Chinese: add translation of oops-tracing.txt
[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 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 static 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
253 static int blk_dropped_open(struct inode *inode, struct file *filp)
254 {
255         filp->private_data = inode->i_private;
256
257         return 0;
258 }
259
260 static ssize_t blk_dropped_read(struct file *filp, char __user *buffer,
261                                 size_t count, loff_t *ppos)
262 {
263         struct blk_trace *bt = filp->private_data;
264         char buf[16];
265
266         snprintf(buf, sizeof(buf), "%u\n", atomic_read(&bt->dropped));
267
268         return simple_read_from_buffer(buffer, count, ppos, buf, strlen(buf));
269 }
270
271 static const struct file_operations blk_dropped_fops = {
272         .owner =        THIS_MODULE,
273         .open =         blk_dropped_open,
274         .read =         blk_dropped_read,
275 };
276
277 /*
278  * Keep track of how many times we encountered a full subbuffer, to aid
279  * the user space app in telling how many lost events there were.
280  */
281 static int blk_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
282                                      void *prev_subbuf, size_t prev_padding)
283 {
284         struct blk_trace *bt;
285
286         if (!relay_buf_full(buf))
287                 return 1;
288
289         bt = buf->chan->private_data;
290         atomic_inc(&bt->dropped);
291         return 0;
292 }
293
294 static int blk_remove_buf_file_callback(struct dentry *dentry)
295 {
296         debugfs_remove(dentry);
297         return 0;
298 }
299
300 static struct dentry *blk_create_buf_file_callback(const char *filename,
301                                                    struct dentry *parent,
302                                                    int mode,
303                                                    struct rchan_buf *buf,
304                                                    int *is_global)
305 {
306         return debugfs_create_file(filename, mode, parent, buf,
307                                         &relay_file_operations);
308 }
309
310 static struct rchan_callbacks blk_relay_callbacks = {
311         .subbuf_start           = blk_subbuf_start_callback,
312         .create_buf_file        = blk_create_buf_file_callback,
313         .remove_buf_file        = blk_remove_buf_file_callback,
314 };
315
316 /*
317  * Setup everything required to start tracing
318  */
319 int do_blk_trace_setup(struct request_queue *q, struct block_device *bdev,
320                         struct blk_user_trace_setup *buts)
321 {
322         struct blk_trace *old_bt, *bt = NULL;
323         struct dentry *dir = NULL;
324         char b[BDEVNAME_SIZE];
325         int ret, i;
326
327         if (!buts->buf_size || !buts->buf_nr)
328                 return -EINVAL;
329
330         strcpy(buts->name, bdevname(bdev, b));
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 = bdev->bd_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 static int blk_trace_setup(struct request_queue *q, struct block_device *bdev,
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, bdev, &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
422 static int blk_trace_startstop(struct request_queue *q, int start)
423 {
424         struct blk_trace *bt;
425         int ret;
426
427         if ((bt = q->blk_trace) == NULL)
428                 return -EINVAL;
429
430         /*
431          * For starting a trace, we can transition from a setup or stopped
432          * trace. For stopping a trace, the state must be running
433          */
434         ret = -EINVAL;
435         if (start) {
436                 if (bt->trace_state == Blktrace_setup ||
437                     bt->trace_state == Blktrace_stopped) {
438                         blktrace_seq++;
439                         smp_mb();
440                         bt->trace_state = Blktrace_running;
441
442                         trace_note_time(bt);
443                         ret = 0;
444                 }
445         } else {
446                 if (bt->trace_state == Blktrace_running) {
447                         bt->trace_state = Blktrace_stopped;
448                         relay_flush(bt->rchan);
449                         ret = 0;
450                 }
451         }
452
453         return ret;
454 }
455
456 /**
457  * blk_trace_ioctl: - handle the ioctls associated with tracing
458  * @bdev:       the block device
459  * @cmd:        the ioctl cmd
460  * @arg:        the argument data, if any
461  *
462  **/
463 int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
464 {
465         struct request_queue *q;
466         int ret, start = 0;
467
468         q = bdev_get_queue(bdev);
469         if (!q)
470                 return -ENXIO;
471
472         mutex_lock(&bdev->bd_mutex);
473
474         switch (cmd) {
475         case BLKTRACESETUP:
476                 ret = blk_trace_setup(q, bdev, arg);
477                 break;
478         case BLKTRACESTART:
479                 start = 1;
480         case BLKTRACESTOP:
481                 ret = blk_trace_startstop(q, start);
482                 break;
483         case BLKTRACETEARDOWN:
484                 ret = blk_trace_remove(q);
485                 break;
486         default:
487                 ret = -ENOTTY;
488                 break;
489         }
490
491         mutex_unlock(&bdev->bd_mutex);
492         return ret;
493 }
494
495 /**
496  * blk_trace_shutdown: - stop and cleanup trace structures
497  * @q:    the request queue associated with the device
498  *
499  **/
500 void blk_trace_shutdown(struct request_queue *q)
501 {
502         if (q->blk_trace) {
503                 blk_trace_startstop(q, 0);
504                 blk_trace_remove(q);
505         }
506 }