// SPDX-License-Identifier: GPL-2.0

#include "bcachefs.h"
#include "alloc_background.h"
#include "alloc_foreground.h"
#include "btree_iter.h"
#include "btree_update.h"
#include "btree_write_buffer.h"
#include "buckets.h"
#include "clock.h"
#include "compress.h"
#include "disk_groups.h"
#include "errcode.h"
#include "error.h"
#include "inode.h"
#include "move.h"
#include "rebalance.h"
#include "subvolume.h"
#include "super-io.h"
#include "trace.h"

#include <linux/freezer.h>
#include <linux/kthread.h>
#include <linux/sched/cputime.h>

#define REBALANCE_WORK_SCAN_OFFSET	(U64_MAX - 1)

static const char * const bch2_rebalance_state_strs[] = {
#define x(t) #t,
	BCH_REBALANCE_STATES()
	NULL
#undef x
};

static int __bch2_set_rebalance_needs_scan(struct btree_trans *trans, u64 inum)
{
	struct btree_iter iter;
	struct bkey_s_c k;
	struct bkey_i_cookie *cookie;
	u64 v;
	int ret;

	bch2_trans_iter_init(trans, &iter, BTREE_ID_rebalance_work,
			     SPOS(inum, REBALANCE_WORK_SCAN_OFFSET, U32_MAX),
			     BTREE_ITER_INTENT);
	k = bch2_btree_iter_peek_slot(&iter);
	ret = bkey_err(k);
	if (ret)
		goto err;

	v = k.k->type == KEY_TYPE_cookie
		? le64_to_cpu(bkey_s_c_to_cookie(k).v->cookie)
		: 0;

	cookie = bch2_trans_kmalloc(trans, sizeof(*cookie));
	ret = PTR_ERR_OR_ZERO(cookie);
	if (ret)
		goto err;

	bkey_cookie_init(&cookie->k_i);
	cookie->k.p = iter.pos;
	cookie->v.cookie = cpu_to_le64(v + 1);

	ret = bch2_trans_update(trans, &iter, &cookie->k_i, 0);
err:
	bch2_trans_iter_exit(trans, &iter);
	return ret;
}

int bch2_set_rebalance_needs_scan(struct bch_fs *c, u64 inum)
{
	int ret = bch2_trans_do(c, NULL, NULL, BTREE_INSERT_NOFAIL|BTREE_INSERT_LAZY_RW,
			    __bch2_set_rebalance_needs_scan(trans, inum));
	rebalance_wakeup(c);
	return ret;
}

int bch2_set_fs_needs_rebalance(struct bch_fs *c)
{
	return bch2_set_rebalance_needs_scan(c, 0);
}

static int bch2_clear_rebalance_needs_scan(struct btree_trans *trans, u64 inum, u64 cookie)
{
	struct btree_iter iter;
	struct bkey_s_c k;
	u64 v;
	int ret;

	bch2_trans_iter_init(trans, &iter, BTREE_ID_rebalance_work,
			     SPOS(inum, REBALANCE_WORK_SCAN_OFFSET, U32_MAX),
			     BTREE_ITER_INTENT);
	k = bch2_btree_iter_peek_slot(&iter);
	ret = bkey_err(k);
	if (ret)
		goto err;

	v = k.k->type == KEY_TYPE_cookie
		? le64_to_cpu(bkey_s_c_to_cookie(k).v->cookie)
		: 0;

	if (v == cookie)
		ret = bch2_btree_delete_at(trans, &iter, 0);
err:
	bch2_trans_iter_exit(trans, &iter);
	return ret;
}

static struct bkey_s_c next_rebalance_entry(struct btree_trans *trans,
					    struct btree_iter *work_iter)
{
	return !kthread_should_stop()
		? bch2_btree_iter_peek(work_iter)
		: bkey_s_c_null;
}

static int bch2_bkey_clear_needs_rebalance(struct btree_trans *trans,
					   struct btree_iter *iter,
					   struct bkey_s_c k)
{
	struct bkey_i *n = bch2_bkey_make_mut(trans, iter, &k, 0);
	int ret = PTR_ERR_OR_ZERO(n);
	if (ret)
		return ret;

	extent_entry_drop(bkey_i_to_s(n),
			  (void *) bch2_bkey_rebalance_opts(bkey_i_to_s_c(n)));
	return bch2_trans_commit(trans, NULL, NULL, BTREE_INSERT_NOFAIL);
}

static struct bkey_s_c next_rebalance_extent(struct btree_trans *trans,
			struct bpos work_pos,
			struct btree_iter *extent_iter,
			struct data_update_opts *data_opts)
{
	struct bch_fs *c = trans->c;
	struct bkey_s_c k;

	bch2_trans_iter_exit(trans, extent_iter);
	bch2_trans_iter_init(trans, extent_iter,
			     work_pos.inode ? BTREE_ID_extents : BTREE_ID_reflink,
			     work_pos,
			     BTREE_ITER_ALL_SNAPSHOTS);
	k = bch2_btree_iter_peek_slot(extent_iter);
	if (bkey_err(k))
		return k;

	const struct bch_extent_rebalance *r = k.k ? bch2_bkey_rebalance_opts(k) : NULL;
	if (!r) {
		/* raced due to btree write buffer, nothing to do */
		return bkey_s_c_null;
	}

	memset(data_opts, 0, sizeof(*data_opts));

	data_opts->rewrite_ptrs		=
		bch2_bkey_ptrs_need_rebalance(c, k, r->target, r->compression);
	data_opts->target		= r->target;

	if (!data_opts->rewrite_ptrs) {
		/*
		 * device we would want to write to offline? devices in target
		 * changed?
		 *
		 * We'll now need a full scan before this extent is picked up
		 * again:
		 */
		int ret = bch2_bkey_clear_needs_rebalance(trans, extent_iter, k);
		if (ret)
			return bkey_s_c_err(ret);
		return bkey_s_c_null;
	}

	return k;
}

noinline_for_stack
static int do_rebalance_extent(struct moving_context *ctxt,
			       struct bpos work_pos,
			       struct btree_iter *extent_iter)
{
	struct btree_trans *trans = ctxt->trans;
	struct bch_fs *c = trans->c;
	struct bch_fs_rebalance *r = &trans->c->rebalance;
	struct data_update_opts data_opts;
	struct bch_io_opts io_opts;
	struct bkey_s_c k;
	struct bkey_buf sk;
	int ret;

	ctxt->stats = &r->work_stats;
	r->state = BCH_REBALANCE_working;

	bch2_bkey_buf_init(&sk);

	ret = bkey_err(k = next_rebalance_extent(trans, work_pos,
						 extent_iter, &data_opts));
	if (ret || !k.k)
		goto out;

	ret = bch2_move_get_io_opts_one(trans, &io_opts, k);
	if (ret)
		goto out;

	atomic64_add(k.k->size, &ctxt->stats->sectors_seen);

	/*
	 * The iterator gets unlocked by __bch2_read_extent - need to
	 * save a copy of @k elsewhere:
	 */
	bch2_bkey_buf_reassemble(&sk, c, k);
	k = bkey_i_to_s_c(sk.k);

	ret = bch2_move_extent(ctxt, NULL, extent_iter, k, io_opts, data_opts);
	if (ret) {
		if (bch2_err_matches(ret, ENOMEM)) {
			/* memory allocation failure, wait for some IO to finish */
			bch2_move_ctxt_wait_for_io(ctxt);
			ret = -BCH_ERR_transaction_restart_nested;
		}

		if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
			goto out;

		/* skip it and continue, XXX signal failure */
		ret = 0;
	}
out:
	bch2_bkey_buf_exit(&sk, c);
	return ret;
}

static bool rebalance_pred(struct bch_fs *c, void *arg,
			   struct bkey_s_c k,
			   struct bch_io_opts *io_opts,
			   struct data_update_opts *data_opts)
{
	unsigned target, compression;

	if (k.k->p.inode) {
		target		= io_opts->background_target;
		compression	= io_opts->background_compression ?: io_opts->compression;
	} else {
		const struct bch_extent_rebalance *r = bch2_bkey_rebalance_opts(k);

		target		= r ? r->target : io_opts->background_target;
		compression	= r ? r->compression :
			(io_opts->background_compression ?: io_opts->compression);
	}

	data_opts->rewrite_ptrs		= bch2_bkey_ptrs_need_rebalance(c, k, target, compression);
	data_opts->target		= target;
	return data_opts->rewrite_ptrs != 0;
}

static int do_rebalance_scan(struct moving_context *ctxt, u64 inum, u64 cookie)
{
	struct btree_trans *trans = ctxt->trans;
	struct bch_fs_rebalance *r = &trans->c->rebalance;
	int ret;

	bch2_move_stats_init(&r->scan_stats, "rebalance_scan");
	ctxt->stats = &r->scan_stats;

	if (!inum) {
		r->scan_start	= BBPOS_MIN;
		r->scan_end	= BBPOS_MAX;
	} else {
		r->scan_start	= BBPOS(BTREE_ID_extents, POS(inum, 0));
		r->scan_end	= BBPOS(BTREE_ID_extents, POS(inum, U64_MAX));
	}

	r->state = BCH_REBALANCE_scanning;

	ret = __bch2_move_data(ctxt, r->scan_start, r->scan_end, rebalance_pred, NULL) ?:
		commit_do(trans, NULL, NULL, BTREE_INSERT_NOFAIL,
			  bch2_clear_rebalance_needs_scan(trans, inum, cookie));

	bch2_move_stats_exit(&r->scan_stats, trans->c);
	return ret;
}

static void rebalance_wait(struct bch_fs *c)
{
	struct bch_fs_rebalance *r = &c->rebalance;
	struct io_clock *clock = &c->io_clock[WRITE];
	u64 now = atomic64_read(&clock->now);
	u64 min_member_capacity = bch2_min_rw_member_capacity(c);

	if (min_member_capacity == U64_MAX)
		min_member_capacity = 128 * 2048;

	r->wait_iotime_end		= now + (min_member_capacity >> 6);

	if (r->state != BCH_REBALANCE_waiting) {
		r->wait_iotime_start	= now;
		r->wait_wallclock_start	= ktime_get_real_ns();
		r->state		= BCH_REBALANCE_waiting;
	}

	bch2_kthread_io_clock_wait(clock, r->wait_iotime_end, MAX_SCHEDULE_TIMEOUT);
}

static int do_rebalance(struct moving_context *ctxt)
{
	struct btree_trans *trans = ctxt->trans;
	struct bch_fs *c = trans->c;
	struct bch_fs_rebalance *r = &c->rebalance;
	struct btree_iter rebalance_work_iter, extent_iter = { NULL };
	struct bkey_s_c k;
	int ret = 0;

	bch2_move_stats_init(&r->work_stats, "rebalance_work");
	bch2_move_stats_init(&r->scan_stats, "rebalance_scan");

	bch2_trans_iter_init(trans, &rebalance_work_iter,
			     BTREE_ID_rebalance_work, POS_MIN,
			     BTREE_ITER_ALL_SNAPSHOTS);

	while (!bch2_move_ratelimit(ctxt)) {
		if (!r->enabled) {
			bch2_moving_ctxt_flush_all(ctxt);
			kthread_wait_freezable(r->enabled ||
					       kthread_should_stop());
		}

		if (kthread_should_stop())
			break;

		bch2_trans_begin(trans);

		ret = bkey_err(k = next_rebalance_entry(trans, &rebalance_work_iter));
		if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
			continue;
		if (ret || !k.k)
			break;

		ret = k.k->type == KEY_TYPE_cookie
			? do_rebalance_scan(ctxt, k.k->p.inode,
					    le64_to_cpu(bkey_s_c_to_cookie(k).v->cookie))
			: do_rebalance_extent(ctxt, k.k->p, &extent_iter);

		if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
			continue;
		if (ret)
			break;

		bch2_btree_iter_advance(&rebalance_work_iter);
	}

	bch2_trans_iter_exit(trans, &extent_iter);
	bch2_trans_iter_exit(trans, &rebalance_work_iter);
	bch2_move_stats_exit(&r->scan_stats, c);

	if (!ret &&
	    !kthread_should_stop() &&
	    !atomic64_read(&r->work_stats.sectors_seen) &&
	    !atomic64_read(&r->scan_stats.sectors_seen)) {
		bch2_moving_ctxt_flush_all(ctxt);
		bch2_trans_unlock_long(trans);
		rebalance_wait(c);
	}

	if (!bch2_err_matches(ret, EROFS))
		bch_err_fn(c, ret);
	return ret;
}

static int bch2_rebalance_thread(void *arg)
{
	struct bch_fs *c = arg;
	struct bch_fs_rebalance *r = &c->rebalance;
	struct moving_context ctxt;
	int ret;

	set_freezable();

	bch2_moving_ctxt_init(&ctxt, c, NULL, &r->work_stats,
			      writepoint_ptr(&c->rebalance_write_point),
			      true);

	while (!kthread_should_stop() &&
	       !(ret = do_rebalance(&ctxt)))
		;

	bch2_moving_ctxt_exit(&ctxt);

	return 0;
}

void bch2_rebalance_status_to_text(struct printbuf *out, struct bch_fs *c)
{
	struct bch_fs_rebalance *r = &c->rebalance;

	prt_str(out, bch2_rebalance_state_strs[r->state]);
	prt_newline(out);
	printbuf_indent_add(out, 2);

	switch (r->state) {
	case BCH_REBALANCE_waiting: {
		u64 now = atomic64_read(&c->io_clock[WRITE].now);

		prt_str(out, "io wait duration:  ");
		bch2_prt_human_readable_s64(out, r->wait_iotime_end - r->wait_iotime_start);
		prt_newline(out);

		prt_str(out, "io wait remaining: ");
		bch2_prt_human_readable_s64(out, r->wait_iotime_end - now);
		prt_newline(out);

		prt_str(out, "duration waited:   ");
		bch2_pr_time_units(out, ktime_get_real_ns() - r->wait_wallclock_start);
		prt_newline(out);
		break;
	}
	case BCH_REBALANCE_working:
		bch2_move_stats_to_text(out, &r->work_stats);
		break;
	case BCH_REBALANCE_scanning:
		bch2_move_stats_to_text(out, &r->scan_stats);
		break;
	}
	prt_newline(out);
	printbuf_indent_sub(out, 2);
}

void bch2_rebalance_stop(struct bch_fs *c)
{
	struct task_struct *p;

	c->rebalance.pd.rate.rate = UINT_MAX;
	bch2_ratelimit_reset(&c->rebalance.pd.rate);

	p = rcu_dereference_protected(c->rebalance.thread, 1);
	c->rebalance.thread = NULL;

	if (p) {
		/* for sychronizing with rebalance_wakeup() */
		synchronize_rcu();

		kthread_stop(p);
		put_task_struct(p);
	}
}

int bch2_rebalance_start(struct bch_fs *c)
{
	struct task_struct *p;
	int ret;

	if (c->rebalance.thread)
		return 0;

	if (c->opts.nochanges)
		return 0;

	p = kthread_create(bch2_rebalance_thread, c, "bch-rebalance/%s", c->name);
	ret = PTR_ERR_OR_ZERO(p);
	if (ret) {
		bch_err_msg(c, ret, "creating rebalance thread");
		return ret;
	}

	get_task_struct(p);
	rcu_assign_pointer(c->rebalance.thread, p);
	wake_up_process(p);
	return 0;
}

void bch2_fs_rebalance_init(struct bch_fs *c)
{
	bch2_pd_controller_init(&c->rebalance.pd);
}