister_trace_block_bio_bounce(blk_add_trace_bio_bounce, NULL);
1162         unregister_trace_block_rq_complete(blk_add_trace_rq_complete, NULL);
1163         unregister_trace_block_rq_requeue(blk_add_trace_rq_requeue, NULL);
1164         unregister_trace_block_rq_issue(blk_add_trace_rq_issue, NULL);
1165         unregister_trace_block_rq_insert(blk_add_trace_rq_insert, NULL);
1166
1167         tracepoint_synchronize_unregister();
1168 }
1169
1170 /*
1171  * struct blk_io_tracer formatting routines
1172  */
1173
1174 static void fill_rwbs(char *rwbs, const struct blk_io_trace *t)
1175 {
1176         int i = 0;
1177         int tc = t->action >> BLK_TC_SHIFT;
1178
1179         if ((t->action & ~__BLK_TN_CGROUP) == BLK_TN_MESSAGE) {
1180                 rwbs[i++] = 'N';
1181                 goto out;
1182         }
1183
1184         if (tc & BLK_TC_FLUSH)
1185                 rwbs[i++] = 'F';
1186
1187         if (tc & BLK_TC_DISCARD)
1188                 rwbs[i++] = 'D';
1189         else if (tc & BLK_TC_WRITE)
1190                 rwbs[i++] = 'W';
1191         else if (t->bytes)
1192                 rwbs[i++] = 'R';
1193         else
1194                 rwbs[i++] = 'N';
1195
1196         if (tc & BLK_TC_FUA)
1197                 rwbs[i++] = 'F';
1198         if (tc & BLK_TC_AHEAD)
1199                 rwbs[i++] = 'A';
1200         if (tc & BLK_TC_SYNC)
1201                 rwbs[i++] = 'S';
1202         if (tc & BLK_TC_META)
1203                 rwbs[i++] = 'M';
1204 out:
1205         rwbs[i] = '\0';
1206 }
1207
1208 static inline
1209 const struct blk_io_trace *te_blk_io_trace(const struct trace_entry *ent)
1210 {
1211         return (const struct blk_io_trace *)ent;
1212 }
1213
1214 static inline const void *pdu_start(const struct trace_entry *ent, bool has_cg)
1215 {
1216         return (void *)(te_blk_io_trace(ent) + 1) + (has_cg ? sizeof(u64) : 0);
1217 }
1218
1219 static inline u64 t_cgid(const struct trace_entry *ent)
1220 {
1221         return *(u64 *)(te_blk_io_trace(ent) + 1);
1222 }
1223
1224 static inline int pdu_real_len(const struct trace_entry *ent, bool has_cg)
1225 {
1226         return te_blk_io_trace(ent)->pdu_len - (has_cg ? sizeof(u64) : 0);
1227 }
1228
1229 static inline u32 t_action(const struct trace_entry *ent)
1230 {
1231         return te_blk_io_trace(ent)->action;
1232 }
1233
1234 static inline u32 t_bytes(const struct trace_entry *ent)
1235 {
1236         return te_blk_io_trace(ent)->bytes;
1237 }
1238
1239 static inline u32 t_sec(const struct trace_entry *ent)
1240 {
1241         return te_blk_io_trace(ent)->bytes >> 9;
1242 }
1243
1244 static inline unsigned long long t_sector(const struct trace_entry *ent)
1245 {
1246         return te_blk_io_trace(ent)->sector;
1247 }
1248
1249 static inline __u16 t_error(const struct trace_entry *ent)
1250 {
1251         return te_blk_io_trace(ent)->error;
1252 }
1253
1254 static __u64 get_pdu_int(const struct trace_entry *ent, bool has_cg)
1255 {
1256         const __u64 *val = pdu_start(ent, has_cg);
1257         return be64_to_cpu(*val);
1258 }
1259
1260 static void get_pdu_remap(const struct trace_entry *ent,
1261                           struct blk_io_trace_remap *r, bool has_cg)
1262 {
1263         const struct blk_io_trace_remap *__r = pdu_start(ent, has_cg);
1264         __u64 sector_from = __r->sector_from;
1265
1266         r->device_from = be32_to_cpu(__r->device_from);
1267         r->device_to   = be32_to_cpu(__r->device_to);
1268         r->sector_from = be64_to_cpu(sector_from);
1269 }
1270
1271 typedef void (blk_log_action_t) (struct trace_iterator *iter, const char *act,
1272         bool has_cg);
1273
1274 static void blk_log_action_classic(struct trace_iterator *iter, const char *act,
1275         bool has_cg)
1276 {
1277         char rwbs[RWBS_LEN];
1278         unsigned long long ts  = iter->ts;
1279         unsigned long nsec_rem = do_div(ts, NSEC_PER_SEC);
1280         unsigned secs          = (unsigned long)ts;
1281         const struct blk_io_trace *t = te_blk_io_trace(iter->ent);
1282
1283         fill_rwbs(rwbs, t);
1284
1285         trace_seq_printf(&iter->seq,
1286                          "%3d,%-3d %2d %5d.%09lu %5u %2s %3s ",
1287                          MAJOR(t->device), MINOR(t->device), iter->cpu,
1288                          secs, nsec_rem, iter->ent->pid, act, rwbs);
1289 }
1290
1291 static void blk_log_action(struct trace_iterator *iter, const char *act,
1292         bool has_cg)
1293 {
1294         char rwbs[RWBS_LEN];
1295         const struct blk_io_trace *t = te_blk_io_trace(iter->ent);
1296
1297         fill_rwbs(rwbs, t);
1298         if (has_cg) {
1299                 u64 id = t_cgid(iter->ent);
1300
1301                 if (blk_tracer_flags.val & TRACE_BLK_OPT_CGNAME) {
1302                         char blkcg_name_buf[NAME_MAX + 1] = "<...>";
1303
1304                         cgroup_path_from_kernfs_id(id, blkcg_name_buf,
1305                                 sizeof(blkcg_name_buf));
1306                         trace_seq_printf(&iter->seq, "%3d,%-3d %s %2s %3s ",
1307                                  MAJOR(t->device), MINOR(t->device),
1308                                  blkcg_name_buf, act, rwbs);
1309                 } else {
1310                         /*
1311                          * The cgid portion used to be "INO,GEN".  Userland
1312                          * builds a FILEID_INO32_GEN fid out of them and
1313                          * opens the cgroup using open_by_handle_at(2).
1314                          * While 32bit ino setups are still the same, 64bit
1315                          * ones now use the 64bit ino as the whole ID and
1316                          * no longer use generation.
1317                          *
1318                          * Regarldess of the content, always output
1319                          * "LOW32,HIGH32" so that FILEID_INO32_GEN fid can
1320                          * be mapped back to @id on both 64 and 32bit ino
1321                          * setups.  See __kernfs_fh_to_dentry().
1322                          */
1323                         trace_seq_printf(&iter->seq,
1324                                  "%3d,%-3d %llx,%-llx %2s %3s ",
1325                                  MAJOR(t->device), MINOR(t->device),
1326                                  id & U32_MAX, id >> 32, act, rwbs);
1327                 }
1328         } else
1329                 trace_seq_printf(&iter->seq, "%3d,%-3d %2s %3s ",
1330                                  MAJOR(t->device), MINOR(t->device), act, rwbs);
1331 }
1332
1333 static void blk_log_dump_pdu(struct trace_seq *s,
1334         const struct trace_entry *ent, bool has_cg)
1335 {
1336         const unsigned char *pdu_buf;
1337         int pdu_len;
1338         int i, end;
1339
1340         pdu_buf = pdu_start(ent, has_cg);
1341         pdu_len = pdu_real_len(ent, has_cg);
1342
1343         if (!pdu_len)
1344                 return;
1345
1346         /* find the last zero that needs to be printed */
1347         for (end = pdu_len - 1; end >= 0; end--)
1348                 if (pdu_buf[end])
1349                         break;
1350         end++;
1351
1352         trace_seq_putc(s, '(');
1353
1354         for (i = 0; i < pdu_len; i++) {
1355
1356                 trace_seq_printf(s, "%s%02x",
1357                                  i == 0 ? "" : " ", pdu_buf[i]);
1358
1359                 /*
1360                  * stop when the rest is just zeroes and indicate so
1361                  * with a ".." appended
1362                  */
1363                 if (i == end && end != pdu_len - 1) {
1364                         trace_seq_puts(s, " ..) ");
1365                         return;
1366                 }
1367         }
1368
1369         trace_seq_puts(s, ") ");
1370 }
1371
1372 static void blk_log_generic(struct trace_seq *s, const struct trace_entry *ent, bool has_cg)
1373 {
1374         char cmd[TASK_COMM_LEN];
1375
1376         trace_find_cmdline(ent->pid, cmd);
1377
1378         if (t_action(ent) & BLK_TC_ACT(BLK_TC_PC)) {
1379                 trace_seq_printf(s, "%u ", t_bytes(ent));
1380                 blk_log_dump_pdu(s, ent, has_cg);
1381                 trace_seq_printf(s, "[%s]\n", cmd);
1382         } else {
1383                 if (t_sec(ent))
1384                         trace_seq_printf(s, "%llu + %u [%s]\n",
1385                                                 t_sector(ent), t_sec(ent), cmd);
1386                 else
1387                         trace_seq_printf(s, "[%s]\n", cmd);
1388         }
1389 }
1390
1391 static void blk_log_with_error(struct trace_seq *s,
1392                               const struct trace_entry *ent, bool has_cg)
1393 {
1394         if (t_action(ent) & BLK_TC_ACT(BLK_TC_PC)) {
1395                 blk_log_dump_pdu(s, ent, has_cg);
1396                 trace_seq_printf(s, "[%d]\n", t_error(ent));
1397         } else {
1398                 if (t_sec(ent))
1399                         trace_seq_printf(s, "%llu + %u [%d]\n",
1400                                          t_sector(ent),
1401                                          t_sec(ent), t_error(ent));
1402                 else
1403                         trace_seq_printf(s, "%llu [%d]\n",
1404                                          t_sector(ent), t_error(ent));
1405         }
1406 }
1407
1408 static void blk_log_remap(struct trace_seq *s, const struct trace_entry *ent, bool has_cg)
1409 {
1410         struct blk_io_trace_remap r = { .device_from = 0, };
1411
1412         get_pdu_remap(ent, &r, has_cg);
1413         trace_seq_printf(s, "%llu + %u <- (%d,%d) %llu\n",
1414                          t_sector(ent), t_sec(ent),
1415                          MAJOR(r.device_from), MINOR(r.device_from),
1416                          (unsigned long long)r.sector_from);
1417 }
1418
1419 static void blk_log_plug(struct trace_seq *s, const struct trace_entry *ent, bool has_cg)
1420 {
1421         char cmd[TASK_COMM_LEN];
1422
1423         trace_find_cmdline(ent->pid, cmd);
1424
1425         trace_seq_printf(s, "[%s]\n", cmd);
1426 }
1427
1428 static void blk_log_unplug(struct trace_seq *s, const struct trace_entry *ent, bool has_cg)
1429 {
1430         char cmd[TASK_COMM_LEN];
1431
1432         trace_find_cmdline(ent->pid, cmd);
1433
1434         trace_seq_printf(s, "[%s] %llu\n", cmd, get_pdu_int(ent, has_cg));
1435 }
1436
1437 static void blk_log_split(struct trace_seq *s, const struct trace_entry *ent, bool has_cg)
1438 {
1439         char cmd[TASK_COMM_LEN];
1440
1441         trace_find_cmdline(ent->pid, cmd);
1442
1443         trace_seq_printf(s, "%llu / %llu [%s]\n", t_sector(ent),
1444                          get_pdu_int(ent, has_cg), cmd);
1445 }
1446
1447 static void blk_log_msg(struct trace_seq *s, const struct trace_entry *ent,
1448                         bool has_cg)
1449 {
1450
1451         trace_seq_putmem(s, pdu_start(ent, has_cg),
1452                 pdu_real_len(ent, has_cg));
1453         trace_seq_putc(s, '\n');
1454 }
1455
1456 /*
1457  * struct tracer operations
1458  */
1459
1460 static void blk_tracer_print_header(struct seq_file *m)
1461 {
1462         if (!(blk_tracer_flags.val & TRACE_BLK_OPT_CLASSIC))
1463                 return;
1464         seq_puts(m, "# DEV   CPU TIMESTAMP     PID ACT FLG\n"
1465                     "#  |     |     |           |   |   |\n");
1466 }
1467
1468 static void blk_tracer_start(struct trace_array *tr)
1469 {
1470         blk_tracer_enabled = true;
1471 }
1472
1473 static int blk_tracer_init(struct trace_array *tr)
1474 {
1475         blk_tr = tr;
1476         blk_tracer_start(tr);
1477         return 0;
1478 }
1479
1480 static void blk_tracer_stop(struct trace_array *tr)
1481 {
1482         blk_tracer_enabled = false;
1483 }
1484
1485 static void blk_tracer_reset(struct trace_array *tr)
1486 {
1487         blk_tracer_stop(tr);
1488 }
1489
1490 static const struct {
1491         const char *act[2];
1492         void       (*print)(struct trace_seq *s, const struct trace_entry *ent,
1493                             bool has_cg);
1494 } what2act[] = {
1495         [__BLK_TA_QUEUE]        = {{  "Q", "queue" },      blk_log_generic },
1496         [__BLK_TA_BACKMERGE]    = {{  "M", "backmerge" },  blk_log_generic },
1497         [__BLK_TA_FRONTMERGE]   = {{  "F", "frontmerge" }, blk_log_generic },
1498         [__BLK_TA_GETRQ]        = {{  "G", "getrq" },      blk_log_generic },
1499         [__BLK_TA_SLEEPRQ]      = {{  "S", "sleeprq" },    blk_log_generic },
1500         [__BLK_TA_REQUEUE]      = {{  "R", "requeue" },    blk_log_with_error },
1501         [__BLK_TA_ISSUE]        = {{  "D", "issue" },      blk_log_generic },
1502         [__BLK_TA_COMPLETE]     = {{  "C", "complete" },   blk_log_with_error },
1503         [__BLK_TA_PLUG]         = {{  "P", "plug" },       blk_log_plug },
1504         [__BLK_TA_UNPLUG_IO]    = {{  "U", "unplug_io" },  blk_log_unplug },
1505         [__BLK_TA_UNPLUG_TIMER] = {{ "UT", "unplug_timer" }, blk_log_unplug },
1506         [__BLK_TA_INSERT]       = {{  "I", "insert" },     blk_log_generic },
1507         [__BLK_TA_SPLIT]        = {{  "X", "split" },      blk_log_split },
1508         [__BLK_TA_BOUNCE]       = {{  "B", "bounce" },     blk_log_generic },
1509         [__BLK_TA_REMAP]        = {{  "A", "remap" },      blk_log_remap },
1510 };
1511
1512 static enum print_line_t print_one_line(struct trace_iterator *iter,
1513                                         bool classic)
1514 {
1515         struct trace_array *tr = iter->tr;
1516         struct trace_seq *s = &iter->seq;
1517         const struct blk_io_trace *t;
1518         u16 what;
1519         bool long_act;
1520         blk_log_action_t *log_action;
1521         bool has_cg;
1522
1523         t          = te_blk_io_trace(iter->ent);
1524         what       = (t->action & ((1 << BLK_TC_SHIFT) - 1)) & ~__BLK_TA_CGROUP;
1525         long_act   = !!(tr->trace_flags & TRACE_ITER_VERBOSE);
1526         log_action = classic ? &blk_log_action_classic : &blk_log_action;
1527         has_cg     = t->action & __BLK_TA_CGROUP;
1528
1529         if ((t->action & ~__BLK_TN_CGROUP) == BLK_TN_MESSAGE) {
1530                 log_action(iter, long_act ? "message" : "m", has_cg);
1531                 blk_log_msg(s, iter->ent, has_cg);
1532                 return trace_handle_return(s);
1533         }
1534
1535         if (unlikely(what == 0 || what >= ARRAY_SIZE(what2act)))
1536                 trace_seq_printf(s, "Unknown action %x\n", what);
1537         else {
1538                 log_action(iter, what2act[what].act[long_act], has_cg);
1539                 what2act[what].print(s, iter->ent, has_cg);
1540         }
1541
1542         return trace_handle_return(s);
1543 }
1544
1545 static enum print_line_t blk_trace_event_print(struct trace_iterator *iter,
1546                                                int flags, struct trace_event *event)
1547 {
1548         return print_one_line(iter, false);
1549 }
1550
1551 static void blk_trace_synthesize_old_trace(struct trace_iterator *iter)
1552 {
1553         struct trace_seq *s = &iter->seq;
1554         struct blk_io_trace *t = (struct blk_io_trace *)iter->ent;
1555         const int offset = offsetof(struct blk_io_trace, sector);
1556         struct blk_io_trace old = {
1557                 .magic    = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION,
1558                 .time     = iter->ts,
1559         };
1560
1561         trace_seq_putmem(s, &old, offset);
1562         trace_seq_putmem(s, &t->sector,
1563                          sizeof(old) - offset + t->pdu_len);
1564 }
1565
1566 static enum print_line_t
1567 blk_trace_event_print_binary(struct trace_iterator *iter, int flags,
1568                              struct trace_event *event)
1569 {
1570         blk_trace_synthesize_old_trace(iter);
1571
1572         return trace_handle_return(&iter->seq);
1573 }
1574
1575 static enum print_line_t blk_tracer_print_line(struct trace_iterator *iter)
1576 {
1577         if (!(blk_tracer_flags.val & TRACE_BLK_OPT_CLASSIC))
1578                 return TRACE_TYPE_UNHANDLED;
1579
1580         return print_one_line(iter, true);
1581 }
1582
1583 static int
1584 blk_tracer_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
1585 {
1586         /* don't output context-info for blk_classic output */
1587         if (bit == TRACE_BLK_OPT_CLASSIC) {
1588                 if (set)
1589                         tr->trace_flags &= ~TRACE_ITER_CONTEXT_INFO;
1590                 else
1591                         tr->trace_flags |= TRACE_ITER_CONTEXT_INFO;
1592         }
1593         return 0;
1594 }
1595
1596 static struct tracer blk_tracer __read_mostly = {
1597         .name           = "blk",
1598         .init           = blk_tracer_init,
1599         .reset          = blk_tracer_reset,
1600         .start          = blk_tracer_start,
1601         .stop           = blk_tracer_stop,
1602         .print_header   = blk_tracer_print_header,
1603         .print_line     = blk_tracer_print_line,
1604         .flags          = &blk_tracer_flags,
1605         .set_flag       = blk_tracer_set_flag,
1606 };
1607
1608 static struct trace_event_functions trace_blk_event_funcs = {
1609         .trace          = blk_trace_event_print,
1610         .binary         = blk_trace_event_print_binary,
1611 };
1612
1613 static struct trace_event trace_blk_event = {
1614         .type           = TRACE_BLK,
1615         .funcs          = &trace_blk_event_funcs,
1616 };
1617
1618 static int __init init_blk_tracer(void)
1619 {
1620         if (!register_trace_event(&trace_blk_event)) {
1621                 pr_warn("Warning: could not register block events\n");
1622                 return 1;
1623         }
1624
1625         if (register_tracer(&blk_tracer) != 0) {
1626                 pr_warn("Warning: could not register the block tracer\n");
1627                 unregister_trace_event(&trace_blk_event);
1628                 return 1;
1629         }
1630
1631         return 0;
1632 }
1633
1634 device_initcall(init_blk_tracer);
1635
1636 static int blk_trace_remove_queue(struct request_queue *q)
1637 {
1638         struct blk_trace *bt;
1639
1640         bt = xchg(&q->blk_trace, NULL);
1641         if (bt == NULL)
1642                 return -EINVAL;
1643
1644         put_probe_ref();
1645         synchronize_rcu();
1646         blk_trace_free(bt);
1647         return 0;
1648 }
1649
1650 /*
1651  * Setup everything required to start tracing
1652  */
1653 static int blk_trace_setup_queue(struct request_queue *q,
1654                                  struct block_device *bdev)
1655 {
1656         struct blk_trace *bt = NULL;
1657         int ret = -ENOMEM;
1658
1659         bt = kzalloc(sizeof(*bt), GFP_KERNEL);
1660         if (!bt)
1661                 return -ENOMEM;
1662
1663         bt->msg_data = __alloc_percpu(BLK_TN_MAX_MSG, __alignof__(char));
1664         if (!bt->msg_data)
1665                 goto free_bt;
1666
1667         bt->dev = bdev->bd_dev;
1668         bt->act_mask = (u16)-1;
1669
1670         blk_trace_setup_lba(bt, bdev);
1671
1672         ret = -EBUSY;
1673         if (cmpxchg(&q->blk_trace, NULL, bt))
1674                 goto free_bt;
1675
1676         get_probe_ref();
1677         return 0;
1678
1679 free_bt:
1680         blk_trace_free(bt);
1681         return ret;
1682 }
1683
1684 /*
1685  * sysfs interface to enable and configure tracing
1686  */
1687
1688 static ssize_t sysfs_blk_trace_attr_show(struct device *dev,
1689                                          struct device_attribute *attr,
1690                                          char *buf);
1691 static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
1692                                           struct device_attribute *attr,
1693                                           const char *buf, size_t count);
1694 #define BLK_TRACE_DEVICE_ATTR(_name) \
1695         DEVICE_ATTR(_name, S_IRUGO | S_IWUSR, \
1696                     sysfs_blk_trace_attr_show, \
1697                     sysfs_blk_trace_attr_store)
1698
1699 static BLK_TRACE_DEVICE_ATTR(enable);
1700 static BLK_TRACE_DEVICE_ATTR(act_mask);
1701 static BLK_TRACE_DEVICE_ATTR(pid);
1702 static BLK_TRACE_DEVICE_ATTR(start_lba);
1703 static BLK_TRACE_DEVICE_ATTR(end_lba);
1704
1705 static struct attribute *blk_trace_attrs[] = {
1706         &dev_attr_enable.attr,
1707         &dev_attr_act_mask.attr,
1708         &dev_attr_pid.attr,
1709         &dev_attr_start_lba.attr,
1710         &dev_attr_end_lba.attr,
1711         NULL
1712 };
1713
1714 struct attribute_group blk_trace_attr_group = {
1715         .name  = "trace",
1716         .attrs = blk_trace_attrs,
1717 };
1718
1719 static const struct {
1720         int mask;
1721         const char *str;
1722 } mask_maps[] = {
1723         { BLK_TC_READ,          "read"          },
1724         { BLK_TC_WRITE,         "write"         },
1725         { BLK_TC_FLUSH,         "flush"         },
1726         { BLK_TC_SYNC,          "sync"          },
1727         { BLK_TC_QUEUE,         "queue"         },
1728         { BLK_TC_REQUEUE,       "requeue"       },
1729         { BLK_TC_ISSUE,         "issue"         },
1730         { BLK_TC_COMPLETE,      "complete"      },
1731         { BLK_TC_FS,            "fs"            },
1732         { BLK_TC_PC,            "pc"            },
1733         { BLK_TC_NOTIFY,        "notify"        },
1734         { BLK_TC_AHEAD,         "ahead"         },
1735         { BLK_TC_META,          "meta"          },
1736         { BLK_TC_DISCARD,       "discard"       },
1737         { BLK_TC_DRV_DATA,      "drv_data"      },
1738         { BLK_TC_FUA,           "fua"           },
1739 };
1740
1741 static int blk_trace_str2mask(const char *str)
1742 {
1743         int i;
1744         int mask = 0;
1745         char *buf, *s, *token;
1746
1747         buf = kstrdup(str, GFP_KERNEL);
1748         if (buf == NULL)
1749                 return -ENOMEM;
1750         s = strstrip(buf);
1751
1752         while (1) {
1753                 token = strsep(&s, ",");
1754                 if (token == NULL)
1755                         break;
1756
1757                 if (*token == '\0')
1758                         continue;
1759
1760                 for (i = 0; i < ARRAY_SIZE(mask_maps); i++) {
1761                         if (strcasecmp(token, mask_maps[i].str) == 0) {
1762                                 mask |= mask_maps[i].mask;
1763                                 break;
1764                         }
1765                 }
1766                 if (i == ARRAY_SIZE(mask_maps)) {
1767                         mask = -EINVAL;
1768                         break;
1769                 }
1770         }
1771         kfree(buf);
1772
1773         return mask;
1774 }
1775
1776 static ssize_t blk_trace_mask2str(char *buf, int mask)
1777 {
1778         int i;
1779         char *p = buf;
1780
1781         for (i = 0; i < ARRAY_SIZE(mask_maps); i++) {
1782                 if (mask & mask_maps[i].mask) {
1783                         p += sprintf(p, "%s%s",
1784                                     (p == buf) ? "" : ",", mask_maps[i].str);
1785                 }
1786         }
1787         *p++ = '\n';
1788
1789         return p - buf;
1790 }
1791
1792 static struct request_queue *blk_trace_get_queue(struct block_device *bdev)
1793 {
1794         if (bdev->bd_disk == NULL)
1795                 return NULL;
1796
1797         return bdev_get_queue(bdev);
1798 }
1799
1800 static ssize_t sysfs_blk_trace_attr_show(struct device *dev,
1801                                          struct device_attribute *attr,
1802                                          char *buf)
1803 {
1804         struct hd_struct *p = dev_to_part(dev);
1805         struct request_queue *q;
1806         struct block_device *bdev;
1807         struct blk_trace *bt;
1808         ssize_t ret = -ENXIO;
1809
1810         bdev = bdget(part_devt(p));
1811         if (bdev == NULL)
1812                 goto out;
1813
1814         q = blk_trace_get_queue(bdev);
1815         if (q == NULL)
1816                 goto out_bdput;
1817
1818         mutex_lock(&q->blk_trace_mutex);
1819
1820         bt = rcu_dereference_protected(q->blk_trace,
1821                                        lockdep_is_held(&q->blk_trace_mutex));
1822         if (attr == &dev_attr_enable) {
1823                 ret = sprintf(buf, "%u\n", !!bt);
1824                 goto out_unlock_bdev;
1825         }
1826
1827         if (bt == NULL)
1828                 ret = sprintf(buf, "disabled\n");
1829         else if (attr == &dev_attr_act_mask)
1830                 ret = blk_trace_mask2str(buf, bt->act_mask);
1831         else if (attr == &dev_attr_pid)
1832                 ret = sprintf(buf, "%u\n", bt->pid);
1833         else if (attr == &dev_attr_start_lba)
1834                 ret = sprintf(buf, "%llu\n", bt->start_lba);
1835         else if (attr == &dev_attr_end_lba)
1836                 ret = sprintf(buf, "%llu\n", bt->end_lba);
1837
1838 out_unlock_bdev:
1839         mutex_unlock(&q->blk_trace_mutex);
1840 out_bdput:
1841         bdput(bdev);
1842 out:
1843         return ret;
1844 }
1845
1846 static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
1847                                           struct device_attribute *attr,
1848                                           const char *buf, size_t count)
1849 {
1850         struct block_device *bdev;
1851         struct request_queue *q;
1852         struct hd_struct *p;
1853         struct blk_trace *bt;
1854         u64 value;
1855         ssize_t ret = -EINVAL;
1856
1857         if (count == 0)
1858                 goto out;
1859
1860         if (attr == &dev_attr_act_mask) {
1861                 if (kstrtoull(buf, 0, &value)) {
1862                         /* Assume it is a list of trace category names */
1863                         ret = blk_trace_str2mask(buf);
1864                         if (ret < 0)
1865                                 goto out;
1866                         value = ret;
1867                 }
1868         } else if (kstrtoull(buf, 0, &value))
1869                 goto out;
1870
1871         ret = -ENXIO;
1872
1873         p = dev_to_part(dev);
1874         bdev = bdget(part_devt(p));
1875         if (bdev == NULL)
1876                 goto out;
1877
1878         q = blk_trace_get_queue(bdev);
1879         if (q == NULL)
1880                 goto out_bdput;
1881
1882         mutex_lock(&q->blk_trace_mutex);
1883
1884         bt = rcu_dereference_protected(q->blk_trace,
1885                                        lockdep_is_held(&q->blk_trace_mutex));
1886         if (attr == &dev_attr_enable) {
1887                 if (!!value == !!bt) {
1888                         ret = 0;
1889                         goto out_unlock_bdev;
1890                 }
1891                 if (value)
1892                         ret = blk_trace_setup_queue(q, bdev);
1893                 else
1894                         ret = blk_trace_remove_queue(q);
1895                 goto out_unlock_bdev;
1896         }
1897
1898         ret = 0;
1899         if (bt == NULL)
1900                 ret = blk_trace_setup_queue(q, bdev);
1901
1902         if (ret == 0) {
1903                 if (attr == &dev_attr_act_mask)
1904                         bt->act_mask = value;
1905                 else if (attr == &dev_attr_pid)
1906                         bt->pid = value;
1907                 else if (attr == &dev_attr_start_lba)
1908                         bt->start_lba = value;
1909                 else if (attr == &dev_attr_end_lba)
1910                         bt->end_lba = value;
1911         }
1912
1913 out_unlock_bdev:
1914         mutex_unlock(&q->blk_trace_mutex);
1915 out_bdput:
1916         bdput(bdev);
1917 out:
1918         return ret ? ret : count;
1919 }
1920
1921 int blk_trace_init_sysfs(struct device *dev)
1922 {
1923         return sysfs_create_group(&dev->kobj, &blk_trace_attr_group);
1924 }
1925
1926 void blk_trace_remove_sysfs(struct device *dev)
1927 {
1928         sysfs_remove_group(&dev->kobj, &blk_trace_attr_group);
1929 }
1930
1931 #endif /* CONFIG_BLK_DEV_IO_TRACE */
1932
1933 #ifdef CONFIG_EVENT_TRACING
1934
1935 void blk_fill_rwbs(char *rwbs, unsigned int op, int bytes)
1936 {
1937         int i = 0;
1938
1939         if (op & REQ_PREFLUSH)
1940                 rwbs[i++] = 'F';
1941
1942         switch (op & REQ_OP_MASK) {
1943         case REQ_OP_WRITE:
1944         case REQ_OP_WRITE_SAME:
1945                 rwbs[i++] = 'W';
1946                 break;
1947         case REQ_OP_DISCARD:
1948                 rwbs[i++] = 'D';
1949                 break;
1950         case REQ_OP_SECURE_ERASE:
1951                 rwbs[i++] = 'D';
1952                 rwbs[i++] = 'E';
1953                 break;
1954         case REQ_OP_FLUSH:
1955                 rwbs[i++] = 'F';
1956                 break;
1957         case REQ_OP_READ:
1958                 rwbs[i++] = 'R';
1959                 break;
1960         default:
1961                 rwbs[i++] = 'N';
1962         }
1963
1964         if (op & REQ_FUA)
1965                 rwbs[i++] = 'F';
1966         if (op & REQ_RAHEAD)
1967                 rwbs[i++] = 'A';
1968         if (op & REQ_SYNC)
1969                 rwbs[i++] = 'S';
1970         if (op & REQ_META)
1971                 rwbs[i++] = 'M';
1972
1973         rwbs[i] = '\0';
1974 }
1975 EXPORT_SYMBOL_GPL(blk_fill_rwbs);
1976
1977 #endif /* CONFIG_EVENT_TRACING */
1978