sch_htb.c 42.6 KB
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 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628
/*
 * net/sched/sch_htb.c	Hierarchical token bucket, feed tree version
 *
 *		This program is free software; you can redistribute it and/or
 *		modify it under the terms of the GNU General Public License
 *		as published by the Free Software Foundation; either version
 *		2 of the License, or (at your option) any later version.
 *
 * Authors:	Martin Devera, <devik@cdi.cz>
 *
 * Credits (in time order) for older HTB versions:
 *              Stef Coene <stef.coene@docum.org>
 *			HTB support at LARTC mailing list
 *		Ondrej Kraus, <krauso@barr.cz>
 *			found missing INIT_QDISC(htb)
 *		Vladimir Smelhaus, Aamer Akhter, Bert Hubert
 *			helped a lot to locate nasty class stall bug
 *		Andi Kleen, Jamal Hadi, Bert Hubert
 *			code review and helpful comments on shaping
 *		Tomasz Wrona, <tw@eter.tym.pl>
 *			created test case so that I was able to fix nasty bug
 *		Wilfried Weissmann
 *			spotted bug in dequeue code and helped with fix
 *		Jiri Fojtasek
 *			fixed requeue routine
 *		and many others. thanks.
 */
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/skbuff.h>
#include <linux/list.h>
#include <linux/compiler.h>
#include <linux/rbtree.h>
#include <linux/workqueue.h>
#include <linux/slab.h>
#include <net/netlink.h>
#include <net/sch_generic.h>
#include <net/pkt_sched.h>

/* HTB algorithm.
    Author: devik@cdi.cz
    ========================================================================
    HTB is like TBF with multiple classes. It is also similar to CBQ because
    it allows to assign priority to each class in hierarchy.
    In fact it is another implementation of Floyd's formal sharing.

    Levels:
    Each class is assigned level. Leaf has ALWAYS level 0 and root
    classes have level TC_HTB_MAXDEPTH-1. Interior nodes has level
    one less than their parent.
*/

static int htb_hysteresis __read_mostly = 0; /* whether to use mode hysteresis for speedup */
#define HTB_VER 0x30011		/* major must be matched with number suplied by TC as version */

#if HTB_VER >> 16 != TC_HTB_PROTOVER
#error "Mismatched sch_htb.c and pkt_sch.h"
#endif

/* Module parameter and sysfs export */
module_param    (htb_hysteresis, int, 0640);
MODULE_PARM_DESC(htb_hysteresis, "Hysteresis mode, less CPU load, less accurate");

static int htb_rate_est = 0; /* htb classes have a default rate estimator */
module_param(htb_rate_est, int, 0640);
MODULE_PARM_DESC(htb_rate_est, "setup a default rate estimator (4sec 16sec) for htb classes");

/* used internaly to keep status of single class */
enum htb_cmode {
	HTB_CANT_SEND,		/* class can't send and can't borrow */
	HTB_MAY_BORROW,		/* class can't send but may borrow */
	HTB_CAN_SEND		/* class can send */
};

struct htb_prio {
	union {
		struct rb_root	row;
		struct rb_root	feed;
	};
	struct rb_node	*ptr;
	/* When class changes from state 1->2 and disconnects from
	 * parent's feed then we lost ptr value and start from the
	 * first child again. Here we store classid of the
	 * last valid ptr (used when ptr is NULL).
	 */
	u32		last_ptr_id;
};

/* interior & leaf nodes; props specific to leaves are marked L:
 * To reduce false sharing, place mostly read fields at beginning,
 * and mostly written ones at the end.
 */
struct htb_class {
	struct Qdisc_class_common common;
	struct psched_ratecfg	rate;
	struct psched_ratecfg	ceil;
	s64			buffer, cbuffer;/* token bucket depth/rate */
	s64			mbuffer;	/* max wait time */
	u32			prio;		/* these two are used only by leaves... */
	int			quantum;	/* but stored for parent-to-leaf return */

	struct tcf_proto	*filter_list;	/* class attached filters */
	int			filter_cnt;
	int			refcnt;		/* usage count of this class */

	int			level;		/* our level (see above) */
	unsigned int		children;
	struct htb_class	*parent;	/* parent class */

	struct gnet_stats_rate_est64 rate_est;

	/*
	 * Written often fields
	 */
	struct gnet_stats_basic_packed bstats;
	struct gnet_stats_queue	qstats;
	struct tc_htb_xstats	xstats;	/* our special stats */

	/* token bucket parameters */
	s64			tokens, ctokens;/* current number of tokens */
	s64			t_c;		/* checkpoint time */

	union {
		struct htb_class_leaf {
			struct list_head drop_list;
			int		deficit[TC_HTB_MAXDEPTH];
			struct Qdisc	*q;
		} leaf;
		struct htb_class_inner {
			struct htb_prio clprio[TC_HTB_NUMPRIO];
		} inner;
	} un;
	s64			pq_key;

	int			prio_activity;	/* for which prios are we active */
	enum htb_cmode		cmode;		/* current mode of the class */
	struct rb_node		pq_node;	/* node for event queue */
	struct rb_node		node[TC_HTB_NUMPRIO];	/* node for self or feed tree */
};

struct htb_level {
	struct rb_root	wait_pq;
	struct htb_prio hprio[TC_HTB_NUMPRIO];
};

struct htb_sched {
	struct Qdisc_class_hash clhash;
	int			defcls;		/* class where unclassified flows go to */
	int			rate2quantum;	/* quant = rate / rate2quantum */

	/* filters for qdisc itself */
	struct tcf_proto	*filter_list;

#define HTB_WARN_TOOMANYEVENTS	0x1
	unsigned int		warned;	/* only one warning */
	int			direct_qlen;
	struct work_struct	work;

	/* non shaped skbs; let them go directly thru */
	struct sk_buff_head	direct_queue;
	long			direct_pkts;

	struct qdisc_watchdog	watchdog;

	s64			now;	/* cached dequeue time */
	struct list_head	drops[TC_HTB_NUMPRIO];/* active leaves (for drops) */

	/* time of nearest event per level (row) */
	s64			near_ev_cache[TC_HTB_MAXDEPTH];

	int			row_mask[TC_HTB_MAXDEPTH];

	struct htb_level	hlevel[TC_HTB_MAXDEPTH];
};

/* find class in global hash table using given handle */
static inline struct htb_class *htb_find(u32 handle, struct Qdisc *sch)
{
	struct htb_sched *q = qdisc_priv(sch);
	struct Qdisc_class_common *clc;

	clc = qdisc_class_find(&q->clhash, handle);
	if (clc == NULL)
		return NULL;
	return container_of(clc, struct htb_class, common);
}

/**
 * htb_classify - classify a packet into class
 *
 * It returns NULL if the packet should be dropped or -1 if the packet
 * should be passed directly thru. In all other cases leaf class is returned.
 * We allow direct class selection by classid in priority. The we examine
 * filters in qdisc and in inner nodes (if higher filter points to the inner
 * node). If we end up with classid MAJOR:0 we enqueue the skb into special
 * internal fifo (direct). These packets then go directly thru. If we still
 * have no valid leaf we try to use MAJOR:default leaf. It still unsuccessful
 * then finish and return direct queue.
 */
#define HTB_DIRECT ((struct htb_class *)-1L)

static struct htb_class *htb_classify(struct sk_buff *skb, struct Qdisc *sch,
				      int *qerr)
{
	struct htb_sched *q = qdisc_priv(sch);
	struct htb_class *cl;
	struct tcf_result res;
	struct tcf_proto *tcf;
	int result;

	/* allow to select class by setting skb->priority to valid classid;
	 * note that nfmark can be used too by attaching filter fw with no
	 * rules in it
	 */
	if (skb->priority == sch->handle)
		return HTB_DIRECT;	/* X:0 (direct flow) selected */
	cl = htb_find(skb->priority, sch);
	if (cl) {
		if (cl->level == 0)
			return cl;
		/* Start with inner filter chain if a non-leaf class is selected */
		tcf = cl->filter_list;
	} else {
		tcf = q->filter_list;
	}

	*qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
	while (tcf && (result = tc_classify(skb, tcf, &res)) >= 0) {
#ifdef CONFIG_NET_CLS_ACT
		switch (result) {
		case TC_ACT_QUEUED:
		case TC_ACT_STOLEN:
			*qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
		case TC_ACT_SHOT:
			return NULL;
		}
#endif
		cl = (void *)res.class;
		if (!cl) {
			if (res.classid == sch->handle)
				return HTB_DIRECT;	/* X:0 (direct flow) */
			cl = htb_find(res.classid, sch);
			if (!cl)
				break;	/* filter selected invalid classid */
		}
		if (!cl->level)
			return cl;	/* we hit leaf; return it */

		/* we have got inner class; apply inner filter chain */
		tcf = cl->filter_list;
	}
	/* classification failed; try to use default class */
	cl = htb_find(TC_H_MAKE(TC_H_MAJ(sch->handle), q->defcls), sch);
	if (!cl || cl->level)
		return HTB_DIRECT;	/* bad default .. this is safe bet */
	return cl;
}

/**
 * htb_add_to_id_tree - adds class to the round robin list
 *
 * Routine adds class to the list (actually tree) sorted by classid.
 * Make sure that class is not already on such list for given prio.
 */
static void htb_add_to_id_tree(struct rb_root *root,
			       struct htb_class *cl, int prio)
{
	struct rb_node **p = &root->rb_node, *parent = NULL;

	while (*p) {
		struct htb_class *c;
		parent = *p;
		c = rb_entry(parent, struct htb_class, node[prio]);

		if (cl->common.classid > c->common.classid)
			p = &parent->rb_right;
		else
			p = &parent->rb_left;
	}
	rb_link_node(&cl->node[prio], parent, p);
	rb_insert_color(&cl->node[prio], root);
}

/**
 * htb_add_to_wait_tree - adds class to the event queue with delay
 *
 * The class is added to priority event queue to indicate that class will
 * change its mode in cl->pq_key microseconds. Make sure that class is not
 * already in the queue.
 */
static void htb_add_to_wait_tree(struct htb_sched *q,
				 struct htb_class *cl, s64 delay)
{
	struct rb_node **p = &q->hlevel[cl->level].wait_pq.rb_node, *parent = NULL;

	cl->pq_key = q->now + delay;
	if (cl->pq_key == q->now)
		cl->pq_key++;

	/* update the nearest event cache */
	if (q->near_ev_cache[cl->level] > cl->pq_key)
		q->near_ev_cache[cl->level] = cl->pq_key;

	while (*p) {
		struct htb_class *c;
		parent = *p;
		c = rb_entry(parent, struct htb_class, pq_node);
		if (cl->pq_key >= c->pq_key)
			p = &parent->rb_right;
		else
			p = &parent->rb_left;
	}
	rb_link_node(&cl->pq_node, parent, p);
	rb_insert_color(&cl->pq_node, &q->hlevel[cl->level].wait_pq);
}

/**
 * htb_next_rb_node - finds next node in binary tree
 *
 * When we are past last key we return NULL.
 * Average complexity is 2 steps per call.
 */
static inline void htb_next_rb_node(struct rb_node **n)
{
	*n = rb_next(*n);
}

/**
 * htb_add_class_to_row - add class to its row
 *
 * The class is added to row at priorities marked in mask.
 * It does nothing if mask == 0.
 */
static inline void htb_add_class_to_row(struct htb_sched *q,
					struct htb_class *cl, int mask)
{
	q->row_mask[cl->level] |= mask;
	while (mask) {
		int prio = ffz(~mask);
		mask &= ~(1 << prio);
		htb_add_to_id_tree(&q->hlevel[cl->level].hprio[prio].row, cl, prio);
	}
}

/* If this triggers, it is a bug in this code, but it need not be fatal */
static void htb_safe_rb_erase(struct rb_node *rb, struct rb_root *root)
{
	if (RB_EMPTY_NODE(rb)) {
		WARN_ON(1);
	} else {
		rb_erase(rb, root);
		RB_CLEAR_NODE(rb);
	}
}


/**
 * htb_remove_class_from_row - removes class from its row
 *
 * The class is removed from row at priorities marked in mask.
 * It does nothing if mask == 0.
 */
static inline void htb_remove_class_from_row(struct htb_sched *q,
						 struct htb_class *cl, int mask)
{
	int m = 0;
	struct htb_level *hlevel = &q->hlevel[cl->level];

	while (mask) {
		int prio = ffz(~mask);
		struct htb_prio *hprio = &hlevel->hprio[prio];

		mask &= ~(1 << prio);
		if (hprio->ptr == cl->node + prio)
			htb_next_rb_node(&hprio->ptr);

		htb_safe_rb_erase(cl->node + prio, &hprio->row);
		if (!hprio->row.rb_node)
			m |= 1 << prio;
	}
	q->row_mask[cl->level] &= ~m;
}

/**
 * htb_activate_prios - creates active classe's feed chain
 *
 * The class is connected to ancestors and/or appropriate rows
 * for priorities it is participating on. cl->cmode must be new
 * (activated) mode. It does nothing if cl->prio_activity == 0.
 */
static void htb_activate_prios(struct htb_sched *q, struct htb_class *cl)
{
	struct htb_class *p = cl->parent;
	long m, mask = cl->prio_activity;

	while (cl->cmode == HTB_MAY_BORROW && p && mask) {
		m = mask;
		while (m) {
			int prio = ffz(~m);
			m &= ~(1 << prio);

			if (p->un.inner.clprio[prio].feed.rb_node)
				/* parent already has its feed in use so that
				 * reset bit in mask as parent is already ok
				 */
				mask &= ~(1 << prio);

			htb_add_to_id_tree(&p->un.inner.clprio[prio].feed, cl, prio);
		}
		p->prio_activity |= mask;
		cl = p;
		p = cl->parent;

	}
	if (cl->cmode == HTB_CAN_SEND && mask)
		htb_add_class_to_row(q, cl, mask);
}

/**
 * htb_deactivate_prios - remove class from feed chain
 *
 * cl->cmode must represent old mode (before deactivation). It does
 * nothing if cl->prio_activity == 0. Class is removed from all feed
 * chains and rows.
 */
static void htb_deactivate_prios(struct htb_sched *q, struct htb_class *cl)
{
	struct htb_class *p = cl->parent;
	long m, mask = cl->prio_activity;

	while (cl->cmode == HTB_MAY_BORROW && p && mask) {
		m = mask;
		mask = 0;
		while (m) {
			int prio = ffz(~m);
			m &= ~(1 << prio);

			if (p->un.inner.clprio[prio].ptr == cl->node + prio) {
				/* we are removing child which is pointed to from
				 * parent feed - forget the pointer but remember
				 * classid
				 */
				p->un.inner.clprio[prio].last_ptr_id = cl->common.classid;
				p->un.inner.clprio[prio].ptr = NULL;
			}

			htb_safe_rb_erase(cl->node + prio,
					  &p->un.inner.clprio[prio].feed);

			if (!p->un.inner.clprio[prio].feed.rb_node)
				mask |= 1 << prio;
		}

		p->prio_activity &= ~mask;
		cl = p;
		p = cl->parent;

	}
	if (cl->cmode == HTB_CAN_SEND && mask)
		htb_remove_class_from_row(q, cl, mask);
}

static inline s64 htb_lowater(const struct htb_class *cl)
{
	if (htb_hysteresis)
		return cl->cmode != HTB_CANT_SEND ? -cl->cbuffer : 0;
	else
		return 0;
}
static inline s64 htb_hiwater(const struct htb_class *cl)
{
	if (htb_hysteresis)
		return cl->cmode == HTB_CAN_SEND ? -cl->buffer : 0;
	else
		return 0;
}


/**
 * htb_class_mode - computes and returns current class mode
 *
 * It computes cl's mode at time cl->t_c+diff and returns it. If mode
 * is not HTB_CAN_SEND then cl->pq_key is updated to time difference
 * from now to time when cl will change its state.
 * Also it is worth to note that class mode doesn't change simply
 * at cl->{c,}tokens == 0 but there can rather be hysteresis of
 * 0 .. -cl->{c,}buffer range. It is meant to limit number of
 * mode transitions per time unit. The speed gain is about 1/6.
 */
static inline enum htb_cmode
htb_class_mode(struct htb_class *cl, s64 *diff)
{
	s64 toks;

	if ((toks = (cl->ctokens + *diff)) < htb_lowater(cl)) {
		*diff = -toks;
		return HTB_CANT_SEND;
	}

	if ((toks = (cl->tokens + *diff)) >= htb_hiwater(cl))
		return HTB_CAN_SEND;

	*diff = -toks;
	return HTB_MAY_BORROW;
}

/**
 * htb_change_class_mode - changes classe's mode
 *
 * This should be the only way how to change classe's mode under normal
 * cirsumstances. Routine will update feed lists linkage, change mode
 * and add class to the wait event queue if appropriate. New mode should
 * be different from old one and cl->pq_key has to be valid if changing
 * to mode other than HTB_CAN_SEND (see htb_add_to_wait_tree).
 */
static void
htb_change_class_mode(struct htb_sched *q, struct htb_class *cl, s64 *diff)
{
	enum htb_cmode new_mode = htb_class_mode(cl, diff);

	if (new_mode == cl->cmode)
		return;

	if (cl->prio_activity) {	/* not necessary: speed optimization */
		if (cl->cmode != HTB_CANT_SEND)
			htb_deactivate_prios(q, cl);
		cl->cmode = new_mode;
		if (new_mode != HTB_CANT_SEND)
			htb_activate_prios(q, cl);
	} else
		cl->cmode = new_mode;
}

/**
 * htb_activate - inserts leaf cl into appropriate active feeds
 *
 * Routine learns (new) priority of leaf and activates feed chain
 * for the prio. It can be called on already active leaf safely.
 * It also adds leaf into droplist.
 */
static inline void htb_activate(struct htb_sched *q, struct htb_class *cl)
{
	WARN_ON(cl->level || !cl->un.leaf.q || !cl->un.leaf.q->q.qlen);

	if (!cl->prio_activity) {
		cl->prio_activity = 1 << cl->prio;
		htb_activate_prios(q, cl);
		list_add_tail(&cl->un.leaf.drop_list,
			      q->drops + cl->prio);
	}
}

/**
 * htb_deactivate - remove leaf cl from active feeds
 *
 * Make sure that leaf is active. In the other words it can't be called
 * with non-active leaf. It also removes class from the drop list.
 */
static inline void htb_deactivate(struct htb_sched *q, struct htb_class *cl)
{
	WARN_ON(!cl->prio_activity);

	htb_deactivate_prios(q, cl);
	cl->prio_activity = 0;
	list_del_init(&cl->un.leaf.drop_list);
}

static int htb_enqueue(struct sk_buff *skb, struct Qdisc *sch)
{
	int uninitialized_var(ret);
	struct htb_sched *q = qdisc_priv(sch);
	struct htb_class *cl = htb_classify(skb, sch, &ret);

	if (cl == HTB_DIRECT) {
		/* enqueue to helper queue */
		if (q->direct_queue.qlen < q->direct_qlen) {
			__skb_queue_tail(&q->direct_queue, skb);
			q->direct_pkts++;
		} else {
			return qdisc_drop(skb, sch);
		}
#ifdef CONFIG_NET_CLS_ACT
	} else if (!cl) {
		if (ret & __NET_XMIT_BYPASS)
			sch->qstats.drops++;
		kfree_skb(skb);
		return ret;
#endif
	} else if ((ret = qdisc_enqueue(skb, cl->un.leaf.q)) != NET_XMIT_SUCCESS) {
		if (net_xmit_drop_count(ret)) {
			sch->qstats.drops++;
			cl->qstats.drops++;
		}
		return ret;
	} else {
		htb_activate(q, cl);
	}

	sch->q.qlen++;
	return NET_XMIT_SUCCESS;
}

static inline void htb_accnt_tokens(struct htb_class *cl, int bytes, s64 diff)
{
	s64 toks = diff + cl->tokens;

	if (toks > cl->buffer)
		toks = cl->buffer;
	toks -= (s64) psched_l2t_ns(&cl->rate, bytes);
	if (toks <= -cl->mbuffer)
		toks = 1 - cl->mbuffer;

	cl->tokens = toks;
}

static inline void htb_accnt_ctokens(struct htb_class *cl, int bytes, s64 diff)
{
	s64 toks = diff + cl->ctokens;

	if (toks > cl->cbuffer)
		toks = cl->cbuffer;
	toks -= (s64) psched_l2t_ns(&cl->ceil, bytes);
	if (toks <= -cl->mbuffer)
		toks = 1 - cl->mbuffer;

	cl->ctokens = toks;
}

/**
 * htb_charge_class - charges amount "bytes" to leaf and ancestors
 *
 * Routine assumes that packet "bytes" long was dequeued from leaf cl
 * borrowing from "level". It accounts bytes to ceil leaky bucket for
 * leaf and all ancestors and to rate bucket for ancestors at levels
 * "level" and higher. It also handles possible change of mode resulting
 * from the update. Note that mode can also increase here (MAY_BORROW to
 * CAN_SEND) because we can use more precise clock that event queue here.
 * In such case we remove class from event queue first.
 */
static void htb_charge_class(struct htb_sched *q, struct htb_class *cl,
			     int level, struct sk_buff *skb)
{
	int bytes = qdisc_pkt_len(skb);
	enum htb_cmode old_mode;
	s64 diff;

	while (cl) {
		diff = min_t(s64, q->now - cl->t_c, cl->mbuffer);
		if (cl->level >= level) {
			if (cl->level == level)
				cl->xstats.lends++;
			htb_accnt_tokens(cl, bytes, diff);
		} else {
			cl->xstats.borrows++;
			cl->tokens += diff;	/* we moved t_c; update tokens */
		}
		htb_accnt_ctokens(cl, bytes, diff);
		cl->t_c = q->now;

		old_mode = cl->cmode;
		diff = 0;
		htb_change_class_mode(q, cl, &diff);
		if (old_mode != cl->cmode) {
			if (old_mode != HTB_CAN_SEND)
				htb_safe_rb_erase(&cl->pq_node, &q->hlevel[cl->level].wait_pq);
			if (cl->cmode != HTB_CAN_SEND)
				htb_add_to_wait_tree(q, cl, diff);
		}

		/* update basic stats except for leaves which are already updated */
		if (cl->level)
			bstats_update(&cl->bstats, skb);

		cl = cl->parent;
	}
}

/**
 * htb_do_events - make mode changes to classes at the level
 *
 * Scans event queue for pending events and applies them. Returns time of
 * next pending event (0 for no event in pq, q->now for too many events).
 * Note: Applied are events whose have cl->pq_key <= q->now.
 */
static s64 htb_do_events(struct htb_sched *q, const int level,
			 unsigned long start)
{
	/* don't run for longer than 2 jiffies; 2 is used instead of
	 * 1 to simplify things when jiffy is going to be incremented
	 * too soon
	 */
	unsigned long stop_at = start + 2;
	struct rb_root *wait_pq = &q->hlevel[level].wait_pq;

	while (time_before(jiffies, stop_at)) {
		struct htb_class *cl;
		s64 diff;
		struct rb_node *p = rb_first(wait_pq);

		if (!p)
			return 0;

		cl = rb_entry(p, struct htb_class, pq_node);
		if (cl->pq_key > q->now)
			return cl->pq_key;

		htb_safe_rb_erase(p, wait_pq);
		diff = min_t(s64, q->now - cl->t_c, cl->mbuffer);
		htb_change_class_mode(q, cl, &diff);
		if (cl->cmode != HTB_CAN_SEND)
			htb_add_to_wait_tree(q, cl, diff);
	}

	/* too much load - let's continue after a break for scheduling */
	if (!(q->warned & HTB_WARN_TOOMANYEVENTS)) {
		pr_warn("htb: too many events!\n");
		q->warned |= HTB_WARN_TOOMANYEVENTS;
	}

	return q->now;
}

/* Returns class->node+prio from id-tree where classe's id is >= id. NULL
 * is no such one exists.
 */
static struct rb_node *htb_id_find_next_upper(int prio, struct rb_node *n,
					      u32 id)
{
	struct rb_node *r = NULL;
	while (n) {
		struct htb_class *cl =
		    rb_entry(n, struct htb_class, node[prio]);

		if (id > cl->common.classid) {
			n = n->rb_right;
		} else if (id < cl->common.classid) {
			r = n;
			n = n->rb_left;
		} else {
			return n;
		}
	}
	return r;
}

/**
 * htb_lookup_leaf - returns next leaf class in DRR order
 *
 * Find leaf where current feed pointers points to.
 */
static struct htb_class *htb_lookup_leaf(struct htb_prio *hprio, const int prio)
{
	int i;
	struct {
		struct rb_node *root;
		struct rb_node **pptr;
		u32 *pid;
	} stk[TC_HTB_MAXDEPTH], *sp = stk;

	BUG_ON(!hprio->row.rb_node);
	sp->root = hprio->row.rb_node;
	sp->pptr = &hprio->ptr;
	sp->pid = &hprio->last_ptr_id;

	for (i = 0; i < 65535; i++) {
		if (!*sp->pptr && *sp->pid) {
			/* ptr was invalidated but id is valid - try to recover
			 * the original or next ptr
			 */
			*sp->pptr =
			    htb_id_find_next_upper(prio, sp->root, *sp->pid);
		}
		*sp->pid = 0;	/* ptr is valid now so that remove this hint as it
				 * can become out of date quickly
				 */
		if (!*sp->pptr) {	/* we are at right end; rewind & go up */
			*sp->pptr = sp->root;
			while ((*sp->pptr)->rb_left)
				*sp->pptr = (*sp->pptr)->rb_left;
			if (sp > stk) {
				sp--;
				if (!*sp->pptr) {
					WARN_ON(1);
					return NULL;
				}
				htb_next_rb_node(sp->pptr);
			}
		} else {
			struct htb_class *cl;
			struct htb_prio *clp;

			cl = rb_entry(*sp->pptr, struct htb_class, node[prio]);
			if (!cl->level)
				return cl;
			clp = &cl->un.inner.clprio[prio];
			(++sp)->root = clp->feed.rb_node;
			sp->pptr = &clp->ptr;
			sp->pid = &clp->last_ptr_id;
		}
	}
	WARN_ON(1);
	return NULL;
}

/* dequeues packet at given priority and level; call only if
 * you are sure that there is active class at prio/level
 */
static struct sk_buff *htb_dequeue_tree(struct htb_sched *q, const int prio,
					const int level)
{
	struct sk_buff *skb = NULL;
	struct htb_class *cl, *start;
	struct htb_level *hlevel = &q->hlevel[level];
	struct htb_prio *hprio = &hlevel->hprio[prio];

	/* look initial class up in the row */
	start = cl = htb_lookup_leaf(hprio, prio);

	do {
next:
		if (unlikely(!cl))
			return NULL;

		/* class can be empty - it is unlikely but can be true if leaf
		 * qdisc drops packets in enqueue routine or if someone used
		 * graft operation on the leaf since last dequeue;
		 * simply deactivate and skip such class
		 */
		if (unlikely(cl->un.leaf.q->q.qlen == 0)) {
			struct htb_class *next;
			htb_deactivate(q, cl);

			/* row/level might become empty */
			if ((q->row_mask[level] & (1 << prio)) == 0)
				return NULL;

			next = htb_lookup_leaf(hprio, prio);

			if (cl == start)	/* fix start if we just deleted it */
				start = next;
			cl = next;
			goto next;
		}

		skb = cl->un.leaf.q->dequeue(cl->un.leaf.q);
		if (likely(skb != NULL))
			break;

		qdisc_warn_nonwc("htb", cl->un.leaf.q);
		htb_next_rb_node(level ? &cl->parent->un.inner.clprio[prio].ptr:
					 &q->hlevel[0].hprio[prio].ptr);
		cl = htb_lookup_leaf(hprio, prio);

	} while (cl != start);

	if (likely(skb != NULL)) {
		bstats_update(&cl->bstats, skb);
		cl->un.leaf.deficit[level] -= qdisc_pkt_len(skb);
		if (cl->un.leaf.deficit[level] < 0) {
			cl->un.leaf.deficit[level] += cl->quantum;
			htb_next_rb_node(level ? &cl->parent->un.inner.clprio[prio].ptr :
						 &q->hlevel[0].hprio[prio].ptr);
		}
		/* this used to be after charge_class but this constelation
		 * gives us slightly better performance
		 */
		if (!cl->un.leaf.q->q.qlen)
			htb_deactivate(q, cl);
		htb_charge_class(q, cl, level, skb);
	}
	return skb;
}

static struct sk_buff *htb_dequeue(struct Qdisc *sch)
{
	struct sk_buff *skb;
	struct htb_sched *q = qdisc_priv(sch);
	int level;
	s64 next_event;
	unsigned long start_at;

	/* try to dequeue direct packets as high prio (!) to minimize cpu work */
	skb = __skb_dequeue(&q->direct_queue);
	if (skb != NULL) {
ok:
		qdisc_bstats_update(sch, skb);
		qdisc_unthrottled(sch);
		sch->q.qlen--;
		return skb;
	}

	if (!sch->q.qlen)
		goto fin;
	q->now = ktime_to_ns(ktime_get());
	start_at = jiffies;

	next_event = q->now + 5LLU * NSEC_PER_SEC;

	for (level = 0; level < TC_HTB_MAXDEPTH; level++) {
		/* common case optimization - skip event handler quickly */
		int m;
		s64 event = q->near_ev_cache[level];

		if (q->now >= event) {
			event = htb_do_events(q, level, start_at);
			if (!event)
				event = q->now + NSEC_PER_SEC;
			q->near_ev_cache[level] = event;
		}

		if (next_event > event)
			next_event = event;

		m = ~q->row_mask[level];
		while (m != (int)(-1)) {
			int prio = ffz(m);

			m |= 1 << prio;
			skb = htb_dequeue_tree(q, prio, level);
			if (likely(skb != NULL))
				goto ok;
		}
	}
	sch->qstats.overlimits++;
	if (likely(next_event > q->now)) {
		if (!test_bit(__QDISC_STATE_DEACTIVATED,
			      &qdisc_root_sleeping(q->watchdog.qdisc)->state)) {
			ktime_t time = ns_to_ktime(next_event);
			qdisc_throttled(q->watchdog.qdisc);
			hrtimer_start(&q->watchdog.timer, time,
				      HRTIMER_MODE_ABS);
		}
	} else {
		schedule_work(&q->work);
	}
fin:
	return skb;
}

/* try to drop from each class (by prio) until one succeed */
static unsigned int htb_drop(struct Qdisc *sch)
{
	struct htb_sched *q = qdisc_priv(sch);
	int prio;

	for (prio = TC_HTB_NUMPRIO - 1; prio >= 0; prio--) {
		struct list_head *p;
		list_for_each(p, q->drops + prio) {
			struct htb_class *cl = list_entry(p, struct htb_class,
							  un.leaf.drop_list);
			unsigned int len;
			if (cl->un.leaf.q->ops->drop &&
			    (len = cl->un.leaf.q->ops->drop(cl->un.leaf.q))) {
				sch->q.qlen--;
				if (!cl->un.leaf.q->q.qlen)
					htb_deactivate(q, cl);
				return len;
			}
		}
	}
	return 0;
}

/* reset all classes */
/* always caled under BH & queue lock */
static void htb_reset(struct Qdisc *sch)
{
	struct htb_sched *q = qdisc_priv(sch);
	struct htb_class *cl;
	unsigned int i;

	for (i = 0; i < q->clhash.hashsize; i++) {
		hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode) {
			if (cl->level)
				memset(&cl->un.inner, 0, sizeof(cl->un.inner));
			else {
				if (cl->un.leaf.q)
					qdisc_reset(cl->un.leaf.q);
				INIT_LIST_HEAD(&cl->un.leaf.drop_list);
			}
			cl->prio_activity = 0;
			cl->cmode = HTB_CAN_SEND;

		}
	}
	qdisc_watchdog_cancel(&q->watchdog);
	__skb_queue_purge(&q->direct_queue);
	sch->q.qlen = 0;
	memset(q->hlevel, 0, sizeof(q->hlevel));
	memset(q->row_mask, 0, sizeof(q->row_mask));
	for (i = 0; i < TC_HTB_NUMPRIO; i++)
		INIT_LIST_HEAD(q->drops + i);
}

static const struct nla_policy htb_policy[TCA_HTB_MAX + 1] = {
	[TCA_HTB_PARMS]	= { .len = sizeof(struct tc_htb_opt) },
	[TCA_HTB_INIT]	= { .len = sizeof(struct tc_htb_glob) },
	[TCA_HTB_CTAB]	= { .type = NLA_BINARY, .len = TC_RTAB_SIZE },
	[TCA_HTB_RTAB]	= { .type = NLA_BINARY, .len = TC_RTAB_SIZE },
	[TCA_HTB_DIRECT_QLEN] = { .type = NLA_U32 },
	[TCA_HTB_RATE64] = { .type = NLA_U64 },
	[TCA_HTB_CEIL64] = { .type = NLA_U64 },
};

static void htb_work_func(struct work_struct *work)
{
	struct htb_sched *q = container_of(work, struct htb_sched, work);
	struct Qdisc *sch = q->watchdog.qdisc;

	__netif_schedule(qdisc_root(sch));
}

static int htb_init(struct Qdisc *sch, struct nlattr *opt)
{
	struct htb_sched *q = qdisc_priv(sch);
	struct nlattr *tb[TCA_HTB_MAX + 1];
	struct tc_htb_glob *gopt;
	int err;
	int i;

	if (!opt)
		return -EINVAL;

	err = nla_parse_nested(tb, TCA_HTB_MAX, opt, htb_policy);
	if (err < 0)
		return err;

	if (!tb[TCA_HTB_INIT])
		return -EINVAL;

	gopt = nla_data(tb[TCA_HTB_INIT]);
	if (gopt->version != HTB_VER >> 16)
		return -EINVAL;

	err = qdisc_class_hash_init(&q->clhash);
	if (err < 0)
		return err;
	for (i = 0; i < TC_HTB_NUMPRIO; i++)
		INIT_LIST_HEAD(q->drops + i);

	qdisc_watchdog_init(&q->watchdog, sch);
	INIT_WORK(&q->work, htb_work_func);
	skb_queue_head_init(&q->direct_queue);

	if (tb[TCA_HTB_DIRECT_QLEN])
		q->direct_qlen = nla_get_u32(tb[TCA_HTB_DIRECT_QLEN]);
	else {
		q->direct_qlen = qdisc_dev(sch)->tx_queue_len;
		if (q->direct_qlen < 2)	/* some devices have zero tx_queue_len */
			q->direct_qlen = 2;
	}
	if ((q->rate2quantum = gopt->rate2quantum) < 1)
		q->rate2quantum = 1;
	q->defcls = gopt->defcls;

	return 0;
}

static int htb_dump(struct Qdisc *sch, struct sk_buff *skb)
{
	spinlock_t *root_lock = qdisc_root_sleeping_lock(sch);
	struct htb_sched *q = qdisc_priv(sch);
	struct nlattr *nest;
	struct tc_htb_glob gopt;

	spin_lock_bh(root_lock);

	gopt.direct_pkts = q->direct_pkts;
	gopt.version = HTB_VER;
	gopt.rate2quantum = q->rate2quantum;
	gopt.defcls = q->defcls;
	gopt.debug = 0;

	nest = nla_nest_start(skb, TCA_OPTIONS);
	if (nest == NULL)
		goto nla_put_failure;
	if (nla_put(skb, TCA_HTB_INIT, sizeof(gopt), &gopt) ||
	    nla_put_u32(skb, TCA_HTB_DIRECT_QLEN, q->direct_qlen))
		goto nla_put_failure;
	nla_nest_end(skb, nest);

	spin_unlock_bh(root_lock);
	return skb->len;

nla_put_failure:
	spin_unlock_bh(root_lock);
	nla_nest_cancel(skb, nest);
	return -1;
}

static int htb_dump_class(struct Qdisc *sch, unsigned long arg,
			  struct sk_buff *skb, struct tcmsg *tcm)
{
	struct htb_class *cl = (struct htb_class *)arg;
	spinlock_t *root_lock = qdisc_root_sleeping_lock(sch);
	struct nlattr *nest;
	struct tc_htb_opt opt;

	spin_lock_bh(root_lock);
	tcm->tcm_parent = cl->parent ? cl->parent->common.classid : TC_H_ROOT;
	tcm->tcm_handle = cl->common.classid;
	if (!cl->level && cl->un.leaf.q)
		tcm->tcm_info = cl->un.leaf.q->handle;

	nest = nla_nest_start(skb, TCA_OPTIONS);
	if (nest == NULL)
		goto nla_put_failure;

	memset(&opt, 0, sizeof(opt));

	psched_ratecfg_getrate(&opt.rate, &cl->rate);
	opt.buffer = PSCHED_NS2TICKS(cl->buffer);
	psched_ratecfg_getrate(&opt.ceil, &cl->ceil);
	opt.cbuffer = PSCHED_NS2TICKS(cl->cbuffer);
	opt.quantum = cl->quantum;
	opt.prio = cl->prio;
	opt.level = cl->level;
	if (nla_put(skb, TCA_HTB_PARMS, sizeof(opt), &opt))
		goto nla_put_failure;
	if ((cl->rate.rate_bytes_ps >= (1ULL << 32)) &&
	    nla_put_u64(skb, TCA_HTB_RATE64, cl->rate.rate_bytes_ps))
		goto nla_put_failure;
	if ((cl->ceil.rate_bytes_ps >= (1ULL << 32)) &&
	    nla_put_u64(skb, TCA_HTB_CEIL64, cl->ceil.rate_bytes_ps))
		goto nla_put_failure;

	nla_nest_end(skb, nest);
	spin_unlock_bh(root_lock);
	return skb->len;

nla_put_failure:
	spin_unlock_bh(root_lock);
	nla_nest_cancel(skb, nest);
	return -1;
}

static int
htb_dump_class_stats(struct Qdisc *sch, unsigned long arg, struct gnet_dump *d)
{
	struct htb_class *cl = (struct htb_class *)arg;

	if (!cl->level && cl->un.leaf.q)
		cl->qstats.qlen = cl->un.leaf.q->q.qlen;
	cl->xstats.tokens = PSCHED_NS2TICKS(cl->tokens);
	cl->xstats.ctokens = PSCHED_NS2TICKS(cl->ctokens);

	if (gnet_stats_copy_basic(d, &cl->bstats) < 0 ||
	    gnet_stats_copy_rate_est(d, NULL, &cl->rate_est) < 0 ||
	    gnet_stats_copy_queue(d, &cl->qstats) < 0)
		return -1;

	return gnet_stats_copy_app(d, &cl->xstats, sizeof(cl->xstats));
}

static int htb_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
		     struct Qdisc **old)
{
	struct htb_class *cl = (struct htb_class *)arg;

	if (cl->level)
		return -EINVAL;
	if (new == NULL &&
	    (new = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
				     cl->common.classid)) == NULL)
		return -ENOBUFS;

	sch_tree_lock(sch);
	*old = cl->un.leaf.q;
	cl->un.leaf.q = new;
	if (*old != NULL) {
		qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
		qdisc_reset(*old);
	}
	sch_tree_unlock(sch);
	return 0;
}

static struct Qdisc *htb_leaf(struct Qdisc *sch, unsigned long arg)
{
	struct htb_class *cl = (struct htb_class *)arg;
	return !cl->level ? cl->un.leaf.q : NULL;
}

static void htb_qlen_notify(struct Qdisc *sch, unsigned long arg)
{
	struct htb_class *cl = (struct htb_class *)arg;

	if (cl->un.leaf.q->q.qlen == 0)
		htb_deactivate(qdisc_priv(sch), cl);
}

static unsigned long htb_get(struct Qdisc *sch, u32 classid)
{
	struct htb_class *cl = htb_find(classid, sch);
	if (cl)
		cl->refcnt++;
	return (unsigned long)cl;
}

static inline int htb_parent_last_child(struct htb_class *cl)
{
	if (!cl->parent)
		/* the root class */
		return 0;
	if (cl->parent->children > 1)
		/* not the last child */
		return 0;
	return 1;
}

static void htb_parent_to_leaf(struct htb_sched *q, struct htb_class *cl,
			       struct Qdisc *new_q)
{
	struct htb_class *parent = cl->parent;

	WARN_ON(cl->level || !cl->un.leaf.q || cl->prio_activity);

	if (parent->cmode != HTB_CAN_SEND)
		htb_safe_rb_erase(&parent->pq_node,
				  &q->hlevel[parent->level].wait_pq);

	parent->level = 0;
	memset(&parent->un.inner, 0, sizeof(parent->un.inner));
	INIT_LIST_HEAD(&parent->un.leaf.drop_list);
	parent->un.leaf.q = new_q ? new_q : &noop_qdisc;
	parent->tokens = parent->buffer;
	parent->ctokens = parent->cbuffer;
	parent->t_c = ktime_to_ns(ktime_get());
	parent->cmode = HTB_CAN_SEND;
}

static void htb_destroy_class(struct Qdisc *sch, struct htb_class *cl)
{
	if (!cl->level) {
		WARN_ON(!cl->un.leaf.q);
		qdisc_destroy(cl->un.leaf.q);
	}
	gen_kill_estimator(&cl->bstats, &cl->rate_est);
	tcf_destroy_chain(&cl->filter_list);
	kfree(cl);
}

static void htb_destroy(struct Qdisc *sch)
{
	struct htb_sched *q = qdisc_priv(sch);
	struct hlist_node *next;
	struct htb_class *cl;
	unsigned int i;

	cancel_work_sync(&q->work);
	qdisc_watchdog_cancel(&q->watchdog);
	/* This line used to be after htb_destroy_class call below
	 * and surprisingly it worked in 2.4. But it must precede it
	 * because filter need its target class alive to be able to call
	 * unbind_filter on it (without Oops).
	 */
	tcf_destroy_chain(&q->filter_list);

	for (i = 0; i < q->clhash.hashsize; i++) {
		hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode)
			tcf_destroy_chain(&cl->filter_list);
	}
	for (i = 0; i < q->clhash.hashsize; i++) {
		hlist_for_each_entry_safe(cl, next, &q->clhash.hash[i],
					  common.hnode)
			htb_destroy_class(sch, cl);
	}
	qdisc_class_hash_destroy(&q->clhash);
	__skb_queue_purge(&q->direct_queue);
}

static int htb_delete(struct Qdisc *sch, unsigned long arg)
{
	struct htb_sched *q = qdisc_priv(sch);
	struct htb_class *cl = (struct htb_class *)arg;
	unsigned int qlen;
	struct Qdisc *new_q = NULL;
	int last_child = 0;

	/* TODO: why don't allow to delete subtree ? references ? does
	 * tc subsys guarantee us that in htb_destroy it holds no class
	 * refs so that we can remove children safely there ?
	 */
	if (cl->children || cl->filter_cnt)
		return -EBUSY;

	if (!cl->level && htb_parent_last_child(cl)) {
		new_q = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
					  cl->parent->common.classid);
		last_child = 1;
	}

	sch_tree_lock(sch);

	if (!cl->level) {
		qlen = cl->un.leaf.q->q.qlen;
		qdisc_reset(cl->un.leaf.q);
		qdisc_tree_decrease_qlen(cl->un.leaf.q, qlen);
	}

	/* delete from hash and active; remainder in destroy_class */
	qdisc_class_hash_remove(&q->clhash, &cl->common);
	if (cl->parent)
		cl->parent->children--;

	if (cl->prio_activity)
		htb_deactivate(q, cl);

	if (cl->cmode != HTB_CAN_SEND)
		htb_safe_rb_erase(&cl->pq_node,
				  &q->hlevel[cl->level].wait_pq);

	if (last_child)
		htb_parent_to_leaf(q, cl, new_q);

	BUG_ON(--cl->refcnt == 0);
	/*
	 * This shouldn't happen: we "hold" one cops->get() when called
	 * from tc_ctl_tclass; the destroy method is done from cops->put().
	 */

	sch_tree_unlock(sch);
	return 0;
}

static void htb_put(struct Qdisc *sch, unsigned long arg)
{
	struct htb_class *cl = (struct htb_class *)arg;

	if (--cl->refcnt == 0)
		htb_destroy_class(sch, cl);
}

static int htb_change_class(struct Qdisc *sch, u32 classid,
			    u32 parentid, struct nlattr **tca,
			    unsigned long *arg)
{
	int err = -EINVAL;
	struct htb_sched *q = qdisc_priv(sch);
	struct htb_class *cl = (struct htb_class *)*arg, *parent;
	struct nlattr *opt = tca[TCA_OPTIONS];
	struct nlattr *tb[TCA_HTB_MAX + 1];
	struct tc_htb_opt *hopt;
	u64 rate64, ceil64;

	/* extract all subattrs from opt attr */
	if (!opt)
		goto failure;

	err = nla_parse_nested(tb, TCA_HTB_MAX, opt, htb_policy);
	if (err < 0)
		goto failure;

	err = -EINVAL;
	if (tb[TCA_HTB_PARMS] == NULL)
		goto failure;

	parent = parentid == TC_H_ROOT ? NULL : htb_find(parentid, sch);

	hopt = nla_data(tb[TCA_HTB_PARMS]);
	if (!hopt->rate.rate || !hopt->ceil.rate)
		goto failure;

	/* Keeping backward compatible with rate_table based iproute2 tc */
	if (hopt->rate.linklayer == TC_LINKLAYER_UNAWARE)
		qdisc_put_rtab(qdisc_get_rtab(&hopt->rate, tb[TCA_HTB_RTAB]));

	if (hopt->ceil.linklayer == TC_LINKLAYER_UNAWARE)
		qdisc_put_rtab(qdisc_get_rtab(&hopt->ceil, tb[TCA_HTB_CTAB]));

	if (!cl) {		/* new class */
		struct Qdisc *new_q;
		int prio;
		struct {
			struct nlattr		nla;
			struct gnet_estimator	opt;
		} est = {
			.nla = {
				.nla_len	= nla_attr_size(sizeof(est.opt)),
				.nla_type	= TCA_RATE,
			},
			.opt = {
				/* 4s interval, 16s averaging constant */
				.interval	= 2,
				.ewma_log	= 2,
			},
		};

		/* check for valid classid */
		if (!classid || TC_H_MAJ(classid ^ sch->handle) ||
		    htb_find(classid, sch))
			goto failure;

		/* check maximal depth */
		if (parent && parent->parent && parent->parent->level < 2) {
			pr_err("htb: tree is too deep\n");
			goto failure;
		}
		err = -ENOBUFS;
		cl = kzalloc(sizeof(*cl), GFP_KERNEL);
		if (!cl)
			goto failure;

		if (htb_rate_est || tca[TCA_RATE]) {
			err = gen_new_estimator(&cl->bstats, &cl->rate_est,
						qdisc_root_sleeping_lock(sch),
						tca[TCA_RATE] ? : &est.nla);
			if (err) {
				kfree(cl);
				goto failure;
			}
		}

		cl->refcnt = 1;
		cl->children = 0;
		INIT_LIST_HEAD(&cl->un.leaf.drop_list);
		RB_CLEAR_NODE(&cl->pq_node);

		for (prio = 0; prio < TC_HTB_NUMPRIO; prio++)
			RB_CLEAR_NODE(&cl->node[prio]);

		/* create leaf qdisc early because it uses kmalloc(GFP_KERNEL)
		 * so that can't be used inside of sch_tree_lock
		 * -- thanks to Karlis Peisenieks
		 */
		new_q = qdisc_create_dflt(sch->dev_queue,
					  &pfifo_qdisc_ops, classid);
		sch_tree_lock(sch);
		if (parent && !parent->level) {
			unsigned int qlen = parent->un.leaf.q->q.qlen;

			/* turn parent into inner node */
			qdisc_reset(parent->un.leaf.q);
			qdisc_tree_decrease_qlen(parent->un.leaf.q, qlen);
			qdisc_destroy(parent->un.leaf.q);
			if (parent->prio_activity)
				htb_deactivate(q, parent);

			/* remove from evt list because of level change */
			if (parent->cmode != HTB_CAN_SEND) {
				htb_safe_rb_erase(&parent->pq_node, &q->hlevel[0].wait_pq);
				parent->cmode = HTB_CAN_SEND;
			}
			parent->level = (parent->parent ? parent->parent->level
					 : TC_HTB_MAXDEPTH) - 1;
			memset(&parent->un.inner, 0, sizeof(parent->un.inner));
		}
		/* leaf (we) needs elementary qdisc */
		cl->un.leaf.q = new_q ? new_q : &noop_qdisc;

		cl->common.classid = classid;
		cl->parent = parent;

		/* set class to be in HTB_CAN_SEND state */
		cl->tokens = PSCHED_TICKS2NS(hopt->buffer);
		cl->ctokens = PSCHED_TICKS2NS(hopt->cbuffer);
		cl->mbuffer = 60ULL * NSEC_PER_SEC;	/* 1min */
		cl->t_c = ktime_to_ns(ktime_get());
		cl->cmode = HTB_CAN_SEND;

		/* attach to the hash list and parent's family */
		qdisc_class_hash_insert(&q->clhash, &cl->common);
		if (parent)
			parent->children++;
	} else {
		if (tca[TCA_RATE]) {
			err = gen_replace_estimator(&cl->bstats, &cl->rate_est,
						    qdisc_root_sleeping_lock(sch),
						    tca[TCA_RATE]);
			if (err)
				return err;
		}
		sch_tree_lock(sch);
	}

	rate64 = tb[TCA_HTB_RATE64] ? nla_get_u64(tb[TCA_HTB_RATE64]) : 0;

	ceil64 = tb[TCA_HTB_CEIL64] ? nla_get_u64(tb[TCA_HTB_CEIL64]) : 0;

	psched_ratecfg_precompute(&cl->rate, &hopt->rate, rate64);
	psched_ratecfg_precompute(&cl->ceil, &hopt->ceil, ceil64);

	/* it used to be a nasty bug here, we have to check that node
	 * is really leaf before changing cl->un.leaf !
	 */
	if (!cl->level) {
		u64 quantum = cl->rate.rate_bytes_ps;

		do_div(quantum, q->rate2quantum);
		cl->quantum = min_t(u64, quantum, INT_MAX);

		if (!hopt->quantum && cl->quantum < 1000) {
			pr_warn("HTB: quantum of class %X is small. Consider r2q change.\n",
				cl->common.classid);
			cl->quantum = 1000;
		}
		if (!hopt->quantum && cl->quantum > 200000) {
			pr_warn("HTB: quantum of class %X is big. Consider r2q change.\n",
				cl->common.classid);
			cl->quantum = 200000;
		}
		if (hopt->quantum)
			cl->quantum = hopt->quantum;
		if ((cl->prio = hopt->prio) >= TC_HTB_NUMPRIO)
			cl->prio = TC_HTB_NUMPRIO - 1;
	}

	cl->buffer = PSCHED_TICKS2NS(hopt->buffer);
	cl->cbuffer = PSCHED_TICKS2NS(hopt->cbuffer);

	sch_tree_unlock(sch);

	qdisc_class_hash_grow(sch, &q->clhash);

	*arg = (unsigned long)cl;
	return 0;

failure:
	return err;
}

static struct tcf_proto **htb_find_tcf(struct Qdisc *sch, unsigned long arg)
{
	struct htb_sched *q = qdisc_priv(sch);
	struct htb_class *cl = (struct htb_class *)arg;
	struct tcf_proto **fl = cl ? &cl->filter_list : &q->filter_list;

	return fl;
}

static unsigned long htb_bind_filter(struct Qdisc *sch, unsigned long parent,
				     u32 classid)
{
	struct htb_class *cl = htb_find(classid, sch);

	/*if (cl && !cl->level) return 0;
	 * The line above used to be there to prevent attaching filters to
	 * leaves. But at least tc_index filter uses this just to get class
	 * for other reasons so that we have to allow for it.
	 * ----
	 * 19.6.2002 As Werner explained it is ok - bind filter is just
	 * another way to "lock" the class - unlike "get" this lock can
	 * be broken by class during destroy IIUC.
	 */
	if (cl)
		cl->filter_cnt++;
	return (unsigned long)cl;
}

static void htb_unbind_filter(struct Qdisc *sch, unsigned long arg)
{
	struct htb_class *cl = (struct htb_class *)arg;

	if (cl)
		cl->filter_cnt--;
}

static void htb_walk(struct Qdisc *sch, struct qdisc_walker *arg)
{
	struct htb_sched *q = qdisc_priv(sch);
	struct htb_class *cl;
	unsigned int i;

	if (arg->stop)
		return;

	for (i = 0; i < q->clhash.hashsize; i++) {
		hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode) {
			if (arg->count < arg->skip) {
				arg->count++;
				continue;
			}
			if (arg->fn(sch, (unsigned long)cl, arg) < 0) {
				arg->stop = 1;
				return;
			}
			arg->count++;
		}
	}
}

static const struct Qdisc_class_ops htb_class_ops = {
	.graft		=	htb_graft,
	.leaf		=	htb_leaf,
	.qlen_notify	=	htb_qlen_notify,
	.get		=	htb_get,
	.put		=	htb_put,
	.change		=	htb_change_class,
	.delete		=	htb_delete,
	.walk		=	htb_walk,
	.tcf_chain	=	htb_find_tcf,
	.bind_tcf	=	htb_bind_filter,
	.unbind_tcf	=	htb_unbind_filter,
	.dump		=	htb_dump_class,
	.dump_stats	=	htb_dump_class_stats,
};

static struct Qdisc_ops htb_qdisc_ops __read_mostly = {
	.cl_ops		=	&htb_class_ops,
	.id		=	"htb",
	.priv_size	=	sizeof(struct htb_sched),
	.enqueue	=	htb_enqueue,
	.dequeue	=	htb_dequeue,
	.peek		=	qdisc_peek_dequeued,
	.drop		=	htb_drop,
	.init		=	htb_init,
	.reset		=	htb_reset,
	.destroy	=	htb_destroy,
	.dump		=	htb_dump,
	.owner		=	THIS_MODULE,
};

static int __init htb_module_init(void)
{
	return register_qdisc(&htb_qdisc_ops);
}
static void __exit htb_module_exit(void)
{
	unregister_qdisc(&htb_qdisc_ops);
}

module_init(htb_module_init)
module_exit(htb_module_exit)
MODULE_LICENSE("GPL");