// SPDX-License-Identifier: GPL-2.0
/*
 * Code for moving data off a device.
 */

#include "bcachefs.h"

#include "alloc/backpointers.h"
#include "alloc/buckets.h"
#include "alloc/replicas.h"

#include "btree/bkey_buf.h"
#include "btree/update.h"
#include "btree/interior.h"
#include "btree/write_buffer.h"

#include "data/ec/init.h"
#include "data/extents.h"
#include "data/write.h"
#include "data/keylist.h"
#include "data/migrate.h"
#include "data/move.h"
#include "data/reconcile/trigger.h"

#include "journal/journal.h"

#include "sb/io.h"

#include "init/progress.h"

static struct bkey_i *drop_dev_ptrs(struct btree_trans *trans, struct bkey_s_c k, unsigned dev_idx,
				    unsigned flags, struct printbuf *err)
{
	struct bch_fs *c = trans->c;
	bool metadata = bkey_is_btree_ptr(k.k);
	unsigned replicas = metadata ? c->opts.metadata_replicas : c->opts.data_replicas;
	unsigned lost = metadata ? BCH_FORCE_IF_METADATA_LOST : BCH_FORCE_IF_DATA_LOST;
	unsigned degraded = metadata ? BCH_FORCE_IF_METADATA_DEGRADED : BCH_FORCE_IF_DATA_DEGRADED;

	if (!bch2_bkey_has_device_c(c, k, dev_idx))
		return NULL;

	unsigned n_buf_u64s = metadata
		? BKEY_BTREE_PTR_U64s_MAX
		: BKEY_EXTENT_U64s_MAX;
	struct bkey_i *n = bch2_trans_kmalloc(trans, n_buf_u64s * sizeof(u64));
	if (IS_ERR(n))
		return n;
	bkey_reassemble(n, k);

	bch2_bkey_drop_device(c, bkey_i_to_s(n), dev_idx);

	struct bkey_durability durability;
	int ret = bch2_bkey_durability(trans, bkey_i_to_s_c(n), &durability);
	if (ret)
		return ERR_PTR(ret);

	if ((!durability.total && !(flags & lost)) ||
	    (durability.total < replicas && !(flags & degraded))) {
		prt_str(err, "cannot drop device without degrading/losing data\n  ");
		bch2_bkey_val_to_text(err, c, k);
		prt_newline(err);
		return ERR_PTR(bch_err_throw(c, remove_would_lose_data));
	}

	if (bch2_bkey_can_read(c, bkey_i_to_s_c(n))) {
		struct bch_inode_opts opts;
		int ret = bch2_bkey_get_io_opts(trans, NULL, k, &opts) ?:
			  bch2_bkey_set_needs_reconcile(trans, NULL, &opts, bkey_i_to_s(n),
							n_buf_u64s,
							SET_NEEDS_RECONCILE_opt_change, 0);
		if (ret)
			return ERR_PTR(ret);
	} else if (!metadata) {
		bch2_set_bkey_error(c, n, KEY_TYPE_ERROR_device_removed);
	}

	return n;
}

static int drop_btree_ptrs(struct btree_trans *trans, struct btree_iter *iter,
			   struct btree *b, unsigned dev_idx,
			   unsigned flags, struct printbuf *err)
{
	struct bkey_i *n = errptr_try(drop_dev_ptrs(trans, bkey_i_to_s_c(&b->key), dev_idx, flags, err));
	if (!n)
		return 0;

	return bch2_btree_node_update_key(trans, iter, b, n, 0, false);
}

static int bch2_dev_usrdata_drop_key(struct btree_trans *trans,
				     struct btree_iter *iter,
				     struct bkey_s_c k,
				     unsigned dev_idx,
				     unsigned flags, struct printbuf *err)
{
	struct bkey_i *n = errptr_try(drop_dev_ptrs(trans, k, dev_idx, flags, err));
	if (!n)
		return 0;

	/*
	 * Since we're not inserting through an extent iterator
	 * (BTREE_ITER_all_snapshots iterators aren't extent iterators),
	 * we aren't using the extent overwrite path to delete, we're
	 * just using the normal key deletion path:
	 */
	if (bkey_deleted(&n->k))
		n->k.size = 0;
	return bch2_trans_update(trans, iter, n, BTREE_UPDATE_internal_snapshot_node);
}

static int bch2_dev_btree_drop_key(struct btree_trans *trans,
				   struct bkey_s_c_backpointer bp,
				   unsigned dev_idx,
				   struct wb_maybe_flush *last_flushed,
				   unsigned flags, struct printbuf *err)
{
	CLASS(btree_iter_uninit, iter)(trans);
	struct btree *b = bch2_backpointer_get_node(trans, bp, &iter, last_flushed);
	int ret = PTR_ERR_OR_ZERO(b);
	if (ret)
		return ret == -BCH_ERR_backpointer_to_overwritten_btree_node ? 0 : ret;

	return drop_btree_ptrs(trans, &iter, b, dev_idx, flags, err);
}

static int bch2_dev_usrdata_drop(struct bch_fs *c,
				 struct progress_indicator *progress,
				 unsigned dev_idx,
				 unsigned flags, struct printbuf *err)
{
	CLASS(btree_trans, trans)(c);
	CLASS(disk_reservation, res)(c);

	/* FIXME: this does not handle unknown btrees with data pointers */
	for (unsigned id = 0; id < BTREE_ID_NR; id++) {
		if (!btree_type_has_data_ptrs(id))
			continue;

		/* Stripe keys have pointers, but are handled separately */
		if (id == BTREE_ID_stripes)
			continue;

		try(for_each_btree_key_commit(trans, iter, id, POS_MIN,
				BTREE_ITER_prefetch|BTREE_ITER_all_snapshots, k,
				&res.r, NULL, BCH_TRANS_COMMIT_no_enospc, ({
			bch2_disk_reservation_put(c, &res.r);
			bch2_progress_update_iter(trans, progress, &iter) ?:
			bch2_dev_usrdata_drop_key(trans, &iter, k, dev_idx, flags, err);
		})));
	}

	return 0;
}

static int bch2_dev_metadata_drop(struct bch_fs *c,
				  struct progress_indicator *progress,
				  unsigned dev_idx,
				  unsigned flags, struct printbuf *err)
{
	/* don't handle this yet: */
	if (flags & BCH_FORCE_IF_METADATA_LOST)
		return bch_err_throw(c, remove_with_metadata_missing_unimplemented);

	CLASS(btree_trans, trans)(c);

	for (unsigned btree = 0; btree < btree_id_nr_alive(c); btree++)
		for (unsigned level = 0; level < BTREE_MAX_DEPTH; level++)
			try(for_each_btree_node(trans, iter, btree, POS_MIN, level, 0, b, ({
				bch2_progress_update_iter(trans, progress, &iter) ?:
				drop_btree_ptrs(trans, &iter, b, dev_idx, flags, err);
			})));

	bch2_trans_unlock(trans);
	bch2_btree_interior_updates_flush(c);
	return 0;
}

static int data_drop_bp(struct btree_trans *trans, unsigned dev_idx,
			struct bkey_s_c_backpointer bp, struct wb_maybe_flush *last_flushed,
			unsigned flags, struct printbuf *err, bool *had_open_stripe)
{
	CLASS(btree_iter_uninit, iter)(trans);
	struct bkey_s_c k = bch2_backpointer_get_key(trans, bp, &iter, BTREE_ITER_intent,
						     last_flushed);
	int ret = bkey_err(k);
	if (ret == -BCH_ERR_backpointer_to_overwritten_btree_node)
		return 0;
	if (ret)
		return ret;

	if (!k.k || !bch2_bkey_has_device_c(trans->c, k, dev_idx))
		return 0;

	/*
	 * XXX: pass flags arg to invalidate_stripe_to_dev and handle it
	 * properly
	 */

	if (bkey_is_btree_ptr(k.k))
		return bch2_dev_btree_drop_key(trans, bp, dev_idx, last_flushed, flags, err);
	else if (k.k->type == KEY_TYPE_stripe)
		return bch2_invalidate_stripe_to_dev(trans, &iter, k, dev_idx, flags, err,
						     had_open_stripe);
	else
		return bch2_dev_usrdata_drop_key(trans, &iter, k, dev_idx, flags, err);
}

static u64 dev_data_buckets(struct bch_dev *ca)
{
	struct bch_dev_usage usage = bch2_dev_usage_read(ca);
	u64 nr = 0;
	for (unsigned i = 0; i < BCH_DATA_NR; i++)
		if (!data_type_is_empty(i) && !data_type_is_hidden(i))
			nr += usage.buckets[i];

	return nr;
}

int bch2_dev_data_drop_by_backpointers(struct bch_fs *c, struct bch_dev *ca,
				       unsigned flags, struct printbuf *err)
{
	unsigned dev_idx = ca->dev_idx;

	CLASS(btree_trans, trans)(c);

	struct wb_maybe_flush last_flushed __cleanup(wb_maybe_flush_exit);
	wb_maybe_flush_init(&last_flushed);

	struct progress_indicator progress;
	bch2_progress_init(&progress, "dropping device data", c,
			   BIT(BTREE_ID_backpointers), 0);

	/*
	 * Backpointers on RO devices may be updated (primarily via reconcile),
	 * even when we're not updating the data on those devices (e.g.
	 * propagating pending/hipri bits); stripe reshape — which deletes the
	 * old stripe and writes a new one at a different stripe index — can
	 * also drop a backpointer for an extant ptr-to-dev and re-add it
	 * outside the scan's already-walked range. Both create races with the
	 * scan that can only be handled by retrying.
	 */
	/*
	 * Terminate on progress, not a fixed iteration count. An EC evacuation
	 * off a failing device can take many scan/flush cycles to drain: the
	 * migration creates that move data off the device are deliberately not
	 * fenced (see "Fence stripe creates against device removal"), so they
	 * run concurrently with the scan as open stripes that we skip and flush.
	 * A fixed cap fires mid-migration. Instead, track the device's data and
	 * keep going as long as it keeps hitting new lows - that's forward
	 * progress. Only bail after max_stalled scans in a row with no new low,
	 * which catches a genuine livelock (or a flush that never drains)
	 * without aborting a slow-but-working drain.
	 */
	const unsigned max_stalled = 10;
	u64 min_data_buckets = U64_MAX;
	unsigned nr_stalled = 0;

	while (true) {
		bool had_open_stripe = false;

		try(bch2_btree_write_buffer_flush_sync(trans));

		try(backpointer_scan_for_each(trans, iter, BTREE_ID_backpointers,
					      POS(dev_idx, 0), POS(dev_idx, U64_MAX),
						  &last_flushed, &progress, bp, ({
			wb_maybe_flush_inc(&last_flushed);
			CLASS(disk_reservation, res)(c);
			data_drop_bp(trans, dev_idx, bp, &last_flushed, flags, err,
				     &had_open_stripe) ?:
			bch2_trans_commit(trans, &res.r, NULL, BCH_TRANS_COMMIT_no_enospc);
		})));

		u64 data_buckets = dev_data_buckets(ca);
		if (!data_buckets)
			return 0;

		if (data_buckets < min_data_buckets) {
			min_data_buckets = data_buckets;
			nr_stalled = 0;
		} else if (++nr_stalled >= max_stalled) {
			prt_printf(err, "%s(): no progress after %u scans, %llu data buckets remain\n",
				   __func__, nr_stalled, data_buckets);
			return bch_err_throw(c, remove_by_backpointer_did_not_terminate);
		}

		/*
		 * Skipped open stripes are owned by in-flight stripe creates;
		 * wait for those to close before rescanning so the next scan can
		 * invalidate them. The flush isn't itself counted as progress: if
		 * it never drains, the stall counter still terminates us.
		 */
		if (had_open_stripe) {
			bch2_trans_unlock(trans);
			bch2_fs_ec_flush_outstanding(c);
		}
	}
}

int bch2_dev_data_drop(struct bch_fs *c, unsigned dev_idx,
		       unsigned flags, struct printbuf *err)
{
	struct progress_indicator progress;
	bch2_progress_init(&progress, "dropping user data", c,
			   btree_has_data_ptrs_mask & ~BIT_ULL(BTREE_ID_stripes), 0);

	try(bch2_dev_usrdata_drop(c, &progress, dev_idx, flags, err));

	bch2_progress_init(&progress, "dropping metadata", c, ~0ULL, ~0ULL);

	return bch2_dev_metadata_drop(c, &progress, dev_idx, flags, err);
}
