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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2011 Red Hat, Inc.
4 *
5 * This file is released under the GPL.
6 */
7#include "dm-block-manager.h"
8#include "dm-persistent-data-internal.h"
9
10#include <linux/dm-bufio.h>
11#include <linux/crc32c.h>
12#include <linux/module.h>
13#include <linux/slab.h>
14#include <linux/rwsem.h>
15#include <linux/device-mapper.h>
16#include <linux/stacktrace.h>
17#include <linux/sched/task.h>
18
19#define DM_MSG_PREFIX "block manager"
20
21/*----------------------------------------------------------------*/
22
23#ifdef CONFIG_DM_DEBUG_BLOCK_MANAGER_LOCKING
24
25/*
26 * This is a read/write semaphore with a couple of differences.
27 *
28 * i) There is a restriction on the number of concurrent read locks that
29 * may be held at once. This is just an implementation detail.
30 *
31 * ii) Recursive locking attempts are detected and return EINVAL. A stack
32 * trace is also emitted for the previous lock acquisition.
33 *
34 * iii) Priority is given to write locks.
35 */
36#define MAX_HOLDERS 4
37#define MAX_STACK 10
38
39struct stack_store {
40 unsigned int nr_entries;
41 unsigned long entries[MAX_STACK];
42};
43
44struct block_lock {
45 spinlock_t lock;
46 __s32 count;
47 struct list_head waiters;
48 struct task_struct *holders[MAX_HOLDERS];
49
50#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
51 struct stack_store traces[MAX_HOLDERS];
52#endif
53};
54
55struct waiter {
56 struct list_head list;
57 struct task_struct *task;
58 int wants_write;
59};
60
61static unsigned int __find_holder(struct block_lock *lock,
62 struct task_struct *task)
63{
64 unsigned int i;
65
66 for (i = 0; i < MAX_HOLDERS; i++)
67 if (lock->holders[i] == task)
68 break;
69
70 BUG_ON(i == MAX_HOLDERS);
71 return i;
72}
73
74/* call this *after* you increment lock->count */
75static void __add_holder(struct block_lock *lock, struct task_struct *task)
76{
77 unsigned int h = __find_holder(lock, NULL);
78#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
79 struct stack_store *t;
80#endif
81
82 get_task_struct(task);
83 lock->holders[h] = task;
84
85#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
86 t = lock->traces + h;
87 t->nr_entries = stack_trace_save(t->entries, MAX_STACK, 2);
88#endif
89}
90
91/* call this *before* you decrement lock->count */
92static void __del_holder(struct block_lock *lock, struct task_struct *task)
93{
94 unsigned int h = __find_holder(lock, task);
95
96 lock->holders[h] = NULL;
97 put_task_struct(task);
98}
99
100static int __check_holder(struct block_lock *lock)
101{
102 unsigned int i;
103
104 for (i = 0; i < MAX_HOLDERS; i++) {
105 if (lock->holders[i] == current) {
106 DMERR("recursive lock detected in metadata");
107#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
108 DMERR("previously held here:");
109 stack_trace_print(lock->traces[i].entries,
110 lock->traces[i].nr_entries, 4);
111
112 DMERR("subsequent acquisition attempted here:");
113 dump_stack();
114#endif
115 return -EINVAL;
116 }
117 }
118
119 return 0;
120}
121
122static void __wait(struct waiter *w)
123{
124 for (;;) {
125 set_current_state(TASK_UNINTERRUPTIBLE);
126
127 if (!w->task)
128 break;
129
130 schedule();
131 }
132
133 set_current_state(TASK_RUNNING);
134}
135
136static void __wake_waiter(struct waiter *w)
137{
138 struct task_struct *task;
139
140 list_del(&w->list);
141 task = w->task;
142 smp_mb();
143 w->task = NULL;
144 wake_up_process(task);
145}
146
147/*
148 * We either wake a few readers or a single writer.
149 */
150static void __wake_many(struct block_lock *lock)
151{
152 struct waiter *w, *tmp;
153
154 BUG_ON(lock->count < 0);
155 list_for_each_entry_safe(w, tmp, &lock->waiters, list) {
156 if (lock->count >= MAX_HOLDERS)
157 return;
158
159 if (w->wants_write) {
160 if (lock->count > 0)
161 return; /* still read locked */
162
163 lock->count = -1;
164 __add_holder(lock, w->task);
165 __wake_waiter(w);
166 return;
167 }
168
169 lock->count++;
170 __add_holder(lock, w->task);
171 __wake_waiter(w);
172 }
173}
174
175static void bl_init(struct block_lock *lock)
176{
177 int i;
178
179 spin_lock_init(&lock->lock);
180 lock->count = 0;
181 INIT_LIST_HEAD(&lock->waiters);
182 for (i = 0; i < MAX_HOLDERS; i++)
183 lock->holders[i] = NULL;
184}
185
186static int __available_for_read(struct block_lock *lock)
187{
188 return lock->count >= 0 &&
189 lock->count < MAX_HOLDERS &&
190 list_empty(&lock->waiters);
191}
192
193static int bl_down_read(struct block_lock *lock)
194{
195 int r;
196 struct waiter w;
197
198 spin_lock(&lock->lock);
199 r = __check_holder(lock);
200 if (r) {
201 spin_unlock(&lock->lock);
202 return r;
203 }
204
205 if (__available_for_read(lock)) {
206 lock->count++;
207 __add_holder(lock, current);
208 spin_unlock(&lock->lock);
209 return 0;
210 }
211
212 get_task_struct(current);
213
214 w.task = current;
215 w.wants_write = 0;
216 list_add_tail(&w.list, &lock->waiters);
217 spin_unlock(&lock->lock);
218
219 __wait(&w);
220 put_task_struct(current);
221 return 0;
222}
223
224static int bl_down_read_nonblock(struct block_lock *lock)
225{
226 int r;
227
228 spin_lock(&lock->lock);
229 r = __check_holder(lock);
230 if (r)
231 goto out;
232
233 if (__available_for_read(lock)) {
234 lock->count++;
235 __add_holder(lock, current);
236 r = 0;
237 } else
238 r = -EWOULDBLOCK;
239
240out:
241 spin_unlock(&lock->lock);
242 return r;
243}
244
245static void bl_up_read(struct block_lock *lock)
246{
247 spin_lock(&lock->lock);
248 BUG_ON(lock->count <= 0);
249 __del_holder(lock, current);
250 --lock->count;
251 if (!list_empty(&lock->waiters))
252 __wake_many(lock);
253 spin_unlock(&lock->lock);
254}
255
256static int bl_down_write(struct block_lock *lock)
257{
258 int r;
259 struct waiter w;
260
261 spin_lock(&lock->lock);
262 r = __check_holder(lock);
263 if (r) {
264 spin_unlock(&lock->lock);
265 return r;
266 }
267
268 if (lock->count == 0 && list_empty(&lock->waiters)) {
269 lock->count = -1;
270 __add_holder(lock, current);
271 spin_unlock(&lock->lock);
272 return 0;
273 }
274
275 get_task_struct(current);
276 w.task = current;
277 w.wants_write = 1;
278
279 /*
280 * Writers given priority. We know there's only one mutator in the
281 * system, so ignoring the ordering reversal.
282 */
283 list_add(&w.list, &lock->waiters);
284 spin_unlock(&lock->lock);
285
286 __wait(&w);
287 put_task_struct(current);
288
289 return 0;
290}
291
292static void bl_up_write(struct block_lock *lock)
293{
294 spin_lock(&lock->lock);
295 __del_holder(lock, current);
296 lock->count = 0;
297 if (!list_empty(&lock->waiters))
298 __wake_many(lock);
299 spin_unlock(&lock->lock);
300}
301
302static void report_recursive_bug(dm_block_t b, int r)
303{
304 if (r == -EINVAL)
305 DMERR("recursive acquisition of block %llu requested.",
306 (unsigned long long) b);
307}
308
309#else /* !CONFIG_DM_DEBUG_BLOCK_MANAGER_LOCKING */
310
311#define bl_init(x) do { } while (0)
312#define bl_down_read(x) 0
313#define bl_down_read_nonblock(x) 0
314#define bl_up_read(x) do { } while (0)
315#define bl_down_write(x) 0
316#define bl_up_write(x) do { } while (0)
317#define report_recursive_bug(x, y) do { } while (0)
318
319#endif /* CONFIG_DM_DEBUG_BLOCK_MANAGER_LOCKING */
320
321/*----------------------------------------------------------------*/
322
323/*
324 * Block manager is currently implemented using dm-bufio. struct
325 * dm_block_manager and struct dm_block map directly onto a couple of
326 * structs in the bufio interface. I want to retain the freedom to move
327 * away from bufio in the future. So these structs are just cast within
328 * this .c file, rather than making it through to the public interface.
329 */
330static struct dm_buffer *to_buffer(struct dm_block *b)
331{
332 return (struct dm_buffer *) b;
333}
334
335dm_block_t dm_block_location(struct dm_block *b)
336{
337 return dm_bufio_get_block_number(to_buffer(b));
338}
339EXPORT_SYMBOL_GPL(dm_block_location);
340
341void *dm_block_data(struct dm_block *b)
342{
343 return dm_bufio_get_block_data(to_buffer(b));
344}
345EXPORT_SYMBOL_GPL(dm_block_data);
346
347struct buffer_aux {
348 const struct dm_block_validator *validator;
349 int write_locked;
350
351#ifdef CONFIG_DM_DEBUG_BLOCK_MANAGER_LOCKING
352 struct block_lock lock;
353#endif
354};
355
356static void dm_block_manager_alloc_callback(struct dm_buffer *buf)
357{
358 struct buffer_aux *aux = dm_bufio_get_aux_data(buf);
359
360 aux->validator = NULL;
361 bl_init(&aux->lock);
362}
363
364static void dm_block_manager_write_callback(struct dm_buffer *buf)
365{
366 struct buffer_aux *aux = dm_bufio_get_aux_data(buf);
367
368 if (aux->validator) {
369 aux->validator->prepare_for_write(aux->validator, (struct dm_block *) buf,
370 dm_bufio_get_block_size(dm_bufio_get_client(buf)));
371 }
372}
373
374/*
375 * -------------------------------------------------------------
376 * Public interface
377 *--------------------------------------------------------------
378 */
379struct dm_block_manager {
380 struct dm_bufio_client *bufio;
381 bool read_only:1;
382};
383
384struct dm_block_manager *dm_block_manager_create(struct block_device *bdev,
385 unsigned int block_size,
386 unsigned int max_held_per_thread)
387{
388 int r;
389 struct dm_block_manager *bm;
390
391 bm = kmalloc_obj(*bm);
392 if (!bm) {
393 r = -ENOMEM;
394 goto bad;
395 }
396
397 bm->bufio = dm_bufio_client_create(bdev, block_size, max_held_per_thread,
398 sizeof(struct buffer_aux),
399 dm_block_manager_alloc_callback,
400 dm_block_manager_write_callback,
401 0);
402 if (IS_ERR(bm->bufio)) {
403 r = PTR_ERR(bm->bufio);
404 kfree(bm);
405 goto bad;
406 }
407
408 bm->read_only = false;
409
410 return bm;
411
412bad:
413 return ERR_PTR(r);
414}
415EXPORT_SYMBOL_GPL(dm_block_manager_create);
416
417void dm_block_manager_destroy(struct dm_block_manager *bm)
418{
419 dm_bufio_client_destroy(bm->bufio);
420 kfree(bm);
421}
422EXPORT_SYMBOL_GPL(dm_block_manager_destroy);
423
424void dm_block_manager_reset(struct dm_block_manager *bm)
425{
426 dm_bufio_client_reset(bm->bufio);
427}
428EXPORT_SYMBOL_GPL(dm_block_manager_reset);
429
430unsigned int dm_bm_block_size(struct dm_block_manager *bm)
431{
432 return dm_bufio_get_block_size(bm->bufio);
433}
434EXPORT_SYMBOL_GPL(dm_bm_block_size);
435
436dm_block_t dm_bm_nr_blocks(struct dm_block_manager *bm)
437{
438 return dm_bufio_get_device_size(bm->bufio);
439}
440
441static int dm_bm_validate_buffer(struct dm_block_manager *bm,
442 struct dm_buffer *buf,
443 struct buffer_aux *aux,
444 const struct dm_block_validator *v)
445{
446 if (unlikely(!aux->validator)) {
447 int r;
448
449 if (!v)
450 return 0;
451 r = v->check(v, (struct dm_block *) buf, dm_bufio_get_block_size(bm->bufio));
452 if (unlikely(r)) {
453 DMERR_LIMIT("%s validator check failed for block %llu", v->name,
454 (unsigned long long) dm_bufio_get_block_number(buf));
455 return r;
456 }
457 aux->validator = v;
458 } else {
459 if (unlikely(aux->validator != v)) {
460 DMERR_LIMIT("validator mismatch (old=%s vs new=%s) for block %llu",
461 aux->validator->name, v ? v->name : "NULL",
462 (unsigned long long) dm_bufio_get_block_number(buf));
463 return -EINVAL;
464 }
465 }
466
467 return 0;
468}
469int dm_bm_read_lock(struct dm_block_manager *bm, dm_block_t b,
470 const struct dm_block_validator *v,
471 struct dm_block **result)
472{
473 struct buffer_aux *aux;
474 void *p;
475 int r;
476
477 p = dm_bufio_read(bm->bufio, b, (struct dm_buffer **) result);
478 if (IS_ERR(p))
479 return PTR_ERR(p);
480
481 aux = dm_bufio_get_aux_data(to_buffer(*result));
482 r = bl_down_read(&aux->lock);
483 if (unlikely(r)) {
484 dm_bufio_release(to_buffer(*result));
485 report_recursive_bug(b, r);
486 return r;
487 }
488
489 aux->write_locked = 0;
490
491 r = dm_bm_validate_buffer(bm, to_buffer(*result), aux, v);
492 if (unlikely(r)) {
493 bl_up_read(&aux->lock);
494 dm_bufio_release(to_buffer(*result));
495 return r;
496 }
497
498 return 0;
499}
500EXPORT_SYMBOL_GPL(dm_bm_read_lock);
501
502int dm_bm_write_lock(struct dm_block_manager *bm,
503 dm_block_t b, const struct dm_block_validator *v,
504 struct dm_block **result)
505{
506 struct buffer_aux *aux;
507 void *p;
508 int r;
509
510 if (dm_bm_is_read_only(bm))
511 return -EPERM;
512
513 p = dm_bufio_read(bm->bufio, b, (struct dm_buffer **) result);
514 if (IS_ERR(p))
515 return PTR_ERR(p);
516
517 aux = dm_bufio_get_aux_data(to_buffer(*result));
518 r = bl_down_write(&aux->lock);
519 if (r) {
520 dm_bufio_release(to_buffer(*result));
521 report_recursive_bug(b, r);
522 return r;
523 }
524
525 aux->write_locked = 1;
526
527 r = dm_bm_validate_buffer(bm, to_buffer(*result), aux, v);
528 if (unlikely(r)) {
529 bl_up_write(&aux->lock);
530 dm_bufio_release(to_buffer(*result));
531 return r;
532 }
533
534 return 0;
535}
536EXPORT_SYMBOL_GPL(dm_bm_write_lock);
537
538int dm_bm_read_try_lock(struct dm_block_manager *bm,
539 dm_block_t b, const struct dm_block_validator *v,
540 struct dm_block **result)
541{
542 struct buffer_aux *aux;
543 void *p;
544 int r;
545
546 p = dm_bufio_get(bm->bufio, b, (struct dm_buffer **) result);
547 if (IS_ERR(p))
548 return PTR_ERR(p);
549 if (unlikely(!p))
550 return -EWOULDBLOCK;
551
552 aux = dm_bufio_get_aux_data(to_buffer(*result));
553 r = bl_down_read_nonblock(&aux->lock);
554 if (r < 0) {
555 dm_bufio_release(to_buffer(*result));
556 report_recursive_bug(b, r);
557 return r;
558 }
559 aux->write_locked = 0;
560
561 r = dm_bm_validate_buffer(bm, to_buffer(*result), aux, v);
562 if (unlikely(r)) {
563 bl_up_read(&aux->lock);
564 dm_bufio_release(to_buffer(*result));
565 return r;
566 }
567
568 return 0;
569}
570
571int dm_bm_write_lock_zero(struct dm_block_manager *bm,
572 dm_block_t b, const struct dm_block_validator *v,
573 struct dm_block **result)
574{
575 int r;
576 struct buffer_aux *aux;
577 void *p;
578
579 if (dm_bm_is_read_only(bm))
580 return -EPERM;
581
582 p = dm_bufio_new(bm->bufio, b, (struct dm_buffer **) result);
583 if (IS_ERR(p))
584 return PTR_ERR(p);
585
586 memset(p, 0, dm_bm_block_size(bm));
587
588 aux = dm_bufio_get_aux_data(to_buffer(*result));
589 r = bl_down_write(&aux->lock);
590 if (r) {
591 dm_bufio_release(to_buffer(*result));
592 return r;
593 }
594
595 aux->write_locked = 1;
596 aux->validator = v;
597
598 return 0;
599}
600EXPORT_SYMBOL_GPL(dm_bm_write_lock_zero);
601
602void dm_bm_unlock(struct dm_block *b)
603{
604 struct buffer_aux *aux = dm_bufio_get_aux_data(to_buffer(b));
605
606 if (aux->write_locked) {
607 dm_bufio_mark_buffer_dirty(to_buffer(b));
608 bl_up_write(&aux->lock);
609 } else
610 bl_up_read(&aux->lock);
611
612 dm_bufio_release(to_buffer(b));
613}
614EXPORT_SYMBOL_GPL(dm_bm_unlock);
615
616int dm_bm_flush(struct dm_block_manager *bm)
617{
618 if (dm_bm_is_read_only(bm))
619 return -EPERM;
620
621 return dm_bufio_write_dirty_buffers(bm->bufio);
622}
623EXPORT_SYMBOL_GPL(dm_bm_flush);
624
625void dm_bm_prefetch(struct dm_block_manager *bm, dm_block_t b)
626{
627 dm_bufio_prefetch(bm->bufio, b, 1);
628}
629
630bool dm_bm_is_read_only(struct dm_block_manager *bm)
631{
632 return bm ? bm->read_only : true;
633}
634EXPORT_SYMBOL_GPL(dm_bm_is_read_only);
635
636void dm_bm_set_read_only(struct dm_block_manager *bm)
637{
638 if (bm)
639 bm->read_only = true;
640}
641EXPORT_SYMBOL_GPL(dm_bm_set_read_only);
642
643void dm_bm_set_read_write(struct dm_block_manager *bm)
644{
645 if (bm)
646 bm->read_only = false;
647}
648EXPORT_SYMBOL_GPL(dm_bm_set_read_write);
649
650u32 dm_bm_checksum(const void *data, size_t len, u32 init_xor)
651{
652 return crc32c(~(u32) 0, data, len) ^ init_xor;
653}
654EXPORT_SYMBOL_GPL(dm_bm_checksum);
655
656/*----------------------------------------------------------------*/
657
658MODULE_LICENSE("GPL");
659MODULE_AUTHOR("Joe Thornber <[email protected]>");
660MODULE_DESCRIPTION("Immutable metadata library for dm");
661
662/*----------------------------------------------------------------*/