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