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authorSerenaFeng <feng.xiaowei@zte.com.cn>2017-03-28 19:13:10 +0800
committerSerenaFeng <feng.xiaowei@zte.com.cn>2017-03-28 19:13:10 +0800
commite46602b7c1f53b12b5f6d3bfe6517a7440d9aa03 (patch)
treeb4030c02bb9c1020ccacfc20d6b2ea66ace71aa5 /docs
parenta14250045fe6fb99bd8a707c59016cba3df4a851 (diff)
modify old naming Testcase_base to TestCase
Testcase_base is the first version, now TestCase is adopted Change-Id: If25eef0d8164220bd36f86fe636f7f1c0b247564 Signed-off-by: SerenaFeng <feng.xiaowei@zte.com.cn>
Diffstat (limited to 'docs')
-rw-r--r--docs/testing/developer/devguide/index.rst2
1 files changed, 1 insertions, 1 deletions
diff --git a/docs/testing/developer/devguide/index.rst b/docs/testing/developer/devguide/index.rst
index 366eb7d3..67890f0b 100644
--- a/docs/testing/developer/devguide/index.rst
+++ b/docs/testing/developer/devguide/index.rst
@@ -166,7 +166,7 @@ feature_base and vnf_base inherit from testcase::
+-----------------------------------------+
| |
- | Testcase_base |
+ | TestCase |
| |
| - init() |
| - run() |
'#n209'>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
#include <linux/errno.h>
#include <linux/numa.h>
#include <linux/slab.h>
#include <linux/rculist.h>
#include <linux/threads.h>
#include <linux/preempt.h>
#include <linux/irqflags.h>
#include <linux/vmalloc.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/device-mapper.h>

#include "dm.h"
#include "dm-stats.h"

#define DM_MSG_PREFIX "stats"

static int dm_stat_need_rcu_barrier;

/*
 * Using 64-bit values to avoid overflow (which is a
 * problem that block/genhd.c's IO accounting has).
 */
struct dm_stat_percpu {
	unsigned long long sectors[2];
	unsigned long long ios[2];
	unsigned long long merges[2];
	unsigned long long ticks[2];
	unsigned long long io_ticks[2];
	unsigned long long io_ticks_total;
	unsigned long long time_in_queue;
	unsigned long long *histogram;
};

struct dm_stat_shared {
	atomic_t in_flight[2];
	unsigned long long stamp;
	struct dm_stat_percpu tmp;
};

struct dm_stat {
	struct list_head list_entry;
	int id;
	unsigned stat_flags;
	size_t n_entries;
	sector_t start;
	sector_t end;
	sector_t step;
	unsigned n_histogram_entries;
	unsigned long long *histogram_boundaries;
	const char *program_id;
	const char *aux_data;
	struct rcu_head rcu_head;
	size_t shared_alloc_size;
	size_t percpu_alloc_size;
	size_t histogram_alloc_size;
	struct dm_stat_percpu *stat_percpu[NR_CPUS];
	struct dm_stat_shared stat_shared[0];
};

#define STAT_PRECISE_TIMESTAMPS		1

struct dm_stats_last_position {
	sector_t last_sector;
	unsigned last_rw;
};

/*
 * A typo on the command line could possibly make the kernel run out of memory
 * and crash. To prevent the crash we account all used memory. We fail if we
 * exhaust 1/4 of all memory or 1/2 of vmalloc space.
 */
#define DM_STATS_MEMORY_FACTOR		4
#define DM_STATS_VMALLOC_FACTOR		2

static DEFINE_SPINLOCK(shared_memory_lock);

static unsigned long shared_memory_amount;

static bool __check_shared_memory(size_t alloc_size)
{
	size_t a;

	a = shared_memory_amount + alloc_size;
	if (a < shared_memory_amount)
		return false;
	if (a >> PAGE_SHIFT > totalram_pages / DM_STATS_MEMORY_FACTOR)
		return false;
#ifdef CONFIG_MMU
	if (a > (VMALLOC_END - VMALLOC_START) / DM_STATS_VMALLOC_FACTOR)
		return false;
#endif
	return true;
}

static bool check_shared_memory(size_t alloc_size)
{
	bool ret;

	spin_lock_irq(&shared_memory_lock);

	ret = __check_shared_memory(alloc_size);

	spin_unlock_irq(&shared_memory_lock);

	return ret;
}

static bool claim_shared_memory(size_t alloc_size)
{
	spin_lock_irq(&shared_memory_lock);

	if (!__check_shared_memory(alloc_size)) {
		spin_unlock_irq(&shared_memory_lock);
		return false;
	}

	shared_memory_amount += alloc_size;

	spin_unlock_irq(&shared_memory_lock);

	return true;
}

static void free_shared_memory(size_t alloc_size)
{
	unsigned long flags;

	spin_lock_irqsave(&shared_memory_lock, flags);

	if (WARN_ON_ONCE(shared_memory_amount < alloc_size)) {
		spin_unlock_irqrestore(&shared_memory_lock, flags);
		DMCRIT("Memory usage accounting bug.");
		return;
	}

	shared_memory_amount -= alloc_size;

	spin_unlock_irqrestore(&shared_memory_lock, flags);
}

static void *dm_kvzalloc(size_t alloc_size, int node)
{
	void *p;

	if (!claim_shared_memory(alloc_size))
		return NULL;

	if (alloc_size <= KMALLOC_MAX_SIZE) {
		p = kzalloc_node(alloc_size, GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN, node);
		if (p)
			return p;
	}
	p = vzalloc_node(alloc_size, node);
	if (p)
		return p;

	free_shared_memory(alloc_size);

	return NULL;
}

static void dm_kvfree(void *ptr, size_t alloc_size)
{
	if (!ptr)
		return;

	free_shared_memory(alloc_size);

	kvfree(ptr);
}

static void dm_stat_free(struct rcu_head *head)
{
	int cpu;
	struct dm_stat *s = container_of(head, struct dm_stat, rcu_head);

	kfree(s->program_id);
	kfree(s->aux_data);
	for_each_possible_cpu(cpu) {
		dm_kvfree(s->stat_percpu[cpu][0].histogram, s->histogram_alloc_size);
		dm_kvfree(s->stat_percpu[cpu], s->percpu_alloc_size);
	}
	dm_kvfree(s->stat_shared[0].tmp.histogram, s->histogram_alloc_size);
	dm_kvfree(s, s->shared_alloc_size);
}

static int dm_stat_in_flight(struct dm_stat_shared *shared)
{
	return atomic_read(&shared->in_flight[READ]) +
	       atomic_read(&shared->in_flight[WRITE]);
}

void dm_stats_init(struct dm_stats *stats)
{
	int cpu;
	struct dm_stats_last_position *last;

	mutex_init(&stats->mutex);
	INIT_LIST_HEAD(&stats->list);
	stats->last = alloc_percpu(struct dm_stats_last_position);
	for_each_possible_cpu(cpu) {
		last = per_cpu_ptr(stats->last, cpu);
		last->last_sector = (sector_t)ULLONG_MAX;
		last->last_rw = UINT_MAX;
	}
}

void dm_stats_cleanup(struct dm_stats *stats)
{
	size_t ni;
	struct dm_stat *s;
	struct dm_stat_shared *shared;

	while (!list_empty(&stats->list)) {
		s = container_of(stats->list.next, struct dm_stat, list_entry);
		list_del(&s->list_entry);
		for (ni = 0; ni < s->n_entries; ni++) {
			shared = &s->stat_shared[ni];
			if (WARN_ON(dm_stat_in_flight(shared))) {
				DMCRIT("leaked in-flight counter at index %lu "
				       "(start %llu, end %llu, step %llu): reads %d, writes %d",
				       (unsigned long)ni,
				       (unsigned long long)s->start,
				       (unsigned long long)s->end,
				       (unsigned long long)s->step,
				       atomic_read(&shared->in_flight[READ]),
				       atomic_read(&shared->in_flight[WRITE]));
			}
		}
		dm_stat_free(&s->rcu_head);
	}
	free_percpu(stats->last);
}

static int dm_stats_create(struct dm_stats *stats, sector_t start, sector_t end,
			   sector_t step, unsigned stat_flags,
			   unsigned n_histogram_entries,
			   unsigned long long *histogram_boundaries,
			   const char *program_id, const char *aux_data,
			   void (*suspend_callback)(struct mapped_device *),
			   void (*resume_callback)(struct mapped_device *),
			   struct mapped_device *md)
{
	struct list_head *l;
	struct dm_stat *s, *tmp_s;
	sector_t n_entries;
	size_t ni;
	size_t shared_alloc_size;
	size_t percpu_alloc_size;
	size_t histogram_alloc_size;
	struct dm_stat_percpu *p;
	int cpu;
	int ret_id;
	int r;

	if (end < start || !step)
		return -EINVAL;

	n_entries = end - start;
	if (dm_sector_div64(n_entries, step))
		n_entries++;

	if (n_entries != (size_t)n_entries || !(size_t)(n_entries + 1))
		return -EOVERFLOW;

	shared_alloc_size = sizeof(struct dm_stat) + (size_t)n_entries * sizeof(struct dm_stat_shared);
	if ((shared_alloc_size - sizeof(struct dm_stat)) / sizeof(struct dm_stat_shared) != n_entries)
		return -EOVERFLOW;

	percpu_alloc_size = (size_t)n_entries * sizeof(struct dm_stat_percpu);
	if (percpu_alloc_size / sizeof(struct dm_stat_percpu) != n_entries)
		return -EOVERFLOW;

	histogram_alloc_size = (n_histogram_entries + 1) * (size_t)n_entries * sizeof(unsigned long long);
	if (histogram_alloc_size / (n_histogram_entries + 1) != (size_t)n_entries * sizeof(unsigned long long))
		return -EOVERFLOW;

	if (!check_shared_memory(shared_alloc_size + histogram_alloc_size +
				 num_possible_cpus() * (percpu_alloc_size + histogram_alloc_size)))
		return -ENOMEM;

	s = dm_kvzalloc(shared_alloc_size, NUMA_NO_NODE);
	if (!s)
		return -ENOMEM;

	s->stat_flags = stat_flags;
	s->n_entries = n_entries;
	s->start = start;
	s->end = end;
	s->step = step;
	s->shared_alloc_size = shared_alloc_size;
	s->percpu_alloc_size = percpu_alloc_size;
	s->histogram_alloc_size = histogram_alloc_size;

	s->n_histogram_entries = n_histogram_entries;
	s->histogram_boundaries = kmemdup(histogram_boundaries,
					  s->n_histogram_entries * sizeof(unsigned long long), GFP_KERNEL);
	if (!s->histogram_boundaries) {
		r = -ENOMEM;
		goto out;
	}

	s->program_id = kstrdup(program_id, GFP_KERNEL);
	if (!s->program_id) {
		r = -ENOMEM;
		goto out;
	}
	s->aux_data = kstrdup(aux_data, GFP_KERNEL);
	if (!s->aux_data) {
		r = -ENOMEM;
		goto out;
	}

	for (ni = 0; ni < n_entries; ni++) {
		atomic_set(&s->stat_shared[ni].in_flight[READ], 0);
		atomic_set(&s->stat_shared[ni].in_flight[WRITE], 0);
	}

	if (s->n_histogram_entries) {
		unsigned long long *hi;
		hi = dm_kvzalloc(s->histogram_alloc_size, NUMA_NO_NODE);
		if (!hi) {
			r = -ENOMEM;
			goto out;
		}
		for (ni = 0; ni < n_entries; ni++) {
			s->stat_shared[ni].tmp.histogram = hi;
			hi += s->n_histogram_entries + 1;
		}
	}

	for_each_possible_cpu(cpu) {
		p = dm_kvzalloc(percpu_alloc_size, cpu_to_node(cpu));
		if (!p) {
			r = -ENOMEM;
			goto out;
		}
		s->stat_percpu[cpu] = p;
		if (s->n_histogram_entries) {
			unsigned long long *hi;
			hi = dm_kvzalloc(s->histogram_alloc_size, cpu_to_node(cpu));
			if (!hi) {
				r = -ENOMEM;
				goto out;
			}
			for (ni = 0; ni < n_entries; ni++) {
				p[ni].histogram = hi;
				hi += s->n_histogram_entries + 1;
			}
		}
	}

	/*
	 * Suspend/resume to make sure there is no i/o in flight,
	 * so that newly created statistics will be exact.
	 *
	 * (note: we couldn't suspend earlier because we must not
	 * allocate memory while suspended)
	 */
	suspend_callback(md);

	mutex_lock(&stats->mutex);
	s->id = 0;
	list_for_each(l, &stats->list) {
		tmp_s = container_of(l, struct dm_stat, list_entry);
		if (WARN_ON(tmp_s->id < s->id)) {
			r = -EINVAL;
			goto out_unlock_resume;
		}
		if (tmp_s->id > s->id)
			break;
		if (unlikely(s->id == INT_MAX)) {
			r = -ENFILE;
			goto out_unlock_resume;
		}
		s->id++;
	}
	ret_id = s->id;
	list_add_tail_rcu(&s->list_entry, l);
	mutex_unlock(&stats->mutex);

	resume_callback(md);

	return ret_id;

out_unlock_resume:
	mutex_unlock(&stats->mutex);
	resume_callback(md);
out:
	dm_stat_free(&s->rcu_head);
	return r;
}

static struct dm_stat *__dm_stats_find(struct dm_stats *stats, int id)
{
	struct dm_stat *s;

	list_for_each_entry(s, &stats->list, list_entry) {
		if (s->id > id)
			break;
		if (s->id == id)
			return s;
	}

	return NULL;
}

static int dm_stats_delete(struct dm_stats *stats, int id)
{
	struct dm_stat *s;
	int cpu;

	mutex_lock(&stats->mutex);

	s = __dm_stats_find(stats, id);
	if (!s) {
		mutex_unlock(&stats->mutex);
		return -ENOENT;
	}

	list_del_rcu(&s->list_entry);
	mutex_unlock(&stats->mutex);

	/*
	 * vfree can't be called from RCU callback
	 */
	for_each_possible_cpu(cpu)
		if (is_vmalloc_addr(s->stat_percpu) ||
		    is_vmalloc_addr(s->stat_percpu[cpu][0].histogram))
			goto do_sync_free;
	if (is_vmalloc_addr(s) ||
	    is_vmalloc_addr(s->stat_shared[0].tmp.histogram)) {
do_sync_free:
		synchronize_rcu_expedited();
		dm_stat_free(&s->rcu_head);
	} else {
		ACCESS_ONCE(dm_stat_need_rcu_barrier) = 1;
		call_rcu(&s->rcu_head, dm_stat_free);
	}
	return 0;
}

static int dm_stats_list(struct dm_stats *stats, const char *program,
			 char *result, unsigned maxlen)
{
	struct dm_stat *s;
	sector_t len;
	unsigned sz = 0;

	/*
	 * Output format:
	 *   <region_id>: <start_sector>+<length> <step> <program_id> <aux_data>
	 */

	mutex_lock(&stats->mutex);
	list_for_each_entry(s, &stats->list, list_entry) {
		if (!program || !strcmp(program, s->program_id)) {
			len = s->end - s->start;
			DMEMIT("%d: %llu+%llu %llu %s %s", s->id,
				(unsigned long long)s->start,
				(unsigned long long)len,
				(unsigned long long)s->step,
				s->program_id,
				s->aux_data);
			if (s->stat_flags & STAT_PRECISE_TIMESTAMPS)
				DMEMIT(" precise_timestamps");
			if (s->n_histogram_entries) {
				unsigned i;
				DMEMIT(" histogram:");
				for (i = 0; i < s->n_histogram_entries; i++) {
					if (i)
						DMEMIT(",");
					DMEMIT("%llu", s->histogram_boundaries[i]);
				}
			}
			DMEMIT("\n");
		}
	}
	mutex_unlock(&stats->mutex);

	return 1;
}

static void dm_stat_round(struct dm_stat *s, struct dm_stat_shared *shared,
			  struct dm_stat_percpu *p)
{
	/*
	 * This is racy, but so is part_round_stats_single.
	 */
	unsigned long long now, difference;
	unsigned in_flight_read, in_flight_write;

	if (likely(!(s->stat_flags & STAT_PRECISE_TIMESTAMPS)))
		now = jiffies;
	else
		now = ktime_to_ns(ktime_get());

	difference = now - shared->stamp;
	if (!difference)
		return;

	in_flight_read = (unsigned)atomic_read(&shared->in_flight[READ]);
	in_flight_write = (unsigned)atomic_read(&shared->in_flight[WRITE]);
	if (in_flight_read)
		p->io_ticks[READ] += difference;
	if (in_flight_write)
		p->io_ticks[WRITE] += difference;
	if (in_flight_read + in_flight_write) {
		p->io_ticks_total += difference;
		p->time_in_queue += (in_flight_read + in_flight_write) * difference;
	}
	shared->stamp = now;
}

static void dm_stat_for_entry(struct dm_stat *s, size_t entry,
			      unsigned long bi_rw, sector_t len,
			      struct dm_stats_aux *stats_aux, bool end,
			      unsigned long duration_jiffies)
{
	unsigned long idx = bi_rw & REQ_WRITE;
	struct dm_stat_shared *shared = &s->stat_shared[entry];
	struct dm_stat_percpu *p;

	/*
	 * For strict correctness we should use local_irq_save/restore
	 * instead of preempt_disable/enable.
	 *
	 * preempt_disable/enable is racy if the driver finishes bios
	 * from non-interrupt context as well as from interrupt context
	 * or from more different interrupts.
	 *
	 * On 64-bit architectures the race only results in not counting some
	 * events, so it is acceptable.  On 32-bit architectures the race could
	 * cause the counter going off by 2^32, so we need to do proper locking
	 * there.
	 *
	 * part_stat_lock()/part_stat_unlock() have this race too.
	 */
#if BITS_PER_LONG == 32
	unsigned long flags;
	local_irq_save(flags);
#else
	preempt_disable();
#endif
	p = &s->stat_percpu[smp_processor_id()][entry];

	if (!end) {
		dm_stat_round(s, shared, p);
		atomic_inc(&shared->in_flight[idx]);
	} else {
		unsigned long long duration;
		dm_stat_round(s, shared, p);
		atomic_dec(&shared->in_flight[idx]);
		p->sectors[idx] += len;
		p->ios[idx] += 1;
		p->merges[idx] += stats_aux->merged;
		if (!(s->stat_flags & STAT_PRECISE_TIMESTAMPS)) {
			p->ticks[idx] += duration_jiffies;
			duration = jiffies_to_msecs(duration_jiffies);
		} else {
			p->ticks[idx] += stats_aux->duration_ns;
			duration = stats_aux->duration_ns;
		}
		if (s->n_histogram_entries) {
			unsigned lo = 0, hi = s->n_histogram_entries + 1;
			while (lo + 1 < hi) {
				unsigned mid = (lo + hi) / 2;
				if (s->histogram_boundaries[mid - 1] > duration) {
					hi = mid;
				} else {
					lo = mid;
				}

			}
			p->histogram[lo]++;
		}
	}

#if BITS_PER_LONG == 32
	local_irq_restore(flags);
#else
	preempt_enable();
#endif
}

static void __dm_stat_bio(struct dm_stat *s, unsigned long bi_rw,
			  sector_t bi_sector, sector_t end_sector,
			  bool end, unsigned long duration_jiffies,
			  struct dm_stats_aux *stats_aux)
{
	sector_t rel_sector, offset, todo, fragment_len;
	size_t entry;

	if (end_sector <= s->start || bi_sector >= s->end)
		return;
	if (unlikely(bi_sector < s->start)) {
		rel_sector = 0;
		todo = end_sector - s->start;
	} else {
		rel_sector = bi_sector - s->start;
		todo = end_sector - bi_sector;
	}
	if (unlikely(end_sector > s->end))
		todo -= (end_sector - s->end);

	offset = dm_sector_div64(rel_sector, s->step);
	entry = rel_sector;
	do {
		if (WARN_ON_ONCE(entry >= s->n_entries)) {
			DMCRIT("Invalid area access in region id %d", s->id);
			return;
		}
		fragment_len = todo;
		if (fragment_len > s->step - offset)
			fragment_len = s->step - offset;
		dm_stat_for_entry(s, entry, bi_rw, fragment_len,
				  stats_aux, end, duration_jiffies);
		todo -= fragment_len;
		entry++;
		offset = 0;
	} while (unlikely(todo != 0));
}

void dm_stats_account_io(struct dm_stats *stats, unsigned long bi_rw,
			 sector_t bi_sector, unsigned bi_sectors, bool end,
			 unsigned long duration_jiffies,
			 struct dm_stats_aux *stats_aux)
{
	struct dm_stat *s;
	sector_t end_sector;
	struct dm_stats_last_position *last;
	bool got_precise_time;

	if (unlikely(!bi_sectors))
		return;

	end_sector = bi_sector + bi_sectors;

	if (!end) {
		/*
		 * A race condition can at worst result in the merged flag being
		 * misrepresented, so we don't have to disable preemption here.
		 */
		last = raw_cpu_ptr(stats->last);
		stats_aux->merged =
			(bi_sector == (ACCESS_ONCE(last->last_sector) &&
				       ((bi_rw & (REQ_WRITE | REQ_DISCARD)) ==
					(ACCESS_ONCE(last->last_rw) & (REQ_WRITE | REQ_DISCARD)))
				       ));
		ACCESS_ONCE(last->last_sector) = end_sector;
		ACCESS_ONCE(last->last_rw) = bi_rw;
	}

	rcu_read_lock();

	got_precise_time = false;
	list_for_each_entry_rcu(s, &stats->list, list_entry) {
		if (s->stat_flags & STAT_PRECISE_TIMESTAMPS && !got_precise_time) {
			if (!end)
				stats_aux->duration_ns = ktime_to_ns(ktime_get());
			else
				stats_aux->duration_ns = ktime_to_ns(ktime_get()) - stats_aux->duration_ns;
			got_precise_time = true;
		}
		__dm_stat_bio(s, bi_rw, bi_sector, end_sector, end, duration_jiffies, stats_aux);
	}

	rcu_read_unlock();
}

static void __dm_stat_init_temporary_percpu_totals(struct dm_stat_shared *shared,
						   struct dm_stat *s, size_t x)
{
	int cpu;
	struct dm_stat_percpu *p;

	local_irq_disable();
	p = &s->stat_percpu[smp_processor_id()][x];
	dm_stat_round(s, shared, p);
	local_irq_enable();

	shared->tmp.sectors[READ] = 0;
	shared->tmp.sectors[WRITE] = 0;
	shared->tmp.ios[READ] = 0;
	shared->tmp.ios[WRITE] = 0;
	shared->tmp.merges[READ] = 0;
	shared->tmp.merges[WRITE] = 0;
	shared->tmp.ticks[READ] = 0;
	shared->tmp.ticks[WRITE] = 0;
	shared->tmp.io_ticks[READ] = 0;
	shared->tmp.io_ticks[WRITE] = 0;
	shared->tmp.io_ticks_total = 0;
	shared->tmp.time_in_queue = 0;

	if (s->n_histogram_entries)
		memset(shared->tmp.histogram, 0, (s->n_histogram_entries + 1) * sizeof(unsigned long long));

	for_each_possible_cpu(cpu) {
		p = &s->stat_percpu[cpu][x];
		shared->tmp.sectors[READ] += ACCESS_ONCE(p->sectors[READ]);
		shared->tmp.sectors[WRITE] += ACCESS_ONCE(p->sectors[WRITE]);
		shared->tmp.ios[READ] += ACCESS_ONCE(p->ios[READ]);
		shared->tmp.ios[WRITE] += ACCESS_ONCE(p->ios[WRITE]);
		shared->tmp.merges[READ] += ACCESS_ONCE(p->merges[READ]);
		shared->tmp.merges[WRITE] += ACCESS_ONCE(p->merges[WRITE]);
		shared->tmp.ticks[READ] += ACCESS_ONCE(p->ticks[READ]);
		shared->tmp.ticks[WRITE] += ACCESS_ONCE(p->ticks[WRITE]);
		shared->tmp.io_ticks[READ] += ACCESS_ONCE(p->io_ticks[READ]);
		shared->tmp.io_ticks[WRITE] += ACCESS_ONCE(p->io_ticks[WRITE]);
		shared->tmp.io_ticks_total += ACCESS_ONCE(p->io_ticks_total);
		shared->tmp.time_in_queue += ACCESS_ONCE(p->time_in_queue);
		if (s->n_histogram_entries) {
			unsigned i;
			for (i = 0; i < s->n_histogram_entries + 1; i++)
				shared->tmp.histogram[i] += ACCESS_ONCE(p->histogram[i]);
		}
	}
}

static void __dm_stat_clear(struct dm_stat *s, size_t idx_start, size_t idx_end,
			    bool init_tmp_percpu_totals)
{
	size_t x;
	struct dm_stat_shared *shared;
	struct dm_stat_percpu *p;

	for (x = idx_start; x < idx_end; x++) {
		shared = &s->stat_shared[x];
		if (init_tmp_percpu_totals)
			__dm_stat_init_temporary_percpu_totals(shared, s, x);
		local_irq_disable();
		p = &s->stat_percpu[smp_processor_id()][x];
		p->sectors[READ] -= shared->tmp.sectors[READ];
		p->sectors[WRITE] -= shared->tmp.sectors[WRITE];
		p->ios[READ] -= shared->tmp.ios[READ];
		p->ios[WRITE] -= shared->tmp.ios[WRITE];
		p->merges[READ] -= shared->tmp.merges[READ];
		p->merges[WRITE] -= shared->tmp.merges[WRITE];
		p->ticks[READ] -= shared->tmp.ticks[READ];
		p->ticks[WRITE] -= shared->tmp.ticks[WRITE];
		p->io_ticks[READ] -= shared->tmp.io_ticks[READ];
		p->io_ticks[WRITE] -= shared->tmp.io_ticks[WRITE];
		p->io_ticks_total -= shared->tmp.io_ticks_total;
		p->time_in_queue -= shared->tmp.time_in_queue;
		local_irq_enable();
		if (s->n_histogram_entries) {
			unsigned i;
			for (i = 0; i < s->n_histogram_entries + 1; i++) {
				local_irq_disable();
				p = &s->stat_percpu[smp_processor_id()][x];
				p->histogram[i] -= shared->tmp.histogram[i];
				local_irq_enable();
			}
		}
	}
}

static int dm_stats_clear(struct dm_stats *stats, int id)
{
	struct dm_stat *s;

	mutex_lock(&stats->mutex);

	s = __dm_stats_find(stats, id);
	if (!s) {
		mutex_unlock(&stats->mutex);
		return -ENOENT;
	}

	__dm_stat_clear(s, 0, s->n_entries, true);

	mutex_unlock(&stats->mutex);

	return 1;
}

/*
 * This is like jiffies_to_msec, but works for 64-bit values.
 */
static unsigned long long dm_jiffies_to_msec64(struct dm_stat *s, unsigned long long j)
{
	unsigned long long result;
	unsigned mult;

	if (s->stat_flags & STAT_PRECISE_TIMESTAMPS)
		return j;

	result = 0;
	if (j)
		result = jiffies_to_msecs(j & 0x3fffff);
	if (j >= 1 << 22) {
		mult = jiffies_to_msecs(1 << 22);
		result += (unsigned long long)mult * (unsigned long long)jiffies_to_msecs((j >> 22) & 0x3fffff);
	}
	if (j >= 1ULL << 44)
		result += (unsigned long long)mult * (unsigned long long)mult * (unsigned long long)jiffies_to_msecs(j >> 44);

	return result;
}

static int dm_stats_print(struct dm_stats *stats, int id,
			  size_t idx_start, size_t idx_len,
			  bool clear, char *result, unsigned maxlen)
{
	unsigned sz = 0;
	struct dm_stat *s;
	size_t x;
	sector_t start, end, step;
	size_t idx_end;
	struct dm_stat_shared *shared;

	/*
	 * Output format:
	 *   <start_sector>+<length> counters
	 */

	mutex_lock(&stats->mutex);

	s = __dm_stats_find(stats, id);
	if (!s) {
		mutex_unlock(&stats->mutex);
		return -ENOENT;
	}

	idx_end = idx_start + idx_len;
	if (idx_end < idx_start ||
	    idx_end > s->n_entries)
		idx_end = s->n_entries;

	if (idx_start > idx_end)
		idx_start = idx_end;

	step = s->step;
	start = s->start + (step * idx_start);

	for (x = idx_start; x < idx_end; x++, start = end) {
		shared = &s->stat_shared[x];
		end = start + step;
		if (unlikely(end > s->end))
			end = s->end;

		__dm_stat_init_temporary_percpu_totals(shared, s, x);

		DMEMIT("%llu+%llu %llu %llu %llu %llu %llu %llu %llu %llu %d %llu %llu %llu %llu",
		       (unsigned long long)start,
		       (unsigned long long)step,
		       shared->tmp.ios[READ],
		       shared->tmp.merges[READ],
		       shared->tmp.sectors[READ],
		       dm_jiffies_to_msec64(s, shared->tmp.ticks[READ]),
		       shared->tmp.ios[WRITE],
		       shared->tmp.merges[WRITE],
		       shared->tmp.sectors[WRITE],
		       dm_jiffies_to_msec64(s, shared->tmp.ticks[WRITE]),
		       dm_stat_in_flight(shared),
		       dm_jiffies_to_msec64(s, shared->tmp.io_ticks_total),
		       dm_jiffies_to_msec64(s, shared->tmp.time_in_queue),
		       dm_jiffies_to_msec64(s, shared->tmp.io_ticks[READ]),
		       dm_jiffies_to_msec64(s, shared->tmp.io_ticks[WRITE]));
		if (s->n_histogram_entries) {
			unsigned i;
			for (i = 0; i < s->n_histogram_entries + 1; i++) {
				DMEMIT("%s%llu", !i ? " " : ":", shared->tmp.histogram[i]);
			}
		}
		DMEMIT("\n");

		if (unlikely(sz + 1 >= maxlen))
			goto buffer_overflow;
	}

	if (clear)
		__dm_stat_clear(s, idx_start, idx_end, false);

buffer_overflow:
	mutex_unlock(&stats->mutex);

	return 1;
}

static int dm_stats_set_aux(struct dm_stats *stats, int id, const char *aux_data)
{
	struct dm_stat *s;
	const char *new_aux_data;

	mutex_lock(&stats->mutex);

	s = __dm_stats_find(stats, id);
	if (!s) {
		mutex_unlock(&stats->mutex);
		return -ENOENT;
	}

	new_aux_data = kstrdup(aux_data, GFP_KERNEL);
	if (!new_aux_data) {
		mutex_unlock(&stats->mutex);
		return -ENOMEM;
	}

	kfree(s->aux_data);
	s->aux_data = new_aux_data;

	mutex_unlock(&stats->mutex);

	return 0;
}

static int parse_histogram(const char *h, unsigned *n_histogram_entries,
			   unsigned long long **histogram_boundaries)
{
	const char *q;
	unsigned n;
	unsigned long long last;

	*n_histogram_entries = 1;
	for (q = h; *q; q++)
		if (*q == ',')
			(*n_histogram_entries)++;

	*histogram_boundaries = kmalloc(*n_histogram_entries * sizeof(unsigned long long), GFP_KERNEL);
	if (!*histogram_boundaries)
		return -ENOMEM;

	n = 0;
	last = 0;
	while (1) {
		unsigned long long hi;
		int s;
		char ch;
		s = sscanf(h, "%llu%c", &hi, &ch);
		if (!s || (s == 2 && ch != ','))
			return -EINVAL;
		if (hi <= last)
			return -EINVAL;
		last = hi;
		(*histogram_boundaries)[n] = hi;
		if (s == 1)
			return 0;
		h = strchr(h, ',') + 1;
		n++;
	}
}

static int message_stats_create(struct mapped_device *md,
				unsigned argc, char **argv,
				char *result, unsigned maxlen)
{
	int r;
	int id;
	char dummy;
	unsigned long long start, end, len, step;
	unsigned divisor;
	const char *program_id, *aux_data;
	unsigned stat_flags = 0;

	unsigned n_histogram_entries = 0;
	unsigned long long *histogram_boundaries = NULL;

	struct dm_arg_set as, as_backup;
	const char *a;
	unsigned feature_args;

	/*
	 * Input format:
	 *   <range> <step> [<extra_parameters> <parameters>] [<program_id> [<aux_data>]]
	 */

	if (argc < 3)
		goto ret_einval;

	as.argc = argc;
	as.argv = argv;
	dm_consume_args(&as, 1);

	a = dm_shift_arg(&as);
	if (!strcmp(a, "-")) {
		start = 0;
		len = dm_get_size(md);
		if (!len)
			len = 1;
	} else if (sscanf(a, "%llu+%llu%c", &start, &len, &dummy) != 2 ||
		   start != (sector_t)start || len != (sector_t)len)
		goto ret_einval;

	end = start + len;
	if (start >= end)
		goto ret_einval;

	a = dm_shift_arg(&as);
	if (sscanf(a, "/%u%c", &divisor, &dummy) == 1) {
		if (!divisor)
			return -EINVAL;
		step = end - start;
		if (do_div(step, divisor))
			step++;
		if (!step)
			step = 1;
	} else if (sscanf(a, "%llu%c", &step, &dummy) != 1 ||
		   step != (sector_t)step || !step)
		goto ret_einval;

	as_backup = as;
	a = dm_shift_arg(&as);
	if (a && sscanf(a, "%u%c", &feature_args, &dummy) == 1) {
		while (feature_args--) {
			a = dm_shift_arg(&as);
			if (!a)
				goto ret_einval;
			if (!strcasecmp(a, "precise_timestamps"))
				stat_flags |= STAT_PRECISE_TIMESTAMPS;
			else if (!strncasecmp(a, "histogram:", 10)) {
				if (n_histogram_entries)
					goto ret_einval;
				if ((r = parse_histogram(a + 10, &n_histogram_entries, &histogram_boundaries)))
					goto ret;
			} else
				goto ret_einval;
		}
	} else {
		as = as_backup;
	}

	program_id = "-";
	aux_data = "-";

	a = dm_shift_arg(&as);
	if (a)
		program_id = a;

	a = dm_shift_arg(&as);
	if (a)
		aux_data = a;

	if (as.argc)
		goto ret_einval;

	/*
	 * If a buffer overflow happens after we created the region,
	 * it's too late (the userspace would retry with a larger
	 * buffer, but the region id that caused the overflow is already
	 * leaked).  So we must detect buffer overflow in advance.
	 */
	snprintf(result, maxlen, "%d", INT_MAX);
	if (dm_message_test_buffer_overflow(result, maxlen)) {
		r = 1;
		goto ret;
	}

	id = dm_stats_create(dm_get_stats(md), start, end, step, stat_flags,
			     n_histogram_entries, histogram_boundaries, program_id, aux_data,
			     dm_internal_suspend_fast, dm_internal_resume_fast, md);
	if (id < 0) {
		r = id;
		goto ret;
	}

	snprintf(result, maxlen, "%d", id);

	r = 1;
	goto ret;

ret_einval:
	r = -EINVAL;
ret:
	kfree(histogram_boundaries);
	return r;
}

static int message_stats_delete(struct mapped_device *md,
				unsigned argc, char **argv)
{
	int id;
	char dummy;

	if (argc != 2)
		return -EINVAL;

	if (sscanf(argv[1], "%d%c", &id, &dummy) != 1 || id < 0)
		return -EINVAL;

	return dm_stats_delete(dm_get_stats(md), id);
}

static int message_stats_clear(struct mapped_device *md,
			       unsigned argc, char **argv)
{
	int id;
	char dummy;

	if (argc != 2)
		return -EINVAL;

	if (sscanf(argv[1], "%d%c", &id, &dummy) != 1 || id < 0)
		return -EINVAL;

	return dm_stats_clear(dm_get_stats(md), id);
}

static int message_stats_list(struct mapped_device *md,
			      unsigned argc, char **argv,
			      char *result, unsigned maxlen)
{
	int r;
	const char *program = NULL;

	if (argc < 1 || argc > 2)
		return -EINVAL;

	if (argc > 1) {
		program = kstrdup(argv[1], GFP_KERNEL);
		if (!program)
			return -ENOMEM;
	}

	r = dm_stats_list(dm_get_stats(md), program, result, maxlen);

	kfree(program);

	return r;
}

static int message_stats_print(struct mapped_device *md,
			       unsigned argc, char **argv, bool clear,
			       char *result, unsigned maxlen)
{
	int id;
	char dummy;
	unsigned long idx_start = 0, idx_len = ULONG_MAX;

	if (argc != 2 && argc != 4)
		return -EINVAL;

	if (sscanf(argv[1], "%d%c", &id, &dummy) != 1 || id < 0)
		return -EINVAL;

	if (argc > 3) {
		if (strcmp(argv[2], "-") &&
		    sscanf(argv[2], "%lu%c", &idx_start, &dummy) != 1)
			return -EINVAL;
		if (strcmp(argv[3], "-") &&
		    sscanf(argv[3], "%lu%c", &idx_len, &dummy) != 1)
			return -EINVAL;
	}

	return dm_stats_print(dm_get_stats(md), id, idx_start, idx_len, clear,
			      result, maxlen);
}

static int message_stats_set_aux(struct mapped_device *md,
				 unsigned argc, char **argv)
{
	int id;
	char dummy;

	if (argc != 3)
		return -EINVAL;

	if (sscanf(argv[1], "%d%c", &id, &dummy) != 1 || id < 0)
		return -EINVAL;

	return dm_stats_set_aux(dm_get_stats(md), id, argv[2]);
}

int dm_stats_message(struct mapped_device *md, unsigned argc, char **argv,
		     char *result, unsigned maxlen)
{
	int r;

	/* All messages here must start with '@' */
	if (!strcasecmp(argv[0], "@stats_create"))
		r = message_stats_create(md, argc, argv, result, maxlen);
	else if (!strcasecmp(argv[0], "@stats_delete"))
		r = message_stats_delete(md, argc, argv);
	else if (!strcasecmp(argv[0], "@stats_clear"))
		r = message_stats_clear(md, argc, argv);
	else if (!strcasecmp(argv[0], "@stats_list"))
		r = message_stats_list(md, argc, argv, result, maxlen);
	else if (!strcasecmp(argv[0], "@stats_print"))
		r = message_stats_print(md, argc, argv, false, result, maxlen);
	else if (!strcasecmp(argv[0], "@stats_print_clear"))
		r = message_stats_print(md, argc, argv, true, result, maxlen);
	else if (!strcasecmp(argv[0], "@stats_set_aux"))
		r = message_stats_set_aux(md, argc, argv);
	else
		return 2; /* this wasn't a stats message */

	if (r == -EINVAL)
		DMWARN("Invalid parameters for message %s", argv[0]);

	return r;
}

int __init dm_statistics_init(void)
{
	shared_memory_amount = 0;
	dm_stat_need_rcu_barrier = 0;
	return 0;
}

void dm_statistics_exit(void)
{
	if (dm_stat_need_rcu_barrier)
		rcu_barrier();
	if (WARN_ON(shared_memory_amount))
		DMCRIT("shared_memory_amount leaked: %lu", shared_memory_amount);
}

module_param_named(stats_current_allocated_bytes, shared_memory_amount, ulong, S_IRUGO);
MODULE_PARM_DESC(stats_current_allocated_bytes, "Memory currently used by statistics");