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 unsigned int blktrace_seq __read_mostly = 1;
  29
  30 /*
  31  * Send out a notify message.
  32  */
  33 static void trace_note(struct blk_trace *bt, pid_t pid, int action,
  34                        const void *data, size_t len)
  35 {
  36         struct blk_io_trace *t;
  37
  38         t = relay_reserve(bt->rchan, sizeof(*t) + len);
  39         if (t) {
  40                 const int cpu = smp_processor_id();
  41
  42                 t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
  43                 t->time = ktime_to_ns(ktime_get());
  44                 t->device = bt->dev;
  45                 t->action = action;
  46                 t->pid = pid;
  47                 t->cpu = cpu;
  48                 t->pdu_len = len;
  49                 memcpy((void *) t + sizeof(*t), data, len);
  50         }
  51 }
  52
  53 /*
  54  * Send out a notify for this process, if we haven't done so since a trace
  55  * started
  56  */
  57 static void trace_note_tsk(struct blk_trace *bt, struct task_struct *tsk)
  58 {
  59         tsk->btrace_seq = blktrace_seq;
  60         trace_note(bt, tsk->pid, BLK_TN_PROCESS, tsk->comm, sizeof(tsk->comm));
  61 }
  62
  63 static void trace_note_time(struct blk_trace *bt)
  64 {
  65         struct timespec now;
  66         unsigned long flags;
  67         u32 words[2];
  68
  69         getnstimeofday(&now);
  70         words[0] = now.tv_sec;
  71         words[1] = now.tv_nsec;
  72
  73         local_irq_save(flags);
  74         trace_note(bt, 0, BLK_TN_TIMESTAMP, words, sizeof(words));
  75         local_irq_restore(flags);
  76 }
  77
  78 void __trace_note_message(struct blk_trace *bt, const char *fmt, ...)
  79 {
  80         int n;
  81         va_list args;
  82         unsigned long flags;
  83         char *buf;
  84
  85         local_irq_save(flags);
  86         buf = per_cpu_ptr(bt->msg_data, smp_processor_id());
  87         va_start(args, fmt);
  88         n = vscnprintf(buf, BLK_TN_MAX_MSG, fmt, args);
  89         va_end(args);
  90
  91         trace_note(bt, 0, BLK_TN_MESSAGE, buf, n);
  92         local_irq_restore(flags);
  93 }
  94 EXPORT_SYMBOL_GPL(__trace_note_message);
  95
  96 static int act_log_check(struct blk_trace *bt, u32 what, sector_t sector,
  97                          pid_t pid)
  98 {
  99         if (((bt->act_mask << BLK_TC_SHIFT) & what) == 0)
 100                 return 1;
 101         if (sector < bt->start_lba || sector > bt->end_lba)
 102                 return 1;
 103         if (bt->pid && pid != bt->pid)
 104                 return 1;
 105
 106         return 0;
 107 }
 108
 109 /*
 110  * Data direction bit lookup
 111  */
 112 static u32 ddir_act[2] __read_mostly = { BLK_TC_ACT(BLK_TC_READ), BLK_TC_ACT(BLK_TC_WRITE) };
 113
 114 /* The ilog2() calls fall out because they're constant */
 115 #define MASK_TC_BIT(rw, __name) ( (rw & (1 << BIO_RW_ ## __name)) << \
 116           (ilog2(BLK_TC_ ## __name) + BLK_TC_SHIFT - BIO_RW_ ## __name) )
 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 |= MASK_TC_BIT(rw, BARRIER);
 137         what |= MASK_TC_BIT(rw, SYNC);
 138         what |= MASK_TC_BIT(rw, AHEAD);
 139         what |= MASK_TC_BIT(rw, META);
 140         what |= MASK_TC_BIT(rw, DISCARD);
 141
 142         pid = tsk->pid;
 143         if (unlikely(act_log_check(bt, what, sector, pid)))
 144                 return;
 145
 146         /*
 147          * A word about the locking here - we disable interrupts to reserve
 148          * some space in the relay per-cpu buffer, to prevent an irq
 149          * from coming in and stepping on our toes.
 150          */
 151         local_irq_save(flags);
 152
 153         if (unlikely(tsk->btrace_seq != blktrace_seq))
 154                 trace_note_tsk(bt, tsk);
 155
 156         t = relay_reserve(bt->rchan, sizeof(*t) + pdu_len);
 157         if (t) {
 158                 cpu = smp_processor_id();
 159                 sequence = per_cpu_ptr(bt->sequence, cpu);
 160
 161                 t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
 162                 t->sequence = ++(*sequence);
 163                 t->time = ktime_to_ns(ktime_get());
 164                 t->sector = sector;
 165                 t->bytes = bytes;
 166                 t->action = what;
 167                 t->pid = pid;
 168                 t->device = bt->dev;
 169                 t->cpu = cpu;
 170                 t->error = error;
 171                 t->pdu_len = pdu_len;
 172
 173                 if (pdu_len)
 174                         memcpy((void *) t + sizeof(*t), pdu_data, pdu_len);
 175         }
 176
 177         local_irq_restore(flags);
 178 }
 179
 180 EXPORT_SYMBOL_GPL(__blk_add_trace);
 181
 182 static struct dentry *blk_tree_root;
 183 static DEFINE_MUTEX(blk_tree_mutex);
 184 static unsigned int root_users;
 185
 186 static inline void blk_remove_root(void)
 187 {
 188         if (blk_tree_root) {
 189                 debugfs_remove(blk_tree_root);
 190                 blk_tree_root = NULL;
 191         }
 192 }
 193
 194 static void blk_remove_tree(struct dentry *dir)
 195 {
 196         mutex_lock(&blk_tree_mutex);
 197         debugfs_remove(dir);
 198         if (--root_users == 0)
 199                 blk_remove_root();
 200         mutex_unlock(&blk_tree_mutex);
 201 }
 202
 203 static struct dentry *blk_create_tree(const char *blk_name)
 204 {
 205         struct dentry *dir = NULL;
 206         int created = 0;
 207
 208         mutex_lock(&blk_tree_mutex);
 209
 210         if (!blk_tree_root) {
 211                 blk_tree_root = debugfs_create_dir("block", NULL);
 212                 if (!blk_tree_root)
 213                         goto err;
 214                 created = 1;
 215         }
 216
 217         dir = debugfs_create_dir(blk_name, blk_tree_root);
 218         if (dir)
 219                 root_users++;
 220         else {
 221                 /* Delete root only if we created it */
 222                 if (created)
 223                         blk_remove_root();
 224         }
 225
 226 err:
 227         mutex_unlock(&blk_tree_mutex);
 228         return dir;
 229 }
 230
 231 static void blk_trace_cleanup(struct blk_trace *bt)
 232 {
 233         relay_close(bt->rchan);
 234         debugfs_remove(bt->msg_file);
 235         debugfs_remove(bt->dropped_file);
 236         blk_remove_tree(bt->dir);
 237         free_percpu(bt->sequence);
 238         free_percpu(bt->msg_data);
 239         kfree(bt);
 240 }
 241
 242 int blk_trace_remove(struct request_queue *q)
 243 {
 244         struct blk_trace *bt;
 245
 246         bt = xchg(&q->blk_trace, NULL);
 247         if (!bt)
 248                 return -EINVAL;
 249
 250         if (bt->trace_state == Blktrace_setup ||
 251             bt->trace_state == Blktrace_stopped)
 252                 blk_trace_cleanup(bt);
 253
 254         return 0;
 255 }
 256 EXPORT_SYMBOL_GPL(blk_trace_remove);
 257
 258 static int blk_dropped_open(struct inode *inode, struct file *filp)
 259 {
 260         filp->private_data = inode->i_private;
 261
 262         return 0;
 263 }
 264
 265 static ssize_t blk_dropped_read(struct file *filp, char __user *buffer,
 266                                 size_t count, loff_t *ppos)
 267 {
 268         struct blk_trace *bt = filp->private_data;
 269         char buf[16];
 270
 271         snprintf(buf, sizeof(buf), "%u\n", atomic_read(&bt->dropped));
 272
 273         return simple_read_from_buffer(buffer, count, ppos, buf, strlen(buf));
 274 }
 275
 276 static const struct file_operations blk_dropped_fops = {
 277         .owner =        THIS_MODULE,
 278         .open =         blk_dropped_open,
 279         .read =         blk_dropped_read,
 280 };
 281
 282 static int blk_msg_open(struct inode *inode, struct file *filp)
 283 {
 284         filp->private_data = inode->i_private;
 285
 286         return 0;
 287 }
 288
 289 static ssize_t blk_msg_write(struct file *filp, const char __user *buffer,
 290                                 size_t count, loff_t *ppos)
 291 {
 292         char *msg;
 293         struct blk_trace *bt;
 294
 295         if (count > BLK_TN_MAX_MSG)
 296                 return -EINVAL;
 297
 298         msg = kmalloc(count, GFP_KERNEL);
 299         if (msg == NULL)
 300                 return -ENOMEM;
 301
 302         if (copy_from_user(msg, buffer, count)) {
 303                 kfree(msg);
 304                 return -EFAULT;
 305         }
 306
 307         bt = filp->private_data;
 308         __trace_note_message(bt, "%s", msg);
 309         kfree(msg);
 310
 311         return count;
 312 }
 313
 314 static const struct file_operations blk_msg_fops = {
 315         .owner =        THIS_MODULE,
 316         .open =         blk_msg_open,
 317         .write =        blk_msg_write,
 318 };
 319
 320 /*
 321  * Keep track of how many times we encountered a full subbuffer, to aid
 322  * the user space app in telling how many lost events there were.
 323  */
 324 static int blk_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
 325                                      void *prev_subbuf, size_t prev_padding)
 326 {
 327         struct blk_trace *bt;
 328
 329         if (!relay_buf_full(buf))
 330                 return 1;
 331
 332         bt = buf->chan->private_data;
 333         atomic_inc(&bt->dropped);
 334         return 0;
 335 }
 336
 337 static int blk_remove_buf_file_callback(struct dentry *dentry)
 338 {
 339         debugfs_remove(dentry);
 340         return 0;
 341 }
 342
 343 static struct dentry *blk_create_buf_file_callback(const char *filename,
 344                                                    struct dentry *parent,
 345                                                    int mode,
 346                                                    struct rchan_buf *buf,
 347                                                    int *is_global)
 348 {
 349         return debugfs_create_file(filename, mode, parent, buf,
 350                                         &relay_file_operations);
 351 }
 352
 353 static struct rchan_callbacks blk_relay_callbacks = {
 354         .subbuf_start           = blk_subbuf_start_callback,
 355         .create_buf_file        = blk_create_buf_file_callback,
 356         .remove_buf_file        = blk_remove_buf_file_callback,
 357 };
 358
 359 /*
 360  * Setup everything required to start tracing
 361  */
 362 int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
 363                         struct blk_user_trace_setup *buts)
 364 {
 365         struct blk_trace *old_bt, *bt = NULL;
 366         struct dentry *dir = NULL;
 367         int ret, i;
 368
 369         if (!buts->buf_size || !buts->buf_nr)
 370                 return -EINVAL;
 371
 372         strncpy(buts->name, name, BLKTRACE_BDEV_SIZE);
 373         buts->name[BLKTRACE_BDEV_SIZE - 1] = '\0';
 374
 375         /*
 376          * some device names have larger paths - convert the slashes
 377          * to underscores for this to work as expected
 378          */
 379         for (i = 0; i < strlen(buts->name); i++)
 380                 if (buts->name[i] == '/')
 381                         buts->name[i] = '_';
 382
 383         ret = -ENOMEM;
 384         bt = kzalloc(sizeof(*bt), GFP_KERNEL);
 385         if (!bt)
 386                 goto err;
 387
 388         bt->sequence = alloc_percpu(unsigned long);
 389         if (!bt->sequence)
 390                 goto err;
 391
 392         bt->msg_data = __alloc_percpu(BLK_TN_MAX_MSG);
 393         if (!bt->msg_data)
 394                 goto err;
 395
 396         ret = -ENOENT;
 397         dir = blk_create_tree(buts->name);
 398         if (!dir)
 399                 goto err;
 400
 401         bt->dir = dir;
 402         bt->dev = dev;
 403         atomic_set(&bt->dropped, 0);
 404
 405         ret = -EIO;
 406         bt->dropped_file = debugfs_create_file("dropped", 0444, dir, bt, &blk_dropped_fops);
 407         if (!bt->dropped_file)
 408                 goto err;
 409
 410         bt->msg_file = debugfs_create_file("msg", 0222, dir, bt, &blk_msg_fops);
 411         if (!bt->msg_file)
 412                 goto err;
 413
 414         bt->rchan = relay_open("trace", dir, buts->buf_size,
 415                                 buts->buf_nr, &blk_relay_callbacks, bt);
 416         if (!bt->rchan)
 417                 goto err;
 418
 419         bt->act_mask = buts->act_mask;
 420         if (!bt->act_mask)
 421                 bt->act_mask = (u16) -1;
 422
 423         bt->start_lba = buts->start_lba;
 424         bt->end_lba = buts->end_lba;
 425         if (!bt->end_lba)
 426                 bt->end_lba = -1ULL;
 427
 428         bt->pid = buts->pid;
 429         bt->trace_state = Blktrace_setup;
 430
 431         ret = -EBUSY;
 432         old_bt = xchg(&q->blk_trace, bt);
 433         if (old_bt) {
 434                 (void) xchg(&q->blk_trace, old_bt);
 435                 goto err;
 436         }
 437
 438         return 0;
 439 err:
 440         if (dir)
 441                 blk_remove_tree(dir);
 442         if (bt) {
 443                 if (bt->msg_file)
 444                         debugfs_remove(bt->msg_file);
 445                 if (bt->dropped_file)
 446                         debugfs_remove(bt->dropped_file);
 447                 free_percpu(bt->sequence);
 448                 free_percpu(bt->msg_data);
 449                 if (bt->rchan)
 450                         relay_close(bt->rchan);
 451                 kfree(bt);
 452         }
 453         return ret;
 454 }
 455
 456 int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
 457                     char __user *arg)
 458 {
 459         struct blk_user_trace_setup buts;
 460         int ret;
 461
 462         ret = copy_from_user(&buts, arg, sizeof(buts));
 463         if (ret)
 464                 return -EFAULT;
 465
 466         ret = do_blk_trace_setup(q, name, dev, &buts);
 467         if (ret)
 468                 return ret;
 469
 470         if (copy_to_user(arg, &buts, sizeof(buts)))
 471                 return -EFAULT;
 472
 473         return 0;
 474 }
 475 EXPORT_SYMBOL_GPL(blk_trace_setup);
 476
 477 int blk_trace_startstop(struct request_queue *q, int start)
 478 {
 479         struct blk_trace *bt;
 480         int ret;
 481
 482         if ((bt = q->blk_trace) == NULL)
 483                 return -EINVAL;
 484
 485         /*
 486          * For starting a trace, we can transition from a setup or stopped
 487          * trace. For stopping a trace, the state must be running
 488          */
 489         ret = -EINVAL;
 490         if (start) {
 491                 if (bt->trace_state == Blktrace_setup ||
 492                     bt->trace_state == Blktrace_stopped) {
 493                         blktrace_seq++;
 494                         smp_mb();
 495                         bt->trace_state = Blktrace_running;
 496
 497                         trace_note_time(bt);
 498                         ret = 0;
 499                 }
 500         } else {
 501                 if (bt->trace_state == Blktrace_running) {
 502                         bt->trace_state = Blktrace_stopped;
 503                         relay_flush(bt->rchan);
 504                         ret = 0;
 505                 }
 506         }
 507
 508         return ret;
 509 }
 510 EXPORT_SYMBOL_GPL(blk_trace_startstop);
 511
 512 /**
 513  * blk_trace_ioctl: - handle the ioctls associated with tracing
 514  * @bdev:       the block device
 515  * @cmd:        the ioctl cmd
 516  * @arg:        the argument data, if any
 517  *
 518  **/
 519 int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
 520 {
 521         struct request_queue *q;
 522         int ret, start = 0;
 523         char b[BDEVNAME_SIZE];
 524
 525         q = bdev_get_queue(bdev);
 526         if (!q)
 527                 return -ENXIO;
 528
 529         mutex_lock(&bdev->bd_mutex);
 530
 531         switch (cmd) {
 532         case BLKTRACESETUP:
 533                 bdevname(bdev, b);
 534                 ret = blk_trace_setup(q, b, bdev->bd_dev, arg);
 535                 break;
 536         case BLKTRACESTART:
 537                 start = 1;
 538         case BLKTRACESTOP:
 539                 ret = blk_trace_startstop(q, start);
 540                 break;
 541         case BLKTRACETEARDOWN:
 542                 ret = blk_trace_remove(q);
 543                 break;
 544         default:
 545                 ret = -ENOTTY;
 546                 break;
 547         }
 548
 549         mutex_unlock(&bdev->bd_mutex);
 550         return ret;
 551 }
 552
 553 /**
 554  * blk_trace_shutdown: - stop and cleanup trace structures
 555  * @q:    the request queue associated with the device
 556  *
 557  **/
 558 void blk_trace_shutdown(struct request_queue *q)
 559 {
 560         if (q->blk_trace) {
 561                 blk_trace_startstop(q, 0);
 562                 blk_trace_remove(q);
 563         }
 564 }