linux/fs/bcachefs/ec.c

// SPDX-License-Identifier: GPL-2.0

/* erasure coding */

#include "bcachefs.h"
#include "alloc_foreground.h"
#include "bkey_buf.h"
#include "bset.h"
#include "btree_gc.h"
#include "btree_update.h"
#include "buckets.h"
#include "disk_groups.h"
#include "ec.h"
#include "error.h"
#include "io.h"
#include "keylist.h"
#include "recovery.h"
#include "super-io.h"
#include "util.h"

#include <linux/sort.h>

#ifdef __KERNEL__

#include <linux/raid/pq.h>
#include <linux/raid/xor.h>

static void raid5_recov(unsigned disks, unsigned failed_idx,
			size_t size, void **data)
{
	unsigned i = 2, nr;

	BUG_ON(failed_idx >= disks);

	swap(data[0], data[failed_idx]);
	memcpy(data[0], data[1], size);

	while (i < disks) {
		nr = min_t(unsigned, disks - i, MAX_XOR_BLOCKS);
		xor_blocks(nr, size, data[0], data + i);
		i += nr;
	}

	swap(data[0], data[failed_idx]);
}

static void raid_gen(int nd, int np, size_t size, void **v)
{
	if (np >= 1)
		raid5_recov(nd + np, nd, size, v);
	if (np >= 2)
		raid6_call.gen_syndrome(nd + np, size, v);
	BUG_ON(np > 2);
}

static void raid_rec(int nr, int *ir, int nd, int np, size_t size, void **v)
{
	switch (nr) {
	case 0:
		break;
	case 1:
		if (ir[0] < nd + 1)
			raid5_recov(nd + 1, ir[0], size, v);
		else
			raid6_call.gen_syndrome(nd + np, size, v);
		break;
	case 2:
		if (ir[1] < nd) {
			/* data+data failure. */
			raid6_2data_recov(nd + np, size, ir[0], ir[1], v);
		} else if (ir[0] < nd) {
			/* data + p/q failure */

			if (ir[1] == nd) /* data + p failure */
				raid6_datap_recov(nd + np, size, ir[0], v);
			else { /* data + q failure */
				raid5_recov(nd + 1, ir[0], size, v);
				raid6_call.gen_syndrome(nd + np, size, v);
			}
		} else {
			raid_gen(nd, np, size, v);
		}
		break;
	default:
		BUG();
	}
}

#else

#include <raid/raid.h>

#endif

struct ec_bio {
	struct bch_dev		*ca;
	struct ec_stripe_buf	*buf;
	size_t			idx;
	struct bio		bio;
};

/* Stripes btree keys: */

const char *bch2_stripe_invalid(const struct bch_fs *c, struct bkey_s_c k)
{
	const struct bch_stripe *s = bkey_s_c_to_stripe(k).v;

	if (k.k->p.inode)
		return "invalid stripe key";

	if (bkey_val_bytes(k.k) < sizeof(*s))
		return "incorrect value size";

	if (bkey_val_bytes(k.k) < sizeof(*s) ||
	    bkey_val_u64s(k.k) < stripe_val_u64s(s))
		return "incorrect value size";

	return bch2_bkey_ptrs_invalid(c, k);
}

void bch2_stripe_to_text(struct printbuf *out, struct bch_fs *c,
			 struct bkey_s_c k)
{
	const struct bch_stripe *s = bkey_s_c_to_stripe(k).v;
	unsigned i;

	pr_buf(out, "algo %u sectors %u blocks %u:%u csum %u gran %u",
	       s->algorithm,
	       le16_to_cpu(s->sectors),
	       s->nr_blocks - s->nr_redundant,
	       s->nr_redundant,
	       s->csum_type,
	       1U << s->csum_granularity_bits);

	for (i = 0; i < s->nr_blocks; i++)
		pr_buf(out, " %u:%llu:%u", s->ptrs[i].dev,
		       (u64) s->ptrs[i].offset,
		       stripe_blockcount_get(s, i));
}

/* returns blocknr in stripe that we matched: */
static int bkey_matches_stripe(struct bch_stripe *s,
			       struct bkey_s_c k)
{
	struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(k);
	const struct bch_extent_ptr *ptr;
	unsigned i, nr_data = s->nr_blocks - s->nr_redundant;

	bkey_for_each_ptr(ptrs, ptr)
		for (i = 0; i < nr_data; i++)
			if (__bch2_ptr_matches_stripe(s, ptr, i))
				return i;

	return -1;
}

static bool extent_has_stripe_ptr(struct bkey_s_c k, u64 idx)
{
	switch (k.k->type) {
	case KEY_TYPE_extent: {
		struct bkey_s_c_extent e = bkey_s_c_to_extent(k);
		const union bch_extent_entry *entry;

		extent_for_each_entry(e, entry)
			if (extent_entry_type(entry) ==
			    BCH_EXTENT_ENTRY_stripe_ptr &&
			    entry->stripe_ptr.idx == idx)
				return true;

		break;
	}
	}

	return false;
}

/* Stripe bufs: */

static void ec_stripe_buf_exit(struct ec_stripe_buf *buf)
{
	unsigned i;

	for (i = 0; i < buf->key.v.nr_blocks; i++) {
		kvpfree(buf->data[i], buf->size << 9);
		buf->data[i] = NULL;
	}
}

static int ec_stripe_buf_init(struct ec_stripe_buf *buf,
			       unsigned offset, unsigned size)
{
	struct bch_stripe *v = &buf->key.v;
	unsigned csum_granularity = 1U << v->csum_granularity_bits;
	unsigned end = offset + size;
	unsigned i;

	BUG_ON(end > le16_to_cpu(v->sectors));

	offset	= round_down(offset, csum_granularity);
	end	= min_t(unsigned, le16_to_cpu(v->sectors),
			round_up(end, csum_granularity));

	buf->offset	= offset;
	buf->size	= end - offset;

	memset(buf->valid, 0xFF, sizeof(buf->valid));

	for (i = 0; i < buf->key.v.nr_blocks; i++) {
		buf->data[i] = kvpmalloc(buf->size << 9, GFP_KERNEL);
		if (!buf->data[i])
			goto err;
	}

	return 0;
err:
	ec_stripe_buf_exit(buf);
	return -ENOMEM;
}

/* Checksumming: */

static struct bch_csum ec_block_checksum(struct ec_stripe_buf *buf,
					 unsigned block, unsigned offset)
{
	struct bch_stripe *v = &buf->key.v;
	unsigned csum_granularity = 1 << v->csum_granularity_bits;
	unsigned end = buf->offset + buf->size;
	unsigned len = min(csum_granularity, end - offset);

	BUG_ON(offset >= end);
	BUG_ON(offset <  buf->offset);
	BUG_ON(offset & (csum_granularity - 1));
	BUG_ON(offset + len != le16_to_cpu(v->sectors) &&
	       (len & (csum_granularity - 1)));

	return bch2_checksum(NULL, v->csum_type,
			     null_nonce(),
			     buf->data[block] + ((offset - buf->offset) << 9),
			     len << 9);
}

static void ec_generate_checksums(struct ec_stripe_buf *buf)
{
	struct bch_stripe *v = &buf->key.v;
	unsigned i, j, csums_per_device = stripe_csums_per_device(v);

	if (!v->csum_type)
		return;

	BUG_ON(buf->offset);
	BUG_ON(buf->size != le16_to_cpu(v->sectors));

	for (i = 0; i < v->nr_blocks; i++)
		for (j = 0; j < csums_per_device; j++)
			stripe_csum_set(v, i, j,
				ec_block_checksum(buf, i, j << v->csum_granularity_bits));
}

static void ec_validate_checksums(struct bch_fs *c, struct ec_stripe_buf *buf)
{
	struct bch_stripe *v = &buf->key.v;
	unsigned csum_granularity = 1 << v->csum_granularity_bits;
	unsigned i;

	if (!v->csum_type)
		return;

	for (i = 0; i < v->nr_blocks; i++) {
		unsigned offset = buf->offset;
		unsigned end = buf->offset + buf->size;

		if (!test_bit(i, buf->valid))
			continue;

		while (offset < end) {
			unsigned j = offset >> v->csum_granularity_bits;
			unsigned len = min(csum_granularity, end - offset);
			struct bch_csum want = stripe_csum_get(v, i, j);
			struct bch_csum got = ec_block_checksum(buf, i, offset);

			if (bch2_crc_cmp(want, got)) {
				bch_err_ratelimited(c,
					"stripe checksum error at %u:%u: csum type %u, expected %llx got %llx",
					i, j, v->csum_type,
					want.lo, got.lo);
				clear_bit(i, buf->valid);
				break;
			}

			offset += len;
		}
	}
}

/* Erasure coding: */

static void ec_generate_ec(struct ec_stripe_buf *buf)
{
	struct bch_stripe *v = &buf->key.v;
	unsigned nr_data = v->nr_blocks - v->nr_redundant;
	unsigned bytes = le16_to_cpu(v->sectors) << 9;

	raid_gen(nr_data, v->nr_redundant, bytes, buf->data);
}

static unsigned ec_nr_failed(struct ec_stripe_buf *buf)
{
	return buf->key.v.nr_blocks -
		bitmap_weight(buf->valid, buf->key.v.nr_blocks);
}

static int ec_do_recov(struct bch_fs *c, struct ec_stripe_buf *buf)
{
	struct bch_stripe *v = &buf->key.v;
	unsigned i, failed[BCH_BKEY_PTRS_MAX], nr_failed = 0;
	unsigned nr_data = v->nr_blocks - v->nr_redundant;
	unsigned bytes = buf->size << 9;

	if (ec_nr_failed(buf) > v->nr_redundant) {
		bch_err_ratelimited(c,
			"error doing reconstruct read: unable to read enough blocks");
		return -1;
	}

	for (i = 0; i < nr_data; i++)
		if (!test_bit(i, buf->valid))
			failed[nr_failed++] = i;

	raid_rec(nr_failed, failed, nr_data, v->nr_redundant, bytes, buf->data);
	return 0;
}

/* IO: */

static void ec_block_endio(struct bio *bio)
{
	struct ec_bio *ec_bio = container_of(bio, struct ec_bio, bio);
	struct bch_dev *ca = ec_bio->ca;
	struct closure *cl = bio->bi_private;

	if (bch2_dev_io_err_on(bio->bi_status, ca, "erasure coding %s error: %s",
			       bio_data_dir(bio) ? "write" : "read",
			       bch2_blk_status_to_str(bio->bi_status)))
		clear_bit(ec_bio->idx, ec_bio->buf->valid);

	bio_put(&ec_bio->bio);
	percpu_ref_put(&ca->io_ref);
	closure_put(cl);
}

static void ec_block_io(struct bch_fs *c, struct ec_stripe_buf *buf,
			unsigned rw, unsigned idx, struct closure *cl)
{
	struct bch_stripe *v = &buf->key.v;
	unsigned offset = 0, bytes = buf->size << 9;
	struct bch_extent_ptr *ptr = &v->ptrs[idx];
	struct bch_dev *ca = bch_dev_bkey_exists(c, ptr->dev);
	enum bch_data_type data_type = idx < buf->key.v.nr_blocks - buf->key.v.nr_redundant
		? BCH_DATA_user
		: BCH_DATA_parity;

	if (ptr_stale(ca, ptr)) {
		bch_err_ratelimited(c,
				    "error %s stripe: stale pointer",
				    rw == READ ? "reading from" : "writing to");
		clear_bit(idx, buf->valid);
		return;
	}

	if (!bch2_dev_get_ioref(ca, rw)) {
		clear_bit(idx, buf->valid);
		return;
	}

	this_cpu_add(ca->io_done->sectors[rw][data_type], buf->size);

	while (offset < bytes) {
		unsigned nr_iovecs = min_t(size_t, BIO_MAX_VECS,
					   DIV_ROUND_UP(bytes, PAGE_SIZE));
		unsigned b = min_t(size_t, bytes - offset,
				   nr_iovecs << PAGE_SHIFT);
		struct ec_bio *ec_bio;

		ec_bio = container_of(bio_alloc_bioset(ca->disk_sb.bdev,
						       nr_iovecs,
						       rw,
						       GFP_KERNEL,
						       &c->ec_bioset),
				      struct ec_bio, bio);

		ec_bio->ca			= ca;
		ec_bio->buf			= buf;
		ec_bio->idx			= idx;

		ec_bio->bio.bi_iter.bi_sector	= ptr->offset + buf->offset + (offset >> 9);
		ec_bio->bio.bi_end_io		= ec_block_endio;
		ec_bio->bio.bi_private		= cl;

		bch2_bio_map(&ec_bio->bio, buf->data[idx] + offset, b);

		closure_get(cl);
		percpu_ref_get(&ca->io_ref);

		submit_bio(&ec_bio->bio);

		offset += b;
	}

	percpu_ref_put(&ca->io_ref);
}

static int get_stripe_key(struct bch_fs *c, u64 idx, struct ec_stripe_buf *stripe)
{
	struct btree_trans trans;
	struct btree_iter *iter;
	struct bkey_s_c k;
	int ret;

	bch2_trans_init(&trans, c, 0, 0);
	iter = bch2_trans_get_iter(&trans, BTREE_ID_EC, POS(0, idx), BTREE_ITER_SLOTS);
	k = bch2_btree_iter_peek_slot(iter);
	ret = bkey_err(k);
	if (ret)
		goto err;
	if (k.k->type != KEY_TYPE_stripe) {
		ret = -ENOENT;
		goto err;
	}
	bkey_reassemble(&stripe->key.k_i, k);
err:
	bch2_trans_exit(&trans);
	return ret;
}

/* recovery read path: */
int bch2_ec_read_extent(struct bch_fs *c, struct bch_read_bio *rbio)
{
	struct ec_stripe_buf *buf;
	struct closure cl;
	struct bch_stripe *v;
	unsigned i, offset;
	int ret = 0;

	closure_init_stack(&cl);

	BUG_ON(!rbio->pick.has_ec);

	buf = kzalloc(sizeof(*buf), GFP_NOIO);
	if (!buf)
		return -ENOMEM;

	ret = get_stripe_key(c, rbio->pick.ec.idx, buf);
	if (ret) {
		bch_err_ratelimited(c,
			"error doing reconstruct read: error %i looking up stripe", ret);
		kfree(buf);
		return -EIO;
	}

	v = &buf->key.v;

	if (!bch2_ptr_matches_stripe(v, rbio->pick)) {
		bch_err_ratelimited(c,
			"error doing reconstruct read: pointer doesn't match stripe");
		ret = -EIO;
		goto err;
	}

	offset = rbio->bio.bi_iter.bi_sector - v->ptrs[rbio->pick.ec.block].offset;
	if (offset + bio_sectors(&rbio->bio) > le16_to_cpu(v->sectors)) {
		bch_err_ratelimited(c,
			"error doing reconstruct read: read is bigger than stripe");
		ret = -EIO;
		goto err;
	}

	ret = ec_stripe_buf_init(buf, offset, bio_sectors(&rbio->bio));
	if (ret)
		goto err;

	for (i = 0; i < v->nr_blocks; i++)
		ec_block_io(c, buf, REQ_OP_READ, i, &cl);

	closure_sync(&cl);

	if (ec_nr_failed(buf) > v->nr_redundant) {
		bch_err_ratelimited(c,
			"error doing reconstruct read: unable to read enough blocks");
		ret = -EIO;
		goto err;
	}

	ec_validate_checksums(c, buf);

	ret = ec_do_recov(c, buf);
	if (ret)
		goto err;

	memcpy_to_bio(&rbio->bio, rbio->bio.bi_iter,
		      buf->data[rbio->pick.ec.block] + ((offset - buf->offset) << 9));
err:
	ec_stripe_buf_exit(buf);
	kfree(buf);
	return ret;
}

/* stripe bucket accounting: */

static int __ec_stripe_mem_alloc(struct bch_fs *c, size_t idx, gfp_t gfp)
{
	ec_stripes_heap n, *h = &c->ec_stripes_heap;

	if (idx >= h->size) {
		if (!init_heap(&n, max(1024UL, roundup_pow_of_two(idx + 1)), gfp))
			return -ENOMEM;

		spin_lock(&c->ec_stripes_heap_lock);
		if (n.size > h->size) {
			memcpy(n.data, h->data, h->used * sizeof(h->data[0]));
			n.used = h->used;
			swap(*h, n);
		}
		spin_unlock(&c->ec_stripes_heap_lock);

		free_heap(&n);
	}

	if (!genradix_ptr_alloc(&c->stripes[0], idx, gfp))
		return -ENOMEM;

	if (c->gc_pos.phase != GC_PHASE_NOT_RUNNING &&
	    !genradix_ptr_alloc(&c->stripes[1], idx, gfp))
		return -ENOMEM;

	return 0;
}

static int ec_stripe_mem_alloc(struct bch_fs *c,
			       struct btree_iter *iter)
{
	size_t idx = iter->pos.offset;
	int ret = 0;

	if (!__ec_stripe_mem_alloc(c, idx, GFP_NOWAIT|__GFP_NOWARN))
		return ret;

	bch2_trans_unlock(iter->trans);
	ret = -EINTR;

	if (!__ec_stripe_mem_alloc(c, idx, GFP_KERNEL))
		return ret;

	return -ENOMEM;
}

static ssize_t stripe_idx_to_delete(struct bch_fs *c)
{
	ec_stripes_heap *h = &c->ec_stripes_heap;

	return h->used && h->data[0].blocks_nonempty == 0
		? h->data[0].idx : -1;
}

static inline int ec_stripes_heap_cmp(ec_stripes_heap *h,
				      struct ec_stripe_heap_entry l,
				      struct ec_stripe_heap_entry r)
{
	return ((l.blocks_nonempty > r.blocks_nonempty) -
		(l.blocks_nonempty < r.blocks_nonempty));
}

static inline void ec_stripes_heap_set_backpointer(ec_stripes_heap *h,
						   size_t i)
{
	struct bch_fs *c = container_of(h, struct bch_fs, ec_stripes_heap);

	genradix_ptr(&c->stripes[0], h->data[i].idx)->heap_idx = i;
}

static void heap_verify_backpointer(struct bch_fs *c, size_t idx)
{
	ec_stripes_heap *h = &c->ec_stripes_heap;
	struct stripe *m = genradix_ptr(&c->stripes[0], idx);

	BUG_ON(!m->alive);
	BUG_ON(m->heap_idx >= h->used);
	BUG_ON(h->data[m->heap_idx].idx != idx);
}

void bch2_stripes_heap_del(struct bch_fs *c,
			   struct stripe *m, size_t idx)
{
	if (!m->on_heap)
		return;

	m->on_heap = false;

	heap_verify_backpointer(c, idx);

	heap_del(&c->ec_stripes_heap, m->heap_idx,
		 ec_stripes_heap_cmp,
		 ec_stripes_heap_set_backpointer);
}

void bch2_stripes_heap_insert(struct bch_fs *c,
			      struct stripe *m, size_t idx)
{
	if (m->on_heap)
		return;

	BUG_ON(heap_full(&c->ec_stripes_heap));

	m->on_heap = true;

	heap_add(&c->ec_stripes_heap, ((struct ec_stripe_heap_entry) {
			.idx = idx,
			.blocks_nonempty = m->blocks_nonempty,
		}),
		 ec_stripes_heap_cmp,
		 ec_stripes_heap_set_backpointer);

	heap_verify_backpointer(c, idx);
}

void bch2_stripes_heap_update(struct bch_fs *c,
			      struct stripe *m, size_t idx)
{
	ec_stripes_heap *h = &c->ec_stripes_heap;
	size_t i;

	if (!m->on_heap)
		return;

	heap_verify_backpointer(c, idx);

	h->data[m->heap_idx].blocks_nonempty = m->blocks_nonempty;

	i = m->heap_idx;
	heap_sift_up(h,	  i, ec_stripes_heap_cmp,
		     ec_stripes_heap_set_backpointer);
	heap_sift_down(h, i, ec_stripes_heap_cmp,
		       ec_stripes_heap_set_backpointer);

	heap_verify_backpointer(c, idx);

	if (stripe_idx_to_delete(c) >= 0 &&
	    !percpu_ref_is_dying(&c->writes))
		schedule_work(&c->ec_stripe_delete_work);
}

/* stripe deletion */

static int ec_stripe_delete(struct bch_fs *c, size_t idx)
{
	//pr_info("deleting stripe %zu", idx);
	return bch2_btree_delete_range(c, BTREE_ID_EC,
				       POS(0, idx),
				       POS(0, idx + 1),
				       NULL);
}

static void ec_stripe_delete_work(struct work_struct *work)
{
	struct bch_fs *c =
		container_of(work, struct bch_fs, ec_stripe_delete_work);
	ssize_t idx;

	while (1) {
		spin_lock(&c->ec_stripes_heap_lock);
		idx = stripe_idx_to_delete(c);
		if (idx < 0) {
			spin_unlock(&c->ec_stripes_heap_lock);
			break;
		}

		bch2_stripes_heap_del(c, genradix_ptr(&c->stripes[0], idx), idx);
		spin_unlock(&c->ec_stripes_heap_lock);

		if (ec_stripe_delete(c, idx))
			break;
	}
}

/* stripe creation: */

static int ec_stripe_bkey_insert(struct bch_fs *c,
				 struct bkey_i_stripe *stripe,
				 struct disk_reservation *res)
{
	struct btree_trans trans;
	struct btree_iter *iter;
	struct bkey_s_c k;
	struct bpos start_pos = POS(0, c->ec_stripe_hint);
	int ret;

	bch2_trans_init(&trans, c, 0, 0);
retry:
	bch2_trans_begin(&trans);

	for_each_btree_key(&trans, iter, BTREE_ID_EC, start_pos,
			   BTREE_ITER_SLOTS|BTREE_ITER_INTENT, k, ret) {
		if (bkey_cmp(k.k->p, POS(0, U32_MAX)) > 0) {
			if (start_pos.offset) {
				start_pos = POS_MIN;
				bch2_btree_iter_set_pos(iter, start_pos);
				continue;
			}

			ret = -ENOSPC;
			break;
		}

		if (bkey_deleted(k.k))
			goto found_slot;
	}

	goto err;
found_slot:
	start_pos = iter->pos;

	ret = ec_stripe_mem_alloc(c, iter);
	if (ret)
		goto err;

	stripe->k.p = iter->pos;

	bch2_trans_update(&trans, iter, &stripe->k_i, 0);

	ret = bch2_trans_commit(&trans, res, NULL,
				BTREE_INSERT_NOFAIL);
err:
	bch2_trans_iter_put(&trans, iter);

	if (ret == -EINTR)
		goto retry;

	c->ec_stripe_hint = ret ? start_pos.offset : start_pos.offset + 1;
	bch2_trans_exit(&trans);

	return ret;
}

static int ec_stripe_bkey_update(struct btree_trans *trans,
				 struct bkey_i_stripe *new)
{
	struct bch_fs *c = trans->c;
	struct btree_iter *iter;
	struct bkey_s_c k;
	const struct bch_stripe *existing;
	unsigned i;
	int ret;

	iter = bch2_trans_get_iter(trans, BTREE_ID_EC,
				   new->k.p, BTREE_ITER_INTENT);
	k = bch2_btree_iter_peek_slot(iter);
	ret = bkey_err(k);
	if (ret)
		goto err;

	if (!k.k || k.k->type != KEY_TYPE_stripe) {
		bch_err(c, "error updating stripe: not found");
		ret = -ENOENT;
		goto err;
	}

	existing = bkey_s_c_to_stripe(k).v;

	if (existing->nr_blocks != new->v.nr_blocks) {
		bch_err(c, "error updating stripe: nr_blocks does not match");
		ret = -EINVAL;
		goto err;
	}

	for (i = 0; i < new->v.nr_blocks; i++)
		stripe_blockcount_set(&new->v, i,
			stripe_blockcount_get(existing, i));

	bch2_trans_update(trans, iter, &new->k_i, 0);
err:
	bch2_trans_iter_put(trans, iter);
	return ret;
}

static void extent_stripe_ptr_add(struct bkey_s_extent e,
				  struct ec_stripe_buf *s,
				  struct bch_extent_ptr *ptr,
				  unsigned block)
{
	struct bch_extent_stripe_ptr *dst = (void *) ptr;
	union bch_extent_entry *end = extent_entry_last(e);

	memmove_u64s_up(dst + 1, dst, (u64 *) end - (u64 *) dst);
	e.k->u64s += sizeof(*dst) / sizeof(u64);

	*dst = (struct bch_extent_stripe_ptr) {
		.type = 1 << BCH_EXTENT_ENTRY_stripe_ptr,
		.block		= block,
		.idx		= s->key.k.p.offset,
	};
}

static int ec_stripe_update_ptrs(struct bch_fs *c,
				 struct ec_stripe_buf *s,
				 struct bkey *pos)
{
	struct btree_trans trans;
	struct btree_iter *iter;
	struct bkey_s_c k;
	struct bkey_s_extent e;
	struct bkey_buf sk;
	int ret = 0, dev, block;

	bch2_bkey_buf_init(&sk);
	bch2_trans_init(&trans, c, BTREE_ITER_MAX, 0);

	/* XXX this doesn't support the reflink btree */

	iter = bch2_trans_get_iter(&trans, BTREE_ID_EXTENTS,
				   bkey_start_pos(pos),
				   BTREE_ITER_INTENT);

	while ((k = bch2_btree_iter_peek(iter)).k &&
	       !(ret = bkey_err(k)) &&
	       bkey_cmp(bkey_start_pos(k.k), pos->p) < 0) {
		struct bch_extent_ptr *ptr, *ec_ptr = NULL;

		if (extent_has_stripe_ptr(k, s->key.k.p.offset)) {
			bch2_btree_iter_next(iter);
			continue;
		}

		block = bkey_matches_stripe(&s->key.v, k);
		if (block < 0) {
			bch2_btree_iter_next(iter);
			continue;
		}

		dev = s->key.v.ptrs[block].dev;

		bch2_bkey_buf_reassemble(&sk, c, k);
		e = bkey_i_to_s_extent(sk.k);

		bch2_bkey_drop_ptrs(e.s, ptr, ptr->dev != dev);
		ec_ptr = (void *) bch2_bkey_has_device(e.s_c, dev);
		BUG_ON(!ec_ptr);

		extent_stripe_ptr_add(e, s, ec_ptr, block);

		bch2_btree_iter_set_pos(iter, bkey_start_pos(&sk.k->k));
		bch2_trans_update(&trans, iter, sk.k, 0);

		ret = bch2_trans_commit(&trans, NULL, NULL,
					BTREE_INSERT_NOFAIL);
		if (ret == -EINTR)
			ret = 0;
		if (ret)
			break;
	}

	bch2_trans_exit(&trans);
	bch2_bkey_buf_exit(&sk, c);

	return ret;
}

/*
 * data buckets of new stripe all written: create the stripe
 */
static void ec_stripe_create(struct ec_stripe_new *s)
{
	struct bch_fs *c = s->c;
	struct open_bucket *ob;
	struct bkey_i *k;
	struct stripe *m;
	struct bch_stripe *v = &s->new_stripe.key.v;
	unsigned i, nr_data = v->nr_blocks - v->nr_redundant;
	int ret;

	BUG_ON(s->h->s == s);

	closure_sync(&s->iodone);

	if (s->err) {
		if (s->err != -EROFS)
			bch_err(c, "error creating stripe: error writing data buckets");
		goto err;
	}

	if (s->have_existing_stripe) {
		ec_validate_checksums(c, &s->existing_stripe);

		if (ec_do_recov(c, &s->existing_stripe)) {
			bch_err(c, "error creating stripe: error reading existing stripe");
			goto err;
		}

		for (i = 0; i < nr_data; i++)
			if (stripe_blockcount_get(&s->existing_stripe.key.v, i))
				swap(s->new_stripe.data[i],
				     s->existing_stripe.data[i]);

		ec_stripe_buf_exit(&s->existing_stripe);
	}

	BUG_ON(!s->allocated);

	if (!percpu_ref_tryget(&c->writes))
		goto err;

	ec_generate_ec(&s->new_stripe);

	ec_generate_checksums(&s->new_stripe);

	/* write p/q: */
	for (i = nr_data; i < v->nr_blocks; i++)
		ec_block_io(c, &s->new_stripe, REQ_OP_WRITE, i, &s->iodone);
	closure_sync(&s->iodone);

	if (ec_nr_failed(&s->new_stripe)) {
		bch_err(c, "error creating stripe: error writing redundancy buckets");
		goto err_put_writes;
	}

	ret = s->have_existing_stripe
		? bch2_trans_do(c, &s->res, NULL, BTREE_INSERT_NOFAIL,
				ec_stripe_bkey_update(&trans, &s->new_stripe.key))
		: ec_stripe_bkey_insert(c, &s->new_stripe.key, &s->res);
	if (ret) {
		bch_err(c, "error creating stripe: error creating stripe key");
		goto err_put_writes;
	}

	for_each_keylist_key(&s->keys, k) {
		ret = ec_stripe_update_ptrs(c, &s->new_stripe, &k->k);
		if (ret) {
			bch_err(c, "error creating stripe: error %i updating pointers", ret);
			break;
		}
	}

	spin_lock(&c->ec_stripes_heap_lock);
	m = genradix_ptr(&c->stripes[0], s->new_stripe.key.k.p.offset);

	BUG_ON(m->on_heap);
	bch2_stripes_heap_insert(c, m, s->new_stripe.key.k.p.offset);
	spin_unlock(&c->ec_stripes_heap_lock);
err_put_writes:
	percpu_ref_put(&c->writes);
err:
	bch2_disk_reservation_put(c, &s->res);

	for (i = 0; i < v->nr_blocks; i++)
		if (s->blocks[i]) {
			ob = c->open_buckets + s->blocks[i];

			if (i < nr_data) {
				ob->ec = NULL;
				__bch2_open_bucket_put(c, ob);
			} else {
				bch2_open_bucket_put(c, ob);
			}
		}

	bch2_keylist_free(&s->keys, s->inline_keys);

	ec_stripe_buf_exit(&s->existing_stripe);
	ec_stripe_buf_exit(&s->new_stripe);
	closure_debug_destroy(&s->iodone);
	kfree(s);
}

static void ec_stripe_create_work(struct work_struct *work)
{
	struct bch_fs *c = container_of(work,
		struct bch_fs, ec_stripe_create_work);
	struct ec_stripe_new *s, *n;
restart:
	mutex_lock(&c->ec_stripe_new_lock);
	list_for_each_entry_safe(s, n, &c->ec_stripe_new_list, list)
		if (!atomic_read(&s->pin)) {
			list_del(&s->list);
			mutex_unlock(&c->ec_stripe_new_lock);
			ec_stripe_create(s);
			goto restart;
		}
	mutex_unlock(&c->ec_stripe_new_lock);
}

static void ec_stripe_new_put(struct bch_fs *c, struct ec_stripe_new *s)
{
	BUG_ON(atomic_read(&s->pin) <= 0);

	if (atomic_dec_and_test(&s->pin)) {
		BUG_ON(!s->pending);
		queue_work(system_long_wq, &c->ec_stripe_create_work);
	}
}

static void ec_stripe_set_pending(struct bch_fs *c, struct ec_stripe_head *h)
{
	struct ec_stripe_new *s = h->s;

	BUG_ON(!s->allocated && !s->err);

	h->s		= NULL;
	s->pending	= true;

	mutex_lock(&c->ec_stripe_new_lock);
	list_add(&s->list, &c->ec_stripe_new_list);
	mutex_unlock(&c->ec_stripe_new_lock);

	ec_stripe_new_put(c, s);
}

/* have a full bucket - hand it off to be erasure coded: */
void bch2_ec_bucket_written(struct bch_fs *c, struct open_bucket *ob)
{
	struct ec_stripe_new *s = ob->ec;

	if (ob->sectors_free)
		s->err = -1;

	ec_stripe_new_put(c, s);
}

void bch2_ec_bucket_cancel(struct bch_fs *c, struct open_bucket *ob)
{
	struct ec_stripe_new *s = ob->ec;

	s->err = -EIO;
}

void *bch2_writepoint_ec_buf(struct bch_fs *c, struct write_point *wp)
{
	struct open_bucket *ob = ec_open_bucket(c, &wp->ptrs);
	struct bch_dev *ca;
	unsigned offset;

	if (!ob)
		return NULL;

	ca	= bch_dev_bkey_exists(c, ob->ptr.dev);
	offset	= ca->mi.bucket_size - ob->sectors_free;

	return ob->ec->new_stripe.data[ob->ec_idx] + (offset << 9);
}

void bch2_ec_add_backpointer(struct bch_fs *c, struct write_point *wp,
			     struct bpos pos, unsigned sectors)
{
	struct open_bucket *ob = ec_open_bucket(c, &wp->ptrs);
	struct ec_stripe_new *ec;

	if (!ob)
		return;

	//pr_info("adding backpointer at %llu:%llu", pos.inode, pos.offset);

	ec = ob->ec;
	mutex_lock(&ec->lock);

	if (bch2_keylist_realloc(&ec->keys, ec->inline_keys,
				 ARRAY_SIZE(ec->inline_keys),
				 BKEY_U64s)) {
		BUG();
	}

	bkey_init(&ec->keys.top->k);
	ec->keys.top->k.p	= pos;
	bch2_key_resize(&ec->keys.top->k, sectors);
	bch2_keylist_push(&ec->keys);

	mutex_unlock(&ec->lock);
}

static int unsigned_cmp(const void *_l, const void *_r)
{
	unsigned l = *((const unsigned *) _l);
	unsigned r = *((const unsigned *) _r);

	return cmp_int(l, r);
}

/* pick most common bucket size: */
static unsigned pick_blocksize(struct bch_fs *c,
			       struct bch_devs_mask *devs)
{
	struct bch_dev *ca;
	unsigned i, nr = 0, sizes[BCH_SB_MEMBERS_MAX];
	struct {
		unsigned nr, size;
	} cur = { 0, 0 }, best = { 0, 0 };

	for_each_member_device_rcu(ca, c, i, devs)
		sizes[nr++] = ca->mi.bucket_size;

	sort(sizes, nr, sizeof(unsigned), unsigned_cmp, NULL);

	for (i = 0; i < nr; i++) {
		if (sizes[i] != cur.size) {
			if (cur.nr > best.nr)
				best = cur;

			cur.nr = 0;
			cur.size = sizes[i];
		}

		cur.nr++;
	}

	if (cur.nr > best.nr)
		best = cur;

	return best.size;
}

static bool may_create_new_stripe(struct bch_fs *c)
{
	return false;
}

static void ec_stripe_key_init(struct bch_fs *c,
			       struct bkey_i_stripe *s,
			       unsigned nr_data,
			       unsigned nr_parity,
			       unsigned stripe_size)
{
	unsigned u64s;

	bkey_stripe_init(&s->k_i);
	s->v.sectors			= cpu_to_le16(stripe_size);
	s->v.algorithm			= 0;
	s->v.nr_blocks			= nr_data + nr_parity;
	s->v.nr_redundant		= nr_parity;
	s->v.csum_granularity_bits	= ilog2(c->sb.encoded_extent_max);
	s->v.csum_type			= BCH_CSUM_CRC32C;
	s->v.pad			= 0;

	while ((u64s = stripe_val_u64s(&s->v)) > BKEY_VAL_U64s_MAX) {
		BUG_ON(1 << s->v.csum_granularity_bits >=
		       le16_to_cpu(s->v.sectors) ||
		       s->v.csum_granularity_bits == U8_MAX);
		s->v.csum_granularity_bits++;
	}

	set_bkey_val_u64s(&s->k, u64s);
}

static int ec_new_stripe_alloc(struct bch_fs *c, struct ec_stripe_head *h)
{
	struct ec_stripe_new *s;

	lockdep_assert_held(&h->lock);

	s = kzalloc(sizeof(*s), GFP_KERNEL);
	if (!s)
		return -ENOMEM;

	mutex_init(&s->lock);
	closure_init(&s->iodone, NULL);
	atomic_set(&s->pin, 1);
	s->c		= c;
	s->h		= h;
	s->nr_data	= min_t(unsigned, h->nr_active_devs,
				BCH_BKEY_PTRS_MAX) - h->redundancy;
	s->nr_parity	= h->redundancy;

	bch2_keylist_init(&s->keys, s->inline_keys);

	ec_stripe_key_init(c, &s->new_stripe.key, s->nr_data,
			   s->nr_parity, h->blocksize);

	h->s = s;
	return 0;
}

static struct ec_stripe_head *
ec_new_stripe_head_alloc(struct bch_fs *c, unsigned target,
			 unsigned algo, unsigned redundancy,
			 bool copygc)
{
	struct ec_stripe_head *h;
	struct bch_dev *ca;
	unsigned i;

	h = kzalloc(sizeof(*h), GFP_KERNEL);
	if (!h)
		return NULL;

	mutex_init(&h->lock);
	mutex_lock(&h->lock);

	h->target	= target;
	h->algo		= algo;
	h->redundancy	= redundancy;
	h->copygc	= copygc;

	rcu_read_lock();
	h->devs = target_rw_devs(c, BCH_DATA_user, target);

	for_each_member_device_rcu(ca, c, i, &h->devs)
		if (!ca->mi.durability)
			__clear_bit(i, h->devs.d);

	h->blocksize = pick_blocksize(c, &h->devs);

	for_each_member_device_rcu(ca, c, i, &h->devs)
		if (ca->mi.bucket_size == h->blocksize)
			h->nr_active_devs++;

	rcu_read_unlock();
	list_add(&h->list, &c->ec_stripe_head_list);
	return h;
}

void bch2_ec_stripe_head_put(struct bch_fs *c, struct ec_stripe_head *h)
{
	if (h->s &&
	    h->s->allocated &&
	    bitmap_weight(h->s->blocks_allocated,
			  h->s->nr_data) == h->s->nr_data)
		ec_stripe_set_pending(c, h);

	mutex_unlock(&h->lock);
}

struct ec_stripe_head *__bch2_ec_stripe_head_get(struct bch_fs *c,
						 unsigned target,
						 unsigned algo,
						 unsigned redundancy,
						 bool copygc)
{
	struct ec_stripe_head *h;

	if (!redundancy)
		return NULL;

	mutex_lock(&c->ec_stripe_head_lock);
	list_for_each_entry(h, &c->ec_stripe_head_list, list)
		if (h->target		== target &&
		    h->algo		== algo &&
		    h->redundancy	== redundancy &&
		    h->copygc		== copygc) {
			mutex_lock(&h->lock);
			goto found;
		}

	h = ec_new_stripe_head_alloc(c, target, algo, redundancy, copygc);
found:
	mutex_unlock(&c->ec_stripe_head_lock);
	return h;
}

static enum bucket_alloc_ret
new_stripe_alloc_buckets(struct bch_fs *c, struct ec_stripe_head *h,
			 struct closure *cl)
{
	struct bch_devs_mask devs = h->devs;
	struct open_bucket *ob;
	struct open_buckets buckets;
	unsigned i, j, nr_have_parity = 0, nr_have_data = 0;
	bool have_cache = true;
	enum bucket_alloc_ret ret = ALLOC_SUCCESS;

	for (i = 0; i < h->s->new_stripe.key.v.nr_blocks; i++) {
		if (test_bit(i, h->s->blocks_gotten)) {
			__clear_bit(h->s->new_stripe.key.v.ptrs[i].dev, devs.d);
			if (i < h->s->nr_data)
				nr_have_data++;
			else
				nr_have_parity++;
		}
	}

	BUG_ON(nr_have_data	> h->s->nr_data);
	BUG_ON(nr_have_parity	> h->s->nr_parity);

	percpu_down_read(&c->mark_lock);
	rcu_read_lock();

	buckets.nr = 0;
	if (nr_have_parity < h->s->nr_parity) {
		ret = bch2_bucket_alloc_set(c, &buckets,
					    &h->parity_stripe,
					    &devs,
					    h->s->nr_parity,
					    &nr_have_parity,
					    &have_cache,
					    h->copygc
					    ? RESERVE_MOVINGGC
					    : RESERVE_NONE,
					    0,
					    cl);

		open_bucket_for_each(c, &buckets, ob, i) {
			j = find_next_zero_bit(h->s->blocks_gotten,
					       h->s->nr_data + h->s->nr_parity,
					       h->s->nr_data);
			BUG_ON(j >= h->s->nr_data + h->s->nr_parity);

			h->s->blocks[j] = buckets.v[i];
			h->s->new_stripe.key.v.ptrs[j] = ob->ptr;
			__set_bit(j, h->s->blocks_gotten);
		}

		if (ret)
			goto err;
	}

	buckets.nr = 0;
	if (nr_have_data < h->s->nr_data) {
		ret = bch2_bucket_alloc_set(c, &buckets,
					    &h->block_stripe,
					    &devs,
					    h->s->nr_data,
					    &nr_have_data,
					    &have_cache,
					    h->copygc
					    ? RESERVE_MOVINGGC
					    : RESERVE_NONE,
					    0,
					    cl);

		open_bucket_for_each(c, &buckets, ob, i) {
			j = find_next_zero_bit(h->s->blocks_gotten,
					       h->s->nr_data, 0);
			BUG_ON(j >= h->s->nr_data);

			h->s->blocks[j] = buckets.v[i];
			h->s->new_stripe.key.v.ptrs[j] = ob->ptr;
			__set_bit(j, h->s->blocks_gotten);
		}

		if (ret)
			goto err;
	}
err:
	rcu_read_unlock();
	percpu_up_read(&c->mark_lock);
	return ret;
}

/* XXX: doesn't obey target: */
static s64 get_existing_stripe(struct bch_fs *c,
			       struct ec_stripe_head *head)
{
	ec_stripes_heap *h = &c->ec_stripes_heap;
	struct stripe *m;
	size_t heap_idx;
	u64 stripe_idx;

	if (may_create_new_stripe(c))
		return -1;

	spin_lock(&c->ec_stripes_heap_lock);
	for (heap_idx = 0; heap_idx < h->used; heap_idx++) {
		if (!h->data[heap_idx].blocks_nonempty)
			continue;

		stripe_idx = h->data[heap_idx].idx;
		m = genradix_ptr(&c->stripes[0], stripe_idx);

		if (m->algorithm	== head->algo &&
		    m->nr_redundant	== head->redundancy &&
		    m->sectors		== head->blocksize &&
		    m->blocks_nonempty	< m->nr_blocks - m->nr_redundant) {
			bch2_stripes_heap_del(c, m, stripe_idx);
			spin_unlock(&c->ec_stripes_heap_lock);
			return stripe_idx;
		}
	}

	spin_unlock(&c->ec_stripes_heap_lock);
	return -1;
}

struct ec_stripe_head *bch2_ec_stripe_head_get(struct bch_fs *c,
					       unsigned target,
					       unsigned algo,
					       unsigned redundancy,
					       bool copygc,
					       struct closure *cl)
{
	struct ec_stripe_head *h;
	unsigned i;
	s64 idx;
	int ret;

	h = __bch2_ec_stripe_head_get(c, target, algo, redundancy, copygc);
	if (!h) {
		bch_err(c, "no stripe head");
		return NULL;
	}

	if (!h->s) {
		if (ec_new_stripe_alloc(c, h)) {
			bch2_ec_stripe_head_put(c, h);
			bch_err(c, "failed to allocate new stripe");
			return NULL;
		}

		idx = get_existing_stripe(c, h);
		if (idx >= 0) {
			h->s->have_existing_stripe = true;
			ret = get_stripe_key(c, idx, &h->s->existing_stripe);
			if (ret) {
				bch2_fs_fatal_error(c, "error reading stripe key: %i", ret);
				bch2_ec_stripe_head_put(c, h);
				return NULL;
			}

			if (ec_stripe_buf_init(&h->s->existing_stripe, 0, h->blocksize)) {
				/*
				 * this is a problem: we have deleted from the
				 * stripes heap already
				 */
				BUG();
			}

			BUG_ON(h->s->existing_stripe.size != h->blocksize);
			BUG_ON(h->s->existing_stripe.size != h->s->existing_stripe.key.v.sectors);

			for (i = 0; i < h->s->existing_stripe.key.v.nr_blocks; i++) {
				if (stripe_blockcount_get(&h->s->existing_stripe.key.v, i)) {
					__set_bit(i, h->s->blocks_gotten);
					__set_bit(i, h->s->blocks_allocated);
				}

				ec_block_io(c, &h->s->existing_stripe, READ, i, &h->s->iodone);
			}

			bkey_copy(&h->s->new_stripe.key.k_i,
				  &h->s->existing_stripe.key.k_i);
		}

		if (ec_stripe_buf_init(&h->s->new_stripe, 0, h->blocksize)) {
			BUG();
		}
	}

	if (!h->s->allocated) {
		if (!h->s->have_existing_stripe &&
		    !h->s->res.sectors) {
			ret = bch2_disk_reservation_get(c, &h->s->res,
					h->blocksize,
					h->s->nr_parity, 0);
			if (ret) {
				/*
				 * This means we need to wait for copygc to
				 * empty out buckets from existing stripes:
				 */
				bch2_ec_stripe_head_put(c, h);
				h = NULL;
				goto out;
			}
		}

		ret = new_stripe_alloc_buckets(c, h, cl);
		if (ret) {
			bch2_ec_stripe_head_put(c, h);
			h = ERR_PTR(-ret);
			goto out;
		}

		h->s->allocated = true;
	}
out:
	return h;
}

void bch2_ec_stop_dev(struct bch_fs *c, struct bch_dev *ca)
{
	struct ec_stripe_head *h;
	struct open_bucket *ob;
	unsigned i;

	mutex_lock(&c->ec_stripe_head_lock);
	list_for_each_entry(h, &c->ec_stripe_head_list, list) {

		mutex_lock(&h->lock);
		if (!h->s)
			goto unlock;

		for (i = 0; i < h->s->new_stripe.key.v.nr_blocks; i++) {
			if (!h->s->blocks[i])
				continue;

			ob = c->open_buckets + h->s->blocks[i];
			if (ob->ptr.dev == ca->dev_idx)
				goto found;
		}
		goto unlock;
found:
		h->s->err = -EROFS;
		ec_stripe_set_pending(c, h);
unlock:
		mutex_unlock(&h->lock);
	}
	mutex_unlock(&c->ec_stripe_head_lock);
}

void bch2_stripes_heap_start(struct bch_fs *c)
{
	struct genradix_iter iter;
	struct stripe *m;

	genradix_for_each(&c->stripes[0], iter, m)
		if (m->alive)
			bch2_stripes_heap_insert(c, m, iter.pos);
}

static int __bch2_stripe_write_key(struct btree_trans *trans,
				   struct btree_iter *iter,
				   struct stripe *m,
				   size_t idx,
				   struct bkey_i_stripe *new_key)
{
	const struct bch_stripe *v;
	struct bkey_s_c k;
	unsigned i;
	int ret;

	bch2_btree_iter_set_pos(iter, POS(0, idx));

	k = bch2_btree_iter_peek_slot(iter);
	ret = bkey_err(k);
	if (ret)
		return ret;

	if (k.k->type != KEY_TYPE_stripe)
		return -EIO;

	v = bkey_s_c_to_stripe(k).v;
	for (i = 0; i < v->nr_blocks; i++)
		if (m->block_sectors[i] != stripe_blockcount_get(v, i))
			goto write;
	return 0;
write:
	bkey_reassemble(&new_key->k_i, k);

	for (i = 0; i < new_key->v.nr_blocks; i++)
		stripe_blockcount_set(&new_key->v, i,
				      m->block_sectors[i]);

	bch2_trans_update(trans, iter, &new_key->k_i, 0);
	return 0;
}

int bch2_stripes_write(struct bch_fs *c, unsigned flags)
{
	struct btree_trans trans;
	struct btree_iter *iter;
	struct genradix_iter giter;
	struct bkey_i_stripe *new_key;
	struct stripe *m;
	int ret = 0;

	new_key = kmalloc(255 * sizeof(u64), GFP_KERNEL);
	BUG_ON(!new_key);

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

	iter = bch2_trans_get_iter(&trans, BTREE_ID_EC, POS_MIN,
				   BTREE_ITER_SLOTS|BTREE_ITER_INTENT);

	genradix_for_each(&c->stripes[0], giter, m) {
		if (!m->alive)
			continue;

		ret = __bch2_trans_do(&trans, NULL, NULL,
				      BTREE_INSERT_NOFAIL|flags,
			__bch2_stripe_write_key(&trans, iter, m,
					giter.pos, new_key));

		if (ret)
			break;
	}

	bch2_trans_exit(&trans);

	kfree(new_key);

	return ret;
}

static int bch2_stripes_read_fn(struct bch_fs *c, enum btree_id id,
			      unsigned level, struct bkey_s_c k)
{
	int ret = 0;

	if (k.k->type == KEY_TYPE_stripe) {
		ret = __ec_stripe_mem_alloc(c, k.k->p.offset, GFP_KERNEL) ?:
			bch2_mark_key(c, k, 0, 0, NULL, 0,
				      BTREE_TRIGGER_NOATOMIC);
		if (ret)
			return ret;
	}

	return ret;
}

int bch2_stripes_read(struct bch_fs *c, struct journal_keys *journal_keys)
{
	int ret = bch2_btree_and_journal_walk(c, journal_keys, BTREE_ID_EC,
					  NULL, bch2_stripes_read_fn);
	if (ret)
		bch_err(c, "error reading stripes: %i", ret);

	return ret;
}

int bch2_ec_mem_alloc(struct bch_fs *c, bool gc)
{
	struct btree_trans trans;
	struct btree_iter *iter;
	struct bkey_s_c k;
	size_t i, idx = 0;
	int ret = 0;

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

	iter = bch2_trans_get_iter(&trans, BTREE_ID_EC, POS(0, U64_MAX), 0);

	k = bch2_btree_iter_prev(iter);
	if (!IS_ERR_OR_NULL(k.k))
		idx = k.k->p.offset + 1;
	ret = bch2_trans_exit(&trans);
	if (ret)
		return ret;

	if (!idx)
		return 0;

	if (!gc &&
	    !init_heap(&c->ec_stripes_heap, roundup_pow_of_two(idx),
		       GFP_KERNEL))
		return -ENOMEM;
#if 0
	ret = genradix_prealloc(&c->stripes[gc], idx, GFP_KERNEL);
#else
	for (i = 0; i < idx; i++)
		if (!genradix_ptr_alloc(&c->stripes[gc], i, GFP_KERNEL))
			return -ENOMEM;
#endif
	return 0;
}

void bch2_stripes_heap_to_text(struct printbuf *out, struct bch_fs *c)
{
	ec_stripes_heap *h = &c->ec_stripes_heap;
	struct stripe *m;
	size_t i;

	spin_lock(&c->ec_stripes_heap_lock);
	for (i = 0; i < min_t(size_t, h->used, 20); i++) {
		m = genradix_ptr(&c->stripes[0], h->data[i].idx);

		pr_buf(out, "%zu %u/%u+%u\n", h->data[i].idx,
		       h->data[i].blocks_nonempty,
		       m->nr_blocks - m->nr_redundant,
		       m->nr_redundant);
	}
	spin_unlock(&c->ec_stripes_heap_lock);
}

void bch2_new_stripes_to_text(struct printbuf *out, struct bch_fs *c)
{
	struct ec_stripe_head *h;
	struct ec_stripe_new *s;

	mutex_lock(&c->ec_stripe_head_lock);
	list_for_each_entry(h, &c->ec_stripe_head_list, list) {
		pr_buf(out, "target %u algo %u redundancy %u:\n",
		       h->target, h->algo, h->redundancy);

		if (h->s)
			pr_buf(out, "\tpending: blocks %u+%u allocated %u\n",
			       h->s->nr_data, h->s->nr_parity,
			       bitmap_weight(h->s->blocks_allocated,
					     h->s->nr_data));
	}
	mutex_unlock(&c->ec_stripe_head_lock);

	mutex_lock(&c->ec_stripe_new_lock);
	list_for_each_entry(s, &c->ec_stripe_new_list, list) {
		pr_buf(out, "\tin flight: blocks %u+%u pin %u\n",
		       s->nr_data, s->nr_parity,
		       atomic_read(&s->pin));
	}
	mutex_unlock(&c->ec_stripe_new_lock);
}

void bch2_fs_ec_exit(struct bch_fs *c)
{
	struct ec_stripe_head *h;

	while (1) {
		mutex_lock(&c->ec_stripe_head_lock);
		h = list_first_entry_or_null(&c->ec_stripe_head_list,
					     struct ec_stripe_head, list);
		if (h)
			list_del(&h->list);
		mutex_unlock(&c->ec_stripe_head_lock);
		if (!h)
			break;

		BUG_ON(h->s);
		kfree(h);
	}

	BUG_ON(!list_empty(&c->ec_stripe_new_list));

	free_heap(&c->ec_stripes_heap);
	genradix_free(&c->stripes[0]);
	bioset_exit(&c->ec_bioset);
}

int bch2_fs_ec_init(struct bch_fs *c)
{
	INIT_WORK(&c->ec_stripe_create_work, ec_stripe_create_work);
	INIT_WORK(&c->ec_stripe_delete_work, ec_stripe_delete_work);

	return bioset_init(&c->ec_bioset, 1, offsetof(struct ec_bio, bio),
			   BIOSET_NEED_BVECS);
}