summaryrefslogtreecommitdiffstats
path: root/src/H5Dio.c
blob: 24c7be9ca65edd2986fbbf95744ff8b3ab3b7866 (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
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * Copyright by The HDF Group.                                               *
 * All rights reserved.                                                      *
 *                                                                           *
 * This file is part of HDF5.  The full HDF5 copyright notice, including     *
 * terms governing use, modification, and redistribution, is contained in    *
 * the COPYING file, which can be found at the root of the source code       *
 * distribution tree, or in https://www.hdfgroup.org/licenses.               *
 * If you do not have access to either file, you may request a copy from     *
 * help@hdfgroup.org.                                                        *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

/****************/
/* Module Setup */
/****************/

#include "H5Dmodule.h" /* This source code file is part of the H5D module */

/***********/
/* Headers */
/***********/
#include "H5private.h"   /* Generic Functions                        */
#include "H5CXprivate.h" /* API Contexts                             */
#include "H5Dpkg.h"      /* Dataset functions                        */
#include "H5Eprivate.h"  /* Error handling                           */
#include "H5FLprivate.h" /* Free Lists                               */
#include "H5Iprivate.h"  /* IDs                                      */
#include "H5MMprivate.h" /* Memory management                        */
#include "H5Sprivate.h"  /* Dataspace                                */

#include "H5VLnative_private.h" /* Native VOL connector                     */

/****************/
/* Local Macros */
/****************/

/******************/
/* Local Typedefs */
/******************/

/********************/
/* Local Prototypes */
/********************/

/* Setup/teardown routines */
static herr_t H5D__ioinfo_init(size_t count, H5D_io_op_type_t op_type, H5D_dset_io_info_t *dset_info,
                               H5D_io_info_t *io_info);
static herr_t H5D__dset_ioinfo_init(H5D_t *dset, H5D_dset_io_info_t *dset_info, H5D_storage_t *store);
static herr_t H5D__typeinfo_init(H5D_io_info_t *io_info, H5D_dset_io_info_t *dset_info, hid_t mem_type_id);
static herr_t H5D__typeinfo_init_phase2(H5D_io_info_t *io_info);
static herr_t H5D__typeinfo_init_phase3(H5D_io_info_t *io_info);
#ifdef H5_HAVE_PARALLEL
static herr_t H5D__ioinfo_adjust(H5D_io_info_t *io_info);
#endif /* H5_HAVE_PARALLEL */
static herr_t H5D__typeinfo_term(H5D_io_info_t *io_info);

/*********************/
/* Package Variables */
/*********************/

/*******************/
/* Local Variables */
/*******************/

/* Declare a free list to manage blocks of type conversion data */
H5FL_BLK_DEFINE(type_conv);

/*-------------------------------------------------------------------------
 * Function:	H5D__read
 *
 * Purpose:	Reads multiple (parts of) DATASETs into application memory BUFs.
 *              See H5Dread_multi() for complete details.
 *
 * Return:	Non-negative on success/Negative on failure
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5D__read(size_t count, H5D_dset_io_info_t *dset_info)
{
    H5D_io_info_t io_info;                    /* Dataset I/O info  for multi dsets */
    H5S_t        *orig_mem_space_local;       /* Local buffer for orig_mem_space */
    H5S_t       **orig_mem_space = NULL;      /* If not NULL, ptr to an array of dataspaces       */
                                              /* containing the original memory spaces contained  */
                                              /* in dset_info.  This is needed in order to        */
                                              /* restore the original state of  dset_info if we   */
                                              /* replaced any mem spaces with equivalents         */
                                              /* projected to a rank equal to that of file_space. */
                                              /*                                                  */
                                              /* This field is only used if                       */
                                              /* H5S_select_shape_same() returns TRUE when        */
                                              /* comparing at least one mem_space and data_space, */
                                              /* and the mem_space has a different rank.          */
                                              /*                                                  */
                                              /* Note that this is a temporary variable - the     */
                                              /* projected memory space is stored in dset_info,   */
                                              /* and will be freed when that structure is         */
                                              /* freed. */
    H5D_storage_t  store_local;               /* Local buffer for store */
    H5D_storage_t *store      = &store_local; /* Union of EFL and chunk pointer in file space */
    size_t         io_op_init = 0;            /* Number I/O ops that have been initialized */
    size_t         io_skipped =
        0;            /* Number I/O ops that have been skipped (due to the dataset not being allocated) */
    size_t i;         /* Local index variable */
    char   fake_char; /* Temporary variable for NULL buffer pointers */
    herr_t ret_value = SUCCEED; /* Return value	*/

    FUNC_ENTER_NOAPI(FAIL)

    /* Init io_info */
    if (H5D__ioinfo_init(count, H5D_IO_OP_READ, dset_info, &io_info) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "can't initialize I/O info")

    /* Allocate store buffer if necessary */
    if (count > 1)
        if (NULL == (store = (H5D_storage_t *)H5MM_malloc(count * sizeof(H5D_storage_t))))
            HGOTO_ERROR(H5E_DATASET, H5E_CANTALLOC, FAIL, "couldn't allocate dset storage info array buffer")

#ifdef H5_HAVE_PARALLEL
    /* Check for non-MPI-based VFD.  Only need to check first dataset since all
     * share the same file. */
    if (!(H5F_HAS_FEATURE(dset_info[0].dset->oloc.file, H5FD_FEAT_HAS_MPI))) {
        H5FD_mpio_xfer_t io_xfer_mode; /* MPI I/O transfer mode */

        /* Get I/O transfer mode */
        if (H5CX_get_io_xfer_mode(&io_xfer_mode) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't get MPI-I/O transfer mode")

        /* Collective access is not permissible without a MPI based VFD */
        if (io_xfer_mode == H5FD_MPIO_COLLECTIVE)
            HGOTO_ERROR(H5E_DATASET, H5E_UNSUPPORTED, FAIL, "collective access for MPI-based drivers only")
    }  /* end if */
#endif /*H5_HAVE_PARALLEL*/

    /* iterate over all dsets and construct I/O information necessary to do I/O */
    for (i = 0; i < count; i++) {
        haddr_t prev_tag = HADDR_UNDEF;

        /* check args */
        if (NULL == dset_info[i].dset)
            HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a dataset")
        if (NULL == dset_info[i].dset->oloc.file)
            HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a file")

        /* set metadata tagging with dset oheader addr */
        H5AC_tag(dset_info[i].dset->oloc.addr, &prev_tag);

        /* Set up datatype info for operation */
        if (H5D__typeinfo_init(&io_info, &(dset_info[i]), dset_info[i].mem_type_id) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to set up type info")

        /* Make certain that the number of elements in each selection is the same, and cache nelmts in
         * dset_info */
        dset_info[i].nelmts = H5S_GET_SELECT_NPOINTS(dset_info[i].mem_space);
        if (dset_info[i].nelmts != H5S_GET_SELECT_NPOINTS(dset_info[i].file_space))
            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
                        "src and dest dataspaces have different number of elements selected")

        /* Check for a NULL buffer */
        if (NULL == dset_info[i].buf.vp) {
            /* Check for any elements selected (which is invalid) */
            if (dset_info[i].nelmts > 0)
                HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "no output buffer")

            /* If the buffer is nil, and 0 element is selected, make a fake buffer.
             * This is for some MPI package like ChaMPIon on NCSA's tungsten which
             * doesn't support this feature.
             */
            dset_info[i].buf.vp = &fake_char;
        } /* end if */

        /* Make sure that both selections have their extents set */
        if (!(H5S_has_extent(dset_info[i].file_space)))
            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "file dataspace does not have extent set")
        if (!(H5S_has_extent(dset_info[i].mem_space)))
            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "memory dataspace does not have extent set")

        /* H5S_select_shape_same() has been modified to accept topologically identical
         * selections with different rank as having the same shape (if the most
         * rapidly changing coordinates match up), but the I/O code still has
         * difficulties with the notion.
         *
         * To solve this, we check to see if H5S_select_shape_same() returns true,
         * and if the ranks of the mem and file spaces are different.  If they are,
         * construct a new mem space that is equivalent to the old mem space, and
         * use that instead.
         *
         * Note that in general, this requires us to touch up the memory buffer as
         * well.
         */
        if (dset_info[i].nelmts > 0 &&
            TRUE == H5S_SELECT_SHAPE_SAME(dset_info[i].mem_space, dset_info[i].file_space) &&
            H5S_GET_EXTENT_NDIMS(dset_info[i].mem_space) != H5S_GET_EXTENT_NDIMS(dset_info[i].file_space)) {
            ptrdiff_t buf_adj = 0;

            /* Allocate original memory space buffer if necessary */
            if (!orig_mem_space) {
                if (count > 1) {
                    /* Allocate buffer */
                    if (NULL == (orig_mem_space = (H5S_t **)H5MM_calloc(count * sizeof(H5S_t *))))
                        HGOTO_ERROR(H5E_DATASET, H5E_CANTALLOC, FAIL,
                                    "couldn't allocate original memory space array buffer")
                }
                else
                    /* Use local buffer */
                    orig_mem_space = &orig_mem_space_local;
            }

            /* Save original memory space */
            orig_mem_space[i]      = dset_info[i].mem_space;
            dset_info[i].mem_space = NULL;

            /* Attempt to construct projected dataspace for memory dataspace */
            if (H5S_select_construct_projection(orig_mem_space[i], &dset_info[i].mem_space,
                                                (unsigned)H5S_GET_EXTENT_NDIMS(dset_info[i].file_space),
                                                (hsize_t)dset_info[i].type_info.dst_type_size, &buf_adj) < 0)
                HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to construct projected memory dataspace")
            assert(dset_info[i].mem_space);

            /* Adjust the buffer by the given amount */
            dset_info[i].buf.vp = (void *)(((uint8_t *)dset_info[i].buf.vp) + buf_adj);
        } /* end if */

        /* If space hasn't been allocated and not using external storage,
         * return fill value to buffer if fill time is upon allocation, or
         * do nothing if fill time is never.  If the dataset is compact and
         * fill time is NEVER, there is no way to tell whether part of data
         * has been overwritten.  So just proceed in reading.
         */
        if (dset_info[i].nelmts > 0 && dset_info[i].dset->shared->dcpl_cache.efl.nused == 0 &&
            !(*dset_info[i].dset->shared->layout.ops->is_space_alloc)(
                &dset_info[i].dset->shared->layout.storage) &&
            !(dset_info[i].dset->shared->layout.ops->is_data_cached &&
              (*dset_info[i].dset->shared->layout.ops->is_data_cached)(dset_info[i].dset->shared))) {
            H5D_fill_value_t fill_status; /* Whether/How the fill value is defined */

            /* Retrieve dataset's fill-value properties */
            if (H5P_is_fill_value_defined(&dset_info[i].dset->shared->dcpl_cache.fill, &fill_status) < 0)
                HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't tell if fill value defined")

            /* Should be impossible, but check anyway... */
            if (fill_status == H5D_FILL_VALUE_UNDEFINED &&
                (dset_info[i].dset->shared->dcpl_cache.fill.fill_time == H5D_FILL_TIME_ALLOC ||
                 dset_info[i].dset->shared->dcpl_cache.fill.fill_time == H5D_FILL_TIME_IFSET))
                HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL,
                            "read failed: dataset doesn't exist, no data can be read")

            /* If we're never going to fill this dataset, just leave the junk in the user's buffer */
            if (dset_info[i].dset->shared->dcpl_cache.fill.fill_time != H5D_FILL_TIME_NEVER)
                /* Go fill the user's selection with the dataset's fill value */
                if (H5D__fill(dset_info[i].dset->shared->dcpl_cache.fill.buf, dset_info[i].dset->shared->type,
                              dset_info[i].buf.vp, dset_info[i].type_info.mem_type,
                              dset_info[i].mem_space) < 0)
                    HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL, "filling buf failed")

            /* No need to perform any more I/O for this dataset */
            dset_info[i].skip_io = TRUE;
            io_skipped++;
        } /* end if */
        else {
            /* Set up I/O operation */
            if (H5D__dset_ioinfo_init(dset_info[i].dset, &(dset_info[i]), &(store[i])) < 0)
                HGOTO_ERROR(H5E_DATASET, H5E_UNSUPPORTED, FAIL, "unable to set up I/O operation")

            /* Sanity check that space is allocated, if there are elements */
            if (dset_info[i].nelmts > 0)
                assert(
                    (*dset_info[i].dset->shared->layout.ops->is_space_alloc)(
                        &dset_info[i].dset->shared->layout.storage) ||
                    (dset_info[i].dset->shared->layout.ops->is_data_cached &&
                     (*dset_info[i].dset->shared->layout.ops->is_data_cached)(dset_info[i].dset->shared)) ||
                    dset_info[i].dset->shared->dcpl_cache.efl.nused > 0 ||
                    dset_info[i].dset->shared->layout.type == H5D_COMPACT);

            /* Call storage method's I/O initialization routine */
            if (dset_info[i].layout_ops.io_init &&
                (dset_info[i].layout_ops.io_init)(&io_info, &(dset_info[i])) < 0)
                HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "can't initialize I/O info")
            dset_info[i].skip_io = FALSE;
            io_op_init++;

            /* Reset metadata tagging */
            H5AC_tag(prev_tag, NULL);
        }
    } /* end of for loop */

    assert(io_op_init + io_skipped == count);

    /* If no datasets have I/O, we're done */
    if (io_op_init == 0)
        HGOTO_DONE(SUCCEED);

    /* Perform second phase of type info initialization */
    if (H5D__typeinfo_init_phase2(&io_info) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to set up type info (second phase)")

#ifdef H5_HAVE_PARALLEL
    /* Adjust I/O info for any parallel or selection I/O */
    if (H5D__ioinfo_adjust(&io_info) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL,
                    "unable to adjust I/O info for parallel or selection I/O")
#endif /* H5_HAVE_PARALLEL */

    /* Perform third phase of type info initialization */
    if (H5D__typeinfo_init_phase3(&io_info) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to set up type info (third phase)")

    H5CX_set_no_selection_io_cause(io_info.no_selection_io_cause);

    /* If multi dataset I/O callback is not provided, perform read IO via
     * single-dset path with looping */
    if (io_info.md_io_ops.multi_read_md) {
        /* Create sel_pieces array if any pieces are selected */
        if (io_info.piece_count > 0) {
            assert(!io_info.sel_pieces);
            assert(io_info.pieces_added == 0);

            /* Allocate sel_pieces array */
            if (NULL ==
                (io_info.sel_pieces = H5MM_malloc(io_info.piece_count * sizeof(io_info.sel_pieces[0]))))
                HGOTO_ERROR(H5E_DATASET, H5E_CANTALLOC, FAIL, "unable to allocate array of selected pieces")
        }

        /* MDIO-specific second phase initialization */
        for (i = 0; i < count; i++)
            if (dset_info[i].layout_ops.mdio_init) {
                haddr_t prev_tag = HADDR_UNDEF;

                /* set metadata tagging with dset oheader addr */
                H5AC_tag(dset_info[i].dset->oloc.addr, &prev_tag);

                /* Make second phase IO init call */
                if ((dset_info[i].layout_ops.mdio_init)(&io_info, &(dset_info[i])) < 0)
                    HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "can't populate array of selected pieces")

                /* Reset metadata tagging */
                H5AC_tag(prev_tag, NULL);
            }

        /* Invoke correct "high level" I/O routine */
        if ((*io_info.md_io_ops.multi_read_md)(&io_info) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL, "can't read data")
    } /* end if */
    else {
        haddr_t prev_tag = HADDR_UNDEF;

        /* Allocate selection I/O parameter arrays if necessary */
        if (!H5D_LAYOUT_CB_PERFORM_IO(&io_info) && io_info.piece_count > 0) {
            if (NULL == (io_info.mem_spaces = H5MM_malloc(io_info.piece_count * sizeof(H5S_t *))))
                HGOTO_ERROR(H5E_RESOURCE, H5E_CANTALLOC, FAIL,
                            "memory allocation failed for memory space list")
            if (NULL == (io_info.file_spaces = H5MM_malloc(io_info.piece_count * sizeof(H5S_t *))))
                HGOTO_ERROR(H5E_RESOURCE, H5E_CANTALLOC, FAIL, "memory allocation failed for file space list")
            if (NULL == (io_info.addrs = H5MM_malloc(io_info.piece_count * sizeof(haddr_t))))
                HGOTO_ERROR(H5E_RESOURCE, H5E_CANTALLOC, FAIL,
                            "memory allocation failed for piece address list")
            if (NULL == (io_info.element_sizes = H5MM_malloc(io_info.piece_count * sizeof(size_t))))
                HGOTO_ERROR(H5E_RESOURCE, H5E_CANTALLOC, FAIL,
                            "memory allocation failed for element size list")
            if (NULL == (io_info.rbufs = H5MM_malloc(io_info.piece_count * sizeof(void *))))
                HGOTO_ERROR(H5E_RESOURCE, H5E_CANTALLOC, FAIL,
                            "memory allocation failed for read buffer list")
            if (io_info.max_tconv_type_size > 0)
                if (NULL ==
                    (io_info.sel_pieces = H5MM_malloc(io_info.piece_count * sizeof(io_info.sel_pieces[0]))))
                    HGOTO_ERROR(H5E_RESOURCE, H5E_CANTALLOC, FAIL,
                                "unable to allocate array of selected pieces")
        }

        /* Loop with serial & single-dset read IO path */
        for (i = 0; i < count; i++) {
            /* Check for skipped I/O */
            if (dset_info[i].skip_io)
                continue;

            /* set metadata tagging with dset oheader addr */
            H5AC_tag(dset_info[i].dset->oloc.addr, &prev_tag);

            /* Invoke correct "high level" I/O routine */
            if ((*dset_info[i].io_ops.multi_read)(&io_info, &dset_info[i]) < 0)
                HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL, "can't read data")

            /* Reset metadata tagging */
            H5AC_tag(prev_tag, NULL);
        }

        /* Make final selection I/O call if the multi_read callbacks did not perform the actual I/O
         * (if using selection I/O and either multi dataset or type conversion) */
        if (!H5D_LAYOUT_CB_PERFORM_IO(&io_info)) {
            /* Check for type conversion */
            if (io_info.max_tconv_type_size > 0) {
                /* Type conversion pathway */
                if (H5D__scatgath_read_select(&io_info) < 0)
                    HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL, "type conversion selection read failed")
            }
            else {
                /* Call selection I/O directly */
                H5_CHECK_OVERFLOW(io_info.pieces_added, size_t, uint32_t);
                if (H5F_shared_select_read(io_info.f_sh, H5FD_MEM_DRAW, (uint32_t)io_info.pieces_added,
                                           io_info.mem_spaces, io_info.file_spaces, io_info.addrs,
                                           io_info.element_sizes, io_info.rbufs) < 0)
                    HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL, "selection read failed")
            }
        }

#ifdef H5_HAVE_PARALLEL
        /* Report the actual I/O mode to the application if appropriate */
        if (io_info.using_mpi_vfd) {
            H5FD_mpio_xfer_t xfer_mode; /* Parallel transfer for this request */

            /* Get the parallel I/O transfer mode */
            if (H5CX_get_io_xfer_mode(&xfer_mode) < 0)
                HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't get MPI-I/O transfer mode")

            /* Only report the collective I/O mode if we're actually performing collective I/O */
            if (xfer_mode == H5FD_MPIO_COLLECTIVE)
                H5CX_set_mpio_actual_io_mode(io_info.actual_io_mode);
        }
#endif /* H5_HAVE_PARALLEL */
    }

done:
    /* Shut down the I/O op information */
    for (i = 0; i < io_op_init; i++)
        if (!dset_info[i].skip_io && dset_info[i].layout_ops.io_term &&
            (*dset_info[i].layout_ops.io_term)(&io_info, &(dset_info[i])) < 0)
            HDONE_ERROR(H5E_DATASET, H5E_CANTCLOSEOBJ, FAIL, "unable to shut down I/O op info");

    /* Shut down datatype info for operation */
    if (H5D__typeinfo_term(&io_info) < 0)
        HDONE_ERROR(H5E_DATASET, H5E_CANTCLOSEOBJ, FAIL, "unable to shut down type info");

    /* Discard projected mem spaces and restore originals */
    if (orig_mem_space) {
        for (i = 0; i < count; i++)
            if (orig_mem_space[i]) {
                if (H5S_close(dset_info[i].mem_space) < 0)
                    HDONE_ERROR(H5E_DATASET, H5E_CANTCLOSEOBJ, FAIL,
                                "unable to shut down projected memory dataspace");
                dset_info[i].mem_space = orig_mem_space[i];
            }

        /* Free orig_mem_space array if it was allocated */
        if (orig_mem_space != &orig_mem_space_local)
            H5MM_free(orig_mem_space);
    }

    /* Free global piece array */
    H5MM_xfree(io_info.sel_pieces);

    /* Free selection I/O arrays */
    H5MM_xfree(io_info.mem_spaces);
    H5MM_xfree(io_info.file_spaces);
    H5MM_xfree(io_info.addrs);
    H5MM_xfree(io_info.element_sizes);
    H5MM_xfree(io_info.rbufs);

    /* Free store array if it was allocated */
    if (store != &store_local)
        H5MM_free(store);

    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5D__read() */

/*-------------------------------------------------------------------------
 * Function:	H5D__write
 *
 * Purpose:	Writes multiple (part of) DATASETs to a file from application
 *          memory BUFs. See H5Dwrite_multi() for complete details.
 *
 *          This was referred from H5D__write for multi-dset work.
 *
 * Return:	Non-negative on success/Negative on failure
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5D__write(size_t count, H5D_dset_io_info_t *dset_info)
{
    H5D_io_info_t io_info;                    /* Dataset I/O info for multi dsets */
    H5S_t        *orig_mem_space_local;       /* Local buffer for orig_mem_space */
    H5S_t       **orig_mem_space = NULL;      /* If not NULL, ptr to an array of dataspaces       */
                                              /* containing the original memory spaces contained  */
                                              /* in dset_info.  This is needed in order to        */
                                              /* restore the original state of  dset_info if we   */
                                              /* replaced any mem spaces with equivalents         */
                                              /* projected to a rank equal to that of file_space. */
                                              /*                                                  */
                                              /* This field is only used if                       */
                                              /* H5S_select_shape_same() returns TRUE when        */
                                              /* comparing at least one mem_space and data_space, */
                                              /* and the mem_space has a different rank.          */
                                              /*                                                  */
                                              /* Note that this is a temporary variable - the     */
                                              /* projected memory space is stored in dset_info,   */
                                              /* and will be freed when that structure is         */
                                              /* freed. */
    H5D_storage_t  store_local;               /* Local buffer for store */
    H5D_storage_t *store      = &store_local; /* Union of EFL and chunk pointer in file space */
    size_t         io_op_init = 0;            /* Number I/O ops that have been initialized */
    size_t         i;                         /* Local index variable */
    char           fake_char;                 /* Temporary variable for NULL buffer pointers */
    herr_t         ret_value = SUCCEED;       /* Return value	*/

    FUNC_ENTER_NOAPI(FAIL)

    /* Init io_info */
    if (H5D__ioinfo_init(count, H5D_IO_OP_WRITE, dset_info, &io_info) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "can't initialize I/O info")

    /* Allocate store buffer if necessary */
    if (count > 1)
        if (NULL == (store = (H5D_storage_t *)H5MM_malloc(count * sizeof(H5D_storage_t))))
            HGOTO_ERROR(H5E_DATASET, H5E_CANTALLOC, FAIL, "couldn't allocate dset storage info array buffer")

    /* iterate over all dsets and construct I/O information */
    for (i = 0; i < count; i++) {
        hbool_t should_alloc_space = FALSE; /* Whether or not to initialize dataset's storage */
        haddr_t prev_tag           = HADDR_UNDEF;

        /* check args */
        if (NULL == dset_info[i].dset)
            HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a dataset")
        if (NULL == dset_info[i].dset->oloc.file)
            HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a file")

        /* set metadata tagging with dset oheader addr */
        H5AC_tag(dset_info[i].dset->oloc.addr, &prev_tag);

        /* All filters in the DCPL must have encoding enabled. */
        if (!dset_info[i].dset->shared->checked_filters) {
            if (H5Z_can_apply(dset_info[i].dset->shared->dcpl_id, dset_info[i].dset->shared->type_id) < 0)
                HGOTO_ERROR(H5E_PLINE, H5E_CANAPPLY, FAIL, "can't apply filters")

            dset_info[i].dset->shared->checked_filters = TRUE;
        } /* end if */

        /* Check if we are allowed to write to this file */
        if (0 == (H5F_INTENT(dset_info[i].dset->oloc.file) & H5F_ACC_RDWR))
            HGOTO_ERROR(H5E_DATASET, H5E_WRITEERROR, FAIL, "no write intent on file")

        /* Set up datatype info for operation */
        if (H5D__typeinfo_init(&io_info, &(dset_info[i]), dset_info[i].mem_type_id) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to set up type info")

            /* Various MPI based checks */
#ifdef H5_HAVE_PARALLEL
        if (H5F_HAS_FEATURE(dset_info[i].dset->oloc.file, H5FD_FEAT_HAS_MPI)) {
            /* If MPI based VFD is used, no VL or region reference datatype support yet. */
            /* This is because they use the global heap in the file and we don't */
            /* support parallel access of that yet */
            if (H5T_is_vl_storage(dset_info[i].type_info.mem_type) > 0)
                HGOTO_ERROR(H5E_DATASET, H5E_UNSUPPORTED, FAIL,
                            "Parallel IO does not support writing VL or region reference datatypes yet")
        } /* end if */
        else {
            H5FD_mpio_xfer_t io_xfer_mode; /* MPI I/O transfer mode */

            /* Get I/O transfer mode */
            if (H5CX_get_io_xfer_mode(&io_xfer_mode) < 0)
                HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't get MPI-I/O transfer mode")

            /* Collective access is not permissible without a MPI based VFD */
            if (io_xfer_mode == H5FD_MPIO_COLLECTIVE)
                HGOTO_ERROR(H5E_DATASET, H5E_UNSUPPORTED, FAIL, "collective access for MPI-based driver only")
        } /* end else */
#endif    /*H5_HAVE_PARALLEL*/

        /* Make certain that the number of elements in each selection is the same, and cache nelmts in
         * dset_info */
        dset_info[i].nelmts = H5S_GET_SELECT_NPOINTS(dset_info[i].mem_space);
        if (dset_info[i].nelmts != H5S_GET_SELECT_NPOINTS(dset_info[i].file_space))
            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
                        "src and dest dataspaces have different number of elements selected")

        /* Check for a NULL buffer */
        if (NULL == dset_info[i].buf.cvp) {
            /* Check for any elements selected (which is invalid) */
            if (dset_info[i].nelmts > 0)
                HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "no output buffer")

            /* If the buffer is nil, and 0 element is selected, make a fake buffer.
             * This is for some MPI package like ChaMPIon on NCSA's tungsten which
             * doesn't support this feature.
             */
            dset_info[i].buf.cvp = &fake_char;
        } /* end if */

        /* Make sure that both selections have their extents set */
        if (!(H5S_has_extent(dset_info[i].file_space)))
            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "file dataspace does not have extent set")
        if (!(H5S_has_extent(dset_info[i].mem_space)))
            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "memory dataspace does not have extent set")

        /* H5S_select_shape_same() has been modified to accept topologically
         * identical selections with different rank as having the same shape
         * (if the most rapidly changing coordinates match up), but the I/O
         * code still has difficulties with the notion.
         *
         * To solve this, we check to see if H5S_select_shape_same() returns
         * true, and if the ranks of the mem and file spaces are different.
         * If they are, construct a new mem space that is equivalent to the
         * old mem space, and use that instead.
         *
         * Note that in general, this requires us to touch up the memory buffer
         * as well.
         */
        if (dset_info[i].nelmts > 0 &&
            TRUE == H5S_SELECT_SHAPE_SAME(dset_info[i].mem_space, dset_info[i].file_space) &&
            H5S_GET_EXTENT_NDIMS(dset_info[i].mem_space) != H5S_GET_EXTENT_NDIMS(dset_info[i].file_space)) {
            ptrdiff_t buf_adj = 0;

            /* Allocate original memory space buffer if necessary */
            if (!orig_mem_space) {
                if (count > 1) {
                    /* Allocate buffer */
                    if (NULL == (orig_mem_space = (H5S_t **)H5MM_calloc(count * sizeof(H5S_t *))))
                        HGOTO_ERROR(H5E_DATASET, H5E_CANTALLOC, FAIL,
                                    "couldn't allocate original memory space array buffer")
                }
                else
                    /* Use local buffer */
                    orig_mem_space = &orig_mem_space_local;
            }

            /* Save original memory space */
            orig_mem_space[i]      = dset_info[i].mem_space;
            dset_info[i].mem_space = NULL;

            /* Attempt to construct projected dataspace for memory dataspace */
            if (H5S_select_construct_projection(orig_mem_space[i], &dset_info[i].mem_space,
                                                (unsigned)H5S_GET_EXTENT_NDIMS(dset_info[i].file_space),
                                                dset_info[i].type_info.src_type_size, &buf_adj) < 0)
                HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to construct projected memory dataspace")
            assert(dset_info[i].mem_space);

            /* Adjust the buffer by the given amount */
            dset_info[i].buf.cvp = (const void *)(((const uint8_t *)dset_info[i].buf.cvp) + buf_adj);
        } /* end if */

        /* Retrieve dataset properties */
        /* <none needed currently> */

        /* Set up I/O operation */
        if (H5D__dset_ioinfo_init(dset_info[i].dset, &(dset_info[i]), &(store[i])) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to set up I/O operation")

        /* Allocate dataspace and initialize it if it hasn't been. */
        should_alloc_space = dset_info[i].dset->shared->dcpl_cache.efl.nused == 0 &&
                             !(*dset_info[i].dset->shared->layout.ops->is_space_alloc)(
                                 &dset_info[i].dset->shared->layout.storage);

        /*
         * If not using an MPI-based VFD, we only need to allocate
         * and initialize storage if there's a selection in the
         * dataset's dataspace. Otherwise, we always need to participate
         * in the storage allocation since this may use collective
         * operations and we will hang if we don't participate.
         */
        if (!H5F_HAS_FEATURE(dset_info[i].dset->oloc.file, H5FD_FEAT_HAS_MPI))
            should_alloc_space = should_alloc_space && (dset_info[i].nelmts > 0);

        if (should_alloc_space) {
            hssize_t file_nelmts;    /* Number of elements in file dataset's dataspace */
            hbool_t  full_overwrite; /* Whether we are over-writing all the elements */

            /* Get the number of elements in file dataset's dataspace */
            if ((file_nelmts = H5S_GET_EXTENT_NPOINTS(dset_info[i].file_space)) < 0)
                HGOTO_ERROR(H5E_DATASET, H5E_BADVALUE, FAIL,
                            "can't retrieve number of elements in file dataset")

            /* Always allow fill values to be written if the dataset has a VL datatype */
            if (H5T_detect_class(dset_info[i].dset->shared->type, H5T_VLEN, FALSE))
                full_overwrite = FALSE;
            else
                full_overwrite = (hbool_t)((hsize_t)file_nelmts == dset_info[i].nelmts ? TRUE : FALSE);

            /* Allocate storage */
            if (H5D__alloc_storage(dset_info[i].dset, H5D_ALLOC_WRITE, full_overwrite, NULL) < 0)
                HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to initialize storage")
        } /* end if */

        /* Call storage method's I/O initialization routine */
        /* Init io_info.dset_info[] and generate piece_info in skip list */
        if (dset_info[i].layout_ops.io_init &&
            (*dset_info[i].layout_ops.io_init)(&io_info, &(dset_info[i])) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "can't initialize I/O info")
        dset_info[i].skip_io = FALSE;
        io_op_init++;

        /* Reset metadata tagging */
        H5AC_tag(prev_tag, NULL);
    } /* end of for loop */

    assert(io_op_init == count);

    /* Perform second phase of type info initialization */
    if (H5D__typeinfo_init_phase2(&io_info) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to set up type info (second phase)")

#ifdef H5_HAVE_PARALLEL
    /* Adjust I/O info for any parallel or selection I/O */
    if (H5D__ioinfo_adjust(&io_info) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL,
                    "unable to adjust I/O info for parallel or selection I/O")
#endif /* H5_HAVE_PARALLEL */

    /* Perform third phase of type info initialization */
    if (H5D__typeinfo_init_phase3(&io_info) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to set up type info (third phase)")

    H5CX_set_no_selection_io_cause(io_info.no_selection_io_cause);

    /* If multi dataset I/O callback is not provided, perform write IO via
     * single-dset path with looping */
    if (io_info.md_io_ops.multi_write_md) {
        /* Create sel_pieces array if any pieces are selected */
        if (io_info.piece_count > 0) {
            assert(!io_info.sel_pieces);
            assert(io_info.pieces_added == 0);

            /* Allocate sel_pieces array */
            if (NULL ==
                (io_info.sel_pieces = H5MM_malloc(io_info.piece_count * sizeof(io_info.sel_pieces[0]))))
                HGOTO_ERROR(H5E_DATASET, H5E_CANTALLOC, FAIL, "unable to allocate array of selected pieces")
        }

        /* MDIO-specific second phase initialization */
        for (i = 0; i < count; i++)
            if (dset_info[i].layout_ops.mdio_init) {
                haddr_t prev_tag = HADDR_UNDEF;

                /* set metadata tagging with dset oheader addr */
                H5AC_tag(dset_info[i].dset->oloc.addr, &prev_tag);

                /* Make second phase IO init call */
                if ((dset_info[i].layout_ops.mdio_init)(&io_info, &(dset_info[i])) < 0)
                    HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "can't populate array of selected pieces")

                /* Reset metadata tagging */
                H5AC_tag(prev_tag, NULL);
            }

        /* Invoke correct "high level" I/O routine */
        if ((*io_info.md_io_ops.multi_write_md)(&io_info) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_WRITEERROR, FAIL, "can't write data")
    } /* end if */
    else {
        haddr_t prev_tag = HADDR_UNDEF;

        /* Allocate selection I/O parameter arrays if necessary */
        if (!H5D_LAYOUT_CB_PERFORM_IO(&io_info) && io_info.piece_count > 0) {
            if (NULL == (io_info.mem_spaces = H5MM_malloc(io_info.piece_count * sizeof(H5S_t *))))
                HGOTO_ERROR(H5E_RESOURCE, H5E_CANTALLOC, FAIL,
                            "memory allocation failed for memory space list")
            if (NULL == (io_info.file_spaces = H5MM_malloc(io_info.piece_count * sizeof(H5S_t *))))
                HGOTO_ERROR(H5E_RESOURCE, H5E_CANTALLOC, FAIL, "memory allocation failed for file space list")
            if (NULL == (io_info.addrs = H5MM_malloc(io_info.piece_count * sizeof(haddr_t))))
                HGOTO_ERROR(H5E_RESOURCE, H5E_CANTALLOC, FAIL,
                            "memory allocation failed for piece address list")
            if (NULL == (io_info.element_sizes = H5MM_malloc(io_info.piece_count * sizeof(size_t))))
                HGOTO_ERROR(H5E_RESOURCE, H5E_CANTALLOC, FAIL,
                            "memory allocation failed for element size list")
            if (NULL == (io_info.wbufs = H5MM_malloc(io_info.piece_count * sizeof(const void *))))
                HGOTO_ERROR(H5E_RESOURCE, H5E_CANTALLOC, FAIL,
                            "memory allocation failed for write buffer list")
            if (io_info.max_tconv_type_size > 0)
                if (NULL ==
                    (io_info.sel_pieces = H5MM_malloc(io_info.piece_count * sizeof(io_info.sel_pieces[0]))))
                    HGOTO_ERROR(H5E_RESOURCE, H5E_CANTALLOC, FAIL,
                                "unable to allocate array of selected pieces")
        }

        /* loop with serial & single-dset write IO path */
        for (i = 0; i < count; i++) {
            assert(!dset_info[i].skip_io);

            /* set metadata tagging with dset oheader addr */
            H5AC_tag(dset_info->dset->oloc.addr, &prev_tag);

            /* Invoke correct "high level" I/O routine */
            if ((*dset_info[i].io_ops.multi_write)(&io_info, &dset_info[i]) < 0)
                HGOTO_ERROR(H5E_DATASET, H5E_WRITEERROR, FAIL, "can't write data")

            /* Reset metadata tagging */
            H5AC_tag(prev_tag, NULL);
        }

        /* Make final selection I/O call if the multi_write callbacks did not perform the actual I/O
         * (if using selection I/O and either multi dataset or type conversion) */
        if (!H5D_LAYOUT_CB_PERFORM_IO(&io_info)) {
            /* Check for type conversion */
            if (io_info.max_tconv_type_size > 0) {
                /* Type conversion pathway */
                if (H5D__scatgath_write_select(&io_info) < 0)
                    HGOTO_ERROR(H5E_DATASET, H5E_WRITEERROR, FAIL, "type conversion selection write failed")
            }
            else {
                /* Call selection I/O directly */
                H5_CHECK_OVERFLOW(io_info.pieces_added, size_t, uint32_t);
                if (H5F_shared_select_write(io_info.f_sh, H5FD_MEM_DRAW, (uint32_t)io_info.pieces_added,
                                            io_info.mem_spaces, io_info.file_spaces, io_info.addrs,
                                            io_info.element_sizes, io_info.wbufs) < 0)
                    HGOTO_ERROR(H5E_DATASET, H5E_WRITEERROR, FAIL, "selection write failed")
            }
        }

#ifdef H5_HAVE_PARALLEL
        /* Report the actual I/O mode to the application if appropriate */
        if (io_info.using_mpi_vfd) {
            H5FD_mpio_xfer_t xfer_mode; /* Parallel transfer for this request */

            /* Get the parallel I/O transfer mode */
            if (H5CX_get_io_xfer_mode(&xfer_mode) < 0)
                HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't get MPI-I/O transfer mode")

            /* Only report the collective I/O mode if we're actually performing collective I/O */
            if (xfer_mode == H5FD_MPIO_COLLECTIVE) {
                H5CX_set_mpio_actual_io_mode(io_info.actual_io_mode);

                /* If we did selection I/O, report that we used "link chunk" mode, since that's the most
                 * analogous to what selection I/O does */
                if (io_info.use_select_io == H5D_SELECTION_IO_MODE_ON)
                    H5CX_set_mpio_actual_chunk_opt(H5D_MPIO_LINK_CHUNK);
            }
        }
#endif /* H5_HAVE_PARALLEL */
    }

done:
    /* Shut down the I/O op information */
    for (i = 0; i < io_op_init; i++) {
        assert(!dset_info[i].skip_io);
        if (dset_info[i].layout_ops.io_term &&
            (*dset_info[i].layout_ops.io_term)(&io_info, &(dset_info[i])) < 0)
            HDONE_ERROR(H5E_DATASET, H5E_CANTCLOSEOBJ, FAIL, "unable to shut down I/O op info");
    }

    /* Shut down datatype info for operation */
    if (H5D__typeinfo_term(&io_info) < 0)
        HDONE_ERROR(H5E_DATASET, H5E_CANTCLOSEOBJ, FAIL, "unable to shut down type info");

    /* Discard projected mem spaces and restore originals */
    if (orig_mem_space) {
        for (i = 0; i < count; i++)
            if (orig_mem_space[i]) {
                if (H5S_close(dset_info[i].mem_space) < 0)
                    HDONE_ERROR(H5E_DATASET, H5E_CANTCLOSEOBJ, FAIL,
                                "unable to shut down projected memory dataspace");
                dset_info[i].mem_space = orig_mem_space[i];
            }

        /* Free orig_mem_space array if it was allocated */
        if (orig_mem_space != &orig_mem_space_local)
            H5MM_free(orig_mem_space);
    }

    /* Free global piece array */
    H5MM_xfree(io_info.sel_pieces);

    /* Free selection I/O arrays */
    H5MM_xfree(io_info.mem_spaces);
    H5MM_xfree(io_info.file_spaces);
    H5MM_xfree(io_info.addrs);
    H5MM_xfree(io_info.element_sizes);
    H5MM_xfree(io_info.wbufs);

    /* Free store array if it was allocated */
    if (store != &store_local)
        H5MM_free(store);

    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5D__write */

/*-------------------------------------------------------------------------
 * Function:	H5D__ioinfo_init
 *
 * Purpose:	General setup for H5D_io_info_t struct
 *
 * Return:	Non-negative on success/Negative on failure
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5D__ioinfo_init(size_t count, H5D_io_op_type_t op_type, H5D_dset_io_info_t *dset_info,
                 H5D_io_info_t *io_info)
{
    H5D_selection_io_mode_t selection_io_mode;

    FUNC_ENTER_PACKAGE_NOERR

    /* check args */
    assert(count > 0);
    assert(dset_info);
    assert(dset_info[0].dset->oloc.file);
    assert(io_info);

    /* Zero out struct */
    memset(io_info, 0, sizeof(*io_info));

    /* Set up simple fields */
    io_info->op_type = op_type;
    io_info->f_sh    = count > 0 ? H5F_SHARED(dset_info[0].dset->oloc.file) : NULL;
    io_info->count   = count;

    /* Start without multi-dataset I/O ops. If we're not using the collective
     * I/O path then we will call the single dataset callbacks in a loop. */

    /* Use provided dset_info */
    io_info->dsets_info = dset_info;

    /* Start with selection I/O mode from property list.  If enabled, layout callback will turn it off if it
     * is not supported by the layout.  Handling of H5D_SELECTION_IO_MODE_AUTO occurs in H5D__ioinfo_adjust.
     */
    H5CX_get_selection_io_mode(&selection_io_mode);
    io_info->use_select_io = selection_io_mode;

    /* Record no selection I/O cause if it was disabled by the API */
    if (selection_io_mode == H5D_SELECTION_IO_MODE_OFF)
        io_info->no_selection_io_cause = H5D_SEL_IO_DISABLE_BY_API;

#ifdef H5_HAVE_PARALLEL

    /* Determine if the file was opened with an MPI VFD */
    if (count > 0)
        io_info->using_mpi_vfd = H5F_HAS_FEATURE(dset_info[0].dset->oloc.file, H5FD_FEAT_HAS_MPI);
#endif /* H5_HAVE_PARALLEL */

    /* Check if we could potentially use in-place type conversion */
    if (op_type == H5D_IO_OP_READ)
        /* Always on for read (modulo other restrictions that are handled in layout callbacks) */
        io_info->may_use_in_place_tconv = TRUE;
    else
        /* Only enable in-place type conversion if we're allowed to modify the write buffer */
        H5CX_get_modify_write_buf(&io_info->may_use_in_place_tconv);

    FUNC_LEAVE_NOAPI(SUCCEED)
} /* end H5D__ioinfo_init() */

/*-------------------------------------------------------------------------
 * Function:	H5D__dset_ioinfo_init
 *
 * Purpose:	Routine for determining correct I/O operations for each I/O action.
 *
 * Return:	Non-negative on success/Negative on failure
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5D__dset_ioinfo_init(H5D_t *dset, H5D_dset_io_info_t *dset_info, H5D_storage_t *store)
{
    FUNC_ENTER_PACKAGE_NOERR

    /* check args */
    assert(dset);
    assert(dset->oloc.file);
    assert(dset_info->type_info.tpath);

    /* Set up "normal" I/O fields */
    dset_info->dset  = dset;
    dset_info->store = store;

    /* Set I/O operations to initial values */
    dset_info->layout_ops = *dset->shared->layout.ops;

    /* Set the "high-level" I/O operations for the dataset */
    dset_info->io_ops.multi_read  = dset->shared->layout.ops->ser_read;
    dset_info->io_ops.multi_write = dset->shared->layout.ops->ser_write;

    /* Set the I/O operations for reading/writing single blocks on disk */
    if (dset_info->type_info.is_xform_noop && dset_info->type_info.is_conv_noop) {
        /*
         * If there is no data transform or type conversion then read directly
         * into the application's buffer.
         * This saves at least one mem-to-mem copy.
         */
        dset_info->io_ops.single_read  = H5D__select_read;
        dset_info->io_ops.single_write = H5D__select_write;
    } /* end if */
    else {
        /*
         * This is the general case (type conversion, usually).
         */
        dset_info->io_ops.single_read  = H5D__scatgath_read;
        dset_info->io_ops.single_write = H5D__scatgath_write;
    } /* end else */

    FUNC_LEAVE_NOAPI(SUCCEED)
} /* end H5D__dset_ioinfo_init() */

/*-------------------------------------------------------------------------
 * Function:	H5D__typeinfo_init
 *
 * Purpose:	Routine for determining correct datatype information for
 *              each I/O action.
 *
 * Return:	Non-negative on success/Negative on failure
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5D__typeinfo_init(H5D_io_info_t *io_info, H5D_dset_io_info_t *dset_info, hid_t mem_type_id)
{
    H5D_type_info_t  *type_info;
    const H5D_t      *dset;
    const H5T_t      *src_type;            /* Source datatype */
    const H5T_t      *dst_type;            /* Destination datatype */
    H5Z_data_xform_t *data_transform;      /* Data transform info */
    herr_t            ret_value = SUCCEED; /* Return value	*/

    FUNC_ENTER_PACKAGE

    /* check args */
    assert(io_info);
    assert(dset_info);

    /* Set convenience pointers */
    type_info = &dset_info->type_info;
    dset      = dset_info->dset;
    assert(dset);

    /* Patch the top level file pointer for dt->shared->u.vlen.f if needed */
    if (H5T_patch_vlen_file(dset->shared->type, H5F_VOL_OBJ(dset->oloc.file)) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_CANTOPENOBJ, FAIL, "can't patch VL datatype file pointer")

    /* Initialize type info safely */
    memset(type_info, 0, sizeof(*type_info));

    /* Get the memory & dataset datatypes */
    if (NULL == (type_info->mem_type = (const H5T_t *)H5I_object_verify(mem_type_id, H5I_DATATYPE)))
        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a datatype")
    type_info->dset_type = dset->shared->type;

    if (io_info->op_type == H5D_IO_OP_WRITE) {
        src_type               = type_info->mem_type;
        dst_type               = dset->shared->type;
        type_info->src_type_id = mem_type_id;
        type_info->dst_type_id = dset->shared->type_id;
    } /* end if */
    else {
        src_type               = dset->shared->type;
        dst_type               = type_info->mem_type;
        type_info->src_type_id = dset->shared->type_id;
        type_info->dst_type_id = mem_type_id;
    } /* end else */

    /* Locate the type conversion function and dataspace conversion
     * functions, and set up the element numbering information. If a data
     * type conversion is necessary then register datatype IDs. Data type
     * conversion is necessary if the user has set the `need_bkg' to a high
     * enough value in xfer_parms since turning off datatype conversion also
     * turns off background preservation.
     */
    if (NULL == (type_info->tpath = H5T_path_find(src_type, dst_type)))
        HGOTO_ERROR(H5E_DATASET, H5E_UNSUPPORTED, FAIL, "unable to convert between src and dest datatype")

    /* Retrieve info from API context */
    if (H5CX_get_data_transform(&data_transform) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't get data transform info")

    /* Precompute some useful information */
    type_info->src_type_size = H5T_get_size(src_type);
    type_info->dst_type_size = H5T_get_size(dst_type);
    type_info->is_conv_noop  = H5T_path_noop(type_info->tpath);
    type_info->is_xform_noop = H5Z_xform_noop(data_transform);
    if (type_info->is_xform_noop && type_info->is_conv_noop) {
        type_info->cmpd_subset = NULL;
        type_info->need_bkg    = H5T_BKG_NO;
    } /* end if */
    else {
        H5T_bkg_t bkgr_buf_type; /* Background buffer type */

        /* Get info from API context */
        if (H5CX_get_bkgr_buf_type(&bkgr_buf_type) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't retrieve background buffer type")

        /* Check if the datatypes are compound subsets of one another */
        type_info->cmpd_subset = H5T_path_compound_subset(type_info->tpath);

        /* Update io_info->max_tconv_type_size */
        io_info->max_tconv_type_size =
            MAX3(io_info->max_tconv_type_size, type_info->src_type_size, type_info->dst_type_size);

        /* Check if we need a background buffer */
        if ((io_info->op_type == H5D_IO_OP_WRITE) && H5T_detect_class(dset->shared->type, H5T_VLEN, FALSE))
            type_info->need_bkg = H5T_BKG_YES;
        else {
            H5T_bkg_t path_bkg; /* Type conversion's background info */

            if ((path_bkg = H5T_path_bkg(type_info->tpath))) {
                /* Retrieve the bkgr buffer property */
                type_info->need_bkg = bkgr_buf_type;
                type_info->need_bkg = MAX(path_bkg, type_info->need_bkg);
            } /* end if */
            else
                type_info->need_bkg = H5T_BKG_NO; /*never needed even if app says yes*/
        }                                         /* end else */
    }                                             /* end else */

done:
    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5D__typeinfo_init() */

/*-------------------------------------------------------------------------
 * Function:    H5D__typeinfo_init_phase2
 *
 * Purpose:     Continue initializing type info for all datasets after
 *              calculating the max type size across all datasets, and
 *              before final determination of collective/independent in
 *              H5D__ioinfo_adjust().  Currently just checks to see if
 *              selection I/O can be used with type conversion, and sets
 *              no_collective_cause flags related to selection I/O.
 *
 * Return:      Non-negative on success/Negative on failure
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5D__typeinfo_init_phase2(H5D_io_info_t *io_info)
{
    herr_t ret_value = SUCCEED; /* Return value */

    FUNC_ENTER_PACKAGE

    /* check args */
    assert(io_info);

    /* If selection I/O mode is default (auto), enable it here if the VFD supports it (it will be turned off
     * later if something else conflicts), otherwise disable it.  If we're using the MPIO VFD, the automatic
     * selection will happen in H5D__mpio_opt_possible() inside H5D__ioinfo_adjust(). */
#ifdef H5_HAVE_PARALLEL
    if (!io_info->using_mpi_vfd)
#endif /* H5_HAVE_PARALLEL */
        if (io_info->use_select_io == H5D_SELECTION_IO_MODE_DEFAULT) {
            if (H5F_has_vector_select_io(io_info->dsets_info[0].dset->oloc.file,
                                         io_info->op_type == H5D_IO_OP_WRITE))
                io_info->use_select_io = H5D_SELECTION_IO_MODE_ON;
            else {
                io_info->use_select_io = H5D_SELECTION_IO_MODE_OFF;
                io_info->no_selection_io_cause |= H5D_SEL_IO_DEFAULT_OFF;
            }
        }

    /* If we're doing type conversion and we might be doing selection I/O, check if the buffers are large
     * enough to handle the whole I/O */
    if (io_info->max_tconv_type_size && io_info->use_select_io != H5D_SELECTION_IO_MODE_OFF) {
        size_t max_temp_buf; /* Maximum temporary buffer size */
        size_t i;            /* Local index variable */

        /* Collective I/O, conversion buffer must be large enough for entire I/O (for now) */

        /* Calculate size of background buffer (tconv buf size was calculated in layout io_init callbacks)
         */
        for (i = 0; i < io_info->count; i++) {
            H5D_type_info_t *type_info = &io_info->dsets_info[i].type_info;

            /* Check for background buffer */
            if (type_info->need_bkg) {
                /* Add size of this dataset's background buffer to the global background buffer size
                 */
                io_info->bkg_buf_size += io_info->dsets_info[i].nelmts * type_info->dst_type_size;

                /* Check if we need to fill the background buffer with the destination contents */
                if (type_info->need_bkg == H5T_BKG_YES)
                    io_info->must_fill_bkg = TRUE;
            }
        }

        /* Get max temp buffer size from API context */
        if (H5CX_get_max_temp_buf(&max_temp_buf) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't retrieve max. temp. buf size")

        /* Check if the needed type conversion or background buffer size is too big */
        if (io_info->tconv_buf_size > max_temp_buf) {
            io_info->use_select_io = H5D_SELECTION_IO_MODE_OFF;
            io_info->no_selection_io_cause |= H5D_SEL_IO_TCONV_BUF_TOO_SMALL;
            io_info->tconv_buf_size = 0;
            io_info->bkg_buf_size   = 0;
            io_info->must_fill_bkg  = FALSE;
        }
        if (io_info->bkg_buf_size > max_temp_buf) {
            io_info->use_select_io = H5D_SELECTION_IO_MODE_OFF;
            io_info->no_selection_io_cause |= H5D_SEL_IO_BKG_BUF_TOO_SMALL;
            io_info->tconv_buf_size = 0;
            io_info->bkg_buf_size   = 0;
            io_info->must_fill_bkg  = FALSE;
        }
    }

done:
    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5D__typeinfo_init_phase2() */

#ifdef H5_HAVE_PARALLEL
/*-------------------------------------------------------------------------
 * Function:    H5D__ioinfo_adjust
 *
 * Purpose:     Adjust operation's I/O info for any parallel I/O, also
 *              handle decision on selection I/O even in serial case
 *
 * Return:      Non-negative on success/Negative on failure
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5D__ioinfo_adjust(H5D_io_info_t *io_info)
{
    H5D_t *dset0;               /* only the first dset , also for single dsets case */
    herr_t ret_value = SUCCEED; /* Return value	*/

    FUNC_ENTER_PACKAGE

    /* check args */
    assert(io_info);

    /* check the first dset, should exist either single or multi dset cases */
    assert(io_info->dsets_info[0].dset);
    dset0 = io_info->dsets_info[0].dset;
    assert(dset0->oloc.file);

    /* Reset the actual io mode properties to the default values in case
     * the DXPL (if it's non-default) was previously used in a collective
     * I/O operation.
     */
    if (!H5CX_is_def_dxpl()) {
        H5CX_set_mpio_actual_chunk_opt(H5D_MPIO_NO_CHUNK_OPTIMIZATION);
        H5CX_set_mpio_actual_io_mode(H5D_MPIO_NO_COLLECTIVE);
    } /* end if */

    /* Make any parallel I/O adjustments */
    if (io_info->using_mpi_vfd) {
        H5FD_mpio_xfer_t xfer_mode; /* Parallel transfer for this request */
        htri_t           opt;       /* Flag whether a selection is optimizable */

        /* Get the original state of parallel I/O transfer mode */
        if (H5CX_get_io_xfer_mode(&xfer_mode) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't get MPI-I/O transfer mode")

        /* Get MPI communicator */
        if (MPI_COMM_NULL == (io_info->comm = H5F_mpi_get_comm(dset0->oloc.file)))
            HGOTO_ERROR(H5E_DATASPACE, H5E_CANTGET, FAIL, "can't retrieve MPI communicator")

        /* Check if we can set direct MPI-IO read/write functions */
        if ((opt = H5D__mpio_opt_possible(io_info)) < 0)
            HGOTO_ERROR(H5E_DATASPACE, H5E_BADRANGE, FAIL, "invalid check for direct IO dataspace ")

        /* Check if we can use the optimized parallel I/O routines */
        if (opt == TRUE) {
            /* Override the I/O op pointers to the MPI-specific routines, unless
             * selection I/O is to be used - in this case the file driver will
             * handle collective I/O */
            /* Check for selection/vector support in file driver? -NAF */
            if (io_info->use_select_io == H5D_SELECTION_IO_MODE_OFF) {
                io_info->md_io_ops.multi_read_md   = H5D__collective_read;
                io_info->md_io_ops.multi_write_md  = H5D__collective_write;
                io_info->md_io_ops.single_read_md  = H5D__mpio_select_read;
                io_info->md_io_ops.single_write_md = H5D__mpio_select_write;
            } /* end if */
        }     /* end if */
        else {
            /* Fail when file sync is required, since it requires collective write */
            if (io_info->op_type == H5D_IO_OP_WRITE) {
                hbool_t mpi_file_sync_required = FALSE;
                if (H5F_shared_get_mpi_file_sync_required(io_info->f_sh, &mpi_file_sync_required) < 0)
                    HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't get MPI file_sync_required flag")

                if (mpi_file_sync_required)
                    HGOTO_ERROR(
                        H5E_DATASET, H5E_NO_INDEPENDENT, FAIL,
                        "Can't perform independent write when MPI_File_sync is required by ROMIO driver.")
            }

            /* Check if there are any filters in the pipeline. If there are,
             * we cannot break to independent I/O if this is a write operation
             * with multiple ranks involved; otherwise, there will be metadata
             * inconsistencies in the file.
             */
            if (io_info->op_type == H5D_IO_OP_WRITE) {
                size_t i;

                /* Check all datasets for filters */
                for (i = 0; i < io_info->count; i++)
                    if (io_info->dsets_info[i].dset->shared->dcpl_cache.pline.nused > 0)
                        break;

                /* If the above loop didn't complete at least one dataset has a filter */
                if (i < io_info->count) {
                    int comm_size = 0;

                    /* Retrieve size of MPI communicator used for file */
                    if ((comm_size = H5F_shared_mpi_get_size(io_info->f_sh)) < 0)
                        HGOTO_ERROR(H5E_FILE, H5E_CANTGET, FAIL, "can't get MPI communicator size")

                    if (comm_size > 1) {
                        char local_no_coll_cause_string[512];
                        char global_no_coll_cause_string[512];

                        if (H5D__mpio_get_no_coll_cause_strings(local_no_coll_cause_string, 512,
                                                                global_no_coll_cause_string, 512) < 0)
                            HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL,
                                        "can't get reasons for breaking collective I/O")

                        HGOTO_ERROR(H5E_IO, H5E_NO_INDEPENDENT, FAIL,
                                    "Can't perform independent write with filters in pipeline.\n"
                                    "    The following caused a break from collective I/O:\n"
                                    "        Local causes: %s\n"
                                    "        Global causes: %s",
                                    local_no_coll_cause_string, global_no_coll_cause_string);
                    }
                }
            }

            /* If we won't be doing collective I/O, but the user asked for
             * collective I/O, change the request to use independent I/O
             */
            if (xfer_mode == H5FD_MPIO_COLLECTIVE) {
                /* Change the xfer_mode to independent for handling the I/O */
                if (H5CX_set_io_xfer_mode(H5FD_MPIO_INDEPENDENT) < 0)
                    HGOTO_ERROR(H5E_DATASET, H5E_CANTSET, FAIL, "can't set MPI-I/O transfer mode")
            } /* end if */
        }     /* end else */
    }         /* end if */

done:
    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5D__ioinfo_adjust() */
#endif /* H5_HAVE_PARALLEL */

/*-------------------------------------------------------------------------
 * Function:    H5D__typeinfo_init_phase3
 *
 * Purpose:     Finish initializing type info for all datasets after
 *              calculating the max type size across all datasets.  And
 *              after final collective/independent determination in
 *              H5D__ioinfo_adjust().
 *
 * Return:      Non-negative on success/Negative on failure
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5D__typeinfo_init_phase3(H5D_io_info_t *io_info)
{
    herr_t ret_value = SUCCEED; /* Return value */

    FUNC_ENTER_PACKAGE

    /* check args */
    assert(io_info);

    /* Check if we need to allocate a shared type conversion buffer */
    if (io_info->max_tconv_type_size) {
        void *tconv_buf; /* Temporary conversion buffer pointer */
        void *bkgr_buf;  /* Background conversion buffer pointer */

        /* Get provided buffers from API context */
        if (H5CX_get_tconv_buf(&tconv_buf) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't retrieve temp. conversion buffer pointer")
        if (H5CX_get_bkgr_buf(&bkgr_buf) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't retrieve background conversion buffer pointer")

        /* Check if we're doing selection I/O */
        if (io_info->use_select_io == H5D_SELECTION_IO_MODE_ON) {
            /* Selection I/O, conversion buffers must be large enough for entire I/O (for now) */

            /* Allocate global type conversion buffer (if any, could be none if datasets in this
             * I/O have 0 elements selected) */
            /* Allocating large buffers here will blow out all other type conversion buffers
             * on the free list.  Should we change this to a regular malloc?  Would require
             * keeping track of which version of free() to call. -NAF */
            if (io_info->tconv_buf_size > 0) {
                if (NULL == (io_info->tconv_buf = H5FL_BLK_MALLOC(type_conv, io_info->tconv_buf_size)))
                    HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL,
                                "memory allocation failed for type conversion")
                io_info->tconv_buf_allocated = TRUE;
            }

            /* Allocate global background buffer (if any) */
            if (io_info->bkg_buf_size > 0) {
                if (NULL == (io_info->bkg_buf = H5FL_BLK_MALLOC(type_conv, io_info->bkg_buf_size)))
                    HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL,
                                "memory allocation failed for type conversion")
                io_info->bkg_buf_allocated = TRUE;
            }
        }
        else {
            /* No selection I/O, only need to make sure it's big enough for one element */
            size_t max_temp_buf; /* Maximum temporary buffer size */
            size_t target_size;  /* Desired buffer size	*/
            size_t i;

            /* Make sure selection I/O is disabled (DEFAULT should have been handled by now) */
            assert(io_info->use_select_io == H5D_SELECTION_IO_MODE_OFF);

            /* Get max buffer size from API context */
            if (H5CX_get_max_temp_buf(&max_temp_buf) < 0)
                HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't retrieve max. temp. buf size")

            /* Set up datatype conversion/background buffers */
            target_size = max_temp_buf;

            /* If the buffer is too small to hold even one element (in the dataset with the largest , try to
             * make it bigger */
            if (target_size < io_info->max_tconv_type_size) {
                hbool_t default_buffer_info; /* Whether the buffer information are the defaults */

                /* Detect if we have all default settings for buffers */
                default_buffer_info = (hbool_t)((H5D_TEMP_BUF_SIZE == max_temp_buf) && (NULL == tconv_buf) &&
                                                (NULL == bkgr_buf));

                /* Check if we are using the default buffer info */
                if (default_buffer_info)
                    /* OK to get bigger for library default settings */
                    target_size = io_info->max_tconv_type_size;
                else
                    /* Don't get bigger than the application has requested */
                    HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "temporary buffer max size is too small")
            } /* end if */

            /* Get a temporary buffer for type conversion unless the app has already
             * supplied one through the xfer properties. Instead of allocating a
             * buffer which is the exact size, we allocate the target size. This
             * buffer is shared among all datasets in the operation. */
            if (NULL == (io_info->tconv_buf = (uint8_t *)tconv_buf)) {
                /* Allocate temporary buffer */
                if (NULL == (io_info->tconv_buf = H5FL_BLK_MALLOC(type_conv, target_size)))
                    HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL,
                                "memory allocation failed for type conversion")
                io_info->tconv_buf_allocated = TRUE;
            } /* end if */

            /* Iterate over datasets */
            for (i = 0; i < io_info->count; i++) {
                H5D_type_info_t *type_info = &io_info->dsets_info[i].type_info;

                /* Compute the number of elements that will fit into buffer */
                type_info->request_nelmts =
                    target_size / MAX(type_info->src_type_size, type_info->dst_type_size);

                /* Check if we need a background buffer and one hasn't been allocated yet */
                if (type_info->need_bkg && (NULL == io_info->bkg_buf) &&
                    (NULL == (io_info->bkg_buf = (uint8_t *)bkgr_buf))) {
                    /* Allocate background buffer with the same size as the type conversion buffer.  We can do
                     * this since the number of elements that fit in the type conversion buffer will never be
                     * larger than the number that could fit in a background buffer of equal size, since the
                     * tconv element size is max(src, dst) and the bkg element size is dst */
                    if (NULL == (io_info->bkg_buf = H5FL_BLK_MALLOC(type_conv, target_size)))
                        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL,
                                    "memory allocation failed for background conversion")
                    io_info->bkg_buf_allocated = TRUE;
                }
            }
        }
    }

done:
    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5D__typeinfo_init_phase3() */

/*-------------------------------------------------------------------------
 * Function:    H5D__typeinfo_term
 *
 * Purpose:     Common logic for terminating a type info object
 *
 * Return:      Non-negative on success/Negative on failure
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5D__typeinfo_term(H5D_io_info_t *io_info)
{
    FUNC_ENTER_PACKAGE_NOERR

    /* Check for releasing datatype conversion & background buffers */
    if (io_info->tconv_buf_allocated) {
        assert(io_info->tconv_buf);
        (void)H5FL_BLK_FREE(type_conv, io_info->tconv_buf);
    } /* end if */
    if (io_info->bkg_buf_allocated) {
        assert(io_info->bkg_buf);
        (void)H5FL_BLK_FREE(type_conv, io_info->bkg_buf);
    } /* end if */

    FUNC_LEAVE_NOAPI(SUCCEED)
} /* end H5D__typeinfo_term() */