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