raid5-cache.c 33.6 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
/*
 * Copyright (C) 2015 Shaohua Li <shli@fb.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 */
#include <linux/kernel.h>
#include <linux/wait.h>
#include <linux/blkdev.h>
#include <linux/slab.h>
#include <linux/raid/md_p.h>
#include <linux/crc32c.h>
#include <linux/random.h>
#include "md.h"
#include "raid5.h"

/*
 * metadata/data stored in disk with 4k size unit (a block) regardless
 * underneath hardware sector size. only works with PAGE_SIZE == 4096
 */
#define BLOCK_SECTORS (8)

/*
 * reclaim runs every 1/4 disk size or 10G reclaimable space. This can prevent
 * recovery scans a very long log
 */
#define RECLAIM_MAX_FREE_SPACE (10 * 1024 * 1024 * 2) /* sector */
#define RECLAIM_MAX_FREE_SPACE_SHIFT (2)

/*
 * We only need 2 bios per I/O unit to make progress, but ensure we
 * have a few more available to not get too tight.
 */
#define R5L_POOL_SIZE	4

struct r5l_log {
	struct md_rdev *rdev;

	u32 uuid_checksum;

	sector_t device_size;		/* log device size, round to
					 * BLOCK_SECTORS */
	sector_t max_free_space;	/* reclaim run if free space is at
					 * this size */

	sector_t last_checkpoint;	/* log tail. where recovery scan
					 * starts from */
	u64 last_cp_seq;		/* log tail sequence */

	sector_t log_start;		/* log head. where new data appends */
	u64 seq;			/* log head sequence */

	sector_t next_checkpoint;
	u64 next_cp_seq;

	struct mutex io_mutex;
	struct r5l_io_unit *current_io;	/* current io_unit accepting new data */

	spinlock_t io_list_lock;
	struct list_head running_ios;	/* io_units which are still running,
					 * and have not yet been completely
					 * written to the log */
	struct list_head io_end_ios;	/* io_units which have been completely
					 * written to the log but not yet written
					 * to the RAID */
	struct list_head flushing_ios;	/* io_units which are waiting for log
					 * cache flush */
	struct list_head finished_ios;	/* io_units which settle down in log disk */
	struct bio flush_bio;

	struct list_head no_mem_stripes;   /* pending stripes, -ENOMEM */

	struct kmem_cache *io_kc;
	mempool_t *io_pool;
	struct bio_set *bs;
	mempool_t *meta_pool;

	struct md_thread *reclaim_thread;
	unsigned long reclaim_target;	/* number of space that need to be
					 * reclaimed.  if it's 0, reclaim spaces
					 * used by io_units which are in
					 * IO_UNIT_STRIPE_END state (eg, reclaim
					 * dones't wait for specific io_unit
					 * switching to IO_UNIT_STRIPE_END
					 * state) */
	wait_queue_head_t iounit_wait;

	struct list_head no_space_stripes; /* pending stripes, log has no space */
	spinlock_t no_space_stripes_lock;

	bool need_cache_flush;
};

/*
 * an IO range starts from a meta data block and end at the next meta data
 * block. The io unit's the meta data block tracks data/parity followed it. io
 * unit is written to log disk with normal write, as we always flush log disk
 * first and then start move data to raid disks, there is no requirement to
 * write io unit with FLUSH/FUA
 */
struct r5l_io_unit {
	struct r5l_log *log;

	struct page *meta_page;	/* store meta block */
	int meta_offset;	/* current offset in meta_page */

	struct bio *current_bio;/* current_bio accepting new data */

	atomic_t pending_stripe;/* how many stripes not flushed to raid */
	u64 seq;		/* seq number of the metablock */
	sector_t log_start;	/* where the io_unit starts */
	sector_t log_end;	/* where the io_unit ends */
	struct list_head log_sibling; /* log->running_ios */
	struct list_head stripe_list; /* stripes added to the io_unit */

	int state;
	bool need_split_bio;
};

/* r5l_io_unit state */
enum r5l_io_unit_state {
	IO_UNIT_RUNNING = 0,	/* accepting new IO */
	IO_UNIT_IO_START = 1,	/* io_unit bio start writing to log,
				 * don't accepting new bio */
	IO_UNIT_IO_END = 2,	/* io_unit bio finish writing to log */
	IO_UNIT_STRIPE_END = 3,	/* stripes data finished writing to raid */
};

static sector_t r5l_ring_add(struct r5l_log *log, sector_t start, sector_t inc)
{
	start += inc;
	if (start >= log->device_size)
		start = start - log->device_size;
	return start;
}

static sector_t r5l_ring_distance(struct r5l_log *log, sector_t start,
				  sector_t end)
{
	if (end >= start)
		return end - start;
	else
		return end + log->device_size - start;
}

static bool r5l_has_free_space(struct r5l_log *log, sector_t size)
{
	sector_t used_size;

	used_size = r5l_ring_distance(log, log->last_checkpoint,
					log->log_start);

	return log->device_size > used_size + size;
}

static void __r5l_set_io_unit_state(struct r5l_io_unit *io,
				    enum r5l_io_unit_state state)
{
	if (WARN_ON(io->state >= state))
		return;
	io->state = state;
}

static void r5l_io_run_stripes(struct r5l_io_unit *io)
{
	struct stripe_head *sh, *next;

	list_for_each_entry_safe(sh, next, &io->stripe_list, log_list) {
		list_del_init(&sh->log_list);
		set_bit(STRIPE_HANDLE, &sh->state);
		raid5_release_stripe(sh);
	}
}

static void r5l_log_run_stripes(struct r5l_log *log)
{
	struct r5l_io_unit *io, *next;

	assert_spin_locked(&log->io_list_lock);

	list_for_each_entry_safe(io, next, &log->running_ios, log_sibling) {
		/* don't change list order */
		if (io->state < IO_UNIT_IO_END)
			break;

		list_move_tail(&io->log_sibling, &log->finished_ios);
		r5l_io_run_stripes(io);
	}
}

static void r5l_move_to_end_ios(struct r5l_log *log)
{
	struct r5l_io_unit *io, *next;

	assert_spin_locked(&log->io_list_lock);

	list_for_each_entry_safe(io, next, &log->running_ios, log_sibling) {
		/* don't change list order */
		if (io->state < IO_UNIT_IO_END)
			break;
		list_move_tail(&io->log_sibling, &log->io_end_ios);
	}
}

static void r5l_log_endio(struct bio *bio)
{
	struct r5l_io_unit *io = bio->bi_private;
	struct r5l_log *log = io->log;
	unsigned long flags;

	if (bio->bi_error)
		md_error(log->rdev->mddev, log->rdev);

	bio_put(bio);
	mempool_free(io->meta_page, log->meta_pool);

	spin_lock_irqsave(&log->io_list_lock, flags);
	__r5l_set_io_unit_state(io, IO_UNIT_IO_END);
	if (log->need_cache_flush)
		r5l_move_to_end_ios(log);
	else
		r5l_log_run_stripes(log);
	spin_unlock_irqrestore(&log->io_list_lock, flags);

	if (log->need_cache_flush)
		md_wakeup_thread(log->rdev->mddev->thread);
}

static void r5l_submit_current_io(struct r5l_log *log)
{
	struct r5l_io_unit *io = log->current_io;
	struct r5l_meta_block *block;
	unsigned long flags;
	u32 crc;

	if (!io)
		return;

	block = page_address(io->meta_page);
	block->meta_size = cpu_to_le32(io->meta_offset);
	crc = crc32c_le(log->uuid_checksum, block, PAGE_SIZE);
	block->checksum = cpu_to_le32(crc);

	log->current_io = NULL;
	spin_lock_irqsave(&log->io_list_lock, flags);
	__r5l_set_io_unit_state(io, IO_UNIT_IO_START);
	spin_unlock_irqrestore(&log->io_list_lock, flags);

	submit_bio(io->current_bio);
}

static struct bio *r5l_bio_alloc(struct r5l_log *log)
{
	struct bio *bio = bio_alloc_bioset(GFP_NOIO, BIO_MAX_PAGES, log->bs);

	bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
	bio->bi_bdev = log->rdev->bdev;
	bio->bi_iter.bi_sector = log->rdev->data_offset + log->log_start;

	return bio;
}

static void r5_reserve_log_entry(struct r5l_log *log, struct r5l_io_unit *io)
{
	log->log_start = r5l_ring_add(log, log->log_start, BLOCK_SECTORS);

	/*
	 * If we filled up the log device start from the beginning again,
	 * which will require a new bio.
	 *
	 * Note: for this to work properly the log size needs to me a multiple
	 * of BLOCK_SECTORS.
	 */
	if (log->log_start == 0)
		io->need_split_bio = true;

	io->log_end = log->log_start;
}

static struct r5l_io_unit *r5l_new_meta(struct r5l_log *log)
{
	struct r5l_io_unit *io;
	struct r5l_meta_block *block;

	io = mempool_alloc(log->io_pool, GFP_ATOMIC);
	if (!io)
		return NULL;
	memset(io, 0, sizeof(*io));

	io->log = log;
	INIT_LIST_HEAD(&io->log_sibling);
	INIT_LIST_HEAD(&io->stripe_list);
	io->state = IO_UNIT_RUNNING;

	io->meta_page = mempool_alloc(log->meta_pool, GFP_NOIO);
	block = page_address(io->meta_page);
	clear_page(block);
	block->magic = cpu_to_le32(R5LOG_MAGIC);
	block->version = R5LOG_VERSION;
	block->seq = cpu_to_le64(log->seq);
	block->position = cpu_to_le64(log->log_start);

	io->log_start = log->log_start;
	io->meta_offset = sizeof(struct r5l_meta_block);
	io->seq = log->seq++;

	io->current_bio = r5l_bio_alloc(log);
	io->current_bio->bi_end_io = r5l_log_endio;
	io->current_bio->bi_private = io;
	bio_add_page(io->current_bio, io->meta_page, PAGE_SIZE, 0);

	r5_reserve_log_entry(log, io);

	spin_lock_irq(&log->io_list_lock);
	list_add_tail(&io->log_sibling, &log->running_ios);
	spin_unlock_irq(&log->io_list_lock);

	return io;
}

static int r5l_get_meta(struct r5l_log *log, unsigned int payload_size)
{
	if (log->current_io &&
	    log->current_io->meta_offset + payload_size > PAGE_SIZE)
		r5l_submit_current_io(log);

	if (!log->current_io) {
		log->current_io = r5l_new_meta(log);
		if (!log->current_io)
			return -ENOMEM;
	}

	return 0;
}

static void r5l_append_payload_meta(struct r5l_log *log, u16 type,
				    sector_t location,
				    u32 checksum1, u32 checksum2,
				    bool checksum2_valid)
{
	struct r5l_io_unit *io = log->current_io;
	struct r5l_payload_data_parity *payload;

	payload = page_address(io->meta_page) + io->meta_offset;
	payload->header.type = cpu_to_le16(type);
	payload->header.flags = cpu_to_le16(0);
	payload->size = cpu_to_le32((1 + !!checksum2_valid) <<
				    (PAGE_SHIFT - 9));
	payload->location = cpu_to_le64(location);
	payload->checksum[0] = cpu_to_le32(checksum1);
	if (checksum2_valid)
		payload->checksum[1] = cpu_to_le32(checksum2);

	io->meta_offset += sizeof(struct r5l_payload_data_parity) +
		sizeof(__le32) * (1 + !!checksum2_valid);
}

static void r5l_append_payload_page(struct r5l_log *log, struct page *page)
{
	struct r5l_io_unit *io = log->current_io;

	if (io->need_split_bio) {
		struct bio *prev = io->current_bio;

		io->current_bio = r5l_bio_alloc(log);
		bio_chain(io->current_bio, prev);

		submit_bio(prev);
	}

	if (!bio_add_page(io->current_bio, page, PAGE_SIZE, 0))
		BUG();

	r5_reserve_log_entry(log, io);
}

static int r5l_log_stripe(struct r5l_log *log, struct stripe_head *sh,
			   int data_pages, int parity_pages)
{
	int i;
	int meta_size;
	int ret;
	struct r5l_io_unit *io;

	meta_size =
		((sizeof(struct r5l_payload_data_parity) + sizeof(__le32))
		 * data_pages) +
		sizeof(struct r5l_payload_data_parity) +
		sizeof(__le32) * parity_pages;

	ret = r5l_get_meta(log, meta_size);
	if (ret)
		return ret;

	io = log->current_io;

	for (i = 0; i < sh->disks; i++) {
		if (!test_bit(R5_Wantwrite, &sh->dev[i].flags))
			continue;
		if (i == sh->pd_idx || i == sh->qd_idx)
			continue;
		r5l_append_payload_meta(log, R5LOG_PAYLOAD_DATA,
					raid5_compute_blocknr(sh, i, 0),
					sh->dev[i].log_checksum, 0, false);
		r5l_append_payload_page(log, sh->dev[i].page);
	}

	if (sh->qd_idx >= 0) {
		r5l_append_payload_meta(log, R5LOG_PAYLOAD_PARITY,
					sh->sector, sh->dev[sh->pd_idx].log_checksum,
					sh->dev[sh->qd_idx].log_checksum, true);
		r5l_append_payload_page(log, sh->dev[sh->pd_idx].page);
		r5l_append_payload_page(log, sh->dev[sh->qd_idx].page);
	} else {
		r5l_append_payload_meta(log, R5LOG_PAYLOAD_PARITY,
					sh->sector, sh->dev[sh->pd_idx].log_checksum,
					0, false);
		r5l_append_payload_page(log, sh->dev[sh->pd_idx].page);
	}

	list_add_tail(&sh->log_list, &io->stripe_list);
	atomic_inc(&io->pending_stripe);
	sh->log_io = io;

	return 0;
}

static void r5l_wake_reclaim(struct r5l_log *log, sector_t space);
/*
 * running in raid5d, where reclaim could wait for raid5d too (when it flushes
 * data from log to raid disks), so we shouldn't wait for reclaim here
 */
int r5l_write_stripe(struct r5l_log *log, struct stripe_head *sh)
{
	int write_disks = 0;
	int data_pages, parity_pages;
	int meta_size;
	int reserve;
	int i;
	int ret = 0;

	if (!log)
		return -EAGAIN;
	/* Don't support stripe batch */
	if (sh->log_io || !test_bit(R5_Wantwrite, &sh->dev[sh->pd_idx].flags) ||
	    test_bit(STRIPE_SYNCING, &sh->state)) {
		/* the stripe is written to log, we start writing it to raid */
		clear_bit(STRIPE_LOG_TRAPPED, &sh->state);
		return -EAGAIN;
	}

	for (i = 0; i < sh->disks; i++) {
		void *addr;

		if (!test_bit(R5_Wantwrite, &sh->dev[i].flags))
			continue;
		write_disks++;
		/* checksum is already calculated in last run */
		if (test_bit(STRIPE_LOG_TRAPPED, &sh->state))
			continue;
		addr = kmap_atomic(sh->dev[i].page);
		sh->dev[i].log_checksum = crc32c_le(log->uuid_checksum,
						    addr, PAGE_SIZE);
		kunmap_atomic(addr);
	}
	parity_pages = 1 + !!(sh->qd_idx >= 0);
	data_pages = write_disks - parity_pages;

	meta_size =
		((sizeof(struct r5l_payload_data_parity) + sizeof(__le32))
		 * data_pages) +
		sizeof(struct r5l_payload_data_parity) +
		sizeof(__le32) * parity_pages;
	/* Doesn't work with very big raid array */
	if (meta_size + sizeof(struct r5l_meta_block) > PAGE_SIZE)
		return -EINVAL;

	set_bit(STRIPE_LOG_TRAPPED, &sh->state);
	/*
	 * The stripe must enter state machine again to finish the write, so
	 * don't delay.
	 */
	clear_bit(STRIPE_DELAYED, &sh->state);
	atomic_inc(&sh->count);

	mutex_lock(&log->io_mutex);
	/* meta + data */
	reserve = (1 + write_disks) << (PAGE_SHIFT - 9);
	if (!r5l_has_free_space(log, reserve)) {
		spin_lock(&log->no_space_stripes_lock);
		list_add_tail(&sh->log_list, &log->no_space_stripes);
		spin_unlock(&log->no_space_stripes_lock);

		r5l_wake_reclaim(log, reserve);
	} else {
		ret = r5l_log_stripe(log, sh, data_pages, parity_pages);
		if (ret) {
			spin_lock_irq(&log->io_list_lock);
			list_add_tail(&sh->log_list, &log->no_mem_stripes);
			spin_unlock_irq(&log->io_list_lock);
		}
	}

	mutex_unlock(&log->io_mutex);
	return 0;
}

void r5l_write_stripe_run(struct r5l_log *log)
{
	if (!log)
		return;
	mutex_lock(&log->io_mutex);
	r5l_submit_current_io(log);
	mutex_unlock(&log->io_mutex);
}

int r5l_handle_flush_request(struct r5l_log *log, struct bio *bio)
{
	if (!log)
		return -ENODEV;
	/*
	 * we flush log disk cache first, then write stripe data to raid disks.
	 * So if bio is finished, the log disk cache is flushed already. The
	 * recovery guarantees we can recovery the bio from log disk, so we
	 * don't need to flush again
	 */
	if (bio->bi_iter.bi_size == 0) {
		bio_endio(bio);
		return 0;
	}
	bio->bi_opf &= ~REQ_PREFLUSH;
	return -EAGAIN;
}

/* This will run after log space is reclaimed */
static void r5l_run_no_space_stripes(struct r5l_log *log)
{
	struct stripe_head *sh;

	spin_lock(&log->no_space_stripes_lock);
	while (!list_empty(&log->no_space_stripes)) {
		sh = list_first_entry(&log->no_space_stripes,
				      struct stripe_head, log_list);
		list_del_init(&sh->log_list);
		set_bit(STRIPE_HANDLE, &sh->state);
		raid5_release_stripe(sh);
	}
	spin_unlock(&log->no_space_stripes_lock);
}

static sector_t r5l_reclaimable_space(struct r5l_log *log)
{
	return r5l_ring_distance(log, log->last_checkpoint,
				 log->next_checkpoint);
}

static void r5l_run_no_mem_stripe(struct r5l_log *log)
{
	struct stripe_head *sh;

	assert_spin_locked(&log->io_list_lock);

	if (!list_empty(&log->no_mem_stripes)) {
		sh = list_first_entry(&log->no_mem_stripes,
				      struct stripe_head, log_list);
		list_del_init(&sh->log_list);
		set_bit(STRIPE_HANDLE, &sh->state);
		raid5_release_stripe(sh);
	}
}

static bool r5l_complete_finished_ios(struct r5l_log *log)
{
	struct r5l_io_unit *io, *next;
	bool found = false;

	assert_spin_locked(&log->io_list_lock);

	list_for_each_entry_safe(io, next, &log->finished_ios, log_sibling) {
		/* don't change list order */
		if (io->state < IO_UNIT_STRIPE_END)
			break;

		log->next_checkpoint = io->log_start;
		log->next_cp_seq = io->seq;

		list_del(&io->log_sibling);
		mempool_free(io, log->io_pool);
		r5l_run_no_mem_stripe(log);

		found = true;
	}

	return found;
}

static void __r5l_stripe_write_finished(struct r5l_io_unit *io)
{
	struct r5l_log *log = io->log;
	unsigned long flags;

	spin_lock_irqsave(&log->io_list_lock, flags);
	__r5l_set_io_unit_state(io, IO_UNIT_STRIPE_END);

	if (!r5l_complete_finished_ios(log)) {
		spin_unlock_irqrestore(&log->io_list_lock, flags);
		return;
	}

	if (r5l_reclaimable_space(log) > log->max_free_space)
		r5l_wake_reclaim(log, 0);

	spin_unlock_irqrestore(&log->io_list_lock, flags);
	wake_up(&log->iounit_wait);
}

void r5l_stripe_write_finished(struct stripe_head *sh)
{
	struct r5l_io_unit *io;

	io = sh->log_io;
	sh->log_io = NULL;

	if (io && atomic_dec_and_test(&io->pending_stripe))
		__r5l_stripe_write_finished(io);
}

static void r5l_log_flush_endio(struct bio *bio)
{
	struct r5l_log *log = container_of(bio, struct r5l_log,
		flush_bio);
	unsigned long flags;
	struct r5l_io_unit *io;

	if (bio->bi_error)
		md_error(log->rdev->mddev, log->rdev);

	spin_lock_irqsave(&log->io_list_lock, flags);
	list_for_each_entry(io, &log->flushing_ios, log_sibling)
		r5l_io_run_stripes(io);
	list_splice_tail_init(&log->flushing_ios, &log->finished_ios);
	spin_unlock_irqrestore(&log->io_list_lock, flags);
}

/*
 * Starting dispatch IO to raid.
 * io_unit(meta) consists of a log. There is one situation we want to avoid. A
 * broken meta in the middle of a log causes recovery can't find meta at the
 * head of log. If operations require meta at the head persistent in log, we
 * must make sure meta before it persistent in log too. A case is:
 *
 * stripe data/parity is in log, we start write stripe to raid disks. stripe
 * data/parity must be persistent in log before we do the write to raid disks.
 *
 * The solution is we restrictly maintain io_unit list order. In this case, we
 * only write stripes of an io_unit to raid disks till the io_unit is the first
 * one whose data/parity is in log.
 */
void r5l_flush_stripe_to_raid(struct r5l_log *log)
{
	bool do_flush;

	if (!log || !log->need_cache_flush)
		return;

	spin_lock_irq(&log->io_list_lock);
	/* flush bio is running */
	if (!list_empty(&log->flushing_ios)) {
		spin_unlock_irq(&log->io_list_lock);
		return;
	}
	list_splice_tail_init(&log->io_end_ios, &log->flushing_ios);
	do_flush = !list_empty(&log->flushing_ios);
	spin_unlock_irq(&log->io_list_lock);

	if (!do_flush)
		return;
	bio_reset(&log->flush_bio);
	log->flush_bio.bi_bdev = log->rdev->bdev;
	log->flush_bio.bi_end_io = r5l_log_flush_endio;
	bio_set_op_attrs(&log->flush_bio, REQ_OP_WRITE, WRITE_FLUSH);
	submit_bio(&log->flush_bio);
}

static void r5l_write_super(struct r5l_log *log, sector_t cp);
static void r5l_write_super_and_discard_space(struct r5l_log *log,
	sector_t end)
{
	struct block_device *bdev = log->rdev->bdev;
	struct mddev *mddev;

	r5l_write_super(log, end);

	if (!blk_queue_discard(bdev_get_queue(bdev)))
		return;

	mddev = log->rdev->mddev;
	/*
	 * Discard could zero data, so before discard we must make sure
	 * superblock is updated to new log tail. Updating superblock (either
	 * directly call md_update_sb() or depend on md thread) must hold
	 * reconfig mutex. On the other hand, raid5_quiesce is called with
	 * reconfig_mutex hold. The first step of raid5_quiesce() is waitting
	 * for all IO finish, hence waitting for reclaim thread, while reclaim
	 * thread is calling this function and waitting for reconfig mutex. So
	 * there is a deadlock. We workaround this issue with a trylock.
	 * FIXME: we could miss discard if we can't take reconfig mutex
	 */
	set_mask_bits(&mddev->flags, 0,
		BIT(MD_CHANGE_DEVS) | BIT(MD_CHANGE_PENDING));
	if (!mddev_trylock(mddev))
		return;
	md_update_sb(mddev, 1);
	mddev_unlock(mddev);

	/* discard IO error really doesn't matter, ignore it */
	if (log->last_checkpoint < end) {
		blkdev_issue_discard(bdev,
				log->last_checkpoint + log->rdev->data_offset,
				end - log->last_checkpoint, GFP_NOIO, 0);
	} else {
		blkdev_issue_discard(bdev,
				log->last_checkpoint + log->rdev->data_offset,
				log->device_size - log->last_checkpoint,
				GFP_NOIO, 0);
		blkdev_issue_discard(bdev, log->rdev->data_offset, end,
				GFP_NOIO, 0);
	}
}


static void r5l_do_reclaim(struct r5l_log *log)
{
	sector_t reclaim_target = xchg(&log->reclaim_target, 0);
	sector_t reclaimable;
	sector_t next_checkpoint;
	u64 next_cp_seq;

	spin_lock_irq(&log->io_list_lock);
	/*
	 * move proper io_unit to reclaim list. We should not change the order.
	 * reclaimable/unreclaimable io_unit can be mixed in the list, we
	 * shouldn't reuse space of an unreclaimable io_unit
	 */
	while (1) {
		reclaimable = r5l_reclaimable_space(log);
		if (reclaimable >= reclaim_target ||
		    (list_empty(&log->running_ios) &&
		     list_empty(&log->io_end_ios) &&
		     list_empty(&log->flushing_ios) &&
		     list_empty(&log->finished_ios)))
			break;

		md_wakeup_thread(log->rdev->mddev->thread);
		wait_event_lock_irq(log->iounit_wait,
				    r5l_reclaimable_space(log) > reclaimable,
				    log->io_list_lock);
	}

	next_checkpoint = log->next_checkpoint;
	next_cp_seq = log->next_cp_seq;
	spin_unlock_irq(&log->io_list_lock);

	BUG_ON(reclaimable < 0);
	if (reclaimable == 0)
		return;

	/*
	 * write_super will flush cache of each raid disk. We must write super
	 * here, because the log area might be reused soon and we don't want to
	 * confuse recovery
	 */
	r5l_write_super_and_discard_space(log, next_checkpoint);

	mutex_lock(&log->io_mutex);
	log->last_checkpoint = next_checkpoint;
	log->last_cp_seq = next_cp_seq;
	mutex_unlock(&log->io_mutex);

	r5l_run_no_space_stripes(log);
}

static void r5l_reclaim_thread(struct md_thread *thread)
{
	struct mddev *mddev = thread->mddev;
	struct r5conf *conf = mddev->private;
	struct r5l_log *log = conf->log;

	if (!log)
		return;
	r5l_do_reclaim(log);
}

static void r5l_wake_reclaim(struct r5l_log *log, sector_t space)
{
	unsigned long target;
	unsigned long new = (unsigned long)space; /* overflow in theory */

	do {
		target = log->reclaim_target;
		if (new < target)
			return;
	} while (cmpxchg(&log->reclaim_target, target, new) != target);
	md_wakeup_thread(log->reclaim_thread);
}

void r5l_quiesce(struct r5l_log *log, int state)
{
	struct mddev *mddev;
	if (!log || state == 2)
		return;
	if (state == 0) {
		/*
		 * This is a special case for hotadd. In suspend, the array has
		 * no journal. In resume, journal is initialized as well as the
		 * reclaim thread.
		 */
		if (log->reclaim_thread)
			return;
		log->reclaim_thread = md_register_thread(r5l_reclaim_thread,
					log->rdev->mddev, "reclaim");
	} else if (state == 1) {
		/* make sure r5l_write_super_and_discard_space exits */
		mddev = log->rdev->mddev;
		wake_up(&mddev->sb_wait);
		r5l_wake_reclaim(log, -1L);
		md_unregister_thread(&log->reclaim_thread);
		r5l_do_reclaim(log);
	}
}

bool r5l_log_disk_error(struct r5conf *conf)
{
	struct r5l_log *log;
	bool ret;
	/* don't allow write if journal disk is missing */
	rcu_read_lock();
	log = rcu_dereference(conf->log);

	if (!log)
		ret = test_bit(MD_HAS_JOURNAL, &conf->mddev->flags);
	else
		ret = test_bit(Faulty, &log->rdev->flags);
	rcu_read_unlock();
	return ret;
}

struct r5l_recovery_ctx {
	struct page *meta_page;		/* current meta */
	sector_t meta_total_blocks;	/* total size of current meta and data */
	sector_t pos;			/* recovery position */
	u64 seq;			/* recovery position seq */
};

static int r5l_read_meta_block(struct r5l_log *log,
			       struct r5l_recovery_ctx *ctx)
{
	struct page *page = ctx->meta_page;
	struct r5l_meta_block *mb;
	u32 crc, stored_crc;

	if (!sync_page_io(log->rdev, ctx->pos, PAGE_SIZE, page, REQ_OP_READ, 0,
			  false))
		return -EIO;

	mb = page_address(page);
	stored_crc = le32_to_cpu(mb->checksum);
	mb->checksum = 0;

	if (le32_to_cpu(mb->magic) != R5LOG_MAGIC ||
	    le64_to_cpu(mb->seq) != ctx->seq ||
	    mb->version != R5LOG_VERSION ||
	    le64_to_cpu(mb->position) != ctx->pos)
		return -EINVAL;

	crc = crc32c_le(log->uuid_checksum, mb, PAGE_SIZE);
	if (stored_crc != crc)
		return -EINVAL;

	if (le32_to_cpu(mb->meta_size) > PAGE_SIZE)
		return -EINVAL;

	ctx->meta_total_blocks = BLOCK_SECTORS;

	return 0;
}

static int r5l_recovery_flush_one_stripe(struct r5l_log *log,
					 struct r5l_recovery_ctx *ctx,
					 sector_t stripe_sect,
					 int *offset, sector_t *log_offset)
{
	struct r5conf *conf = log->rdev->mddev->private;
	struct stripe_head *sh;
	struct r5l_payload_data_parity *payload;
	int disk_index;

	sh = raid5_get_active_stripe(conf, stripe_sect, 0, 0, 0);
	while (1) {
		payload = page_address(ctx->meta_page) + *offset;

		if (le16_to_cpu(payload->header.type) == R5LOG_PAYLOAD_DATA) {
			raid5_compute_sector(conf,
					     le64_to_cpu(payload->location), 0,
					     &disk_index, sh);

			sync_page_io(log->rdev, *log_offset, PAGE_SIZE,
				     sh->dev[disk_index].page, REQ_OP_READ, 0,
				     false);
			sh->dev[disk_index].log_checksum =
				le32_to_cpu(payload->checksum[0]);
			set_bit(R5_Wantwrite, &sh->dev[disk_index].flags);
			ctx->meta_total_blocks += BLOCK_SECTORS;
		} else {
			disk_index = sh->pd_idx;
			sync_page_io(log->rdev, *log_offset, PAGE_SIZE,
				     sh->dev[disk_index].page, REQ_OP_READ, 0,
				     false);
			sh->dev[disk_index].log_checksum =
				le32_to_cpu(payload->checksum[0]);
			set_bit(R5_Wantwrite, &sh->dev[disk_index].flags);

			if (sh->qd_idx >= 0) {
				disk_index = sh->qd_idx;
				sync_page_io(log->rdev,
					     r5l_ring_add(log, *log_offset, BLOCK_SECTORS),
					     PAGE_SIZE, sh->dev[disk_index].page,
					     REQ_OP_READ, 0, false);
				sh->dev[disk_index].log_checksum =
					le32_to_cpu(payload->checksum[1]);
				set_bit(R5_Wantwrite,
					&sh->dev[disk_index].flags);
			}
			ctx->meta_total_blocks += BLOCK_SECTORS * conf->max_degraded;
		}

		*log_offset = r5l_ring_add(log, *log_offset,
					   le32_to_cpu(payload->size));
		*offset += sizeof(struct r5l_payload_data_parity) +
			sizeof(__le32) *
			(le32_to_cpu(payload->size) >> (PAGE_SHIFT - 9));
		if (le16_to_cpu(payload->header.type) == R5LOG_PAYLOAD_PARITY)
			break;
	}

	for (disk_index = 0; disk_index < sh->disks; disk_index++) {
		void *addr;
		u32 checksum;

		if (!test_bit(R5_Wantwrite, &sh->dev[disk_index].flags))
			continue;
		addr = kmap_atomic(sh->dev[disk_index].page);
		checksum = crc32c_le(log->uuid_checksum, addr, PAGE_SIZE);
		kunmap_atomic(addr);
		if (checksum != sh->dev[disk_index].log_checksum)
			goto error;
	}

	for (disk_index = 0; disk_index < sh->disks; disk_index++) {
		struct md_rdev *rdev, *rrdev;

		if (!test_and_clear_bit(R5_Wantwrite,
					&sh->dev[disk_index].flags))
			continue;

		/* in case device is broken */
		rdev = rcu_dereference(conf->disks[disk_index].rdev);
		if (rdev)
			sync_page_io(rdev, stripe_sect, PAGE_SIZE,
				     sh->dev[disk_index].page, REQ_OP_WRITE, 0,
				     false);
		rrdev = rcu_dereference(conf->disks[disk_index].replacement);
		if (rrdev)
			sync_page_io(rrdev, stripe_sect, PAGE_SIZE,
				     sh->dev[disk_index].page, REQ_OP_WRITE, 0,
				     false);
	}
	raid5_release_stripe(sh);
	return 0;

error:
	for (disk_index = 0; disk_index < sh->disks; disk_index++)
		sh->dev[disk_index].flags = 0;
	raid5_release_stripe(sh);
	return -EINVAL;
}

static int r5l_recovery_flush_one_meta(struct r5l_log *log,
				       struct r5l_recovery_ctx *ctx)
{
	struct r5conf *conf = log->rdev->mddev->private;
	struct r5l_payload_data_parity *payload;
	struct r5l_meta_block *mb;
	int offset;
	sector_t log_offset;
	sector_t stripe_sector;

	mb = page_address(ctx->meta_page);
	offset = sizeof(struct r5l_meta_block);
	log_offset = r5l_ring_add(log, ctx->pos, BLOCK_SECTORS);

	while (offset < le32_to_cpu(mb->meta_size)) {
		int dd;

		payload = (void *)mb + offset;
		stripe_sector = raid5_compute_sector(conf,
						     le64_to_cpu(payload->location), 0, &dd, NULL);
		if (r5l_recovery_flush_one_stripe(log, ctx, stripe_sector,
						  &offset, &log_offset))
			return -EINVAL;
	}
	return 0;
}

/* copy data/parity from log to raid disks */
static void r5l_recovery_flush_log(struct r5l_log *log,
				   struct r5l_recovery_ctx *ctx)
{
	while (1) {
		if (r5l_read_meta_block(log, ctx))
			return;
		if (r5l_recovery_flush_one_meta(log, ctx))
			return;
		ctx->seq++;
		ctx->pos = r5l_ring_add(log, ctx->pos, ctx->meta_total_blocks);
	}
}

static int r5l_log_write_empty_meta_block(struct r5l_log *log, sector_t pos,
					  u64 seq)
{
	struct page *page;
	struct r5l_meta_block *mb;
	u32 crc;

	page = alloc_page(GFP_KERNEL | __GFP_ZERO);
	if (!page)
		return -ENOMEM;
	mb = page_address(page);
	mb->magic = cpu_to_le32(R5LOG_MAGIC);
	mb->version = R5LOG_VERSION;
	mb->meta_size = cpu_to_le32(sizeof(struct r5l_meta_block));
	mb->seq = cpu_to_le64(seq);
	mb->position = cpu_to_le64(pos);
	crc = crc32c_le(log->uuid_checksum, mb, PAGE_SIZE);
	mb->checksum = cpu_to_le32(crc);

	if (!sync_page_io(log->rdev, pos, PAGE_SIZE, page, REQ_OP_WRITE,
			  WRITE_FUA, false)) {
		__free_page(page);
		return -EIO;
	}
	__free_page(page);
	return 0;
}

static int r5l_recovery_log(struct r5l_log *log)
{
	struct r5l_recovery_ctx ctx;

	ctx.pos = log->last_checkpoint;
	ctx.seq = log->last_cp_seq;
	ctx.meta_page = alloc_page(GFP_KERNEL);
	if (!ctx.meta_page)
		return -ENOMEM;

	r5l_recovery_flush_log(log, &ctx);
	__free_page(ctx.meta_page);

	/*
	 * we did a recovery. Now ctx.pos points to an invalid meta block. New
	 * log will start here. but we can't let superblock point to last valid
	 * meta block. The log might looks like:
	 * | meta 1| meta 2| meta 3|
	 * meta 1 is valid, meta 2 is invalid. meta 3 could be valid. If
	 * superblock points to meta 1, we write a new valid meta 2n.  if crash
	 * happens again, new recovery will start from meta 1. Since meta 2n is
	 * valid now, recovery will think meta 3 is valid, which is wrong.
	 * The solution is we create a new meta in meta2 with its seq == meta
	 * 1's seq + 10 and let superblock points to meta2. The same recovery will
	 * not think meta 3 is a valid meta, because its seq doesn't match
	 */
	if (ctx.seq > log->last_cp_seq) {
		int ret;

		ret = r5l_log_write_empty_meta_block(log, ctx.pos, ctx.seq + 10);
		if (ret)
			return ret;
		log->seq = ctx.seq + 11;
		log->log_start = r5l_ring_add(log, ctx.pos, BLOCK_SECTORS);
		r5l_write_super(log, ctx.pos);
		log->last_checkpoint = ctx.pos;
		log->next_checkpoint = ctx.pos;
	} else {
		log->log_start = ctx.pos;
		log->seq = ctx.seq;
	}
	return 0;
}

static void r5l_write_super(struct r5l_log *log, sector_t cp)
{
	struct mddev *mddev = log->rdev->mddev;

	log->rdev->journal_tail = cp;
	set_bit(MD_CHANGE_DEVS, &mddev->flags);
}

static int r5l_load_log(struct r5l_log *log)
{
	struct md_rdev *rdev = log->rdev;
	struct page *page;
	struct r5l_meta_block *mb;
	sector_t cp = log->rdev->journal_tail;
	u32 stored_crc, expected_crc;
	bool create_super = false;
	int ret;

	/* Make sure it's valid */
	if (cp >= rdev->sectors || round_down(cp, BLOCK_SECTORS) != cp)
		cp = 0;
	page = alloc_page(GFP_KERNEL);
	if (!page)
		return -ENOMEM;

	if (!sync_page_io(rdev, cp, PAGE_SIZE, page, REQ_OP_READ, 0, false)) {
		ret = -EIO;
		goto ioerr;
	}
	mb = page_address(page);

	if (le32_to_cpu(mb->magic) != R5LOG_MAGIC ||
	    mb->version != R5LOG_VERSION) {
		create_super = true;
		goto create;
	}
	stored_crc = le32_to_cpu(mb->checksum);
	mb->checksum = 0;
	expected_crc = crc32c_le(log->uuid_checksum, mb, PAGE_SIZE);
	if (stored_crc != expected_crc) {
		create_super = true;
		goto create;
	}
	if (le64_to_cpu(mb->position) != cp) {
		create_super = true;
		goto create;
	}
create:
	if (create_super) {
		log->last_cp_seq = prandom_u32();
		cp = 0;
		r5l_log_write_empty_meta_block(log, cp, log->last_cp_seq);
		/*
		 * Make sure super points to correct address. Log might have
		 * data very soon. If super hasn't correct log tail address,
		 * recovery can't find the log
		 */
		r5l_write_super(log, cp);
	} else
		log->last_cp_seq = le64_to_cpu(mb->seq);

	log->device_size = round_down(rdev->sectors, BLOCK_SECTORS);
	log->max_free_space = log->device_size >> RECLAIM_MAX_FREE_SPACE_SHIFT;
	if (log->max_free_space > RECLAIM_MAX_FREE_SPACE)
		log->max_free_space = RECLAIM_MAX_FREE_SPACE;
	log->last_checkpoint = cp;
	log->next_checkpoint = cp;

	__free_page(page);

	return r5l_recovery_log(log);
ioerr:
	__free_page(page);
	return ret;
}

int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev)
{
	struct request_queue *q = bdev_get_queue(rdev->bdev);
	struct r5l_log *log;

	if (PAGE_SIZE != 4096)
		return -EINVAL;
	log = kzalloc(sizeof(*log), GFP_KERNEL);
	if (!log)
		return -ENOMEM;
	log->rdev = rdev;

	log->need_cache_flush = test_bit(QUEUE_FLAG_WC, &q->queue_flags) != 0;

	log->uuid_checksum = crc32c_le(~0, rdev->mddev->uuid,
				       sizeof(rdev->mddev->uuid));

	mutex_init(&log->io_mutex);

	spin_lock_init(&log->io_list_lock);
	INIT_LIST_HEAD(&log->running_ios);
	INIT_LIST_HEAD(&log->io_end_ios);
	INIT_LIST_HEAD(&log->flushing_ios);
	INIT_LIST_HEAD(&log->finished_ios);
	bio_init(&log->flush_bio);

	log->io_kc = KMEM_CACHE(r5l_io_unit, 0);
	if (!log->io_kc)
		goto io_kc;

	log->io_pool = mempool_create_slab_pool(R5L_POOL_SIZE, log->io_kc);
	if (!log->io_pool)
		goto io_pool;

	log->bs = bioset_create(R5L_POOL_SIZE, 0);
	if (!log->bs)
		goto io_bs;

	log->meta_pool = mempool_create_page_pool(R5L_POOL_SIZE, 0);
	if (!log->meta_pool)
		goto out_mempool;

	log->reclaim_thread = md_register_thread(r5l_reclaim_thread,
						 log->rdev->mddev, "reclaim");
	if (!log->reclaim_thread)
		goto reclaim_thread;
	init_waitqueue_head(&log->iounit_wait);

	INIT_LIST_HEAD(&log->no_mem_stripes);

	INIT_LIST_HEAD(&log->no_space_stripes);
	spin_lock_init(&log->no_space_stripes_lock);

	if (r5l_load_log(log))
		goto error;

	rcu_assign_pointer(conf->log, log);
	set_bit(MD_HAS_JOURNAL, &conf->mddev->flags);
	return 0;

error:
	md_unregister_thread(&log->reclaim_thread);
reclaim_thread:
	mempool_destroy(log->meta_pool);
out_mempool:
	bioset_free(log->bs);
io_bs:
	mempool_destroy(log->io_pool);
io_pool:
	kmem_cache_destroy(log->io_kc);
io_kc:
	kfree(log);
	return -EINVAL;
}

void r5l_exit_log(struct r5l_log *log)
{
	md_unregister_thread(&log->reclaim_thread);
	mempool_destroy(log->meta_pool);
	bioset_free(log->bs);
	mempool_destroy(log->io_pool);
	kmem_cache_destroy(log->io_kc);
	kfree(log);
}