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 
   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 }
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FreeBSD/Linux Kernel Cross Reference sys/block/blktrace.c

FreeBSD/Linux Kernel Cross Reference
sys/block/blktrace.c
