xref: /openbmc/linux/drivers/dma-buf/dma-resv.c (revision 083a7fba)
1 // SPDX-License-Identifier: MIT
2 /*
3  * Copyright (C) 2012-2014 Canonical Ltd (Maarten Lankhorst)
4  *
5  * Based on bo.c which bears the following copyright notice,
6  * but is dual licensed:
7  *
8  * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
9  * All Rights Reserved.
10  *
11  * Permission is hereby granted, free of charge, to any person obtaining a
12  * copy of this software and associated documentation files (the
13  * "Software"), to deal in the Software without restriction, including
14  * without limitation the rights to use, copy, modify, merge, publish,
15  * distribute, sub license, and/or sell copies of the Software, and to
16  * permit persons to whom the Software is furnished to do so, subject to
17  * the following conditions:
18  *
19  * The above copyright notice and this permission notice (including the
20  * next paragraph) shall be included in all copies or substantial portions
21  * of the Software.
22  *
23  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
24  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
25  * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
26  * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
27  * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
28  * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
29  * USE OR OTHER DEALINGS IN THE SOFTWARE.
30  *
31  **************************************************************************/
32 /*
33  * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
34  */
35 
36 #include <linux/dma-resv.h>
37 #include <linux/export.h>
38 #include <linux/mm.h>
39 #include <linux/sched/mm.h>
40 #include <linux/mmu_notifier.h>
41 
42 /**
43  * DOC: Reservation Object Overview
44  *
45  * The reservation object provides a mechanism to manage shared and
46  * exclusive fences associated with a buffer.  A reservation object
47  * can have attached one exclusive fence (normally associated with
48  * write operations) or N shared fences (read operations).  The RCU
49  * mechanism is used to protect read access to fences from locked
50  * write-side updates.
51  *
52  * See struct dma_resv for more details.
53  */
54 
55 DEFINE_WD_CLASS(reservation_ww_class);
56 EXPORT_SYMBOL(reservation_ww_class);
57 
58 /**
59  * dma_resv_list_alloc - allocate fence list
60  * @shared_max: number of fences we need space for
61  *
62  * Allocate a new dma_resv_list and make sure to correctly initialize
63  * shared_max.
64  */
65 static struct dma_resv_list *dma_resv_list_alloc(unsigned int shared_max)
66 {
67 	struct dma_resv_list *list;
68 
69 	list = kmalloc(struct_size(list, shared, shared_max), GFP_KERNEL);
70 	if (!list)
71 		return NULL;
72 
73 	list->shared_max = (ksize(list) - offsetof(typeof(*list), shared)) /
74 		sizeof(*list->shared);
75 
76 	return list;
77 }
78 
79 /**
80  * dma_resv_list_free - free fence list
81  * @list: list to free
82  *
83  * Free a dma_resv_list and make sure to drop all references.
84  */
85 static void dma_resv_list_free(struct dma_resv_list *list)
86 {
87 	unsigned int i;
88 
89 	if (!list)
90 		return;
91 
92 	for (i = 0; i < list->shared_count; ++i)
93 		dma_fence_put(rcu_dereference_protected(list->shared[i], true));
94 
95 	kfree_rcu(list, rcu);
96 }
97 
98 /**
99  * dma_resv_init - initialize a reservation object
100  * @obj: the reservation object
101  */
102 void dma_resv_init(struct dma_resv *obj)
103 {
104 	ww_mutex_init(&obj->lock, &reservation_ww_class);
105 	seqcount_ww_mutex_init(&obj->seq, &obj->lock);
106 
107 	RCU_INIT_POINTER(obj->fence, NULL);
108 	RCU_INIT_POINTER(obj->fence_excl, NULL);
109 }
110 EXPORT_SYMBOL(dma_resv_init);
111 
112 /**
113  * dma_resv_fini - destroys a reservation object
114  * @obj: the reservation object
115  */
116 void dma_resv_fini(struct dma_resv *obj)
117 {
118 	struct dma_resv_list *fobj;
119 	struct dma_fence *excl;
120 
121 	/*
122 	 * This object should be dead and all references must have
123 	 * been released to it, so no need to be protected with rcu.
124 	 */
125 	excl = rcu_dereference_protected(obj->fence_excl, 1);
126 	if (excl)
127 		dma_fence_put(excl);
128 
129 	fobj = rcu_dereference_protected(obj->fence, 1);
130 	dma_resv_list_free(fobj);
131 	ww_mutex_destroy(&obj->lock);
132 }
133 EXPORT_SYMBOL(dma_resv_fini);
134 
135 /**
136  * dma_resv_reserve_shared - Reserve space to add shared fences to
137  * a dma_resv.
138  * @obj: reservation object
139  * @num_fences: number of fences we want to add
140  *
141  * Should be called before dma_resv_add_shared_fence().  Must
142  * be called with @obj locked through dma_resv_lock().
143  *
144  * Note that the preallocated slots need to be re-reserved if @obj is unlocked
145  * at any time before calling dma_resv_add_shared_fence(). This is validated
146  * when CONFIG_DEBUG_MUTEXES is enabled.
147  *
148  * RETURNS
149  * Zero for success, or -errno
150  */
151 int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences)
152 {
153 	struct dma_resv_list *old, *new;
154 	unsigned int i, j, k, max;
155 
156 	dma_resv_assert_held(obj);
157 
158 	old = dma_resv_shared_list(obj);
159 	if (old && old->shared_max) {
160 		if ((old->shared_count + num_fences) <= old->shared_max)
161 			return 0;
162 		max = max(old->shared_count + num_fences, old->shared_max * 2);
163 	} else {
164 		max = max(4ul, roundup_pow_of_two(num_fences));
165 	}
166 
167 	new = dma_resv_list_alloc(max);
168 	if (!new)
169 		return -ENOMEM;
170 
171 	/*
172 	 * no need to bump fence refcounts, rcu_read access
173 	 * requires the use of kref_get_unless_zero, and the
174 	 * references from the old struct are carried over to
175 	 * the new.
176 	 */
177 	for (i = 0, j = 0, k = max; i < (old ? old->shared_count : 0); ++i) {
178 		struct dma_fence *fence;
179 
180 		fence = rcu_dereference_protected(old->shared[i],
181 						  dma_resv_held(obj));
182 		if (dma_fence_is_signaled(fence))
183 			RCU_INIT_POINTER(new->shared[--k], fence);
184 		else
185 			RCU_INIT_POINTER(new->shared[j++], fence);
186 	}
187 	new->shared_count = j;
188 
189 	/*
190 	 * We are not changing the effective set of fences here so can
191 	 * merely update the pointer to the new array; both existing
192 	 * readers and new readers will see exactly the same set of
193 	 * active (unsignaled) shared fences. Individual fences and the
194 	 * old array are protected by RCU and so will not vanish under
195 	 * the gaze of the rcu_read_lock() readers.
196 	 */
197 	rcu_assign_pointer(obj->fence, new);
198 
199 	if (!old)
200 		return 0;
201 
202 	/* Drop the references to the signaled fences */
203 	for (i = k; i < max; ++i) {
204 		struct dma_fence *fence;
205 
206 		fence = rcu_dereference_protected(new->shared[i],
207 						  dma_resv_held(obj));
208 		dma_fence_put(fence);
209 	}
210 	kfree_rcu(old, rcu);
211 
212 	return 0;
213 }
214 EXPORT_SYMBOL(dma_resv_reserve_shared);
215 
216 #ifdef CONFIG_DEBUG_MUTEXES
217 /**
218  * dma_resv_reset_shared_max - reset shared fences for debugging
219  * @obj: the dma_resv object to reset
220  *
221  * Reset the number of pre-reserved shared slots to test that drivers do
222  * correct slot allocation using dma_resv_reserve_shared(). See also
223  * &dma_resv_list.shared_max.
224  */
225 void dma_resv_reset_shared_max(struct dma_resv *obj)
226 {
227 	struct dma_resv_list *fences = dma_resv_shared_list(obj);
228 
229 	dma_resv_assert_held(obj);
230 
231 	/* Test shared fence slot reservation */
232 	if (fences)
233 		fences->shared_max = fences->shared_count;
234 }
235 EXPORT_SYMBOL(dma_resv_reset_shared_max);
236 #endif
237 
238 /**
239  * dma_resv_add_shared_fence - Add a fence to a shared slot
240  * @obj: the reservation object
241  * @fence: the shared fence to add
242  *
243  * Add a fence to a shared slot, @obj must be locked with dma_resv_lock(), and
244  * dma_resv_reserve_shared() has been called.
245  *
246  * See also &dma_resv.fence for a discussion of the semantics.
247  */
248 void dma_resv_add_shared_fence(struct dma_resv *obj, struct dma_fence *fence)
249 {
250 	struct dma_resv_list *fobj;
251 	struct dma_fence *old;
252 	unsigned int i, count;
253 
254 	dma_fence_get(fence);
255 
256 	dma_resv_assert_held(obj);
257 
258 	fobj = dma_resv_shared_list(obj);
259 	count = fobj->shared_count;
260 
261 	write_seqcount_begin(&obj->seq);
262 
263 	for (i = 0; i < count; ++i) {
264 
265 		old = rcu_dereference_protected(fobj->shared[i],
266 						dma_resv_held(obj));
267 		if (old->context == fence->context ||
268 		    dma_fence_is_signaled(old))
269 			goto replace;
270 	}
271 
272 	BUG_ON(fobj->shared_count >= fobj->shared_max);
273 	old = NULL;
274 	count++;
275 
276 replace:
277 	RCU_INIT_POINTER(fobj->shared[i], fence);
278 	/* pointer update must be visible before we extend the shared_count */
279 	smp_store_mb(fobj->shared_count, count);
280 
281 	write_seqcount_end(&obj->seq);
282 	dma_fence_put(old);
283 }
284 EXPORT_SYMBOL(dma_resv_add_shared_fence);
285 
286 /**
287  * dma_resv_add_excl_fence - Add an exclusive fence.
288  * @obj: the reservation object
289  * @fence: the exclusive fence to add
290  *
291  * Add a fence to the exclusive slot. @obj must be locked with dma_resv_lock().
292  * Note that this function replaces all fences attached to @obj, see also
293  * &dma_resv.fence_excl for a discussion of the semantics.
294  */
295 void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence)
296 {
297 	struct dma_fence *old_fence = dma_resv_excl_fence(obj);
298 	struct dma_resv_list *old;
299 	u32 i = 0;
300 
301 	dma_resv_assert_held(obj);
302 
303 	old = dma_resv_shared_list(obj);
304 	if (old)
305 		i = old->shared_count;
306 
307 	if (fence)
308 		dma_fence_get(fence);
309 
310 	write_seqcount_begin(&obj->seq);
311 	/* write_seqcount_begin provides the necessary memory barrier */
312 	RCU_INIT_POINTER(obj->fence_excl, fence);
313 	if (old)
314 		old->shared_count = 0;
315 	write_seqcount_end(&obj->seq);
316 
317 	/* inplace update, no shared fences */
318 	while (i--)
319 		dma_fence_put(rcu_dereference_protected(old->shared[i],
320 						dma_resv_held(obj)));
321 
322 	dma_fence_put(old_fence);
323 }
324 EXPORT_SYMBOL(dma_resv_add_excl_fence);
325 
326 /**
327  * dma_resv_iter_restart_unlocked - restart the unlocked iterator
328  * @cursor: The dma_resv_iter object to restart
329  *
330  * Restart the unlocked iteration by initializing the cursor object.
331  */
332 static void dma_resv_iter_restart_unlocked(struct dma_resv_iter *cursor)
333 {
334 	cursor->seq = read_seqcount_begin(&cursor->obj->seq);
335 	cursor->index = -1;
336 	cursor->shared_count = 0;
337 	if (cursor->all_fences) {
338 		cursor->fences = dma_resv_shared_list(cursor->obj);
339 		if (cursor->fences)
340 			cursor->shared_count = cursor->fences->shared_count;
341 	} else {
342 		cursor->fences = NULL;
343 	}
344 	cursor->is_restarted = true;
345 }
346 
347 /**
348  * dma_resv_iter_walk_unlocked - walk over fences in a dma_resv obj
349  * @cursor: cursor to record the current position
350  *
351  * Return all the fences in the dma_resv object which are not yet signaled.
352  * The returned fence has an extra local reference so will stay alive.
353  * If a concurrent modify is detected the whole iteration is started over again.
354  */
355 static void dma_resv_iter_walk_unlocked(struct dma_resv_iter *cursor)
356 {
357 	struct dma_resv *obj = cursor->obj;
358 
359 	do {
360 		/* Drop the reference from the previous round */
361 		dma_fence_put(cursor->fence);
362 
363 		if (cursor->index == -1) {
364 			cursor->fence = dma_resv_excl_fence(obj);
365 			cursor->index++;
366 			if (!cursor->fence)
367 				continue;
368 
369 		} else if (!cursor->fences ||
370 			   cursor->index >= cursor->shared_count) {
371 			cursor->fence = NULL;
372 			break;
373 
374 		} else {
375 			struct dma_resv_list *fences = cursor->fences;
376 			unsigned int idx = cursor->index++;
377 
378 			cursor->fence = rcu_dereference(fences->shared[idx]);
379 		}
380 		cursor->fence = dma_fence_get_rcu(cursor->fence);
381 		if (!cursor->fence || !dma_fence_is_signaled(cursor->fence))
382 			break;
383 	} while (true);
384 }
385 
386 /**
387  * dma_resv_iter_first_unlocked - first fence in an unlocked dma_resv obj.
388  * @cursor: the cursor with the current position
389  *
390  * Returns the first fence from an unlocked dma_resv obj.
391  */
392 struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor)
393 {
394 	rcu_read_lock();
395 	do {
396 		dma_resv_iter_restart_unlocked(cursor);
397 		dma_resv_iter_walk_unlocked(cursor);
398 	} while (read_seqcount_retry(&cursor->obj->seq, cursor->seq));
399 	rcu_read_unlock();
400 
401 	return cursor->fence;
402 }
403 EXPORT_SYMBOL(dma_resv_iter_first_unlocked);
404 
405 /**
406  * dma_resv_iter_next_unlocked - next fence in an unlocked dma_resv obj.
407  * @cursor: the cursor with the current position
408  *
409  * Returns the next fence from an unlocked dma_resv obj.
410  */
411 struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor)
412 {
413 	bool restart;
414 
415 	rcu_read_lock();
416 	cursor->is_restarted = false;
417 	restart = read_seqcount_retry(&cursor->obj->seq, cursor->seq);
418 	do {
419 		if (restart)
420 			dma_resv_iter_restart_unlocked(cursor);
421 		dma_resv_iter_walk_unlocked(cursor);
422 		restart = true;
423 	} while (read_seqcount_retry(&cursor->obj->seq, cursor->seq));
424 	rcu_read_unlock();
425 
426 	return cursor->fence;
427 }
428 EXPORT_SYMBOL(dma_resv_iter_next_unlocked);
429 
430 /**
431  * dma_resv_iter_first - first fence from a locked dma_resv object
432  * @cursor: cursor to record the current position
433  *
434  * Return the first fence in the dma_resv object while holding the
435  * &dma_resv.lock.
436  */
437 struct dma_fence *dma_resv_iter_first(struct dma_resv_iter *cursor)
438 {
439 	struct dma_fence *fence;
440 
441 	dma_resv_assert_held(cursor->obj);
442 
443 	cursor->index = 0;
444 	if (cursor->all_fences)
445 		cursor->fences = dma_resv_shared_list(cursor->obj);
446 	else
447 		cursor->fences = NULL;
448 
449 	fence = dma_resv_excl_fence(cursor->obj);
450 	if (!fence)
451 		fence = dma_resv_iter_next(cursor);
452 
453 	cursor->is_restarted = true;
454 	return fence;
455 }
456 EXPORT_SYMBOL_GPL(dma_resv_iter_first);
457 
458 /**
459  * dma_resv_iter_next - next fence from a locked dma_resv object
460  * @cursor: cursor to record the current position
461  *
462  * Return the next fences from the dma_resv object while holding the
463  * &dma_resv.lock.
464  */
465 struct dma_fence *dma_resv_iter_next(struct dma_resv_iter *cursor)
466 {
467 	unsigned int idx;
468 
469 	dma_resv_assert_held(cursor->obj);
470 
471 	cursor->is_restarted = false;
472 	if (!cursor->fences || cursor->index >= cursor->fences->shared_count)
473 		return NULL;
474 
475 	idx = cursor->index++;
476 	return rcu_dereference_protected(cursor->fences->shared[idx],
477 					 dma_resv_held(cursor->obj));
478 }
479 EXPORT_SYMBOL_GPL(dma_resv_iter_next);
480 
481 /**
482  * dma_resv_copy_fences - Copy all fences from src to dst.
483  * @dst: the destination reservation object
484  * @src: the source reservation object
485  *
486  * Copy all fences from src to dst. dst-lock must be held.
487  */
488 int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
489 {
490 	struct dma_resv_iter cursor;
491 	struct dma_resv_list *list;
492 	struct dma_fence *f, *excl;
493 
494 	dma_resv_assert_held(dst);
495 
496 	list = NULL;
497 	excl = NULL;
498 
499 	dma_resv_iter_begin(&cursor, src, true);
500 	dma_resv_for_each_fence_unlocked(&cursor, f) {
501 
502 		if (dma_resv_iter_is_restarted(&cursor)) {
503 			dma_resv_list_free(list);
504 			dma_fence_put(excl);
505 
506 			if (cursor.shared_count) {
507 				list = dma_resv_list_alloc(cursor.shared_count);
508 				if (!list) {
509 					dma_resv_iter_end(&cursor);
510 					return -ENOMEM;
511 				}
512 
513 				list->shared_count = 0;
514 
515 			} else {
516 				list = NULL;
517 			}
518 			excl = NULL;
519 		}
520 
521 		dma_fence_get(f);
522 		if (dma_resv_iter_is_exclusive(&cursor))
523 			excl = f;
524 		else
525 			RCU_INIT_POINTER(list->shared[list->shared_count++], f);
526 	}
527 	dma_resv_iter_end(&cursor);
528 
529 	write_seqcount_begin(&dst->seq);
530 	excl = rcu_replace_pointer(dst->fence_excl, excl, dma_resv_held(dst));
531 	list = rcu_replace_pointer(dst->fence, list, dma_resv_held(dst));
532 	write_seqcount_end(&dst->seq);
533 
534 	dma_resv_list_free(list);
535 	dma_fence_put(excl);
536 
537 	return 0;
538 }
539 EXPORT_SYMBOL(dma_resv_copy_fences);
540 
541 /**
542  * dma_resv_get_fences - Get an object's shared and exclusive
543  * fences without update side lock held
544  * @obj: the reservation object
545  * @fence_excl: the returned exclusive fence (or NULL)
546  * @shared_count: the number of shared fences returned
547  * @shared: the array of shared fence ptrs returned (array is krealloc'd to
548  * the required size, and must be freed by caller)
549  *
550  * Retrieve all fences from the reservation object. If the pointer for the
551  * exclusive fence is not specified the fence is put into the array of the
552  * shared fences as well. Returns either zero or -ENOMEM.
553  */
554 int dma_resv_get_fences(struct dma_resv *obj, struct dma_fence **fence_excl,
555 			unsigned int *shared_count, struct dma_fence ***shared)
556 {
557 	struct dma_resv_iter cursor;
558 	struct dma_fence *fence;
559 
560 	*shared_count = 0;
561 	*shared = NULL;
562 
563 	if (fence_excl)
564 		*fence_excl = NULL;
565 
566 	dma_resv_iter_begin(&cursor, obj, true);
567 	dma_resv_for_each_fence_unlocked(&cursor, fence) {
568 
569 		if (dma_resv_iter_is_restarted(&cursor)) {
570 			unsigned int count;
571 
572 			while (*shared_count)
573 				dma_fence_put((*shared)[--(*shared_count)]);
574 
575 			if (fence_excl)
576 				dma_fence_put(*fence_excl);
577 
578 			count = cursor.shared_count;
579 			count += fence_excl ? 0 : 1;
580 
581 			/* Eventually re-allocate the array */
582 			*shared = krealloc_array(*shared, count,
583 						 sizeof(void *),
584 						 GFP_KERNEL);
585 			if (count && !*shared) {
586 				dma_resv_iter_end(&cursor);
587 				return -ENOMEM;
588 			}
589 		}
590 
591 		dma_fence_get(fence);
592 		if (dma_resv_iter_is_exclusive(&cursor) && fence_excl)
593 			*fence_excl = fence;
594 		else
595 			(*shared)[(*shared_count)++] = fence;
596 	}
597 	dma_resv_iter_end(&cursor);
598 
599 	return 0;
600 }
601 EXPORT_SYMBOL_GPL(dma_resv_get_fences);
602 
603 /**
604  * dma_resv_wait_timeout - Wait on reservation's objects
605  * shared and/or exclusive fences.
606  * @obj: the reservation object
607  * @wait_all: if true, wait on all fences, else wait on just exclusive fence
608  * @intr: if true, do interruptible wait
609  * @timeout: timeout value in jiffies or zero to return immediately
610  *
611  * Callers are not required to hold specific locks, but maybe hold
612  * dma_resv_lock() already
613  * RETURNS
614  * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
615  * greater than zer on success.
616  */
617 long dma_resv_wait_timeout(struct dma_resv *obj, bool wait_all, bool intr,
618 			   unsigned long timeout)
619 {
620 	long ret = timeout ? timeout : 1;
621 	struct dma_resv_iter cursor;
622 	struct dma_fence *fence;
623 
624 	dma_resv_iter_begin(&cursor, obj, wait_all);
625 	dma_resv_for_each_fence_unlocked(&cursor, fence) {
626 
627 		ret = dma_fence_wait_timeout(fence, intr, ret);
628 		if (ret <= 0) {
629 			dma_resv_iter_end(&cursor);
630 			return ret;
631 		}
632 	}
633 	dma_resv_iter_end(&cursor);
634 
635 	return ret;
636 }
637 EXPORT_SYMBOL_GPL(dma_resv_wait_timeout);
638 
639 
640 /**
641  * dma_resv_test_signaled - Test if a reservation object's fences have been
642  * signaled.
643  * @obj: the reservation object
644  * @test_all: if true, test all fences, otherwise only test the exclusive
645  * fence
646  *
647  * Callers are not required to hold specific locks, but maybe hold
648  * dma_resv_lock() already.
649  *
650  * RETURNS
651  *
652  * True if all fences signaled, else false.
653  */
654 bool dma_resv_test_signaled(struct dma_resv *obj, bool test_all)
655 {
656 	struct dma_resv_iter cursor;
657 	struct dma_fence *fence;
658 
659 	dma_resv_iter_begin(&cursor, obj, test_all);
660 	dma_resv_for_each_fence_unlocked(&cursor, fence) {
661 		dma_resv_iter_end(&cursor);
662 		return false;
663 	}
664 	dma_resv_iter_end(&cursor);
665 	return true;
666 }
667 EXPORT_SYMBOL_GPL(dma_resv_test_signaled);
668 
669 #if IS_ENABLED(CONFIG_LOCKDEP)
670 static int __init dma_resv_lockdep(void)
671 {
672 	struct mm_struct *mm = mm_alloc();
673 	struct ww_acquire_ctx ctx;
674 	struct dma_resv obj;
675 	struct address_space mapping;
676 	int ret;
677 
678 	if (!mm)
679 		return -ENOMEM;
680 
681 	dma_resv_init(&obj);
682 	address_space_init_once(&mapping);
683 
684 	mmap_read_lock(mm);
685 	ww_acquire_init(&ctx, &reservation_ww_class);
686 	ret = dma_resv_lock(&obj, &ctx);
687 	if (ret == -EDEADLK)
688 		dma_resv_lock_slow(&obj, &ctx);
689 	fs_reclaim_acquire(GFP_KERNEL);
690 	/* for unmap_mapping_range on trylocked buffer objects in shrinkers */
691 	i_mmap_lock_write(&mapping);
692 	i_mmap_unlock_write(&mapping);
693 #ifdef CONFIG_MMU_NOTIFIER
694 	lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
695 	__dma_fence_might_wait();
696 	lock_map_release(&__mmu_notifier_invalidate_range_start_map);
697 #else
698 	__dma_fence_might_wait();
699 #endif
700 	fs_reclaim_release(GFP_KERNEL);
701 	ww_mutex_unlock(&obj.lock);
702 	ww_acquire_fini(&ctx);
703 	mmap_read_unlock(mm);
704 
705 	mmput(mm);
706 
707 	return 0;
708 }
709 subsys_initcall(dma_resv_lockdep);
710 #endif
711