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