// SPDX-License-Identifier: GPL-2.0
/*
 * bcachefs setup/teardown code, and some metadata io - read a superblock and
 * figure out what to do with it.
 *
 * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
 * Copyright 2012 Google, Inc.
 */

#include "bcachefs.h"

#include "alloc/backpointers.h"
#include "alloc/discard.h"
#include "alloc/disk_groups.h"
#include "alloc/foreground.h"
#include "alloc/replicas.h"

#include "btree/check.h"
#include "btree/journal_overlay.h"
#include "btree/init.h"
#include "btree/interior.h"
#include "btree/key_cache.h"
#include "btree/locking.h"
#include "btree/read.h"
#include "btree/write.h"
#include "btree/write_buffer.h"

#include "data/checksum.h"
#include "data/compress.h"
#include "data/copygc.h"
#include "data/ec/create.h"
#include "data/ec/init.h"
#include "data/move.h"
#include "data/nocow_locking.h"
#include "data/read.h"
#include "data/reconcile/work.h"
#include "data/write.h"

#ifdef CONFIG_DEBUG_FS
#include "debug/async_objs.h"
#endif
#include "debug/debug.h"
#include "debug/sysfs.h"

#include "fs/check.h"
#include "fs/dirent.h"
#include "fs/inode.h"
#include "fs/quota.h"

#include "init/chardev.h"
#include "init/dev.h"
#include "init/error.h"
#include "init/recovery.h"
#include "init/passes.h"
#include "init/fs.h"

#include "journal/init.h"
#include "journal/journal.h"
#include "journal/reclaim.h"
#include "journal/seq_blacklist.h"

#include "sb/clean.h"
#include "sb/counters.h"
#include "sb/downgrade.h"
#include "sb/errors.h"
#include "sb/io.h"
#include "sb/members.h"

#include "snapshots/snapshot.h"
#include "snapshots/subvolume.h"

#include "vfs/fs.h"
#include "vfs/io.h"
#include "vfs/buffered.h"
#include "vfs/direct.h"

#include "util/clock.h"
#include "util/enumerated_ref.h"
#include "util/thread_with_file.h"

#include <linux/backing-dev.h>
#include <linux/blkdev.h>
#include <linux/debugfs.h>
#include <linux/device.h>
#include <linux/idr.h>
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/random.h>
#include <linux/sysfs.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Kent Overstreet <kent.overstreet@gmail.com>");
MODULE_DESCRIPTION("bcachefs filesystem");

#define x(n)		#n,
const char * const bch2_fs_flag_strs[] = {
	BCH_FS_FLAGS()
	NULL
};

const char * const bch2_write_refs[] = {
	BCH_WRITE_REFS()
	NULL
};
#undef x

static int kern_soh_to_loglevel(const char *fmt)
{
	if (fmt[0] == KERN_SOH[0] &&
	    fmt[1] >= '0' && fmt[1] <= '9')
		return fmt[1] - '0';
	else
		return -1;
}

static unsigned loglevel_opt(struct bch_fs *c)
{
	return c->loglevel ?: c->opts.verbose ? 7: 6;
}

void bch2_print_str_loglevel(struct bch_fs *c, int loglevel, const char *str)
{
	unsigned len = strlen(str);
	/*
	 * printbufs leave extra spaces from indent level after the last
	 * newline; strip them
	 */
	unsigned l = len;
	while (l && str[l - 1] == ' ')
		--l;
	if (!l || str[l - 1] == '\n')
		len = l;
	if (!len)
		return;

	if (loglevel < 0)
		loglevel = c->prev_loglevel;
	else
		c->prev_loglevel = loglevel;

	if (loglevel > loglevel_opt(c))
		return;

#ifdef __KERNEL__
	static const char *prefixes[] = {
		KERN_SOH "0",
		KERN_SOH "1",
		KERN_SOH "2",
		KERN_SOH "3",
		KERN_SOH "4",
		KERN_SOH "5",
		KERN_SOH "6",
		KERN_SOH "7",
	};
	const char *prefix = loglevel < ARRAY_SIZE(prefixes) ? prefixes[loglevel] : KERN_SOH;
#else
	const char *prefix = "";
#endif

#ifdef __KERNEL__
	struct stdio_redirect *stdio = bch2_fs_stdio_redirect_log(c);

	if (unlikely(stdio)) {
		bch2_stdio_redirect_write(stdio, true, str, len);
		return;
	}
#endif
	bch2_print_string_as_lines(prefix, str);
}

void bch2_print_str(struct bch_fs *c, const char *prefix, const char *str)
{
	/* Nothing to print? Nothing to do: */
	if (!str)
		return;

	bch2_print_str_loglevel(c, kern_soh_to_loglevel(prefix), str);
}

void bch2_print_str_user(struct bch_fs *c, const char *str)
{
	if (!str)
		return;

#ifdef __KERNEL__
	struct stdio_redirect *stdio = bch2_fs_stdio_redirect_user(c);

	if (unlikely(stdio)) {
		bch2_stdio_redirect_write(stdio, true, str, strlen(str));
		return;
	}
#endif
	/*
	 * Can't double-write: bch2_print_str() reaches a redirect only through
	 * bch2_fs_stdio_redirect_log(), which is NULL in every case that got here.
	 */
	bch2_print_str(c, KERN_ERR, str);
}

__printf(2, 0)
static void bch2_print_maybe_redirect(struct stdio_redirect *stdio, const char *fmt, va_list args)
{
#ifdef __KERNEL__
	if (unlikely(stdio)) {
		if (fmt[0] == KERN_SOH[0])
			fmt += 2;

		bch2_stdio_redirect_vprintf(stdio, true, fmt, args);
		return;
	}
#endif
	vprintk(fmt, args);
}

void bch2_print_opts(struct bch_opts *opts, const char *fmt, ...)
{
	struct stdio_redirect *stdio = (void *)(unsigned long)opts->stdio;

	va_list args;
	va_start(args, fmt);
	bch2_print_maybe_redirect(stdio, fmt, args);
	va_end(args);
}

void __bch2_print(struct bch_fs *c, const char *fmt, ...)
{
	int loglevel = kern_soh_to_loglevel(fmt);
	if (loglevel < 0)
		loglevel = c->prev_loglevel;
	else
		c->prev_loglevel = loglevel;

	if (loglevel > loglevel_opt(c))
		return;

#ifndef __KERNEL__
	if (fmt[0] == KERN_SOH[0])
		fmt += 2;
#endif

	struct stdio_redirect *stdio = bch2_fs_stdio_redirect_log(c);

	va_list args;
	va_start(args, fmt);
	bch2_print_maybe_redirect(stdio, fmt, args);
	va_end(args);
}

static void bch2_fs_release(struct kobject *);
static void bch2_fs_counters_release(struct kobject *k)
{
}

static void bch2_fs_internal_release(struct kobject *k)
{
}

static void bch2_fs_opts_dir_release(struct kobject *k)
{
}

static void bch2_fs_time_stats_release(struct kobject *k)
{
}

static void bch2_fs_time_stats_json_release(struct kobject *k)
{
}

static struct attribute *bcachefs_files[] = {
	NULL
};

static void bcachefs_release(struct kobject *k)
{
}

static const struct sysfs_ops bcachefs_sysfs_ops = {};

KTYPE(bcachefs);
KTYPE(bch2_fs);
KTYPE(bch2_fs_counters);
KTYPE(bch2_fs_internal);
KTYPE(bch2_fs_opts_dir);
KTYPE(bch2_fs_time_stats);
KTYPE(bch2_fs_time_stats_json);

static struct kobject bcachefs_kobj;

static DECLARE_WAIT_QUEUE_HEAD(bch2_read_only_wait);

LIST_HEAD(bch2_fs_list);
DEFINE_MUTEX(bch2_fs_list_lock);

static bool bch2_fs_will_resize_on_mount(struct bch_fs *);

struct bch_fs *__bch2_uuid_to_fs(__uuid_t uuid)
{
	struct bch_fs *c;

	lockdep_assert_held(&bch2_fs_list_lock);

	list_for_each_entry(c, &bch2_fs_list, list)
		if (!memcmp(&c->disk_sb.sb->uuid, &uuid, sizeof(uuid)))
			return c;

	return NULL;
}

struct bch_fs *bch2_uuid_to_fs(__uuid_t uuid)
{
	guard(mutex)(&bch2_fs_list_lock);

	struct bch_fs *c = __bch2_uuid_to_fs(uuid);
	if (c)
		closure_get(&c->cl);
	return c;
}

/* Filesystem RO/RW: */

/*
 * For startup/shutdown of RW stuff, the dependencies are:
 *
 * - foreground writes depend on copygc and rebalance (to free up space)
 *
 * - copygc and rebalance depend on mark and sweep gc (they actually probably
 *   don't because they either reserve ahead of time or don't block if
 *   allocations fail, but allocations can require mark and sweep gc to run
 *   because of generation number wraparound)
 *
 * - all of the above depends on the allocator threads
 *
 * - allocator depends on the journal (when it rewrites prios and gens)
 */

static void __bch2_fs_read_only(struct bch_fs *c)
{
	unsigned clean_passes = 0;
	u64 seq = 0;

	bch2_maybe_schedule_btree_bitmap_gc_stop(c);
	bch2_fs_ec_stop(c);
	bch2_open_buckets_stop(c, NULL, true);
	bch2_copygc_stop(c);
	bch2_btree_write_buffer_stop(c);
	bch2_fs_ec_flush(c);
	cancel_delayed_work_sync(&c->maybe_schedule_btree_bitmap_gc);

	bch_verbose(c, "flushing journal and stopping allocators, journal seq %llu",
		    journal_cur_seq(&c->journal));

	do {
		clean_passes++;

		bch2_do_discards_going_ro(c);

		if (bch2_btree_write_buffer_flush_going_ro(c) ||
		    bch2_btree_key_cache_flush_going_ro(c) ||
		    bch2_btree_interior_updates_flush(c) ||
		    bch2_journal_flush_all_pins(&c->journal) ||
		    bch2_btree_flush_all_writes(c) ||
		    seq != atomic64_read(&c->journal.seq)) {
			seq = atomic64_read(&c->journal.seq);
			clean_passes = 0;
		}
	} while (clean_passes < 2);

	/*
	 * On a dead journal the clean-shutdown loop above can't make dirty
	 * btree nodes clean: journal_flush_all_pins doesn't push them out,
	 * and __bch2_btree_node_write skips submission for journal_error, so
	 * BTREE_NODE_dirty stays set on every node that hadn't been written
	 * yet. The loop terminates (everything no-ops) but live[].dirty is
	 * still populated. Force-cancel: drop dirty bits + transition DIRTY →
	 * CLEAN, then drain any interior updates btree_node_write_update_key
	 * may have kicked off before the journal died.
	 */
	if (bch2_journal_error(&c->journal)) {
		bch2_btree_cancel_all_writes(c);
		bch2_btree_interior_updates_flush(c);
	}

	bch_verbose(c, "flushing journal and stopping allocators complete, journal seq %llu",
		    journal_cur_seq(&c->journal));

	if (test_bit(JOURNAL_replay_done, &c->journal.flags) &&
	    !test_bit(BCH_FS_emergency_ro, &c->flags))
		set_bit(BCH_FS_clean_shutdown, &c->flags);

	bch2_fs_journal_stop(&c->journal);

	bch_info(c, "%sclean shutdown complete, journal seq %llu",
		 test_bit(BCH_FS_clean_shutdown, &c->flags) ? "" : "un",
		 c->journal.seq_ondisk);

	/*
	 * After stopping journal:
	 */
	for_each_member_device(c, ca) {
		bch2_dev_io_ref_stop(ca, WRITE);
		bch2_dev_allocator_remove(c, ca);

		/*
		 * Queued from bch2_journal_space_available(); not cancelled
		 * anywhere else on the going-RO path, so cancel it here, after
		 * the journal is stopped, or it can run against a freed device.
		 */
		cancel_work_sync(&ca->journal.discard);
	}
}

static void bch2_writes_disabled(struct enumerated_ref *writes)
{
	struct bch_fs *c = container_of(writes, struct bch_fs, writes);

	set_bit(BCH_FS_write_disable_complete, &c->flags);
	wake_up(&bch2_read_only_wait);
}

void bch2_fs_read_only(struct bch_fs *c)
{
	if (!test_bit(BCH_FS_rw, &c->flags)) {
		bch2_journal_reclaim_stop(&c->journal);
		return;
	}

	BUG_ON(test_bit(BCH_FS_write_disable_complete, &c->flags));

	bch_verbose(c, "going read-only");

	/*
	 * Block new foreground-end write operations from starting - any new
	 * writes will return -EROFS. Set before stopping reconcile so the
	 * reconcile kthread's child workers (which check this flag to break
	 * out) see it while bch2_reconcile_stop() is blocked waiting on them.
	 */
	set_bit(BCH_FS_going_ro, &c->flags);

	/*
	 * Stop background kthreads that issue writes (reconcile, etc.)
	 * before disabling c->writes; otherwise they can dispatch
	 * data_update operations that fail with erofs_no_writes once
	 * c->writes is stopped, and the failure-rate threshold trips.
	 */
	bch2_reconcile_stop(c);

	enumerated_ref_stop_async(&c->writes);

	/*
	 * If we're not doing an emergency shutdown, we want to wait on
	 * outstanding writes to complete so they don't see spurious errors due
	 * to shutting down the allocator:
	 *
	 * If we are doing an emergency shutdown outstanding writes may
	 * hang until we shutdown the allocator so we don't want to wait
	 * on outstanding writes before shutting everything down - but
	 * we do need to wait on them before returning and signalling
	 * that going RO is complete:
	 */
	wait_event(bch2_read_only_wait,
		   test_bit(BCH_FS_write_disable_complete, &c->flags) ||
		   test_bit(BCH_FS_emergency_ro, &c->flags));

	bool writes_disabled = test_bit(BCH_FS_write_disable_complete, &c->flags);
	if (writes_disabled)
		bch_verbose(c, "finished waiting for writes to stop");

	__bch2_fs_read_only(c);

	wait_event(bch2_read_only_wait,
		   test_bit(BCH_FS_write_disable_complete, &c->flags));

	if (!writes_disabled)
		bch_verbose(c, "finished waiting for writes to stop");

	clear_bit(BCH_FS_write_disable_complete, &c->flags);
	clear_bit(BCH_FS_going_ro, &c->flags);
	clear_bit(BCH_FS_rw, &c->flags);

	if (!bch2_journal_error(&c->journal) &&
	    !test_bit(BCH_FS_error, &c->flags) &&
	    !test_bit(BCH_FS_emergency_ro, &c->flags) &&
	    test_bit(BCH_FS_started, &c->flags) &&
	    test_bit(BCH_FS_clean_shutdown, &c->flags) &&
	    c->recovery.pass_done >= BCH_RECOVERY_PASS_journal_replay) {
		BUG_ON(c->journal.last_empty_seq != journal_cur_seq(&c->journal));
		BUG_ON(!c->sb.clean);
		BUG_ON(c->btree.cache.live[0].nr_dirty || c->btree.cache.live[1].nr_dirty);
		BUG_ON(atomic_long_read(&c->btree.key_cache.nr_dirty));
		for (unsigned i = 0; i < BCH_WB_BTREE_NR; i++) {
			BUG_ON(c->btree.write_buffer[i].inc.keys.nr);
			BUG_ON(c->btree.write_buffer[i].flushing.keys.nr);
		}
		bch2_verify_replicas_refs_clean(c);
		bch2_verify_accounting_clean(c);
	} else {
		/* Make sure error counts/counters are persisted */
		guard(mutex_noio)(&c->sb_lock);
		bch2_write_super(c);

		bch_verbose(c, "done going read-only, filesystem not clean");
	}
}

static void bch2_fs_read_only_work(struct work_struct *work)
{
	struct bch_fs *c =
		container_of(work, struct bch_fs, read_only_work);

	guard(rwsem_write)(&c->state_lock);
	bch2_fs_read_only(c);
}

static void bch2_fs_read_only_async(struct bch_fs *c)
{
	queue_work(system_long_wq, &c->read_only_work);
}

static bool __bch2_fs_emergency_read_only(struct bch_fs *c, struct printbuf *out, bool locked)
{
	bool ret = !test_and_set_bit(BCH_FS_emergency_ro, &c->flags);

	if (!locked)
		bch2_journal_halt(&c->journal);
	else
		bch2_journal_halt_locked(&c->journal);
	bch2_fs_read_only_async(c);
	wake_up(&bch2_read_only_wait);

	/*
	 * Wake threads parked in __bch2_wait_on_allocator: going-RO won't
	 * complete while they hold open closures on freelist_wait, and they
	 * won't otherwise notice the fs is shutting down.
	 */
	bch2_alloc_wake_all(c);

	if (ret) {
		prt_printf(out, "emergency read only at seq %llu\n",
			   journal_cur_seq(&c->journal));
		out->suppress = false;
	}

	return ret;
}

/* Returns true if going ERO, false if we already are */
bool bch2_fs_emergency_read_only(struct bch_fs *c, struct printbuf *out)
{
	return __bch2_fs_emergency_read_only(c, out, false);
}

bool bch2_fs_emergency_read_only_locked(struct bch_fs *c, struct printbuf *out)
{
	return __bch2_fs_emergency_read_only(c, out, true);
}

static int __bch2_fs_read_write(struct bch_fs *c, bool early)
{
	BUG_ON(!test_bit(BCH_FS_may_go_rw, &c->flags));

	if (WARN_ON(c->sb.features & BIT_ULL(BCH_FEATURE_no_alloc_info)))
		return bch_err_throw(c, erofs_no_alloc_info);

	BUG_ON(!test_bit(BCH_FS_may_upgrade_downgrade, &c->flags));

	if (test_bit(BCH_FS_initial_gc_unfixed, &c->flags)) {
		bch_err(c, "cannot go rw, unfixed btree errors");
		return bch_err_throw(c, erofs_unfixed_errors);
	}

	if (c->sb.features & BIT_ULL(BCH_FEATURE_small_image)) {
		bch_err(c, "cannot go rw, filesystem is an unresized image file");
		return bch_err_throw(c, erofs_filesystem_full);
	}

	if (c->sb.features & BIT_ULL(BCH_FEATURE_no_default_sb)) {
		bch_err(c, "cannot go rw, run bcachefs migrate-superblock first");
		return bch_err_throw(c, erofs_sb_not_migrated);
	}

	if (test_bit(BCH_FS_rw, &c->flags))
		return 0;

	bch_info(c, "going read-write");

	try(bch2_fs_init_rw(c));
	try(bch2_sb_members_v2_init(c));

	clear_bit(BCH_FS_clean_shutdown, &c->flags);

	scoped_guard(rcu)
		for_each_online_member_rcu(c, ca)
			if (ca->mi.state == BCH_MEMBER_STATE_rw) {
				bch2_dev_allocator_add(c, ca);
				enumerated_ref_start(&ca->io_ref[WRITE]);
			}

	bch2_recalc_capacity(c);

	/*
	 * First journal write must be a flush write: after a clean shutdown we
	 * don't read the journal, so the first journal write may end up
	 * overwriting whatever was there previously, and there must always be
	 * at least one non-flush write in the journal or recovery will fail:
	 */
	scoped_guard(spinlock, &c->journal.lock) {
		set_bit(JOURNAL_need_flush_write, &c->journal.flags);
		set_bit(JOURNAL_running, &c->journal.flags);
#ifdef CONFIG_BCACHEFS_DEBUG
		c->journal.stop_thread = NULL;
#endif
		bch2_journal_space_available(&c->journal);
	}

	/*
	 * Don't jump to our error path, and call bch2_fs_read_only(), unless we
	 * successfully marked the filesystem dirty
	 */

	set_bit(BCH_FS_rw, &c->flags);
	set_bit(BCH_FS_was_rw, &c->flags);

	if (test_and_clear_bit(BCH_FS_sb_dirty, &c->flags)) {
		guard(mutex_noio)(&c->sb_lock);
		bch2_write_super(c);
	}

	enumerated_ref_start(&c->writes);

	int ret = bch2_journal_reclaim_start(&c->journal) ?:
		  bch2_btree_write_buffer_start(c) ?:
		  bch2_copygc_start(c) ?:
		  (!c->opts.read_only
		   ? bch2_reconcile_start(c)
		   : 0);
	if (ret) {
		bch2_fs_read_only(c);
		return ret;
	}

	bch2_do_discards_async(c);
	bch2_do_invalidates(c);
	bch2_do_stripe_deletes(c);
	bch2_do_pending_node_rewrites(c);
	bch2_scrub_journal_do_repairs(c);
	bch2_maybe_schedule_btree_bitmap_gc(c);
	return 0;
}

int bch2_fs_read_write(struct bch_fs *c)
{
	if (c->opts.recovery_pass_last &&
	    c->opts.recovery_pass_last < BCH_RECOVERY_PASS_journal_replay)
		return bch_err_throw(c, erofs_norecovery);

	if (c->opts.nochanges)
		return bch_err_throw(c, erofs_nochanges);

	if (c->sb.features & BIT_ULL(BCH_FEATURE_no_alloc_info))
		return bch_err_throw(c, erofs_no_alloc_info);

	return __bch2_fs_read_write(c, false);
}

int bch2_fs_read_write_early(struct bch_fs *c)
{
	guard(rwsem_write)(&c->state_lock);
	return __bch2_fs_read_write(c, true);
}

/* Filesystem startup/shutdown: */

static void __bch2_fs_free(struct bch_fs *c)
{
	bch2_journal_keys_put_initial(c);
	BUG_ON(atomic_read(&c->journal_keys.ref));

	for (unsigned i = 0; i < BCH_TIME_STAT_NR; i++)
		bch2_time_stats_exit(&c->times[i]);

#if IS_ENABLED(CONFIG_UNICODE)
	utf8_unload(c->cf_encoding);
#endif

	bch2_reconcile_stop(c);
	bch2_copygc_stop(c);
	bch2_btree_write_buffer_stop(c);
	bch2_free_pending_node_rewrites(c);
	bch2_free_fsck_errs(c);
	bch2_fs_vfs_exit(c);
	bch2_fs_snapshots_exit(c);
	bch2_fs_replicas_exit(c);
	bch2_fs_reconcile_exit(c);
	bch2_fs_quota_exit(c);
	bch2_fs_nocow_locking_exit(c);
	bch2_fs_journal_exit(&c->journal);
	bch2_fs_io_write_exit(c);
	bch2_fs_io_read_exit(c);
	bch2_fs_errors_exit(c);
	bch2_fs_encryption_exit(c);
	bch2_fs_ec_exit(c);
	bch2_fs_discards_exit(c);
	bch2_fs_data_update_exit(c);
	bch2_fs_move_exit(c);
	bch2_fs_counters_exit(c);
	bch2_fs_copygc_exit(c);
	bch2_fs_compress_exit(c);
	bch2_io_clock_exit(&c->io_clock[WRITE]);
	bch2_io_clock_exit(&c->io_clock[READ]);
	bch2_fs_capacity_exit(c);
	bch2_fs_btree_exit(c);
	bch2_fs_accounting_exit(c);

#ifdef CONFIG_DEBUG_FS
	bch2_fs_async_obj_exit(c);
#endif

	enumerated_ref_exit(&c->writes);
	kfree(rcu_dereference_protected(c->disk_groups, 1));
	kfree(c->journal_seq_blacklist_table);

	if (c->promote_wq)
		destroy_workqueue(c->promote_wq);
	if (c->write_ref_wq)
		destroy_workqueue(c->write_ref_wq);
	if (c->btree_update_wq)
		destroy_workqueue(c->btree_update_wq);

	bch2_free_super(&c->disk_sb);
	kvfree(c);
	module_put(THIS_MODULE);
}

static void bch2_fs_release(struct kobject *kobj)
{
	struct bch_fs *c = container_of(kobj, struct bch_fs, kobj);

	__bch2_fs_free(c);
}

int bch2_fs_stop(struct bch_fs *c)
{
	if (!test_and_set_bit(BCH_FS_stopping, &c->flags)) {
		if (test_bit(BCH_FS_started, &c->flags))
			bch_verbose(c, "shutting down");

		scoped_guard(rwsem_write, &c->state_lock)
			bch2_fs_read_only(c);

		for (unsigned i = 0; i < c->sb.nr_devices; i++) {
			struct bch_dev *ca = rcu_dereference_protected(c->devs[i], true);
			if (ca)
				bch2_dev_io_ref_stop(ca, READ);
		}

		for_each_member_device(c, ca)
			bch2_dev_unlink(ca);

		if (c->kobj.state_in_sysfs)
			kobject_del(&c->kobj);

		bch2_fs_debug_exit(c);
		bch2_fs_chardev_exit(c);

		bch2_ro_ref_put(c);
		wait_event(c->ro_ref_wait, !refcount_read(&c->ro_ref));

		kobject_put(&c->counters_kobj);
		kobject_put(&c->time_stats_json);
		kobject_put(&c->time_stats);
		kobject_put(&c->opts_dir);
		if (c->internal.state_in_sysfs)
			sysfs_remove_bin_file(&c->internal, &bin_attr_btree_trans_stats_json);
		kobject_put(&c->internal);

		/* btree prefetch might have kicked off reads in the background: */
		bch2_btree_flush_all_reads(c);


		cancel_work_sync(&c->read_only_work);

		flush_work(&c->btree.interior_updates.work);
	}

	if (test_bit(BCH_FS_emergency_ro, &c->flags))
		return bch_err_throw(c, shutdown_with_emergency_ro);
	if (test_bit(BCH_FS_error, &c->flags))
		return bch_err_throw(c, shutdown_with_errors_unfixed);
	if (test_bit(BCH_FS_errors_fixed, &c->flags))
		return bch_err_throw(c, shutdown_with_errors_fixed);
	return 0;
}

static void bch2_fs_free(struct bch_fs *c)
{
	scoped_guard(mutex, &bch2_fs_list_lock)
		list_del(&c->list);

	closure_sync(&c->cl);
	closure_debug_destroy(&c->cl);

	for (unsigned i = 0; i < c->sb.nr_devices; i++) {
		struct bch_dev *ca = rcu_dereference_protected(c->devs[i], true);

		if (ca) {
			EBUG_ON(atomic_long_read(&ca->ref) != 1);
			bch2_dev_io_ref_stop(ca, READ);
			bch2_free_super(&ca->disk_sb);
			bch2_dev_free(ca);
		}
	}

	bch_verbose(c, "shutdown complete");

	kobject_put(&c->kobj);
}

int bch2_fs_exit(struct bch_fs *c)
{
	int ret = bch2_fs_stop(c);
	bch2_fs_free(c);
	return ret;
}

static int bch2_fs_online(struct bch_fs *c)
{
	lockdep_assert_held(&bch2_fs_list_lock);

	if (c->sb.multi_device &&
	    __bch2_uuid_to_fs(c->sb.uuid))
		return bch_err_throw(c, filesystem_uuid_already_open);

	try(bch2_fs_chardev_init(c));

	bch2_fs_debug_init(c);

	if ((c->sb.multi_device
	     ? kobject_add(&c->kobj, &bcachefs_kobj, "%pU", c->sb.user_uuid.b)
	     : kobject_add(&c->kobj, &bcachefs_kobj, "%s", c->name)) ?:
	    kobject_add(&c->internal, &c->kobj, "internal") ?:
	    kobject_add(&c->opts_dir, &c->kobj, "options") ?:
#ifndef CONFIG_BCACHEFS_NO_LATENCY_ACCT
	    kobject_add(&c->time_stats, &c->kobj, "time_stats") ?:
	    kobject_add(&c->time_stats_json, &c->kobj, "time_stats_json") ?:
#endif
	    kobject_add(&c->counters_kobj, &c->kobj, "counters") ?:
	    bch2_opts_create_sysfs_files(&c->opts_dir, OPT_FS) ?:
	    sysfs_create_bin_file(&c->internal, &bin_attr_btree_trans_stats_json))
		return bch_err_throw(c, sysfs_init_error);

	guard(rwsem_write)(&c->state_lock);

	for_each_member_device(c, ca)
		if (bch2_dev_sysfs_online(c, ca))
			return bch_err_throw(c, sysfs_init_error);

	BUG_ON(!list_empty(&c->list));
	list_add(&c->list, &bch2_fs_list);
	return 0;
}

int bch2_fs_init_rw(struct bch_fs *c)
{
	if (test_bit(BCH_FS_rw_init_done, &c->flags))
		return 0;

	if (!(c->btree_update_wq = alloc_workqueue("bcachefs",
				WQ_HIGHPRI|WQ_FREEZABLE|WQ_MEM_RECLAIM|WQ_UNBOUND, 512)) ||
	    !(c->write_ref_wq = alloc_workqueue("bcachefs_write_ref",
				WQ_FREEZABLE|WQ_PERCPU, 0)) ||
	    !(c->promote_wq = alloc_workqueue("bcachefs_promotes",
				WQ_FREEZABLE|WQ_PERCPU, 2)))
		return bch_err_throw(c, ENOMEM_fs_other_alloc);

	try(bch2_fs_btree_init_rw(c));
	try(bch2_fs_io_write_init(c));
	try(bch2_fs_journal_init_rw(&c->journal));
	try(bch2_fs_vfs_init_rw(c));
	try(bch2_journal_reclaim_start(&c->journal));
	try(bch2_btree_write_buffer_start(c));
	try(bch2_copygc_start(c));
	try(bch2_reconcile_start(c));

	set_bit(BCH_FS_rw_init_done, &c->flags);
	return 0;
}

static bool check_version_upgrade(struct bch_fs *c, struct printbuf *out)
{
	unsigned latest_version	= bcachefs_metadata_version_current;
	unsigned latest_compatible = min(latest_version,
					 bch2_latest_compatible_version(c->sb.version));
	unsigned old_version = c->sb.version_upgrade_complete ?: c->sb.version;
	unsigned new_version = 0;
	bool ret = false;

	if (old_version < bcachefs_metadata_required_upgrade_below) {
		if (c->opts.version_upgrade == BCH_VERSION_UPGRADE_incompatible ||
		    latest_compatible < bcachefs_metadata_required_upgrade_below)
			new_version = latest_version;
		else
			new_version = latest_compatible;
	} else {
		switch (c->opts.version_upgrade) {
		case BCH_VERSION_UPGRADE_compatible:
			new_version = latest_compatible;
			break;
		case BCH_VERSION_UPGRADE_incompatible:
			new_version = latest_version;
			break;
		case BCH_VERSION_UPGRADE_none:
			new_version = min(old_version, latest_version);
			break;
		}
	}

	if (new_version > old_version) {
		if (old_version < bcachefs_metadata_required_upgrade_below)
			prt_str(out, "Version upgrade required:\n");

		if (old_version != c->sb.version) {
			prt_str(out, "Version upgrade from ");
			bch2_version_to_text(out, c->sb.version_upgrade_complete);
			prt_str(out, " to ");
			bch2_version_to_text(out, c->sb.version);
			prt_str(out, " incomplete\n");
		}

		prt_printf(out, "Doing %s version upgrade from ",
			   BCH_VERSION_MAJOR(old_version) != BCH_VERSION_MAJOR(new_version)
			   ? "incompatible" : "compatible");
		bch2_version_to_text(out, old_version);
		prt_str(out, " to ");
		bch2_version_to_text(out, new_version);
		prt_newline(out);

		struct bch_sb_field_ext *ext = bch2_sb_field_get(c->disk_sb.sb, ext);
		__le64 passes = ext->recovery_passes_required[0];
		bch2_sb_set_upgrade(c, old_version, new_version);
		passes = ext->recovery_passes_required[0] & ~passes;

		if (passes) {
			prt_str(out, "Upgrade requires recovery passes: ");
			prt_bitflags(out, bch2_recovery_passes,
				     bch2_recovery_passes_from_stable(le64_to_cpu(passes)));
			prt_newline(out);
		}

		ret = true;
	}

	if (new_version > c->sb.version_incompat_allowed &&
	    c->opts.version_upgrade == BCH_VERSION_UPGRADE_incompatible) {
		prt_str(out, "Now allowing incompatible features up to ");
		bch2_version_to_text(out, new_version);
		prt_str(out, ", previously allowed up to ");
		bch2_version_to_text(out, c->sb.version_incompat_allowed);
		prt_newline(out);

		ret = true;
	}

	if (ret)
		bch2_sb_upgrade(c, new_version,
				c->opts.version_upgrade == BCH_VERSION_UPGRADE_incompatible);

	return ret;
}

noinline_for_stack
static int bch2_fs_opt_version_init(struct bch_fs *c, struct printbuf *out)
{
	if (c->opts.norecovery) {
		c->opts.recovery_pass_last = c->opts.recovery_pass_last
			? min(c->opts.recovery_pass_last, BCH_RECOVERY_PASS_snapshots_read)
			: BCH_RECOVERY_PASS_snapshots_read;
		c->opts.nochanges = true;
	}

	if (c->opts.nochanges)
		c->opts.read_only = true;

	if (c->opts.journal_rewind)
		c->opts.fsck = true;

	if (!(c->sb.features & (BIT_ULL(BCH_FEATURE_small_image)|
			        BIT_ULL(BCH_FEATURE_no_default_sb))) ||
	    bch2_fs_will_resize_on_mount(c))
		set_bit(BCH_FS_may_upgrade_downgrade, &c->flags);

	prt_str(out, "starting version ");
	bch2_version_to_text(out, c->sb.version);
	prt_newline(out);

	bool first = true;
	for (enum bch_opt_id i = 0; i < bch2_opts_nr; i++) {
		const struct bch_option *opt = &bch2_opt_table[i];
		u64 v = bch2_opt_get_by_id(&c->opts, i);

		if (!(opt->flags & OPT_MOUNT))
			continue;

		if (v == bch2_opt_get_by_id(&bch2_opts_default, i))
			continue;

		prt_str(out, first ? "with options: " : ",");
		first = false;
		bch2_opt_to_text(out, c, c->disk_sb.sb, opt, v, OPT_SHOW_MOUNT_STYLE);
	}

	if (!first)
		prt_newline(out);

	if (c->sb.version_incompat_allowed != c->sb.version) {
		prt_printf(out, "allowing incompatible features up to ");
		bch2_version_to_text(out, c->sb.version_incompat_allowed);
		prt_newline(out);
	}

	if (c->opts.verbose) {
		prt_printf(out, "features: ");
		prt_bitflags(out, bch2_sb_features, c->sb.features);
		prt_newline(out);
	}

	if (c->sb.multi_device) {
		first = true;
		prt_printf(out, "with devices: ");
		for_each_online_member(c, ca, BCH_DEV_READ_REF_bch2_online_devs) {
			if (!first)
				prt_char(out, ',');
			first = false;
			prt_str(out, ca->name);
		}
		prt_newline(out);
	}

	/* cf_encoding log message should be here, but it breaks xfstests - sigh */

	if (c->opts.journal_rewind)
		prt_printf(out, "rewinding journal, fsck required\n");

	scoped_guard(mutex_noio, &c->sb_lock) {
		struct bch_sb_field_ext *ext = bch2_sb_field_get(c->disk_sb.sb, ext);

		__le64 now = cpu_to_le64(ktime_get_real_seconds());
		scoped_guard(rcu)
			for_each_online_member_rcu(c, ca)
				bch2_members_v2_get_mut(c->disk_sb.sb, ca->dev_idx)->last_mount = now;

		if (BCH_SB_HAS_TOPOLOGY_ERRORS(c->disk_sb.sb))
			ext->recovery_passes_required[0] |=
				cpu_to_le64(bch2_recovery_passes_to_stable(BIT_ULL(BCH_RECOVERY_PASS_check_topology)));

		u64 sb_passes = bch2_recovery_passes_from_stable(le64_to_cpu(ext->recovery_passes_required[0]));
		if (sb_passes) {
			prt_str(out, "superblock requires following recovery passes to be run: ");
			prt_bitflags(out, bch2_recovery_passes, sb_passes);
			prt_newline(out);
		}

		u64 btrees_lost_data = le64_to_cpu(ext->btrees_lost_data);
		if (btrees_lost_data) {
			prt_str(out, "superblock indicates damage to following btrees:  ");
			prt_bitflags(out, __bch2_btree_ids, btrees_lost_data);
			prt_newline(out);
		}

		if (test_bit(BCH_FS_may_upgrade_downgrade, &c->flags)) {
			if (bch2_check_version_downgrade(c)) {
				prt_str(out, "Version downgrade required");

				__le64 passes = ext->recovery_passes_required[0];
				bch2_sb_set_downgrade(c,
						      BCH_VERSION_MINOR(bcachefs_metadata_version_current),
						      BCH_VERSION_MINOR(c->sb.version));
				passes = ext->recovery_passes_required[0] & ~passes;
				if (passes) {
					prt_str(out, ", running recovery passes: ");
					prt_bitflags(out, bch2_recovery_passes,
						     bch2_recovery_passes_from_stable(le64_to_cpu(passes)));
				}
				prt_newline(out);
			}

			check_version_upgrade(c, out);
		}

		c->opts.recovery_passes |= bch2_recovery_passes_from_stable(le64_to_cpu(ext->recovery_passes_required[0]));

		if (c->sb.version_upgrade_complete < bcachefs_metadata_version_autofix_errors)
			SET_BCH_SB_ERROR_ACTION(c->disk_sb.sb, BCH_ON_ERROR_fix_safe);

		unsigned extent_bp_shift_needed = ilog2(c->opts.encoded_extent_max >> 9) + 1;
		if (extent_bp_shift_needed > c->sb.extent_bp_shift) {
			prt_printf(out, "extent_bp_shift too small: must repair backpointers\n");
			SET_BCH_SB_EXTENT_BP_SHIFT(c->disk_sb.sb, extent_bp_shift_needed);
			ext->recovery_passes_required[0] |=
				cpu_to_le64(bch2_recovery_passes_to_stable(BIT_ULL(BCH_RECOVERY_PASS_check_extents_to_backpointers)));
			ext->recovery_passes_required[0] |=
				cpu_to_le64(bch2_recovery_passes_to_stable(BIT_ULL(BCH_RECOVERY_PASS_check_backpointers_to_extents)));
			__set_bit_le64(BCH_FSCK_ERR_backpointer_to_missing_ptr, ext->errors_silent);
			__set_bit_le64(BCH_FSCK_ERR_ptr_to_missing_backpointer, ext->errors_silent);
		}

		set_bit(BCH_FS_sb_dirty, &c->flags);
	}

	if (c->sb.clean)
		set_bit(BCH_FS_clean_recovery, &c->flags);
	if (c->opts.fsck)
		set_bit(BCH_FS_in_fsck, &c->flags);
	set_bit(BCH_FS_in_recovery, &c->flags);

	/* this really should be part of our one multi line mount message, but -
	 * xfstests... */
	if (c->cf_encoding)
		bch_info(c, "Using encoding defined by superblock: utf8-%u.%u.%u",
			   unicode_major(BCH_FS_DEFAULT_UTF8_ENCODING),
			   unicode_minor(BCH_FS_DEFAULT_UTF8_ENCODING),
			   unicode_rev(BCH_FS_DEFAULT_UTF8_ENCODING));

	if (BCH_SB_INITIALIZED(c->disk_sb.sb)) {
		if (!(c->sb.features & BIT_ULL(BCH_FEATURE_new_extent_overwrite))) {
			prt_str(out, "feature new_extent_overwrite not set, filesystem no longer supported\n");
			return bch_err_throw(c, EINVAL_missing_new_extent_overwrite);
		}

		if (c->sb.version_min < bcachefs_metadata_version_btree_ptr_sectors_written) {
			prt_str(out, "version_min < version_btree_ptr_sectors_written\n");
			prt_str(out, "filesystem needs upgrade from older version; run fsck from older bcachefs-tools to fix\n");
			return bch_err_throw(c, EINVAL_version_min_too_old);
		}
	}

#ifdef __KERNEL__
#ifdef CONFIG_BCACHEFS_RUST
	prt_str(out, "Rust support enabled\n");
#else
	/*
	 * Not CONFIG_RUST: bcachefs vendors its own Rust stack, so a kernel
	 * built without CONFIG_RUST is fine. What matters is what the module
	 * build couldn't find, which fs/Makefile records here - telling someone
	 * to go ask their distribution for CONFIG_RUST when the actual problem
	 * is a missing bindgen wastes everyone's time.
	 */
	prt_str(out, "built without Rust support; this will be required in the near future\n");
#ifdef BCACHEFS_NO_RUST_REASON
	prt_printf(out, "  reason: %s\n", BCACHEFS_NO_RUST_REASON);
#endif
	prt_str(out, "  rebuild the module with rustc, bindgen and rust-src available to enable it\n");
#endif
#endif

	bch2_fs_mi_field_upgrades(c);

	return 0;
}

static int bch2_fs_init(struct bch_fs *c, struct bch_sb *sb,
			struct bch_opts *opts, bch_sb_handles *sbs,
			struct printbuf *out)
{
	CLASS(printbuf, name)();

	c->stdio = (void *)(unsigned long) opts->stdio;
	c->recovery_task = current;

	__module_get(THIS_MODULE);

	closure_init(&c->cl, NULL);

	kobject_init(&c->kobj, &bch2_fs_ktype);
	kobject_init(&c->internal, &bch2_fs_internal_ktype);
	kobject_init(&c->opts_dir, &bch2_fs_opts_dir_ktype);
	kobject_init(&c->time_stats, &bch2_fs_time_stats_ktype);
	kobject_init(&c->time_stats_json, &bch2_fs_time_stats_json_ktype);
	kobject_init(&c->counters_kobj, &bch2_fs_counters_ktype);

	c->minor		= -1;
	c->disk_sb.fs_sb	= true;

	init_rwsem(&c->state_lock);
	mutex_noio_init(&c->sb_lock);
	INIT_WORK(&c->read_only_work, bch2_fs_read_only_work);

	refcount_set(&c->ro_ref, 1);
	init_waitqueue_head(&c->ro_ref_wait);
	mutex_init(&c->opt_change_lock);

	for (unsigned i = 0; i < BCH_TIME_STAT_NR; i++)
		bch2_time_stats_init(&c->times[i]);

	bch2_fs_allocator_background_init(c);
	bch2_fs_allocator_foreground_init(c);
	bch2_fs_btree_gc_init_early(c);
	bch2_fs_btree_init_early(c);
	bch2_fs_copygc_init(c);
	bch2_fs_counters_init_early(c);
	bch2_fs_discards_init_early(c);
	bch2_fs_ec_init_early(c);
	bch2_fs_errors_init_early(c);
	bch2_fs_journal_init_early(&c->journal);
	bch2_fs_journal_keys_init(c);
	bch2_fs_move_init(c);
	bch2_fs_nocow_locking_init_early(c);
	bch2_fs_quota_init(c);
	bch2_fs_recovery_passes_init(c);
	bch2_fs_snapshots_init_early(c);
	bch2_fs_subvolumes_init_early(c);

	INIT_LIST_HEAD(&c->list);

	mutex_init(&c->bio_bounce_pages_lock);

	spin_lock_init(&c->write_error_lock);

	INIT_LIST_HEAD(&c->journal_iters);

	c->journal.flush_write_time	= &c->times[BCH_TIME_journal_flush_write];
	c->journal.noflush_write_time	= &c->times[BCH_TIME_journal_noflush_write];
	c->journal.flush_seq_time	= &c->times[BCH_TIME_journal_flush_seq];

	/* must be initialized before we throw any errors */
	c->counters.now = __alloc_percpu(sizeof(u64) * BCH_COUNTER_NR, sizeof(u64));
	if (!c->counters.now)
		return -BCH_ERR_ENOMEM_fs_counters_init;

	try(bch2_fs_capacity_init(c));

	scoped_guard(mutex_noio, &c->sb_lock) {
		try(bch2_sb_to_fs(c, sb));

		sb = c->disk_sb.sb;

		try(bch2_sb_members_v2_init(c));

		/* Ensure sb_field_ext and members_v2 exist at current size
		 * before reading opts, so ext opts see a fully-sized field: */
		struct bch_sb_field_ext *ext =
		    bch2_sb_field_get_minsize(&c->disk_sb, ext,
				sizeof(struct bch_sb_field_ext) / sizeof(u64));
		if (!ext)
			return bch_err_throw(c, ENOSPC_sb);

		sb = c->disk_sb.sb;

		/* Compat: */
		if (!BCH_SB_JOURNAL_FLUSH_DELAY(sb))
			SET_BCH_SB_JOURNAL_FLUSH_DELAY(sb, 1000);
		if (!BCH_SB_JOURNAL_RECLAIM_DELAY(sb))
			SET_BCH_SB_JOURNAL_RECLAIM_DELAY(sb, 1000);

		if (!BCH_SB_VERSION_UPGRADE_COMPLETE(sb))
			SET_BCH_SB_VERSION_UPGRADE_COMPLETE(sb, le16_to_cpu(sb->version));

		if (le16_to_cpu(sb->version) <= bcachefs_metadata_version_disk_accounting_v2 &&
		    !BCH_SB_ALLOCATOR_STUCK_TIMEOUT(sb))
			SET_BCH_SB_ALLOCATOR_STUCK_TIMEOUT(sb, 30);

		if (le16_to_cpu(sb->version) <= bcachefs_metadata_version_disk_accounting_v2)
			SET_BCH_SB_PROMOTE_WHOLE_EXTENTS(sb, true);

		if (!BCH_SB_WRITE_ERROR_TIMEOUT(sb))
			SET_BCH_SB_WRITE_ERROR_TIMEOUT(sb, 30);

		if (le16_to_cpu(sb->version) <= bcachefs_metadata_version_extent_flags &&
		    !BCH_SB_CSUM_ERR_RETRY_NR(sb))
			SET_BCH_SB_CSUM_ERR_RETRY_NR(sb, 3);

		if (!BCH_SB_EXT_DEV_READAHEAD(ext))
			SET_BCH_SB_EXT_DEV_READAHEAD(ext, SZ_2M >> 9);

		if (!BCH_SB_EXT_EC_STRIPE_BUF_LIMIT(ext))
			SET_BCH_SB_EXT_EC_STRIPE_BUF_LIMIT(ext, 5);

		if (!BCH_SB_EXT_BTREE_CACHE_SHRINKER_SEEKS(ext))
			SET_BCH_SB_EXT_BTREE_CACHE_SHRINKER_SEEKS(ext, 4);

		if (le16_to_cpu(sb->version) <= bcachefs_metadata_version_erasure_coding &&
		    !BCH_SB_EXT_DISCARD_BUFFER(ext))
			SET_BCH_SB_EXT_DISCARD_BUFFER(ext, 4);

		for (unsigned opt_id = 0; opt_id < bch2_opts_nr; opt_id++) {
			const struct bch_option *opt = bch2_opt_table + opt_id;

			if (opt->get_sb || opt->get_ext) {
				u64 v = bch2_opt_from_sb(sb, opt_id, -1);

				CLASS(printbuf, err)();
				int ret = bch2_opt_validate(opt, v, &err);
				if (ret) {
					prt_printf(out, "Invalid superblock option %s\n", err.buf);
					return ret;
				}
			}
		}
	}

	c->opts = bch2_opts_default;
	try(bch2_opts_from_sb(&c->opts, sb));

	bch2_opts_apply(&c->opts, *opts);

#ifdef __KERNEL__
	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
	    c->opts.block_size > PAGE_SIZE) {
		prt_printf(out, "cannot mount bs > ps filesystem without CONFIG_TRANSPARENT_HUGEPAGE\n");
		return bch_err_throw(c, EINVAL_block_size_needs_thp);
	}
#endif

	c->block_bits		= ilog2(block_sectors(c));

	bch2_fs_inode_shard_cpu_init(c);

	if (bch2_fs_init_fault("fs_alloc")) {
		prt_printf(out, "fs_alloc fault injected\n");
		return -EFAULT;
	}

	if (c->sb.multi_device)
		pr_uuid(&name, c->sb.user_uuid.b);
	else
		prt_bdevname(&name, sbs->data[0].bdev);

	try(name.allocation_failure ? -BCH_ERR_ENOMEM_fs_name_alloc : 0);

	strscpy(c->name, name.buf, sizeof(c->name));

	if (enumerated_ref_init(&c->writes, BCH_WRITE_REF_NR,
				bch2_writes_disabled))
		return bch_err_throw(c, ENOMEM_fs_other_alloc);

	try(bch2_blacklist_table_initialize(c));
#ifdef CONFIG_DEBUG_FS
	try(bch2_fs_async_obj_init(c));
#endif
	try(bch2_fs_btree_init(c));
	try(bch2_fs_compress_init(c));
	try(bch2_fs_counters_init(c));
	try(bch2_fs_data_update_init(c));
	try(bch2_fs_discards_init(c));
	try(bch2_fs_ec_init(c));
	try(bch2_fs_errors_init(c));
	try(bch2_fs_encryption_init(c));
	try(bch2_fs_io_read_init(c));
	try(bch2_fs_journal_init(&c->journal));
	try(bch2_fs_snapshots_init(c));
	try(bch2_fs_vfs_init(c));
	try(bch2_io_clock_init(&c->io_clock[READ]));
	try(bch2_io_clock_init(&c->io_clock[WRITE]));

#if IS_ENABLED(CONFIG_UNICODE)
	if (!bch2_fs_casefold_enabled(c)) {
		/* Default encoding until we can potentially have more as an option. */
		c->cf_encoding = utf8_load(BCH_FS_DEFAULT_UTF8_ENCODING);
		if (IS_ERR(c->cf_encoding)) {
			prt_printf(out, "Cannot load UTF-8 encoding for filesystem. Version: %u.%u.%u\n",
				   unicode_major(BCH_FS_DEFAULT_UTF8_ENCODING),
				   unicode_minor(BCH_FS_DEFAULT_UTF8_ENCODING),
				   unicode_rev(BCH_FS_DEFAULT_UTF8_ENCODING));
			return bch_err_throw(c, EINVAL_utf8_load_failed);
		}
	}
#else
	if (c->sb.features & BIT_ULL(BCH_FEATURE_casefolding)) {
		prt_printf(out, "Cannot mount a filesystem with casefolding on a kernel without CONFIG_UNICODE\n");
		return bch_err_throw(c, EINVAL_casefolding_no_unicode);
	}
#endif

	for (unsigned i = 0; i < c->sb.nr_devices; i++) {
		if (!bch2_member_exists(c->disk_sb.sb, i))
			continue;
		try(bch2_dev_alloc(c, i));
	}

	bch2_journal_entry_res_resize(&c->journal,
			&c->btree.root_journal_res,
			BTREE_ID_NR * (JSET_KEYS_U64s + BKEY_BTREE_PTR_U64s_MAX));
	bch2_journal_entry_res_resize(&c->journal,
			&c->clock_journal_res,
			(sizeof(struct jset_entry_clock) / sizeof(u64)) * 2);
	bch2_journal_entry_res_resize(&c->journal,
			&c->rewind_limit_res,
			sizeof(struct jset_entry_rewind_limit) / sizeof(u64));

	scoped_guard(rwsem_write, &c->state_lock)
		darray_for_each(*sbs, sb)
			try(bch2_dev_attach_bdev(c, sb, out));

	if (!c->opts.no_version_check) {
		/*
		 * Do this early, so that we never expose a filesystem object that
		 * hasn't been version downgraded
		 */
		try(bch2_fs_opt_version_init(c, out));
	}

	if (IS_ENABLED(CONFIG_BCACHEFS_DEBUG))
		prt_printf(out, "*** DEBUG BUILD ***\n");

	scoped_guard(mutex, &bch2_fs_list_lock)
		try(bch2_fs_online(c));

	return 0;
}

static struct bch_fs *bch2_fs_alloc(struct bch_sb *sb, struct bch_opts *opts,
				    bch_sb_handles *sbs,
				    const struct bch_key *user_key,
				    struct printbuf *out)
{
	struct bch_fs *c = kvzalloc(sizeof(struct bch_fs), GFP_KERNEL);
	if (!c)
		return ERR_PTR(-BCH_ERR_ENOMEM_fs_alloc);

	if (user_key) {
		c->user_key = *user_key;
		c->user_key_set = true;
	}

	int ret = bch2_fs_init(c, sb, opts, sbs, out);
	if (ret) {
		bch2_fs_exit(c);
		return ERR_PTR(ret);
	}

	return c;
}

__cold void bch2_missing_devs_to_text(struct printbuf *out, struct bch_fs *c)
{
	prt_printf(out, "Missing devices\n");
	for_each_member_device(c, ca)
		if (!bch2_dev_is_online(ca) && bch2_dev_has_data(c, ca)) {
			prt_printf(out, "Device %u\n", ca->dev_idx);
			guard(printbuf_indent)(out);
			bch2_member_to_text_short(out, c, ca);
		}
}

static int bch2_fs_may_start(struct bch_fs *c, struct printbuf *err)
{
	unsigned flags = 0;

	if (c->opts.no_version_check) {
		prt_printf(err, "Cannot start with opts.no_version_check\n");
		return bch_err_throw(c, EINVAL_no_version_check_start);
	}

	switch (c->opts.degraded) {
	case BCH_DEGRADED_very:
		flags |= BCH_FORCE_IF_DEGRADED|BCH_FORCE_IF_LOST;
		break;
	case BCH_DEGRADED_yes:
		flags |= BCH_FORCE_IF_DEGRADED;
		break;
	default: {
		bool missing = false;
		for_each_member_device(c, ca)
			if (!bch2_dev_is_online(ca) &&
			    (ca->mi.state != BCH_MEMBER_STATE_evacuating ||
			     bch2_dev_has_data(c, ca))) {
				prt_printf(err, "Cannot mount without device %u\n", ca->dev_idx);
				guard(printbuf_indent)(err);
				bch2_member_to_text_short(err, c, ca);
				missing = true;
			}

		if (!missing)
			return 0;

		/*
		 * Which refusal this is decides what there is to consent to, so
		 * it goes in the error code and not just the message:
		 * mount.bcachefs puts the question to whoever is at the
		 * machine, and prose is not an interface.
		 *
		 * degraded=yes is enough while every replica set still has a
		 * readable copy; past that only degraded=very will start, and
		 * reads of what is gone will fail.
		 */
		return bch2_can_read_fs_with_devs(c, &c->devs_online,
						  BCH_FORCE_IF_DEGRADED, err)
			? bch_err_throw(c, insufficient_devices_data_intact)
			: bch_err_throw(c, insufficient_devices_data_lost);
	}
	}

	if (!bch2_can_read_fs_with_devs(c, &c->devs_online, flags, err) ||
	    (!c->opts.read_only &&
	     !bch2_can_write_fs_with_devs(c, c->allocator.rw_devs[0], flags, err))) {
		bch2_missing_devs_to_text(err, c);
		return bch_err_throw(c, insufficient_devices_to_start);
	}

	return 0;
}

static int __bch2_fs_start(struct bch_fs *c, struct printbuf *err)
{
	BUG_ON(test_bit(BCH_FS_started, &c->flags));

	scoped_guard(rwsem_write, &c->state_lock) {
		scoped_guard(rcu)
			for_each_online_member_rcu(c, ca)
				if (ca->mi.state == BCH_MEMBER_STATE_rw)
					bch2_dev_allocator_add(c, ca);

		bch2_recalc_capacity(c);
	}

	try(bch2_fs_may_start(c, err));

	try(bch2_fs_reconcile_init(c));
	try(bch2_fs_counters_init_late(c));

	/*
	 * Request no_sb_user_data_replicas eagerly at startup so it gets
	 * persisted before any user-data accounting fires. Otherwise the
	 * bump only happens lazily inside __bch2_accounting_maybe_kill (when
	 * a user-data accounting entry zeroes), and a fresh fs that gets
	 * forcibly shut down before that ever fires never persists the
	 * version_incompat bump - on next mount, bch2_replicas_marked_locked
	 * doesn't short-circuit for user data and accounting_read fsck_err's
	 * for replicas not in the (no-longer-storing-them) sb.
	 */
	bch2_request_incompat_feature(c, bcachefs_metadata_version_no_sb_user_data_replicas);

	/*
	 * just make sure this is always allocated if we might need it - mount
	 * failing due to kthread_create() failing is _very_ annoying
	 */
	if (go_rw_in_recovery(c))
		try(bch2_fs_init_rw(c));

	/*
	 * check mount options as early as possible; some can only be checked
	 * after starting
	 */
	try(bch2_opts_hooks_pre_set(c));

	try(BCH_SB_INITIALIZED(c->disk_sb.sb)
	    ? bch2_fs_recovery(c)
	    : bch2_fs_initialize(c));

	try(bch2_opts_hooks_pre_set(c));

	if (bch2_fs_init_fault("fs_start"))
		return bch_err_throw(c, injected_fs_start);

	set_bit(BCH_FS_started, &c->flags);
	wake_up(&c->ro_ref_wait);

	scoped_guard(rwsem_write, &c->state_lock) {
		if (c->opts.read_only)
			bch2_fs_read_only(c);
		else if (!test_bit(BCH_FS_rw, &c->flags))
			try(bch2_fs_read_write(c));
	}

	return 0;
}

int bch2_fs_start(struct bch_fs *c)
{
	CLASS(printbuf, err)();
	bch2_log_msg_start(c, &err);
	unsigned pos = err.pos;

	int ret = __bch2_fs_start(c, &err);
	c->recovery_task = NULL;

	if (ret)
		prt_printf(&err, "error starting filesystem: %s", bch2_err_str(ret));
	if (err.pos != pos)
		bch2_print_str(c, KERN_ERR, err.buf);

	return ret;
}

static bool bch2_dev_will_resize_on_mount(struct bch_dev *ca)
{
	return ca->mi.resize_on_mount &&
		ca->mi.nbuckets < div64_u64(get_capacity(ca->disk_sb.bdev->bd_disk),
					    ca->mi.bucket_size);
}

static bool bch2_fs_will_resize_on_mount(struct bch_fs *c)
{
	bool ret = false;
	for_each_online_member(c, ca, BCH_DEV_READ_REF_fs_resize_on_mount)
		ret |= bch2_dev_will_resize_on_mount(ca);
	return ret;
}

int bch2_fs_resize_on_mount(struct bch_fs *c)
{
	for_each_online_member(c, ca, BCH_DEV_READ_REF_fs_resize_on_mount) {
		if (bch2_dev_will_resize_on_mount(ca)) {
			u64 old_nbuckets = ca->mi.nbuckets;
			u64 new_nbuckets = div64_u64(get_capacity(ca->disk_sb.bdev->bd_disk),
						     ca->mi.bucket_size);

			bch_info_dev(ca, "resizing to size %llu", new_nbuckets * ca->mi.bucket_size);
			int ret = bch2_dev_buckets_resize(c, ca, new_nbuckets);
			bch_err_fn_dev(ca, ret);
			if (ret) {
				enumerated_ref_put(&ca->io_ref[READ],
						   BCH_DEV_READ_REF_fs_resize_on_mount);
				return ret;
			}

			scoped_guard(mutex_noio, &c->sb_lock) {
				struct bch_member *m =
					bch2_members_v2_get_mut(c->disk_sb.sb, ca->dev_idx);
				m->nbuckets = cpu_to_le64(new_nbuckets);
				SET_BCH_MEMBER_RESIZE_ON_MOUNT(m, false);

				c->disk_sb.sb->features[0] &= ~cpu_to_le64(BIT_ULL(BCH_FEATURE_small_image));
				bch2_write_super(c);
			}

			if (ca->mi.freespace_initialized) {
				ret = __bch2_dev_resize_alloc(ca, old_nbuckets, new_nbuckets);
				if (ret) {
					enumerated_ref_put(&ca->io_ref[READ],
							BCH_DEV_READ_REF_fs_resize_on_mount);
					return ret;
				}
			}
		}
	}
	return 0;
}

/* Filesystem open: */

static inline int sb_cmp(struct bch_sb *l, struct bch_sb *r)
{
	return  cmp_int(le64_to_cpu(l->seq), le64_to_cpu(r->seq)) ?:
		cmp_int(le64_to_cpu(l->write_time), le64_to_cpu(r->write_time));
}

int bch2_sbs_filter_dead(bch_sb_handles *sbs, struct bch_opts *opts, struct printbuf *out)
{
	struct bch_sb_handle *best = NULL;
	int ret;

	for (size_t i = 0; i < sbs->nr; i++)
		if (!best || sb_cmp(sbs->data[i].sb, best->sb) > 0)
			best = &sbs->data[i];

	if (!best)
		return 0;

	for (size_t i = sbs->nr; i; --i) {
		struct bch_sb_handle *sb = &sbs->data[i - 1];

		ret = bch2_dev_in_fs(best, sb, opts);

		if (ret == -BCH_ERR_device_has_been_removed ||
		    ret == -BCH_ERR_device_splitbrain) {
			if (out)
				prt_printf(out, "Not using device %s: %s\n",
					   sb->sb_name, bch2_err_str(ret));
			bch2_free_super(sb);
			array_remove_item(sbs->data, sbs->nr, i - 1);
			best -= best > sb;
			continue;
		}

		if (ret) {
			if (out)
				prt_printf(out, "Cannot mount with device %s: %s\n",
					   sb->sb_name, bch2_err_str(ret));
			return ret;
		}
	}

	if (best != sbs->data)
		swap(*best, sbs->data[0]);

	return 0;
}

static struct bch_fs *__bch2_fs_open(darray_const_str *devices,
				     struct bch_opts *opts,
				     const struct bch_key *user_key,
				     struct printbuf *out)
{
	bch_sb_handles sbs = {};
	struct bch_fs *c = NULL;
	int ret = 0;

	if (!try_module_get(THIS_MODULE))
		return ERR_PTR(-ENODEV);

	if (!devices->nr) {
		ret = -EINVAL;
		goto err;
	}

	ret = darray_make_room(&sbs, devices->nr);
	if (ret)
		goto err;

	darray_for_each(*devices, i) {
		struct bch_sb_handle sb = { NULL };

		ret = bch2_read_super(*i, opts, &sb);
		if (ret)
			goto err;

		BUG_ON(darray_push(&sbs, sb));
	}

	ret = bch2_sbs_filter_dead(&sbs, opts, out);
	if (ret)
		goto err;

	c = bch2_fs_alloc(sbs.data->sb, opts, &sbs, user_key, out);
	ret = PTR_ERR_OR_ZERO(c);
	if (ret)
		goto err;

	if (out->buf) {
		/* Log opt_version_init() message before doing actual filesystem startup */
		CLASS(printbuf, msg_with_prefix)();
		prt_str(&msg_with_prefix, out->buf);
		bch2_print_str(c, KERN_INFO, msg_with_prefix.buf);
		printbuf_reset(out);
	}

	if (!c->opts.nostart) {
		ret = __bch2_fs_start(c, out);
		c->recovery_task = NULL;
		if (ret)
			goto err;
	}
out:
	darray_for_each(sbs, sb)
		bch2_free_super(sb);
	darray_exit(&sbs);
	module_put(THIS_MODULE);
	return c;
err:
	if (!IS_ERR_OR_NULL(c))
		bch2_fs_exit(c);
	c = ERR_PTR(ret);
	goto out;
}

struct bch_fs *bch2_fs_open(darray_const_str *devices,
			    struct bch_opts *opts,
			    const struct bch_key *user_key)
{
	CLASS(printbuf, msg)();
	printbuf_indent_add_nextline(&msg, 2);

	struct bch_fs *c = __bch2_fs_open(devices, opts, user_key, &msg);
	int ret = PTR_ERR_OR_ZERO(c);

	if (ret) {
		prt_printf(&msg, "error starting filesystem: %s", bch2_err_str(ret));
		bch2_print_string_as_lines(KERN_ERR, msg.buf);
	} else if (msg.pos) {
		CLASS(bch_log_msg_level, msg_with_prefix)(c, 6);
		prt_str(&msg_with_prefix.m, msg.buf);
	}

	return c;
}

/* Global interfaces/init */

static void bcachefs_exit(void)
{
	bch2_debug_exit();
	bch2_vfs_exit();
	bch2_chardev_exit();
	bch2_btree_key_cache_exit();
	bch2_lock_graph_exit();
	kobject_put(&bcachefs_kobj);
}

static int __init bcachefs_init(void)
{
	bch2_bkey_pack_test();

	bch2_dirent_init();

	kobject_init(&bcachefs_kobj, &bcachefs_ktype);

	if (kobject_add(&bcachefs_kobj, fs_kobj, "bcachefs") ||
	    bch2_lock_graph_init() ||
	    bch2_btree_key_cache_init() ||
	    bch2_chardev_init() ||
	    bch2_vfs_init() ||
	    bch2_debug_init())
		goto err;

	return 0;
err:
	bcachefs_exit();
	return -ENOMEM;
}

#define BCH_DEBUG_PARAM(name, description) DEFINE_STATIC_KEY_FALSE(bch2_##name);
BCH_DEBUG_PARAMS_ALL()
#undef BCH_DEBUG_PARAM

static int bch2_param_set_static_key_t(const char *val, const struct kernel_param *kp)
{
	/* Match bool exactly, by re-using it. */
	struct static_key *key = kp->arg;
	struct kernel_param boolkp = *kp;
	bool v;
	int ret;

	boolkp.arg = &v;

	ret = param_set_bool(val, &boolkp);
	if (ret)
		return ret;
	if (v)
		static_key_enable(key);
	else
		static_key_disable(key);
	return 0;
}

static int bch2_param_get_static_key_t(char *buffer, const struct kernel_param *kp)
{
	struct static_key *key = kp->arg;
	return sprintf(buffer, "%c\n", static_key_enabled(key) ? 'Y' : 'N');
}

/* this is unused in userspace - silence the warning */
__maybe_unused
static const struct kernel_param_ops bch2_param_ops_static_key_t = {
	.flags = KERNEL_PARAM_OPS_FL_NOARG,
	.set = bch2_param_set_static_key_t,
	.get = bch2_param_get_static_key_t,
};

#define BCH_DEBUG_PARAM(name, description)				\
	module_param_cb(name, &bch2_param_ops_static_key_t, &bch2_##name.key, 0644);\
	__MODULE_PARM_TYPE(name, "static_key_t");			\
	MODULE_PARM_DESC(name, description);
BCH_DEBUG_PARAMS()
#undef BCH_DEBUG_PARAM

__maybe_unused
static unsigned bch2_metadata_version = bcachefs_metadata_version_current;
module_param_named(version, bch2_metadata_version, uint, 0444);

module_exit(bcachefs_exit);
module_init(bcachefs_init);
