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         strcpy(buts->name, name);
 373
 374         /*
 375          * some device names have larger paths - convert the slashes
 376          * to underscores for this to work as expected
 377          */
 378         for (i = 0; i < strlen(buts->name); i++)
 379                 if (buts->name[i] == '/')
 380                         buts->name[i] = '_';
 381
 382         ret = -ENOMEM;
 383         bt = kzalloc(sizeof(*bt), GFP_KERNEL);
 384         if (!bt)
 385                 goto err;
 386
 387         bt->sequence = alloc_percpu(unsigned long);
 388         if (!bt->sequence)
 389                 goto err;
 390
 391         bt->msg_data = __alloc_percpu(BLK_TN_MAX_MSG);
 392         if (!bt->msg_data)
 393                 goto err;
 394
 395         ret = -ENOENT;
 396         dir = blk_create_tree(buts->name);
 397         if (!dir)
 398                 goto err;
 399
 400         bt->dir = dir;
 401         bt->dev = dev;
 402         atomic_set(&bt->dropped, 0);
 403
 404         ret = -EIO;
 405         bt->dropped_file = debugfs_create_file("dropped", 0444, dir, bt, &blk_dropped_fops);
 406         if (!bt->dropped_file)
 407                 goto err;
 408
 409         bt->msg_file = debugfs_create_file("msg", 0222, dir, bt, &blk_msg_fops);
 410         if (!bt->msg_file)
 411                 goto err;
 412
 413         bt->rchan = relay_open("trace", dir, buts->buf_size,
 414                                 buts->buf_nr, &blk_relay_callbacks, bt);
 415         if (!bt->rchan)
 416                 goto err;
 417
 418         bt->act_mask = buts->act_mask;
 419         if (!bt->act_mask)
 420                 bt->act_mask = (u16) -1;
 421
 422         bt->start_lba = buts->start_lba;
 423         bt->end_lba = buts->end_lba;
 424         if (!bt->end_lba)
 425                 bt->end_lba = -1ULL;
 426
 427         bt->pid = buts->pid;
 428         bt->trace_state = Blktrace_setup;
 429
 430         ret = -EBUSY;
 431         old_bt = xchg(&q->blk_trace, bt);
 432         if (old_bt) {
 433                 (void) xchg(&q->blk_trace, old_bt);
 434                 goto err;
 435         }
 436
 437         return 0;
 438 err:
 439         if (dir)
 440                 blk_remove_tree(dir);
 441         if (bt) {
 442                 if (bt->msg_file)
 443                         debugfs_remove(bt->msg_file);
 444                 if (bt->dropped_file)
 445                         debugfs_remove(bt->dropped_file);
 446                 free_percpu(bt->sequence);
 447                 free_percpu(bt->msg_data);
 448                 if (bt->rchan)
 449                         relay_close(bt->rchan);
 450                 kfree(bt);
 451         }
 452         return ret;
 453 }
 454
 455 int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
 456                     char __user *arg)
 457 {
 458         struct blk_user_trace_setup buts;
 459         int ret;
 460
 461         ret = copy_from_user(&buts, arg, sizeof(buts));
 462         if (ret)
 463                 return -EFAULT;
 464
 465         ret = do_blk_trace_setup(q, name, dev, &buts);
 466         if (ret)
 467                 return ret;
 468
 469         if (copy_to_user(arg, &buts, sizeof(buts)))
 470                 return -EFAULT;
 471
 472         return 0;
 473 }
 474 EXPORT_SYMBOL_GPL(blk_trace_setup);
 475
 476 int blk_trace_startstop(struct request_queue *q, int start)
 477 {
 478         struct blk_trace *bt;
 479         int ret;
 480
 481         if ((bt = q->blk_trace) == NULL)
 482                 return -EINVAL;
 483
 484         /*
 485          * For starting a trace, we can transition from a setup or stopped
 486          * trace. For stopping a trace, the state must be running
 487          */
 488         ret = -EINVAL;
 489         if (start) {
 490                 if (bt->trace_state == Blktrace_setup ||
 491                     bt->trace_state == Blktrace_stopped) {
 492                         blktrace_seq++;
 493                         smp_mb();
 494                         bt->trace_state = Blktrace_running;
 495
 496                         trace_note_time(bt);
 497                         ret = 0;
 498                 }
 499         } else {
 500                 if (bt->trace_state == Blktrace_running) {
 501                         bt->trace_state = Blktrace_stopped;
 502                         relay_flush(bt->rchan);
 503                         ret = 0;
 504                 }
 505         }
 506
 507         return ret;
 508 }
 509 EXPORT_SYMBOL_GPL(blk_trace_startstop);
 510
 511 /**
 512  * blk_trace_ioctl: - handle the ioctls associated with tracing
 513  * @bdev:       the block device
 514  * @cmd:        the ioctl cmd
 515  * @arg:        the argument data, if any
 516  *
 517  **/
 518 int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
 519 {
 520         struct request_queue *q;
 521         int ret, start = 0;
 522         char b[BDEVNAME_SIZE];
 523
 524         q = bdev_get_queue(bdev);
 525         if (!q)
 526                 return -ENXIO;
 527
 528         mutex_lock(&bdev->bd_mutex);
 529
 530         switch (cmd) {
 531         case BLKTRACESETUP:
 532                 bdevname(bdev, b);
 533                 ret = blk_trace_setup(q, b, bdev->bd_dev, arg);
 534                 break;
 535         case BLKTRACESTART:
 536                 start = 1;
 537         case BLKTRACESTOP:
 538                 ret = blk_trace_startstop(q, start);
 539                 break;
 540         case BLKTRACETEARDOWN:
 541                 ret = blk_trace_remove(q);
 542                 break;
 543         default:
 544                 ret = -ENOTTY;
 545                 break;
 546         }
 547
 548         mutex_unlock(&bdev->bd_mutex);
 549         return ret;
 550 }
 551
 552 /**
 553  * blk_trace_shutdown: - stop and cleanup trace structures
 554  * @q:    the request queue associated with the device
 555  *
 556  **/
 557 void blk_trace_shutdown(struct request_queue *q)
 558 {
 559         if (q->blk_trace) {
 560                 blk_trace_startstop(q, 0);
 561                 blk_trace_remove(q);
 562         }
 563 }