linux/block/blktrace.c
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   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
  28static unsigned int blktrace_seq __read_mostly = 1;
  29
  30/*
  31 * Send out a notify message.
  32 */
  33static 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 */
  57static 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
  63static 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
  78void __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}
  94EXPORT_SYMBOL_GPL(__trace_note_message);
  95
  96static 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 */
 112static 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 */
 122void __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
 180EXPORT_SYMBOL_GPL(__blk_add_trace);
 181
 182static struct dentry *blk_tree_root;
 183static DEFINE_MUTEX(blk_tree_mutex);
 184static unsigned int root_users;
 185
 186static 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
 194static 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
 203static 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
 226err:
 227        mutex_unlock(&blk_tree_mutex);
 228        return dir;
 229}
 230
 231static 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
 242int 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}
 256EXPORT_SYMBOL_GPL(blk_trace_remove);
 257
 258static int blk_dropped_open(struct inode *inode, struct file *filp)
 259{
 260        filp->private_data = inode->i_private;
 261
 262        return 0;
 263}
 264
 265static 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
 276static const struct file_operations blk_dropped_fops = {
 277        .owner =        THIS_MODULE,
 278        .open =         blk_dropped_open,
 279        .read =         blk_dropped_read,
 280};
 281
 282static int blk_msg_open(struct inode *inode, struct file *filp)
 283{
 284        filp->private_data = inode->i_private;
 285
 286        return 0;
 287}
 288
 289static 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
 314static 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 */
 324static 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
 337static int blk_remove_buf_file_callback(struct dentry *dentry)
 338{
 339        debugfs_remove(dentry);
 340        return 0;
 341}
 342
 343static 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
 353static 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 */
 362int 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;
 439err:
 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
 456int 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}
 475EXPORT_SYMBOL_GPL(blk_trace_setup);
 476
 477int 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}
 510EXPORT_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 **/
 519int 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 **/
 558void 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}
 565
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