block/blktrace.c

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