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