1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Copyright (C) 2010 Kent Overstreet <kent.overstreet@gmail.com>
   4 *
   5 * Uses a block device as cache for other block devices; optimized for SSDs.
   6 * All allocation is done in buckets, which should match the erase block size
   7 * of the device.
   8 *
   9 * Buckets containing cached data are kept on a heap sorted by priority;
  10 * bucket priority is increased on cache hit, and periodically all the buckets
  11 * on the heap have their priority scaled down. This currently is just used as
  12 * an LRU but in the future should allow for more intelligent heuristics.
  13 *
  14 * Buckets have an 8 bit counter; freeing is accomplished by incrementing the
  15 * counter. Garbage collection is used to remove stale pointers.
  16 *
  17 * Indexing is done via a btree; nodes are not necessarily fully sorted, rather
  18 * as keys are inserted we only sort the pages that have not yet been written.
  19 * When garbage collection is run, we resort the entire node.
  20 *
  21 * All configuration is done via sysfs; see Documentation/admin-guide/bcache.rst.
  22 */
  23
  24#include "bcache.h"
  25#include "btree.h"
  26#include "debug.h"
  27#include "extents.h"
  28
  29#include <linux/slab.h>
  30#include <linux/bitops.h>
  31#include <linux/hash.h>
  32#include <linux/kthread.h>
  33#include <linux/prefetch.h>
  34#include <linux/random.h>
  35#include <linux/rcupdate.h>
  36#include <linux/sched/clock.h>
  37#include <linux/rculist.h>
  38#include <linux/delay.h>
  39#include <trace/events/bcache.h>
  40
  41/*
  42 * Todo:
  43 * register_bcache: Return errors out to userspace correctly
  44 *
  45 * Writeback: don't undirty key until after a cache flush
  46 *
  47 * Create an iterator for key pointers
  48 *
  49 * On btree write error, mark bucket such that it won't be freed from the cache
  50 *
  51 * Journalling:
  52 *   Check for bad keys in replay
  53 *   Propagate barriers
  54 *   Refcount journal entries in journal_replay
  55 *
  56 * Garbage collection:
  57 *   Finish incremental gc
  58 *   Gc should free old UUIDs, data for invalid UUIDs
  59 *
  60 * Provide a way to list backing device UUIDs we have data cached for, and
  61 * probably how long it's been since we've seen them, and a way to invalidate
  62 * dirty data for devices that will never be attached again
  63 *
  64 * Keep 1 min/5 min/15 min statistics of how busy a block device has been, so
  65 * that based on that and how much dirty data we have we can keep writeback
  66 * from being starved
  67 *
  68 * Add a tracepoint or somesuch to watch for writeback starvation
  69 *
  70 * When btree depth > 1 and splitting an interior node, we have to make sure
  71 * alloc_bucket() cannot fail. This should be true but is not completely
  72 * obvious.
  73 *
  74 * Plugging?
  75 *
  76 * If data write is less than hard sector size of ssd, round up offset in open
  77 * bucket to the next whole sector
  78 *
  79 * Superblock needs to be fleshed out for multiple cache devices
  80 *
  81 * Add a sysfs tunable for the number of writeback IOs in flight
  82 *
  83 * Add a sysfs tunable for the number of open data buckets
  84 *
  85 * IO tracking: Can we track when one process is doing io on behalf of another?
  86 * IO tracking: Don't use just an average, weigh more recent stuff higher
  87 *
  88 * Test module load/unload
  89 */
  90
  91#define MAX_NEED_GC		64
  92#define MAX_SAVE_PRIO		72
  93#define MAX_GC_TIMES		100
  94#define MIN_GC_NODES		100
  95#define GC_SLEEP_MS		100
  96
  97#define PTR_DIRTY_BIT		(((uint64_t) 1 << 36))
  98
  99#define PTR_HASH(c, k)							\
 100	(((k)->ptr[0] >> c->bucket_bits) | PTR_GEN(k, 0))
 101
 102static struct workqueue_struct *btree_io_wq;
 103
 104#define insert_lock(s, b)	((b)->level <= (s)->lock)
 105
 106
 107static inline struct bset *write_block(struct btree *b)
 108{
 109	return ((void *) btree_bset_first(b)) + b->written * block_bytes(b->c->cache);
 110}
 111
 112static void bch_btree_init_next(struct btree *b)
 113{
 114	/* If not a leaf node, always sort */
 115	if (b->level && b->keys.nsets)
 116		bch_btree_sort(&b->keys, &b->c->sort);
 117	else
 118		bch_btree_sort_lazy(&b->keys, &b->c->sort);
 119
 120	if (b->written < btree_blocks(b))
 121		bch_bset_init_next(&b->keys, write_block(b),
 122				   bset_magic(&b->c->cache->sb));
 123
 124}
 125
 126/* Btree key manipulation */
 127
 128void bkey_put(struct cache_set *c, struct bkey *k)
 129{
 130	unsigned int i;
 131
 132	for (i = 0; i < KEY_PTRS(k); i++)
 133		if (ptr_available(c, k, i))
 134			atomic_dec_bug(&PTR_BUCKET(c, k, i)->pin);
 135}
 136
 137/* Btree IO */
 138
 139static uint64_t btree_csum_set(struct btree *b, struct bset *i)
 140{
 141	uint64_t crc = b->key.ptr[0];
 142	void *data = (void *) i + 8, *end = bset_bkey_last(i);
 143
 144	crc = crc64_be(crc, data, end - data);
 145	return crc ^ 0xffffffffffffffffULL;
 146}
 147
 148void bch_btree_node_read_done(struct btree *b)
 149{
 150	const char *err = "bad btree header";
 151	struct bset *i = btree_bset_first(b);
 152	struct btree_iter *iter;
 153
 154	/*
 155	 * c->fill_iter can allocate an iterator with more memory space
 156	 * than static MAX_BSETS.
 157	 * See the comment arount cache_set->fill_iter.
 158	 */
 159	iter = mempool_alloc(&b->c->fill_iter, GFP_NOIO);
 160	iter->size = b->c->cache->sb.bucket_size / b->c->cache->sb.block_size;
 161	iter->used = 0;
 162
 163#ifdef CONFIG_BCACHE_DEBUG
 164	iter->b = &b->keys;
 165#endif
 166
 167	if (!i->seq)
 168		goto err;
 169
 170	for (;
 171	     b->written < btree_blocks(b) && i->seq == b->keys.set[0].data->seq;
 172	     i = write_block(b)) {
 173		err = "unsupported bset version";
 174		if (i->version > BCACHE_BSET_VERSION)
 175			goto err;
 176
 177		err = "bad btree header";
 178		if (b->written + set_blocks(i, block_bytes(b->c->cache)) >
 179		    btree_blocks(b))
 180			goto err;
 181
 182		err = "bad magic";
 183		if (i->magic != bset_magic(&b->c->cache->sb))
 184			goto err;
 185
 186		err = "bad checksum";
 187		switch (i->version) {
 188		case 0:
 189			if (i->csum != csum_set(i))
 190				goto err;
 191			break;
 192		case BCACHE_BSET_VERSION:
 193			if (i->csum != btree_csum_set(b, i))
 194				goto err;
 195			break;
 196		}
 197
 198		err = "empty set";
 199		if (i != b->keys.set[0].data && !i->keys)
 200			goto err;
 201
 202		bch_btree_iter_push(iter, i->start, bset_bkey_last(i));
 203
 204		b->written += set_blocks(i, block_bytes(b->c->cache));
 205	}
 206
 207	err = "corrupted btree";
 208	for (i = write_block(b);
 209	     bset_sector_offset(&b->keys, i) < KEY_SIZE(&b->key);
 210	     i = ((void *) i) + block_bytes(b->c->cache))
 211		if (i->seq == b->keys.set[0].data->seq)
 212			goto err;
 213
 214	bch_btree_sort_and_fix_extents(&b->keys, iter, &b->c->sort);
 215
 216	i = b->keys.set[0].data;
 217	err = "short btree key";
 218	if (b->keys.set[0].size &&
 219	    bkey_cmp(&b->key, &b->keys.set[0].end) < 0)
 220		goto err;
 221
 222	if (b->written < btree_blocks(b))
 223		bch_bset_init_next(&b->keys, write_block(b),
 224				   bset_magic(&b->c->cache->sb));
 225out:
 226	mempool_free(iter, &b->c->fill_iter);
 227	return;
 228err:
 229	set_btree_node_io_error(b);
 230	bch_cache_set_error(b->c, "%s at bucket %zu, block %u, %u keys",
 231			    err, PTR_BUCKET_NR(b->c, &b->key, 0),
 232			    bset_block_offset(b, i), i->keys);
 233	goto out;
 234}
 235
 236static void btree_node_read_endio(struct bio *bio)
 237{
 238	struct closure *cl = bio->bi_private;
 239
 240	closure_put(cl);
 241}
 242
 243static void bch_btree_node_read(struct btree *b)
 244{
 245	uint64_t start_time = local_clock();
 246	struct closure cl;
 247	struct bio *bio;
 248
 249	trace_bcache_btree_read(b);
 250
 251	closure_init_stack(&cl);
 252
 253	bio = bch_bbio_alloc(b->c);
 254	bio->bi_iter.bi_size = KEY_SIZE(&b->key) << 9;
 255	bio->bi_end_io	= btree_node_read_endio;
 256	bio->bi_private	= &cl;
 257	bio->bi_opf = REQ_OP_READ | REQ_META;
 258
 259	bch_bio_map(bio, b->keys.set[0].data);
 260
 261	bch_submit_bbio(bio, b->c, &b->key, 0);
 262	closure_sync(&cl);
 263
 264	if (bio->bi_status)
 265		set_btree_node_io_error(b);
 266
 267	bch_bbio_free(bio, b->c);
 268
 269	if (btree_node_io_error(b))
 270		goto err;
 271
 272	bch_btree_node_read_done(b);
 273	bch_time_stats_update(&b->c->btree_read_time, start_time);
 274
 275	return;
 276err:
 277	bch_cache_set_error(b->c, "io error reading bucket %zu",
 278			    PTR_BUCKET_NR(b->c, &b->key, 0));
 279}
 280
 281static void btree_complete_write(struct btree *b, struct btree_write *w)
 282{
 283	if (w->prio_blocked &&
 284	    !atomic_sub_return(w->prio_blocked, &b->c->prio_blocked))
 285		wake_up_allocators(b->c);
 286
 287	if (w->journal) {
 288		atomic_dec_bug(w->journal);
 289		__closure_wake_up(&b->c->journal.wait);
 290	}
 291
 292	w->prio_blocked	= 0;
 293	w->journal	= NULL;
 294}
 295
 296static CLOSURE_CALLBACK(btree_node_write_unlock)
 297{
 298	closure_type(b, struct btree, io);
 299
 300	up(&b->io_mutex);
 301}
 302
 303static CLOSURE_CALLBACK(__btree_node_write_done)
 304{
 305	closure_type(b, struct btree, io);
 306	struct btree_write *w = btree_prev_write(b);
 307
 308	bch_bbio_free(b->bio, b->c);
 309	b->bio = NULL;
 310	btree_complete_write(b, w);
 311
 312	if (btree_node_dirty(b))
 313		queue_delayed_work(btree_io_wq, &b->work, 30 * HZ);
 314
 315	closure_return_with_destructor(cl, btree_node_write_unlock);
 316}
 317
 318static CLOSURE_CALLBACK(btree_node_write_done)
 319{
 320	closure_type(b, struct btree, io);
 321
 322	bio_free_pages(b->bio);
 323	__btree_node_write_done(&cl->work);
 324}
 325
 326static void btree_node_write_endio(struct bio *bio)
 327{
 328	struct closure *cl = bio->bi_private;
 329	struct btree *b = container_of(cl, struct btree, io);
 330
 331	if (bio->bi_status)
 332		set_btree_node_io_error(b);
 333
 334	bch_bbio_count_io_errors(b->c, bio, bio->bi_status, "writing btree");
 335	closure_put(cl);
 336}
 337
 338static void do_btree_node_write(struct btree *b)
 339{
 340	struct closure *cl = &b->io;
 341	struct bset *i = btree_bset_last(b);
 342	BKEY_PADDED(key) k;
 343
 344	i->version	= BCACHE_BSET_VERSION;
 345	i->csum		= btree_csum_set(b, i);
 346
 347	BUG_ON(b->bio);
 348	b->bio = bch_bbio_alloc(b->c);
 349
 350	b->bio->bi_end_io	= btree_node_write_endio;
 351	b->bio->bi_private	= cl;
 352	b->bio->bi_iter.bi_size	= roundup(set_bytes(i), block_bytes(b->c->cache));
 353	b->bio->bi_opf		= REQ_OP_WRITE | REQ_META | REQ_FUA;
 354	bch_bio_map(b->bio, i);
 355
 356	/*
 357	 * If we're appending to a leaf node, we don't technically need FUA -
 358	 * this write just needs to be persisted before the next journal write,
 359	 * which will be marked FLUSH|FUA.
 360	 *
 361	 * Similarly if we're writing a new btree root - the pointer is going to
 362	 * be in the next journal entry.
 363	 *
 364	 * But if we're writing a new btree node (that isn't a root) or
 365	 * appending to a non leaf btree node, we need either FUA or a flush
 366	 * when we write the parent with the new pointer. FUA is cheaper than a
 367	 * flush, and writes appending to leaf nodes aren't blocking anything so
 368	 * just make all btree node writes FUA to keep things sane.
 369	 */
 370
 371	bkey_copy(&k.key, &b->key);
 372	SET_PTR_OFFSET(&k.key, 0, PTR_OFFSET(&k.key, 0) +
 373		       bset_sector_offset(&b->keys, i));
 374
 375	if (!bch_bio_alloc_pages(b->bio, __GFP_NOWARN|GFP_NOWAIT)) {
 376		struct bio_vec *bv;
 377		void *addr = (void *) ((unsigned long) i & ~(PAGE_SIZE - 1));
 378		struct bvec_iter_all iter_all;
 379
 380		bio_for_each_segment_all(bv, b->bio, iter_all) {
 381			memcpy(page_address(bv->bv_page), addr, PAGE_SIZE);
 382			addr += PAGE_SIZE;
 383		}
 384
 385		bch_submit_bbio(b->bio, b->c, &k.key, 0);
 386
 387		continue_at(cl, btree_node_write_done, NULL);
 388	} else {
 389		/*
 390		 * No problem for multipage bvec since the bio is
 391		 * just allocated
 392		 */
 393		b->bio->bi_vcnt = 0;
 394		bch_bio_map(b->bio, i);
 395
 396		bch_submit_bbio(b->bio, b->c, &k.key, 0);
 397
 398		closure_sync(cl);
 399		continue_at_nobarrier(cl, __btree_node_write_done, NULL);
 400	}
 401}
 402
 403void __bch_btree_node_write(struct btree *b, struct closure *parent)
 404{
 405	struct bset *i = btree_bset_last(b);
 406
 407	lockdep_assert_held(&b->write_lock);
 408
 409	trace_bcache_btree_write(b);
 410
 411	BUG_ON(current->bio_list);
 412	BUG_ON(b->written >= btree_blocks(b));
 413	BUG_ON(b->written && !i->keys);
 414	BUG_ON(btree_bset_first(b)->seq != i->seq);
 415	bch_check_keys(&b->keys, "writing");
 416
 417	cancel_delayed_work(&b->work);
 418
 419	/* If caller isn't waiting for write, parent refcount is cache set */
 420	down(&b->io_mutex);
 421	closure_init(&b->io, parent ?: &b->c->cl);
 422
 423	clear_bit(BTREE_NODE_dirty,	 &b->flags);
 424	change_bit(BTREE_NODE_write_idx, &b->flags);
 425
 426	do_btree_node_write(b);
 427
 428	atomic_long_add(set_blocks(i, block_bytes(b->c->cache)) * b->c->cache->sb.block_size,
 429			&b->c->cache->btree_sectors_written);
 430
 431	b->written += set_blocks(i, block_bytes(b->c->cache));
 432}
 433
 434void bch_btree_node_write(struct btree *b, struct closure *parent)
 435{
 436	unsigned int nsets = b->keys.nsets;
 437
 438	lockdep_assert_held(&b->lock);
 439
 440	__bch_btree_node_write(b, parent);
 441
 442	/*
 443	 * do verify if there was more than one set initially (i.e. we did a
 444	 * sort) and we sorted down to a single set:
 445	 */
 446	if (nsets && !b->keys.nsets)
 447		bch_btree_verify(b);
 448
 449	bch_btree_init_next(b);
 450}
 451
 452static void bch_btree_node_write_sync(struct btree *b)
 453{
 454	struct closure cl;
 455
 456	closure_init_stack(&cl);
 457
 458	mutex_lock(&b->write_lock);
 459	bch_btree_node_write(b, &cl);
 460	mutex_unlock(&b->write_lock);
 461
 462	closure_sync(&cl);
 463}
 464
 465static void btree_node_write_work(struct work_struct *w)
 466{
 467	struct btree *b = container_of(to_delayed_work(w), struct btree, work);
 468
 469	mutex_lock(&b->write_lock);
 470	if (btree_node_dirty(b))
 471		__bch_btree_node_write(b, NULL);
 472	mutex_unlock(&b->write_lock);
 473}
 474
 475static void bch_btree_leaf_dirty(struct btree *b, atomic_t *journal_ref)
 476{
 477	struct bset *i = btree_bset_last(b);
 478	struct btree_write *w = btree_current_write(b);
 479
 480	lockdep_assert_held(&b->write_lock);
 481
 482	BUG_ON(!b->written);
 483	BUG_ON(!i->keys);
 484
 485	if (!btree_node_dirty(b))
 486		queue_delayed_work(btree_io_wq, &b->work, 30 * HZ);
 487
 488	set_btree_node_dirty(b);
 489
 490	/*
 491	 * w->journal is always the oldest journal pin of all bkeys
 492	 * in the leaf node, to make sure the oldest jset seq won't
 493	 * be increased before this btree node is flushed.
 494	 */
 495	if (journal_ref) {
 496		if (w->journal &&
 497		    journal_pin_cmp(b->c, w->journal, journal_ref)) {
 498			atomic_dec_bug(w->journal);
 499			w->journal = NULL;
 500		}
 501
 502		if (!w->journal) {
 503			w->journal = journal_ref;
 504			atomic_inc(w->journal);
 505		}
 506	}
 507
 508	/* Force write if set is too big */
 509	if (set_bytes(i) > PAGE_SIZE - 48 &&
 510	    !current->bio_list)
 511		bch_btree_node_write(b, NULL);
 512}
 513
 514/*
 515 * Btree in memory cache - allocation/freeing
 516 * mca -> memory cache
 517 */
 518
 519#define mca_reserve(c)	(((!IS_ERR_OR_NULL(c->root) && c->root->level) \
 520			  ? c->root->level : 1) * 8 + 16)
 521#define mca_can_free(c)						\
 522	max_t(int, 0, c->btree_cache_used - mca_reserve(c))
 523
 524static void mca_data_free(struct btree *b)
 525{
 526	BUG_ON(b->io_mutex.count != 1);
 527
 528	bch_btree_keys_free(&b->keys);
 529
 530	b->c->btree_cache_used--;
 531	list_move(&b->list, &b->c->btree_cache_freed);
 532}
 533
 534static void mca_bucket_free(struct btree *b)
 535{
 536	BUG_ON(btree_node_dirty(b));
 537
 538	b->key.ptr[0] = 0;
 539	hlist_del_init_rcu(&b->hash);
 540	list_move(&b->list, &b->c->btree_cache_freeable);
 541}
 542
 543static unsigned int btree_order(struct bkey *k)
 544{
 545	return ilog2(KEY_SIZE(k) / PAGE_SECTORS ?: 1);
 546}
 547
 548static void mca_data_alloc(struct btree *b, struct bkey *k, gfp_t gfp)
 549{
 550	if (!bch_btree_keys_alloc(&b->keys,
 551				  max_t(unsigned int,
 552					ilog2(b->c->btree_pages),
 553					btree_order(k)),
 554				  gfp)) {
 555		b->c->btree_cache_used++;
 556		list_move(&b->list, &b->c->btree_cache);
 557	} else {
 558		list_move(&b->list, &b->c->btree_cache_freed);
 559	}
 560}
 561
 562#define cmp_int(l, r)		((l > r) - (l < r))
 563
 564#ifdef CONFIG_PROVE_LOCKING
 565static int btree_lock_cmp_fn(const struct lockdep_map *_a,
 566			     const struct lockdep_map *_b)
 567{
 568	const struct btree *a = container_of(_a, struct btree, lock.dep_map);
 569	const struct btree *b = container_of(_b, struct btree, lock.dep_map);
 570
 571	return -cmp_int(a->level, b->level) ?: bkey_cmp(&a->key, &b->key);
 572}
 573
 574static void btree_lock_print_fn(const struct lockdep_map *map)
 575{
 576	const struct btree *b = container_of(map, struct btree, lock.dep_map);
 577
 578	printk(KERN_CONT " l=%u %llu:%llu", b->level,
 579	       KEY_INODE(&b->key), KEY_OFFSET(&b->key));
 580}
 581#endif
 582
 583static struct btree *mca_bucket_alloc(struct cache_set *c,
 584				      struct bkey *k, gfp_t gfp)
 585{
 586	/*
 587	 * kzalloc() is necessary here for initialization,
 588	 * see code comments in bch_btree_keys_init().
 589	 */
 590	struct btree *b = kzalloc(sizeof(struct btree), gfp);
 591
 592	if (!b)
 593		return NULL;
 594
 595	init_rwsem(&b->lock);
 596	lock_set_cmp_fn(&b->lock, btree_lock_cmp_fn, btree_lock_print_fn);
 597	mutex_init(&b->write_lock);
 598	lockdep_set_novalidate_class(&b->write_lock);
 599	INIT_LIST_HEAD(&b->list);
 600	INIT_DELAYED_WORK(&b->work, btree_node_write_work);
 601	b->c = c;
 602	sema_init(&b->io_mutex, 1);
 603
 604	mca_data_alloc(b, k, gfp);
 605	return b;
 606}
 607
 608static int mca_reap(struct btree *b, unsigned int min_order, bool flush)
 609{
 610	struct closure cl;
 611
 612	closure_init_stack(&cl);
 613	lockdep_assert_held(&b->c->bucket_lock);
 614
 615	if (!down_write_trylock(&b->lock))
 616		return -ENOMEM;
 617
 618	BUG_ON(btree_node_dirty(b) && !b->keys.set[0].data);
 619
 620	if (b->keys.page_order < min_order)
 621		goto out_unlock;
 622
 623	if (!flush) {
 624		if (btree_node_dirty(b))
 625			goto out_unlock;
 626
 627		if (down_trylock(&b->io_mutex))
 628			goto out_unlock;
 629		up(&b->io_mutex);
 630	}
 631
 632retry:
 633	/*
 634	 * BTREE_NODE_dirty might be cleared in btree_flush_btree() by
 635	 * __bch_btree_node_write(). To avoid an extra flush, acquire
 636	 * b->write_lock before checking BTREE_NODE_dirty bit.
 637	 */
 638	mutex_lock(&b->write_lock);
 639	/*
 640	 * If this btree node is selected in btree_flush_write() by journal
 641	 * code, delay and retry until the node is flushed by journal code
 642	 * and BTREE_NODE_journal_flush bit cleared by btree_flush_write().
 643	 */
 644	if (btree_node_journal_flush(b)) {
 645		pr_debug("bnode %p is flushing by journal, retry\n", b);
 646		mutex_unlock(&b->write_lock);
 647		udelay(1);
 648		goto retry;
 649	}
 650
 651	if (btree_node_dirty(b))
 652		__bch_btree_node_write(b, &cl);
 653	mutex_unlock(&b->write_lock);
 654
 655	closure_sync(&cl);
 656
 657	/* wait for any in flight btree write */
 658	down(&b->io_mutex);
 659	up(&b->io_mutex);
 660
 661	return 0;
 662out_unlock:
 663	rw_unlock(true, b);
 664	return -ENOMEM;
 665}
 666
 667static unsigned long bch_mca_scan(struct shrinker *shrink,
 668				  struct shrink_control *sc)
 669{
 670	struct cache_set *c = shrink->private_data;
 671	struct btree *b, *t;
 672	unsigned long i, nr = sc->nr_to_scan;
 673	unsigned long freed = 0;
 674	unsigned int btree_cache_used;
 675
 676	if (c->shrinker_disabled)
 677		return SHRINK_STOP;
 678
 679	if (c->btree_cache_alloc_lock)
 680		return SHRINK_STOP;
 681
 682	/* Return -1 if we can't do anything right now */
 683	if (sc->gfp_mask & __GFP_IO)
 684		mutex_lock(&c->bucket_lock);
 685	else if (!mutex_trylock(&c->bucket_lock))
 686		return -1;
 687
 688	/*
 689	 * It's _really_ critical that we don't free too many btree nodes - we
 690	 * have to always leave ourselves a reserve. The reserve is how we
 691	 * guarantee that allocating memory for a new btree node can always
 692	 * succeed, so that inserting keys into the btree can always succeed and
 693	 * IO can always make forward progress:
 694	 */
 695	nr /= c->btree_pages;
 696	if (nr == 0)
 697		nr = 1;
 698	nr = min_t(unsigned long, nr, mca_can_free(c));
 699
 700	i = 0;
 701	btree_cache_used = c->btree_cache_used;
 702	list_for_each_entry_safe_reverse(b, t, &c->btree_cache_freeable, list) {
 703		if (nr <= 0)
 704			goto out;
 705
 706		if (!mca_reap(b, 0, false)) {
 707			mca_data_free(b);
 708			rw_unlock(true, b);
 709			freed++;
 710		}
 711		nr--;
 712		i++;
 713	}
 714
 715	list_for_each_entry_safe_reverse(b, t, &c->btree_cache, list) {
 716		if (nr <= 0 || i >= btree_cache_used)
 717			goto out;
 718
 719		if (!mca_reap(b, 0, false)) {
 720			mca_bucket_free(b);
 721			mca_data_free(b);
 722			rw_unlock(true, b);
 723			freed++;
 724		}
 725
 726		nr--;
 727		i++;
 728	}
 729out:
 730	mutex_unlock(&c->bucket_lock);
 731	return freed * c->btree_pages;
 732}
 733
 734static unsigned long bch_mca_count(struct shrinker *shrink,
 735				   struct shrink_control *sc)
 736{
 737	struct cache_set *c = shrink->private_data;
 738
 739	if (c->shrinker_disabled)
 740		return 0;
 741
 742	if (c->btree_cache_alloc_lock)
 743		return 0;
 744
 745	return mca_can_free(c) * c->btree_pages;
 746}
 747
 748void bch_btree_cache_free(struct cache_set *c)
 749{
 750	struct btree *b;
 751	struct closure cl;
 752
 753	closure_init_stack(&cl);
 754
 755	if (c->shrink)
 756		shrinker_free(c->shrink);
 757
 758	mutex_lock(&c->bucket_lock);
 759
 760#ifdef CONFIG_BCACHE_DEBUG
 761	if (c->verify_data)
 762		list_move(&c->verify_data->list, &c->btree_cache);
 763
 764	free_pages((unsigned long) c->verify_ondisk, ilog2(meta_bucket_pages(&c->cache->sb)));
 765#endif
 766
 767	list_splice(&c->btree_cache_freeable,
 768		    &c->btree_cache);
 769
 770	while (!list_empty(&c->btree_cache)) {
 771		b = list_first_entry(&c->btree_cache, struct btree, list);
 772
 773		/*
 774		 * This function is called by cache_set_free(), no I/O
 775		 * request on cache now, it is unnecessary to acquire
 776		 * b->write_lock before clearing BTREE_NODE_dirty anymore.
 777		 */
 778		if (btree_node_dirty(b)) {
 779			btree_complete_write(b, btree_current_write(b));
 780			clear_bit(BTREE_NODE_dirty, &b->flags);
 781		}
 782		mca_data_free(b);
 783	}
 784
 785	while (!list_empty(&c->btree_cache_freed)) {
 786		b = list_first_entry(&c->btree_cache_freed,
 787				     struct btree, list);
 788		list_del(&b->list);
 789		cancel_delayed_work_sync(&b->work);
 790		kfree(b);
 791	}
 792
 793	mutex_unlock(&c->bucket_lock);
 794}
 795
 796int bch_btree_cache_alloc(struct cache_set *c)
 797{
 798	unsigned int i;
 799
 800	for (i = 0; i < mca_reserve(c); i++)
 801		if (!mca_bucket_alloc(c, &ZERO_KEY, GFP_KERNEL))
 802			return -ENOMEM;
 803
 804	list_splice_init(&c->btree_cache,
 805			 &c->btree_cache_freeable);
 806
 807#ifdef CONFIG_BCACHE_DEBUG
 808	mutex_init(&c->verify_lock);
 809
 810	c->verify_ondisk = (void *)
 811		__get_free_pages(GFP_KERNEL|__GFP_COMP,
 812				 ilog2(meta_bucket_pages(&c->cache->sb)));
 813	if (!c->verify_ondisk) {
 814		/*
 815		 * Don't worry about the mca_rereserve buckets
 816		 * allocated in previous for-loop, they will be
 817		 * handled properly in bch_cache_set_unregister().
 818		 */
 819		return -ENOMEM;
 820	}
 821
 822	c->verify_data = mca_bucket_alloc(c, &ZERO_KEY, GFP_KERNEL);
 823
 824	if (c->verify_data &&
 825	    c->verify_data->keys.set->data)
 826		list_del_init(&c->verify_data->list);
 827	else
 828		c->verify_data = NULL;
 829#endif
 830
 831	c->shrink = shrinker_alloc(0, "md-bcache:%pU", c->set_uuid);
 832	if (!c->shrink) {
 833		pr_warn("bcache: %s: could not allocate shrinker\n", __func__);
 834		return 0;
 835	}
 836
 837	c->shrink->count_objects = bch_mca_count;
 838	c->shrink->scan_objects = bch_mca_scan;
 839	c->shrink->seeks = 4;
 840	c->shrink->batch = c->btree_pages * 2;
 841	c->shrink->private_data = c;
 842
 843	shrinker_register(c->shrink);
 844
 845	return 0;
 846}
 847
 848/* Btree in memory cache - hash table */
 849
 850static struct hlist_head *mca_hash(struct cache_set *c, struct bkey *k)
 851{
 852	return &c->bucket_hash[hash_32(PTR_HASH(c, k), BUCKET_HASH_BITS)];
 853}
 854
 855static struct btree *mca_find(struct cache_set *c, struct bkey *k)
 856{
 857	struct btree *b;
 858
 859	rcu_read_lock();
 860	hlist_for_each_entry_rcu(b, mca_hash(c, k), hash)
 861		if (PTR_HASH(c, &b->key) == PTR_HASH(c, k))
 862			goto out;
 863	b = NULL;
 864out:
 865	rcu_read_unlock();
 866	return b;
 867}
 868
 869static int mca_cannibalize_lock(struct cache_set *c, struct btree_op *op)
 870{
 871	spin_lock(&c->btree_cannibalize_lock);
 872	if (likely(c->btree_cache_alloc_lock == NULL)) {
 873		c->btree_cache_alloc_lock = current;
 874	} else if (c->btree_cache_alloc_lock != current) {
 875		if (op)
 876			prepare_to_wait(&c->btree_cache_wait, &op->wait,
 877					TASK_UNINTERRUPTIBLE);
 878		spin_unlock(&c->btree_cannibalize_lock);
 879		return -EINTR;
 880	}
 881	spin_unlock(&c->btree_cannibalize_lock);
 882
 883	return 0;
 884}
 885
 886static struct btree *mca_cannibalize(struct cache_set *c, struct btree_op *op,
 887				     struct bkey *k)
 888{
 889	struct btree *b;
 890
 891	trace_bcache_btree_cache_cannibalize(c);
 892
 893	if (mca_cannibalize_lock(c, op))
 894		return ERR_PTR(-EINTR);
 895
 896	list_for_each_entry_reverse(b, &c->btree_cache, list)
 897		if (!mca_reap(b, btree_order(k), false))
 898			return b;
 899
 900	list_for_each_entry_reverse(b, &c->btree_cache, list)
 901		if (!mca_reap(b, btree_order(k), true))
 902			return b;
 903
 904	WARN(1, "btree cache cannibalize failed\n");
 905	return ERR_PTR(-ENOMEM);
 906}
 907
 908/*
 909 * We can only have one thread cannibalizing other cached btree nodes at a time,
 910 * or we'll deadlock. We use an open coded mutex to ensure that, which a
 911 * cannibalize_bucket() will take. This means every time we unlock the root of
 912 * the btree, we need to release this lock if we have it held.
 913 */
 914void bch_cannibalize_unlock(struct cache_set *c)
 915{
 916	spin_lock(&c->btree_cannibalize_lock);
 917	if (c->btree_cache_alloc_lock == current) {
 918		c->btree_cache_alloc_lock = NULL;
 919		wake_up(&c->btree_cache_wait);
 920	}
 921	spin_unlock(&c->btree_cannibalize_lock);
 922}
 923
 924static struct btree *mca_alloc(struct cache_set *c, struct btree_op *op,
 925			       struct bkey *k, int level)
 926{
 927	struct btree *b;
 928
 929	BUG_ON(current->bio_list);
 930
 931	lockdep_assert_held(&c->bucket_lock);
 932
 933	if (mca_find(c, k))
 934		return NULL;
 935
 936	/* btree_free() doesn't free memory; it sticks the node on the end of
 937	 * the list. Check if there's any freed nodes there:
 938	 */
 939	list_for_each_entry(b, &c->btree_cache_freeable, list)
 940		if (!mca_reap(b, btree_order(k), false))
 941			goto out;
 942
 943	/* We never free struct btree itself, just the memory that holds the on
 944	 * disk node. Check the freed list before allocating a new one:
 945	 */
 946	list_for_each_entry(b, &c->btree_cache_freed, list)
 947		if (!mca_reap(b, 0, false)) {
 948			mca_data_alloc(b, k, __GFP_NOWARN|GFP_NOIO);
 949			if (!b->keys.set[0].data)
 950				goto err;
 951			else
 952				goto out;
 953		}
 954
 955	b = mca_bucket_alloc(c, k, __GFP_NOWARN|GFP_NOIO);
 956	if (!b)
 957		goto err;
 958
 959	BUG_ON(!down_write_trylock(&b->lock));
 960	if (!b->keys.set->data)
 961		goto err;
 962out:
 963	BUG_ON(b->io_mutex.count != 1);
 964
 965	bkey_copy(&b->key, k);
 966	list_move(&b->list, &c->btree_cache);
 967	hlist_del_init_rcu(&b->hash);
 968	hlist_add_head_rcu(&b->hash, mca_hash(c, k));
 969
 970	lock_set_subclass(&b->lock.dep_map, level + 1, _THIS_IP_);
 971	b->parent	= (void *) ~0UL;
 972	b->flags	= 0;
 973	b->written	= 0;
 974	b->level	= level;
 975
 976	if (!b->level)
 977		bch_btree_keys_init(&b->keys, &bch_extent_keys_ops,
 978				    &b->c->expensive_debug_checks);
 979	else
 980		bch_btree_keys_init(&b->keys, &bch_btree_keys_ops,
 981				    &b->c->expensive_debug_checks);
 982
 983	return b;
 984err:
 985	if (b)
 986		rw_unlock(true, b);
 987
 988	b = mca_cannibalize(c, op, k);
 989	if (!IS_ERR(b))
 990		goto out;
 991
 992	return b;
 993}
 994
 995/*
 996 * bch_btree_node_get - find a btree node in the cache and lock it, reading it
 997 * in from disk if necessary.
 998 *
 999 * If IO is necessary and running under submit_bio_noacct, returns -EAGAIN.
1000 *
1001 * The btree node will have either a read or a write lock held, depending on
1002 * level and op->lock.
1003 *
1004 * Note: Only error code or btree pointer will be returned, it is unncessary
1005 *       for callers to check NULL pointer.
1006 */
1007struct btree *bch_btree_node_get(struct cache_set *c, struct btree_op *op,
1008				 struct bkey *k, int level, bool write,
1009				 struct btree *parent)
1010{
1011	int i = 0;
1012	struct btree *b;
1013
1014	BUG_ON(level < 0);
1015retry:
1016	b = mca_find(c, k);
1017
1018	if (!b) {
1019		if (current->bio_list)
1020			return ERR_PTR(-EAGAIN);
1021
1022		mutex_lock(&c->bucket_lock);
1023		b = mca_alloc(c, op, k, level);
1024		mutex_unlock(&c->bucket_lock);
1025
1026		if (!b)
1027			goto retry;
1028		if (IS_ERR(b))
1029			return b;
1030
1031		bch_btree_node_read(b);
1032
1033		if (!write)
1034			downgrade_write(&b->lock);
1035	} else {
1036		rw_lock(write, b, level);
1037		if (PTR_HASH(c, &b->key) != PTR_HASH(c, k)) {
1038			rw_unlock(write, b);
1039			goto retry;
1040		}
1041		BUG_ON(b->level != level);
1042	}
1043
1044	if (btree_node_io_error(b)) {
1045		rw_unlock(write, b);
1046		return ERR_PTR(-EIO);
1047	}
1048
1049	BUG_ON(!b->written);
1050
1051	b->parent = parent;
1052
1053	for (; i <= b->keys.nsets && b->keys.set[i].size; i++) {
1054		prefetch(b->keys.set[i].tree);
1055		prefetch(b->keys.set[i].data);
1056	}
1057
1058	for (; i <= b->keys.nsets; i++)
1059		prefetch(b->keys.set[i].data);
1060
1061	return b;
1062}
1063
1064static void btree_node_prefetch(struct btree *parent, struct bkey *k)
1065{
1066	struct btree *b;
1067
1068	mutex_lock(&parent->c->bucket_lock);
1069	b = mca_alloc(parent->c, NULL, k, parent->level - 1);
1070	mutex_unlock(&parent->c->bucket_lock);
1071
1072	if (!IS_ERR_OR_NULL(b)) {
1073		b->parent = parent;
1074		bch_btree_node_read(b);
1075		rw_unlock(true, b);
1076	}
1077}
1078
1079/* Btree alloc */
1080
1081static void btree_node_free(struct btree *b)
1082{
1083	trace_bcache_btree_node_free(b);
1084
1085	BUG_ON(b == b->c->root);
1086
1087retry:
1088	mutex_lock(&b->write_lock);
1089	/*
1090	 * If the btree node is selected and flushing in btree_flush_write(),
1091	 * delay and retry until the BTREE_NODE_journal_flush bit cleared,
1092	 * then it is safe to free the btree node here. Otherwise this btree
1093	 * node will be in race condition.
1094	 */
1095	if (btree_node_journal_flush(b)) {
1096		mutex_unlock(&b->write_lock);
1097		pr_debug("bnode %p journal_flush set, retry\n", b);
1098		udelay(1);
1099		goto retry;
1100	}
1101
1102	if (btree_node_dirty(b)) {
1103		btree_complete_write(b, btree_current_write(b));
1104		clear_bit(BTREE_NODE_dirty, &b->flags);
1105	}
1106
1107	mutex_unlock(&b->write_lock);
1108
1109	cancel_delayed_work(&b->work);
1110
1111	mutex_lock(&b->c->bucket_lock);
1112	bch_bucket_free(b->c, &b->key);
1113	mca_bucket_free(b);
1114	mutex_unlock(&b->c->bucket_lock);
1115}
1116
1117/*
1118 * Only error code or btree pointer will be returned, it is unncessary for
1119 * callers to check NULL pointer.
1120 */
1121struct btree *__bch_btree_node_alloc(struct cache_set *c, struct btree_op *op,
1122				     int level, bool wait,
1123				     struct btree *parent)
1124{
1125	BKEY_PADDED(key) k;
1126	struct btree *b;
1127
1128	mutex_lock(&c->bucket_lock);
1129retry:
1130	/* return ERR_PTR(-EAGAIN) when it fails */
1131	b = ERR_PTR(-EAGAIN);
1132	if (__bch_bucket_alloc_set(c, RESERVE_BTREE, &k.key, wait))
1133		goto err;
1134
1135	bkey_put(c, &k.key);
1136	SET_KEY_SIZE(&k.key, c->btree_pages * PAGE_SECTORS);
1137
1138	b = mca_alloc(c, op, &k.key, level);
1139	if (IS_ERR(b))
1140		goto err_free;
1141
1142	if (!b) {
1143		cache_bug(c,
1144			"Tried to allocate bucket that was in btree cache");
1145		goto retry;
1146	}
1147
1148	b->parent = parent;
1149	bch_bset_init_next(&b->keys, b->keys.set->data, bset_magic(&b->c->cache->sb));
1150
1151	mutex_unlock(&c->bucket_lock);
1152
1153	trace_bcache_btree_node_alloc(b);
1154	return b;
1155err_free:
1156	bch_bucket_free(c, &k.key);
1157err:
1158	mutex_unlock(&c->bucket_lock);
1159
1160	trace_bcache_btree_node_alloc_fail(c);
1161	return b;
1162}
1163
1164static struct btree *bch_btree_node_alloc(struct cache_set *c,
1165					  struct btree_op *op, int level,
1166					  struct btree *parent)
1167{
1168	return __bch_btree_node_alloc(c, op, level, op != NULL, parent);
1169}
1170
1171static struct btree *btree_node_alloc_replacement(struct btree *b,
1172						  struct btree_op *op)
1173{
1174	struct btree *n = bch_btree_node_alloc(b->c, op, b->level, b->parent);
1175
1176	if (!IS_ERR(n)) {
1177		mutex_lock(&n->write_lock);
1178		bch_btree_sort_into(&b->keys, &n->keys, &b->c->sort);
1179		bkey_copy_key(&n->key, &b->key);
1180		mutex_unlock(&n->write_lock);
1181	}
1182
1183	return n;
1184}
1185
1186static void make_btree_freeing_key(struct btree *b, struct bkey *k)
1187{
1188	unsigned int i;
1189
1190	mutex_lock(&b->c->bucket_lock);
1191
1192	atomic_inc(&b->c->prio_blocked);
1193
1194	bkey_copy(k, &b->key);
1195	bkey_copy_key(k, &ZERO_KEY);
1196
1197	for (i = 0; i < KEY_PTRS(k); i++)
1198		SET_PTR_GEN(k, i,
1199			    bch_inc_gen(b->c->cache,
1200					PTR_BUCKET(b->c, &b->key, i)));
1201
1202	mutex_unlock(&b->c->bucket_lock);
1203}
1204
1205static int btree_check_reserve(struct btree *b, struct btree_op *op)
1206{
1207	struct cache_set *c = b->c;
1208	struct cache *ca = c->cache;
1209	unsigned int reserve = (c->root->level - b->level) * 2 + 1;
1210
1211	mutex_lock(&c->bucket_lock);
1212
1213	if (fifo_used(&ca->free[RESERVE_BTREE]) < reserve) {
1214		if (op)
1215			prepare_to_wait(&c->btree_cache_wait, &op->wait,
1216					TASK_UNINTERRUPTIBLE);
1217		mutex_unlock(&c->bucket_lock);
1218		return -EINTR;
1219	}
1220
1221	mutex_unlock(&c->bucket_lock);
1222
1223	return mca_cannibalize_lock(b->c, op);
1224}
1225
1226/* Garbage collection */
1227
1228static uint8_t __bch_btree_mark_key(struct cache_set *c, int level,
1229				    struct bkey *k)
1230{
1231	uint8_t stale = 0;
1232	unsigned int i;
1233	struct bucket *g;
1234
1235	/*
1236	 * ptr_invalid() can't return true for the keys that mark btree nodes as
1237	 * freed, but since ptr_bad() returns true we'll never actually use them
1238	 * for anything and thus we don't want mark their pointers here
1239	 */
1240	if (!bkey_cmp(k, &ZERO_KEY))
1241		return stale;
1242
1243	for (i = 0; i < KEY_PTRS(k); i++) {
1244		if (!ptr_available(c, k, i))
1245			continue;
1246
1247		g = PTR_BUCKET(c, k, i);
1248
1249		if (gen_after(g->last_gc, PTR_GEN(k, i)))
1250			g->last_gc = PTR_GEN(k, i);
1251
1252		if (ptr_stale(c, k, i)) {
1253			stale = max(stale, ptr_stale(c, k, i));
1254			continue;
1255		}
1256
1257		cache_bug_on(GC_MARK(g) &&
1258			     (GC_MARK(g) == GC_MARK_METADATA) != (level != 0),
1259			     c, "inconsistent ptrs: mark = %llu, level = %i",
1260			     GC_MARK(g), level);
1261
1262		if (level)
1263			SET_GC_MARK(g, GC_MARK_METADATA);
1264		else if (KEY_DIRTY(k))
1265			SET_GC_MARK(g, GC_MARK_DIRTY);
1266		else if (!GC_MARK(g))
1267			SET_GC_MARK(g, GC_MARK_RECLAIMABLE);
1268
1269		/* guard against overflow */
1270		SET_GC_SECTORS_USED(g, min_t(unsigned int,
1271					     GC_SECTORS_USED(g) + KEY_SIZE(k),
1272					     MAX_GC_SECTORS_USED));
1273
1274		BUG_ON(!GC_SECTORS_USED(g));
1275	}
1276
1277	return stale;
1278}
1279
1280#define btree_mark_key(b, k)	__bch_btree_mark_key(b->c, b->level, k)
1281
1282void bch_initial_mark_key(struct cache_set *c, int level, struct bkey *k)
1283{
1284	unsigned int i;
1285
1286	for (i = 0; i < KEY_PTRS(k); i++)
1287		if (ptr_available(c, k, i) &&
1288		    !ptr_stale(c, k, i)) {
1289			struct bucket *b = PTR_BUCKET(c, k, i);
1290
1291			b->gen = PTR_GEN(k, i);
1292
1293			if (level && bkey_cmp(k, &ZERO_KEY))
1294				b->prio = BTREE_PRIO;
1295			else if (!level && b->prio == BTREE_PRIO)
1296				b->prio = INITIAL_PRIO;
1297		}
1298
1299	__bch_btree_mark_key(c, level, k);
1300}
1301
1302void bch_update_bucket_in_use(struct cache_set *c, struct gc_stat *stats)
1303{
1304	stats->in_use = (c->nbuckets - c->avail_nbuckets) * 100 / c->nbuckets;
1305}
1306
1307static bool btree_gc_mark_node(struct btree *b, struct gc_stat *gc)
1308{
1309	uint8_t stale = 0;
1310	unsigned int keys = 0, good_keys = 0;
1311	struct bkey *k;
1312	struct btree_iter iter;
1313	struct bset_tree *t;
1314
1315	gc->nodes++;
1316
1317	for_each_key_filter(&b->keys, k, &iter, bch_ptr_invalid) {
1318		stale = max(stale, btree_mark_key(b, k));
1319		keys++;
1320
1321		if (bch_ptr_bad(&b->keys, k))
1322			continue;
1323
1324		gc->key_bytes += bkey_u64s(k);
1325		gc->nkeys++;
1326		good_keys++;
1327
1328		gc->data += KEY_SIZE(k);
1329	}
1330
1331	for (t = b->keys.set; t <= &b->keys.set[b->keys.nsets]; t++)
1332		btree_bug_on(t->size &&
1333			     bset_written(&b->keys, t) &&
1334			     bkey_cmp(&b->key, &t->end) < 0,
1335			     b, "found short btree key in gc");
1336
1337	if (b->c->gc_always_rewrite)
1338		return true;
1339
1340	if (stale > 10)
1341		return true;
1342
1343	if ((keys - good_keys) * 2 > keys)
1344		return true;
1345
1346	return false;
1347}
1348
1349#define GC_MERGE_NODES	4U
1350
1351struct gc_merge_info {
1352	struct btree	*b;
1353	unsigned int	keys;
1354};
1355
1356static int bch_btree_insert_node(struct btree *b, struct btree_op *op,
1357				 struct keylist *insert_keys,
1358				 atomic_t *journal_ref,
1359				 struct bkey *replace_key);
1360
1361static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
1362			     struct gc_stat *gc, struct gc_merge_info *r)
1363{
1364	unsigned int i, nodes = 0, keys = 0, blocks;
1365	struct btree *new_nodes[GC_MERGE_NODES];
1366	struct keylist keylist;
1367	struct closure cl;
1368	struct bkey *k;
1369
1370	bch_keylist_init(&keylist);
1371
1372	if (btree_check_reserve(b, NULL))
1373		return 0;
1374
1375	memset(new_nodes, 0, sizeof(new_nodes));
1376	closure_init_stack(&cl);
1377
1378	while (nodes < GC_MERGE_NODES && !IS_ERR_OR_NULL(r[nodes].b))
1379		keys += r[nodes++].keys;
1380
1381	blocks = btree_default_blocks(b->c) * 2 / 3;
1382
1383	if (nodes < 2 ||
1384	    __set_blocks(b->keys.set[0].data, keys,
1385			 block_bytes(b->c->cache)) > blocks * (nodes - 1))
1386		return 0;
1387
1388	for (i = 0; i < nodes; i++) {
1389		new_nodes[i] = btree_node_alloc_replacement(r[i].b, NULL);
1390		if (IS_ERR(new_nodes[i]))
1391			goto out_nocoalesce;
1392	}
1393
1394	/*
1395	 * We have to check the reserve here, after we've allocated our new
1396	 * nodes, to make sure the insert below will succeed - we also check
1397	 * before as an optimization to potentially avoid a bunch of expensive
1398	 * allocs/sorts
1399	 */
1400	if (btree_check_reserve(b, NULL))
1401		goto out_nocoalesce;
1402
1403	for (i = 0; i < nodes; i++)
1404		mutex_lock(&new_nodes[i]->write_lock);
1405
1406	for (i = nodes - 1; i > 0; --i) {
1407		struct bset *n1 = btree_bset_first(new_nodes[i]);
1408		struct bset *n2 = btree_bset_first(new_nodes[i - 1]);
1409		struct bkey *k, *last = NULL;
1410
1411		keys = 0;
1412
1413		if (i > 1) {
1414			for (k = n2->start;
1415			     k < bset_bkey_last(n2);
1416			     k = bkey_next(k)) {
1417				if (__set_blocks(n1, n1->keys + keys +
1418						 bkey_u64s(k),
1419						 block_bytes(b->c->cache)) > blocks)
1420					break;
1421
1422				last = k;
1423				keys += bkey_u64s(k);
1424			}
1425		} else {
1426			/*
1427			 * Last node we're not getting rid of - we're getting
1428			 * rid of the node at r[0]. Have to try and fit all of
1429			 * the remaining keys into this node; we can't ensure
1430			 * they will always fit due to rounding and variable
1431			 * length keys (shouldn't be possible in practice,
1432			 * though)
1433			 */
1434			if (__set_blocks(n1, n1->keys + n2->keys,
1435					 block_bytes(b->c->cache)) >
1436			    btree_blocks(new_nodes[i]))
1437				goto out_unlock_nocoalesce;
1438
1439			keys = n2->keys;
1440			/* Take the key of the node we're getting rid of */
1441			last = &r->b->key;
1442		}
1443
1444		BUG_ON(__set_blocks(n1, n1->keys + keys, block_bytes(b->c->cache)) >
1445		       btree_blocks(new_nodes[i]));
1446
1447		if (last)
1448			bkey_copy_key(&new_nodes[i]->key, last);
1449
1450		memcpy(bset_bkey_last(n1),
1451		       n2->start,
1452		       (void *) bset_bkey_idx(n2, keys) - (void *) n2->start);
1453
1454		n1->keys += keys;
1455		r[i].keys = n1->keys;
1456
1457		memmove(n2->start,
1458			bset_bkey_idx(n2, keys),
1459			(void *) bset_bkey_last(n2) -
1460			(void *) bset_bkey_idx(n2, keys));
1461
1462		n2->keys -= keys;
1463
1464		if (__bch_keylist_realloc(&keylist,
1465					  bkey_u64s(&new_nodes[i]->key)))
1466			goto out_unlock_nocoalesce;
1467
1468		bch_btree_node_write(new_nodes[i], &cl);
1469		bch_keylist_add(&keylist, &new_nodes[i]->key);
1470	}
1471
1472	for (i = 0; i < nodes; i++)
1473		mutex_unlock(&new_nodes[i]->write_lock);
1474
1475	closure_sync(&cl);
1476
1477	/* We emptied out this node */
1478	BUG_ON(btree_bset_first(new_nodes[0])->keys);
1479	btree_node_free(new_nodes[0]);
1480	rw_unlock(true, new_nodes[0]);
1481	new_nodes[0] = NULL;
1482
1483	for (i = 0; i < nodes; i++) {
1484		if (__bch_keylist_realloc(&keylist, bkey_u64s(&r[i].b->key)))
1485			goto out_nocoalesce;
1486
1487		make_btree_freeing_key(r[i].b, keylist.top);
1488		bch_keylist_push(&keylist);
1489	}
1490
1491	bch_btree_insert_node(b, op, &keylist, NULL, NULL);
1492	BUG_ON(!bch_keylist_empty(&keylist));
1493
1494	for (i = 0; i < nodes; i++) {
1495		btree_node_free(r[i].b);
1496		rw_unlock(true, r[i].b);
1497
1498		r[i].b = new_nodes[i];
1499	}
1500
1501	memmove(r, r + 1, sizeof(r[0]) * (nodes - 1));
1502	r[nodes - 1].b = ERR_PTR(-EINTR);
1503
1504	trace_bcache_btree_gc_coalesce(nodes);
1505	gc->nodes--;
1506
1507	bch_keylist_free(&keylist);
1508
1509	/* Invalidated our iterator */
1510	return -EINTR;
1511
1512out_unlock_nocoalesce:
1513	for (i = 0; i < nodes; i++)
1514		mutex_unlock(&new_nodes[i]->write_lock);
1515
1516out_nocoalesce:
1517	closure_sync(&cl);
1518
1519	while ((k = bch_keylist_pop(&keylist)))
1520		if (!bkey_cmp(k, &ZERO_KEY))
1521			atomic_dec(&b->c->prio_blocked);
1522	bch_keylist_free(&keylist);
1523
1524	for (i = 0; i < nodes; i++)
1525		if (!IS_ERR_OR_NULL(new_nodes[i])) {
1526			btree_node_free(new_nodes[i]);
1527			rw_unlock(true, new_nodes[i]);
1528		}
1529	return 0;
1530}
1531
1532static int btree_gc_rewrite_node(struct btree *b, struct btree_op *op,
1533				 struct btree *replace)
1534{
1535	struct keylist keys;
1536	struct btree *n;
1537
1538	if (btree_check_reserve(b, NULL))
1539		return 0;
1540
1541	n = btree_node_alloc_replacement(replace, NULL);
1542	if (IS_ERR(n))
1543		return 0;
1544
1545	/* recheck reserve after allocating replacement node */
1546	if (btree_check_reserve(b, NULL)) {
1547		btree_node_free(n);
1548		rw_unlock(true, n);
1549		return 0;
1550	}
1551
1552	bch_btree_node_write_sync(n);
1553
1554	bch_keylist_init(&keys);
1555	bch_keylist_add(&keys, &n->key);
1556
1557	make_btree_freeing_key(replace, keys.top);
1558	bch_keylist_push(&keys);
1559
1560	bch_btree_insert_node(b, op, &keys, NULL, NULL);
1561	BUG_ON(!bch_keylist_empty(&keys));
1562
1563	btree_node_free(replace);
1564	rw_unlock(true, n);
1565
1566	/* Invalidated our iterator */
1567	return -EINTR;
1568}
1569
1570static unsigned int btree_gc_count_keys(struct btree *b)
1571{
1572	struct bkey *k;
1573	struct btree_iter iter;
1574	unsigned int ret = 0;
1575
1576	for_each_key_filter(&b->keys, k, &iter, bch_ptr_bad)
1577		ret += bkey_u64s(k);
1578
1579	return ret;
1580}
1581
1582static size_t btree_gc_min_nodes(struct cache_set *c)
1583{
1584	size_t min_nodes;
1585
1586	/*
1587	 * Since incremental GC would stop 100ms when front
1588	 * side I/O comes, so when there are many btree nodes,
1589	 * if GC only processes constant (100) nodes each time,
1590	 * GC would last a long time, and the front side I/Os
1591	 * would run out of the buckets (since no new bucket
1592	 * can be allocated during GC), and be blocked again.
1593	 * So GC should not process constant nodes, but varied
1594	 * nodes according to the number of btree nodes, which
1595	 * realized by dividing GC into constant(100) times,
1596	 * so when there are many btree nodes, GC can process
1597	 * more nodes each time, otherwise, GC will process less
1598	 * nodes each time (but no less than MIN_GC_NODES)
1599	 */
1600	min_nodes = c->gc_stats.nodes / MAX_GC_TIMES;
1601	if (min_nodes < MIN_GC_NODES)
1602		min_nodes = MIN_GC_NODES;
1603
1604	return min_nodes;
1605}
1606
1607
1608static int btree_gc_recurse(struct btree *b, struct btree_op *op,
1609			    struct closure *writes, struct gc_stat *gc)
1610{
1611	int ret = 0;
1612	bool should_rewrite;
1613	struct bkey *k;
1614	struct btree_iter iter;
1615	struct gc_merge_info r[GC_MERGE_NODES];
1616	struct gc_merge_info *i, *last = r + ARRAY_SIZE(r) - 1;
1617
1618	bch_btree_iter_init(&b->keys, &iter, &b->c->gc_done);
1619
1620	for (i = r; i < r + ARRAY_SIZE(r); i++)
1621		i->b = ERR_PTR(-EINTR);
1622
1623	while (1) {
1624		k = bch_btree_iter_next_filter(&iter, &b->keys, bch_ptr_bad);
1625		if (k) {
1626			r->b = bch_btree_node_get(b->c, op, k, b->level - 1,
1627						  true, b);
1628			if (IS_ERR(r->b)) {
1629				ret = PTR_ERR(r->b);
1630				break;
1631			}
1632
1633			r->keys = btree_gc_count_keys(r->b);
1634
1635			ret = btree_gc_coalesce(b, op, gc, r);
1636			if (ret)
1637				break;
1638		}
1639
1640		if (!last->b)
1641			break;
1642
1643		if (!IS_ERR(last->b)) {
1644			should_rewrite = btree_gc_mark_node(last->b, gc);
1645			if (should_rewrite) {
1646				ret = btree_gc_rewrite_node(b, op, last->b);
1647				if (ret)
1648					break;
1649			}
1650
1651			if (last->b->level) {
1652				ret = btree_gc_recurse(last->b, op, writes, gc);
1653				if (ret)
1654					break;
1655			}
1656
1657			bkey_copy_key(&b->c->gc_done, &last->b->key);
1658
1659			/*
1660			 * Must flush leaf nodes before gc ends, since replace
1661			 * operations aren't journalled
1662			 */
1663			mutex_lock(&last->b->write_lock);
1664			if (btree_node_dirty(last->b))
1665				bch_btree_node_write(last->b, writes);
1666			mutex_unlock(&last->b->write_lock);
1667			rw_unlock(true, last->b);
1668		}
1669
1670		memmove(r + 1, r, sizeof(r[0]) * (GC_MERGE_NODES - 1));
1671		r->b = NULL;
1672
1673		if (atomic_read(&b->c->search_inflight) &&
1674		    gc->nodes >= gc->nodes_pre + btree_gc_min_nodes(b->c)) {
1675			gc->nodes_pre =  gc->nodes;
1676			ret = -EAGAIN;
1677			break;
1678		}
1679
1680		if (need_resched()) {
1681			ret = -EAGAIN;
1682			break;
1683		}
1684	}
1685
1686	for (i = r; i < r + ARRAY_SIZE(r); i++)
1687		if (!IS_ERR_OR_NULL(i->b)) {
1688			mutex_lock(&i->b->write_lock);
1689			if (btree_node_dirty(i->b))
1690				bch_btree_node_write(i->b, writes);
1691			mutex_unlock(&i->b->write_lock);
1692			rw_unlock(true, i->b);
1693		}
1694
1695	return ret;
1696}
1697
1698static int bch_btree_gc_root(struct btree *b, struct btree_op *op,
1699			     struct closure *writes, struct gc_stat *gc)
1700{
1701	struct btree *n = NULL;
1702	int ret = 0;
1703	bool should_rewrite;
1704
1705	should_rewrite = btree_gc_mark_node(b, gc);
1706	if (should_rewrite) {
1707		n = btree_node_alloc_replacement(b, NULL);
1708
1709		if (!IS_ERR(n)) {
1710			bch_btree_node_write_sync(n);
1711
1712			bch_btree_set_root(n);
1713			btree_node_free(b);
1714			rw_unlock(true, n);
1715
1716			return -EINTR;
1717		}
1718	}
1719
1720	__bch_btree_mark_key(b->c, b->level + 1, &b->key);
1721
1722	if (b->level) {
1723		ret = btree_gc_recurse(b, op, writes, gc);
1724		if (ret)
1725			return ret;
1726	}
1727
1728	bkey_copy_key(&b->c->gc_done, &b->key);
1729
1730	return ret;
1731}
1732
1733static void btree_gc_start(struct cache_set *c)
1734{
1735	struct cache *ca;
1736	struct bucket *b;
1737
1738	if (!c->gc_mark_valid)
1739		return;
1740
1741	mutex_lock(&c->bucket_lock);
1742
1743	c->gc_mark_valid = 0;
1744	c->gc_done = ZERO_KEY;
1745
1746	ca = c->cache;
1747	for_each_bucket(b, ca) {
1748		b->last_gc = b->gen;
1749		if (!atomic_read(&b->pin)) {
1750			SET_GC_MARK(b, 0);
1751			SET_GC_SECTORS_USED(b, 0);
1752		}
1753	}
1754
1755	mutex_unlock(&c->bucket_lock);
1756}
1757
1758static void bch_btree_gc_finish(struct cache_set *c)
1759{
1760	struct bucket *b;
1761	struct cache *ca;
1762	unsigned int i, j;
1763	uint64_t *k;
1764
1765	mutex_lock(&c->bucket_lock);
1766
1767	set_gc_sectors(c);
1768	c->gc_mark_valid = 1;
1769	c->need_gc	= 0;
1770
1771	for (i = 0; i < KEY_PTRS(&c->uuid_bucket); i++)
1772		SET_GC_MARK(PTR_BUCKET(c, &c->uuid_bucket, i),
1773			    GC_MARK_METADATA);
1774
1775	/* don't reclaim buckets to which writeback keys point */
1776	rcu_read_lock();
1777	for (i = 0; i < c->devices_max_used; i++) {
1778		struct bcache_device *d = c->devices[i];
1779		struct cached_dev *dc;
1780		struct keybuf_key *w, *n;
1781
1782		if (!d || UUID_FLASH_ONLY(&c->uuids[i]))
1783			continue;
1784		dc = container_of(d, struct cached_dev, disk);
1785
1786		spin_lock(&dc->writeback_keys.lock);
1787		rbtree_postorder_for_each_entry_safe(w, n,
1788					&dc->writeback_keys.keys, node)
1789			for (j = 0; j < KEY_PTRS(&w->key); j++)
1790				SET_GC_MARK(PTR_BUCKET(c, &w->key, j),
1791					    GC_MARK_DIRTY);
1792		spin_unlock(&dc->writeback_keys.lock);
1793	}
1794	rcu_read_unlock();
1795
1796	c->avail_nbuckets = 0;
1797
1798	ca = c->cache;
1799	ca->invalidate_needs_gc = 0;
1800
1801	for (k = ca->sb.d; k < ca->sb.d + ca->sb.keys; k++)
1802		SET_GC_MARK(ca->buckets + *k, GC_MARK_METADATA);
1803
1804	for (k = ca->prio_buckets;
1805	     k < ca->prio_buckets + prio_buckets(ca) * 2; k++)
1806		SET_GC_MARK(ca->buckets + *k, GC_MARK_METADATA);
1807
1808	for_each_bucket(b, ca) {
1809		c->need_gc	= max(c->need_gc, bucket_gc_gen(b));
1810
1811		if (atomic_read(&b->pin))
1812			continue;
1813
1814		BUG_ON(!GC_MARK(b) && GC_SECTORS_USED(b));
1815
1816		if (!GC_MARK(b) || GC_MARK(b) == GC_MARK_RECLAIMABLE)
1817			c->avail_nbuckets++;
1818	}
1819
1820	mutex_unlock(&c->bucket_lock);
1821}
1822
1823static void bch_btree_gc(struct cache_set *c)
1824{
1825	int ret;
1826	struct gc_stat stats;
1827	struct closure writes;
1828	struct btree_op op;
1829	uint64_t start_time = local_clock();
1830
1831	trace_bcache_gc_start(c);
1832
1833	memset(&stats, 0, sizeof(struct gc_stat));
1834	closure_init_stack(&writes);
1835	bch_btree_op_init(&op, SHRT_MAX);
1836
1837	btree_gc_start(c);
1838
1839	/* if CACHE_SET_IO_DISABLE set, gc thread should stop too */
1840	do {
1841		ret = bcache_btree_root(gc_root, c, &op, &writes, &stats);
1842		closure_sync(&writes);
1843		cond_resched();
1844
1845		if (ret == -EAGAIN)
1846			schedule_timeout_interruptible(msecs_to_jiffies
1847						       (GC_SLEEP_MS));
1848		else if (ret)
1849			pr_warn("gc failed!\n");
1850	} while (ret && !test_bit(CACHE_SET_IO_DISABLE, &c->flags));
1851
1852	bch_btree_gc_finish(c);
1853	wake_up_allocators(c);
1854
1855	bch_time_stats_update(&c->btree_gc_time, start_time);
1856
1857	stats.key_bytes *= sizeof(uint64_t);
1858	stats.data	<<= 9;
1859	bch_update_bucket_in_use(c, &stats);
1860	memcpy(&c->gc_stats, &stats, sizeof(struct gc_stat));
1861
1862	trace_bcache_gc_end(c);
1863
1864	bch_moving_gc(c);
1865}
1866
1867static bool gc_should_run(struct cache_set *c)
1868{
1869	struct cache *ca = c->cache;
1870
1871	if (ca->invalidate_needs_gc)
1872		return true;
1873
1874	if (atomic_read(&c->sectors_to_gc) < 0)
1875		return true;
1876
1877	return false;
1878}
1879
1880static int bch_gc_thread(void *arg)
1881{
1882	struct cache_set *c = arg;
1883
1884	while (1) {
1885		wait_event_interruptible(c->gc_wait,
1886			   kthread_should_stop() ||
1887			   test_bit(CACHE_SET_IO_DISABLE, &c->flags) ||
1888			   gc_should_run(c));
1889
1890		if (kthread_should_stop() ||
1891		    test_bit(CACHE_SET_IO_DISABLE, &c->flags))
1892			break;
1893
1894		set_gc_sectors(c);
1895		bch_btree_gc(c);
1896	}
1897
1898	wait_for_kthread_stop();
1899	return 0;
1900}
1901
1902int bch_gc_thread_start(struct cache_set *c)
1903{
1904	c->gc_thread = kthread_run(bch_gc_thread, c, "bcache_gc");
1905	return PTR_ERR_OR_ZERO(c->gc_thread);
1906}
1907
1908/* Initial partial gc */
1909
1910static int bch_btree_check_recurse(struct btree *b, struct btree_op *op)
1911{
1912	int ret = 0;
1913	struct bkey *k, *p = NULL;
1914	struct btree_iter iter;
1915
1916	for_each_key_filter(&b->keys, k, &iter, bch_ptr_invalid)
1917		bch_initial_mark_key(b->c, b->level, k);
1918
1919	bch_initial_mark_key(b->c, b->level + 1, &b->key);
1920
1921	if (b->level) {
1922		bch_btree_iter_init(&b->keys, &iter, NULL);
1923
1924		do {
1925			k = bch_btree_iter_next_filter(&iter, &b->keys,
1926						       bch_ptr_bad);
1927			if (k) {
1928				btree_node_prefetch(b, k);
1929				/*
1930				 * initiallize c->gc_stats.nodes
1931				 * for incremental GC
1932				 */
1933				b->c->gc_stats.nodes++;
1934			}
1935
1936			if (p)
1937				ret = bcache_btree(check_recurse, p, b, op);
1938
1939			p = k;
1940		} while (p && !ret);
1941	}
1942
1943	return ret;
1944}
1945
1946
1947static int bch_btree_check_thread(void *arg)
1948{
1949	int ret;
1950	struct btree_check_info *info = arg;
1951	struct btree_check_state *check_state = info->state;
1952	struct cache_set *c = check_state->c;
1953	struct btree_iter iter;
1954	struct bkey *k, *p;
1955	int cur_idx, prev_idx, skip_nr;
1956
1957	k = p = NULL;
1958	cur_idx = prev_idx = 0;
1959	ret = 0;
1960
1961	/* root node keys are checked before thread created */
1962	bch_btree_iter_init(&c->root->keys, &iter, NULL);
1963	k = bch_btree_iter_next_filter(&iter, &c->root->keys, bch_ptr_bad);
1964	BUG_ON(!k);
1965
1966	p = k;
1967	while (k) {
1968		/*
1969		 * Fetch a root node key index, skip the keys which
1970		 * should be fetched by other threads, then check the
1971		 * sub-tree indexed by the fetched key.
1972		 */
1973		spin_lock(&check_state->idx_lock);
1974		cur_idx = check_state->key_idx;
1975		check_state->key_idx++;
1976		spin_unlock(&check_state->idx_lock);
1977
1978		skip_nr = cur_idx - prev_idx;
1979
1980		while (skip_nr) {
1981			k = bch_btree_iter_next_filter(&iter,
1982						       &c->root->keys,
1983						       bch_ptr_bad);
1984			if (k)
1985				p = k;
1986			else {
1987				/*
1988				 * No more keys to check in root node,
1989				 * current checking threads are enough,
1990				 * stop creating more.
1991				 */
1992				atomic_set(&check_state->enough, 1);
1993				/* Update check_state->enough earlier */
1994				smp_mb__after_atomic();
1995				goto out;
1996			}
1997			skip_nr--;
1998			cond_resched();
1999		}
2000
2001		if (p) {
2002			struct btree_op op;
2003
2004			btree_node_prefetch(c->root, p);
2005			c->gc_stats.nodes++;
2006			bch_btree_op_init(&op, 0);
2007			ret = bcache_btree(check_recurse, p, c->root, &op);
2008			/*
2009			 * The op may be added to cache_set's btree_cache_wait
2010			 * in mca_cannibalize(), must ensure it is removed from
2011			 * the list and release btree_cache_alloc_lock before
2012			 * free op memory.
2013			 * Otherwise, the btree_cache_wait will be damaged.
2014			 */
2015			bch_cannibalize_unlock(c);
2016			finish_wait(&c->btree_cache_wait, &(&op)->wait);
2017			if (ret)
2018				goto out;
2019		}
2020		p = NULL;
2021		prev_idx = cur_idx;
2022		cond_resched();
2023	}
2024
2025out:
2026	info->result = ret;
2027	/* update check_state->started among all CPUs */
2028	smp_mb__before_atomic();
2029	if (atomic_dec_and_test(&check_state->started))
2030		wake_up(&check_state->wait);
2031
2032	return ret;
2033}
2034
2035
2036
2037static int bch_btree_chkthread_nr(void)
2038{
2039	int n = num_online_cpus()/2;
2040
2041	if (n == 0)
2042		n = 1;
2043	else if (n > BCH_BTR_CHKTHREAD_MAX)
2044		n = BCH_BTR_CHKTHREAD_MAX;
2045
2046	return n;
2047}
2048
2049int bch_btree_check(struct cache_set *c)
2050{
2051	int ret = 0;
2052	int i;
2053	struct bkey *k = NULL;
2054	struct btree_iter iter;
2055	struct btree_check_state check_state;
 
2056
2057	/* check and mark root node keys */
2058	for_each_key_filter(&c->root->keys, k, &iter, bch_ptr_invalid)
2059		bch_initial_mark_key(c, c->root->level, k);
2060
2061	bch_initial_mark_key(c, c->root->level + 1, &c->root->key);
2062
2063	if (c->root->level == 0)
2064		return 0;
2065
2066	memset(&check_state, 0, sizeof(struct btree_check_state));
2067	check_state.c = c;
2068	check_state.total_threads = bch_btree_chkthread_nr();
2069	check_state.key_idx = 0;
2070	spin_lock_init(&check_state.idx_lock);
2071	atomic_set(&check_state.started, 0);
2072	atomic_set(&check_state.enough, 0);
2073	init_waitqueue_head(&check_state.wait);
 
 
 
2074
2075	rw_lock(0, c->root, c->root->level);
2076	/*
2077	 * Run multiple threads to check btree nodes in parallel,
2078	 * if check_state.enough is non-zero, it means current
2079	 * running check threads are enough, unncessary to create
2080	 * more.
2081	 */
2082	for (i = 0; i < check_state.total_threads; i++) {
2083		/* fetch latest check_state.enough earlier */
2084		smp_mb__before_atomic();
2085		if (atomic_read(&check_state.enough))
2086			break;
2087
2088		check_state.infos[i].result = 0;
2089		check_state.infos[i].state = &check_state;
 
 
2090
2091		check_state.infos[i].thread =
2092			kthread_run(bch_btree_check_thread,
2093				    &check_state.infos[i],
2094				    "bch_btrchk[%d]", i);
2095		if (IS_ERR(check_state.infos[i].thread)) {
2096			pr_err("fails to run thread bch_btrchk[%d]\n", i);
2097			for (--i; i >= 0; i--)
2098				kthread_stop(check_state.infos[i].thread);
2099			ret = -ENOMEM;
2100			goto out;
2101		}
2102		atomic_inc(&check_state.started);
2103	}
2104
2105	/*
2106	 * Must wait for all threads to stop.
2107	 */
2108	wait_event(check_state.wait, atomic_read(&check_state.started) == 0);
2109
2110	for (i = 0; i < check_state.total_threads; i++) {
2111		if (check_state.infos[i].result) {
2112			ret = check_state.infos[i].result;
2113			goto out;
2114		}
2115	}
2116
2117out:
2118	rw_unlock(0, c->root);
2119	return ret;
2120}
2121
2122void bch_initial_gc_finish(struct cache_set *c)
2123{
2124	struct cache *ca = c->cache;
2125	struct bucket *b;
2126
2127	bch_btree_gc_finish(c);
2128
2129	mutex_lock(&c->bucket_lock);
2130
2131	/*
2132	 * We need to put some unused buckets directly on the prio freelist in
2133	 * order to get the allocator thread started - it needs freed buckets in
2134	 * order to rewrite the prios and gens, and it needs to rewrite prios
2135	 * and gens in order to free buckets.
2136	 *
2137	 * This is only safe for buckets that have no live data in them, which
2138	 * there should always be some of.
2139	 */
2140	for_each_bucket(b, ca) {
2141		if (fifo_full(&ca->free[RESERVE_PRIO]) &&
2142		    fifo_full(&ca->free[RESERVE_BTREE]))
2143			break;
2144
2145		if (bch_can_invalidate_bucket(ca, b) &&
2146		    !GC_MARK(b)) {
2147			__bch_invalidate_one_bucket(ca, b);
2148			if (!fifo_push(&ca->free[RESERVE_PRIO],
2149			   b - ca->buckets))
2150				fifo_push(&ca->free[RESERVE_BTREE],
2151					  b - ca->buckets);
2152		}
2153	}
2154
2155	mutex_unlock(&c->bucket_lock);
2156}
2157
2158/* Btree insertion */
2159
2160static bool btree_insert_key(struct btree *b, struct bkey *k,
2161			     struct bkey *replace_key)
2162{
2163	unsigned int status;
2164
2165	BUG_ON(bkey_cmp(k, &b->key) > 0);
2166
2167	status = bch_btree_insert_key(&b->keys, k, replace_key);
2168	if (status != BTREE_INSERT_STATUS_NO_INSERT) {
2169		bch_check_keys(&b->keys, "%u for %s", status,
2170			       replace_key ? "replace" : "insert");
2171
2172		trace_bcache_btree_insert_key(b, k, replace_key != NULL,
2173					      status);
2174		return true;
2175	} else
2176		return false;
2177}
2178
2179static size_t insert_u64s_remaining(struct btree *b)
2180{
2181	long ret = bch_btree_keys_u64s_remaining(&b->keys);
2182
2183	/*
2184	 * Might land in the middle of an existing extent and have to split it
2185	 */
2186	if (b->keys.ops->is_extents)
2187		ret -= KEY_MAX_U64S;
2188
2189	return max(ret, 0L);
2190}
2191
2192static bool bch_btree_insert_keys(struct btree *b, struct btree_op *op,
2193				  struct keylist *insert_keys,
2194				  struct bkey *replace_key)
2195{
2196	bool ret = false;
2197	int oldsize = bch_count_data(&b->keys);
2198
2199	while (!bch_keylist_empty(insert_keys)) {
2200		struct bkey *k = insert_keys->keys;
2201
2202		if (bkey_u64s(k) > insert_u64s_remaining(b))
2203			break;
2204
2205		if (bkey_cmp(k, &b->key) <= 0) {
2206			if (!b->level)
2207				bkey_put(b->c, k);
2208
2209			ret |= btree_insert_key(b, k, replace_key);
2210			bch_keylist_pop_front(insert_keys);
2211		} else if (bkey_cmp(&START_KEY(k), &b->key) < 0) {
2212			BKEY_PADDED(key) temp;
2213			bkey_copy(&temp.key, insert_keys->keys);
2214
2215			bch_cut_back(&b->key, &temp.key);
2216			bch_cut_front(&b->key, insert_keys->keys);
2217
2218			ret |= btree_insert_key(b, &temp.key, replace_key);
2219			break;
2220		} else {
2221			break;
2222		}
2223	}
2224
2225	if (!ret)
2226		op->insert_collision = true;
2227
2228	BUG_ON(!bch_keylist_empty(insert_keys) && b->level);
2229
2230	BUG_ON(bch_count_data(&b->keys) < oldsize);
2231	return ret;
2232}
2233
2234static int btree_split(struct btree *b, struct btree_op *op,
2235		       struct keylist *insert_keys,
2236		       struct bkey *replace_key)
2237{
2238	bool split;
2239	struct btree *n1, *n2 = NULL, *n3 = NULL;
2240	uint64_t start_time = local_clock();
2241	struct closure cl;
2242	struct keylist parent_keys;
2243
2244	closure_init_stack(&cl);
2245	bch_keylist_init(&parent_keys);
2246
2247	if (btree_check_reserve(b, op)) {
2248		if (!b->level)
2249			return -EINTR;
2250		else
2251			WARN(1, "insufficient reserve for split\n");
2252	}
2253
2254	n1 = btree_node_alloc_replacement(b, op);
2255	if (IS_ERR(n1))
2256		goto err;
2257
2258	split = set_blocks(btree_bset_first(n1),
2259			   block_bytes(n1->c->cache)) > (btree_blocks(b) * 4) / 5;
2260
2261	if (split) {
2262		unsigned int keys = 0;
2263
2264		trace_bcache_btree_node_split(b, btree_bset_first(n1)->keys);
2265
2266		n2 = bch_btree_node_alloc(b->c, op, b->level, b->parent);
2267		if (IS_ERR(n2))
2268			goto err_free1;
2269
2270		if (!b->parent) {
2271			n3 = bch_btree_node_alloc(b->c, op, b->level + 1, NULL);
2272			if (IS_ERR(n3))
2273				goto err_free2;
2274		}
2275
2276		mutex_lock(&n1->write_lock);
2277		mutex_lock(&n2->write_lock);
2278
2279		bch_btree_insert_keys(n1, op, insert_keys, replace_key);
2280
2281		/*
2282		 * Has to be a linear search because we don't have an auxiliary
2283		 * search tree yet
2284		 */
2285
2286		while (keys < (btree_bset_first(n1)->keys * 3) / 5)
2287			keys += bkey_u64s(bset_bkey_idx(btree_bset_first(n1),
2288							keys));
2289
2290		bkey_copy_key(&n1->key,
2291			      bset_bkey_idx(btree_bset_first(n1), keys));
2292		keys += bkey_u64s(bset_bkey_idx(btree_bset_first(n1), keys));
2293
2294		btree_bset_first(n2)->keys = btree_bset_first(n1)->keys - keys;
2295		btree_bset_first(n1)->keys = keys;
2296
2297		memcpy(btree_bset_first(n2)->start,
2298		       bset_bkey_last(btree_bset_first(n1)),
2299		       btree_bset_first(n2)->keys * sizeof(uint64_t));
2300
2301		bkey_copy_key(&n2->key, &b->key);
2302
2303		bch_keylist_add(&parent_keys, &n2->key);
2304		bch_btree_node_write(n2, &cl);
2305		mutex_unlock(&n2->write_lock);
2306		rw_unlock(true, n2);
2307	} else {
2308		trace_bcache_btree_node_compact(b, btree_bset_first(n1)->keys);
2309
2310		mutex_lock(&n1->write_lock);
2311		bch_btree_insert_keys(n1, op, insert_keys, replace_key);
2312	}
2313
2314	bch_keylist_add(&parent_keys, &n1->key);
2315	bch_btree_node_write(n1, &cl);
2316	mutex_unlock(&n1->write_lock);
2317
2318	if (n3) {
2319		/* Depth increases, make a new root */
2320		mutex_lock(&n3->write_lock);
2321		bkey_copy_key(&n3->key, &MAX_KEY);
2322		bch_btree_insert_keys(n3, op, &parent_keys, NULL);
2323		bch_btree_node_write(n3, &cl);
2324		mutex_unlock(&n3->write_lock);
2325
2326		closure_sync(&cl);
2327		bch_btree_set_root(n3);
2328		rw_unlock(true, n3);
2329	} else if (!b->parent) {
2330		/* Root filled up but didn't need to be split */
2331		closure_sync(&cl);
2332		bch_btree_set_root(n1);
2333	} else {
2334		/* Split a non root node */
2335		closure_sync(&cl);
2336		make_btree_freeing_key(b, parent_keys.top);
2337		bch_keylist_push(&parent_keys);
2338
2339		bch_btree_insert_node(b->parent, op, &parent_keys, NULL, NULL);
2340		BUG_ON(!bch_keylist_empty(&parent_keys));
2341	}
2342
2343	btree_node_free(b);
2344	rw_unlock(true, n1);
2345
2346	bch_time_stats_update(&b->c->btree_split_time, start_time);
2347
2348	return 0;
2349err_free2:
2350	bkey_put(b->c, &n2->key);
2351	btree_node_free(n2);
2352	rw_unlock(true, n2);
2353err_free1:
2354	bkey_put(b->c, &n1->key);
2355	btree_node_free(n1);
2356	rw_unlock(true, n1);
2357err:
2358	WARN(1, "bcache: btree split failed (level %u)", b->level);
2359
2360	if (n3 == ERR_PTR(-EAGAIN) ||
2361	    n2 == ERR_PTR(-EAGAIN) ||
2362	    n1 == ERR_PTR(-EAGAIN))
2363		return -EAGAIN;
2364
2365	return -ENOMEM;
2366}
2367
2368static int bch_btree_insert_node(struct btree *b, struct btree_op *op,
2369				 struct keylist *insert_keys,
2370				 atomic_t *journal_ref,
2371				 struct bkey *replace_key)
2372{
2373	struct closure cl;
2374
2375	BUG_ON(b->level && replace_key);
2376
2377	closure_init_stack(&cl);
2378
2379	mutex_lock(&b->write_lock);
2380
2381	if (write_block(b) != btree_bset_last(b) &&
2382	    b->keys.last_set_unwritten)
2383		bch_btree_init_next(b); /* just wrote a set */
2384
2385	if (bch_keylist_nkeys(insert_keys) > insert_u64s_remaining(b)) {
2386		mutex_unlock(&b->write_lock);
2387		goto split;
2388	}
2389
2390	BUG_ON(write_block(b) != btree_bset_last(b));
2391
2392	if (bch_btree_insert_keys(b, op, insert_keys, replace_key)) {
2393		if (!b->level)
2394			bch_btree_leaf_dirty(b, journal_ref);
2395		else
2396			bch_btree_node_write(b, &cl);
2397	}
2398
2399	mutex_unlock(&b->write_lock);
2400
2401	/* wait for btree node write if necessary, after unlock */
2402	closure_sync(&cl);
2403
2404	return 0;
2405split:
2406	if (current->bio_list) {
2407		op->lock = b->c->root->level + 1;
2408		return -EAGAIN;
2409	} else if (op->lock <= b->c->root->level) {
2410		op->lock = b->c->root->level + 1;
2411		return -EINTR;
2412	} else {
2413		/* Invalidated all iterators */
2414		int ret = btree_split(b, op, insert_keys, replace_key);
2415
2416		if (bch_keylist_empty(insert_keys))
2417			return 0;
2418		else if (!ret)
2419			return -EINTR;
2420		return ret;
2421	}
2422}
2423
2424int bch_btree_insert_check_key(struct btree *b, struct btree_op *op,
2425			       struct bkey *check_key)
2426{
2427	int ret = -EINTR;
2428	uint64_t btree_ptr = b->key.ptr[0];
2429	unsigned long seq = b->seq;
2430	struct keylist insert;
2431	bool upgrade = op->lock == -1;
2432
2433	bch_keylist_init(&insert);
2434
2435	if (upgrade) {
2436		rw_unlock(false, b);
2437		rw_lock(true, b, b->level);
2438
2439		if (b->key.ptr[0] != btree_ptr ||
2440		    b->seq != seq + 1) {
2441			op->lock = b->level;
2442			goto out;
2443		}
2444	}
2445
2446	SET_KEY_PTRS(check_key, 1);
2447	get_random_bytes(&check_key->ptr[0], sizeof(uint64_t));
2448
2449	SET_PTR_DEV(check_key, 0, PTR_CHECK_DEV);
2450
2451	bch_keylist_add(&insert, check_key);
2452
2453	ret = bch_btree_insert_node(b, op, &insert, NULL, NULL);
2454
2455	BUG_ON(!ret && !bch_keylist_empty(&insert));
2456out:
2457	if (upgrade)
2458		downgrade_write(&b->lock);
2459	return ret;
2460}
2461
2462struct btree_insert_op {
2463	struct btree_op	op;
2464	struct keylist	*keys;
2465	atomic_t	*journal_ref;
2466	struct bkey	*replace_key;
2467};
2468
2469static int btree_insert_fn(struct btree_op *b_op, struct btree *b)
2470{
2471	struct btree_insert_op *op = container_of(b_op,
2472					struct btree_insert_op, op);
2473
2474	int ret = bch_btree_insert_node(b, &op->op, op->keys,
2475					op->journal_ref, op->replace_key);
2476	if (ret && !bch_keylist_empty(op->keys))
2477		return ret;
2478	else
2479		return MAP_DONE;
2480}
2481
2482int bch_btree_insert(struct cache_set *c, struct keylist *keys,
2483		     atomic_t *journal_ref, struct bkey *replace_key)
2484{
2485	struct btree_insert_op op;
2486	int ret = 0;
2487
2488	BUG_ON(current->bio_list);
2489	BUG_ON(bch_keylist_empty(keys));
2490
2491	bch_btree_op_init(&op.op, 0);
2492	op.keys		= keys;
2493	op.journal_ref	= journal_ref;
2494	op.replace_key	= replace_key;
2495
2496	while (!ret && !bch_keylist_empty(keys)) {
2497		op.op.lock = 0;
2498		ret = bch_btree_map_leaf_nodes(&op.op, c,
2499					       &START_KEY(keys->keys),
2500					       btree_insert_fn);
2501	}
2502
2503	if (ret) {
2504		struct bkey *k;
2505
2506		pr_err("error %i\n", ret);
2507
2508		while ((k = bch_keylist_pop(keys)))
2509			bkey_put(c, k);
2510	} else if (op.op.insert_collision)
2511		ret = -ESRCH;
2512
2513	return ret;
2514}
2515
2516void bch_btree_set_root(struct btree *b)
2517{
2518	unsigned int i;
2519	struct closure cl;
2520
2521	closure_init_stack(&cl);
2522
2523	trace_bcache_btree_set_root(b);
2524
2525	BUG_ON(!b->written);
2526
2527	for (i = 0; i < KEY_PTRS(&b->key); i++)
2528		BUG_ON(PTR_BUCKET(b->c, &b->key, i)->prio != BTREE_PRIO);
2529
2530	mutex_lock(&b->c->bucket_lock);
2531	list_del_init(&b->list);
2532	mutex_unlock(&b->c->bucket_lock);
2533
2534	b->c->root = b;
2535
2536	bch_journal_meta(b->c, &cl);
2537	closure_sync(&cl);
2538}
2539
2540/* Map across nodes or keys */
2541
2542static int bch_btree_map_nodes_recurse(struct btree *b, struct btree_op *op,
2543				       struct bkey *from,
2544				       btree_map_nodes_fn *fn, int flags)
2545{
2546	int ret = MAP_CONTINUE;
2547
2548	if (b->level) {
2549		struct bkey *k;
2550		struct btree_iter iter;
2551
2552		bch_btree_iter_init(&b->keys, &iter, from);
2553
2554		while ((k = bch_btree_iter_next_filter(&iter, &b->keys,
2555						       bch_ptr_bad))) {
2556			ret = bcache_btree(map_nodes_recurse, k, b,
2557				    op, from, fn, flags);
2558			from = NULL;
2559
2560			if (ret != MAP_CONTINUE)
2561				return ret;
2562		}
2563	}
2564
2565	if (!b->level || flags == MAP_ALL_NODES)
2566		ret = fn(op, b);
2567
2568	return ret;
2569}
2570
2571int __bch_btree_map_nodes(struct btree_op *op, struct cache_set *c,
2572			  struct bkey *from, btree_map_nodes_fn *fn, int flags)
2573{
2574	return bcache_btree_root(map_nodes_recurse, c, op, from, fn, flags);
2575}
2576
2577int bch_btree_map_keys_recurse(struct btree *b, struct btree_op *op,
2578				      struct bkey *from, btree_map_keys_fn *fn,
2579				      int flags)
2580{
2581	int ret = MAP_CONTINUE;
2582	struct bkey *k;
2583	struct btree_iter iter;
2584
2585	bch_btree_iter_init(&b->keys, &iter, from);
2586
2587	while ((k = bch_btree_iter_next_filter(&iter, &b->keys, bch_ptr_bad))) {
2588		ret = !b->level
2589			? fn(op, b, k)
2590			: bcache_btree(map_keys_recurse, k,
2591				       b, op, from, fn, flags);
2592		from = NULL;
2593
2594		if (ret != MAP_CONTINUE)
2595			return ret;
2596	}
2597
2598	if (!b->level && (flags & MAP_END_KEY))
2599		ret = fn(op, b, &KEY(KEY_INODE(&b->key),
2600				     KEY_OFFSET(&b->key), 0));
2601
2602	return ret;
2603}
2604
2605int bch_btree_map_keys(struct btree_op *op, struct cache_set *c,
2606		       struct bkey *from, btree_map_keys_fn *fn, int flags)
2607{
2608	return bcache_btree_root(map_keys_recurse, c, op, from, fn, flags);
2609}
2610
2611/* Keybuf code */
2612
2613static inline int keybuf_cmp(struct keybuf_key *l, struct keybuf_key *r)
2614{
2615	/* Overlapping keys compare equal */
2616	if (bkey_cmp(&l->key, &START_KEY(&r->key)) <= 0)
2617		return -1;
2618	if (bkey_cmp(&START_KEY(&l->key), &r->key) >= 0)
2619		return 1;
2620	return 0;
2621}
2622
2623static inline int keybuf_nonoverlapping_cmp(struct keybuf_key *l,
2624					    struct keybuf_key *r)
2625{
2626	return clamp_t(int64_t, bkey_cmp(&l->key, &r->key), -1, 1);
2627}
2628
2629struct refill {
2630	struct btree_op	op;
2631	unsigned int	nr_found;
2632	struct keybuf	*buf;
2633	struct bkey	*end;
2634	keybuf_pred_fn	*pred;
2635};
2636
2637static int refill_keybuf_fn(struct btree_op *op, struct btree *b,
2638			    struct bkey *k)
2639{
2640	struct refill *refill = container_of(op, struct refill, op);
2641	struct keybuf *buf = refill->buf;
2642	int ret = MAP_CONTINUE;
2643
2644	if (bkey_cmp(k, refill->end) > 0) {
2645		ret = MAP_DONE;
2646		goto out;
2647	}
2648
2649	if (!KEY_SIZE(k)) /* end key */
2650		goto out;
2651
2652	if (refill->pred(buf, k)) {
2653		struct keybuf_key *w;
2654
2655		spin_lock(&buf->lock);
2656
2657		w = array_alloc(&buf->freelist);
2658		if (!w) {
2659			spin_unlock(&buf->lock);
2660			return MAP_DONE;
2661		}
2662
2663		w->private = NULL;
2664		bkey_copy(&w->key, k);
2665
2666		if (RB_INSERT(&buf->keys, w, node, keybuf_cmp))
2667			array_free(&buf->freelist, w);
2668		else
2669			refill->nr_found++;
2670
2671		if (array_freelist_empty(&buf->freelist))
2672			ret = MAP_DONE;
2673
2674		spin_unlock(&buf->lock);
2675	}
2676out:
2677	buf->last_scanned = *k;
2678	return ret;
2679}
2680
2681void bch_refill_keybuf(struct cache_set *c, struct keybuf *buf,
2682		       struct bkey *end, keybuf_pred_fn *pred)
2683{
2684	struct bkey start = buf->last_scanned;
2685	struct refill refill;
2686
2687	cond_resched();
2688
2689	bch_btree_op_init(&refill.op, -1);
2690	refill.nr_found	= 0;
2691	refill.buf	= buf;
2692	refill.end	= end;
2693	refill.pred	= pred;
2694
2695	bch_btree_map_keys(&refill.op, c, &buf->last_scanned,
2696			   refill_keybuf_fn, MAP_END_KEY);
2697
2698	trace_bcache_keyscan(refill.nr_found,
2699			     KEY_INODE(&start), KEY_OFFSET(&start),
2700			     KEY_INODE(&buf->last_scanned),
2701			     KEY_OFFSET(&buf->last_scanned));
2702
2703	spin_lock(&buf->lock);
2704
2705	if (!RB_EMPTY_ROOT(&buf->keys)) {
2706		struct keybuf_key *w;
2707
2708		w = RB_FIRST(&buf->keys, struct keybuf_key, node);
2709		buf->start	= START_KEY(&w->key);
2710
2711		w = RB_LAST(&buf->keys, struct keybuf_key, node);
2712		buf->end	= w->key;
2713	} else {
2714		buf->start	= MAX_KEY;
2715		buf->end	= MAX_KEY;
2716	}
2717
2718	spin_unlock(&buf->lock);
2719}
2720
2721static void __bch_keybuf_del(struct keybuf *buf, struct keybuf_key *w)
2722{
2723	rb_erase(&w->node, &buf->keys);
2724	array_free(&buf->freelist, w);
2725}
2726
2727void bch_keybuf_del(struct keybuf *buf, struct keybuf_key *w)
2728{
2729	spin_lock(&buf->lock);
2730	__bch_keybuf_del(buf, w);
2731	spin_unlock(&buf->lock);
2732}
2733
2734bool bch_keybuf_check_overlapping(struct keybuf *buf, struct bkey *start,
2735				  struct bkey *end)
2736{
2737	bool ret = false;
2738	struct keybuf_key *p, *w, s;
2739
2740	s.key = *start;
2741
2742	if (bkey_cmp(end, &buf->start) <= 0 ||
2743	    bkey_cmp(start, &buf->end) >= 0)
2744		return false;
2745
2746	spin_lock(&buf->lock);
2747	w = RB_GREATER(&buf->keys, s, node, keybuf_nonoverlapping_cmp);
2748
2749	while (w && bkey_cmp(&START_KEY(&w->key), end) < 0) {
2750		p = w;
2751		w = RB_NEXT(w, node);
2752
2753		if (p->private)
2754			ret = true;
2755		else
2756			__bch_keybuf_del(buf, p);
2757	}
2758
2759	spin_unlock(&buf->lock);
2760	return ret;
2761}
2762
2763struct keybuf_key *bch_keybuf_next(struct keybuf *buf)
2764{
2765	struct keybuf_key *w;
2766
2767	spin_lock(&buf->lock);
2768
2769	w = RB_FIRST(&buf->keys, struct keybuf_key, node);
2770
2771	while (w && w->private)
2772		w = RB_NEXT(w, node);
2773
2774	if (w)
2775		w->private = ERR_PTR(-EINTR);
2776
2777	spin_unlock(&buf->lock);
2778	return w;
2779}
2780
2781struct keybuf_key *bch_keybuf_next_rescan(struct cache_set *c,
2782					  struct keybuf *buf,
2783					  struct bkey *end,
2784					  keybuf_pred_fn *pred)
2785{
2786	struct keybuf_key *ret;
2787
2788	while (1) {
2789		ret = bch_keybuf_next(buf);
2790		if (ret)
2791			break;
2792
2793		if (bkey_cmp(&buf->last_scanned, end) >= 0) {
2794			pr_debug("scan finished\n");
2795			break;
2796		}
2797
2798		bch_refill_keybuf(c, buf, end, pred);
2799	}
2800
2801	return ret;
2802}
2803
2804void bch_keybuf_init(struct keybuf *buf)
2805{
2806	buf->last_scanned	= MAX_KEY;
2807	buf->keys		= RB_ROOT;
2808
2809	spin_lock_init(&buf->lock);
2810	array_allocator_init(&buf->freelist);
2811}
2812
2813void bch_btree_exit(void)
2814{
2815	if (btree_io_wq)
2816		destroy_workqueue(btree_io_wq);
2817}
2818
2819int __init bch_btree_init(void)
2820{
2821	btree_io_wq = alloc_workqueue("bch_btree_io", WQ_MEM_RECLAIM, 0);
2822	if (!btree_io_wq)
2823		return -ENOMEM;
2824
2825	return 0;
2826}