path: root/fs/bcachefs/alloc_background.c

// SPDX-License-Identifier: GPL-2.0
#include "bcachefs.h"
#include "alloc_background.h"
#include "alloc_foreground.h"
#include "btree_cache.h"
#include "btree_io.h"
#include "btree_key_cache.h"
#include "btree_update.h"
#include "btree_update_interior.h"
#include "btree_gc.h"
#include "buckets.h"
#include "buckets_waiting_for_journal.h"
#include "clock.h"
#include "debug.h"
#include "ec.h"
#include "error.h"
#include "lru.h"
#include "recovery.h"
#include "trace.h"
#include "varint.h"

#include <linux/kthread.h>
#include <linux/math64.h>
#include <linux/random.h>
#include <linux/rculist.h>
#include <linux/rcupdate.h>
#include <linux/sched/task.h>
#include <linux/sort.h>

/* Persistent alloc info: */

static const unsigned BCH_ALLOC_V1_FIELD_BYTES[] = {
#define x(name, bits) [BCH_ALLOC_FIELD_V1_##name] = bits / 8,
	BCH_ALLOC_FIELDS_V1()
#undef x
};

const char * const bch2_bucket_states[] = {
	"free",
	"need gc gens",
	"need discard",
	"cached",
	"dirty",
	NULL
};

struct bkey_alloc_unpacked {
	u64		journal_seq;
	u64		bucket;
	u8		dev;
	u8		gen;
	u8		oldest_gen;
	u8		data_type;
	bool		need_discard:1;
	bool		need_inc_gen:1;
#define x(_name, _bits)	u##_bits _name;
	BCH_ALLOC_FIELDS_V2()
#undef  x
};

static inline u64 alloc_field_v1_get(const struct bch_alloc *a,
				     const void **p, unsigned field)
{
	unsigned bytes = BCH_ALLOC_V1_FIELD_BYTES[field];
	u64 v;

	if (!(a->fields & (1 << field)))
		return 0;

	switch (bytes) {
	case 1:
		v = *((const u8 *) *p);
		break;
	case 2:
		v = le16_to_cpup(*p);
		break;
	case 4:
		v = le32_to_cpup(*p);
		break;
	case 8:
		v = le64_to_cpup(*p);
		break;
	default:
		BUG();
	}

	*p += bytes;
	return v;
}

static inline void alloc_field_v1_put(struct bkey_i_alloc *a, void **p,
				      unsigned field, u64 v)
{
	unsigned bytes = BCH_ALLOC_V1_FIELD_BYTES[field];

	if (!v)
		return;

	a->v.fields |= 1 << field;

	switch (bytes) {
	case 1:
		*((u8 *) *p) = v;
		break;
	case 2:
		*((__le16 *) *p) = cpu_to_le16(v);
		break;
	case 4:
		*((__le32 *) *p) = cpu_to_le32(v);
		break;
	case 8:
		*((__le64 *) *p) = cpu_to_le64(v);
		break;
	default:
		BUG();
	}

	*p += bytes;
}

static void bch2_alloc_unpack_v1(struct bkey_alloc_unpacked *out,
				 struct bkey_s_c k)
{
	const struct bch_alloc *in = bkey_s_c_to_alloc(k).v;
	const void *d = in->data;
	unsigned idx = 0;

	out->gen = in->gen;

#define x(_name, _bits) out->_name = alloc_field_v1_get(in, &d, idx++);
	BCH_ALLOC_FIELDS_V1()
#undef  x
}

static int bch2_alloc_unpack_v2(struct bkey_alloc_unpacked *out,
				struct bkey_s_c k)
{
	struct bkey_s_c_alloc_v2 a = bkey_s_c_to_alloc_v2(k);
	const u8 *in = a.v->data;
	const u8 *end = bkey_val_end(a);
	unsigned fieldnr = 0;
	int ret;
	u64 v;

	out->gen	= a.v->gen;
	out->oldest_gen	= a.v->oldest_gen;
	out->data_type	= a.v->data_type;

#define x(_name, _bits)							\
	if (fieldnr < a.v->nr_fields) {					\
		ret = bch2_varint_decode_fast(in, end, &v);		\
		if (ret < 0)						\
			return ret;					\
		in += ret;						\
	} else {							\
		v = 0;							\
	}								\
	out->_name = v;							\
	if (v != out->_name)						\
		return -1;						\
	fieldnr++;

	BCH_ALLOC_FIELDS_V2()
#undef  x
	return 0;
}

static int bch2_alloc_unpack_v3(struct bkey_alloc_unpacked *out,
				struct bkey_s_c k)
{
	struct bkey_s_c_alloc_v3 a = bkey_s_c_to_alloc_v3(k);
	const u8 *in = a.v->data;
	const u8 *end = bkey_val_end(a);
	unsigned fieldnr = 0;
	int ret;
	u64 v;

	out->gen	= a.v->gen;
	out->oldest_gen	= a.v->oldest_gen;
	out->data_type	= a.v->data_type;
	out->need_discard = BCH_ALLOC_V3_NEED_DISCARD(a.v);
	out->need_inc_gen = BCH_ALLOC_V3_NEED_INC_GEN(a.v);
	out->journal_seq = le64_to_cpu(a.v->journal_seq);

#define x(_name, _bits)							\
	if (fieldnr < a.v->nr_fields) {					\
		ret = bch2_varint_decode_fast(in, end, &v);		\
		if (ret < 0)						\
			return ret;					\
		in += ret;						\
	} else {							\
		v = 0;							\
	}								\
	out->_name = v;							\
	if (v != out->_name)						\
		return -1;						\
	fieldnr++;

	BCH_ALLOC_FIELDS_V2()
#undef  x
	return 0;
}

static struct bkey_alloc_unpacked bch2_alloc_unpack(struct bkey_s_c k)
{
	struct bkey_alloc_unpacked ret = {
		.dev	= k.k->p.inode,
		.bucket	= k.k->p.offset,
		.gen	= 0,
	};

	switch (k.k->type) {
	case KEY_TYPE_alloc:
		bch2_alloc_unpack_v1(&ret, k);
		break;
	case KEY_TYPE_alloc_v2:
		bch2_alloc_unpack_v2(&ret, k);
		break;
	case KEY_TYPE_alloc_v3:
		bch2_alloc_unpack_v3(&ret, k);
		break;
	}

	return ret;
}

void bch2_alloc_to_v4(struct bkey_s_c k, struct bch_alloc_v4 *out)
{
	if (k.k->type == KEY_TYPE_alloc_v4) {
		*out = *bkey_s_c_to_alloc_v4(k).v;
	} else {
		struct bkey_alloc_unpacked u = bch2_alloc_unpack(k);

		*out = (struct bch_alloc_v4) {
			.journal_seq		= u.journal_seq,
			.flags			= u.need_discard,
			.gen			= u.gen,
			.oldest_gen		= u.oldest_gen,
			.data_type		= u.data_type,
			.stripe_redundancy	= u.stripe_redundancy,
			.dirty_sectors		= u.dirty_sectors,
			.cached_sectors		= u.cached_sectors,
			.io_time[READ]		= u.read_time,
			.io_time[WRITE]		= u.write_time,
			.stripe			= u.stripe,
		};
	}
}

struct bkey_i_alloc_v4 *bch2_alloc_to_v4_mut(struct btree_trans *trans, struct bkey_s_c k)
{
	struct bkey_i_alloc_v4 *ret;

	if (k.k->type == KEY_TYPE_alloc_v4) {
		ret = bch2_trans_kmalloc(trans, bkey_bytes(k.k));
		if (!IS_ERR(ret))
			bkey_reassemble(&ret->k_i, k);
	} else {
		ret = bch2_trans_kmalloc(trans, sizeof(*ret));
		if (!IS_ERR(ret)) {
			bkey_alloc_v4_init(&ret->k_i);
			ret->k.p = k.k->p;
			bch2_alloc_to_v4(k, &ret->v);
		}
	}
	return ret;
}

struct bkey_i_alloc_v4 *
bch2_trans_start_alloc_update(struct btree_trans *trans, struct btree_iter *iter,
			      struct bpos pos)
{
	struct bkey_s_c k;
	struct bkey_i_alloc_v4 *a;
	int ret;

	bch2_trans_iter_init(trans, iter, BTREE_ID_alloc, pos,
			     BTREE_ITER_WITH_UPDATES|
			     BTREE_ITER_CACHED|
			     BTREE_ITER_INTENT);
	k = bch2_btree_iter_peek_slot(iter);
	ret = bkey_err(k);
	if (ret) {
		bch2_trans_iter_exit(trans, iter);
		return ERR_PTR(ret);
	}

	a = bch2_alloc_to_v4_mut(trans, k);
	if (IS_ERR(a))
		bch2_trans_iter_exit(trans, iter);
	return a;
}

static unsigned bch_alloc_v1_val_u64s(const struct bch_alloc *a)
{
	unsigned i, bytes = offsetof(struct bch_alloc, data);

	for (i = 0; i < ARRAY_SIZE(BCH_ALLOC_V1_FIELD_BYTES); i++)
		if (a->fields & (1 << i))
			bytes += BCH_ALLOC_V1_FIELD_BYTES[i];

	return DIV_ROUND_UP(bytes, sizeof(u64));
}

int bch2_alloc_v1_invalid(const struct bch_fs *c, struct bkey_s_c k, struct printbuf *err)
{
	struct bkey_s_c_alloc a = bkey_s_c_to_alloc(k);

	if (!bch2_dev_exists2(c, k.k->p.inode)) {
		pr_buf(err, "invalid device (%llu)", k.k->p.inode);
		return -EINVAL;
	}

	/* allow for unknown fields */
	if (bkey_val_u64s(a.k) < bch_alloc_v1_val_u64s(a.v)) {
		pr_buf(err, "incorrect value size (%zu < %u)",
		       bkey_val_u64s(a.k), bch_alloc_v1_val_u64s(a.v));
		return -EINVAL;
	}

	return 0;
}

int bch2_alloc_v2_invalid(const struct bch_fs *c, struct bkey_s_c k, struct printbuf *err)
{
	struct bkey_alloc_unpacked u;

	if (!bch2_dev_exists2(c, k.k->p.inode)) {
		pr_buf(err, "invalid device (%llu)", k.k->p.inode);
		return -EINVAL;
	}

	if (bch2_alloc_unpack_v2(&u, k)) {
		pr_buf(err, "unpack error");
		return -EINVAL;
	}

	return 0;
}

int bch2_alloc_v3_invalid(const struct bch_fs *c, struct bkey_s_c k, struct printbuf *err)
{
	struct bkey_alloc_unpacked u;
	struct bch_dev *ca;

	if (!bch2_dev_exists2(c, k.k->p.inode)) {
		pr_buf(err, "invalid device (%llu)", k.k->p.inode);
		return -EINVAL;
	}

	ca = bch_dev_bkey_exists(c, k.k->p.inode);

	if (k.k->p.offset < ca->mi.first_bucket ||
	    k.k->p.offset >= ca->mi.nbuckets) {
		pr_buf(err, "invalid bucket");
		return -EINVAL;
	}

	if (bch2_alloc_unpack_v3(&u, k)) {
		pr_buf(err, "unpack error");
		return -EINVAL;
	}

	return 0;
}

int bch2_alloc_v4_invalid(const struct bch_fs *c, struct bkey_s_c k, struct printbuf *err)
{
	struct bch_dev *ca;

	if (!bch2_dev_exists2(c, k.k->p.inode)) {
		pr_buf(err, "invalid device (%llu)", k.k->p.inode);
		return -EINVAL;
	}

	ca = bch_dev_bkey_exists(c, k.k->p.inode);

	if (k.k->p.offset < ca->mi.first_bucket ||
	    k.k->p.offset >= ca->mi.nbuckets) {
		pr_buf(err, "invalid bucket");
		return -EINVAL;
	}

	return 0;
}

void bch2_alloc_v4_swab(struct bkey_s k)
{
	struct bch_alloc_v4 *a = bkey_s_to_alloc_v4(k).v;

	a->journal_seq		= swab64(a->journal_seq);
	a->flags		= swab32(a->flags);
	a->dirty_sectors	= swab32(a->dirty_sectors);
	a->cached_sectors	= swab32(a->cached_sectors);
	a->io_time[0]		= swab64(a->io_time[0]);
	a->io_time[1]		= swab64(a->io_time[1]);
	a->stripe		= swab32(a->stripe);
	a->nr_external_backpointers = swab32(a->nr_external_backpointers);
}

void bch2_alloc_to_text(struct printbuf *out, struct bch_fs *c, struct bkey_s_c k)
{
	struct bch_alloc_v4 a;

	bch2_alloc_to_v4(k, &a);

	pr_buf(out, "gen %u oldest_gen %u data_type %s journal_seq %llu need_discard %llu",
	       a.gen, a.oldest_gen, bch2_data_types[a.data_type],
	       a.journal_seq, BCH_ALLOC_V4_NEED_DISCARD(&a));
	pr_buf(out, " dirty_sectors %u",	a.dirty_sectors);
	pr_buf(out, " cached_sectors %u",	a.cached_sectors);
	pr_buf(out, " stripe %u",		a.stripe);
	pr_buf(out, " stripe_redundancy %u",	a.stripe_redundancy);
	pr_buf(out, " read_time %llu",		a.io_time[READ]);
	pr_buf(out, " write_time %llu",		a.io_time[WRITE]);
}

int bch2_alloc_read(struct bch_fs *c)
{
	struct btree_trans trans;
	struct btree_iter iter;
	struct bkey_s_c k;
	struct bch_alloc_v4 a;
	struct bch_dev *ca;
	int ret;

	bch2_trans_init(&trans, c, 0, 0);

	for_each_btree_key(&trans, iter, BTREE_ID_alloc, POS_MIN,
			   BTREE_ITER_PREFETCH, k, ret) {
		ca = bch_dev_bkey_exists(c, k.k->p.inode);
		bch2_alloc_to_v4(k, &a);

		*bucket_gen(ca, k.k->p.offset) = a.gen;
	}
	bch2_trans_iter_exit(&trans, &iter);

	bch2_trans_exit(&trans);

	if (ret)
		bch_err(c, "error reading alloc info: %i", ret);

	return ret;
}

/* Free space/discard btree: */

static int bch2_bucket_do_index(struct btree_trans *trans,
				struct bkey_s_c alloc_k,
				struct bch_alloc_v4 a,
				bool set)
{
	struct bch_fs *c = trans->c;
	struct bch_dev *ca = bch_dev_bkey_exists(c, alloc_k.k->p.inode);
	struct btree_iter iter;
	struct bkey_s_c old;
	struct bkey_i *k;
	enum bucket_state state = bucket_state(a);
	enum btree_id btree;
	enum bch_bkey_type old_type = !set ? KEY_TYPE_set : KEY_TYPE_deleted;
	enum bch_bkey_type new_type =  set ? KEY_TYPE_set : KEY_TYPE_deleted;
	struct printbuf buf = PRINTBUF;
	int ret;

	if (state != BUCKET_free &&
	    state != BUCKET_need_discard)
		return 0;

	k = bch2_trans_kmalloc(trans, sizeof(*k));
	if (IS_ERR(k))
		return PTR_ERR(k);

	bkey_init(&k->k);
	k->k.type = new_type;

	switch (state) {
	case BUCKET_free:
		btree = BTREE_ID_freespace;
		k->k.p = alloc_freespace_pos(alloc_k.k->p, a);
		bch2_key_resize(&k->k, 1);
		break;
	case BUCKET_need_discard:
		btree = BTREE_ID_need_discard;
		k->k.p = alloc_k.k->p;
		break;
	default:
		return 0;
	}

	bch2_trans_iter_init(trans, &iter, btree,
			     bkey_start_pos(&k->k),
			     BTREE_ITER_INTENT);
	old = bch2_btree_iter_peek_slot(&iter);
	ret = bkey_err(old);
	if (ret)
		goto err;

	if (ca->mi.freespace_initialized &&
	    bch2_fs_inconsistent_on(old.k->type != old_type, c,
			"incorrect key when %s %s btree (got %s should be %s)\n"
			"  for %s",
			set ? "setting" : "clearing",
			bch2_btree_ids[btree],
			bch2_bkey_types[old.k->type],
			bch2_bkey_types[old_type],
			(bch2_bkey_val_to_text(&buf, c, alloc_k), buf.buf))) {
		ret = -EIO;
		goto err;
	}

	ret = bch2_trans_update(trans, &iter, k, 0);
err:
	bch2_trans_iter_exit(trans, &iter);
	printbuf_exit(&buf);
	return ret;
}

int bch2_trans_mark_alloc(struct btree_trans *trans,
			  struct bkey_s_c old, struct bkey_i *new,
			  unsigned flags)
{
	struct bch_fs *c = trans->c;
	struct bch_alloc_v4 old_a, *new_a;
	u64 old_lru, new_lru;
	int ret = 0;

	/*
	 * Deletion only happens in the device removal path, with
	 * BTREE_TRIGGER_NORUN:
	 */
	BUG_ON(new->k.type != KEY_TYPE_alloc_v4);

	bch2_alloc_to_v4(old, &old_a);
	new_a = &bkey_i_to_alloc_v4(new)->v;

	if (new_a->dirty_sectors > old_a.dirty_sectors ||
	    new_a->cached_sectors > old_a.cached_sectors) {
		new_a->io_time[READ] = max_t(u64, 1, atomic64_read(&c->io_clock[READ].now));
		new_a->io_time[WRITE]= max_t(u64, 1, atomic64_read(&c->io_clock[WRITE].now));
		SET_BCH_ALLOC_V4_NEED_INC_GEN(new_a, true);
		SET_BCH_ALLOC_V4_NEED_DISCARD(new_a, true);
	}

	if (old_a.data_type && !new_a->data_type &&
	    old_a.gen == new_a->gen &&
	    !bch2_bucket_is_open_safe(c, new->k.p.inode, new->k.p.offset)) {
		new_a->gen++;
		SET_BCH_ALLOC_V4_NEED_INC_GEN(new_a, false);
	}

	if (bucket_state(old_a) != bucket_state(*new_a) ||
	    (bucket_state(*new_a) == BUCKET_free &&
	     alloc_freespace_genbits(old_a) != alloc_freespace_genbits(*new_a))) {
		ret =   bch2_bucket_do_index(trans, old, old_a, false) ?:
			bch2_bucket_do_index(trans, bkey_i_to_s_c(new), *new_a, true);
		if (ret)
			return ret;
	}

	old_lru = alloc_lru_idx(old_a);
	new_lru = alloc_lru_idx(*new_a);

	if (old_lru != new_lru) {
		ret = bch2_lru_change(trans, new->k.p.inode, new->k.p.offset,
				      old_lru, &new_lru);
		if (ret)
			return ret;

		if (new_lru && new_a->io_time[READ] != new_lru)
			new_a->io_time[READ] = new_lru;
	}

	return 0;
}

static int bch2_check_alloc_key(struct btree_trans *trans,
				struct btree_iter *alloc_iter)
{
	struct bch_fs *c = trans->c;
	struct btree_iter discard_iter, freespace_iter;
	struct bch_alloc_v4 a;
	unsigned discard_key_type, freespace_key_type;
	struct bkey_s_c alloc_k, k;
	struct printbuf buf = PRINTBUF;
	struct printbuf buf2 = PRINTBUF;
	int ret;

	alloc_k = bch2_btree_iter_peek(alloc_iter);
	if (!alloc_k.k)
		return 0;

	ret = bkey_err(alloc_k);
	if (ret)
		return ret;

	bch2_alloc_to_v4(alloc_k, &a);
	discard_key_type = bucket_state(a) == BUCKET_need_discard
		? KEY_TYPE_set : 0;
	freespace_key_type = bucket_state(a) == BUCKET_free
		? KEY_TYPE_set : 0;

	bch2_trans_iter_init(trans, &discard_iter, BTREE_ID_need_discard,
			     alloc_k.k->p, 0);
	bch2_trans_iter_init(trans, &freespace_iter, BTREE_ID_freespace,
			     alloc_freespace_pos(alloc_k.k->p, a), 0);

	k = bch2_btree_iter_peek_slot(&discard_iter);
	ret = bkey_err(k);
	if (ret)
		goto err;

	if (fsck_err_on(k.k->type != discard_key_type, c,
			"incorrect key in need_discard btree (got %s should be %s)\n"
			"  %s",
			bch2_bkey_types[k.k->type],
			bch2_bkey_types[discard_key_type],
			(bch2_bkey_val_to_text(&buf, c, alloc_k), buf.buf))) {
		struct bkey_i *update =
			bch2_trans_kmalloc(trans, sizeof(*update));

		ret = PTR_ERR_OR_ZERO(update);
		if (ret)
			goto err;

		bkey_init(&update->k);
		update->k.type	= discard_key_type;
		update->k.p	= discard_iter.pos;

		ret = bch2_trans_update(trans, &discard_iter, update, 0);
		if (ret)
			goto err;
	}

	k = bch2_btree_iter_peek_slot(&freespace_iter);
	ret = bkey_err(k);
	if (ret)
		goto err;

	if (fsck_err_on(k.k->type != freespace_key_type, c,
			"incorrect key in freespace btree (got %s should be %s)\n"
			"  %s",
			bch2_bkey_types[k.k->type],
			bch2_bkey_types[freespace_key_type],
			(printbuf_reset(&buf),
			 bch2_bkey_val_to_text(&buf, c, alloc_k), buf.buf))) {
		struct bkey_i *update =
			bch2_trans_kmalloc(trans, sizeof(*update));

		ret = PTR_ERR_OR_ZERO(update);
		if (ret)
			goto err;

		bkey_init(&update->k);
		update->k.type	= freespace_key_type;
		update->k.p	= freespace_iter.pos;
		bch2_key_resize(&update->k, 1);

		ret = bch2_trans_update(trans, &freespace_iter, update, 0);
		if (ret)
			goto err;
	}
err:
fsck_err:
	bch2_trans_iter_exit(trans, &freespace_iter);
	bch2_trans_iter_exit(trans, &discard_iter);
	printbuf_exit(&buf2);
	printbuf_exit(&buf);
	return ret;
}

static inline bool bch2_dev_bucket_exists(struct bch_fs *c, struct bpos pos)
{
	struct bch_dev *ca;

	if (pos.inode >= c->sb.nr_devices || !c->devs[pos.inode])
		return false;

	ca = bch_dev_bkey_exists(c, pos.inode);
	return pos.offset >= ca->mi.first_bucket &&
		pos.offset < ca->mi.nbuckets;
}

static int bch2_check_freespace_key(struct btree_trans *trans,
				    struct btree_iter *freespace_iter,
				    bool initial)
{
	struct bch_fs *c = trans->c;
	struct btree_iter alloc_iter;
	struct bkey_s_c k, freespace_k;
	struct bch_alloc_v4 a;
	u64 genbits;
	struct bpos pos;
	struct bkey_i *update;
	struct printbuf buf = PRINTBUF;
	int ret;

	freespace_k = bch2_btree_iter_peek(freespace_iter);
	if (!freespace_k.k)
		return 1;

	ret = bkey_err(freespace_k);
	if (ret)
		return ret;

	pos = freespace_iter->pos;
	pos.offset &= ~(~0ULL << 56);
	genbits = freespace_iter->pos.offset & (~0ULL << 56);

	bch2_trans_iter_init(trans, &alloc_iter, BTREE_ID_alloc, pos, 0);

	if (fsck_err_on(!bch2_dev_bucket_exists(c, pos), c,
			"%llu:%llu set in freespace btree but device or bucket does not exist",
			pos.inode, pos.offset))
		goto delete;

	k = bch2_btree_iter_peek_slot(&alloc_iter);
	ret = bkey_err(k);
	if (ret)
		goto err;

	bch2_alloc_to_v4(k, &a);

	if (fsck_err_on(bucket_state(a) != BUCKET_free ||
			genbits != alloc_freespace_genbits(a), c,
			"%s\n  incorrectly set in freespace index (free %u, genbits %llu should be %llu)",
			(bch2_bkey_val_to_text(&buf, c, k), buf.buf),
			bucket_state(a) == BUCKET_free,
			genbits >> 56, alloc_freespace_genbits(a) >> 56))
		goto delete;
out:
err:
fsck_err:
	bch2_trans_iter_exit(trans, &alloc_iter);
	printbuf_exit(&buf);
	return ret;
delete:
	update = bch2_trans_kmalloc(trans, sizeof(*update));
	ret = PTR_ERR_OR_ZERO(update);
	if (ret)
		goto err;

	bkey_init(&update->k);
	update->k.p = freespace_iter->pos;
	bch2_key_resize(&update->k, 1);

	ret   = bch2_trans_update(trans, freespace_iter, update, 0) ?:
		bch2_trans_commit(trans, NULL, NULL, 0);
	goto out;
}

int bch2_check_alloc_info(struct bch_fs *c, bool initial)
{
	struct btree_trans trans;
	struct btree_iter iter;
	struct bkey_s_c k;
	int ret = 0, last_dev = -1;

	bch2_trans_init(&trans, c, 0, 0);

	for_each_btree_key(&trans, iter, BTREE_ID_alloc, POS_MIN,
			   BTREE_ITER_PREFETCH, k, ret) {
		if (k.k->p.inode != last_dev) {
			struct bch_dev *ca = bch_dev_bkey_exists(c, k.k->p.inode);

			if (!ca->mi.freespace_initialized) {
				bch2_btree_iter_set_pos(&iter, POS(k.k->p.inode + 1, 0));
				continue;
			}

			last_dev = k.k->p.inode;
		}

		ret = __bch2_trans_do(&trans, NULL, NULL, 0,
			bch2_check_alloc_key(&trans, &iter));
		if (ret)
			break;
	}
	bch2_trans_iter_exit(&trans, &iter);

	if (ret)
		goto err;

	bch2_trans_iter_init(&trans, &iter, BTREE_ID_freespace, POS_MIN,
			     BTREE_ITER_PREFETCH);
	while (1) {
		ret = __bch2_trans_do(&trans, NULL, NULL, 0,
			bch2_check_freespace_key(&trans, &iter, initial));
		if (ret)
			break;

		bch2_btree_iter_set_pos(&iter, bpos_nosnap_successor(iter.pos));
	}
	bch2_trans_iter_exit(&trans, &iter);
err:
	bch2_trans_exit(&trans);
	return ret < 0 ? ret : 0;
}

static int bch2_check_alloc_to_lru_ref(struct btree_trans *trans,
				       struct btree_iter *alloc_iter)
{
	struct bch_fs *c = trans->c;
	struct btree_iter lru_iter;
	struct bch_alloc_v4 a;
	struct bkey_s_c alloc_k, k;
	struct printbuf buf = PRINTBUF;
	struct printbuf buf2 = PRINTBUF;
	int ret;

	alloc_k = bch2_btree_iter_peek(alloc_iter);
	if (!alloc_k.k)
		return 0;

	ret = bkey_err(alloc_k);
	if (ret)
		return ret;

	bch2_alloc_to_v4(alloc_k, &a);

	if (bucket_state(a) != BUCKET_cached)
		return 0;

	bch2_trans_iter_init(trans, &lru_iter, BTREE_ID_lru,
			     POS(alloc_k.k->p.inode, a.io_time[READ]), 0);

	k = bch2_btree_iter_peek_slot(&lru_iter);
	ret = bkey_err(k);
	if (ret)
		goto err;

	if (fsck_err_on(!a.io_time[READ], c,
			"cached bucket with read_time 0\n"
			"  %s",
		(printbuf_reset(&buf),
		 bch2_bkey_val_to_text(&buf, c, alloc_k), buf.buf)) ||
	    fsck_err_on(k.k->type != KEY_TYPE_lru ||
			le64_to_cpu(bkey_s_c_to_lru(k).v->idx) != alloc_k.k->p.offset, c,
			"incorrect/missing lru entry\n"
			"  %s\n"
			"  %s",
			(printbuf_reset(&buf),
			 bch2_bkey_val_to_text(&buf, c, alloc_k), buf.buf),
			(bch2_bkey_val_to_text(&buf2, c, k), buf2.buf))) {
		u64 read_time = a.io_time[READ];

		if (!a.io_time[READ])
			a.io_time[READ] = atomic64_read(&c->io_clock[READ].now);

		ret = bch2_lru_change(trans,
				      alloc_k.k->p.inode,
				      alloc_k.k->p.offset,
				      0, &a.io_time[READ]);
		if (ret)
			goto err;

		if (a.io_time[READ] != read_time) {
			struct bkey_i_alloc_v4 *a_mut =
				bch2_alloc_to_v4_mut(trans, alloc_k);
			ret = PTR_ERR_OR_ZERO(a_mut);
			if (ret)
				goto err;

			a_mut->v.io_time[READ] = a.io_time[READ];
			ret = bch2_trans_update(trans, alloc_iter,
						&a_mut->k_i, BTREE_TRIGGER_NORUN);
			if (ret)
				goto err;
		}
	}
err:
fsck_err:
	bch2_trans_iter_exit(trans, &lru_iter);
	printbuf_exit(&buf2);
	printbuf_exit(&buf);
	return ret;
}

int bch2_check_alloc_to_lru_refs(struct bch_fs *c)
{
	struct btree_trans trans;
	struct btree_iter iter;
	struct bkey_s_c k;
	int ret = 0;

	bch2_trans_init(&trans, c, 0, 0);

	for_each_btree_key(&trans, iter, BTREE_ID_alloc, POS_MIN,
			   BTREE_ITER_PREFETCH, k, ret) {
		ret = __bch2_trans_do(&trans, NULL, NULL,
				      BTREE_INSERT_NOFAIL|
				      BTREE_INSERT_LAZY_RW,
			bch2_check_alloc_to_lru_ref(&trans, &iter));
		if (ret)
			break;
	}
	bch2_trans_iter_exit(&trans, &iter);

	bch2_trans_exit(&trans);
	return ret < 0 ? ret : 0;
}

static int bch2_clear_need_discard(struct btree_trans *trans, struct bpos pos,
				   struct bch_dev *ca, bool *discard_done)
{
	struct bch_fs *c = trans->c;
	struct btree_iter iter;
	struct bkey_s_c k;
	struct bkey_i_alloc_v4 *a;
	struct printbuf buf = PRINTBUF;
	int ret;

	bch2_trans_iter_init(trans, &iter, BTREE_ID_alloc, pos,
			     BTREE_ITER_CACHED);
	k = bch2_btree_iter_peek_slot(&iter);
	ret = bkey_err(k);
	if (ret)
		goto out;

	a = bch2_alloc_to_v4_mut(trans, k);
	ret = PTR_ERR_OR_ZERO(a);
	if (ret)
		goto out;

	if (BCH_ALLOC_V4_NEED_INC_GEN(&a->v)) {
		a->v.gen++;
		SET_BCH_ALLOC_V4_NEED_INC_GEN(&a->v, false);
		goto write;
	}

	BUG_ON(a->v.journal_seq > c->journal.flushed_seq_ondisk);

	if (bch2_fs_inconsistent_on(!BCH_ALLOC_V4_NEED_DISCARD(&a->v), c,
			"%s\n  incorrectly set in need_discard btree",
			(bch2_bkey_val_to_text(&buf, c, k), buf.buf))) {
		ret = -EIO;
		goto out;
	}

	if (!*discard_done && ca->mi.discard && !c->opts.nochanges) {
		/*
		 * This works without any other locks because this is the only
		 * thread that removes items from the need_discard tree
		 */
		bch2_trans_unlock(trans);
		blkdev_issue_discard(ca->disk_sb.bdev,
				     k.k->p.offset * ca->mi.bucket_size,
				     ca->mi.bucket_size,
				     GFP_KERNEL);
		*discard_done = true;

		ret = bch2_trans_relock(trans) ? 0 : -EINTR;
		if (ret)
			goto out;
	}

	SET_BCH_ALLOC_V4_NEED_DISCARD(&a->v, false);
write:
	ret = bch2_trans_update(trans, &iter, &a->k_i, 0);
out:
	bch2_trans_iter_exit(trans, &iter);
	printbuf_exit(&buf);
	return ret;
}

static void bch2_do_discards_work(struct work_struct *work)
{
	struct bch_fs *c = container_of(work, struct bch_fs, discard_work);
	struct bch_dev *ca = NULL;
	struct btree_trans trans;
	struct btree_iter iter;
	struct bkey_s_c k;
	u64 seen = 0, open = 0, need_journal_commit = 0, discarded = 0;
	int ret;

	bch2_trans_init(&trans, c, 0, 0);

	for_each_btree_key(&trans, iter, BTREE_ID_need_discard,
			   POS_MIN, 0, k, ret) {
		bool discard_done = false;

		if (ca && k.k->p.inode != ca->dev_idx) {
			percpu_ref_put(&ca->io_ref);
			ca = NULL;
		}

		if (!ca) {
			ca = bch_dev_bkey_exists(c, k.k->p.inode);
			if (!percpu_ref_tryget(&ca->io_ref)) {
				ca = NULL;
				bch2_btree_iter_set_pos(&iter, POS(k.k->p.inode + 1, 0));
				continue;
			}
		}

		seen++;

		if (bch2_bucket_is_open_safe(c, k.k->p.inode, k.k->p.offset)) {
			open++;
			continue;
		}

		if (bch2_bucket_needs_journal_commit(&c->buckets_waiting_for_journal,
				c->journal.flushed_seq_ondisk,
				k.k->p.inode, k.k->p.offset)) {
			need_journal_commit++;
			continue;
		}

		ret = __bch2_trans_do(&trans, NULL, NULL,
				      BTREE_INSERT_USE_RESERVE|
				      BTREE_INSERT_NOFAIL,
				bch2_clear_need_discard(&trans, k.k->p, ca, &discard_done));
		if (ret)
			break;

		discarded++;
	}
	bch2_trans_iter_exit(&trans, &iter);

	if (ca)
		percpu_ref_put(&ca->io_ref);

	bch2_trans_exit(&trans);

	if (need_journal_commit * 2 > seen)
		bch2_journal_flush_async(&c->journal, NULL);

	percpu_ref_put(&c->writes);

	trace_do_discards(c, seen, open, need_journal_commit, discarded, ret);
}

void bch2_do_discards(struct bch_fs *c)
{
	if (percpu_ref_tryget(&c->writes) &&
	    !queue_work(system_long_wq, &c->discard_work))
		percpu_ref_put(&c->writes);
}

static int invalidate_one_bucket(struct btree_trans *trans, struct bch_dev *ca)
{
	struct bch_fs *c = trans->c;
	struct btree_iter lru_iter, alloc_iter = { NULL };
	struct bkey_s_c k;
	struct bkey_i_alloc_v4 *a;
	u64 bucket, idx;
	int ret;

	bch2_trans_iter_init(trans, &lru_iter, BTREE_ID_lru,
			     POS(ca->dev_idx, 0), 0);
	k = bch2_btree_iter_peek(&lru_iter);
	ret = bkey_err(k);
	if (ret)
		goto out;

	if (!k.k || k.k->p.inode != ca->dev_idx)
		goto out;

	if (bch2_fs_inconsistent_on(k.k->type != KEY_TYPE_lru, c,
				    "non lru key in lru btree"))
		goto out;

	idx	= k.k->p.offset;
	bucket	= le64_to_cpu(bkey_s_c_to_lru(k).v->idx);

	a = bch2_trans_start_alloc_update(trans, &alloc_iter,
					  POS(ca->dev_idx, bucket));
	ret = PTR_ERR_OR_ZERO(a);
	if (ret)
		goto out;

	if (bch2_fs_inconsistent_on(idx != alloc_lru_idx(a->v), c,
			"invalidating bucket with wrong lru idx (got %llu should be %llu",
			idx, alloc_lru_idx(a->v)))
		goto out;

	SET_BCH_ALLOC_V4_NEED_INC_GEN(&a->v, false);
	a->v.gen++;
	a->v.data_type		= 0;
	a->v.dirty_sectors	= 0;
	a->v.cached_sectors	= 0;
	a->v.io_time[READ]	= atomic64_read(&c->io_clock[READ].now);
	a->v.io_time[WRITE]	= atomic64_read(&c->io_clock[WRITE].now);

	ret = bch2_trans_update(trans, &alloc_iter, &a->k_i,
				BTREE_TRIGGER_BUCKET_INVALIDATE);
out:
	bch2_trans_iter_exit(trans, &alloc_iter);
	bch2_trans_iter_exit(trans, &lru_iter);
	return ret;
}

static void bch2_do_invalidates_work(struct work_struct *work)
{
	struct bch_fs *c = container_of(work, struct bch_fs, invalidate_work);
	struct bch_dev *ca;
	struct btree_trans trans;
	unsigned i;
	int ret = 0;

	bch2_trans_init(&trans, c, 0, 0);

	for_each_member_device(ca, c, i)
		while (!ret && should_invalidate_buckets(ca))
			ret = __bch2_trans_do(&trans, NULL, NULL,
					      BTREE_INSERT_USE_RESERVE|
					      BTREE_INSERT_NOFAIL,
					invalidate_one_bucket(&trans, ca));

	bch2_trans_exit(&trans);
	percpu_ref_put(&c->writes);
}

void bch2_do_invalidates(struct bch_fs *c)
{
	if (percpu_ref_tryget(&c->writes))
		queue_work(system_long_wq, &c->invalidate_work);
}

static int bch2_dev_freespace_init(struct bch_fs *c, struct bch_dev *ca)
{
	struct btree_trans trans;
	struct btree_iter iter;
	struct bkey_s_c k;
	struct bch_alloc_v4 a;
	struct bch_member *m;
	int ret;

	bch2_trans_init(&trans, c, 0, 0);

	for_each_btree_key(&trans, iter, BTREE_ID_alloc,
			   POS(ca->dev_idx, ca->mi.first_bucket),
			   BTREE_ITER_SLOTS|
			   BTREE_ITER_PREFETCH, k, ret) {
		if (iter.pos.offset >= ca->mi.nbuckets)
			break;

		bch2_alloc_to_v4(k, &a);
		ret = __bch2_trans_do(&trans, NULL, NULL,
				      BTREE_INSERT_LAZY_RW,
				 bch2_bucket_do_index(&trans, k, a, true));
		if (ret)
			break;
	}
	bch2_trans_iter_exit(&trans, &iter);

	bch2_trans_exit(&trans);

	if (ret) {
		bch_err(ca, "error initializing free space: %i", ret);
		return ret;
	}

	mutex_lock(&c->sb_lock);
	m = bch2_sb_get_members(c->disk_sb.sb)->members + ca->dev_idx;
	SET_BCH_MEMBER_FREESPACE_INITIALIZED(m, true);
	mutex_unlock(&c->sb_lock);

	return ret;
}

int bch2_fs_freespace_init(struct bch_fs *c)
{
	struct bch_dev *ca;
	unsigned i;
	int ret = 0;
	bool doing_init = false;

	/*
	 * We can crash during the device add path, so we need to check this on
	 * every mount:
	 */

	for_each_member_device(ca, c, i) {
		if (ca->mi.freespace_initialized)
			continue;

		if (!doing_init) {
			bch_info(c, "initializing freespace");
			doing_init = true;
		}

		ret = bch2_dev_freespace_init(c, ca);
		if (ret) {
			percpu_ref_put(&ca->ref);
			return ret;
		}
	}

	if (doing_init) {
		mutex_lock(&c->sb_lock);
		bch2_write_super(c);
		mutex_unlock(&c->sb_lock);

		bch_verbose(c, "done initializing freespace");
	}

	return ret;
}

/* Bucket IO clocks: */

int bch2_bucket_io_time_reset(struct btree_trans *trans, unsigned dev,
			      size_t bucket_nr, int rw)
{
	struct bch_fs *c = trans->c;
	struct btree_iter iter;
	struct bkey_i_alloc_v4 *a;
	u64 now;
	int ret = 0;

	a = bch2_trans_start_alloc_update(trans, &iter,  POS(dev, bucket_nr));
	ret = PTR_ERR_OR_ZERO(a);
	if (ret)
		return ret;

	now = atomic64_read(&c->io_clock[rw].now);
	if (a->v.io_time[rw] == now)
		goto out;

	a->v.io_time[rw] = now;

	ret   = bch2_trans_update(trans, &iter, &a->k_i, 0) ?:
		bch2_trans_commit(trans, NULL, NULL, 0);
out:
	bch2_trans_iter_exit(trans, &iter);
	return ret;
}

/* Startup/shutdown (ro/rw): */

void bch2_recalc_capacity(struct bch_fs *c)
{
	struct bch_dev *ca;
	u64 capacity = 0, reserved_sectors = 0, gc_reserve;
	unsigned bucket_size_max = 0;
	unsigned long ra_pages = 0;
	unsigned i;

	lockdep_assert_held(&c->state_lock);

	for_each_online_member(ca, c, i) {
		struct backing_dev_info *bdi = ca->disk_sb.bdev->bd_disk->bdi;

		ra_pages += bdi->ra_pages;
	}

	bch2_set_ra_pages(c, ra_pages);

	for_each_rw_member(ca, c, i) {
		u64 dev_reserve = 0;

		/*
		 * We need to reserve buckets (from the number
		 * of currently available buckets) against
		 * foreground writes so that mainly copygc can
		 * make forward progress.
		 *
		 * We need enough to refill the various reserves
		 * from scratch - copygc will use its entire
		 * reserve all at once, then run against when
		 * its reserve is refilled (from the formerly
		 * available buckets).
		 *
		 * This reserve is just used when considering if
		 * allocations for foreground writes must wait -
		 * not -ENOSPC calculations.
		 */

		dev_reserve += ca->nr_btree_reserve * 2;
		dev_reserve += ca->mi.nbuckets >> 6; /* copygc reserve */

		dev_reserve += 1;	/* btree write point */
		dev_reserve += 1;	/* copygc write point */
		dev_reserve += 1;	/* rebalance write point */

		dev_reserve *= ca->mi.bucket_size;

		capacity += bucket_to_sector(ca, ca->mi.nbuckets -
					     ca->mi.first_bucket);

		reserved_sectors += dev_reserve * 2;

		bucket_size_max = max_t(unsigned, bucket_size_max,
					ca->mi.bucket_size);
	}

	gc_reserve = c->opts.gc_reserve_bytes
		? c->opts.gc_reserve_bytes >> 9
		: div64_u64(capacity * c->opts.gc_reserve_percent, 100);

	reserved_sectors = max(gc_reserve, reserved_sectors);

	reserved_sectors = min(reserved_sectors, capacity);

	c->capacity = capacity - reserved_sectors;

	c->bucket_size_max = bucket_size_max;

	/* Wake up case someone was waiting for buckets */
	closure_wake_up(&c->freelist_wait);
}

static bool bch2_dev_has_open_write_point(struct bch_fs *c, struct bch_dev *ca)
{
	struct open_bucket *ob;
	bool ret = false;

	for (ob = c->open_buckets;
	     ob < c->open_buckets + ARRAY_SIZE(c->open_buckets);
	     ob++) {
		spin_lock(&ob->lock);
		if (ob->valid && !ob->on_partial_list &&
		    ob->dev == ca->dev_idx)
			ret = true;
		spin_unlock(&ob->lock);
	}

	return ret;
}

/* device goes ro: */
void bch2_dev_allocator_remove(struct bch_fs *c, struct bch_dev *ca)
{
	unsigned i;

	/* First, remove device from allocation groups: */

	for (i = 0; i < ARRAY_SIZE(c->rw_devs); i++)
		clear_bit(ca->dev_idx, c->rw_devs[i].d);

	/*
	 * Capacity is calculated based off of devices in allocation groups:
	 */
	bch2_recalc_capacity(c);

	/* Next, close write points that point to this device... */
	for (i = 0; i < ARRAY_SIZE(c->write_points); i++)
		bch2_writepoint_stop(c, ca, &c->write_points[i]);

	bch2_writepoint_stop(c, ca, &c->copygc_write_point);
	bch2_writepoint_stop(c, ca, &c->rebalance_write_point);
	bch2_writepoint_stop(c, ca, &c->btree_write_point);

	mutex_lock(&c->btree_reserve_cache_lock);
	while (c->btree_reserve_cache_nr) {
		struct btree_alloc *a =
			&c->btree_reserve_cache[--c->btree_reserve_cache_nr];

		bch2_open_buckets_put(c, &a->ob);
	}
	mutex_unlock(&c->btree_reserve_cache_lock);

	while (1) {
		struct open_bucket *ob;

		spin_lock(&c->freelist_lock);
		if (!ca->open_buckets_partial_nr) {
			spin_unlock(&c->freelist_lock);
			break;
		}
		ob = c->open_buckets +
			ca->open_buckets_partial[--ca->open_buckets_partial_nr];
		ob->on_partial_list = false;
		spin_unlock(&c->freelist_lock);

		bch2_open_bucket_put(c, ob);
	}

	bch2_ec_stop_dev(c, ca);

	/*
	 * Wake up threads that were blocked on allocation, so they can notice
	 * the device can no longer be removed and the capacity has changed:
	 */
	closure_wake_up(&c->freelist_wait);

	/*
	 * journal_res_get() can block waiting for free space in the journal -
	 * it needs to notice there may not be devices to allocate from anymore:
	 */
	wake_up(&c->journal.wait);

	/* Now wait for any in flight writes: */

	closure_wait_event(&c->open_buckets_wait,
			   !bch2_dev_has_open_write_point(c, ca));
}

/* device goes rw: */
void bch2_dev_allocator_add(struct bch_fs *c, struct bch_dev *ca)
{
	unsigned i;

	for (i = 0; i < ARRAY_SIZE(c->rw_devs); i++)
		if (ca->mi.data_allowed & (1 << i))
			set_bit(ca->dev_idx, c->rw_devs[i].d);
}

void bch2_fs_allocator_background_init(struct bch_fs *c)
{
	spin_lock_init(&c->freelist_lock);
	INIT_WORK(&c->discard_work, bch2_do_discards_work);
	INIT_WORK(&c->invalidate_work, bch2_do_invalidates_work);
}