kernel/trace/blktrace.c

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