block/blktrace.c

   1 /*
   2  * Copyright (C) 2006 Jens Axboe <axboe@kernel.dk>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License
  14  * along with this program; if not, write to the Free Software
  15  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  16  *
  17  */
  18 #include <linux/kernel.h>
  19 #include <linux/blkdev.h>
  20 #include <linux/blktrace_api.h>
  21 #include <linux/percpu.h>
  22 #include <linux/init.h>
  23 #include <linux/mutex.h>
  24 #include <linux/debugfs.h>
  25 #include <linux/time.h>
  26 #include <asm/uaccess.h>
  27
  28 static DEFINE_PER_CPU(unsigned long long, blk_trace_cpu_offset) = { 0, };
  29 static unsigned int blktrace_seq __read_mostly = 1;
  30
  31 /*
  32  * Send out a notify message.
  33  */
  34 static inline unsigned int trace_note(struct blk_trace *bt,
  35                 pid_t pid, int action,
  36                 const void *data, size_t len)
  37 {
  38         struct blk_io_trace *t;
  39         int cpu = smp_processor_id();
  40
  41         t = relay_reserve(bt->rchan, sizeof(*t) + len);
  42         if (t == NULL)
  43                 return 0;
  44
  45         t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
  46         t->time = sched_clock() - per_cpu(blk_trace_cpu_offset, cpu);
  47         t->device = bt->dev;
  48         t->action = action;
  49         t->pid = pid;
  50         t->cpu = cpu;
  51         t->pdu_len = len;
  52         memcpy((void *) t + sizeof(*t), data, len);
  53         return blktrace_seq;
  54 }
  55
  56 /*
  57  * Send out a notify for this process, if we haven't done so since a trace
  58  * started
  59  */
  60 static void trace_note_tsk(struct blk_trace *bt, struct task_struct *tsk)
  61 {
  62         tsk->btrace_seq = trace_note(bt, tsk->pid,
  63                         BLK_TN_PROCESS,
  64                         tsk->comm, sizeof(tsk->comm));
  65 }
  66
  67 static void trace_note_time(struct blk_trace *bt)
  68 {
  69         struct timespec now;
  70         unsigned long flags;
  71         u32 words[2];
  72
  73         getnstimeofday(&now);
  74         words[0] = now.tv_sec;
  75         words[1] = now.tv_nsec;
  76
  77         local_irq_save(flags);
  78         trace_note(bt, 0, BLK_TN_TIMESTAMP, words, sizeof(words));
  79         local_irq_restore(flags);
  80 }
  81
  82 static int act_log_check(struct blk_trace *bt, u32 what, sector_t sector,
  83                          pid_t pid)
  84 {
  85         if (((bt->act_mask << BLK_TC_SHIFT) & what) == 0)
  86                 return 1;
  87         if (sector < bt->start_lba || sector > bt->end_lba)
  88                 return 1;
  89         if (bt->pid && pid != bt->pid)
  90                 return 1;
  91
  92         return 0;
  93 }
  94
  95 /*
  96  * Data direction bit lookup
  97  */
  98 static u32 ddir_act[2] __read_mostly = { BLK_TC_ACT(BLK_TC_READ), BLK_TC_ACT(BLK_TC_WRITE) };
  99
 100 /*
 101  * Bio action bits of interest
 102  */
 103 static u32 bio_act[9] __read_mostly = { 0, BLK_TC_ACT(BLK_TC_BARRIER), BLK_TC_ACT(BLK_TC_SYNC), 0, BLK_TC_ACT(BLK_TC_AHEAD), 0, 0, 0, BLK_TC_ACT(BLK_TC_META) };
 104
 105 /*
 106  * More could be added as needed, taking care to increment the decrementer
 107  * to get correct indexing
 108  */
 109 #define trace_barrier_bit(rw)   \
 110         (((rw) & (1 << BIO_RW_BARRIER)) >> (BIO_RW_BARRIER - 0))
 111 #define trace_sync_bit(rw)      \
 112         (((rw) & (1 << BIO_RW_SYNC)) >> (BIO_RW_SYNC - 1))
 113 #define trace_ahead_bit(rw)     \
 114         (((rw) & (1 << BIO_RW_AHEAD)) << (2 - BIO_RW_AHEAD))
 115 #define trace_meta_bit(rw)      \
 116         (((rw) & (1 << BIO_RW_META)) >> (BIO_RW_META - 3))
 117
 118 /*
 119  * The worker for the various blk_add_trace*() types. Fills out a
 120  * blk_io_trace structure and places it in a per-cpu subbuffer.
 121  */
 122 void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
 123                      int rw, u32 what, int error, int pdu_len, void *pdu_data)
 124 {
 125         struct task_struct *tsk = current;
 126         struct blk_io_trace *t;
 127         unsigned long flags;
 128         unsigned long *sequence;
 129         pid_t pid;
 130         int cpu;
 131
 132         if (unlikely(bt->trace_state != Blktrace_running))
 133                 return;
 134
 135         what |= ddir_act[rw & WRITE];
 136         what |= bio_act[trace_barrier_bit(rw)];
 137         what |= bio_act[trace_sync_bit(rw)];
 138         what |= bio_act[trace_ahead_bit(rw)];
 139         what |= bio_act[trace_meta_bit(rw)];
 140
 141         pid = tsk->pid;
 142         if (unlikely(act_log_check(bt, what, sector, pid)))
 143                 return;
 144
 145         /*
 146          * A word about the locking here - we disable interrupts to reserve
 147          * some space in the relay per-cpu buffer, to prevent an irq
 148          * from coming in and stepping on our toes. Once reserved, it's
 149          * enough to get preemption disabled to prevent read of this data
 150          * before we are through filling it. get_cpu()/put_cpu() does this
 151          * for us
 152          */
 153         local_irq_save(flags);
 154
 155         if (unlikely(tsk->btrace_seq != blktrace_seq))
 156                 trace_note_tsk(bt, tsk);
 157
 158         t = relay_reserve(bt->rchan, sizeof(*t) + pdu_len);
 159         if (t) {
 160                 cpu = smp_processor_id();
 161                 sequence = per_cpu_ptr(bt->sequence, cpu);
 162
 163                 t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
 164                 t->sequence = ++(*sequence);
 165                 t->time = sched_clock() - per_cpu(blk_trace_cpu_offset, cpu);
 166                 t->sector = sector;
 167                 t->bytes = bytes;
 168                 t->action = what;
 169                 t->pid = pid;
 170                 t->device = bt->dev;
 171                 t->cpu = cpu;
 172                 t->error = error;
 173                 t->pdu_len = pdu_len;
 174
 175                 if (pdu_len)
 176                         memcpy((void *) t + sizeof(*t), pdu_data, pdu_len);
 177         }
 178
 179         local_irq_restore(flags);
 180 }
 181
 182 EXPORT_SYMBOL_GPL(__blk_add_trace);
 183
 184 static struct dentry *blk_tree_root;
 185 static struct mutex blk_tree_mutex;
 186 static unsigned int root_users;
 187
 188 static inline void blk_remove_root(void)
 189 {
 190         if (blk_tree_root) {
 191                 debugfs_remove(blk_tree_root);
 192                 blk_tree_root = NULL;
 193         }
 194 }
 195
 196 static void blk_remove_tree(struct dentry *dir)
 197 {
 198         mutex_lock(&blk_tree_mutex);
 199         debugfs_remove(dir);
 200         if (--root_users == 0)
 201                 blk_remove_root();
 202         mutex_unlock(&blk_tree_mutex);
 203 }
 204
 205 static struct dentry *blk_create_tree(const char *blk_name)
 206 {
 207         struct dentry *dir = NULL;
 208
 209         mutex_lock(&blk_tree_mutex);
 210
 211         if (!blk_tree_root) {
 212                 blk_tree_root = debugfs_create_dir("block", NULL);
 213                 if (!blk_tree_root)
 214                         goto err;
 215         }
 216
 217         dir = debugfs_create_dir(blk_name, blk_tree_root);
 218         if (dir)
 219                 root_users++;
 220         else
 221                 blk_remove_root();
 222
 223 err:
 224         mutex_unlock(&blk_tree_mutex);
 225         return dir;
 226 }
 227
 228 static void blk_trace_cleanup(struct blk_trace *bt)
 229 {
 230         relay_close(bt->rchan);
 231         debugfs_remove(bt->dropped_file);
 232         blk_remove_tree(bt->dir);
 233         free_percpu(bt->sequence);
 234         kfree(bt);
 235 }
 236
 237 static int blk_trace_remove(request_queue_t *q)
 238 {
 239         struct blk_trace *bt;
 240
 241         bt = xchg(&q->blk_trace, NULL);
 242         if (!bt)
 243                 return -EINVAL;
 244
 245         if (bt->trace_state == Blktrace_setup ||
 246             bt->trace_state == Blktrace_stopped)
 247                 blk_trace_cleanup(bt);
 248
 249         return 0;
 250 }
 251
 252 static int blk_dropped_open(struct inode *inode, struct file *filp)
 253 {
 254         filp->private_data = inode->i_private;
 255
 256         return 0;
 257 }
 258
 259 static ssize_t blk_dropped_read(struct file *filp, char __user *buffer,
 260                                 size_t count, loff_t *ppos)
 261 {
 262         struct blk_trace *bt = filp->private_data;
 263         char buf[16];
 264
 265         snprintf(buf, sizeof(buf), "%u\n", atomic_read(&bt->dropped));
 266
 267         return simple_read_from_buffer(buffer, count, ppos, buf, strlen(buf));
 268 }
 269
 270 static struct file_operations blk_dropped_fops = {
 271         .owner =        THIS_MODULE,
 272         .open =         blk_dropped_open,
 273         .read =         blk_dropped_read,
 274 };
 275
 276 /*
 277  * Keep track of how many times we encountered a full subbuffer, to aid
 278  * the user space app in telling how many lost events there were.
 279  */
 280 static int blk_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
 281                                      void *prev_subbuf, size_t prev_padding)
 282 {
 283         struct blk_trace *bt;
 284
 285         if (!relay_buf_full(buf))
 286                 return 1;
 287
 288         bt = buf->chan->private_data;
 289         atomic_inc(&bt->dropped);
 290         return 0;
 291 }
 292
 293 static int blk_remove_buf_file_callback(struct dentry *dentry)
 294 {
 295         debugfs_remove(dentry);
 296         return 0;
 297 }
 298
 299 static struct dentry *blk_create_buf_file_callback(const char *filename,
 300                                                    struct dentry *parent,
 301                                                    int mode,
 302                                                    struct rchan_buf *buf,
 303                                                    int *is_global)
 304 {
 305         return debugfs_create_file(filename, mode, parent, buf,
 306                                         &relay_file_operations);
 307 }
 308
 309 static struct rchan_callbacks blk_relay_callbacks = {
 310         .subbuf_start           = blk_subbuf_start_callback,
 311         .create_buf_file        = blk_create_buf_file_callback,
 312         .remove_buf_file        = blk_remove_buf_file_callback,
 313 };
 314
 315 /*
 316  * Setup everything required to start tracing
 317  */
 318 static int blk_trace_setup(request_queue_t *q, struct block_device *bdev,
 319                            char __user *arg)
 320 {
 321         struct blk_user_trace_setup buts;
 322         struct blk_trace *old_bt, *bt = NULL;
 323         struct dentry *dir = NULL;
 324         char b[BDEVNAME_SIZE];
 325         int ret, i;
 326
 327         if (copy_from_user(&buts, arg, sizeof(buts)))
 328                 return -EFAULT;
 329
 330         if (!buts.buf_size || !buts.buf_nr)
 331                 return -EINVAL;
 332
 333         strcpy(buts.name, bdevname(bdev, b));
 334
 335         /*
 336          * some device names have larger paths - convert the slashes
 337          * to underscores for this to work as expected
 338          */
 339         for (i = 0; i < strlen(buts.name); i++)
 340                 if (buts.name[i] == '/')
 341                         buts.name[i] = '_';
 342
 343         if (copy_to_user(arg, &buts, sizeof(buts)))
 344                 return -EFAULT;
 345
 346         ret = -ENOMEM;
 347         bt = kzalloc(sizeof(*bt), GFP_KERNEL);
 348         if (!bt)
 349                 goto err;
 350
 351         bt->sequence = alloc_percpu(unsigned long);
 352         if (!bt->sequence)
 353                 goto err;
 354
 355         ret = -ENOENT;
 356         dir = blk_create_tree(buts.name);
 357         if (!dir)
 358                 goto err;
 359
 360         bt->dir = dir;
 361         bt->dev = bdev->bd_dev;
 362         atomic_set(&bt->dropped, 0);
 363
 364         ret = -EIO;
 365         bt->dropped_file = debugfs_create_file("dropped", 0444, dir, bt, &blk_dropped_fops);
 366         if (!bt->dropped_file)
 367                 goto err;
 368
 369         bt->rchan = relay_open("trace", dir, buts.buf_size, buts.buf_nr, &blk_relay_callbacks);
 370         if (!bt->rchan)
 371                 goto err;
 372         bt->rchan->private_data = bt;
 373
 374         bt->act_mask = buts.act_mask;
 375         if (!bt->act_mask)
 376                 bt->act_mask = (u16) -1;
 377
 378         bt->start_lba = buts.start_lba;
 379         bt->end_lba = buts.end_lba;
 380         if (!bt->end_lba)
 381                 bt->end_lba = -1ULL;
 382
 383         bt->pid = buts.pid;
 384         bt->trace_state = Blktrace_setup;
 385
 386         ret = -EBUSY;
 387         old_bt = xchg(&q->blk_trace, bt);
 388         if (old_bt) {
 389                 (void) xchg(&q->blk_trace, old_bt);
 390                 goto err;
 391         }
 392
 393         return 0;
 394 err:
 395         if (dir)
 396                 blk_remove_tree(dir);
 397         if (bt) {
 398                 if (bt->dropped_file)
 399                         debugfs_remove(bt->dropped_file);
 400                 if (bt->sequence)
 401                         free_percpu(bt->sequence);
 402                 if (bt->rchan)
 403                         relay_close(bt->rchan);
 404                 kfree(bt);
 405         }
 406         return ret;
 407 }
 408
 409 static int blk_trace_startstop(request_queue_t *q, int start)
 410 {
 411         struct blk_trace *bt;
 412         int ret;
 413
 414         if ((bt = q->blk_trace) == NULL)
 415                 return -EINVAL;
 416
 417         /*
 418          * For starting a trace, we can transition from a setup or stopped
 419          * trace. For stopping a trace, the state must be running
 420          */
 421         ret = -EINVAL;
 422         if (start) {
 423                 if (bt->trace_state == Blktrace_setup ||
 424                     bt->trace_state == Blktrace_stopped) {
 425                         blktrace_seq++;
 426                         smp_mb();
 427                         bt->trace_state = Blktrace_running;
 428
 429                         trace_note_time(bt);
 430                         ret = 0;
 431                 }
 432         } else {
 433                 if (bt->trace_state == Blktrace_running) {
 434                         bt->trace_state = Blktrace_stopped;
 435                         relay_flush(bt->rchan);
 436                         ret = 0;
 437                 }
 438         }
 439
 440         return ret;
 441 }
 442
 443 /**
 444  * blk_trace_ioctl: - handle the ioctls associated with tracing
 445  * @bdev:       the block device
 446  * @cmd:        the ioctl cmd
 447  * @arg:        the argument data, if any
 448  *
 449  **/
 450 int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
 451 {
 452         request_queue_t *q;
 453         int ret, start = 0;
 454
 455         q = bdev_get_queue(bdev);
 456         if (!q)
 457                 return -ENXIO;
 458
 459         mutex_lock(&bdev->bd_mutex);
 460
 461         switch (cmd) {
 462         case BLKTRACESETUP:
 463                 ret = blk_trace_setup(q, bdev, arg);
 464                 break;
 465         case BLKTRACESTART:
 466                 start = 1;
 467         case BLKTRACESTOP:
 468                 ret = blk_trace_startstop(q, start);
 469                 break;
 470         case BLKTRACETEARDOWN:
 471                 ret = blk_trace_remove(q);
 472                 break;
 473         default:
 474                 ret = -ENOTTY;
 475                 break;
 476         }
 477
 478         mutex_unlock(&bdev->bd_mutex);
 479         return ret;
 480 }
 481
 482 /**
 483  * blk_trace_shutdown: - stop and cleanup trace structures
 484  * @q:    the request queue associated with the device
 485  *
 486  **/
 487 void blk_trace_shutdown(request_queue_t *q)
 488 {
 489         if (q->blk_trace) {
 490                 blk_trace_startstop(q, 0);
 491                 blk_trace_remove(q);
 492         }
 493 }
 494
 495 /*
 496  * Average offset over two calls to sched_clock() with a gettimeofday()
 497  * in the middle
 498  */
 499 static void blk_check_time(unsigned long long *t)
 500 {
 501         unsigned long long a, b;
 502         struct timeval tv;
 503
 504         a = sched_clock();
 505         do_gettimeofday(&tv);
 506         b = sched_clock();
 507
 508         *t = tv.tv_sec * 1000000000 + tv.tv_usec * 1000;
 509         *t -= (a + b) / 2;
 510 }
 511
 512 /*
 513  * calibrate our inter-CPU timings
 514  */
 515 static void blk_trace_check_cpu_time(void *data)
 516 {
 517         unsigned long long *t;
 518         int cpu = get_cpu();
 519
 520         t = &per_cpu(blk_trace_cpu_offset, cpu);
 521
 522         /*
 523          * Just call it twice, hopefully the second call will be cache hot
 524          * and a little more precise
 525          */
 526         blk_check_time(t);
 527         blk_check_time(t);
 528
 529         put_cpu();
 530 }
 531
 532 static void blk_trace_set_ht_offsets(void)
 533 {
 534 #if defined(CONFIG_SCHED_SMT)
 535         int cpu, i;
 536
 537         /*
 538          * now make sure HT siblings have the same time offset
 539          */
 540         preempt_disable();
 541         for_each_online_cpu(cpu) {
 542                 unsigned long long *cpu_off, *sibling_off;
 543
 544                 for_each_cpu_mask(i, cpu_sibling_map[cpu]) {
 545                         if (i == cpu)
 546                                 continue;
 547
 548                         cpu_off = &per_cpu(blk_trace_cpu_offset, cpu);
 549                         sibling_off = &per_cpu(blk_trace_cpu_offset, i);
 550                         *sibling_off = *cpu_off;
 551                 }
 552         }
 553         preempt_enable();
 554 #endif
 555 }
 556
 557 static __init int blk_trace_init(void)
 558 {
 559         mutex_init(&blk_tree_mutex);
 560         on_each_cpu(blk_trace_check_cpu_time, NULL, 1, 1);
 561         blk_trace_set_ht_offsets();
 562
 563         return 0;
 564 }
 565
 566 module_init(blk_trace_init);
 567