Merge tag 'drm-intel-next-2021-12-14' of ssh://git.freedesktop.org/git/drm/drm-intel...
[linux-2.6-microblaze.git] / drivers / dma-buf / dma-resv.c
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 #include <linux/seq_file.h>
42
43 /**
44  * DOC: Reservation Object Overview
45  *
46  * The reservation object provides a mechanism to manage shared and
47  * exclusive fences associated with a buffer.  A reservation object
48  * can have attached one exclusive fence (normally associated with
49  * write operations) or N shared fences (read operations).  The RCU
50  * mechanism is used to protect read access to fences from locked
51  * write-side updates.
52  *
53  * See struct dma_resv for more details.
54  */
55
56 DEFINE_WD_CLASS(reservation_ww_class);
57 EXPORT_SYMBOL(reservation_ww_class);
58
59 /**
60  * dma_resv_list_alloc - allocate fence list
61  * @shared_max: number of fences we need space for
62  *
63  * Allocate a new dma_resv_list and make sure to correctly initialize
64  * shared_max.
65  */
66 static struct dma_resv_list *dma_resv_list_alloc(unsigned int shared_max)
67 {
68         struct dma_resv_list *list;
69
70         list = kmalloc(struct_size(list, shared, shared_max), GFP_KERNEL);
71         if (!list)
72                 return NULL;
73
74         list->shared_max = (ksize(list) - offsetof(typeof(*list), shared)) /
75                 sizeof(*list->shared);
76
77         return list;
78 }
79
80 /**
81  * dma_resv_list_free - free fence list
82  * @list: list to free
83  *
84  * Free a dma_resv_list and make sure to drop all references.
85  */
86 static void dma_resv_list_free(struct dma_resv_list *list)
87 {
88         unsigned int i;
89
90         if (!list)
91                 return;
92
93         for (i = 0; i < list->shared_count; ++i)
94                 dma_fence_put(rcu_dereference_protected(list->shared[i], true));
95
96         kfree_rcu(list, rcu);
97 }
98
99 /**
100  * dma_resv_init - initialize a reservation object
101  * @obj: the reservation object
102  */
103 void dma_resv_init(struct dma_resv *obj)
104 {
105         ww_mutex_init(&obj->lock, &reservation_ww_class);
106         seqcount_ww_mutex_init(&obj->seq, &obj->lock);
107
108         RCU_INIT_POINTER(obj->fence, NULL);
109         RCU_INIT_POINTER(obj->fence_excl, NULL);
110 }
111 EXPORT_SYMBOL(dma_resv_init);
112
113 /**
114  * dma_resv_fini - destroys a reservation object
115  * @obj: the reservation object
116  */
117 void dma_resv_fini(struct dma_resv *obj)
118 {
119         struct dma_resv_list *fobj;
120         struct dma_fence *excl;
121
122         /*
123          * This object should be dead and all references must have
124          * been released to it, so no need to be protected with rcu.
125          */
126         excl = rcu_dereference_protected(obj->fence_excl, 1);
127         if (excl)
128                 dma_fence_put(excl);
129
130         fobj = rcu_dereference_protected(obj->fence, 1);
131         dma_resv_list_free(fobj);
132         ww_mutex_destroy(&obj->lock);
133 }
134 EXPORT_SYMBOL(dma_resv_fini);
135
136 /**
137  * dma_resv_reserve_shared - Reserve space to add shared fences to
138  * a dma_resv.
139  * @obj: reservation object
140  * @num_fences: number of fences we want to add
141  *
142  * Should be called before dma_resv_add_shared_fence().  Must
143  * be called with @obj locked through dma_resv_lock().
144  *
145  * Note that the preallocated slots need to be re-reserved if @obj is unlocked
146  * at any time before calling dma_resv_add_shared_fence(). This is validated
147  * when CONFIG_DEBUG_MUTEXES is enabled.
148  *
149  * RETURNS
150  * Zero for success, or -errno
151  */
152 int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences)
153 {
154         struct dma_resv_list *old, *new;
155         unsigned int i, j, k, max;
156
157         dma_resv_assert_held(obj);
158
159         old = dma_resv_shared_list(obj);
160         if (old && old->shared_max) {
161                 if ((old->shared_count + num_fences) <= old->shared_max)
162                         return 0;
163                 max = max(old->shared_count + num_fences, old->shared_max * 2);
164         } else {
165                 max = max(4ul, roundup_pow_of_two(num_fences));
166         }
167
168         new = dma_resv_list_alloc(max);
169         if (!new)
170                 return -ENOMEM;
171
172         /*
173          * no need to bump fence refcounts, rcu_read access
174          * requires the use of kref_get_unless_zero, and the
175          * references from the old struct are carried over to
176          * the new.
177          */
178         for (i = 0, j = 0, k = max; i < (old ? old->shared_count : 0); ++i) {
179                 struct dma_fence *fence;
180
181                 fence = rcu_dereference_protected(old->shared[i],
182                                                   dma_resv_held(obj));
183                 if (dma_fence_is_signaled(fence))
184                         RCU_INIT_POINTER(new->shared[--k], fence);
185                 else
186                         RCU_INIT_POINTER(new->shared[j++], fence);
187         }
188         new->shared_count = j;
189
190         /*
191          * We are not changing the effective set of fences here so can
192          * merely update the pointer to the new array; both existing
193          * readers and new readers will see exactly the same set of
194          * active (unsignaled) shared fences. Individual fences and the
195          * old array are protected by RCU and so will not vanish under
196          * the gaze of the rcu_read_lock() readers.
197          */
198         rcu_assign_pointer(obj->fence, new);
199
200         if (!old)
201                 return 0;
202
203         /* Drop the references to the signaled fences */
204         for (i = k; i < max; ++i) {
205                 struct dma_fence *fence;
206
207                 fence = rcu_dereference_protected(new->shared[i],
208                                                   dma_resv_held(obj));
209                 dma_fence_put(fence);
210         }
211         kfree_rcu(old, rcu);
212
213         return 0;
214 }
215 EXPORT_SYMBOL(dma_resv_reserve_shared);
216
217 #ifdef CONFIG_DEBUG_MUTEXES
218 /**
219  * dma_resv_reset_shared_max - reset shared fences for debugging
220  * @obj: the dma_resv object to reset
221  *
222  * Reset the number of pre-reserved shared slots to test that drivers do
223  * correct slot allocation using dma_resv_reserve_shared(). See also
224  * &dma_resv_list.shared_max.
225  */
226 void dma_resv_reset_shared_max(struct dma_resv *obj)
227 {
228         struct dma_resv_list *fences = dma_resv_shared_list(obj);
229
230         dma_resv_assert_held(obj);
231
232         /* Test shared fence slot reservation */
233         if (fences)
234                 fences->shared_max = fences->shared_count;
235 }
236 EXPORT_SYMBOL(dma_resv_reset_shared_max);
237 #endif
238
239 /**
240  * dma_resv_add_shared_fence - Add a fence to a shared slot
241  * @obj: the reservation object
242  * @fence: the shared fence to add
243  *
244  * Add a fence to a shared slot, @obj must be locked with dma_resv_lock(), and
245  * dma_resv_reserve_shared() has been called.
246  *
247  * See also &dma_resv.fence for a discussion of the semantics.
248  */
249 void dma_resv_add_shared_fence(struct dma_resv *obj, struct dma_fence *fence)
250 {
251         struct dma_resv_list *fobj;
252         struct dma_fence *old;
253         unsigned int i, count;
254
255         dma_fence_get(fence);
256
257         dma_resv_assert_held(obj);
258
259         fobj = dma_resv_shared_list(obj);
260         count = fobj->shared_count;
261
262         write_seqcount_begin(&obj->seq);
263
264         for (i = 0; i < count; ++i) {
265
266                 old = rcu_dereference_protected(fobj->shared[i],
267                                                 dma_resv_held(obj));
268                 if (old->context == fence->context ||
269                     dma_fence_is_signaled(old))
270                         goto replace;
271         }
272
273         BUG_ON(fobj->shared_count >= fobj->shared_max);
274         old = NULL;
275         count++;
276
277 replace:
278         RCU_INIT_POINTER(fobj->shared[i], fence);
279         /* pointer update must be visible before we extend the shared_count */
280         smp_store_mb(fobj->shared_count, count);
281
282         write_seqcount_end(&obj->seq);
283         dma_fence_put(old);
284 }
285 EXPORT_SYMBOL(dma_resv_add_shared_fence);
286
287 /**
288  * dma_resv_add_excl_fence - Add an exclusive fence.
289  * @obj: the reservation object
290  * @fence: the exclusive fence to add
291  *
292  * Add a fence to the exclusive slot. @obj must be locked with dma_resv_lock().
293  * Note that this function replaces all fences attached to @obj, see also
294  * &dma_resv.fence_excl for a discussion of the semantics.
295  */
296 void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence)
297 {
298         struct dma_fence *old_fence = dma_resv_excl_fence(obj);
299         struct dma_resv_list *old;
300         u32 i = 0;
301
302         dma_resv_assert_held(obj);
303
304         old = dma_resv_shared_list(obj);
305         if (old)
306                 i = old->shared_count;
307
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 /**
670  * dma_resv_describe - Dump description of the resv object into seq_file
671  * @obj: the reservation object
672  * @seq: the seq_file to dump the description into
673  *
674  * Dump a textual description of the fences inside an dma_resv object into the
675  * seq_file.
676  */
677 void dma_resv_describe(struct dma_resv *obj, struct seq_file *seq)
678 {
679         struct dma_resv_iter cursor;
680         struct dma_fence *fence;
681
682         dma_resv_for_each_fence(&cursor, obj, true, fence) {
683                 seq_printf(seq, "\t%s fence:",
684                            dma_resv_iter_is_exclusive(&cursor) ?
685                                 "Exclusive" : "Shared");
686                 dma_fence_describe(fence, seq);
687         }
688 }
689 EXPORT_SYMBOL_GPL(dma_resv_describe);
690
691 #if IS_ENABLED(CONFIG_LOCKDEP)
692 static int __init dma_resv_lockdep(void)
693 {
694         struct mm_struct *mm = mm_alloc();
695         struct ww_acquire_ctx ctx;
696         struct dma_resv obj;
697         struct address_space mapping;
698         int ret;
699
700         if (!mm)
701                 return -ENOMEM;
702
703         dma_resv_init(&obj);
704         address_space_init_once(&mapping);
705
706         mmap_read_lock(mm);
707         ww_acquire_init(&ctx, &reservation_ww_class);
708         ret = dma_resv_lock(&obj, &ctx);
709         if (ret == -EDEADLK)
710                 dma_resv_lock_slow(&obj, &ctx);
711         fs_reclaim_acquire(GFP_KERNEL);
712         /* for unmap_mapping_range on trylocked buffer objects in shrinkers */
713         i_mmap_lock_write(&mapping);
714         i_mmap_unlock_write(&mapping);
715 #ifdef CONFIG_MMU_NOTIFIER
716         lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
717         __dma_fence_might_wait();
718         lock_map_release(&__mmu_notifier_invalidate_range_start_map);
719 #else
720         __dma_fence_might_wait();
721 #endif
722         fs_reclaim_release(GFP_KERNEL);
723         ww_mutex_unlock(&obj.lock);
724         ww_acquire_fini(&ctx);
725         mmap_read_unlock(mm);
726
727         mmput(mm);
728
729         return 0;
730 }
731 subsys_initcall(dma_resv_lockdep);
732 #endif