ocfs2: use simple_read_from_buffer()
[linux-2.6.git] / 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 /*
115  * Bio action bits of interest
116  */
117 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) };
118
119 /*
120  * More could be added as needed, taking care to increment the decrementer
121  * to get correct indexing
122  */
123 #define trace_barrier_bit(rw)   \
124         (((rw) & (1 << BIO_RW_BARRIER)) >> (BIO_RW_BARRIER - 0))
125 #define trace_sync_bit(rw)      \
126         (((rw) & (1 << BIO_RW_SYNC)) >> (BIO_RW_SYNC - 1))
127 #define trace_ahead_bit(rw)     \
128         (((rw) & (1 << BIO_RW_AHEAD)) << (2 - BIO_RW_AHEAD))
129 #define trace_meta_bit(rw)      \
130         (((rw) & (1 << BIO_RW_META)) >> (BIO_RW_META - 3))
131
132 /*
133  * The worker for the various blk_add_trace*() types. Fills out a
134  * blk_io_trace structure and places it in a per-cpu subbuffer.
135  */
136 void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
137                      int rw, u32 what, int error, int pdu_len, void *pdu_data)
138 {
139         struct task_struct *tsk = current;
140         struct blk_io_trace *t;
141         unsigned long flags;
142         unsigned long *sequence;
143         pid_t pid;
144         int cpu;
145
146         if (unlikely(bt->trace_state != Blktrace_running))
147                 return;
148
149         what |= ddir_act[rw & WRITE];
150         what |= bio_act[trace_barrier_bit(rw)];
151         what |= bio_act[trace_sync_bit(rw)];
152         what |= bio_act[trace_ahead_bit(rw)];
153         what |= bio_act[trace_meta_bit(rw)];
154
155         pid = tsk->pid;
156         if (unlikely(act_log_check(bt, what, sector, pid)))
157                 return;
158
159         /*
160          * A word about the locking here - we disable interrupts to reserve
161          * some space in the relay per-cpu buffer, to prevent an irq
162          * from coming in and stepping on our toes.
163          */
164         local_irq_save(flags);
165
166         if (unlikely(tsk->btrace_seq != blktrace_seq))
167                 trace_note_tsk(bt, tsk);
168
169         t = relay_reserve(bt->rchan, sizeof(*t) + pdu_len);
170         if (t) {
171                 cpu = smp_processor_id();
172                 sequence = per_cpu_ptr(bt->sequence, cpu);
173
174                 t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
175                 t->sequence = ++(*sequence);
176                 t->time = ktime_to_ns(ktime_get());
177                 t->sector = sector;
178                 t->bytes = bytes;
179                 t->action = what;
180                 t->pid = pid;
181                 t->device = bt->dev;
182                 t->cpu = cpu;
183                 t->error = error;
184                 t->pdu_len = pdu_len;
185
186                 if (pdu_len)
187                         memcpy((void *) t + sizeof(*t), pdu_data, pdu_len);
188         }
189
190         local_irq_restore(flags);
191 }
192
193 EXPORT_SYMBOL_GPL(__blk_add_trace);
194
195 static struct dentry *blk_tree_root;
196 static DEFINE_MUTEX(blk_tree_mutex);
197 static unsigned int root_users;
198
199 static inline void blk_remove_root(void)
200 {
201         if (blk_tree_root) {
202                 debugfs_remove(blk_tree_root);
203                 blk_tree_root = NULL;
204         }
205 }
206
207 static void blk_remove_tree(struct dentry *dir)
208 {
209         mutex_lock(&blk_tree_mutex);
210         debugfs_remove(dir);
211         if (--root_users == 0)
212                 blk_remove_root();
213         mutex_unlock(&blk_tree_mutex);
214 }
215
216 static struct dentry *blk_create_tree(const char *blk_name)
217 {
218         struct dentry *dir = NULL;
219         int created = 0;
220
221         mutex_lock(&blk_tree_mutex);
222
223         if (!blk_tree_root) {
224                 blk_tree_root = debugfs_create_dir("block", NULL);
225                 if (!blk_tree_root)
226                         goto err;
227                 created = 1;
228         }
229
230         dir = debugfs_create_dir(blk_name, blk_tree_root);
231         if (dir)
232                 root_users++;
233         else {
234                 /* Delete root only if we created it */
235                 if (created)
236                         blk_remove_root();
237         }
238
239 err:
240         mutex_unlock(&blk_tree_mutex);
241         return dir;
242 }
243
244 static void blk_trace_cleanup(struct blk_trace *bt)
245 {
246         relay_close(bt->rchan);
247         debugfs_remove(bt->dropped_file);
248         blk_remove_tree(bt->dir);
249         free_percpu(bt->sequence);
250         free_percpu(bt->msg_data);
251         kfree(bt);
252 }
253
254 int blk_trace_remove(struct request_queue *q)
255 {
256         struct blk_trace *bt;
257
258         bt = xchg(&q->blk_trace, NULL);
259         if (!bt)
260                 return -EINVAL;
261
262         if (bt->trace_state == Blktrace_setup ||
263             bt->trace_state == Blktrace_stopped)
264                 blk_trace_cleanup(bt);
265
266         return 0;
267 }
268 EXPORT_SYMBOL_GPL(blk_trace_remove);
269
270 static int blk_dropped_open(struct inode *inode, struct file *filp)
271 {
272         filp->private_data = inode->i_private;
273
274         return 0;
275 }
276
277 static ssize_t blk_dropped_read(struct file *filp, char __user *buffer,
278                                 size_t count, loff_t *ppos)
279 {
280         struct blk_trace *bt = filp->private_data;
281         char buf[16];
282
283         snprintf(buf, sizeof(buf), "%u\n", atomic_read(&bt->dropped));
284
285         return simple_read_from_buffer(buffer, count, ppos, buf, strlen(buf));
286 }
287
288 static const struct file_operations blk_dropped_fops = {
289         .owner =        THIS_MODULE,
290         .open =         blk_dropped_open,
291         .read =         blk_dropped_read,
292 };
293
294 /*
295  * Keep track of how many times we encountered a full subbuffer, to aid
296  * the user space app in telling how many lost events there were.
297  */
298 static int blk_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
299                                      void *prev_subbuf, size_t prev_padding)
300 {
301         struct blk_trace *bt;
302
303         if (!relay_buf_full(buf))
304                 return 1;
305
306         bt = buf->chan->private_data;
307         atomic_inc(&bt->dropped);
308         return 0;
309 }
310
311 static int blk_remove_buf_file_callback(struct dentry *dentry)
312 {
313         debugfs_remove(dentry);
314         return 0;
315 }
316
317 static struct dentry *blk_create_buf_file_callback(const char *filename,
318                                                    struct dentry *parent,
319                                                    int mode,
320                                                    struct rchan_buf *buf,
321                                                    int *is_global)
322 {
323         return debugfs_create_file(filename, mode, parent, buf,
324                                         &relay_file_operations);
325 }
326
327 static struct rchan_callbacks blk_relay_callbacks = {
328         .subbuf_start           = blk_subbuf_start_callback,
329         .create_buf_file        = blk_create_buf_file_callback,
330         .remove_buf_file        = blk_remove_buf_file_callback,
331 };
332
333 /*
334  * Setup everything required to start tracing
335  */
336 int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
337                         struct blk_user_trace_setup *buts)
338 {
339         struct blk_trace *old_bt, *bt = NULL;
340         struct dentry *dir = NULL;
341         int ret, i;
342
343         if (!buts->buf_size || !buts->buf_nr)
344                 return -EINVAL;
345
346         strcpy(buts->name, name);
347
348         /*
349          * some device names have larger paths - convert the slashes
350          * to underscores for this to work as expected
351          */
352         for (i = 0; i < strlen(buts->name); i++)
353                 if (buts->name[i] == '/')
354                         buts->name[i] = '_';
355
356         ret = -ENOMEM;
357         bt = kzalloc(sizeof(*bt), GFP_KERNEL);
358         if (!bt)
359                 goto err;
360
361         bt->sequence = alloc_percpu(unsigned long);
362         if (!bt->sequence)
363                 goto err;
364
365         bt->msg_data = __alloc_percpu(BLK_TN_MAX_MSG);
366         if (!bt->msg_data)
367                 goto err;
368
369         ret = -ENOENT;
370         dir = blk_create_tree(buts->name);
371         if (!dir)
372                 goto err;
373
374         bt->dir = dir;
375         bt->dev = dev;
376         atomic_set(&bt->dropped, 0);
377
378         ret = -EIO;
379         bt->dropped_file = debugfs_create_file("dropped", 0444, dir, bt, &blk_dropped_fops);
380         if (!bt->dropped_file)
381                 goto err;
382
383         bt->rchan = relay_open("trace", dir, buts->buf_size,
384                                 buts->buf_nr, &blk_relay_callbacks, bt);
385         if (!bt->rchan)
386                 goto err;
387
388         bt->act_mask = buts->act_mask;
389         if (!bt->act_mask)
390                 bt->act_mask = (u16) -1;
391
392         bt->start_lba = buts->start_lba;
393         bt->end_lba = buts->end_lba;
394         if (!bt->end_lba)
395                 bt->end_lba = -1ULL;
396
397         bt->pid = buts->pid;
398         bt->trace_state = Blktrace_setup;
399
400         ret = -EBUSY;
401         old_bt = xchg(&q->blk_trace, bt);
402         if (old_bt) {
403                 (void) xchg(&q->blk_trace, old_bt);
404                 goto err;
405         }
406
407         return 0;
408 err:
409         if (dir)
410                 blk_remove_tree(dir);
411         if (bt) {
412                 if (bt->dropped_file)
413                         debugfs_remove(bt->dropped_file);
414                 free_percpu(bt->sequence);
415                 free_percpu(bt->msg_data);
416                 if (bt->rchan)
417                         relay_close(bt->rchan);
418                 kfree(bt);
419         }
420         return ret;
421 }
422
423 int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
424                     char __user *arg)
425 {
426         struct blk_user_trace_setup buts;
427         int ret;
428
429         ret = copy_from_user(&buts, arg, sizeof(buts));
430         if (ret)
431                 return -EFAULT;
432
433         ret = do_blk_trace_setup(q, name, dev, &buts);
434         if (ret)
435                 return ret;
436
437         if (copy_to_user(arg, &buts, sizeof(buts)))
438                 return -EFAULT;
439
440         return 0;
441 }
442 EXPORT_SYMBOL_GPL(blk_trace_setup);
443
444 int blk_trace_startstop(struct request_queue *q, int start)
445 {
446         struct blk_trace *bt;
447         int ret;
448
449         if ((bt = q->blk_trace) == NULL)
450                 return -EINVAL;
451
452         /*
453          * For starting a trace, we can transition from a setup or stopped
454          * trace. For stopping a trace, the state must be running
455          */
456         ret = -EINVAL;
457         if (start) {
458                 if (bt->trace_state == Blktrace_setup ||
459                     bt->trace_state == Blktrace_stopped) {
460                         blktrace_seq++;
461                         smp_mb();
462                         bt->trace_state = Blktrace_running;
463
464                         trace_note_time(bt);
465                         ret = 0;
466                 }
467         } else {
468                 if (bt->trace_state == Blktrace_running) {
469                         bt->trace_state = Blktrace_stopped;
470                         relay_flush(bt->rchan);
471                         ret = 0;
472                 }
473         }
474
475         return ret;
476 }
477 EXPORT_SYMBOL_GPL(blk_trace_startstop);
478
479 /**
480  * blk_trace_ioctl: - handle the ioctls associated with tracing
481  * @bdev:       the block device
482  * @cmd:        the ioctl cmd
483  * @arg:        the argument data, if any
484  *
485  **/
486 int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
487 {
488         struct request_queue *q;
489         int ret, start = 0;
490         char b[BDEVNAME_SIZE];
491
492         q = bdev_get_queue(bdev);
493         if (!q)
494                 return -ENXIO;
495
496         mutex_lock(&bdev->bd_mutex);
497
498         switch (cmd) {
499         case BLKTRACESETUP:
500                 bdevname(bdev, b);
501                 ret = blk_trace_setup(q, b, bdev->bd_dev, arg);
502                 break;
503         case BLKTRACESTART:
504                 start = 1;
505         case BLKTRACESTOP:
506                 ret = blk_trace_startstop(q, start);
507                 break;
508         case BLKTRACETEARDOWN:
509                 ret = blk_trace_remove(q);
510                 break;
511         default:
512                 ret = -ENOTTY;
513                 break;
514         }
515
516         mutex_unlock(&bdev->bd_mutex);
517         return ret;
518 }
519
520 /**
521  * blk_trace_shutdown: - stop and cleanup trace structures
522  * @q:    the request queue associated with the device
523  *
524  **/
525 void blk_trace_shutdown(struct request_queue *q)
526 {
527         if (q->blk_trace) {
528                 blk_trace_startstop(q, 0);
529                 blk_trace_remove(q);
530         }
531 }