Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2800 insertions, 0 deletions

diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
new file mode 100644
index 000000000..6a2f57ae0
--- /dev/null
+++ b/drivers/md/bcache/btree.c
@@ -0,0 +1,2800 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2010 Kent Overstreet <kent.overstreet@gmail.com>
+ *
+ * Uses a block device as cache for other block devices; optimized for SSDs.
+ * All allocation is done in buckets, which should match the erase block size
+ * of the device.
+ *
+ * Buckets containing cached data are kept on a heap sorted by priority;
+ * bucket priority is increased on cache hit, and periodically all the buckets
+ * on the heap have their priority scaled down. This currently is just used as
+ * an LRU but in the future should allow for more intelligent heuristics.
+ *
+ * Buckets have an 8 bit counter; freeing is accomplished by incrementing the
+ * counter. Garbage collection is used to remove stale pointers.
+ *
+ * Indexing is done via a btree; nodes are not necessarily fully sorted, rather
+ * as keys are inserted we only sort the pages that have not yet been written.
+ * When garbage collection is run, we resort the entire node.
+ *
+ * All configuration is done via sysfs; see Documentation/admin-guide/bcache.rst.
+ */
+
+#include "bcache.h"
+#include "btree.h"
+#include "debug.h"
+#include "extents.h"
+
+#include <linux/slab.h>
+#include <linux/bitops.h>
+#include <linux/hash.h>
+#include <linux/kthread.h>
+#include <linux/prefetch.h>
+#include <linux/random.h>
+#include <linux/rcupdate.h>
+#include <linux/sched/clock.h>
+#include <linux/rculist.h>
+#include <linux/delay.h>
+#include <trace/events/bcache.h>
+
+/*
+ * Todo:
+ * register_bcache: Return errors out to userspace correctly
+ *
+ * Writeback: don't undirty key until after a cache flush
+ *
+ * Create an iterator for key pointers
+ *
+ * On btree write error, mark bucket such that it won't be freed from the cache
+ *
+ * Journalling:
+ *   Check for bad keys in replay
+ *   Propagate barriers
+ *   Refcount journal entries in journal_replay
+ *
+ * Garbage collection:
+ *   Finish incremental gc
+ *   Gc should free old UUIDs, data for invalid UUIDs
+ *
+ * Provide a way to list backing device UUIDs we have data cached for, and
+ * probably how long it's been since we've seen them, and a way to invalidate
+ * dirty data for devices that will never be attached again
+ *
+ * Keep 1 min/5 min/15 min statistics of how busy a block device has been, so
+ * that based on that and how much dirty data we have we can keep writeback
+ * from being starved
+ *
+ * Add a tracepoint or somesuch to watch for writeback starvation
+ *
+ * When btree depth > 1 and splitting an interior node, we have to make sure
+ * alloc_bucket() cannot fail. This should be true but is not completely
+ * obvious.
+ *
+ * Plugging?
+ *
+ * If data write is less than hard sector size of ssd, round up offset in open
+ * bucket to the next whole sector
+ *
+ * Superblock needs to be fleshed out for multiple cache devices
+ *
+ * Add a sysfs tunable for the number of writeback IOs in flight
+ *
+ * Add a sysfs tunable for the number of open data buckets
+ *
+ * IO tracking: Can we track when one process is doing io on behalf of another?
+ * IO tracking: Don't use just an average, weigh more recent stuff higher
+ *
+ * Test module load/unload
+ */
+
+#define MAX_NEED_GC		64
+#define MAX_SAVE_PRIO		72
+#define MAX_GC_TIMES		100
+#define MIN_GC_NODES		100
+#define GC_SLEEP_MS		100
+
+#define PTR_DIRTY_BIT		(((uint64_t) 1 << 36))
+
+#define PTR_HASH(c, k)							\
+	(((k)->ptr[0] >> c->bucket_bits) | PTR_GEN(k, 0))
+
+static struct workqueue_struct *btree_io_wq;
+
+#define insert_lock(s, b)	((b)->level <= (s)->lock)
+
+
+static inline struct bset *write_block(struct btree *b)
+{
+	return ((void *) btree_bset_first(b)) + b->written * block_bytes(b->c->cache);
+}
+
+static void bch_btree_init_next(struct btree *b)
+{
+	/* If not a leaf node, always sort */
+	if (b->level && b->keys.nsets)
+		bch_btree_sort(&b->keys, &b->c->sort);
+	else
+		bch_btree_sort_lazy(&b->keys, &b->c->sort);
+
+	if (b->written < btree_blocks(b))
+		bch_bset_init_next(&b->keys, write_block(b),
+				   bset_magic(&b->c->cache->sb));
+
+}
+
+/* Btree key manipulation */
+
+void bkey_put(struct cache_set *c, struct bkey *k)
+{
+	unsigned int i;
+
+	for (i = 0; i < KEY_PTRS(k); i++)
+		if (ptr_available(c, k, i))
+			atomic_dec_bug(&PTR_BUCKET(c, k, i)->pin);
+}
+
+/* Btree IO */
+
+static uint64_t btree_csum_set(struct btree *b, struct bset *i)
+{
+	uint64_t crc = b->key.ptr[0];
+	void *data = (void *) i + 8, *end = bset_bkey_last(i);
+
+	crc = crc64_be(crc, data, end - data);
+	return crc ^ 0xffffffffffffffffULL;
+}
+
+void bch_btree_node_read_done(struct btree *b)
+{
+	const char *err = "bad btree header";
+	struct bset *i = btree_bset_first(b);
+	struct btree_iter *iter;
+
+	/*
+	 * c->fill_iter can allocate an iterator with more memory space
+	 * than static MAX_BSETS.
+	 * See the comment arount cache_set->fill_iter.
+	 */
+	iter = mempool_alloc(&b->c->fill_iter, GFP_NOIO);
+	iter->size = b->c->cache->sb.bucket_size / b->c->cache->sb.block_size;
+	iter->used = 0;
+
+#ifdef CONFIG_BCACHE_DEBUG
+	iter->b = &b->keys;
+#endif
+
+	if (!i->seq)
+		goto err;
+
+	for (;
+	     b->written < btree_blocks(b) && i->seq == b->keys.set[0].data->seq;
+	     i = write_block(b)) {
+		err = "unsupported bset version";
+		if (i->version > BCACHE_BSET_VERSION)
+			goto err;
+
+		err = "bad btree header";
+		if (b->written + set_blocks(i, block_bytes(b->c->cache)) >
+		    btree_blocks(b))
+			goto err;
+
+		err = "bad magic";
+		if (i->magic != bset_magic(&b->c->cache->sb))
+			goto err;
+
+		err = "bad checksum";
+		switch (i->version) {
+		case 0:
+			if (i->csum != csum_set(i))
+				goto err;
+			break;
+		case BCACHE_BSET_VERSION:
+			if (i->csum != btree_csum_set(b, i))
+				goto err;
+			break;
+		}
+
+		err = "empty set";
+		if (i != b->keys.set[0].data && !i->keys)
+			goto err;
+
+		bch_btree_iter_push(iter, i->start, bset_bkey_last(i));
+
+		b->written += set_blocks(i, block_bytes(b->c->cache));
+	}
+
+	err = "corrupted btree";
+	for (i = write_block(b);
+	     bset_sector_offset(&b->keys, i) < KEY_SIZE(&b->key);
+	     i = ((void *) i) + block_bytes(b->c->cache))
+		if (i->seq == b->keys.set[0].data->seq)
+			goto err;
+
+	bch_btree_sort_and_fix_extents(&b->keys, iter, &b->c->sort);
+
+	i = b->keys.set[0].data;
+	err = "short btree key";
+	if (b->keys.set[0].size &&
+	    bkey_cmp(&b->key, &b->keys.set[0].end) < 0)
+		goto err;
+
+	if (b->written < btree_blocks(b))
+		bch_bset_init_next(&b->keys, write_block(b),
+				   bset_magic(&b->c->cache->sb));
+out:
+	mempool_free(iter, &b->c->fill_iter);
+	return;
+err:
+	set_btree_node_io_error(b);
+	bch_cache_set_error(b->c, "%s at bucket %zu, block %u, %u keys",
+			    err, PTR_BUCKET_NR(b->c, &b->key, 0),
+			    bset_block_offset(b, i), i->keys);
+	goto out;
+}
+
+static void btree_node_read_endio(struct bio *bio)
+{
+	struct closure *cl = bio->bi_private;
+
+	closure_put(cl);
+}
+
+static void bch_btree_node_read(struct btree *b)
+{
+	uint64_t start_time = local_clock();
+	struct closure cl;
+	struct bio *bio;
+
+	trace_bcache_btree_read(b);
+
+	closure_init_stack(&cl);
+
+	bio = bch_bbio_alloc(b->c);
+	bio->bi_iter.bi_size = KEY_SIZE(&b->key) << 9;
+	bio->bi_end_io	= btree_node_read_endio;
+	bio->bi_private	= &cl;
+	bio->bi_opf = REQ_OP_READ | REQ_META;
+
+	bch_bio_map(bio, b->keys.set[0].data);
+
+	bch_submit_bbio(bio, b->c, &b->key, 0);
+	closure_sync(&cl);
+
+	if (bio->bi_status)
+		set_btree_node_io_error(b);
+
+	bch_bbio_free(bio, b->c);
+
+	if (btree_node_io_error(b))
+		goto err;
+
+	bch_btree_node_read_done(b);
+	bch_time_stats_update(&b->c->btree_read_time, start_time);
+
+	return;
+err:
+	bch_cache_set_error(b->c, "io error reading bucket %zu",
+			    PTR_BUCKET_NR(b->c, &b->key, 0));
+}
+
+static void btree_complete_write(struct btree *b, struct btree_write *w)
+{
+	if (w->prio_blocked &&
+	    !atomic_sub_return(w->prio_blocked, &b->c->prio_blocked))
+		wake_up_allocators(b->c);
+
+	if (w->journal) {
+		atomic_dec_bug(w->journal);
+		__closure_wake_up(&b->c->journal.wait);
+	}
+
+	w->prio_blocked	= 0;
+	w->journal	= NULL;
+}
+
+static void btree_node_write_unlock(struct closure *cl)
+{
+	struct btree *b = container_of(cl, struct btree, io);
+
+	up(&b->io_mutex);
+}
+
+static void __btree_node_write_done(struct closure *cl)
+{
+	struct btree *b = container_of(cl, struct btree, io);
+	struct btree_write *w = btree_prev_write(b);
+
+	bch_bbio_free(b->bio, b->c);
+	b->bio = NULL;
+	btree_complete_write(b, w);
+
+	if (btree_node_dirty(b))
+		queue_delayed_work(btree_io_wq, &b->work, 30 * HZ);
+
+	closure_return_with_destructor(cl, btree_node_write_unlock);
+}
+
+static void btree_node_write_done(struct closure *cl)
+{
+	struct btree *b = container_of(cl, struct btree, io);
+
+	bio_free_pages(b->bio);
+	__btree_node_write_done(cl);
+}
+
+static void btree_node_write_endio(struct bio *bio)
+{
+	struct closure *cl = bio->bi_private;
+	struct btree *b = container_of(cl, struct btree, io);
+
+	if (bio->bi_status)
+		set_btree_node_io_error(b);
+
+	bch_bbio_count_io_errors(b->c, bio, bio->bi_status, "writing btree");
+	closure_put(cl);
+}
+
+static void do_btree_node_write(struct btree *b)
+{
+	struct closure *cl = &b->io;
+	struct bset *i = btree_bset_last(b);
+	BKEY_PADDED(key) k;
+
+	i->version	= BCACHE_BSET_VERSION;
+	i->csum		= btree_csum_set(b, i);
+
+	BUG_ON(b->bio);
+	b->bio = bch_bbio_alloc(b->c);
+
+	b->bio->bi_end_io	= btree_node_write_endio;
+	b->bio->bi_private	= cl;
+	b->bio->bi_iter.bi_size	= roundup(set_bytes(i), block_bytes(b->c->cache));
+	b->bio->bi_opf		= REQ_OP_WRITE | REQ_META | REQ_FUA;
+	bch_bio_map(b->bio, i);
+
+	/*
+	 * If we're appending to a leaf node, we don't technically need FUA -
+	 * this write just needs to be persisted before the next journal write,
+	 * which will be marked FLUSH|FUA.
+	 *
+	 * Similarly if we're writing a new btree root - the pointer is going to
+	 * be in the next journal entry.
+	 *
+	 * But if we're writing a new btree node (that isn't a root) or
+	 * appending to a non leaf btree node, we need either FUA or a flush
+	 * when we write the parent with the new pointer. FUA is cheaper than a
+	 * flush, and writes appending to leaf nodes aren't blocking anything so
+	 * just make all btree node writes FUA to keep things sane.
+	 */
+
+	bkey_copy(&k.key, &b->key);
+	SET_PTR_OFFSET(&k.key, 0, PTR_OFFSET(&k.key, 0) +
+		       bset_sector_offset(&b->keys, i));
+
+	if (!bch_bio_alloc_pages(b->bio, __GFP_NOWARN|GFP_NOWAIT)) {
+		struct bio_vec *bv;
+		void *addr = (void *) ((unsigned long) i & ~(PAGE_SIZE - 1));
+		struct bvec_iter_all iter_all;
+
+		bio_for_each_segment_all(bv, b->bio, iter_all) {
+			memcpy(page_address(bv->bv_page), addr, PAGE_SIZE);
+			addr += PAGE_SIZE;
+		}
+
+		bch_submit_bbio(b->bio, b->c, &k.key, 0);
+
+		continue_at(cl, btree_node_write_done, NULL);
+	} else {
+		/*
+		 * No problem for multipage bvec since the bio is
+		 * just allocated
+		 */
+		b->bio->bi_vcnt = 0;
+		bch_bio_map(b->bio, i);
+
+		bch_submit_bbio(b->bio, b->c, &k.key, 0);
+
+		closure_sync(cl);
+		continue_at_nobarrier(cl, __btree_node_write_done, NULL);
+	}
+}
+
+void __bch_btree_node_write(struct btree *b, struct closure *parent)
+{
+	struct bset *i = btree_bset_last(b);
+
+	lockdep_assert_held(&b->write_lock);
+
+	trace_bcache_btree_write(b);
+
+	BUG_ON(current->bio_list);
+	BUG_ON(b->written >= btree_blocks(b));
+	BUG_ON(b->written && !i->keys);
+	BUG_ON(btree_bset_first(b)->seq != i->seq);
+	bch_check_keys(&b->keys, "writing");
+
+	cancel_delayed_work(&b->work);
+
+	/* If caller isn't waiting for write, parent refcount is cache set */
+	down(&b->io_mutex);
+	closure_init(&b->io, parent ?: &b->c->cl);
+
+	clear_bit(BTREE_NODE_dirty,	 &b->flags);
+	change_bit(BTREE_NODE_write_idx, &b->flags);
+
+	do_btree_node_write(b);
+
+	atomic_long_add(set_blocks(i, block_bytes(b->c->cache)) * b->c->cache->sb.block_size,
+			&b->c->cache->btree_sectors_written);
+
+	b->written += set_blocks(i, block_bytes(b->c->cache));
+}
+
+void bch_btree_node_write(struct btree *b, struct closure *parent)
+{
+	unsigned int nsets = b->keys.nsets;
+
+	lockdep_assert_held(&b->lock);
+
+	__bch_btree_node_write(b, parent);
+
+	/*
+	 * do verify if there was more than one set initially (i.e. we did a
+	 * sort) and we sorted down to a single set:
+	 */
+	if (nsets && !b->keys.nsets)
+		bch_btree_verify(b);
+
+	bch_btree_init_next(b);
+}
+
+static void bch_btree_node_write_sync(struct btree *b)
+{
+	struct closure cl;
+
+	closure_init_stack(&cl);
+
+	mutex_lock(&b->write_lock);
+	bch_btree_node_write(b, &cl);
+	mutex_unlock(&b->write_lock);
+
+	closure_sync(&cl);
+}
+
+static void btree_node_write_work(struct work_struct *w)
+{
+	struct btree *b = container_of(to_delayed_work(w), struct btree, work);
+
+	mutex_lock(&b->write_lock);
+	if (btree_node_dirty(b))
+		__bch_btree_node_write(b, NULL);
+	mutex_unlock(&b->write_lock);
+}
+
+static void bch_btree_leaf_dirty(struct btree *b, atomic_t *journal_ref)
+{
+	struct bset *i = btree_bset_last(b);
+	struct btree_write *w = btree_current_write(b);
+
+	lockdep_assert_held(&b->write_lock);
+
+	BUG_ON(!b->written);
+	BUG_ON(!i->keys);
+
+	if (!btree_node_dirty(b))
+		queue_delayed_work(btree_io_wq, &b->work, 30 * HZ);
+
+	set_btree_node_dirty(b);
+
+	/*
+	 * w->journal is always the oldest journal pin of all bkeys
+	 * in the leaf node, to make sure the oldest jset seq won't
+	 * be increased before this btree node is flushed.
+	 */
+	if (journal_ref) {
+		if (w->journal &&
+		    journal_pin_cmp(b->c, w->journal, journal_ref)) {
+			atomic_dec_bug(w->journal);
+			w->journal = NULL;
+		}
+
+		if (!w->journal) {
+			w->journal = journal_ref;
+			atomic_inc(w->journal);
+		}
+	}
+
+	/* Force write if set is too big */
+	if (set_bytes(i) > PAGE_SIZE - 48 &&
+	    !current->bio_list)
+		bch_btree_node_write(b, NULL);
+}
+
+/*
+ * Btree in memory cache - allocation/freeing
+ * mca -> memory cache
+ */
+
+#define mca_reserve(c)	(((!IS_ERR_OR_NULL(c->root) && c->root->level) \
+			  ? c->root->level : 1) * 8 + 16)
+#define mca_can_free(c)						\
+	max_t(int, 0, c->btree_cache_used - mca_reserve(c))
+
+static void mca_data_free(struct btree *b)
+{
+	BUG_ON(b->io_mutex.count != 1);
+
+	bch_btree_keys_free(&b->keys);
+
+	b->c->btree_cache_used--;
+	list_move(&b->list, &b->c->btree_cache_freed);
+}
+
+static void mca_bucket_free(struct btree *b)
+{
+	BUG_ON(btree_node_dirty(b));
+
+	b->key.ptr[0] = 0;
+	hlist_del_init_rcu(&b->hash);
+	list_move(&b->list, &b->c->btree_cache_freeable);
+}
+
+static unsigned int btree_order(struct bkey *k)
+{
+	return ilog2(KEY_SIZE(k) / PAGE_SECTORS ?: 1);
+}
+
+static void mca_data_alloc(struct btree *b, struct bkey *k, gfp_t gfp)
+{
+	if (!bch_btree_keys_alloc(&b->keys,
+				  max_t(unsigned int,
+					ilog2(b->c->btree_pages),
+					btree_order(k)),
+				  gfp)) {
+		b->c->btree_cache_used++;
+		list_move(&b->list, &b->c->btree_cache);
+	} else {
+		list_move(&b->list, &b->c->btree_cache_freed);
+	}
+}
+
+static struct btree *mca_bucket_alloc(struct cache_set *c,
+				      struct bkey *k, gfp_t gfp)
+{
+	/*
+	 * kzalloc() is necessary here for initialization,
+	 * see code comments in bch_btree_keys_init().
+	 */
+	struct btree *b = kzalloc(sizeof(struct btree), gfp);
+
+	if (!b)
+		return NULL;
+
+	init_rwsem(&b->lock);
+	lockdep_set_novalidate_class(&b->lock);
+	mutex_init(&b->write_lock);
+	lockdep_set_novalidate_class(&b->write_lock);
+	INIT_LIST_HEAD(&b->list);
+	INIT_DELAYED_WORK(&b->work, btree_node_write_work);
+	b->c = c;
+	sema_init(&b->io_mutex, 1);
+
+	mca_data_alloc(b, k, gfp);
+	return b;
+}
+
+static int mca_reap(struct btree *b, unsigned int min_order, bool flush)
+{
+	struct closure cl;
+
+	closure_init_stack(&cl);
+	lockdep_assert_held(&b->c->bucket_lock);
+
+	if (!down_write_trylock(&b->lock))
+		return -ENOMEM;
+
+	BUG_ON(btree_node_dirty(b) && !b->keys.set[0].data);
+
+	if (b->keys.page_order < min_order)
+		goto out_unlock;
+
+	if (!flush) {
+		if (btree_node_dirty(b))
+			goto out_unlock;
+
+		if (down_trylock(&b->io_mutex))
+			goto out_unlock;
+		up(&b->io_mutex);
+	}
+
+retry:
+	/*
+	 * BTREE_NODE_dirty might be cleared in btree_flush_btree() by
+	 * __bch_btree_node_write(). To avoid an extra flush, acquire
+	 * b->write_lock before checking BTREE_NODE_dirty bit.
+	 */
+	mutex_lock(&b->write_lock);
+	/*
+	 * If this btree node is selected in btree_flush_write() by journal
+	 * code, delay and retry until the node is flushed by journal code
+	 * and BTREE_NODE_journal_flush bit cleared by btree_flush_write().
+	 */
+	if (btree_node_journal_flush(b)) {
+		pr_debug("bnode %p is flushing by journal, retry\n", b);
+		mutex_unlock(&b->write_lock);
+		udelay(1);
+		goto retry;
+	}
+
+	if (btree_node_dirty(b))
+		__bch_btree_node_write(b, &cl);
+	mutex_unlock(&b->write_lock);
+
+	closure_sync(&cl);
+
+	/* wait for any in flight btree write */
+	down(&b->io_mutex);
+	up(&b->io_mutex);
+
+	return 0;
+out_unlock:
+	rw_unlock(true, b);
+	return -ENOMEM;
+}
+
+static unsigned long bch_mca_scan(struct shrinker *shrink,
+				  struct shrink_control *sc)
+{
+	struct cache_set *c = container_of(shrink, struct cache_set, shrink);
+	struct btree *b, *t;
+	unsigned long i, nr = sc->nr_to_scan;
+	unsigned long freed = 0;
+	unsigned int btree_cache_used;
+
+	if (c->shrinker_disabled)
+		return SHRINK_STOP;
+
+	if (c->btree_cache_alloc_lock)
+		return SHRINK_STOP;
+
+	/* Return -1 if we can't do anything right now */
+	if (sc->gfp_mask & __GFP_IO)
+		mutex_lock(&c->bucket_lock);
+	else if (!mutex_trylock(&c->bucket_lock))
+		return -1;
+
+	/*
+	 * It's _really_ critical that we don't free too many btree nodes - we
+	 * have to always leave ourselves a reserve. The reserve is how we
+	 * guarantee that allocating memory for a new btree node can always
+	 * succeed, so that inserting keys into the btree can always succeed and
+	 * IO can always make forward progress:
+	 */
+	nr /= c->btree_pages;
+	if (nr == 0)
+		nr = 1;
+	nr = min_t(unsigned long, nr, mca_can_free(c));
+
+	i = 0;
+	btree_cache_used = c->btree_cache_used;
+	list_for_each_entry_safe_reverse(b, t, &c->btree_cache_freeable, list) {
+		if (nr <= 0)
+			goto out;
+
+		if (!mca_reap(b, 0, false)) {
+			mca_data_free(b);
+			rw_unlock(true, b);
+			freed++;
+		}
+		nr--;
+		i++;
+	}
+
+	list_for_each_entry_safe_reverse(b, t, &c->btree_cache, list) {
+		if (nr <= 0 || i >= btree_cache_used)
+			goto out;
+
+		if (!mca_reap(b, 0, false)) {
+			mca_bucket_free(b);
+			mca_data_free(b);
+			rw_unlock(true, b);
+			freed++;
+		}
+
+		nr--;
+		i++;
+	}
+out:
+	mutex_unlock(&c->bucket_lock);
+	return freed * c->btree_pages;
+}
+
+static unsigned long bch_mca_count(struct shrinker *shrink,
+				   struct shrink_control *sc)
+{
+	struct cache_set *c = container_of(shrink, struct cache_set, shrink);
+
+	if (c->shrinker_disabled)
+		return 0;
+
+	if (c->btree_cache_alloc_lock)
+		return 0;
+
+	return mca_can_free(c) * c->btree_pages;
+}
+
+void bch_btree_cache_free(struct cache_set *c)
+{
+	struct btree *b;
+	struct closure cl;
+
+	closure_init_stack(&cl);
+
+	if (c->shrink.list.next)
+		unregister_shrinker(&c->shrink);
+
+	mutex_lock(&c->bucket_lock);
+
+#ifdef CONFIG_BCACHE_DEBUG
+	if (c->verify_data)
+		list_move(&c->verify_data->list, &c->btree_cache);
+
+	free_pages((unsigned long) c->verify_ondisk, ilog2(meta_bucket_pages(&c->cache->sb)));
+#endif
+
+	list_splice(&c->btree_cache_freeable,
+		    &c->btree_cache);
+
+	while (!list_empty(&c->btree_cache)) {
+		b = list_first_entry(&c->btree_cache, struct btree, list);
+
+		/*
+		 * This function is called by cache_set_free(), no I/O
+		 * request on cache now, it is unnecessary to acquire
+		 * b->write_lock before clearing BTREE_NODE_dirty anymore.
+		 */
+		if (btree_node_dirty(b)) {
+			btree_complete_write(b, btree_current_write(b));
+			clear_bit(BTREE_NODE_dirty, &b->flags);
+		}
+		mca_data_free(b);
+	}
+
+	while (!list_empty(&c->btree_cache_freed)) {
+		b = list_first_entry(&c->btree_cache_freed,
+				     struct btree, list);
+		list_del(&b->list);
+		cancel_delayed_work_sync(&b->work);
+		kfree(b);
+	}
+
+	mutex_unlock(&c->bucket_lock);
+}
+
+int bch_btree_cache_alloc(struct cache_set *c)
+{
+	unsigned int i;
+
+	for (i = 0; i < mca_reserve(c); i++)
+		if (!mca_bucket_alloc(c, &ZERO_KEY, GFP_KERNEL))
+			return -ENOMEM;
+
+	list_splice_init(&c->btree_cache,
+			 &c->btree_cache_freeable);
+
+#ifdef CONFIG_BCACHE_DEBUG
+	mutex_init(&c->verify_lock);
+
+	c->verify_ondisk = (void *)
+		__get_free_pages(GFP_KERNEL|__GFP_COMP,
+				 ilog2(meta_bucket_pages(&c->cache->sb)));
+	if (!c->verify_ondisk) {
+		/*
+		 * Don't worry about the mca_rereserve buckets
+		 * allocated in previous for-loop, they will be
+		 * handled properly in bch_cache_set_unregister().
+		 */
+		return -ENOMEM;
+	}
+
+	c->verify_data = mca_bucket_alloc(c, &ZERO_KEY, GFP_KERNEL);
+
+	if (c->verify_data &&
+	    c->verify_data->keys.set->data)
+		list_del_init(&c->verify_data->list);
+	else
+		c->verify_data = NULL;
+#endif
+
+	c->shrink.count_objects = bch_mca_count;
+	c->shrink.scan_objects = bch_mca_scan;
+	c->shrink.seeks = 4;
+	c->shrink.batch = c->btree_pages * 2;
+
+	if (register_shrinker(&c->shrink, "md-bcache:%pU", c->set_uuid))
+		pr_warn("bcache: %s: could not register shrinker\n",
+				__func__);
+
+	return 0;
+}
+
+/* Btree in memory cache - hash table */
+
+static struct hlist_head *mca_hash(struct cache_set *c, struct bkey *k)
+{
+	return &c->bucket_hash[hash_32(PTR_HASH(c, k), BUCKET_HASH_BITS)];
+}
+
+static struct btree *mca_find(struct cache_set *c, struct bkey *k)
+{
+	struct btree *b;
+
+	rcu_read_lock();
+	hlist_for_each_entry_rcu(b, mca_hash(c, k), hash)
+		if (PTR_HASH(c, &b->key) == PTR_HASH(c, k))
+			goto out;
+	b = NULL;
+out:
+	rcu_read_unlock();
+	return b;
+}
+
+static int mca_cannibalize_lock(struct cache_set *c, struct btree_op *op)
+{
+	spin_lock(&c->btree_cannibalize_lock);
+	if (likely(c->btree_cache_alloc_lock == NULL)) {
+		c->btree_cache_alloc_lock = current;
+	} else if (c->btree_cache_alloc_lock != current) {
+		if (op)
+			prepare_to_wait(&c->btree_cache_wait, &op->wait,
+					TASK_UNINTERRUPTIBLE);
+		spin_unlock(&c->btree_cannibalize_lock);
+		return -EINTR;
+	}
+	spin_unlock(&c->btree_cannibalize_lock);
+
+	return 0;
+}
+
+static struct btree *mca_cannibalize(struct cache_set *c, struct btree_op *op,
+				     struct bkey *k)
+{
+	struct btree *b;
+
+	trace_bcache_btree_cache_cannibalize(c);
+
+	if (mca_cannibalize_lock(c, op))
+		return ERR_PTR(-EINTR);
+
+	list_for_each_entry_reverse(b, &c->btree_cache, list)
+		if (!mca_reap(b, btree_order(k), false))
+			return b;
+
+	list_for_each_entry_reverse(b, &c->btree_cache, list)
+		if (!mca_reap(b, btree_order(k), true))
+			return b;
+
+	WARN(1, "btree cache cannibalize failed\n");
+	return ERR_PTR(-ENOMEM);
+}
+
+/*
+ * We can only have one thread cannibalizing other cached btree nodes at a time,
+ * or we'll deadlock. We use an open coded mutex to ensure that, which a
+ * cannibalize_bucket() will take. This means every time we unlock the root of
+ * the btree, we need to release this lock if we have it held.
+ */
+void bch_cannibalize_unlock(struct cache_set *c)
+{
+	spin_lock(&c->btree_cannibalize_lock);
+	if (c->btree_cache_alloc_lock == current) {
+		c->btree_cache_alloc_lock = NULL;
+		wake_up(&c->btree_cache_wait);
+	}
+	spin_unlock(&c->btree_cannibalize_lock);
+}
+
+static struct btree *mca_alloc(struct cache_set *c, struct btree_op *op,
+			       struct bkey *k, int level)
+{
+	struct btree *b;
+
+	BUG_ON(current->bio_list);
+
+	lockdep_assert_held(&c->bucket_lock);
+
+	if (mca_find(c, k))
+		return NULL;
+
+	/* btree_free() doesn't free memory; it sticks the node on the end of
+	 * the list. Check if there's any freed nodes there:
+	 */
+	list_for_each_entry(b, &c->btree_cache_freeable, list)
+		if (!mca_reap(b, btree_order(k), false))
+			goto out;
+
+	/* We never free struct btree itself, just the memory that holds the on
+	 * disk node. Check the freed list before allocating a new one:
+	 */
+	list_for_each_entry(b, &c->btree_cache_freed, list)
+		if (!mca_reap(b, 0, false)) {
+			mca_data_alloc(b, k, __GFP_NOWARN|GFP_NOIO);
+			if (!b->keys.set[0].data)
+				goto err;
+			else
+				goto out;
+		}
+
+	b = mca_bucket_alloc(c, k, __GFP_NOWARN|GFP_NOIO);
+	if (!b)
+		goto err;
+
+	BUG_ON(!down_write_trylock(&b->lock));
+	if (!b->keys.set->data)
+		goto err;
+out:
+	BUG_ON(b->io_mutex.count != 1);
+
+	bkey_copy(&b->key, k);
+	list_move(&b->list, &c->btree_cache);
+	hlist_del_init_rcu(&b->hash);
+	hlist_add_head_rcu(&b->hash, mca_hash(c, k));
+
+	lock_set_subclass(&b->lock.dep_map, level + 1, _THIS_IP_);
+	b->parent	= (void *) ~0UL;
+	b->flags	= 0;
+	b->written	= 0;
+	b->level	= level;
+
+	if (!b->level)
+		bch_btree_keys_init(&b->keys, &bch_extent_keys_ops,
+				    &b->c->expensive_debug_checks);
+	else
+		bch_btree_keys_init(&b->keys, &bch_btree_keys_ops,
+				    &b->c->expensive_debug_checks);
+
+	return b;
+err:
+	if (b)
+		rw_unlock(true, b);
+
+	b = mca_cannibalize(c, op, k);
+	if (!IS_ERR(b))
+		goto out;
+
+	return b;
+}
+
+/*
+ * bch_btree_node_get - find a btree node in the cache and lock it, reading it
+ * in from disk if necessary.
+ *
+ * If IO is necessary and running under submit_bio_noacct, returns -EAGAIN.
+ *
+ * The btree node will have either a read or a write lock held, depending on
+ * level and op->lock.
+ *
+ * Note: Only error code or btree pointer will be returned, it is unncessary
+ *       for callers to check NULL pointer.
+ */
+struct btree *bch_btree_node_get(struct cache_set *c, struct btree_op *op,
+				 struct bkey *k, int level, bool write,
+				 struct btree *parent)
+{
+	int i = 0;
+	struct btree *b;
+
+	BUG_ON(level < 0);
+retry:
+	b = mca_find(c, k);
+
+	if (!b) {
+		if (current->bio_list)
+			return ERR_PTR(-EAGAIN);
+
+		mutex_lock(&c->bucket_lock);
+		b = mca_alloc(c, op, k, level);
+		mutex_unlock(&c->bucket_lock);
+
+		if (!b)
+			goto retry;
+		if (IS_ERR(b))
+			return b;
+
+		bch_btree_node_read(b);
+
+		if (!write)
+			downgrade_write(&b->lock);
+	} else {
+		rw_lock(write, b, level);
+		if (PTR_HASH(c, &b->key) != PTR_HASH(c, k)) {
+			rw_unlock(write, b);
+			goto retry;
+		}
+		BUG_ON(b->level != level);
+	}
+
+	if (btree_node_io_error(b)) {
+		rw_unlock(write, b);
+		return ERR_PTR(-EIO);
+	}
+
+	BUG_ON(!b->written);
+
+	b->parent = parent;
+
+	for (; i <= b->keys.nsets && b->keys.set[i].size; i++) {
+		prefetch(b->keys.set[i].tree);
+		prefetch(b->keys.set[i].data);
+	}
+
+	for (; i <= b->keys.nsets; i++)
+		prefetch(b->keys.set[i].data);
+
+	return b;
+}
+
+static void btree_node_prefetch(struct btree *parent, struct bkey *k)
+{
+	struct btree *b;
+
+	mutex_lock(&parent->c->bucket_lock);
+	b = mca_alloc(parent->c, NULL, k, parent->level - 1);
+	mutex_unlock(&parent->c->bucket_lock);
+
+	if (!IS_ERR_OR_NULL(b)) {
+		b->parent = parent;
+		bch_btree_node_read(b);
+		rw_unlock(true, b);
+	}
+}
+
+/* Btree alloc */
+
+static void btree_node_free(struct btree *b)
+{
+	trace_bcache_btree_node_free(b);
+
+	BUG_ON(b == b->c->root);
+
+retry:
+	mutex_lock(&b->write_lock);
+	/*
+	 * If the btree node is selected and flushing in btree_flush_write(),
+	 * delay and retry until the BTREE_NODE_journal_flush bit cleared,
+	 * then it is safe to free the btree node here. Otherwise this btree
+	 * node will be in race condition.
+	 */
+	if (btree_node_journal_flush(b)) {
+		mutex_unlock(&b->write_lock);
+		pr_debug("bnode %p journal_flush set, retry\n", b);
+		udelay(1);
+		goto retry;
+	}
+
+	if (btree_node_dirty(b)) {
+		btree_complete_write(b, btree_current_write(b));
+		clear_bit(BTREE_NODE_dirty, &b->flags);
+	}
+
+	mutex_unlock(&b->write_lock);
+
+	cancel_delayed_work(&b->work);
+
+	mutex_lock(&b->c->bucket_lock);
+	bch_bucket_free(b->c, &b->key);
+	mca_bucket_free(b);
+	mutex_unlock(&b->c->bucket_lock);
+}
+
+/*
+ * Only error code or btree pointer will be returned, it is unncessary for
+ * callers to check NULL pointer.
+ */
+struct btree *__bch_btree_node_alloc(struct cache_set *c, struct btree_op *op,
+				     int level, bool wait,
+				     struct btree *parent)
+{
+	BKEY_PADDED(key) k;
+	struct btree *b;
+
+	mutex_lock(&c->bucket_lock);
+retry:
+	/* return ERR_PTR(-EAGAIN) when it fails */
+	b = ERR_PTR(-EAGAIN);
+	if (__bch_bucket_alloc_set(c, RESERVE_BTREE, &k.key, wait))
+		goto err;
+
+	bkey_put(c, &k.key);
+	SET_KEY_SIZE(&k.key, c->btree_pages * PAGE_SECTORS);
+
+	b = mca_alloc(c, op, &k.key, level);
+	if (IS_ERR(b))
+		goto err_free;
+
+	if (!b) {
+		cache_bug(c,
+			"Tried to allocate bucket that was in btree cache");
+		goto retry;
+	}
+
+	b->parent = parent;
+	bch_bset_init_next(&b->keys, b->keys.set->data, bset_magic(&b->c->cache->sb));
+
+	mutex_unlock(&c->bucket_lock);
+
+	trace_bcache_btree_node_alloc(b);
+	return b;
+err_free:
+	bch_bucket_free(c, &k.key);
+err:
+	mutex_unlock(&c->bucket_lock);
+
+	trace_bcache_btree_node_alloc_fail(c);
+	return b;
+}
+
+static struct btree *bch_btree_node_alloc(struct cache_set *c,
+					  struct btree_op *op, int level,
+					  struct btree *parent)
+{
+	return __bch_btree_node_alloc(c, op, level, op != NULL, parent);
+}
+
+static struct btree *btree_node_alloc_replacement(struct btree *b,
+						  struct btree_op *op)
+{
+	struct btree *n = bch_btree_node_alloc(b->c, op, b->level, b->parent);
+
+	if (!IS_ERR(n)) {
+		mutex_lock(&n->write_lock);
+		bch_btree_sort_into(&b->keys, &n->keys, &b->c->sort);
+		bkey_copy_key(&n->key, &b->key);
+		mutex_unlock(&n->write_lock);
+	}
+
+	return n;
+}
+
+static void make_btree_freeing_key(struct btree *b, struct bkey *k)
+{
+	unsigned int i;
+
+	mutex_lock(&b->c->bucket_lock);
+
+	atomic_inc(&b->c->prio_blocked);
+
+	bkey_copy(k, &b->key);
+	bkey_copy_key(k, &ZERO_KEY);
+
+	for (i = 0; i < KEY_PTRS(k); i++)
+		SET_PTR_GEN(k, i,
+			    bch_inc_gen(b->c->cache,
+					PTR_BUCKET(b->c, &b->key, i)));
+
+	mutex_unlock(&b->c->bucket_lock);
+}
+
+static int btree_check_reserve(struct btree *b, struct btree_op *op)
+{
+	struct cache_set *c = b->c;
+	struct cache *ca = c->cache;
+	unsigned int reserve = (c->root->level - b->level) * 2 + 1;
+
+	mutex_lock(&c->bucket_lock);
+
+	if (fifo_used(&ca->free[RESERVE_BTREE]) < reserve) {
+		if (op)
+			prepare_to_wait(&c->btree_cache_wait, &op->wait,
+					TASK_UNINTERRUPTIBLE);
+		mutex_unlock(&c->bucket_lock);
+		return -EINTR;
+	}
+
+	mutex_unlock(&c->bucket_lock);
+
+	return mca_cannibalize_lock(b->c, op);
+}
+
+/* Garbage collection */
+
+static uint8_t __bch_btree_mark_key(struct cache_set *c, int level,
+				    struct bkey *k)
+{
+	uint8_t stale = 0;
+	unsigned int i;
+	struct bucket *g;
+
+	/*
+	 * ptr_invalid() can't return true for the keys that mark btree nodes as
+	 * freed, but since ptr_bad() returns true we'll never actually use them
+	 * for anything and thus we don't want mark their pointers here
+	 */
+	if (!bkey_cmp(k, &ZERO_KEY))
+		return stale;
+
+	for (i = 0; i < KEY_PTRS(k); i++) {
+		if (!ptr_available(c, k, i))
+			continue;
+
+		g = PTR_BUCKET(c, k, i);
+
+		if (gen_after(g->last_gc, PTR_GEN(k, i)))
+			g->last_gc = PTR_GEN(k, i);
+
+		if (ptr_stale(c, k, i)) {
+			stale = max(stale, ptr_stale(c, k, i));
+			continue;
+		}
+
+		cache_bug_on(GC_MARK(g) &&
+			     (GC_MARK(g) == GC_MARK_METADATA) != (level != 0),
+			     c, "inconsistent ptrs: mark = %llu, level = %i",
+			     GC_MARK(g), level);
+
+		if (level)
+			SET_GC_MARK(g, GC_MARK_METADATA);
+		else if (KEY_DIRTY(k))
+			SET_GC_MARK(g, GC_MARK_DIRTY);
+		else if (!GC_MARK(g))
+			SET_GC_MARK(g, GC_MARK_RECLAIMABLE);
+
+		/* guard against overflow */
+		SET_GC_SECTORS_USED(g, min_t(unsigned int,
+					     GC_SECTORS_USED(g) + KEY_SIZE(k),
+					     MAX_GC_SECTORS_USED));
+
+		BUG_ON(!GC_SECTORS_USED(g));
+	}
+
+	return stale;
+}
+
+#define btree_mark_key(b, k)	__bch_btree_mark_key(b->c, b->level, k)
+
+void bch_initial_mark_key(struct cache_set *c, int level, struct bkey *k)
+{
+	unsigned int i;
+
+	for (i = 0; i < KEY_PTRS(k); i++)
+		if (ptr_available(c, k, i) &&
+		    !ptr_stale(c, k, i)) {
+			struct bucket *b = PTR_BUCKET(c, k, i);
+
+			b->gen = PTR_GEN(k, i);
+
+			if (level && bkey_cmp(k, &ZERO_KEY))
+				b->prio = BTREE_PRIO;
+			else if (!level && b->prio == BTREE_PRIO)
+				b->prio = INITIAL_PRIO;
+		}
+
+	__bch_btree_mark_key(c, level, k);
+}
+
+void bch_update_bucket_in_use(struct cache_set *c, struct gc_stat *stats)
+{
+	stats->in_use = (c->nbuckets - c->avail_nbuckets) * 100 / c->nbuckets;
+}
+
+static bool btree_gc_mark_node(struct btree *b, struct gc_stat *gc)
+{
+	uint8_t stale = 0;
+	unsigned int keys = 0, good_keys = 0;
+	struct bkey *k;
+	struct btree_iter iter;
+	struct bset_tree *t;
+
+	gc->nodes++;
+
+	for_each_key_filter(&b->keys, k, &iter, bch_ptr_invalid) {
+		stale = max(stale, btree_mark_key(b, k));
+		keys++;
+
+		if (bch_ptr_bad(&b->keys, k))
+			continue;
+
+		gc->key_bytes += bkey_u64s(k);
+		gc->nkeys++;
+		good_keys++;
+
+		gc->data += KEY_SIZE(k);
+	}
+
+	for (t = b->keys.set; t <= &b->keys.set[b->keys.nsets]; t++)
+		btree_bug_on(t->size &&
+			     bset_written(&b->keys, t) &&
+			     bkey_cmp(&b->key, &t->end) < 0,
+			     b, "found short btree key in gc");
+
+	if (b->c->gc_always_rewrite)
+		return true;
+
+	if (stale > 10)
+		return true;
+
+	if ((keys - good_keys) * 2 > keys)
+		return true;
+
+	return false;
+}
+
+#define GC_MERGE_NODES	4U
+
+struct gc_merge_info {
+	struct btree	*b;
+	unsigned int	keys;
+};
+
+static int bch_btree_insert_node(struct btree *b, struct btree_op *op,
+				 struct keylist *insert_keys,
+				 atomic_t *journal_ref,
+				 struct bkey *replace_key);
+
+static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
+			     struct gc_stat *gc, struct gc_merge_info *r)
+{
+	unsigned int i, nodes = 0, keys = 0, blocks;
+	struct btree *new_nodes[GC_MERGE_NODES];
+	struct keylist keylist;
+	struct closure cl;
+	struct bkey *k;
+
+	bch_keylist_init(&keylist);
+
+	if (btree_check_reserve(b, NULL))
+		return 0;
+
+	memset(new_nodes, 0, sizeof(new_nodes));
+	closure_init_stack(&cl);
+
+	while (nodes < GC_MERGE_NODES && !IS_ERR_OR_NULL(r[nodes].b))
+		keys += r[nodes++].keys;
+
+	blocks = btree_default_blocks(b->c) * 2 / 3;
+
+	if (nodes < 2 ||
+	    __set_blocks(b->keys.set[0].data, keys,
+			 block_bytes(b->c->cache)) > blocks * (nodes - 1))
+		return 0;
+
+	for (i = 0; i < nodes; i++) {
+		new_nodes[i] = btree_node_alloc_replacement(r[i].b, NULL);
+		if (IS_ERR(new_nodes[i]))
+			goto out_nocoalesce;
+	}
+
+	/*
+	 * We have to check the reserve here, after we've allocated our new
+	 * nodes, to make sure the insert below will succeed - we also check
+	 * before as an optimization to potentially avoid a bunch of expensive
+	 * allocs/sorts
+	 */
+	if (btree_check_reserve(b, NULL))
+		goto out_nocoalesce;
+
+	for (i = 0; i < nodes; i++)
+		mutex_lock(&new_nodes[i]->write_lock);
+
+	for (i = nodes - 1; i > 0; --i) {
+		struct bset *n1 = btree_bset_first(new_nodes[i]);
+		struct bset *n2 = btree_bset_first(new_nodes[i - 1]);
+		struct bkey *k, *last = NULL;
+
+		keys = 0;
+
+		if (i > 1) {
+			for (k = n2->start;
+			     k < bset_bkey_last(n2);
+			     k = bkey_next(k)) {
+				if (__set_blocks(n1, n1->keys + keys +
+						 bkey_u64s(k),
+						 block_bytes(b->c->cache)) > blocks)
+					break;
+
+				last = k;
+				keys += bkey_u64s(k);
+			}
+		} else {
+			/*
+			 * Last node we're not getting rid of - we're getting
+			 * rid of the node at r[0]. Have to try and fit all of
+			 * the remaining keys into this node; we can't ensure
+			 * they will always fit due to rounding and variable
+			 * length keys (shouldn't be possible in practice,
+			 * though)
+			 */
+			if (__set_blocks(n1, n1->keys + n2->keys,
+					 block_bytes(b->c->cache)) >
+			    btree_blocks(new_nodes[i]))
+				goto out_unlock_nocoalesce;
+
+			keys = n2->keys;
+			/* Take the key of the node we're getting rid of */
+			last = &r->b->key;
+		}
+
+		BUG_ON(__set_blocks(n1, n1->keys + keys, block_bytes(b->c->cache)) >
+		       btree_blocks(new_nodes[i]));
+
+		if (last)
+			bkey_copy_key(&new_nodes[i]->key, last);
+
+		memcpy(bset_bkey_last(n1),
+		       n2->start,
+		       (void *) bset_bkey_idx(n2, keys) - (void *) n2->start);
+
+		n1->keys += keys;
+		r[i].keys = n1->keys;
+
+		memmove(n2->start,
+			bset_bkey_idx(n2, keys),
+			(void *) bset_bkey_last(n2) -
+			(void *) bset_bkey_idx(n2, keys));
+
+		n2->keys -= keys;
+
+		if (__bch_keylist_realloc(&keylist,
+					  bkey_u64s(&new_nodes[i]->key)))
+			goto out_unlock_nocoalesce;
+
+		bch_btree_node_write(new_nodes[i], &cl);
+		bch_keylist_add(&keylist, &new_nodes[i]->key);
+	}
+
+	for (i = 0; i < nodes; i++)
+		mutex_unlock(&new_nodes[i]->write_lock);
+
+	closure_sync(&cl);
+
+	/* We emptied out this node */
+	BUG_ON(btree_bset_first(new_nodes[0])->keys);
+	btree_node_free(new_nodes[0]);
+	rw_unlock(true, new_nodes[0]);
+	new_nodes[0] = NULL;
+
+	for (i = 0; i < nodes; i++) {
+		if (__bch_keylist_realloc(&keylist, bkey_u64s(&r[i].b->key)))
+			goto out_nocoalesce;
+
+		make_btree_freeing_key(r[i].b, keylist.top);
+		bch_keylist_push(&keylist);
+	}
+
+	bch_btree_insert_node(b, op, &keylist, NULL, NULL);
+	BUG_ON(!bch_keylist_empty(&keylist));
+
+	for (i = 0; i < nodes; i++) {
+		btree_node_free(r[i].b);
+		rw_unlock(true, r[i].b);
+
+		r[i].b = new_nodes[i];
+	}
+
+	memmove(r, r + 1, sizeof(r[0]) * (nodes - 1));
+	r[nodes - 1].b = ERR_PTR(-EINTR);
+
+	trace_bcache_btree_gc_coalesce(nodes);
+	gc->nodes--;
+
+	bch_keylist_free(&keylist);
+
+	/* Invalidated our iterator */
+	return -EINTR;
+
+out_unlock_nocoalesce:
+	for (i = 0; i < nodes; i++)
+		mutex_unlock(&new_nodes[i]->write_lock);
+
+out_nocoalesce:
+	closure_sync(&cl);
+
+	while ((k = bch_keylist_pop(&keylist)))
+		if (!bkey_cmp(k, &ZERO_KEY))
+			atomic_dec(&b->c->prio_blocked);
+	bch_keylist_free(&keylist);
+
+	for (i = 0; i < nodes; i++)
+		if (!IS_ERR_OR_NULL(new_nodes[i])) {
+			btree_node_free(new_nodes[i]);
+			rw_unlock(true, new_nodes[i]);
+		}
+	return 0;
+}
+
+static int btree_gc_rewrite_node(struct btree *b, struct btree_op *op,
+				 struct btree *replace)
+{
+	struct keylist keys;
+	struct btree *n;
+
+	if (btree_check_reserve(b, NULL))
+		return 0;
+
+	n = btree_node_alloc_replacement(replace, NULL);
+	if (IS_ERR(n))
+		return 0;
+
+	/* recheck reserve after allocating replacement node */
+	if (btree_check_reserve(b, NULL)) {
+		btree_node_free(n);
+		rw_unlock(true, n);
+		return 0;
+	}
+
+	bch_btree_node_write_sync(n);
+
+	bch_keylist_init(&keys);
+	bch_keylist_add(&keys, &n->key);
+
+	make_btree_freeing_key(replace, keys.top);
+	bch_keylist_push(&keys);
+
+	bch_btree_insert_node(b, op, &keys, NULL, NULL);
+	BUG_ON(!bch_keylist_empty(&keys));
+
+	btree_node_free(replace);
+	rw_unlock(true, n);
+
+	/* Invalidated our iterator */
+	return -EINTR;
+}
+
+static unsigned int btree_gc_count_keys(struct btree *b)
+{
+	struct bkey *k;
+	struct btree_iter iter;
+	unsigned int ret = 0;
+
+	for_each_key_filter(&b->keys, k, &iter, bch_ptr_bad)
+		ret += bkey_u64s(k);
+
+	return ret;
+}
+
+static size_t btree_gc_min_nodes(struct cache_set *c)
+{
+	size_t min_nodes;
+
+	/*
+	 * Since incremental GC would stop 100ms when front
+	 * side I/O comes, so when there are many btree nodes,
+	 * if GC only processes constant (100) nodes each time,
+	 * GC would last a long time, and the front side I/Os
+	 * would run out of the buckets (since no new bucket
+	 * can be allocated during GC), and be blocked again.
+	 * So GC should not process constant nodes, but varied
+	 * nodes according to the number of btree nodes, which
+	 * realized by dividing GC into constant(100) times,
+	 * so when there are many btree nodes, GC can process
+	 * more nodes each time, otherwise, GC will process less
+	 * nodes each time (but no less than MIN_GC_NODES)
+	 */
+	min_nodes = c->gc_stats.nodes / MAX_GC_TIMES;
+	if (min_nodes < MIN_GC_NODES)
+		min_nodes = MIN_GC_NODES;
+
+	return min_nodes;
+}
+
+
+static int btree_gc_recurse(struct btree *b, struct btree_op *op,
+			    struct closure *writes, struct gc_stat *gc)
+{
+	int ret = 0;
+	bool should_rewrite;
+	struct bkey *k;
+	struct btree_iter iter;
+	struct gc_merge_info r[GC_MERGE_NODES];
+	struct gc_merge_info *i, *last = r + ARRAY_SIZE(r) - 1;
+
+	bch_btree_iter_init(&b->keys, &iter, &b->c->gc_done);
+
+	for (i = r; i < r + ARRAY_SIZE(r); i++)
+		i->b = ERR_PTR(-EINTR);
+
+	while (1) {
+		k = bch_btree_iter_next_filter(&iter, &b->keys, bch_ptr_bad);
+		if (k) {
+			r->b = bch_btree_node_get(b->c, op, k, b->level - 1,
+						  true, b);
+			if (IS_ERR(r->b)) {
+				ret = PTR_ERR(r->b);
+				break;
+			}
+
+			r->keys = btree_gc_count_keys(r->b);
+
+			ret = btree_gc_coalesce(b, op, gc, r);
+			if (ret)
+				break;
+		}
+
+		if (!last->b)
+			break;
+
+		if (!IS_ERR(last->b)) {
+			should_rewrite = btree_gc_mark_node(last->b, gc);
+			if (should_rewrite) {
+				ret = btree_gc_rewrite_node(b, op, last->b);
+				if (ret)
+					break;
+			}
+
+			if (last->b->level) {
+				ret = btree_gc_recurse(last->b, op, writes, gc);
+				if (ret)
+					break;
+			}
+
+			bkey_copy_key(&b->c->gc_done, &last->b->key);
+
+			/*
+			 * Must flush leaf nodes before gc ends, since replace
+			 * operations aren't journalled
+			 */
+			mutex_lock(&last->b->write_lock);
+			if (btree_node_dirty(last->b))
+				bch_btree_node_write(last->b, writes);
+			mutex_unlock(&last->b->write_lock);
+			rw_unlock(true, last->b);
+		}
+
+		memmove(r + 1, r, sizeof(r[0]) * (GC_MERGE_NODES - 1));
+		r->b = NULL;
+
+		if (atomic_read(&b->c->search_inflight) &&
+		    gc->nodes >= gc->nodes_pre + btree_gc_min_nodes(b->c)) {
+			gc->nodes_pre =  gc->nodes;
+			ret = -EAGAIN;
+			break;
+		}
+
+		if (need_resched()) {
+			ret = -EAGAIN;
+			break;
+		}
+	}
+
+	for (i = r; i < r + ARRAY_SIZE(r); i++)
+		if (!IS_ERR_OR_NULL(i->b)) {
+			mutex_lock(&i->b->write_lock);
+			if (btree_node_dirty(i->b))
+				bch_btree_node_write(i->b, writes);
+			mutex_unlock(&i->b->write_lock);
+			rw_unlock(true, i->b);
+		}
+
+	return ret;
+}
+
+static int bch_btree_gc_root(struct btree *b, struct btree_op *op,
+			     struct closure *writes, struct gc_stat *gc)
+{
+	struct btree *n = NULL;
+	int ret = 0;
+	bool should_rewrite;
+
+	should_rewrite = btree_gc_mark_node(b, gc);
+	if (should_rewrite) {
+		n = btree_node_alloc_replacement(b, NULL);
+
+		if (!IS_ERR(n)) {
+			bch_btree_node_write_sync(n);
+
+			bch_btree_set_root(n);
+			btree_node_free(b);
+			rw_unlock(true, n);
+
+			return -EINTR;
+		}
+	}
+
+	__bch_btree_mark_key(b->c, b->level + 1, &b->key);
+
+	if (b->level) {
+		ret = btree_gc_recurse(b, op, writes, gc);
+		if (ret)
+			return ret;
+	}
+
+	bkey_copy_key(&b->c->gc_done, &b->key);
+
+	return ret;
+}
+
+static void btree_gc_start(struct cache_set *c)
+{
+	struct cache *ca;
+	struct bucket *b;
+
+	if (!c->gc_mark_valid)
+		return;
+
+	mutex_lock(&c->bucket_lock);
+
+	c->gc_mark_valid = 0;
+	c->gc_done = ZERO_KEY;
+
+	ca = c->cache;
+	for_each_bucket(b, ca) {
+		b->last_gc = b->gen;
+		if (!atomic_read(&b->pin)) {
+			SET_GC_MARK(b, 0);
+			SET_GC_SECTORS_USED(b, 0);
+		}
+	}
+
+	mutex_unlock(&c->bucket_lock);
+}
+
+static void bch_btree_gc_finish(struct cache_set *c)
+{
+	struct bucket *b;
+	struct cache *ca;
+	unsigned int i, j;
+	uint64_t *k;
+
+	mutex_lock(&c->bucket_lock);
+
+	set_gc_sectors(c);
+	c->gc_mark_valid = 1;
+	c->need_gc	= 0;
+
+	for (i = 0; i < KEY_PTRS(&c->uuid_bucket); i++)
+		SET_GC_MARK(PTR_BUCKET(c, &c->uuid_bucket, i),
+			    GC_MARK_METADATA);
+
+	/* don't reclaim buckets to which writeback keys point */
+	rcu_read_lock();
+	for (i = 0; i < c->devices_max_used; i++) {
+		struct bcache_device *d = c->devices[i];
+		struct cached_dev *dc;
+		struct keybuf_key *w, *n;
+
+		if (!d || UUID_FLASH_ONLY(&c->uuids[i]))
+			continue;
+		dc = container_of(d, struct cached_dev, disk);
+
+		spin_lock(&dc->writeback_keys.lock);
+		rbtree_postorder_for_each_entry_safe(w, n,
+					&dc->writeback_keys.keys, node)
+			for (j = 0; j < KEY_PTRS(&w->key); j++)
+				SET_GC_MARK(PTR_BUCKET(c, &w->key, j),
+					    GC_MARK_DIRTY);
+		spin_unlock(&dc->writeback_keys.lock);
+	}
+	rcu_read_unlock();
+
+	c->avail_nbuckets = 0;
+
+	ca = c->cache;
+	ca->invalidate_needs_gc = 0;
+
+	for (k = ca->sb.d; k < ca->sb.d + ca->sb.keys; k++)
+		SET_GC_MARK(ca->buckets + *k, GC_MARK_METADATA);
+
+	for (k = ca->prio_buckets;
+	     k < ca->prio_buckets + prio_buckets(ca) * 2; k++)
+		SET_GC_MARK(ca->buckets + *k, GC_MARK_METADATA);
+
+	for_each_bucket(b, ca) {
+		c->need_gc	= max(c->need_gc, bucket_gc_gen(b));
+
+		if (atomic_read(&b->pin))
+			continue;
+
+		BUG_ON(!GC_MARK(b) && GC_SECTORS_USED(b));
+
+		if (!GC_MARK(b) || GC_MARK(b) == GC_MARK_RECLAIMABLE)
+			c->avail_nbuckets++;
+	}
+
+	mutex_unlock(&c->bucket_lock);
+}
+
+static void bch_btree_gc(struct cache_set *c)
+{
+	int ret;
+	struct gc_stat stats;
+	struct closure writes;
+	struct btree_op op;
+	uint64_t start_time = local_clock();
+
+	trace_bcache_gc_start(c);
+
+	memset(&stats, 0, sizeof(struct gc_stat));
+	closure_init_stack(&writes);
+	bch_btree_op_init(&op, SHRT_MAX);
+
+	btree_gc_start(c);
+
+	/* if CACHE_SET_IO_DISABLE set, gc thread should stop too */
+	do {
+		ret = bcache_btree_root(gc_root, c, &op, &writes, &stats);
+		closure_sync(&writes);
+		cond_resched();
+
+		if (ret == -EAGAIN)
+			schedule_timeout_interruptible(msecs_to_jiffies
+						       (GC_SLEEP_MS));
+		else if (ret)
+			pr_warn("gc failed!\n");
+	} while (ret && !test_bit(CACHE_SET_IO_DISABLE, &c->flags));
+
+	bch_btree_gc_finish(c);
+	wake_up_allocators(c);
+
+	bch_time_stats_update(&c->btree_gc_time, start_time);
+
+	stats.key_bytes *= sizeof(uint64_t);
+	stats.data	<<= 9;
+	bch_update_bucket_in_use(c, &stats);
+	memcpy(&c->gc_stats, &stats, sizeof(struct gc_stat));
+
+	trace_bcache_gc_end(c);
+
+	bch_moving_gc(c);
+}
+
+static bool gc_should_run(struct cache_set *c)
+{
+	struct cache *ca = c->cache;
+
+	if (ca->invalidate_needs_gc)
+		return true;
+
+	if (atomic_read(&c->sectors_to_gc) < 0)
+		return true;
+
+	return false;
+}
+
+static int bch_gc_thread(void *arg)
+{
+	struct cache_set *c = arg;
+
+	while (1) {
+		wait_event_interruptible(c->gc_wait,
+			   kthread_should_stop() ||
+			   test_bit(CACHE_SET_IO_DISABLE, &c->flags) ||
+			   gc_should_run(c));
+
+		if (kthread_should_stop() ||
+		    test_bit(CACHE_SET_IO_DISABLE, &c->flags))
+			break;
+
+		set_gc_sectors(c);
+		bch_btree_gc(c);
+	}
+
+	wait_for_kthread_stop();
+	return 0;
+}
+
+int bch_gc_thread_start(struct cache_set *c)
+{
+	c->gc_thread = kthread_run(bch_gc_thread, c, "bcache_gc");
+	return PTR_ERR_OR_ZERO(c->gc_thread);
+}
+
+/* Initial partial gc */
+
+static int bch_btree_check_recurse(struct btree *b, struct btree_op *op)
+{
+	int ret = 0;
+	struct bkey *k, *p = NULL;
+	struct btree_iter iter;
+
+	for_each_key_filter(&b->keys, k, &iter, bch_ptr_invalid)
+		bch_initial_mark_key(b->c, b->level, k);
+
+	bch_initial_mark_key(b->c, b->level + 1, &b->key);
+
+	if (b->level) {
+		bch_btree_iter_init(&b->keys, &iter, NULL);
+
+		do {
+			k = bch_btree_iter_next_filter(&iter, &b->keys,
+						       bch_ptr_bad);
+			if (k) {
+				btree_node_prefetch(b, k);
+				/*
+				 * initiallize c->gc_stats.nodes
+				 * for incremental GC
+				 */
+				b->c->gc_stats.nodes++;
+			}
+
+			if (p)
+				ret = bcache_btree(check_recurse, p, b, op);
+
+			p = k;
+		} while (p && !ret);
+	}
+
+	return ret;
+}
+
+
+static int bch_btree_check_thread(void *arg)
+{
+	int ret;
+	struct btree_check_info *info = arg;
+	struct btree_check_state *check_state = info->state;
+	struct cache_set *c = check_state->c;
+	struct btree_iter iter;
+	struct bkey *k, *p;
+	int cur_idx, prev_idx, skip_nr;
+
+	k = p = NULL;
+	cur_idx = prev_idx = 0;
+	ret = 0;
+
+	/* root node keys are checked before thread created */
+	bch_btree_iter_init(&c->root->keys, &iter, NULL);
+	k = bch_btree_iter_next_filter(&iter, &c->root->keys, bch_ptr_bad);
+	BUG_ON(!k);
+
+	p = k;
+	while (k) {
+		/*
+		 * Fetch a root node key index, skip the keys which
+		 * should be fetched by other threads, then check the
+		 * sub-tree indexed by the fetched key.
+		 */
+		spin_lock(&check_state->idx_lock);
+		cur_idx = check_state->key_idx;
+		check_state->key_idx++;
+		spin_unlock(&check_state->idx_lock);
+
+		skip_nr = cur_idx - prev_idx;
+
+		while (skip_nr) {
+			k = bch_btree_iter_next_filter(&iter,
+						       &c->root->keys,
+						       bch_ptr_bad);
+			if (k)
+				p = k;
+			else {
+				/*
+				 * No more keys to check in root node,
+				 * current checking threads are enough,
+				 * stop creating more.
+				 */
+				atomic_set(&check_state->enough, 1);
+				/* Update check_state->enough earlier */
+				smp_mb__after_atomic();
+				goto out;
+			}
+			skip_nr--;
+			cond_resched();
+		}
+
+		if (p) {
+			struct btree_op op;
+
+			btree_node_prefetch(c->root, p);
+			c->gc_stats.nodes++;
+			bch_btree_op_init(&op, 0);
+			ret = bcache_btree(check_recurse, p, c->root, &op);
+			/*
+			 * The op may be added to cache_set's btree_cache_wait
+			 * in mca_cannibalize(), must ensure it is removed from
+			 * the list and release btree_cache_alloc_lock before
+			 * free op memory.
+			 * Otherwise, the btree_cache_wait will be damaged.
+			 */
+			bch_cannibalize_unlock(c);
+			finish_wait(&c->btree_cache_wait, &(&op)->wait);
+			if (ret)
+				goto out;
+		}
+		p = NULL;
+		prev_idx = cur_idx;
+		cond_resched();
+	}
+
+out:
+	info->result = ret;
+	/* update check_state->started among all CPUs */
+	smp_mb__before_atomic();
+	if (atomic_dec_and_test(&check_state->started))
+		wake_up(&check_state->wait);
+
+	return ret;
+}
+
+
+
+static int bch_btree_chkthread_nr(void)
+{
+	int n = num_online_cpus()/2;
+
+	if (n == 0)
+		n = 1;
+	else if (n > BCH_BTR_CHKTHREAD_MAX)
+		n = BCH_BTR_CHKTHREAD_MAX;
+
+	return n;
+}
+
+int bch_btree_check(struct cache_set *c)
+{
+	int ret = 0;
+	int i;
+	struct bkey *k = NULL;
+	struct btree_iter iter;
+	struct btree_check_state check_state;
+
+	/* check and mark root node keys */
+	for_each_key_filter(&c->root->keys, k, &iter, bch_ptr_invalid)
+		bch_initial_mark_key(c, c->root->level, k);
+
+	bch_initial_mark_key(c, c->root->level + 1, &c->root->key);
+
+	if (c->root->level == 0)
+		return 0;
+
+	memset(&check_state, 0, sizeof(struct btree_check_state));
+	check_state.c = c;
+	check_state.total_threads = bch_btree_chkthread_nr();
+	check_state.key_idx = 0;
+	spin_lock_init(&check_state.idx_lock);
+	atomic_set(&check_state.started, 0);
+	atomic_set(&check_state.enough, 0);
+	init_waitqueue_head(&check_state.wait);
+
+	rw_lock(0, c->root, c->root->level);
+	/*
+	 * Run multiple threads to check btree nodes in parallel,
+	 * if check_state.enough is non-zero, it means current
+	 * running check threads are enough, unncessary to create
+	 * more.
+	 */
+	for (i = 0; i < check_state.total_threads; i++) {
+		/* fetch latest check_state.enough earlier */
+		smp_mb__before_atomic();
+		if (atomic_read(&check_state.enough))
+			break;
+
+		check_state.infos[i].result = 0;
+		check_state.infos[i].state = &check_state;
+
+		check_state.infos[i].thread =
+			kthread_run(bch_btree_check_thread,
+				    &check_state.infos[i],
+				    "bch_btrchk[%d]", i);
+		if (IS_ERR(check_state.infos[i].thread)) {
+			pr_err("fails to run thread bch_btrchk[%d]\n", i);
+			for (--i; i >= 0; i--)
+				kthread_stop(check_state.infos[i].thread);
+			ret = -ENOMEM;
+			goto out;
+		}
+		atomic_inc(&check_state.started);
+	}
+
+	/*
+	 * Must wait for all threads to stop.
+	 */
+	wait_event(check_state.wait, atomic_read(&check_state.started) == 0);
+
+	for (i = 0; i < check_state.total_threads; i++) {
+		if (check_state.infos[i].result) {
+			ret = check_state.infos[i].result;
+			goto out;
+		}
+	}
+
+out:
+	rw_unlock(0, c->root);
+	return ret;
+}
+
+void bch_initial_gc_finish(struct cache_set *c)
+{
+	struct cache *ca = c->cache;
+	struct bucket *b;
+
+	bch_btree_gc_finish(c);
+
+	mutex_lock(&c->bucket_lock);
+
+	/*
+	 * We need to put some unused buckets directly on the prio freelist in
+	 * order to get the allocator thread started - it needs freed buckets in
+	 * order to rewrite the prios and gens, and it needs to rewrite prios
+	 * and gens in order to free buckets.
+	 *
+	 * This is only safe for buckets that have no live data in them, which
+	 * there should always be some of.
+	 */
+	for_each_bucket(b, ca) {
+		if (fifo_full(&ca->free[RESERVE_PRIO]) &&
+		    fifo_full(&ca->free[RESERVE_BTREE]))
+			break;
+
+		if (bch_can_invalidate_bucket(ca, b) &&
+		    !GC_MARK(b)) {
+			__bch_invalidate_one_bucket(ca, b);
+			if (!fifo_push(&ca->free[RESERVE_PRIO],
+			   b - ca->buckets))
+				fifo_push(&ca->free[RESERVE_BTREE],
+					  b - ca->buckets);
+		}
+	}
+
+	mutex_unlock(&c->bucket_lock);
+}
+
+/* Btree insertion */
+
+static bool btree_insert_key(struct btree *b, struct bkey *k,
+			     struct bkey *replace_key)
+{
+	unsigned int status;
+
+	BUG_ON(bkey_cmp(k, &b->key) > 0);
+
+	status = bch_btree_insert_key(&b->keys, k, replace_key);
+	if (status != BTREE_INSERT_STATUS_NO_INSERT) {
+		bch_check_keys(&b->keys, "%u for %s", status,
+			       replace_key ? "replace" : "insert");
+
+		trace_bcache_btree_insert_key(b, k, replace_key != NULL,
+					      status);
+		return true;
+	} else
+		return false;
+}
+
+static size_t insert_u64s_remaining(struct btree *b)
+{
+	long ret = bch_btree_keys_u64s_remaining(&b->keys);
+
+	/*
+	 * Might land in the middle of an existing extent and have to split it
+	 */
+	if (b->keys.ops->is_extents)
+		ret -= KEY_MAX_U64S;
+
+	return max(ret, 0L);
+}
+
+static bool bch_btree_insert_keys(struct btree *b, struct btree_op *op,
+				  struct keylist *insert_keys,
+				  struct bkey *replace_key)
+{
+	bool ret = false;
+	int oldsize = bch_count_data(&b->keys);
+
+	while (!bch_keylist_empty(insert_keys)) {
+		struct bkey *k = insert_keys->keys;
+
+		if (bkey_u64s(k) > insert_u64s_remaining(b))
+			break;
+
+		if (bkey_cmp(k, &b->key) <= 0) {
+			if (!b->level)
+				bkey_put(b->c, k);
+
+			ret |= btree_insert_key(b, k, replace_key);
+			bch_keylist_pop_front(insert_keys);
+		} else if (bkey_cmp(&START_KEY(k), &b->key) < 0) {
+			BKEY_PADDED(key) temp;
+			bkey_copy(&temp.key, insert_keys->keys);
+
+			bch_cut_back(&b->key, &temp.key);
+			bch_cut_front(&b->key, insert_keys->keys);
+
+			ret |= btree_insert_key(b, &temp.key, replace_key);
+			break;
+		} else {
+			break;
+		}
+	}
+
+	if (!ret)
+		op->insert_collision = true;
+
+	BUG_ON(!bch_keylist_empty(insert_keys) && b->level);
+
+	BUG_ON(bch_count_data(&b->keys) < oldsize);
+	return ret;
+}
+
+static int btree_split(struct btree *b, struct btree_op *op,
+		       struct keylist *insert_keys,
+		       struct bkey *replace_key)
+{
+	bool split;
+	struct btree *n1, *n2 = NULL, *n3 = NULL;
+	uint64_t start_time = local_clock();
+	struct closure cl;
+	struct keylist parent_keys;
+
+	closure_init_stack(&cl);
+	bch_keylist_init(&parent_keys);
+
+	if (btree_check_reserve(b, op)) {
+		if (!b->level)
+			return -EINTR;
+		else
+			WARN(1, "insufficient reserve for split\n");
+	}
+
+	n1 = btree_node_alloc_replacement(b, op);
+	if (IS_ERR(n1))
+		goto err;
+
+	split = set_blocks(btree_bset_first(n1),
+			   block_bytes(n1->c->cache)) > (btree_blocks(b) * 4) / 5;
+
+	if (split) {
+		unsigned int keys = 0;
+
+		trace_bcache_btree_node_split(b, btree_bset_first(n1)->keys);
+
+		n2 = bch_btree_node_alloc(b->c, op, b->level, b->parent);
+		if (IS_ERR(n2))
+			goto err_free1;
+
+		if (!b->parent) {
+			n3 = bch_btree_node_alloc(b->c, op, b->level + 1, NULL);
+			if (IS_ERR(n3))
+				goto err_free2;
+		}
+
+		mutex_lock(&n1->write_lock);
+		mutex_lock(&n2->write_lock);
+
+		bch_btree_insert_keys(n1, op, insert_keys, replace_key);
+
+		/*
+		 * Has to be a linear search because we don't have an auxiliary
+		 * search tree yet
+		 */
+
+		while (keys < (btree_bset_first(n1)->keys * 3) / 5)
+			keys += bkey_u64s(bset_bkey_idx(btree_bset_first(n1),
+							keys));
+
+		bkey_copy_key(&n1->key,
+			      bset_bkey_idx(btree_bset_first(n1), keys));
+		keys += bkey_u64s(bset_bkey_idx(btree_bset_first(n1), keys));
+
+		btree_bset_first(n2)->keys = btree_bset_first(n1)->keys - keys;
+		btree_bset_first(n1)->keys = keys;
+
+		memcpy(btree_bset_first(n2)->start,
+		       bset_bkey_last(btree_bset_first(n1)),
+		       btree_bset_first(n2)->keys * sizeof(uint64_t));
+
+		bkey_copy_key(&n2->key, &b->key);
+
+		bch_keylist_add(&parent_keys, &n2->key);
+		bch_btree_node_write(n2, &cl);
+		mutex_unlock(&n2->write_lock);
+		rw_unlock(true, n2);
+	} else {
+		trace_bcache_btree_node_compact(b, btree_bset_first(n1)->keys);
+
+		mutex_lock(&n1->write_lock);
+		bch_btree_insert_keys(n1, op, insert_keys, replace_key);
+	}
+
+	bch_keylist_add(&parent_keys, &n1->key);
+	bch_btree_node_write(n1, &cl);
+	mutex_unlock(&n1->write_lock);
+
+	if (n3) {
+		/* Depth increases, make a new root */
+		mutex_lock(&n3->write_lock);
+		bkey_copy_key(&n3->key, &MAX_KEY);
+		bch_btree_insert_keys(n3, op, &parent_keys, NULL);
+		bch_btree_node_write(n3, &cl);
+		mutex_unlock(&n3->write_lock);
+
+		closure_sync(&cl);
+		bch_btree_set_root(n3);
+		rw_unlock(true, n3);
+	} else if (!b->parent) {
+		/* Root filled up but didn't need to be split */
+		closure_sync(&cl);
+		bch_btree_set_root(n1);
+	} else {
+		/* Split a non root node */
+		closure_sync(&cl);
+		make_btree_freeing_key(b, parent_keys.top);
+		bch_keylist_push(&parent_keys);
+
+		bch_btree_insert_node(b->parent, op, &parent_keys, NULL, NULL);
+		BUG_ON(!bch_keylist_empty(&parent_keys));
+	}
+
+	btree_node_free(b);
+	rw_unlock(true, n1);
+
+	bch_time_stats_update(&b->c->btree_split_time, start_time);
+
+	return 0;
+err_free2:
+	bkey_put(b->c, &n2->key);
+	btree_node_free(n2);
+	rw_unlock(true, n2);
+err_free1:
+	bkey_put(b->c, &n1->key);
+	btree_node_free(n1);
+	rw_unlock(true, n1);
+err:
+	WARN(1, "bcache: btree split failed (level %u)", b->level);
+
+	if (n3 == ERR_PTR(-EAGAIN) ||
+	    n2 == ERR_PTR(-EAGAIN) ||
+	    n1 == ERR_PTR(-EAGAIN))
+		return -EAGAIN;
+
+	return -ENOMEM;
+}
+
+static int bch_btree_insert_node(struct btree *b, struct btree_op *op,
+				 struct keylist *insert_keys,
+				 atomic_t *journal_ref,
+				 struct bkey *replace_key)
+{
+	struct closure cl;
+
+	BUG_ON(b->level && replace_key);
+
+	closure_init_stack(&cl);
+
+	mutex_lock(&b->write_lock);
+
+	if (write_block(b) != btree_bset_last(b) &&
+	    b->keys.last_set_unwritten)
+		bch_btree_init_next(b); /* just wrote a set */
+
+	if (bch_keylist_nkeys(insert_keys) > insert_u64s_remaining(b)) {
+		mutex_unlock(&b->write_lock);
+		goto split;
+	}
+
+	BUG_ON(write_block(b) != btree_bset_last(b));
+
+	if (bch_btree_insert_keys(b, op, insert_keys, replace_key)) {
+		if (!b->level)
+			bch_btree_leaf_dirty(b, journal_ref);
+		else
+			bch_btree_node_write(b, &cl);
+	}
+
+	mutex_unlock(&b->write_lock);
+
+	/* wait for btree node write if necessary, after unlock */
+	closure_sync(&cl);
+
+	return 0;
+split:
+	if (current->bio_list) {
+		op->lock = b->c->root->level + 1;
+		return -EAGAIN;
+	} else if (op->lock <= b->c->root->level) {
+		op->lock = b->c->root->level + 1;
+		return -EINTR;
+	} else {
+		/* Invalidated all iterators */
+		int ret = btree_split(b, op, insert_keys, replace_key);
+
+		if (bch_keylist_empty(insert_keys))
+			return 0;
+		else if (!ret)
+			return -EINTR;
+		return ret;
+	}
+}
+
+int bch_btree_insert_check_key(struct btree *b, struct btree_op *op,
+			       struct bkey *check_key)
+{
+	int ret = -EINTR;
+	uint64_t btree_ptr = b->key.ptr[0];
+	unsigned long seq = b->seq;
+	struct keylist insert;
+	bool upgrade = op->lock == -1;
+
+	bch_keylist_init(&insert);
+
+	if (upgrade) {
+		rw_unlock(false, b);
+		rw_lock(true, b, b->level);
+
+		if (b->key.ptr[0] != btree_ptr ||
+		    b->seq != seq + 1) {
+			op->lock = b->level;
+			goto out;
+		}
+	}
+
+	SET_KEY_PTRS(check_key, 1);
+	get_random_bytes(&check_key->ptr[0], sizeof(uint64_t));
+
+	SET_PTR_DEV(check_key, 0, PTR_CHECK_DEV);
+
+	bch_keylist_add(&insert, check_key);
+
+	ret = bch_btree_insert_node(b, op, &insert, NULL, NULL);
+
+	BUG_ON(!ret && !bch_keylist_empty(&insert));
+out:
+	if (upgrade)
+		downgrade_write(&b->lock);
+	return ret;
+}
+
+struct btree_insert_op {
+	struct btree_op	op;
+	struct keylist	*keys;
+	atomic_t	*journal_ref;
+	struct bkey	*replace_key;
+};
+
+static int btree_insert_fn(struct btree_op *b_op, struct btree *b)
+{
+	struct btree_insert_op *op = container_of(b_op,
+					struct btree_insert_op, op);
+
+	int ret = bch_btree_insert_node(b, &op->op, op->keys,
+					op->journal_ref, op->replace_key);
+	if (ret && !bch_keylist_empty(op->keys))
+		return ret;
+	else
+		return MAP_DONE;
+}
+
+int bch_btree_insert(struct cache_set *c, struct keylist *keys,
+		     atomic_t *journal_ref, struct bkey *replace_key)
+{
+	struct btree_insert_op op;
+	int ret = 0;
+
+	BUG_ON(current->bio_list);
+	BUG_ON(bch_keylist_empty(keys));
+
+	bch_btree_op_init(&op.op, 0);
+	op.keys		= keys;
+	op.journal_ref	= journal_ref;
+	op.replace_key	= replace_key;
+
+	while (!ret && !bch_keylist_empty(keys)) {
+		op.op.lock = 0;
+		ret = bch_btree_map_leaf_nodes(&op.op, c,
+					       &START_KEY(keys->keys),
+					       btree_insert_fn);
+	}
+
+	if (ret) {
+		struct bkey *k;
+
+		pr_err("error %i\n", ret);
+
+		while ((k = bch_keylist_pop(keys)))
+			bkey_put(c, k);
+	} else if (op.op.insert_collision)
+		ret = -ESRCH;
+
+	return ret;
+}
+
+void bch_btree_set_root(struct btree *b)
+{
+	unsigned int i;
+	struct closure cl;
+
+	closure_init_stack(&cl);
+
+	trace_bcache_btree_set_root(b);
+
+	BUG_ON(!b->written);
+
+	for (i = 0; i < KEY_PTRS(&b->key); i++)
+		BUG_ON(PTR_BUCKET(b->c, &b->key, i)->prio != BTREE_PRIO);
+
+	mutex_lock(&b->c->bucket_lock);
+	list_del_init(&b->list);
+	mutex_unlock(&b->c->bucket_lock);
+
+	b->c->root = b;
+
+	bch_journal_meta(b->c, &cl);
+	closure_sync(&cl);
+}
+
+/* Map across nodes or keys */
+
+static int bch_btree_map_nodes_recurse(struct btree *b, struct btree_op *op,
+				       struct bkey *from,
+				       btree_map_nodes_fn *fn, int flags)
+{
+	int ret = MAP_CONTINUE;
+
+	if (b->level) {
+		struct bkey *k;
+		struct btree_iter iter;
+
+		bch_btree_iter_init(&b->keys, &iter, from);
+
+		while ((k = bch_btree_iter_next_filter(&iter, &b->keys,
+						       bch_ptr_bad))) {
+			ret = bcache_btree(map_nodes_recurse, k, b,
+				    op, from, fn, flags);
+			from = NULL;
+
+			if (ret != MAP_CONTINUE)
+				return ret;
+		}
+	}
+
+	if (!b->level || flags == MAP_ALL_NODES)
+		ret = fn(op, b);
+
+	return ret;
+}
+
+int __bch_btree_map_nodes(struct btree_op *op, struct cache_set *c,
+			  struct bkey *from, btree_map_nodes_fn *fn, int flags)
+{
+	return bcache_btree_root(map_nodes_recurse, c, op, from, fn, flags);
+}
+
+int bch_btree_map_keys_recurse(struct btree *b, struct btree_op *op,
+				      struct bkey *from, btree_map_keys_fn *fn,
+				      int flags)
+{
+	int ret = MAP_CONTINUE;
+	struct bkey *k;
+	struct btree_iter iter;
+
+	bch_btree_iter_init(&b->keys, &iter, from);
+
+	while ((k = bch_btree_iter_next_filter(&iter, &b->keys, bch_ptr_bad))) {
+		ret = !b->level
+			? fn(op, b, k)
+			: bcache_btree(map_keys_recurse, k,
+				       b, op, from, fn, flags);
+		from = NULL;
+
+		if (ret != MAP_CONTINUE)
+			return ret;
+	}
+
+	if (!b->level && (flags & MAP_END_KEY))
+		ret = fn(op, b, &KEY(KEY_INODE(&b->key),
+				     KEY_OFFSET(&b->key), 0));
+
+	return ret;
+}
+
+int bch_btree_map_keys(struct btree_op *op, struct cache_set *c,
+		       struct bkey *from, btree_map_keys_fn *fn, int flags)
+{
+	return bcache_btree_root(map_keys_recurse, c, op, from, fn, flags);
+}
+
+/* Keybuf code */
+
+static inline int keybuf_cmp(struct keybuf_key *l, struct keybuf_key *r)
+{
+	/* Overlapping keys compare equal */
+	if (bkey_cmp(&l->key, &START_KEY(&r->key)) <= 0)
+		return -1;
+	if (bkey_cmp(&START_KEY(&l->key), &r->key) >= 0)
+		return 1;
+	return 0;
+}
+
+static inline int keybuf_nonoverlapping_cmp(struct keybuf_key *l,
+					    struct keybuf_key *r)
+{
+	return clamp_t(int64_t, bkey_cmp(&l->key, &r->key), -1, 1);
+}
+
+struct refill {
+	struct btree_op	op;
+	unsigned int	nr_found;
+	struct keybuf	*buf;
+	struct bkey	*end;
+	keybuf_pred_fn	*pred;
+};
+
+static int refill_keybuf_fn(struct btree_op *op, struct btree *b,
+			    struct bkey *k)
+{
+	struct refill *refill = container_of(op, struct refill, op);
+	struct keybuf *buf = refill->buf;
+	int ret = MAP_CONTINUE;
+
+	if (bkey_cmp(k, refill->end) > 0) {
+		ret = MAP_DONE;
+		goto out;
+	}
+
+	if (!KEY_SIZE(k)) /* end key */
+		goto out;
+
+	if (refill->pred(buf, k)) {
+		struct keybuf_key *w;
+
+		spin_lock(&buf->lock);
+
+		w = array_alloc(&buf->freelist);
+		if (!w) {
+			spin_unlock(&buf->lock);
+			return MAP_DONE;
+		}
+
+		w->private = NULL;
+		bkey_copy(&w->key, k);
+
+		if (RB_INSERT(&buf->keys, w, node, keybuf_cmp))
+			array_free(&buf->freelist, w);
+		else
+			refill->nr_found++;
+
+		if (array_freelist_empty(&buf->freelist))
+			ret = MAP_DONE;
+
+		spin_unlock(&buf->lock);
+	}
+out:
+	buf->last_scanned = *k;
+	return ret;
+}
+
+void bch_refill_keybuf(struct cache_set *c, struct keybuf *buf,
+		       struct bkey *end, keybuf_pred_fn *pred)
+{
+	struct bkey start = buf->last_scanned;
+	struct refill refill;
+
+	cond_resched();
+
+	bch_btree_op_init(&refill.op, -1);
+	refill.nr_found	= 0;
+	refill.buf	= buf;
+	refill.end	= end;
+	refill.pred	= pred;
+
+	bch_btree_map_keys(&refill.op, c, &buf->last_scanned,
+			   refill_keybuf_fn, MAP_END_KEY);
+
+	trace_bcache_keyscan(refill.nr_found,
+			     KEY_INODE(&start), KEY_OFFSET(&start),
+			     KEY_INODE(&buf->last_scanned),
+			     KEY_OFFSET(&buf->last_scanned));
+
+	spin_lock(&buf->lock);
+
+	if (!RB_EMPTY_ROOT(&buf->keys)) {
+		struct keybuf_key *w;
+
+		w = RB_FIRST(&buf->keys, struct keybuf_key, node);
+		buf->start	= START_KEY(&w->key);
+
+		w = RB_LAST(&buf->keys, struct keybuf_key, node);
+		buf->end	= w->key;
+	} else {
+		buf->start	= MAX_KEY;
+		buf->end	= MAX_KEY;
+	}
+
+	spin_unlock(&buf->lock);
+}
+
+static void __bch_keybuf_del(struct keybuf *buf, struct keybuf_key *w)
+{
+	rb_erase(&w->node, &buf->keys);
+	array_free(&buf->freelist, w);
+}
+
+void bch_keybuf_del(struct keybuf *buf, struct keybuf_key *w)
+{
+	spin_lock(&buf->lock);
+	__bch_keybuf_del(buf, w);
+	spin_unlock(&buf->lock);
+}
+
+bool bch_keybuf_check_overlapping(struct keybuf *buf, struct bkey *start,
+				  struct bkey *end)
+{
+	bool ret = false;
+	struct keybuf_key *p, *w, s;
+
+	s.key = *start;
+
+	if (bkey_cmp(end, &buf->start) <= 0 ||
+	    bkey_cmp(start, &buf->end) >= 0)
+		return false;
+
+	spin_lock(&buf->lock);
+	w = RB_GREATER(&buf->keys, s, node, keybuf_nonoverlapping_cmp);
+
+	while (w && bkey_cmp(&START_KEY(&w->key), end) < 0) {
+		p = w;
+		w = RB_NEXT(w, node);
+
+		if (p->private)
+			ret = true;
+		else
+			__bch_keybuf_del(buf, p);
+	}
+
+	spin_unlock(&buf->lock);
+	return ret;
+}
+
+struct keybuf_key *bch_keybuf_next(struct keybuf *buf)
+{
+	struct keybuf_key *w;
+
+	spin_lock(&buf->lock);
+
+	w = RB_FIRST(&buf->keys, struct keybuf_key, node);
+
+	while (w && w->private)
+		w = RB_NEXT(w, node);
+
+	if (w)
+		w->private = ERR_PTR(-EINTR);
+
+	spin_unlock(&buf->lock);
+	return w;
+}
+
+struct keybuf_key *bch_keybuf_next_rescan(struct cache_set *c,
+					  struct keybuf *buf,
+					  struct bkey *end,
+					  keybuf_pred_fn *pred)
+{
+	struct keybuf_key *ret;
+
+	while (1) {
+		ret = bch_keybuf_next(buf);
+		if (ret)
+			break;
+
+		if (bkey_cmp(&buf->last_scanned, end) >= 0) {
+			pr_debug("scan finished\n");
+			break;
+		}
+
+		bch_refill_keybuf(c, buf, end, pred);
+	}
+
+	return ret;
+}
+
+void bch_keybuf_init(struct keybuf *buf)
+{
+	buf->last_scanned	= MAX_KEY;
+	buf->keys		= RB_ROOT;
+
+	spin_lock_init(&buf->lock);
+	array_allocator_init(&buf->freelist);
+}
+
+void bch_btree_exit(void)
+{
+	if (btree_io_wq)
+		destroy_workqueue(btree_io_wq);
+}
+
+int __init bch_btree_init(void)
+{
+	btree_io_wq = alloc_workqueue("bch_btree_io", WQ_MEM_RECLAIM, 0);
+	if (!btree_io_wq)
+		return -ENOMEM;
+
+	return 0;
+}