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 static int act_log_check(struct blk_trace *bt, u32 what, sector_t sector,
79 pid_t pid)
80 {
81 if (((bt->act_mask << BLK_TC_SHIFT) & what) == 0)
82 return 1;
83 if (sector < bt->start_lba || sector > bt->end_lba)
84 return 1;
85 if (bt->pid && pid != bt->pid)
86 return 1;
87
88 return 0;
89 }
90
91 /*
92 * Data direction bit lookup
93 */
94 static u32 ddir_act[2] __read_mostly = { BLK_TC_ACT(BLK_TC_READ), BLK_TC_ACT(BLK_TC_WRITE) };
95
96 /*
97 * Bio action bits of interest
98 */
99 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) };
100
101 /*
102 * More could be added as needed, taking care to increment the decrementer
103 * to get correct indexing
104 */
105 #define trace_barrier_bit(rw) \
106 (((rw) & (1 << BIO_RW_BARRIER)) >> (BIO_RW_BARRIER - 0))
107 #define trace_sync_bit(rw) \
108 (((rw) & (1 << BIO_RW_SYNC)) >> (BIO_RW_SYNC - 1))
109 #define trace_ahead_bit(rw) \
110 (((rw) & (1 << BIO_RW_AHEAD)) << (2 - BIO_RW_AHEAD))
111 #define trace_meta_bit(rw) \
112 (((rw) & (1 << BIO_RW_META)) >> (BIO_RW_META - 3))
113
114 /*
115 * The worker for the various blk_add_trace*() types. Fills out a
116 * blk_io_trace structure and places it in a per-cpu subbuffer.
117 */
118 void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
119 int rw, u32 what, int error, int pdu_len, void *pdu_data)
120 {
121 struct task_struct *tsk = current;
122 struct blk_io_trace *t;
123 unsigned long flags;
124 unsigned long *sequence;
125 pid_t pid;
126 int cpu;
127
128 if (unlikely(bt->trace_state != Blktrace_running))
129 return;
130
131 what |= ddir_act[rw & WRITE];
132 what |= bio_act[trace_barrier_bit(rw)];
133 what |= bio_act[trace_sync_bit(rw)];
134 what |= bio_act[trace_ahead_bit(rw)];
135 what |= bio_act[trace_meta_bit(rw)];
136
137 pid = tsk->pid;
138 if (unlikely(act_log_check(bt, what, sector, pid)))
139 return;
140
141 /*
142 * A word about the locking here - we disable interrupts to reserve
143 * some space in the relay per-cpu buffer, to prevent an irq
144 * from coming in and stepping on our toes. Once reserved, it's
145 * enough to get preemption disabled to prevent read of this data
146 * before we are through filling it. get_cpu()/put_cpu() does this
147 * for us
148 */
149 local_irq_save(flags);
150
151 if (unlikely(tsk->btrace_seq != blktrace_seq))
152 trace_note_tsk(bt, tsk);
153
154 t = relay_reserve(bt->rchan, sizeof(*t) + pdu_len);
155 if (t) {
156 cpu = smp_processor_id();
157 sequence = per_cpu_ptr(bt->sequence, cpu);
158
159 t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
160 t->sequence = ++(*sequence);
161 t->time = ktime_to_ns(ktime_get());
162 t->sector = sector;
163 t->bytes = bytes;
164 t->action = what;
165 t->pid = pid;
166 t->device = bt->dev;
167 t->cpu = cpu;
168 t->error = error;
169 t->pdu_len = pdu_len;
170
171 if (pdu_len)
172 memcpy((void *) t + sizeof(*t), pdu_data, pdu_len);
173 }
174
175 local_irq_restore(flags);
176 }
177
178 EXPORT_SYMBOL_GPL(__blk_add_trace);
179
180 static struct dentry *blk_tree_root;
181 static DEFINE_MUTEX(blk_tree_mutex);
182 static unsigned int root_users;
183
184 static inline void blk_remove_root(void)
185 {
186 if (blk_tree_root) {
187 debugfs_remove(blk_tree_root);
188 blk_tree_root = NULL;
189 }
190 }
191
192 static void blk_remove_tree(struct dentry *dir)
193 {
194 mutex_lock(&blk_tree_mutex);
195 debugfs_remove(dir);
196 if (--root_users == 0)
197 blk_remove_root();
198 mutex_unlock(&blk_tree_mutex);
199 }
200
201 static struct dentry *blk_create_tree(const char *blk_name)
202 {
203 struct dentry *dir = NULL;
204 int created = 0;
205
206 mutex_lock(&blk_tree_mutex);
207
208 if (!blk_tree_root) {
209 blk_tree_root = debugfs_create_dir("block", NULL);
210 if (!blk_tree_root)
211 goto err;
212 created = 1;
213 }
214
215 dir = debugfs_create_dir(blk_name, blk_tree_root);
216 if (dir)
217 root_users++;
218 else {
219 /* Delete root only if we created it */
220 if (created)
221 blk_remove_root();
222 }
223
224 err:
225 mutex_unlock(&blk_tree_mutex);
226 return dir;
227 }
228
229 static void blk_trace_cleanup(struct blk_trace *bt)
230 {
231 relay_close(bt->rchan);
232 debugfs_remove(bt->dropped_file);
233 blk_remove_tree(bt->dir);
234 free_percpu(bt->sequence);
235 kfree(bt);
236 }
237
238 int blk_trace_remove(struct request_queue *q)
239 {
240 struct blk_trace *bt;
241
242 bt = xchg(&q->blk_trace, NULL);
243 if (!bt)
244 return -EINVAL;
245
246 if (bt->trace_state == Blktrace_setup ||
247 bt->trace_state == Blktrace_stopped)
248 blk_trace_cleanup(bt);
249
250 return 0;
251 }
252 EXPORT_SYMBOL_GPL(blk_trace_remove);
253
254 static int blk_dropped_open(struct inode *inode, struct file *filp)
255 {
256 filp->private_data = inode->i_private;
257
258 return 0;
259 }
260
261 static ssize_t blk_dropped_read(struct file *filp, char __user *buffer,
262 size_t count, loff_t *ppos)
263 {
264 struct blk_trace *bt = filp->private_data;
265 char buf[16];
266
267 snprintf(buf, sizeof(buf), "%u\n", atomic_read(&bt->dropped));
268
269 return simple_read_from_buffer(buffer, count, ppos, buf, strlen(buf));
270 }
271
272 static const struct file_operations blk_dropped_fops = {
273 .owner = THIS_MODULE,
274 .open = blk_dropped_open,
275 .read = blk_dropped_read,
276 };
277
278 /*
279 * Keep track of how many times we encountered a full subbuffer, to aid
280 * the user space app in telling how many lost events there were.
281 */
282 static int blk_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
283 void *prev_subbuf, size_t prev_padding)
284 {
285 struct blk_trace *bt;
286
287 if (!relay_buf_full(buf))
288 return 1;
289
290 bt = buf->chan->private_data;
291 atomic_inc(&bt->dropped);
292 return 0;
293 }
294
295 static int blk_remove_buf_file_callback(struct dentry *dentry)
296 {
297 debugfs_remove(dentry);
298 return 0;
299 }
300
301 static struct dentry *blk_create_buf_file_callback(const char *filename,
302 struct dentry *parent,
303 int mode,
304 struct rchan_buf *buf,
305 int *is_global)
306 {
307 return debugfs_create_file(filename, mode, parent, buf,
308 &relay_file_operations);
309 }
310
311 static struct rchan_callbacks blk_relay_callbacks = {
312 .subbuf_start = blk_subbuf_start_callback,
313 .create_buf_file = blk_create_buf_file_callback,
314 .remove_buf_file = blk_remove_buf_file_callback,
315 };
316
317 /*
318 * Setup everything required to start tracing
319 */
320 int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
321 struct blk_user_trace_setup *buts)
322 {
323 struct blk_trace *old_bt, *bt = NULL;
324 struct dentry *dir = NULL;
325 int ret, i;
326
327 if (!buts->buf_size || !buts->buf_nr)
328 return -EINVAL;
329
330 strcpy(buts->name, name);
331
332 /*
333 * some device names have larger paths - convert the slashes
334 * to underscores for this to work as expected
335 */
336 for (i = 0; i < strlen(buts->name); i++)
337 if (buts->name[i] == '/')
338 buts->name[i] = '_';
339
340 ret = -ENOMEM;
341 bt = kzalloc(sizeof(*bt), GFP_KERNEL);
342 if (!bt)
343 goto err;
344
345 bt->sequence = alloc_percpu(unsigned long);
346 if (!bt->sequence)
347 goto err;
348
349 ret = -ENOENT;
350 dir = blk_create_tree(buts->name);
351 if (!dir)
352 goto err;
353
354 bt->dir = dir;
355 bt->dev = dev;
356 atomic_set(&bt->dropped, 0);
357
358 ret = -EIO;
359 bt->dropped_file = debugfs_create_file("dropped", 0444, dir, bt, &blk_dropped_fops);
360 if (!bt->dropped_file)
361 goto err;
362
363 bt->rchan = relay_open("trace", dir, buts->buf_size,
364 buts->buf_nr, &blk_relay_callbacks, bt);
365 if (!bt->rchan)
366 goto err;
367
368 bt->act_mask = buts->act_mask;
369 if (!bt->act_mask)
370 bt->act_mask = (u16) -1;
371
372 bt->start_lba = buts->start_lba;
373 bt->end_lba = buts->end_lba;
374 if (!bt->end_lba)
375 bt->end_lba = -1ULL;
376
377 bt->pid = buts->pid;
378 bt->trace_state = Blktrace_setup;
379
380 ret = -EBUSY;
381 old_bt = xchg(&q->blk_trace, bt);
382 if (old_bt) {
383 (void) xchg(&q->blk_trace, old_bt);
384 goto err;
385 }
386
387 return 0;
388 err:
389 if (dir)
390 blk_remove_tree(dir);
391 if (bt) {
392 if (bt->dropped_file)
393 debugfs_remove(bt->dropped_file);
394 free_percpu(bt->sequence);
395 if (bt->rchan)
396 relay_close(bt->rchan);
397 kfree(bt);
398 }
399 return ret;
400 }
401
402 int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
403 char __user *arg)
404 {
405 struct blk_user_trace_setup buts;
406 int ret;
407
408 ret = copy_from_user(&buts, arg, sizeof(buts));
409 if (ret)
410 return -EFAULT;
411
412 ret = do_blk_trace_setup(q, name, dev, &buts);
413 if (ret)
414 return ret;
415
416 if (copy_to_user(arg, &buts, sizeof(buts)))
417 return -EFAULT;
418
419 return 0;
420 }
421 EXPORT_SYMBOL_GPL(blk_trace_setup);
422
423 int blk_trace_startstop(struct request_queue *q, int start)
424 {
425 struct blk_trace *bt;
426 int ret;
427
428 if ((bt = q->blk_trace) == NULL)
429 return -EINVAL;
430
431 /*
432 * For starting a trace, we can transition from a setup or stopped
433 * trace. For stopping a trace, the state must be running
434 */
435 ret = -EINVAL;
436 if (start) {
437 if (bt->trace_state == Blktrace_setup ||
438 bt->trace_state == Blktrace_stopped) {
439 blktrace_seq++;
440 smp_mb();
441 bt->trace_state = Blktrace_running;
442
443 trace_note_time(bt);
444 ret = 0;
445 }
446 } else {
447 if (bt->trace_state == Blktrace_running) {
448 bt->trace_state = Blktrace_stopped;
449 relay_flush(bt->rchan);
450 ret = 0;
451 }
452 }
453
454 return ret;
455 }
456 EXPORT_SYMBOL_GPL(blk_trace_startstop);
457
458 /**
459 * blk_trace_ioctl: - handle the ioctls associated with tracing
460 * @bdev: the block device
461 * @cmd: the ioctl cmd
462 * @arg: the argument data, if any
463 *
464 **/
465 int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
466 {
467 struct request_queue *q;
468 int ret, start = 0;
469 char b[BDEVNAME_SIZE];
470
471 q = bdev_get_queue(bdev);
472 if (!q)
473 return -ENXIO;
474
475 mutex_lock(&bdev->bd_mutex);
476
477 switch (cmd) {
478 case BLKTRACESETUP:
479 strcpy(b, bdevname(bdev, b));
480 ret = blk_trace_setup(q, b, bdev->bd_dev, arg);
481 break;
482 case BLKTRACESTART:
483 start = 1;
484 case BLKTRACESTOP:
485 ret = blk_trace_startstop(q, start);
486 break;
487 case BLKTRACETEARDOWN:
488 ret = blk_trace_remove(q);
489 break;
490 default:
491 ret = -ENOTTY;
492 break;
493 }
494
495 mutex_unlock(&bdev->bd_mutex);
496 return ret;
497 }
498
499 /**
500 * blk_trace_shutdown: - stop and cleanup trace structures
501 * @q: the request queue associated with the device
502 *
503 **/
504 void blk_trace_shutdown(struct request_queue *q)
505 {
506 if (q->blk_trace) {
507 blk_trace_startstop(q, 0);
508 blk_trace_remove(q);
509 }
510 }
511
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