fs/bcachefs/rebalance.c - third_party/linux - Git at Google

 // 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 "io_write.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_commit_do(c, NULL, NULL,
 				       BCH_TRANS_COMMIT_no_enospc|
 				       BCH_TRANS_COMMIT_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, BCH_TRANS_COMMIT_no_enospc);
 }

 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;
 	data_opts->write_flags		|= BCH_WRITE_ONLY_SPECIFIED_DEVS;

 	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;
 	}

 	if (trace_rebalance_extent_enabled()) {
 		struct printbuf buf = PRINTBUF;

 		prt_str(&buf, "target=");
 		bch2_target_to_text(&buf, c, r->target);
 		prt_str(&buf, " compression=");
 		bch2_compression_opt_to_text(&buf, r->compression);
 		prt_str(&buf, " ");
 		bch2_bkey_val_to_text(&buf, c, k);

 		trace_rebalance_extent(c, buf.buf);
 		printbuf_exit(&buf);
 	}

 	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	= background_compression(*io_opts);
 	} else {
 		const struct bch_extent_rebalance *r = bch2_bkey_rebalance_opts(k);

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

 	data_opts->rewrite_ptrs		= bch2_bkey_ptrs_need_rebalance(c, k, target, compression);
 	data_opts->target		= target;
 	data_opts->write_flags		|= BCH_WRITE_ONLY_SPECIFIED_DEVS;
 	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, BCH_TRANS_COMMIT_no_enospc,
 			  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_trans_begin(trans);

 	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;

 	set_freezable();

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

 	while (!kthread_should_stop() && !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) << 9);
 		prt_newline(out);

 		prt_str(out, "io wait remaining: ");
 		bch2_prt_human_readable_s64(out, (r->wait_iotime_end - now) << 9);
 		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);
 	bch_err_msg(c, ret, "creating rebalance thread");
 	if (ret)
 		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);
 }
	// 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 "io_write.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_commit_do(c, NULL, NULL,
	BCH_TRANS_COMMIT_no_enospc\|
	BCH_TRANS_COMMIT_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, BCH_TRANS_COMMIT_no_enospc);
	}

	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;
	data_opts->write_flags \|= BCH_WRITE_ONLY_SPECIFIED_DEVS;

	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;
	}

	if (trace_rebalance_extent_enabled()) {
	struct printbuf buf = PRINTBUF;

	prt_str(&buf, "target=");
	bch2_target_to_text(&buf, c, r->target);
	prt_str(&buf, " compression=");
	bch2_compression_opt_to_text(&buf, r->compression);
	prt_str(&buf, " ");
	bch2_bkey_val_to_text(&buf, c, k);

	trace_rebalance_extent(c, buf.buf);
	printbuf_exit(&buf);
	}

	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 = background_compression(*io_opts);
	} else {
	const struct bch_extent_rebalance *r = bch2_bkey_rebalance_opts(k);

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

	data_opts->rewrite_ptrs = bch2_bkey_ptrs_need_rebalance(c, k, target, compression);
	data_opts->target = target;
	data_opts->write_flags \|= BCH_WRITE_ONLY_SPECIFIED_DEVS;
	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, BCH_TRANS_COMMIT_no_enospc,
	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_trans_begin(trans);

	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;

	set_freezable();

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

	while (!kthread_should_stop() && !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) << 9);
	prt_newline(out);

	prt_str(out, "io wait remaining: ");
	bch2_prt_human_readable_s64(out, (r->wait_iotime_end - now) << 9);
	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);
	bch_err_msg(c, ret, "creating rebalance thread");
	if (ret)
	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);
	}