summaryrefslogtreecommitdiff
path: root/drivers/gpu/drm/drm_gem.c
blob: aa15c52ae18218bba358b5fb4dce8eab8396b644 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
/*
 * Copyright © 2008 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 *
 * Authors:
 *    Eric Anholt <eric@anholt.net>
 *
 */

#include <linux/dma-buf.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/iosys-map.h>
#include <linux/mem_encrypt.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/module.h>
#include <linux/pagemap.h>
#include <linux/pagevec.h>
#include <linux/shmem_fs.h>
#include <linux/slab.h>
#include <linux/string_helpers.h>
#include <linux/types.h>
#include <linux/uaccess.h>

#include <drm/drm.h>
#include <drm/drm_device.h>
#include <drm/drm_drv.h>
#include <drm/drm_file.h>
#include <drm/drm_gem.h>
#include <drm/drm_managed.h>
#include <drm/drm_print.h>
#include <drm/drm_vma_manager.h>

#include "drm_internal.h"

/** @file drm_gem.c
 *
 * This file provides some of the base ioctls and library routines for
 * the graphics memory manager implemented by each device driver.
 *
 * Because various devices have different requirements in terms of
 * synchronization and migration strategies, implementing that is left up to
 * the driver, and all that the general API provides should be generic --
 * allocating objects, reading/writing data with the cpu, freeing objects.
 * Even there, platform-dependent optimizations for reading/writing data with
 * the CPU mean we'll likely hook those out to driver-specific calls.  However,
 * the DRI2 implementation wants to have at least allocate/mmap be generic.
 *
 * The goal was to have swap-backed object allocation managed through
 * struct file.  However, file descriptors as handles to a struct file have
 * two major failings:
 * - Process limits prevent more than 1024 or so being used at a time by
 *   default.
 * - Inability to allocate high fds will aggravate the X Server's select()
 *   handling, and likely that of many GL client applications as well.
 *
 * This led to a plan of using our own integer IDs (called handles, following
 * DRM terminology) to mimic fds, and implement the fd syscalls we need as
 * ioctls.  The objects themselves will still include the struct file so
 * that we can transition to fds if the required kernel infrastructure shows
 * up at a later date, and as our interface with shmfs for memory allocation.
 */

static void
drm_gem_init_release(struct drm_device *dev, void *ptr)
{
	drm_vma_offset_manager_destroy(dev->vma_offset_manager);
}

/**
 * drm_gem_init - Initialize the GEM device fields
 * @dev: drm_devic structure to initialize
 */
int
drm_gem_init(struct drm_device *dev)
{
	struct drm_vma_offset_manager *vma_offset_manager;

	mutex_init(&dev->object_name_lock);
	idr_init_base(&dev->object_name_idr, 1);

	vma_offset_manager = drmm_kzalloc(dev, sizeof(*vma_offset_manager),
					  GFP_KERNEL);
	if (!vma_offset_manager) {
		DRM_ERROR("out of memory\n");
		return -ENOMEM;
	}

	dev->vma_offset_manager = vma_offset_manager;
	drm_vma_offset_manager_init(vma_offset_manager,
				    DRM_FILE_PAGE_OFFSET_START,
				    DRM_FILE_PAGE_OFFSET_SIZE);

	return drmm_add_action(dev, drm_gem_init_release, NULL);
}

/**
 * drm_gem_object_init - initialize an allocated shmem-backed GEM object
 * @dev: drm_device the object should be initialized for
 * @obj: drm_gem_object to initialize
 * @size: object size
 *
 * Initialize an already allocated GEM object of the specified size with
 * shmfs backing store.
 */
int drm_gem_object_init(struct drm_device *dev,
			struct drm_gem_object *obj, size_t size)
{
	struct file *filp;

	drm_gem_private_object_init(dev, obj, size);

	filp = shmem_file_setup("drm mm object", size, VM_NORESERVE);
	if (IS_ERR(filp))
		return PTR_ERR(filp);

	obj->filp = filp;

	return 0;
}
EXPORT_SYMBOL(drm_gem_object_init);

/**
 * drm_gem_private_object_init - initialize an allocated private GEM object
 * @dev: drm_device the object should be initialized for
 * @obj: drm_gem_object to initialize
 * @size: object size
 *
 * Initialize an already allocated GEM object of the specified size with
 * no GEM provided backing store. Instead the caller is responsible for
 * backing the object and handling it.
 */
void drm_gem_private_object_init(struct drm_device *dev,
				 struct drm_gem_object *obj, size_t size)
{
	BUG_ON((size & (PAGE_SIZE - 1)) != 0);

	obj->dev = dev;
	obj->filp = NULL;

	kref_init(&obj->refcount);
	obj->handle_count = 0;
	obj->size = size;
	dma_resv_init(&obj->_resv);
	if (!obj->resv)
		obj->resv = &obj->_resv;

	drm_vma_node_reset(&obj->vma_node);
	INIT_LIST_HEAD(&obj->lru_node);
}
EXPORT_SYMBOL(drm_gem_private_object_init);

/**
 * drm_gem_private_object_fini - Finalize a failed drm_gem_object
 * @obj: drm_gem_object
 *
 * Uninitialize an already allocated GEM object when it initialized failed
 */
void drm_gem_private_object_fini(struct drm_gem_object *obj)
{
	WARN_ON(obj->dma_buf);

	dma_resv_fini(&obj->_resv);
}
EXPORT_SYMBOL(drm_gem_private_object_fini);

/**
 * drm_gem_object_handle_free - release resources bound to userspace handles
 * @obj: GEM object to clean up.
 *
 * Called after the last handle to the object has been closed
 *
 * Removes any name for the object. Note that this must be
 * called before drm_gem_object_free or we'll be touching
 * freed memory
 */
static void drm_gem_object_handle_free(struct drm_gem_object *obj)
{
	struct drm_device *dev = obj->dev;

	/* Remove any name for this object */
	if (obj->name) {
		idr_remove(&dev->object_name_idr, obj->name);
		obj->name = 0;
	}
}

static void drm_gem_object_exported_dma_buf_free(struct drm_gem_object *obj)
{
	/* Unbreak the reference cycle if we have an exported dma_buf. */
	if (obj->dma_buf) {
		dma_buf_put(obj->dma_buf);
		obj->dma_buf = NULL;
	}
}

static void
drm_gem_object_handle_put_unlocked(struct drm_gem_object *obj)
{
	struct drm_device *dev = obj->dev;
	bool final = false;

	if (WARN_ON(READ_ONCE(obj->handle_count) == 0))
		return;

	/*
	* Must bump handle count first as this may be the last
	* ref, in which case the object would disappear before we
	* checked for a name
	*/

	mutex_lock(&dev->object_name_lock);
	if (--obj->handle_count == 0) {
		drm_gem_object_handle_free(obj);
		drm_gem_object_exported_dma_buf_free(obj);
		final = true;
	}
	mutex_unlock(&dev->object_name_lock);

	if (final)
		drm_gem_object_put(obj);
}

/*
 * Called at device or object close to release the file's
 * handle references on objects.
 */
static int
drm_gem_object_release_handle(int id, void *ptr, void *data)
{
	struct drm_file *file_priv = data;
	struct drm_gem_object *obj = ptr;

	if (obj->funcs->close)
		obj->funcs->close(obj, file_priv);

	drm_prime_remove_buf_handle(&file_priv->prime, id);
	drm_vma_node_revoke(&obj->vma_node, file_priv);

	drm_gem_object_handle_put_unlocked(obj);

	return 0;
}

/**
 * drm_gem_handle_delete - deletes the given file-private handle
 * @filp: drm file-private structure to use for the handle look up
 * @handle: userspace handle to delete
 *
 * Removes the GEM handle from the @filp lookup table which has been added with
 * drm_gem_handle_create(). If this is the last handle also cleans up linked
 * resources like GEM names.
 */
int
drm_gem_handle_delete(struct drm_file *filp, u32 handle)
{
	struct drm_gem_object *obj;

	spin_lock(&filp->table_lock);

	/* Check if we currently have a reference on the object */
	obj = idr_replace(&filp->object_idr, NULL, handle);
	spin_unlock(&filp->table_lock);
	if (IS_ERR_OR_NULL(obj))
		return -EINVAL;

	/* Release driver's reference and decrement refcount. */
	drm_gem_object_release_handle(handle, obj, filp);

	/* And finally make the handle available for future allocations. */
	spin_lock(&filp->table_lock);
	idr_remove(&filp->object_idr, handle);
	spin_unlock(&filp->table_lock);

	return 0;
}
EXPORT_SYMBOL(drm_gem_handle_delete);

/**
 * drm_gem_dumb_map_offset - return the fake mmap offset for a gem object
 * @file: drm file-private structure containing the gem object
 * @dev: corresponding drm_device
 * @handle: gem object handle
 * @offset: return location for the fake mmap offset
 *
 * This implements the &drm_driver.dumb_map_offset kms driver callback for
 * drivers which use gem to manage their backing storage.
 *
 * Returns:
 * 0 on success or a negative error code on failure.
 */
int drm_gem_dumb_map_offset(struct drm_file *file, struct drm_device *dev,
			    u32 handle, u64 *offset)
{
	struct drm_gem_object *obj;
	int ret;

	obj = drm_gem_object_lookup(file, handle);
	if (!obj)
		return -ENOENT;

	/* Don't allow imported objects to be mapped */
	if (obj->import_attach) {
		ret = -EINVAL;
		goto out;
	}

	ret = drm_gem_create_mmap_offset(obj);
	if (ret)
		goto out;

	*offset = drm_vma_node_offset_addr(&obj->vma_node);
out:
	drm_gem_object_put(obj);

	return ret;
}
EXPORT_SYMBOL_GPL(drm_gem_dumb_map_offset);

/**
 * drm_gem_handle_create_tail - internal functions to create a handle
 * @file_priv: drm file-private structure to register the handle for
 * @obj: object to register
 * @handlep: pointer to return the created handle to the caller
 *
 * This expects the &drm_device.object_name_lock to be held already and will
 * drop it before returning. Used to avoid races in establishing new handles
 * when importing an object from either an flink name or a dma-buf.
 *
 * Handles must be release again through drm_gem_handle_delete(). This is done
 * when userspace closes @file_priv for all attached handles, or through the
 * GEM_CLOSE ioctl for individual handles.
 */
int
drm_gem_handle_create_tail(struct drm_file *file_priv,
			   struct drm_gem_object *obj,
			   u32 *handlep)
{
	struct drm_device *dev = obj->dev;
	u32 handle;
	int ret;

	WARN_ON(!mutex_is_locked(&dev->object_name_lock));
	if (obj->handle_count++ == 0)
		drm_gem_object_get(obj);

	/*
	 * Get the user-visible handle using idr.  Preload and perform
	 * allocation under our spinlock.
	 */
	idr_preload(GFP_KERNEL);
	spin_lock(&file_priv->table_lock);

	ret = idr_alloc(&file_priv->object_idr, obj, 1, 0, GFP_NOWAIT);

	spin_unlock(&file_priv->table_lock);
	idr_preload_end();

	mutex_unlock(&dev->object_name_lock);
	if (ret < 0)
		goto err_unref;

	handle = ret;

	ret = drm_vma_node_allow(&obj->vma_node, file_priv);
	if (ret)
		goto err_remove;

	if (obj->funcs->open) {
		ret = obj->funcs->open(obj, file_priv);
		if (ret)
			goto err_revoke;
	}

	*handlep = handle;
	return 0;

err_revoke:
	drm_vma_node_revoke(&obj->vma_node, file_priv);
err_remove:
	spin_lock(&file_priv->table_lock);
	idr_remove(&file_priv->object_idr, handle);
	spin_unlock(&file_priv->table_lock);
err_unref:
	drm_gem_object_handle_put_unlocked(obj);
	return ret;
}

/**
 * drm_gem_handle_create - create a gem handle for an object
 * @file_priv: drm file-private structure to register the handle for
 * @obj: object to register
 * @handlep: pointer to return the created handle to the caller
 *
 * Create a handle for this object. This adds a handle reference to the object,
 * which includes a regular reference count. Callers will likely want to
 * dereference the object afterwards.
 *
 * Since this publishes @obj to userspace it must be fully set up by this point,
 * drivers must call this last in their buffer object creation callbacks.
 */
int drm_gem_handle_create(struct drm_file *file_priv,
			  struct drm_gem_object *obj,
			  u32 *handlep)
{
	mutex_lock(&obj->dev->object_name_lock);

	return drm_gem_handle_create_tail(file_priv, obj, handlep);
}
EXPORT_SYMBOL(drm_gem_handle_create);


/**
 * drm_gem_free_mmap_offset - release a fake mmap offset for an object
 * @obj: obj in question
 *
 * This routine frees fake offsets allocated by drm_gem_create_mmap_offset().
 *
 * Note that drm_gem_object_release() already calls this function, so drivers
 * don't have to take care of releasing the mmap offset themselves when freeing
 * the GEM object.
 */
void
drm_gem_free_mmap_offset(struct drm_gem_object *obj)
{
	struct drm_device *dev = obj->dev;

	drm_vma_offset_remove(dev->vma_offset_manager, &obj->vma_node);
}
EXPORT_SYMBOL(drm_gem_free_mmap_offset);

/**
 * drm_gem_create_mmap_offset_size - create a fake mmap offset for an object
 * @obj: obj in question
 * @size: the virtual size
 *
 * GEM memory mapping works by handing back to userspace a fake mmap offset
 * it can use in a subsequent mmap(2) call.  The DRM core code then looks
 * up the object based on the offset and sets up the various memory mapping
 * structures.
 *
 * This routine allocates and attaches a fake offset for @obj, in cases where
 * the virtual size differs from the physical size (ie. &drm_gem_object.size).
 * Otherwise just use drm_gem_create_mmap_offset().
 *
 * This function is idempotent and handles an already allocated mmap offset
 * transparently. Drivers do not need to check for this case.
 */
int
drm_gem_create_mmap_offset_size(struct drm_gem_object *obj, size_t size)
{
	struct drm_device *dev = obj->dev;

	return drm_vma_offset_add(dev->vma_offset_manager, &obj->vma_node,
				  size / PAGE_SIZE);
}
EXPORT_SYMBOL(drm_gem_create_mmap_offset_size);

/**
 * drm_gem_create_mmap_offset - create a fake mmap offset for an object
 * @obj: obj in question
 *
 * GEM memory mapping works by handing back to userspace a fake mmap offset
 * it can use in a subsequent mmap(2) call.  The DRM core code then looks
 * up the object based on the offset and sets up the various memory mapping
 * structures.
 *
 * This routine allocates and attaches a fake offset for @obj.
 *
 * Drivers can call drm_gem_free_mmap_offset() before freeing @obj to release
 * the fake offset again.
 */
int drm_gem_create_mmap_offset(struct drm_gem_object *obj)
{
	return drm_gem_create_mmap_offset_size(obj, obj->size);
}
EXPORT_SYMBOL(drm_gem_create_mmap_offset);

/*
 * Move pages to appropriate lru and release the pagevec, decrementing the
 * ref count of those pages.
 */
static void drm_gem_check_release_pagevec(struct pagevec *pvec)
{
	check_move_unevictable_pages(pvec);
	__pagevec_release(pvec);
	cond_resched();
}

/**
 * drm_gem_get_pages - helper to allocate backing pages for a GEM object
 * from shmem
 * @obj: obj in question
 *
 * This reads the page-array of the shmem-backing storage of the given gem
 * object. An array of pages is returned. If a page is not allocated or
 * swapped-out, this will allocate/swap-in the required pages. Note that the
 * whole object is covered by the page-array and pinned in memory.
 *
 * Use drm_gem_put_pages() to release the array and unpin all pages.
 *
 * This uses the GFP-mask set on the shmem-mapping (see mapping_set_gfp_mask()).
 * If you require other GFP-masks, you have to do those allocations yourself.
 *
 * Note that you are not allowed to change gfp-zones during runtime. That is,
 * shmem_read_mapping_page_gfp() must be called with the same gfp_zone(gfp) as
 * set during initialization. If you have special zone constraints, set them
 * after drm_gem_object_init() via mapping_set_gfp_mask(). shmem-core takes care
 * to keep pages in the required zone during swap-in.
 *
 * This function is only valid on objects initialized with
 * drm_gem_object_init(), but not for those initialized with
 * drm_gem_private_object_init() only.
 */
struct page **drm_gem_get_pages(struct drm_gem_object *obj)
{
	struct address_space *mapping;
	struct page *p, **pages;
	struct pagevec pvec;
	int i, npages;


	if (WARN_ON(!obj->filp))
		return ERR_PTR(-EINVAL);

	/* This is the shared memory object that backs the GEM resource */
	mapping = obj->filp->f_mapping;

	/* We already BUG_ON() for non-page-aligned sizes in
	 * drm_gem_object_init(), so we should never hit this unless
	 * driver author is doing something really wrong:
	 */
	WARN_ON((obj->size & (PAGE_SIZE - 1)) != 0);

	npages = obj->size >> PAGE_SHIFT;

	pages = kvmalloc_array(npages, sizeof(struct page *), GFP_KERNEL);
	if (pages == NULL)
		return ERR_PTR(-ENOMEM);

	mapping_set_unevictable(mapping);

	for (i = 0; i < npages; i++) {
		p = shmem_read_mapping_page(mapping, i);
		if (IS_ERR(p))
			goto fail;
		pages[i] = p;

		/* Make sure shmem keeps __GFP_DMA32 allocated pages in the
		 * correct region during swapin. Note that this requires
		 * __GFP_DMA32 to be set in mapping_gfp_mask(inode->i_mapping)
		 * so shmem can relocate pages during swapin if required.
		 */
		BUG_ON(mapping_gfp_constraint(mapping, __GFP_DMA32) &&
				(page_to_pfn(p) >= 0x00100000UL));
	}

	return pages;

fail:
	mapping_clear_unevictable(mapping);
	pagevec_init(&pvec);
	while (i--) {
		if (!pagevec_add(&pvec, pages[i]))
			drm_gem_check_release_pagevec(&pvec);
	}
	if (pagevec_count(&pvec))
		drm_gem_check_release_pagevec(&pvec);

	kvfree(pages);
	return ERR_CAST(p);
}
EXPORT_SYMBOL(drm_gem_get_pages);

/**
 * drm_gem_put_pages - helper to free backing pages for a GEM object
 * @obj: obj in question
 * @pages: pages to free
 * @dirty: if true, pages will be marked as dirty
 * @accessed: if true, the pages will be marked as accessed
 */
void drm_gem_put_pages(struct drm_gem_object *obj, struct page **pages,
		bool dirty, bool accessed)
{
	int i, npages;
	struct address_space *mapping;
	struct pagevec pvec;

	mapping = file_inode(obj->filp)->i_mapping;
	mapping_clear_unevictable(mapping);

	/* We already BUG_ON() for non-page-aligned sizes in
	 * drm_gem_object_init(), so we should never hit this unless
	 * driver author is doing something really wrong:
	 */
	WARN_ON((obj->size & (PAGE_SIZE - 1)) != 0);

	npages = obj->size >> PAGE_SHIFT;

	pagevec_init(&pvec);
	for (i = 0; i < npages; i++) {
		if (!pages[i])
			continue;

		if (dirty)
			set_page_dirty(pages[i]);

		if (accessed)
			mark_page_accessed(pages[i]);

		/* Undo the reference we took when populating the table */
		if (!pagevec_add(&pvec, pages[i]))
			drm_gem_check_release_pagevec(&pvec);
	}
	if (pagevec_count(&pvec))
		drm_gem_check_release_pagevec(&pvec);

	kvfree(pages);
}
EXPORT_SYMBOL(drm_gem_put_pages);

static int objects_lookup(struct drm_file *filp, u32 *handle, int count,
			  struct drm_gem_object **objs)
{
	int i, ret = 0;
	struct drm_gem_object *obj;

	spin_lock(&filp->table_lock);

	for (i = 0; i < count; i++) {
		/* Check if we currently have a reference on the object */
		obj = idr_find(&filp->object_idr, handle[i]);
		if (!obj) {
			ret = -ENOENT;
			break;
		}
		drm_gem_object_get(obj);
		objs[i] = obj;
	}
	spin_unlock(&filp->table_lock);

	return ret;
}

/**
 * drm_gem_objects_lookup - look up GEM objects from an array of handles
 * @filp: DRM file private date
 * @bo_handles: user pointer to array of userspace handle
 * @count: size of handle array
 * @objs_out: returned pointer to array of drm_gem_object pointers
 *
 * Takes an array of userspace handles and returns a newly allocated array of
 * GEM objects.
 *
 * For a single handle lookup, use drm_gem_object_lookup().
 *
 * Returns:
 *
 * @objs filled in with GEM object pointers. Returned GEM objects need to be
 * released with drm_gem_object_put(). -ENOENT is returned on a lookup
 * failure. 0 is returned on success.
 *
 */
int drm_gem_objects_lookup(struct drm_file *filp, void __user *bo_handles,
			   int count, struct drm_gem_object ***objs_out)
{
	int ret;
	u32 *handles;
	struct drm_gem_object **objs;

	if (!count)
		return 0;

	objs = kvmalloc_array(count, sizeof(struct drm_gem_object *),
			     GFP_KERNEL | __GFP_ZERO);
	if (!objs)
		return -ENOMEM;

	*objs_out = objs;

	handles = kvmalloc_array(count, sizeof(u32), GFP_KERNEL);
	if (!handles) {
		ret = -ENOMEM;
		goto out;
	}

	if (copy_from_user(handles, bo_handles, count * sizeof(u32))) {
		ret = -EFAULT;
		DRM_DEBUG("Failed to copy in GEM handles\n");
		goto out;
	}

	ret = objects_lookup(filp, handles, count, objs);
out:
	kvfree(handles);
	return ret;

}
EXPORT_SYMBOL(drm_gem_objects_lookup);

/**
 * drm_gem_object_lookup - look up a GEM object from its handle
 * @filp: DRM file private date
 * @handle: userspace handle
 *
 * Returns:
 *
 * A reference to the object named by the handle if such exists on @filp, NULL
 * otherwise.
 *
 * If looking up an array of handles, use drm_gem_objects_lookup().
 */
struct drm_gem_object *
drm_gem_object_lookup(struct drm_file *filp, u32 handle)
{
	struct drm_gem_object *obj = NULL;

	objects_lookup(filp, &handle, 1, &obj);
	return obj;
}
EXPORT_SYMBOL(drm_gem_object_lookup);

/**
 * drm_gem_dma_resv_wait - Wait on GEM object's reservation's objects
 * shared and/or exclusive fences.
 * @filep: DRM file private date
 * @handle: userspace handle
 * @wait_all: if true, wait on all fences, else wait on just exclusive fence
 * @timeout: timeout value in jiffies or zero to return immediately
 *
 * Returns:
 *
 * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
 * greater than 0 on success.
 */
long drm_gem_dma_resv_wait(struct drm_file *filep, u32 handle,
				    bool wait_all, unsigned long timeout)
{
	long ret;
	struct drm_gem_object *obj;

	obj = drm_gem_object_lookup(filep, handle);
	if (!obj) {
		DRM_DEBUG("Failed to look up GEM BO %d\n", handle);
		return -EINVAL;
	}

	ret = dma_resv_wait_timeout(obj->resv, dma_resv_usage_rw(wait_all),
				    true, timeout);
	if (ret == 0)
		ret = -ETIME;
	else if (ret > 0)
		ret = 0;

	drm_gem_object_put(obj);

	return ret;
}
EXPORT_SYMBOL(drm_gem_dma_resv_wait);

/**
 * drm_gem_close_ioctl - implementation of the GEM_CLOSE ioctl
 * @dev: drm_device
 * @data: ioctl data
 * @file_priv: drm file-private structure
 *
 * Releases the handle to an mm object.
 */
int
drm_gem_close_ioctl(struct drm_device *dev, void *data,
		    struct drm_file *file_priv)
{
	struct drm_gem_close *args = data;
	int ret;

	if (!drm_core_check_feature(dev, DRIVER_GEM))
		return -EOPNOTSUPP;

	ret = drm_gem_handle_delete(file_priv, args->handle);

	return ret;
}

/**
 * drm_gem_flink_ioctl - implementation of the GEM_FLINK ioctl
 * @dev: drm_device
 * @data: ioctl data
 * @file_priv: drm file-private structure
 *
 * Create a global name for an object, returning the name.
 *
 * Note that the name does not hold a reference; when the object
 * is freed, the name goes away.
 */
int
drm_gem_flink_ioctl(struct drm_device *dev, void *data,
		    struct drm_file *file_priv)
{
	struct drm_gem_flink *args = data;
	struct drm_gem_object *obj;
	int ret;

	if (!drm_core_check_feature(dev, DRIVER_GEM))
		return -EOPNOTSUPP;

	obj = drm_gem_object_lookup(file_priv, args->handle);
	if (obj == NULL)
		return -ENOENT;

	mutex_lock(&dev->object_name_lock);
	/* prevent races with concurrent gem_close. */
	if (obj->handle_count == 0) {
		ret = -ENOENT;
		goto err;
	}

	if (!obj->name) {
		ret = idr_alloc(&dev->object_name_idr, obj, 1, 0, GFP_KERNEL);
		if (ret < 0)
			goto err;

		obj->name = ret;
	}

	args->name = (uint64_t) obj->name;
	ret = 0;

err:
	mutex_unlock(&dev->object_name_lock);
	drm_gem_object_put(obj);
	return ret;
}

/**
 * drm_gem_open_ioctl - implementation of the GEM_OPEN ioctl
 * @dev: drm_device
 * @data: ioctl data
 * @file_priv: drm file-private structure
 *
 * Open an object using the global name, returning a handle and the size.
 *
 * This handle (of course) holds a reference to the object, so the object
 * will not go away until the handle is deleted.
 */
int
drm_gem_open_ioctl(struct drm_device *dev, void *data,
		   struct drm_file *file_priv)
{
	struct drm_gem_open *args = data;
	struct drm_gem_object *obj;
	int ret;
	u32 handle;

	if (!drm_core_check_feature(dev, DRIVER_GEM))
		return -EOPNOTSUPP;

	mutex_lock(&dev->object_name_lock);
	obj = idr_find(&dev->object_name_idr, (int) args->name);
	if (obj) {
		drm_gem_object_get(obj);
	} else {
		mutex_unlock(&dev->object_name_lock);
		return -ENOENT;
	}

	/* drm_gem_handle_create_tail unlocks dev->object_name_lock. */
	ret = drm_gem_handle_create_tail(file_priv, obj, &handle);
	if (ret)
		goto err;

	args->handle = handle;
	args->size = obj->size;

err:
	drm_gem_object_put(obj);
	return ret;
}

/**
 * drm_gem_open - initializes GEM file-private structures at devnode open time
 * @dev: drm_device which is being opened by userspace
 * @file_private: drm file-private structure to set up
 *
 * Called at device open time, sets up the structure for handling refcounting
 * of mm objects.
 */
void
drm_gem_open(struct drm_device *dev, struct drm_file *file_private)
{
	idr_init_base(&file_private->object_idr, 1);
	spin_lock_init(&file_private->table_lock);
}

/**
 * drm_gem_release - release file-private GEM resources
 * @dev: drm_device which is being closed by userspace
 * @file_private: drm file-private structure to clean up
 *
 * Called at close time when the filp is going away.
 *
 * Releases any remaining references on objects by this filp.
 */
void
drm_gem_release(struct drm_device *dev, struct drm_file *file_private)
{
	idr_for_each(&file_private->object_idr,
		     &drm_gem_object_release_handle, file_private);
	idr_destroy(&file_private->object_idr);
}

/**
 * drm_gem_object_release - release GEM buffer object resources
 * @obj: GEM buffer object
 *
 * This releases any structures and resources used by @obj and is the inverse of
 * drm_gem_object_init().
 */
void
drm_gem_object_release(struct drm_gem_object *obj)
{
	if (obj->filp)
		fput(obj->filp);

	drm_gem_private_object_fini(obj);

	drm_gem_free_mmap_offset(obj);
	drm_gem_lru_remove(obj);
}
EXPORT_SYMBOL(drm_gem_object_release);

/**
 * drm_gem_object_free - free a GEM object
 * @kref: kref of the object to free
 *
 * Called after the last reference to the object has been lost.
 *
 * Frees the object
 */
void
drm_gem_object_free(struct kref *kref)
{
	struct drm_gem_object *obj =
		container_of(kref, struct drm_gem_object, refcount);

	if (WARN_ON(!obj->funcs->free))
		return;

	obj->funcs->free(obj);
}
EXPORT_SYMBOL(drm_gem_object_free);

/**
 * drm_gem_vm_open - vma->ops->open implementation for GEM
 * @vma: VM area structure
 *
 * This function implements the #vm_operations_struct open() callback for GEM
 * drivers. This must be used together with drm_gem_vm_close().
 */
void drm_gem_vm_open(struct vm_area_struct *vma)
{
	struct drm_gem_object *obj = vma->vm_private_data;

	drm_gem_object_get(obj);
}
EXPORT_SYMBOL(drm_gem_vm_open);

/**
 * drm_gem_vm_close - vma->ops->close implementation for GEM
 * @vma: VM area structure
 *
 * This function implements the #vm_operations_struct close() callback for GEM
 * drivers. This must be used together with drm_gem_vm_open().
 */
void drm_gem_vm_close(struct vm_area_struct *vma)
{
	struct drm_gem_object *obj = vma->vm_private_data;

	drm_gem_object_put(obj);
}
EXPORT_SYMBOL(drm_gem_vm_close);

/**
 * drm_gem_mmap_obj - memory map a GEM object
 * @obj: the GEM object to map
 * @obj_size: the object size to be mapped, in bytes
 * @vma: VMA for the area to be mapped
 *
 * Set up the VMA to prepare mapping of the GEM object using the GEM object's
 * vm_ops. Depending on their requirements, GEM objects can either
 * provide a fault handler in their vm_ops (in which case any accesses to
 * the object will be trapped, to perform migration, GTT binding, surface
 * register allocation, or performance monitoring), or mmap the buffer memory
 * synchronously after calling drm_gem_mmap_obj.
 *
 * This function is mainly intended to implement the DMABUF mmap operation, when
 * the GEM object is not looked up based on its fake offset. To implement the
 * DRM mmap operation, drivers should use the drm_gem_mmap() function.
 *
 * drm_gem_mmap_obj() assumes the user is granted access to the buffer while
 * drm_gem_mmap() prevents unprivileged users from mapping random objects. So
 * callers must verify access restrictions before calling this helper.
 *
 * Return 0 or success or -EINVAL if the object size is smaller than the VMA
 * size, or if no vm_ops are provided.
 */
int drm_gem_mmap_obj(struct drm_gem_object *obj, unsigned long obj_size,
		     struct vm_area_struct *vma)
{
	int ret;

	/* Check for valid size. */
	if (obj_size < vma->vm_end - vma->vm_start)
		return -EINVAL;

	/* Take a ref for this mapping of the object, so that the fault
	 * handler can dereference the mmap offset's pointer to the object.
	 * This reference is cleaned up by the corresponding vm_close
	 * (which should happen whether the vma was created by this call, or
	 * by a vm_open due to mremap or partial unmap or whatever).
	 */
	drm_gem_object_get(obj);

	vma->vm_private_data = obj;
	vma->vm_ops = obj->funcs->vm_ops;

	if (obj->funcs->mmap) {
		ret = obj->funcs->mmap(obj, vma);
		if (ret)
			goto err_drm_gem_object_put;
		WARN_ON(!(vma->vm_flags & VM_DONTEXPAND));
	} else {
		if (!vma->vm_ops) {
			ret = -EINVAL;
			goto err_drm_gem_object_put;
		}

		vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
		vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
		vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
	}

	return 0;

err_drm_gem_object_put:
	drm_gem_object_put(obj);
	return ret;
}
EXPORT_SYMBOL(drm_gem_mmap_obj);

/**
 * drm_gem_mmap - memory map routine for GEM objects
 * @filp: DRM file pointer
 * @vma: VMA for the area to be mapped
 *
 * If a driver supports GEM object mapping, mmap calls on the DRM file
 * descriptor will end up here.
 *
 * Look up the GEM object based on the offset passed in (vma->vm_pgoff will
 * contain the fake offset we created when the GTT map ioctl was called on
 * the object) and map it with a call to drm_gem_mmap_obj().
 *
 * If the caller is not granted access to the buffer object, the mmap will fail
 * with EACCES. Please see the vma manager for more information.
 */
int drm_gem_mmap(struct file *filp, struct vm_area_struct *vma)
{
	struct drm_file *priv = filp->private_data;
	struct drm_device *dev = priv->minor->dev;
	struct drm_gem_object *obj = NULL;
	struct drm_vma_offset_node *node;
	int ret;

	if (drm_dev_is_unplugged(dev))
		return -ENODEV;

	drm_vma_offset_lock_lookup(dev->vma_offset_manager);
	node = drm_vma_offset_exact_lookup_locked(dev->vma_offset_manager,
						  vma->vm_pgoff,
						  vma_pages(vma));
	if (likely(node)) {
		obj = container_of(node, struct drm_gem_object, vma_node);
		/*
		 * When the object is being freed, after it hits 0-refcnt it
		 * proceeds to tear down the object. In the process it will
		 * attempt to remove the VMA offset and so acquire this
		 * mgr->vm_lock.  Therefore if we find an object with a 0-refcnt
		 * that matches our range, we know it is in the process of being
		 * destroyed and will be freed as soon as we release the lock -
		 * so we have to check for the 0-refcnted object and treat it as
		 * invalid.
		 */
		if (!kref_get_unless_zero(&obj->refcount))
			obj = NULL;
	}
	drm_vma_offset_unlock_lookup(dev->vma_offset_manager);

	if (!obj)
		return -EINVAL;

	if (!drm_vma_node_is_allowed(node, priv)) {
		drm_gem_object_put(obj);
		return -EACCES;
	}

	ret = drm_gem_mmap_obj(obj, drm_vma_node_size(node) << PAGE_SHIFT,
			       vma);

	drm_gem_object_put(obj);

	return ret;
}
EXPORT_SYMBOL(drm_gem_mmap);

void drm_gem_print_info(struct drm_printer *p, unsigned int indent,
			const struct drm_gem_object *obj)
{
	drm_printf_indent(p, indent, "name=%d\n", obj->name);
	drm_printf_indent(p, indent, "refcount=%u\n",
			  kref_read(&obj->refcount));
	drm_printf_indent(p, indent, "start=%08lx\n",
			  drm_vma_node_start(&obj->vma_node));
	drm_printf_indent(p, indent, "size=%zu\n", obj->size);
	drm_printf_indent(p, indent, "imported=%s\n",
			  str_yes_no(obj->import_attach));

	if (obj->funcs->print_info)
		obj->funcs->print_info(p, indent, obj);
}

int drm_gem_pin(struct drm_gem_object *obj)
{
	if (obj->funcs->pin)
		return obj->funcs->pin(obj);
	else
		return 0;
}

void drm_gem_unpin(struct drm_gem_object *obj)
{
	if (obj->funcs->unpin)
		obj->funcs->unpin(obj);
}

int drm_gem_vmap(struct drm_gem_object *obj, struct iosys_map *map)
{
	int ret;

	dma_resv_assert_held(obj->resv);

	if (!obj->funcs->vmap)
		return -EOPNOTSUPP;

	ret = obj->funcs->vmap(obj, map);
	if (ret)
		return ret;
	else if (iosys_map_is_null(map))
		return -ENOMEM;

	return 0;
}
EXPORT_SYMBOL(drm_gem_vmap);

void drm_gem_vunmap(struct drm_gem_object *obj, struct iosys_map *map)
{
	dma_resv_assert_held(obj->resv);

	if (iosys_map_is_null(map))
		return;

	if (obj->funcs->vunmap)
		obj->funcs->vunmap(obj, map);

	/* Always set the mapping to NULL. Callers may rely on this. */
	iosys_map_clear(map);
}
EXPORT_SYMBOL(drm_gem_vunmap);

int drm_gem_vmap_unlocked(struct drm_gem_object *obj, struct iosys_map *map)
{
	int ret;

	dma_resv_lock(obj->resv, NULL);
	ret = drm_gem_vmap(obj, map);
	dma_resv_unlock(obj->resv);

	return ret;
}
EXPORT_SYMBOL(drm_gem_vmap_unlocked);

void drm_gem_vunmap_unlocked(struct drm_gem_object *obj, struct iosys_map *map)
{
	dma_resv_lock(obj->resv, NULL);
	drm_gem_vunmap(obj, map);
	dma_resv_unlock(obj->resv);
}
EXPORT_SYMBOL(drm_gem_vunmap_unlocked);

/**
 * drm_gem_lock_reservations - Sets up the ww context and acquires
 * the lock on an array of GEM objects.
 *
 * Once you've locked your reservations, you'll want to set up space
 * for your shared fences (if applicable), submit your job, then
 * drm_gem_unlock_reservations().
 *
 * @objs: drm_gem_objects to lock
 * @count: Number of objects in @objs
 * @acquire_ctx: struct ww_acquire_ctx that will be initialized as
 * part of tracking this set of locked reservations.
 */
int
drm_gem_lock_reservations(struct drm_gem_object **objs, int count,
			  struct ww_acquire_ctx *acquire_ctx)
{
	int contended = -1;
	int i, ret;

	ww_acquire_init(acquire_ctx, &reservation_ww_class);

retry:
	if (contended != -1) {
		struct drm_gem_object *obj = objs[contended];

		ret = dma_resv_lock_slow_interruptible(obj->resv,
								 acquire_ctx);
		if (ret) {
			ww_acquire_fini(acquire_ctx);
			return ret;
		}
	}

	for (i = 0; i < count; i++) {
		if (i == contended)
			continue;

		ret = dma_resv_lock_interruptible(objs[i]->resv,
							    acquire_ctx);
		if (ret) {
			int j;

			for (j = 0; j < i; j++)
				dma_resv_unlock(objs[j]->resv);

			if (contended != -1 && contended >= i)
				dma_resv_unlock(objs[contended]->resv);

			if (ret == -EDEADLK) {
				contended = i;
				goto retry;
			}

			ww_acquire_fini(acquire_ctx);
			return ret;
		}
	}

	ww_acquire_done(acquire_ctx);

	return 0;
}
EXPORT_SYMBOL(drm_gem_lock_reservations);

void
drm_gem_unlock_reservations(struct drm_gem_object **objs, int count,
			    struct ww_acquire_ctx *acquire_ctx)
{
	int i;

	for (i = 0; i < count; i++)
		dma_resv_unlock(objs[i]->resv);

	ww_acquire_fini(acquire_ctx);
}
EXPORT_SYMBOL(drm_gem_unlock_reservations);

/**
 * drm_gem_lru_init - initialize a LRU
 *
 * @lru: The LRU to initialize
 * @lock: The lock protecting the LRU
 */
void
drm_gem_lru_init(struct drm_gem_lru *lru, struct mutex *lock)
{
	lru->lock = lock;
	lru->count = 0;
	INIT_LIST_HEAD(&lru->list);
}
EXPORT_SYMBOL(drm_gem_lru_init);

static void
drm_gem_lru_remove_locked(struct drm_gem_object *obj)
{
	obj->lru->count -= obj->size >> PAGE_SHIFT;
	WARN_ON(obj->lru->count < 0);
	list_del(&obj->lru_node);
	obj->lru = NULL;
}

/**
 * drm_gem_lru_remove - remove object from whatever LRU it is in
 *
 * If the object is currently in any LRU, remove it.
 *
 * @obj: The GEM object to remove from current LRU
 */
void
drm_gem_lru_remove(struct drm_gem_object *obj)
{
	struct drm_gem_lru *lru = obj->lru;

	if (!lru)
		return;

	mutex_lock(lru->lock);
	drm_gem_lru_remove_locked(obj);
	mutex_unlock(lru->lock);
}
EXPORT_SYMBOL(drm_gem_lru_remove);

static void
drm_gem_lru_move_tail_locked(struct drm_gem_lru *lru, struct drm_gem_object *obj)
{
	lockdep_assert_held_once(lru->lock);

	if (obj->lru)
		drm_gem_lru_remove_locked(obj);

	lru->count += obj->size >> PAGE_SHIFT;
	list_add_tail(&obj->lru_node, &lru->list);
	obj->lru = lru;
}

/**
 * drm_gem_lru_move_tail - move the object to the tail of the LRU
 *
 * If the object is already in this LRU it will be moved to the
 * tail.  Otherwise it will be removed from whichever other LRU
 * it is in (if any) and moved into this LRU.
 *
 * @lru: The LRU to move the object into.
 * @obj: The GEM object to move into this LRU
 */
void
drm_gem_lru_move_tail(struct drm_gem_lru *lru, struct drm_gem_object *obj)
{
	mutex_lock(lru->lock);
	drm_gem_lru_move_tail_locked(lru, obj);
	mutex_unlock(lru->lock);
}
EXPORT_SYMBOL(drm_gem_lru_move_tail);

/**
 * drm_gem_lru_scan - helper to implement shrinker.scan_objects
 *
 * If the shrink callback succeeds, it is expected that the driver
 * move the object out of this LRU.
 *
 * If the LRU possibly contain active buffers, it is the responsibility
 * of the shrink callback to check for this (ie. dma_resv_test_signaled())
 * or if necessary block until the buffer becomes idle.
 *
 * @lru: The LRU to scan
 * @nr_to_scan: The number of pages to try to reclaim
 * @shrink: Callback to try to shrink/reclaim the object.
 */
unsigned long
drm_gem_lru_scan(struct drm_gem_lru *lru, unsigned nr_to_scan,
		 bool (*shrink)(struct drm_gem_object *obj))
{
	struct drm_gem_lru still_in_lru;
	struct drm_gem_object *obj;
	unsigned freed = 0;

	drm_gem_lru_init(&still_in_lru, lru->lock);

	mutex_lock(lru->lock);

	while (freed < nr_to_scan) {
		obj = list_first_entry_or_null(&lru->list, typeof(*obj), lru_node);

		if (!obj)
			break;

		drm_gem_lru_move_tail_locked(&still_in_lru, obj);

		/*
		 * If it's in the process of being freed, gem_object->free()
		 * may be blocked on lock waiting to remove it.  So just
		 * skip it.
		 */
		if (!kref_get_unless_zero(&obj->refcount))
			continue;

		/*
		 * Now that we own a reference, we can drop the lock for the
		 * rest of the loop body, to reduce contention with other
		 * code paths that need the LRU lock
		 */
		mutex_unlock(lru->lock);

		/*
		 * Note that this still needs to be trylock, since we can
		 * hit shrinker in response to trying to get backing pages
		 * for this obj (ie. while it's lock is already held)
		 */
		if (!dma_resv_trylock(obj->resv))
			goto tail;

		if (shrink(obj)) {
			freed += obj->size >> PAGE_SHIFT;

			/*
			 * If we succeeded in releasing the object's backing
			 * pages, we expect the driver to have moved the object
			 * out of this LRU
			 */
			WARN_ON(obj->lru == &still_in_lru);
			WARN_ON(obj->lru == lru);
		}

		dma_resv_unlock(obj->resv);

tail:
		drm_gem_object_put(obj);
		mutex_lock(lru->lock);
	}

	/*
	 * Move objects we've skipped over out of the temporary still_in_lru
	 * back into this LRU
	 */
	list_for_each_entry (obj, &still_in_lru.list, lru_node)
		obj->lru = lru;
	list_splice_tail(&still_in_lru.list, &lru->list);
	lru->count += still_in_lru.count;

	mutex_unlock(lru->lock);

	return freed;
}
EXPORT_SYMBOL(drm_gem_lru_scan);