]> git.sesse.net Git - bcachefs-tools-debian/blobdiff - libbcachefs/super.c
Move c_src dirs back to toplevel
[bcachefs-tools-debian] / libbcachefs / super.c
index 19f96921c6ee554a35125c1c73f8e058a248037b..9dbc35940197f1c55c1bc48746bc23a3983ac203 100644 (file)
@@ -1,3 +1,4 @@
+// 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.
  */
 
 #include "bcachefs.h"
-#include "alloc.h"
+#include "alloc_background.h"
+#include "alloc_foreground.h"
+#include "bkey_sort.h"
 #include "btree_cache.h"
 #include "btree_gc.h"
-#include "btree_update.h"
+#include "btree_journal_iter.h"
+#include "btree_key_cache.h"
+#include "btree_update_interior.h"
 #include "btree_io.h"
+#include "btree_write_buffer.h"
+#include "buckets_waiting_for_journal.h"
 #include "chardev.h"
 #include "checksum.h"
 #include "clock.h"
 #include "compress.h"
+#include "counters.h"
 #include "debug.h"
+#include "disk_groups.h"
+#include "ec.h"
+#include "errcode.h"
 #include "error.h"
 #include "fs.h"
-#include "fs-gc.h"
+#include "fs-io.h"
+#include "fs-io-buffered.h"
+#include "fs-io-direct.h"
+#include "fsck.h"
 #include "inode.h"
-#include "io.h"
+#include "io_read.h"
+#include "io_write.h"
 #include "journal.h"
-#include "keylist.h"
+#include "journal_reclaim.h"
+#include "journal_seq_blacklist.h"
 #include "move.h"
 #include "migrate.h"
 #include "movinggc.h"
+#include "nocow_locking.h"
+#include "quota.h"
+#include "rebalance.h"
+#include "recovery.h"
+#include "replicas.h"
+#include "sb-clean.h"
+#include "sb-errors.h"
+#include "sb-members.h"
+#include "snapshot.h"
+#include "subvolume.h"
 #include "super.h"
 #include "super-io.h"
 #include "sysfs.h"
-#include "tier.h"
+#include "trace.h"
 
 #include <linux/backing-dev.h>
 #include <linux/blkdev.h>
 #include <linux/debugfs.h>
 #include <linux/device.h>
-#include <linux/genhd.h>
 #include <linux/idr.h>
-#include <linux/kthread.h>
 #include <linux/module.h>
 #include <linux/percpu.h>
 #include <linux/random.h>
 #include <linux/sysfs.h>
 #include <crypto/hash.h>
 
-#include <trace/events/bcachefs.h>
-
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Kent Overstreet <kent.overstreet@gmail.com>");
+MODULE_DESCRIPTION("bcachefs filesystem");
+MODULE_SOFTDEP("pre: crc32c");
+MODULE_SOFTDEP("pre: crc64");
+MODULE_SOFTDEP("pre: sha256");
+MODULE_SOFTDEP("pre: chacha20");
+MODULE_SOFTDEP("pre: poly1305");
+MODULE_SOFTDEP("pre: xxhash");
+
+const char * const bch2_fs_flag_strs[] = {
+#define x(n)           #n,
+       BCH_FS_FLAGS()
+#undef x
+       NULL
+};
+
+void __bch2_print(struct bch_fs *c, const char *fmt, ...)
+{
+       struct stdio_redirect *stdio = bch2_fs_stdio_redirect(c);
+
+       va_list args;
+       va_start(args, fmt);
+       if (likely(!stdio)) {
+               vprintk(fmt, args);
+       } else {
+               unsigned long flags;
+
+               if (fmt[0] == KERN_SOH[0])
+                       fmt += 2;
+
+               spin_lock_irqsave(&stdio->output_lock, flags);
+               prt_vprintf(&stdio->output_buf, fmt, args);
+               spin_unlock_irqrestore(&stdio->output_lock, flags);
+
+               wake_up(&stdio->output_wait);
+       }
+       va_end(args);
+}
 
 #define KTYPE(type)                                                    \
-struct kobj_type type ## _ktype = {                                    \
+static const struct attribute_group type ## _group = {                 \
+       .attrs = type ## _files                                         \
+};                                                                     \
+                                                                       \
+static const struct attribute_group *type ## _groups[] = {             \
+       &type ## _group,                                                \
+       NULL                                                            \
+};                                                                     \
+                                                                       \
+static const struct kobj_type type ## _ktype = {                       \
        .release        = type ## _release,                             \
        .sysfs_ops      = &type ## _sysfs_ops,                          \
-       .default_attrs  = type ## _files                                \
+       .default_groups = type ## _groups                               \
 }
 
 static void bch2_fs_release(struct kobject *);
 static void bch2_dev_release(struct kobject *);
+static void bch2_fs_counters_release(struct kobject *k)
+{
+}
 
 static void bch2_fs_internal_release(struct kobject *k)
 {
@@ -72,35 +143,34 @@ static void bch2_fs_time_stats_release(struct kobject *k)
 {
 }
 
-static KTYPE(bch2_fs);
-static KTYPE(bch2_fs_internal);
-static KTYPE(bch2_fs_opts_dir);
-static KTYPE(bch2_fs_time_stats);
-static KTYPE(bch2_dev);
+KTYPE(bch2_fs);
+KTYPE(bch2_fs_counters);
+KTYPE(bch2_fs_internal);
+KTYPE(bch2_fs_opts_dir);
+KTYPE(bch2_fs_time_stats);
+KTYPE(bch2_dev);
 
 static struct kset *bcachefs_kset;
 static LIST_HEAD(bch_fs_list);
 static DEFINE_MUTEX(bch_fs_list_lock);
 
-static DECLARE_WAIT_QUEUE_HEAD(bch_read_only_wait);
+DECLARE_WAIT_QUEUE_HEAD(bch2_read_only_wait);
 
 static void bch2_dev_free(struct bch_dev *);
 static int bch2_dev_alloc(struct bch_fs *, unsigned);
-static int bch2_dev_sysfs_online(struct bch_dev *);
+static int bch2_dev_sysfs_online(struct bch_fs *, struct bch_dev *);
 static void __bch2_dev_read_only(struct bch_fs *, struct bch_dev *);
 
-struct bch_fs *bch2_bdev_to_fs(struct block_device *bdev)
+struct bch_fs *bch2_dev_to_fs(dev_t dev)
 {
        struct bch_fs *c;
-       struct bch_dev *ca;
-       unsigned i;
 
        mutex_lock(&bch_fs_list_lock);
        rcu_read_lock();
 
        list_for_each_entry(c, &bch_fs_list, list)
-               for_each_member_device_rcu(ca, c, i)
-                       if (ca->disk_sb.bdev == bdev) {
+               for_each_member_device_rcu(c, ca, NULL)
+                       if (ca->disk_sb.bdev && ca->disk_sb.bdev->bd_dev == dev) {
                                closure_get(&c->cl);
                                goto found;
                        }
@@ -112,20 +182,20 @@ found:
        return c;
 }
 
-static struct bch_fs *__bch2_uuid_to_fs(uuid_le uuid)
+static struct bch_fs *__bch2_uuid_to_fs(__uuid_t uuid)
 {
        struct bch_fs *c;
 
        lockdep_assert_held(&bch_fs_list_lock);
 
        list_for_each_entry(c, &bch_fs_list, list)
-               if (!memcmp(&c->disk_sb->uuid, &uuid, sizeof(uuid_le)))
+               if (!memcmp(&c->disk_sb.sb->uuid, &uuid, sizeof(uuid)))
                        return c;
 
        return NULL;
 }
 
-struct bch_fs *bch2_uuid_to_fs(uuid_le uuid)
+struct bch_fs *bch2_uuid_to_fs(__uuid_t uuid)
 {
        struct bch_fs *c;
 
@@ -138,48 +208,20 @@ struct bch_fs *bch2_uuid_to_fs(uuid_le uuid)
        return c;
 }
 
-int bch2_congested(struct bch_fs *c, int bdi_bits)
+static void bch2_dev_usage_journal_reserve(struct bch_fs *c)
 {
-       struct backing_dev_info *bdi;
-       struct bch_dev *ca;
-       unsigned i;
-       int ret = 0;
+       unsigned nr = 0, u64s =
+               ((sizeof(struct jset_entry_dev_usage) +
+                 sizeof(struct jset_entry_dev_usage_type) * BCH_DATA_NR)) /
+               sizeof(u64);
 
-       if (bdi_bits & (1 << WB_sync_congested)) {
-               /* Reads - check all devices: */
-               for_each_readable_member(ca, c, i) {
-                       bdi = blk_get_backing_dev_info(ca->disk_sb.bdev);
-
-                       if (bdi_congested(bdi, bdi_bits)) {
-                               ret = 1;
-                               break;
-                       }
-               }
-       } else {
-               /* Writes prefer fastest tier: */
-               struct bch_tier *tier = READ_ONCE(c->fastest_tier);
-               struct dev_group *grp = tier ? &tier->devs : &c->all_devs;
-
-               rcu_read_lock();
-               group_for_each_dev(ca, grp, i) {
-                       bdi = blk_get_backing_dev_info(ca->disk_sb.bdev);
-
-                       if (bdi_congested(bdi, bdi_bits)) {
-                               ret = 1;
-                               break;
-                       }
-               }
-               rcu_read_unlock();
-       }
-
-       return ret;
-}
-
-static int bch2_congested_fn(void *data, int bdi_bits)
-{
-       struct bch_fs *c = data;
+       rcu_read_lock();
+       for_each_member_device_rcu(c, ca, NULL)
+               nr++;
+       rcu_read_unlock();
 
-       return bch2_congested(c, bdi_bits);
+       bch2_journal_entry_res_resize(&c->journal,
+                       &c->dev_usage_journal_res, u64s * nr);
 }
 
 /* Filesystem RO/RW: */
@@ -187,9 +229,9 @@ static int bch2_congested_fn(void *data, int bdi_bits)
 /*
  * For startup/shutdown of RW stuff, the dependencies are:
  *
- * - foreground writes depend on copygc and tiering (to free up space)
+ * - foreground writes depend on copygc and rebalance (to free up space)
  *
- * - copygc and tiering depend on mark and sweep gc (they actually probably
+ * - 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)
@@ -201,57 +243,78 @@ static int bch2_congested_fn(void *data, int bdi_bits)
 
 static void __bch2_fs_read_only(struct bch_fs *c)
 {
-       struct bch_dev *ca;
-       unsigned i;
+       unsigned clean_passes = 0;
+       u64 seq = 0;
 
-       bch2_tiering_stop(c);
+       bch2_fs_ec_stop(c);
+       bch2_open_buckets_stop(c, NULL, true);
+       bch2_rebalance_stop(c);
+       bch2_copygc_stop(c);
+       bch2_gc_thread_stop(c);
+       bch2_fs_ec_flush(c);
 
-       for_each_member_device(ca, c, i)
-               bch2_moving_gc_stop(ca);
+       bch_verbose(c, "flushing journal and stopping allocators, journal seq %llu",
+                   journal_cur_seq(&c->journal));
 
-       bch2_gc_thread_stop(c);
+       do {
+               clean_passes++;
 
-       bch2_btree_flush(c);
+               if (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);
 
-       for_each_member_device(ca, c, i)
-               bch2_dev_allocator_stop(ca);
+       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);
+
+       /*
+        * After stopping journal:
+        */
+       for_each_member_device(c, ca)
+               bch2_dev_allocator_remove(c, ca);
 }
 
+#ifndef BCH_WRITE_REF_DEBUG
 static void bch2_writes_disabled(struct percpu_ref *writes)
 {
        struct bch_fs *c = container_of(writes, struct bch_fs, writes);
 
-       set_bit(BCH_FS_WRITE_DISABLE_COMPLETE, &c->flags);
-       wake_up(&bch_read_only_wait);
+       set_bit(BCH_FS_write_disable_complete, &c->flags);
+       wake_up(&bch2_read_only_wait);
 }
+#endif
 
 void bch2_fs_read_only(struct bch_fs *c)
 {
-       mutex_lock(&c->state_lock);
-       if (c->state != BCH_FS_STARTING &&
-           c->state != BCH_FS_RW)
-               goto out;
+       if (!test_bit(BCH_FS_rw, &c->flags)) {
+               bch2_journal_reclaim_stop(&c->journal);
+               return;
+       }
 
-       if (test_bit(BCH_FS_ERROR, &c->flags))
-               goto out;
+       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:
-        *
-        * (This is really blocking new _allocations_, writes to previously
-        * allocated space can still happen until stopping the allocator in
-        * bch2_dev_allocator_stop()).
         */
+       set_bit(BCH_FS_going_ro, &c->flags);
+#ifndef BCH_WRITE_REF_DEBUG
        percpu_ref_kill(&c->writes);
-
-       del_timer(&c->foreground_write_wakeup);
-       cancel_delayed_work(&c->pd_controllers_update);
-
-       c->foreground_write_pd.rate.rate = UINT_MAX;
-       bch2_wake_delayed_writes((unsigned long) c);
+#else
+       for (unsigned i = 0; i < BCH_WRITE_REF_NR; i++)
+               bch2_write_ref_put(c, i);
+#endif
 
        /*
         * If we're not doing an emergency shutdown, we want to wait on
@@ -264,28 +327,43 @@ void bch2_fs_read_only(struct bch_fs *c)
         * we do need to wait on them before returning and signalling
         * that going RO is complete:
         */
-       wait_event(bch_read_only_wait,
-                  test_bit(BCH_FS_WRITE_DISABLE_COMPLETE, &c->flags) ||
-                  test_bit(BCH_FS_EMERGENCY_RO, &c->flags));
+       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(bch_read_only_wait,
-                  test_bit(BCH_FS_WRITE_DISABLE_COMPLETE, &c->flags));
+       wait_event(bch2_read_only_wait,
+                  test_bit(BCH_FS_write_disable_complete, &c->flags));
 
-       clear_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)) {
-               mutex_lock(&c->sb_lock);
-               SET_BCH_SB_CLEAN(c->disk_sb, true);
-               bch2_write_super(c);
-               mutex_unlock(&c->sb_lock);
+           !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->opts.norecovery) {
+               BUG_ON(c->journal.last_empty_seq != journal_cur_seq(&c->journal));
+               BUG_ON(atomic_read(&c->btree_cache.dirty));
+               BUG_ON(atomic_long_read(&c->btree_key_cache.nr_dirty));
+               BUG_ON(c->btree_write_buffer.inc.keys.nr);
+               BUG_ON(c->btree_write_buffer.flushing.keys.nr);
+
+               bch_verbose(c, "marking filesystem clean");
+               bch2_fs_mark_clean(c);
+       } else {
+               bch_verbose(c, "done going read-only, filesystem not clean");
        }
-
-       c->state = BCH_FS_RO;
-out:
-       mutex_unlock(&c->state_lock);
 }
 
 static void bch2_fs_read_only_work(struct work_struct *work)
@@ -293,7 +371,9 @@ static void bch2_fs_read_only_work(struct work_struct *work)
        struct bch_fs *c =
                container_of(work, struct bch_fs, read_only_work);
 
+       down_write(&c->state_lock);
        bch2_fs_read_only(c);
+       up_write(&c->state_lock);
 }
 
 static void bch2_fs_read_only_async(struct bch_fs *c)
@@ -303,128 +383,226 @@ static void bch2_fs_read_only_async(struct bch_fs *c)
 
 bool bch2_fs_emergency_read_only(struct bch_fs *c)
 {
-       bool ret = !test_and_set_bit(BCH_FS_EMERGENCY_RO, &c->flags);
+       bool ret = !test_and_set_bit(BCH_FS_emergency_ro, &c->flags);
 
-       bch2_fs_read_only_async(c);
        bch2_journal_halt(&c->journal);
+       bch2_fs_read_only_async(c);
 
-       wake_up(&bch_read_only_wait);
+       wake_up(&bch2_read_only_wait);
        return ret;
 }
 
-const char *bch2_fs_read_write(struct bch_fs *c)
+static int bch2_fs_read_write_late(struct bch_fs *c)
 {
-       struct bch_dev *ca;
-       const char *err = NULL;
-       unsigned i;
+       int ret;
 
-       mutex_lock(&c->state_lock);
-       if (c->state != BCH_FS_STARTING &&
-           c->state != BCH_FS_RO)
-               goto out;
+       /*
+        * Data move operations can't run until after check_snapshots has
+        * completed, and bch2_snapshot_is_ancestor() is available.
+        *
+        * Ideally we'd start copygc/rebalance earlier instead of waiting for
+        * all of recovery/fsck to complete:
+        */
+       ret = bch2_copygc_start(c);
+       if (ret) {
+               bch_err(c, "error starting copygc thread");
+               return ret;
+       }
 
-       err = "error starting allocator thread";
-       for_each_rw_member(ca, c, i)
-               if (bch2_dev_allocator_start(ca)) {
-                       percpu_ref_put(&ca->io_ref);
-                       goto err;
-               }
+       ret = bch2_rebalance_start(c);
+       if (ret) {
+               bch_err(c, "error starting rebalance thread");
+               return ret;
+       }
 
-       err = "error starting btree GC thread";
-       if (bch2_gc_thread_start(c))
-               goto err;
+       return 0;
+}
 
-       err = "error starting moving GC thread";
-       for_each_rw_member(ca, c, i)
-               if (bch2_moving_gc_start(ca)) {
-                       percpu_ref_put(&ca->io_ref);
-                       goto err;
-               }
+static int __bch2_fs_read_write(struct bch_fs *c, bool early)
+{
+       int ret;
+
+       if (test_bit(BCH_FS_initial_gc_unfixed, &c->flags)) {
+               bch_err(c, "cannot go rw, unfixed btree errors");
+               return -BCH_ERR_erofs_unfixed_errors;
+       }
 
-       err = "error starting tiering thread";
-       if (bch2_tiering_start(c))
+       if (test_bit(BCH_FS_rw, &c->flags))
+               return 0;
+
+       bch_info(c, "going read-write");
+
+       ret = bch2_sb_members_v2_init(c);
+       if (ret)
                goto err;
 
-       schedule_delayed_work(&c->pd_controllers_update, 5 * HZ);
+       ret = bch2_fs_mark_dirty(c);
+       if (ret)
+               goto err;
 
-       if (c->state != BCH_FS_STARTING)
-               percpu_ref_reinit(&c->writes);
+       clear_bit(BCH_FS_clean_shutdown, &c->flags);
 
-       c->state = BCH_FS_RW;
-       err = NULL;
-out:
-       mutex_unlock(&c->state_lock);
-       return err;
+       /*
+        * 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:
+        */
+       set_bit(JOURNAL_NEED_FLUSH_WRITE, &c->journal.flags);
+
+       for_each_rw_member(c, ca)
+               bch2_dev_allocator_add(c, ca);
+       bch2_recalc_capacity(c);
+
+       set_bit(BCH_FS_rw, &c->flags);
+       set_bit(BCH_FS_was_rw, &c->flags);
+
+#ifndef BCH_WRITE_REF_DEBUG
+       percpu_ref_reinit(&c->writes);
+#else
+       for (unsigned i = 0; i < BCH_WRITE_REF_NR; i++) {
+               BUG_ON(atomic_long_read(&c->writes[i]));
+               atomic_long_inc(&c->writes[i]);
+       }
+#endif
+
+       ret = bch2_gc_thread_start(c);
+       if (ret) {
+               bch_err(c, "error starting gc thread");
+               return ret;
+       }
+
+       ret = bch2_journal_reclaim_start(&c->journal);
+       if (ret)
+               goto err;
+
+       if (!early) {
+               ret = bch2_fs_read_write_late(c);
+               if (ret)
+                       goto err;
+       }
+
+       bch2_do_discards(c);
+       bch2_do_invalidates(c);
+       bch2_do_stripe_deletes(c);
+       bch2_do_pending_node_rewrites(c);
+       return 0;
 err:
-       __bch2_fs_read_only(c);
-       goto out;
+       if (test_bit(BCH_FS_rw, &c->flags))
+               bch2_fs_read_only(c);
+       else
+               __bch2_fs_read_only(c);
+       return ret;
+}
+
+int bch2_fs_read_write(struct bch_fs *c)
+{
+       if (c->opts.norecovery)
+               return -BCH_ERR_erofs_norecovery;
+
+       if (c->opts.nochanges)
+               return -BCH_ERR_erofs_nochanges;
+
+       return __bch2_fs_read_write(c, false);
+}
+
+int bch2_fs_read_write_early(struct bch_fs *c)
+{
+       lockdep_assert_held(&c->state_lock);
+
+       return __bch2_fs_read_write(c, true);
 }
 
 /* Filesystem startup/shutdown: */
 
-static void bch2_fs_free(struct bch_fs *c)
+static void __bch2_fs_free(struct bch_fs *c)
 {
+       unsigned i;
+
+       for (i = 0; i < BCH_TIME_STAT_NR; i++)
+               bch2_time_stats_exit(&c->times[i]);
+
+       bch2_free_pending_node_rewrites(c);
+       bch2_fs_sb_errors_exit(c);
+       bch2_fs_counters_exit(c);
+       bch2_fs_snapshots_exit(c);
+       bch2_fs_quota_exit(c);
+       bch2_fs_fs_io_direct_exit(c);
+       bch2_fs_fs_io_buffered_exit(c);
+       bch2_fs_fsio_exit(c);
+       bch2_fs_ec_exit(c);
        bch2_fs_encryption_exit(c);
-       bch2_fs_btree_exit(c);
+       bch2_fs_nocow_locking_exit(c);
+       bch2_fs_io_write_exit(c);
+       bch2_fs_io_read_exit(c);
+       bch2_fs_buckets_waiting_for_journal_exit(c);
+       bch2_fs_btree_interior_update_exit(c);
+       bch2_fs_btree_iter_exit(c);
+       bch2_fs_btree_key_cache_exit(&c->btree_key_cache);
+       bch2_fs_btree_cache_exit(c);
+       bch2_fs_replicas_exit(c);
        bch2_fs_journal_exit(&c->journal);
        bch2_io_clock_exit(&c->io_clock[WRITE]);
        bch2_io_clock_exit(&c->io_clock[READ]);
        bch2_fs_compress_exit(c);
-       bdi_destroy(&c->bdi);
-       lg_lock_free(&c->usage_lock);
-       free_percpu(c->usage_percpu);
+       bch2_journal_keys_put_initial(c);
+       BUG_ON(atomic_read(&c->journal_keys.ref));
+       bch2_fs_btree_write_buffer_exit(c);
+       percpu_free_rwsem(&c->mark_lock);
+       free_percpu(c->online_reserved);
+
+       darray_exit(&c->btree_roots_extra);
+       free_percpu(c->pcpu);
+       mempool_exit(&c->large_bkey_pool);
        mempool_exit(&c->btree_bounce_pool);
-       mempool_exit(&c->bio_bounce_pages);
-       bioset_exit(&c->bio_write);
-       bioset_exit(&c->bio_read_split);
-       bioset_exit(&c->bio_read);
-       bioset_exit(&c->btree_read_bio);
-       mempool_exit(&c->btree_interior_update_pool);
-       mempool_exit(&c->btree_reserve_pool);
+       bioset_exit(&c->btree_bio);
        mempool_exit(&c->fill_iter);
+#ifndef BCH_WRITE_REF_DEBUG
        percpu_ref_exit(&c->writes);
-
+#endif
+       kfree(rcu_dereference_protected(c->disk_groups, 1));
+       kfree(c->journal_seq_blacklist_table);
+       kfree(c->unused_inode_hints);
+
+       if (c->write_ref_wq)
+               destroy_workqueue(c->write_ref_wq);
+       if (c->io_complete_wq)
+               destroy_workqueue(c->io_complete_wq);
        if (c->copygc_wq)
                destroy_workqueue(c->copygc_wq);
-       if (c->wq)
-               destroy_workqueue(c->wq);
+       if (c->btree_io_complete_wq)
+               destroy_workqueue(c->btree_io_complete_wq);
+       if (c->btree_update_wq)
+               destroy_workqueue(c->btree_update_wq);
 
-       free_pages((unsigned long) c->disk_sb, c->disk_sb_order);
-       kfree(c);
+       bch2_free_super(&c->disk_sb);
+       kvpfree(c, sizeof(*c));
        module_put(THIS_MODULE);
 }
 
-static void bch2_fs_exit(struct bch_fs *c)
+static void bch2_fs_release(struct kobject *kobj)
 {
-       unsigned i;
-
-       del_timer_sync(&c->foreground_write_wakeup);
-       cancel_delayed_work_sync(&c->pd_controllers_update);
-       cancel_work_sync(&c->read_only_work);
-       cancel_work_sync(&c->read_retry_work);
-
-       for (i = 0; i < c->sb.nr_devices; i++)
-               if (c->devs[i])
-                       bch2_dev_free(c->devs[i]);
+       struct bch_fs *c = container_of(kobj, struct bch_fs, kobj);
 
-       closure_debug_destroy(&c->cl);
-       kobject_put(&c->kobj);
+       __bch2_fs_free(c);
 }
 
-static void bch2_fs_offline(struct bch_fs *c)
+void __bch2_fs_stop(struct bch_fs *c)
 {
-       struct bch_dev *ca;
-       unsigned i;
+       bch_verbose(c, "shutting down");
 
-       mutex_lock(&bch_fs_list_lock);
-       list_del(&c->list);
-       mutex_unlock(&bch_fs_list_lock);
+       set_bit(BCH_FS_stopping, &c->flags);
+
+       cancel_work_sync(&c->journal_seq_blacklist_gc_work);
+
+       down_write(&c->state_lock);
+       bch2_fs_read_only(c);
+       up_write(&c->state_lock);
 
-       for_each_member_device(ca, c, i)
+       for_each_member_device(c, ca)
                if (ca->kobj.state_in_sysfs &&
                    ca->disk_sb.bdev)
-                       sysfs_remove_link(&part_to_dev(ca->disk_sb.bdev->bd_part)->kobj,
-                                         "bcachefs");
+                       sysfs_remove_link(bdev_kobj(ca->disk_sb.bdev), "bcachefs");
 
        if (c->kobj.state_in_sysfs)
                kobject_del(&c->kobj);
@@ -432,517 +610,534 @@ static void bch2_fs_offline(struct bch_fs *c)
        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);
        kobject_put(&c->opts_dir);
        kobject_put(&c->internal);
 
-       __bch2_fs_read_only(c);
+       /* btree prefetch might have kicked off reads in the background: */
+       bch2_btree_flush_all_reads(c);
+
+       for_each_member_device(c, ca)
+               cancel_work_sync(&ca->io_error_work);
+
+       cancel_work_sync(&c->read_only_work);
 }
 
-static void bch2_fs_release(struct kobject *kobj)
+void bch2_fs_free(struct bch_fs *c)
 {
-       struct bch_fs *c = container_of(kobj, struct bch_fs, kobj);
+       unsigned i;
 
-       bch2_fs_free(c);
+       mutex_lock(&bch_fs_list_lock);
+       list_del(&c->list);
+       mutex_unlock(&bch_fs_list_lock);
+
+       closure_sync(&c->cl);
+       closure_debug_destroy(&c->cl);
+
+       for (i = 0; i < c->sb.nr_devices; i++) {
+               struct bch_dev *ca = rcu_dereference_protected(c->devs[i], true);
+
+               if (ca) {
+                       bch2_free_super(&ca->disk_sb);
+                       bch2_dev_free(ca);
+               }
+       }
+
+       bch_verbose(c, "shutdown complete");
+
+       kobject_put(&c->kobj);
 }
 
 void bch2_fs_stop(struct bch_fs *c)
 {
-       mutex_lock(&c->state_lock);
-       BUG_ON(c->state == BCH_FS_STOPPING);
-       c->state = BCH_FS_STOPPING;
-       mutex_unlock(&c->state_lock);
+       __bch2_fs_stop(c);
+       bch2_fs_free(c);
+}
 
-       bch2_fs_offline(c);
+static int bch2_fs_online(struct bch_fs *c)
+{
+       int ret = 0;
 
-       closure_sync(&c->cl);
+       lockdep_assert_held(&bch_fs_list_lock);
 
-       bch2_fs_exit(c);
-}
+       if (__bch2_uuid_to_fs(c->sb.uuid)) {
+               bch_err(c, "filesystem UUID already open");
+               return -EINVAL;
+       }
+
+       ret = bch2_fs_chardev_init(c);
+       if (ret) {
+               bch_err(c, "error creating character device");
+               return ret;
+       }
+
+       bch2_fs_debug_init(c);
+
+       ret = kobject_add(&c->kobj, NULL, "%pU", c->sb.user_uuid.b) ?:
+           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") ?:
+#endif
+           kobject_add(&c->counters_kobj, &c->kobj, "counters") ?:
+           bch2_opts_create_sysfs_files(&c->opts_dir);
+       if (ret) {
+               bch_err(c, "error creating sysfs objects");
+               return ret;
+       }
+
+       down_write(&c->state_lock);
 
-#define alloc_bucket_pages(gfp, ca)                    \
-       ((void *) __get_free_pages(__GFP_ZERO|gfp, ilog2(bucket_pages(ca))))
+       for_each_member_device(c, ca) {
+               ret = bch2_dev_sysfs_online(c, ca);
+               if (ret) {
+                       bch_err(c, "error creating sysfs objects");
+                       percpu_ref_put(&ca->ref);
+                       goto err;
+               }
+       }
+
+       BUG_ON(!list_empty(&c->list));
+       list_add(&c->list, &bch_fs_list);
+err:
+       up_write(&c->state_lock);
+       return ret;
+}
 
 static struct bch_fs *bch2_fs_alloc(struct bch_sb *sb, struct bch_opts opts)
 {
-       struct bch_sb_field_members *mi;
        struct bch_fs *c;
-       unsigned i, iter_size, journal_entry_bytes;
+       struct printbuf name = PRINTBUF;
+       unsigned i, iter_size;
+       int ret = 0;
 
-       c = kzalloc(sizeof(struct bch_fs), GFP_KERNEL);
-       if (!c)
-               return NULL;
+       c = kvpmalloc(sizeof(struct bch_fs), GFP_KERNEL|__GFP_ZERO);
+       if (!c) {
+               c = ERR_PTR(-BCH_ERR_ENOMEM_fs_alloc);
+               goto out;
+       }
+
+       c->stdio = (void *)(unsigned long) opts.stdio;
 
        __module_get(THIS_MODULE);
 
+       closure_init(&c->cl, NULL);
+
+       c->kobj.kset = bcachefs_kset;
+       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->counters_kobj, &bch2_fs_counters_ktype);
+
        c->minor                = -1;
+       c->disk_sb.fs_sb        = true;
 
-       mutex_init(&c->state_lock);
+       init_rwsem(&c->state_lock);
        mutex_init(&c->sb_lock);
-       mutex_init(&c->btree_cache_lock);
-       mutex_init(&c->bucket_lock);
+       mutex_init(&c->replicas_gc_lock);
        mutex_init(&c->btree_root_lock);
        INIT_WORK(&c->read_only_work, bch2_fs_read_only_work);
 
-       init_rwsem(&c->gc_lock);
-
-#define BCH_TIME_STAT(name, frequency_units, duration_units)           \
-       spin_lock_init(&c->name##_time.lock);
-       BCH_TIME_STATS()
-#undef BCH_TIME_STAT
+       refcount_set(&c->ro_ref, 1);
+       init_waitqueue_head(&c->ro_ref_wait);
+       sema_init(&c->online_fsck_mutex, 1);
 
-       bch2_fs_allocator_init(c);
-       bch2_fs_tiering_init(c);
+       init_rwsem(&c->gc_lock);
+       mutex_init(&c->gc_gens_lock);
+       atomic_set(&c->journal_keys.ref, 1);
+       c->journal_keys.initial_ref_held = true;
+
+       for (i = 0; i < BCH_TIME_STAT_NR; i++)
+               bch2_time_stats_init(&c->times[i]);
+
+       bch2_fs_copygc_init(c);
+       bch2_fs_btree_key_cache_init_early(&c->btree_key_cache);
+       bch2_fs_btree_iter_init_early(c);
+       bch2_fs_btree_interior_update_init_early(c);
+       bch2_fs_allocator_background_init(c);
+       bch2_fs_allocator_foreground_init(c);
+       bch2_fs_rebalance_init(c);
+       bch2_fs_quota_init(c);
+       bch2_fs_ec_init_early(c);
+       bch2_fs_move_init(c);
+       bch2_fs_sb_errors_init_early(c);
 
        INIT_LIST_HEAD(&c->list);
-       INIT_LIST_HEAD(&c->btree_cache);
-       INIT_LIST_HEAD(&c->btree_cache_freeable);
-       INIT_LIST_HEAD(&c->btree_cache_freed);
 
-       INIT_LIST_HEAD(&c->btree_interior_update_list);
-       mutex_init(&c->btree_reserve_cache_lock);
-       mutex_init(&c->btree_interior_update_lock);
+       mutex_init(&c->usage_scratch_lock);
 
        mutex_init(&c->bio_bounce_pages_lock);
-       bio_list_init(&c->read_retry_list);
-       spin_lock_init(&c->read_retry_lock);
-       INIT_WORK(&c->read_retry_work, bch2_read_retry_work);
-       mutex_init(&c->zlib_workspace_lock);
+       mutex_init(&c->snapshot_table_lock);
+       init_rwsem(&c->snapshot_create_lock);
+
+       spin_lock_init(&c->btree_write_error_lock);
+
+       INIT_WORK(&c->journal_seq_blacklist_gc_work,
+                 bch2_blacklist_entries_gc);
+
+       INIT_LIST_HEAD(&c->journal_iters);
+
+       INIT_LIST_HEAD(&c->fsck_error_msgs);
+       mutex_init(&c->fsck_error_msgs_lock);
 
        seqcount_init(&c->gc_pos_lock);
 
-       c->prio_clock[READ].hand = 1;
-       c->prio_clock[READ].min_prio = 0;
-       c->prio_clock[WRITE].hand = 1;
-       c->prio_clock[WRITE].min_prio = 0;
+       seqcount_init(&c->usage_lock);
 
-       init_waitqueue_head(&c->writeback_wait);
-       c->writeback_pages_max = (256 << 10) / PAGE_SIZE;
+       sema_init(&c->io_in_flight, 128);
 
-       c->copy_gc_enabled = 1;
-       c->tiering_enabled = 1;
-       c->tiering_percent = 10;
+       INIT_LIST_HEAD(&c->vfs_inodes_list);
+       mutex_init(&c->vfs_inodes_lock);
 
-       c->foreground_target_percent = 20;
+       c->copy_gc_enabled              = 1;
+       c->rebalance.enabled            = 1;
+       c->promote_whole_extents        = true;
 
-       c->journal.write_time   = &c->journal_write_time;
-       c->journal.delay_time   = &c->journal_delay_time;
-       c->journal.blocked_time = &c->journal_blocked_time;
-       c->journal.flush_seq_time = &c->journal_flush_seq_time;
+       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];
 
-       mutex_lock(&c->sb_lock);
+       bch2_fs_btree_cache_init_early(&c->btree_cache);
 
-       if (bch2_sb_to_fs(c, sb)) {
-               mutex_unlock(&c->sb_lock);
+       mutex_init(&c->sectors_available_lock);
+
+       ret = percpu_init_rwsem(&c->mark_lock);
+       if (ret)
                goto err;
-       }
 
+       mutex_lock(&c->sb_lock);
+       ret = bch2_sb_to_fs(c, sb);
        mutex_unlock(&c->sb_lock);
 
-       scnprintf(c->name, sizeof(c->name), "%pU", &c->sb.user_uuid);
+       if (ret)
+               goto err;
+
+       pr_uuid(&name, c->sb.user_uuid.b);
+       strscpy(c->name, name.buf, sizeof(c->name));
+       printbuf_exit(&name);
 
-       bch2_opts_apply(&c->opts, bch2_sb_opts(sb));
-       bch2_opts_apply(&c->opts, opts);
+       ret = name.allocation_failure ? -BCH_ERR_ENOMEM_fs_name_alloc : 0;
+       if (ret)
+               goto err;
 
-       c->opts.nochanges       |= c->opts.noreplay;
-       c->opts.read_only       |= c->opts.nochanges;
+       /* Compat: */
+       if (le16_to_cpu(sb->version) <= bcachefs_metadata_version_inode_v2 &&
+           !BCH_SB_JOURNAL_FLUSH_DELAY(sb))
+               SET_BCH_SB_JOURNAL_FLUSH_DELAY(sb, 1000);
 
-       c->block_bits           = ilog2(c->sb.block_size);
+       if (le16_to_cpu(sb->version) <= bcachefs_metadata_version_inode_v2 &&
+           !BCH_SB_JOURNAL_RECLAIM_DELAY(sb))
+               SET_BCH_SB_JOURNAL_RECLAIM_DELAY(sb, 100);
 
-       if (bch2_fs_init_fault("fs_alloc"))
+       c->opts = bch2_opts_default;
+       ret = bch2_opts_from_sb(&c->opts, sb);
+       if (ret)
                goto err;
 
-       iter_size = (btree_blocks(c) + 1) * 2 *
-               sizeof(struct btree_node_iter_set);
+       bch2_opts_apply(&c->opts, opts);
+
+       c->btree_key_cache_btrees |= 1U << BTREE_ID_alloc;
+       if (c->opts.inodes_use_key_cache)
+               c->btree_key_cache_btrees |= 1U << BTREE_ID_inodes;
+       c->btree_key_cache_btrees |= 1U << BTREE_ID_logged_ops;
+
+       c->block_bits           = ilog2(block_sectors(c));
+       c->btree_foreground_merge_threshold = BTREE_FOREGROUND_MERGE_THRESHOLD(c);
 
-       journal_entry_bytes = 512U << BCH_SB_JOURNAL_ENTRY_SIZE(sb);
+       if (bch2_fs_init_fault("fs_alloc")) {
+               bch_err(c, "fs_alloc fault injected");
+               ret = -EFAULT;
+               goto err;
+       }
 
-       if (!(c->wq = alloc_workqueue("bcachefs",
-                               WQ_FREEZABLE|WQ_MEM_RECLAIM|WQ_HIGHPRI, 1)) ||
-           !(c->copygc_wq = alloc_workqueue("bcache_copygc",
-                               WQ_FREEZABLE|WQ_MEM_RECLAIM|WQ_HIGHPRI, 1)) ||
-           percpu_ref_init(&c->writes, bch2_writes_disabled, 0, GFP_KERNEL) ||
-           mempool_init_kmalloc_pool(&c->btree_reserve_pool, 1,
-                                     sizeof(struct btree_reserve)) ||
-           mempool_init_kmalloc_pool(&c->btree_interior_update_pool, 1,
-                                     sizeof(struct btree_interior_update)) ||
+       iter_size = sizeof(struct sort_iter) +
+               (btree_blocks(c) + 1) * 2 *
+               sizeof(struct sort_iter_set);
+
+       c->inode_shard_bits = ilog2(roundup_pow_of_two(num_possible_cpus()));
+
+       if (!(c->btree_update_wq = alloc_workqueue("bcachefs",
+                               WQ_FREEZABLE|WQ_UNBOUND|WQ_MEM_RECLAIM, 512)) ||
+           !(c->btree_io_complete_wq = alloc_workqueue("bcachefs_btree_io",
+                               WQ_FREEZABLE|WQ_MEM_RECLAIM, 1)) ||
+           !(c->copygc_wq = alloc_workqueue("bcachefs_copygc",
+                               WQ_FREEZABLE|WQ_MEM_RECLAIM|WQ_CPU_INTENSIVE, 1)) ||
+           !(c->io_complete_wq = alloc_workqueue("bcachefs_io",
+                               WQ_FREEZABLE|WQ_HIGHPRI|WQ_MEM_RECLAIM, 512)) ||
+           !(c->write_ref_wq = alloc_workqueue("bcachefs_write_ref",
+                               WQ_FREEZABLE, 0)) ||
+#ifndef BCH_WRITE_REF_DEBUG
+           percpu_ref_init(&c->writes, bch2_writes_disabled,
+                           PERCPU_REF_INIT_DEAD, GFP_KERNEL) ||
+#endif
            mempool_init_kmalloc_pool(&c->fill_iter, 1, iter_size) ||
-           bioset_init(&c->btree_read_bio, 1, 0) ||
-           bioset_init(&c->bio_read, 1, offsetof(struct bch_read_bio, bio)) ||
-           bioset_init(&c->bio_read_split, 1, offsetof(struct bch_read_bio, bio)) ||
-           bioset_init(&c->bio_write, 1, offsetof(struct bch_write_bio, bio)) ||
-           mempool_init_page_pool(&c->bio_bounce_pages,
-                                  max_t(unsigned,
-                                        c->sb.btree_node_size,
-                                        BCH_ENCODED_EXTENT_MAX) /
-                                  PAGE_SECTORS, 0) ||
-           !(c->usage_percpu = alloc_percpu(struct bch_fs_usage)) ||
-           lg_lock_init(&c->usage_lock) ||
-           mempool_init_page_pool(&c->btree_bounce_pool, 1,
-                                  ilog2(btree_pages(c))) ||
-           bdi_setup_and_register(&c->bdi, "bcachefs") ||
-           bch2_io_clock_init(&c->io_clock[READ]) ||
-           bch2_io_clock_init(&c->io_clock[WRITE]) ||
-           bch2_fs_journal_init(&c->journal, journal_entry_bytes) ||
-           bch2_fs_btree_init(c) ||
-           bch2_fs_encryption_init(c) ||
-           bch2_fs_compress_init(c) ||
-           bch2_check_set_has_compressed_data(c, c->opts.compression))
+           bioset_init(&c->btree_bio, 1,
+                       max(offsetof(struct btree_read_bio, bio),
+                           offsetof(struct btree_write_bio, wbio.bio)),
+                       BIOSET_NEED_BVECS) ||
+           !(c->pcpu = alloc_percpu(struct bch_fs_pcpu)) ||
+           !(c->online_reserved = alloc_percpu(u64)) ||
+           mempool_init_kvpmalloc_pool(&c->btree_bounce_pool, 1,
+                                       btree_bytes(c)) ||
+           mempool_init_kmalloc_pool(&c->large_bkey_pool, 1, 2048) ||
+           !(c->unused_inode_hints = kcalloc(1U << c->inode_shard_bits,
+                                             sizeof(u64), GFP_KERNEL))) {
+               ret = -BCH_ERR_ENOMEM_fs_other_alloc;
                goto err;
+       }
 
-       c->bdi.ra_pages         = VM_MAX_READAHEAD * 1024 / PAGE_SIZE;
-       c->bdi.congested_fn     = bch2_congested_fn;
-       c->bdi.congested_data   = c;
+       ret = bch2_fs_counters_init(c) ?:
+           bch2_fs_sb_errors_init(c) ?:
+           bch2_io_clock_init(&c->io_clock[READ]) ?:
+           bch2_io_clock_init(&c->io_clock[WRITE]) ?:
+           bch2_fs_journal_init(&c->journal) ?:
+           bch2_fs_replicas_init(c) ?:
+           bch2_fs_btree_cache_init(c) ?:
+           bch2_fs_btree_key_cache_init(&c->btree_key_cache) ?:
+           bch2_fs_btree_iter_init(c) ?:
+           bch2_fs_btree_interior_update_init(c) ?:
+           bch2_fs_buckets_waiting_for_journal_init(c) ?:
+           bch2_fs_btree_write_buffer_init(c) ?:
+           bch2_fs_subvolumes_init(c) ?:
+           bch2_fs_io_read_init(c) ?:
+           bch2_fs_io_write_init(c) ?:
+           bch2_fs_nocow_locking_init(c) ?:
+           bch2_fs_encryption_init(c) ?:
+           bch2_fs_compress_init(c) ?:
+           bch2_fs_ec_init(c) ?:
+           bch2_fs_fsio_init(c) ?:
+           bch2_fs_fs_io_buffered_init(c) ?:
+           bch2_fs_fs_io_direct_init(c);
+       if (ret)
+               goto err;
 
-       mi = bch2_sb_get_members(c->disk_sb);
        for (i = 0; i < c->sb.nr_devices; i++)
-               if (!bch2_is_zero(mi->members[i].uuid.b, sizeof(uuid_le)) &&
-                   bch2_dev_alloc(c, i))
+               if (bch2_dev_exists(c->disk_sb.sb, i) &&
+                   bch2_dev_alloc(c, i)) {
+                       ret = -EEXIST;
                        goto err;
+               }
 
-       /*
-        * Now that all allocations have succeeded, init various refcounty
-        * things that let us shutdown:
-        */
-       closure_init(&c->cl, NULL);
+       bch2_journal_entry_res_resize(&c->journal,
+                       &c->btree_root_journal_res,
+                       BTREE_ID_NR * (JSET_KEYS_U64s + BKEY_BTREE_PTR_U64s_MAX));
+       bch2_dev_usage_journal_reserve(c);
+       bch2_journal_entry_res_resize(&c->journal,
+                       &c->clock_journal_res,
+                       (sizeof(struct jset_entry_clock) / sizeof(u64)) * 2);
 
-       c->kobj.kset = bcachefs_kset;
-       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);
+       mutex_lock(&bch_fs_list_lock);
+       ret = bch2_fs_online(c);
+       mutex_unlock(&bch_fs_list_lock);
+
+       if (ret)
+               goto err;
+out:
        return c;
 err:
        bch2_fs_free(c);
-       return NULL;
+       c = ERR_PTR(ret);
+       goto out;
 }
 
-static const char *__bch2_fs_online(struct bch_fs *c)
+noinline_for_stack
+static void print_mount_opts(struct bch_fs *c)
 {
-       struct bch_dev *ca;
-       const char *err = NULL;
-       unsigned i;
-       int ret;
+       enum bch_opt_id i;
+       struct printbuf p = PRINTBUF;
+       bool first = true;
 
-       lockdep_assert_held(&bch_fs_list_lock);
+       prt_str(&p, "mounting version ");
+       bch2_version_to_text(&p, c->sb.version);
 
-       if (!list_empty(&c->list))
-               return NULL;
-
-       if (__bch2_uuid_to_fs(c->sb.uuid))
-               return "filesystem UUID already open";
-
-       ret = bch2_fs_chardev_init(c);
-       if (ret)
-               return "error creating character device";
+       if (c->opts.read_only) {
+               prt_str(&p, " opts=");
+               first = false;
+               prt_printf(&p, "ro");
+       }
 
-       bch2_fs_debug_init(c);
+       for (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 (kobject_add(&c->kobj, NULL, "%pU", c->sb.user_uuid.b) ||
-           kobject_add(&c->internal, &c->kobj, "internal") ||
-           kobject_add(&c->opts_dir, &c->kobj, "options") ||
-           kobject_add(&c->time_stats, &c->kobj, "time_stats"))
-               return "error creating sysfs objects";
+               if (!(opt->flags & OPT_MOUNT))
+                       continue;
 
-       mutex_lock(&c->state_lock);
+               if (v == bch2_opt_get_by_id(&bch2_opts_default, i))
+                       continue;
 
-       err = "error creating sysfs objects";
-       __for_each_member_device(ca, c, i)
-               if (bch2_dev_sysfs_online(ca))
-                       goto err;
+               prt_str(&p, first ? " opts=" : ",");
+               first = false;
+               bch2_opt_to_text(&p, c, c->disk_sb.sb, opt, v, OPT_SHOW_MOUNT_STYLE);
+       }
 
-       list_add(&c->list, &bch_fs_list);
-       err = NULL;
-err:
-       mutex_unlock(&c->state_lock);
-       return err;
+       bch_info(c, "%s", p.buf);
+       printbuf_exit(&p);
 }
 
-static const char *bch2_fs_online(struct bch_fs *c)
+int bch2_fs_start(struct bch_fs *c)
 {
-       const char *err;
-
-       mutex_lock(&bch_fs_list_lock);
-       err = __bch2_fs_online(c);
-       mutex_unlock(&bch_fs_list_lock);
+       time64_t now = ktime_get_real_seconds();
+       int ret;
 
-       return err;
-}
+       print_mount_opts(c);
 
-static const char *__bch2_fs_start(struct bch_fs *c)
-{
-       const char *err = "cannot allocate memory";
-       struct bch_sb_field_members *mi;
-       struct bch_dev *ca;
-       unsigned i, id;
-       time64_t now;
-       LIST_HEAD(journal);
-       struct jset *j;
-       int ret = -EINVAL;
+       down_write(&c->state_lock);
 
-       BUG_ON(c->state != BCH_FS_STARTING);
+       BUG_ON(test_bit(BCH_FS_started, &c->flags));
 
        mutex_lock(&c->sb_lock);
-       for_each_online_member(ca, c, i)
-               bch2_sb_from_fs(c, ca);
-       mutex_unlock(&c->sb_lock);
-
-       if (BCH_SB_INITIALIZED(c->disk_sb)) {
-               ret = bch2_journal_read(c, &journal);
-               if (ret)
-                       goto err;
-
-               j = &list_entry(journal.prev, struct journal_replay, list)->j;
-
-               c->prio_clock[READ].hand = le16_to_cpu(j->read_clock);
-               c->prio_clock[WRITE].hand = le16_to_cpu(j->write_clock);
-
-               err = "error reading priorities";
-               for_each_readable_member(ca, c, i) {
-                       ret = bch2_prio_read(ca);
-                       if (ret) {
-                               percpu_ref_put(&ca->io_ref);
-                               goto err;
-                       }
-               }
-
-               for (id = 0; id < BTREE_ID_NR; id++) {
-                       unsigned level;
-                       struct bkey_i *k;
-
-                       err = "bad btree root";
-                       k = bch2_journal_find_btree_root(c, j, id, &level);
-                       if (!k && id == BTREE_ID_EXTENTS)
-                               goto err;
-                       if (!k) {
-                               pr_debug("missing btree root: %d", id);
-                               continue;
-                       }
-
-                       err = "error reading btree root";
-                       if (bch2_btree_root_read(c, id, k, level))
-                               goto err;
-               }
-
-               bch_verbose(c, "starting mark and sweep:");
-
-               err = "error in recovery";
-               ret = bch2_initial_gc(c, &journal);
-               if (ret)
-                       goto err;
-
-               if (c->opts.noreplay)
-                       goto recovery_done;
-
-               bch_verbose(c, "mark and sweep done");
-
-               /*
-                * bch2_journal_start() can't happen sooner, or btree_gc_finish()
-                * will give spurious errors about oldest_gen > bucket_gen -
-                * this is a hack but oh well.
-                */
-               bch2_journal_start(c);
-
-               err = "error starting allocator thread";
-               for_each_rw_member(ca, c, i)
-                       if (bch2_dev_allocator_start(ca)) {
-                               percpu_ref_put(&ca->io_ref);
-                               goto err;
-                       }
-
-               bch_verbose(c, "starting journal replay:");
-
-               err = "journal replay failed";
-               ret = bch2_journal_replay(c, &journal);
-               if (ret)
-                       goto err;
-
-               bch_verbose(c, "journal replay done");
-
-               if (c->opts.norecovery)
-                       goto recovery_done;
-
-               bch_verbose(c, "starting fsck:");
-               err = "error in fsck";
-               ret = bch2_fsck(c, !c->opts.nofsck);
-               if (ret)
-                       goto err;
-
-               for_each_rw_member(ca, c, i)
-                       if (ca->need_prio_write) {
-                               ret = bch2_prio_write(ca);
-                               if (ret) {
-                                       percpu_ref_put(&ca->io_ref);
-                                       goto err;
-                               }
-                       }
-
-               bch_verbose(c, "fsck done");
-       } else {
-               struct bch_inode_unpacked inode;
-               struct bkey_inode_buf packed_inode;
-               struct closure cl;
-
-               closure_init_stack(&cl);
-
-               bch_notice(c, "initializing new filesystem");
-
-               ret = bch2_initial_gc(c, &journal);
-               if (ret)
-                       goto err;
-
-               err = "unable to allocate journal buckets";
-               for_each_rw_member(ca, c, i)
-                       if (bch2_dev_journal_alloc(ca)) {
-                               percpu_ref_put(&ca->io_ref);
-                               goto err;
-                       }
 
-               /*
-                * journal_res_get() will crash if called before this has
-                * set up the journal.pin FIFO and journal.cur pointer:
-                */
-               bch2_journal_start(c);
-               bch2_journal_set_replay_done(&c->journal);
-
-               err = "error starting allocator thread";
-               for_each_rw_member(ca, c, i)
-                       if (bch2_dev_allocator_start(ca)) {
-                               percpu_ref_put(&ca->io_ref);
-                               goto err;
-                       }
+       ret = bch2_sb_members_v2_init(c);
+       if (ret) {
+               mutex_unlock(&c->sb_lock);
+               goto err;
+       }
 
-               err = "cannot allocate new btree root";
-               for (id = 0; id < BTREE_ID_NR; id++)
-                       if (bch2_btree_root_alloc(c, id, &cl)) {
-                               closure_sync(&cl);
-                               goto err;
-                       }
+       for_each_online_member(c, ca)
+               bch2_members_v2_get_mut(c->disk_sb.sb, ca->dev_idx)->last_mount = cpu_to_le64(now);
 
-               /* Wait for new btree roots to be written: */
-               closure_sync(&cl);
+       mutex_unlock(&c->sb_lock);
 
-               bch2_inode_init(c, &inode, 0, 0,
-                              S_IFDIR|S_IRWXU|S_IRUGO|S_IXUGO, 0);
-               inode.inum = BCACHE_ROOT_INO;
+       for_each_rw_member(c, ca)
+               bch2_dev_allocator_add(c, ca);
+       bch2_recalc_capacity(c);
 
-               bch2_inode_pack(&packed_inode, &inode);
+       ret = BCH_SB_INITIALIZED(c->disk_sb.sb)
+               ? bch2_fs_recovery(c)
+               : bch2_fs_initialize(c);
+       if (ret)
+               goto err;
 
-               err = "error creating root directory";
-               if (bch2_btree_insert(c, BTREE_ID_INODES,
-                                    &packed_inode.inode.k_i,
-                                    NULL, NULL, NULL, 0))
-                       goto err;
+       ret = bch2_opts_check_may_set(c);
+       if (ret)
+               goto err;
 
-               err = "error writing first journal entry";
-               if (bch2_journal_meta(&c->journal))
-                       goto err;
-       }
-recovery_done:
-       err = "dynamic fault";
-       if (bch2_fs_init_fault("fs_start"))
+       if (bch2_fs_init_fault("fs_start")) {
+               bch_err(c, "fs_start fault injected");
+               ret = -EINVAL;
                goto err;
+       }
+
+       set_bit(BCH_FS_started, &c->flags);
 
        if (c->opts.read_only) {
                bch2_fs_read_only(c);
        } else {
-               err = bch2_fs_read_write(c);
-               if (err)
+               ret = !test_bit(BCH_FS_rw, &c->flags)
+                       ? bch2_fs_read_write(c)
+                       : bch2_fs_read_write_late(c);
+               if (ret)
                        goto err;
        }
 
-       mutex_lock(&c->sb_lock);
-       mi = bch2_sb_get_members(c->disk_sb);
-       now = ktime_get_seconds();
-
-       for_each_member_device(ca, c, i)
-               mi->members[ca->dev_idx].last_mount = cpu_to_le64(now);
-
-       SET_BCH_SB_INITIALIZED(c->disk_sb, true);
-       SET_BCH_SB_CLEAN(c->disk_sb, false);
-       c->disk_sb->version = BCACHE_SB_VERSION_CDEV;
-
-       bch2_write_super(c);
-       mutex_unlock(&c->sb_lock);
-
-       err = NULL;
-out:
-       bch2_journal_entries_free(&journal);
-       return err;
+       ret = 0;
 err:
-       switch (ret) {
-       case BCH_FSCK_ERRORS_NOT_FIXED:
-               bch_err(c, "filesystem contains errors: please report this to the developers");
-               pr_cont("mount with -o fix_errors to repair");
-               err = "fsck error";
-               break;
-       case BCH_FSCK_REPAIR_UNIMPLEMENTED:
-               bch_err(c, "filesystem contains errors: please report this to the developers");
-               pr_cont("repair unimplemented: inform the developers so that it can be added");
-               err = "fsck error";
-               break;
-       case BCH_FSCK_REPAIR_IMPOSSIBLE:
-               bch_err(c, "filesystem contains errors, but repair impossible");
-               err = "fsck error";
-               break;
-       case BCH_FSCK_UNKNOWN_VERSION:
-               err = "unknown metadata version";;
-               break;
-       case -ENOMEM:
-               err = "cannot allocate memory";
-               break;
-       case -EIO:
-               err = "IO error";
-               break;
-       }
-
-       BUG_ON(!err);
-       set_bit(BCH_FS_ERROR, &c->flags);
-       goto out;
-}
-
-const char *bch2_fs_start(struct bch_fs *c)
-{
-       return __bch2_fs_start(c) ?: bch2_fs_online(c);
+       if (ret)
+               bch_err_msg(c, ret, "starting filesystem");
+       else
+               bch_verbose(c, "done starting filesystem");
+       up_write(&c->state_lock);
+       return ret;
 }
 
-static const char *bch2_dev_may_add(struct bch_sb *sb, struct bch_fs *c)
+static int bch2_dev_may_add(struct bch_sb *sb, struct bch_fs *c)
 {
-       struct bch_sb_field_members *sb_mi;
+       struct bch_member m = bch2_sb_member_get(sb, sb->dev_idx);
 
-       sb_mi = bch2_sb_get_members(sb);
-       if (!sb_mi)
-               return "Invalid superblock: member info area missing";
+       if (le16_to_cpu(sb->block_size) != block_sectors(c))
+               return -BCH_ERR_mismatched_block_size;
 
-       if (le16_to_cpu(sb->block_size) != c->sb.block_size)
-               return "mismatched block size";
+       if (le16_to_cpu(m.bucket_size) <
+           BCH_SB_BTREE_NODE_SIZE(c->disk_sb.sb))
+               return -BCH_ERR_bucket_size_too_small;
 
-       if (le16_to_cpu(sb_mi->members[sb->dev_idx].bucket_size) <
-           BCH_SB_BTREE_NODE_SIZE(c->disk_sb))
-               return "new cache bucket size is too small";
-
-       return NULL;
+       return 0;
 }
 
-static const char *bch2_dev_in_fs(struct bch_sb *fs, struct bch_sb *sb)
+static int bch2_dev_in_fs(struct bch_sb_handle *fs,
+                         struct bch_sb_handle *sb)
 {
-       struct bch_sb *newest =
-               le64_to_cpu(fs->seq) > le64_to_cpu(sb->seq) ? fs : sb;
-       struct bch_sb_field_members *mi = bch2_sb_get_members(newest);
+       if (fs == sb)
+               return 0;
+
+       if (!uuid_equal(&fs->sb->uuid, &sb->sb->uuid))
+               return -BCH_ERR_device_not_a_member_of_filesystem;
 
-       if (uuid_le_cmp(fs->uuid, sb->uuid))
-               return "device not a member of filesystem";
+       if (!bch2_dev_exists(fs->sb, sb->sb->dev_idx))
+               return -BCH_ERR_device_has_been_removed;
 
-       if (sb->dev_idx >= newest->nr_devices)
-               return "device has invalid dev_idx";
+       if (fs->sb->block_size != sb->sb->block_size)
+               return -BCH_ERR_mismatched_block_size;
 
-       if (bch2_is_zero(mi->members[sb->dev_idx].uuid.b, sizeof(uuid_le)))
-               return "device has been removed";
+       if (le16_to_cpu(fs->sb->version) < bcachefs_metadata_version_member_seq ||
+           le16_to_cpu(sb->sb->version) < bcachefs_metadata_version_member_seq)
+               return 0;
 
-       if (fs->block_size != sb->block_size)
-               return "mismatched block size";
+       if (fs->sb->seq == sb->sb->seq &&
+           fs->sb->write_time != sb->sb->write_time) {
+               struct printbuf buf = PRINTBUF;
+
+               prt_str(&buf, "Split brain detected between ");
+               prt_bdevname(&buf, sb->bdev);
+               prt_str(&buf, " and ");
+               prt_bdevname(&buf, fs->bdev);
+               prt_char(&buf, ':');
+               prt_newline(&buf);
+               prt_printf(&buf, "seq=%llu but write_time different, got", le64_to_cpu(sb->sb->seq));
+               prt_newline(&buf);
+
+               prt_bdevname(&buf, fs->bdev);
+               prt_char(&buf, ' ');
+               bch2_prt_datetime(&buf, le64_to_cpu(fs->sb->write_time));;
+               prt_newline(&buf);
+
+               prt_bdevname(&buf, sb->bdev);
+               prt_char(&buf, ' ');
+               bch2_prt_datetime(&buf, le64_to_cpu(sb->sb->write_time));;
+               prt_newline(&buf);
+
+               prt_printf(&buf, "Not using older sb");
+
+               pr_err("%s", buf.buf);
+               printbuf_exit(&buf);
+               return -BCH_ERR_device_splitbrain;
+       }
 
-       return NULL;
+       struct bch_member m = bch2_sb_member_get(fs->sb, sb->sb->dev_idx);
+       u64 seq_from_fs         = le64_to_cpu(m.seq);
+       u64 seq_from_member     = le64_to_cpu(sb->sb->seq);
+
+       if (seq_from_fs && seq_from_fs < seq_from_member) {
+               struct printbuf buf = PRINTBUF;
+
+               prt_str(&buf, "Split brain detected between ");
+               prt_bdevname(&buf, sb->bdev);
+               prt_str(&buf, " and ");
+               prt_bdevname(&buf, fs->bdev);
+               prt_char(&buf, ':');
+               prt_newline(&buf);
+
+               prt_bdevname(&buf, fs->bdev);
+               prt_str(&buf, "believes seq of ");
+               prt_bdevname(&buf, sb->bdev);
+               prt_printf(&buf, " to be %llu, but ", seq_from_fs);
+               prt_bdevname(&buf, sb->bdev);
+               prt_printf(&buf, " has %llu\n", seq_from_member);
+               prt_str(&buf, "Not using ");
+               prt_bdevname(&buf, sb->bdev);
+
+               pr_err("%s", buf.buf);
+               printbuf_exit(&buf);
+               return -BCH_ERR_device_splitbrain;
+       }
+
+       return 0;
 }
 
 /* Device startup/shutdown: */
@@ -956,14 +1151,11 @@ static void bch2_dev_release(struct kobject *kobj)
 
 static void bch2_dev_free(struct bch_dev *ca)
 {
-       unsigned i;
-
        cancel_work_sync(&ca->io_error_work);
 
        if (ca->kobj.state_in_sysfs &&
            ca->disk_sb.bdev)
-               sysfs_remove_link(&part_to_dev(ca->disk_sb.bdev->bd_part)->kobj,
-                                 "bcachefs");
+               sysfs_remove_link(bdev_kobj(ca->disk_sb.bdev), "bcachefs");
 
        if (ca->kobj.state_in_sysfs)
                kobject_del(&ca->kobj);
@@ -971,49 +1163,35 @@ static void bch2_dev_free(struct bch_dev *ca)
        bch2_free_super(&ca->disk_sb);
        bch2_dev_journal_exit(ca);
 
-       free_percpu(ca->sectors_written);
+       free_percpu(ca->io_done);
        bioset_exit(&ca->replica_set);
-       free_percpu(ca->usage_percpu);
-       free_pages((unsigned long) ca->disk_buckets, ilog2(bucket_pages(ca)));
-       kfree(ca->prio_buckets);
-       kfree(ca->bio_prio);
-       vfree(ca->buckets);
-       vfree(ca->oldest_gens);
-       free_heap(&ca->heap);
-       free_fifo(&ca->free_inc);
-
-       for (i = 0; i < RESERVE_NR; i++)
-               free_fifo(&ca->free[i]);
+       bch2_dev_buckets_free(ca);
+       free_page((unsigned long) ca->sb_read_scratch);
+
+       bch2_time_stats_exit(&ca->io_latency[WRITE]);
+       bch2_time_stats_exit(&ca->io_latency[READ]);
 
        percpu_ref_exit(&ca->io_ref);
        percpu_ref_exit(&ca->ref);
        kobject_put(&ca->kobj);
 }
 
-static void bch2_dev_io_ref_release(struct percpu_ref *ref)
+static void __bch2_dev_offline(struct bch_fs *c, struct bch_dev *ca)
 {
-       struct bch_dev *ca = container_of(ref, struct bch_dev, io_ref);
-
-       complete(&ca->offline_complete);
-}
-
-static void __bch2_dev_offline(struct bch_dev *ca)
-{
-       struct bch_fs *c = ca->fs;
 
        lockdep_assert_held(&c->state_lock);
 
-       __bch2_dev_read_only(ca->fs, ca);
+       if (percpu_ref_is_zero(&ca->io_ref))
+               return;
 
-       reinit_completion(&ca->offline_complete);
+       __bch2_dev_read_only(c, ca);
+
+       reinit_completion(&ca->io_ref_completion);
        percpu_ref_kill(&ca->io_ref);
-       wait_for_completion(&ca->offline_complete);
+       wait_for_completion(&ca->io_ref_completion);
 
        if (ca->kobj.state_in_sysfs) {
-               struct kobject *block =
-                       &part_to_dev(ca->disk_sb.bdev->bd_part)->kobj;
-
-               sysfs_remove_link(block, "bcachefs");
+               sysfs_remove_link(bdev_kobj(ca->disk_sb.bdev), "bcachefs");
                sysfs_remove_link(&ca->kobj, "block");
        }
 
@@ -1021,51 +1199,41 @@ static void __bch2_dev_offline(struct bch_dev *ca)
        bch2_dev_journal_exit(ca);
 }
 
-static void bch2_dev_ref_release(struct percpu_ref *ref)
+static void bch2_dev_ref_complete(struct percpu_ref *ref)
 {
        struct bch_dev *ca = container_of(ref, struct bch_dev, ref);
 
-       complete(&ca->stop_complete);
+       complete(&ca->ref_completion);
 }
 
-static void bch2_dev_stop(struct bch_dev *ca)
+static void bch2_dev_io_ref_complete(struct percpu_ref *ref)
 {
-       struct bch_fs *c = ca->fs;
-
-       lockdep_assert_held(&c->state_lock);
-
-       BUG_ON(rcu_access_pointer(c->devs[ca->dev_idx]) != ca);
-       rcu_assign_pointer(c->devs[ca->dev_idx], NULL);
-
-       synchronize_rcu();
+       struct bch_dev *ca = container_of(ref, struct bch_dev, io_ref);
 
-       reinit_completion(&ca->stop_complete);
-       percpu_ref_kill(&ca->ref);
-       wait_for_completion(&ca->stop_complete);
+       complete(&ca->io_ref_completion);
 }
 
-static int bch2_dev_sysfs_online(struct bch_dev *ca)
+static int bch2_dev_sysfs_online(struct bch_fs *c, struct bch_dev *ca)
 {
-       struct bch_fs *c = ca->fs;
        int ret;
 
        if (!c->kobj.state_in_sysfs)
                return 0;
 
        if (!ca->kobj.state_in_sysfs) {
-               ret = kobject_add(&ca->kobj, &ca->fs->kobj,
+               ret = kobject_add(&ca->kobj, &c->kobj,
                                  "dev-%u", ca->dev_idx);
                if (ret)
                        return ret;
        }
 
        if (ca->disk_sb.bdev) {
-               struct kobject *block =
-                       &part_to_dev(ca->disk_sb.bdev->bd_part)->kobj;
+               struct kobject *block = bdev_kobj(ca->disk_sb.bdev);
 
                ret = sysfs_create_link(block, &ca->kobj, "bcachefs");
                if (ret)
                        return ret;
+
                ret = sysfs_create_link(&ca->kobj, block, "block");
                if (ret)
                        return ret;
@@ -1074,207 +1242,161 @@ static int bch2_dev_sysfs_online(struct bch_dev *ca)
        return 0;
 }
 
-static int bch2_dev_alloc(struct bch_fs *c, unsigned dev_idx)
+static struct bch_dev *__bch2_dev_alloc(struct bch_fs *c,
+                                       struct bch_member *member)
 {
-       struct bch_member *member;
-       size_t reserve_none, movinggc_reserve, free_inc_reserve, total_reserve;
-       size_t heap_size;
-       unsigned i;
        struct bch_dev *ca;
-
-       if (bch2_fs_init_fault("dev_alloc"))
-               return -ENOMEM;
+       unsigned i;
 
        ca = kzalloc(sizeof(*ca), GFP_KERNEL);
        if (!ca)
-               return -ENOMEM;
+               return NULL;
 
        kobject_init(&ca->kobj, &bch2_dev_ktype);
-       init_completion(&ca->stop_complete);
-       init_completion(&ca->offline_complete);
+       init_completion(&ca->ref_completion);
+       init_completion(&ca->io_ref_completion);
 
-       spin_lock_init(&ca->self.lock);
-       ca->self.nr = 1;
-       rcu_assign_pointer(ca->self.d[0].dev, ca);
-       ca->dev_idx = dev_idx;
+       init_rwsem(&ca->bucket_lock);
 
-       spin_lock_init(&ca->freelist_lock);
-       spin_lock_init(&ca->prio_buckets_lock);
-       mutex_init(&ca->heap_lock);
-       mutex_init(&ca->prio_write_lock);
-       bch2_dev_moving_gc_init(ca);
+       INIT_WORK(&ca->io_error_work, bch2_io_error_work);
 
-       INIT_WORK(&ca->io_error_work, bch2_nonfatal_io_error_work);
+       bch2_time_stats_init(&ca->io_latency[READ]);
+       bch2_time_stats_init(&ca->io_latency[WRITE]);
 
-       if (bch2_fs_init_fault("dev_alloc"))
-               goto err;
+       ca->mi = bch2_mi_to_cpu(member);
 
-       member = bch2_sb_get_members(c->disk_sb)->members + dev_idx;
+       for (i = 0; i < ARRAY_SIZE(member->errors); i++)
+               atomic64_set(&ca->errors[i], le64_to_cpu(member->errors[i]));
 
-       ca->mi = bch2_mi_to_cpu(member);
        ca->uuid = member->uuid;
-       ca->bucket_bits = ilog2(ca->mi.bucket_size);
-       scnprintf(ca->name, sizeof(ca->name), "dev-%u", dev_idx);
 
-       /* XXX: tune these */
-       movinggc_reserve = max_t(size_t, 16, ca->mi.nbuckets >> 7);
-       reserve_none = max_t(size_t, 4, ca->mi.nbuckets >> 9);
-       /*
-        * free_inc must be smaller than the copygc reserve: if it was bigger,
-        * one copygc iteration might not make enough buckets available to fill
-        * up free_inc and allow the allocator to make forward progress
-        */
-       free_inc_reserve = movinggc_reserve / 2;
-       heap_size = movinggc_reserve * 8;
+       ca->nr_btree_reserve = DIV_ROUND_UP(BTREE_NODE_RESERVE,
+                            ca->mi.bucket_size / btree_sectors(c));
 
-       if (percpu_ref_init(&ca->ref, bch2_dev_ref_release,
+       if (percpu_ref_init(&ca->ref, bch2_dev_ref_complete,
                            0, GFP_KERNEL) ||
-           percpu_ref_init(&ca->io_ref, bch2_dev_io_ref_release,
+           percpu_ref_init(&ca->io_ref, bch2_dev_io_ref_complete,
                            PERCPU_REF_INIT_DEAD, GFP_KERNEL) ||
-           !init_fifo(&ca->free[RESERVE_PRIO], prio_buckets(ca), GFP_KERNEL) ||
-           !init_fifo(&ca->free[RESERVE_BTREE], BTREE_NODE_RESERVE, GFP_KERNEL) ||
-           !init_fifo(&ca->free[RESERVE_MOVINGGC],
-                      movinggc_reserve, GFP_KERNEL) ||
-           !init_fifo(&ca->free[RESERVE_NONE], reserve_none, GFP_KERNEL) ||
-           !init_fifo(&ca->free_inc,   free_inc_reserve, GFP_KERNEL) ||
-           !init_heap(&ca->heap,       heap_size, GFP_KERNEL) ||
-           !(ca->oldest_gens   = vzalloc(sizeof(u8) *
-                                         ca->mi.nbuckets)) ||
-           !(ca->buckets       = vzalloc(sizeof(struct bucket) *
-                                         ca->mi.nbuckets)) ||
-           !(ca->prio_buckets  = kzalloc(sizeof(u64) * prio_buckets(ca) *
-                                         2, GFP_KERNEL)) ||
-           !(ca->disk_buckets  = alloc_bucket_pages(GFP_KERNEL, ca)) ||
-           !(ca->usage_percpu = alloc_percpu(struct bch_dev_usage)) ||
-           !(ca->bio_prio = bio_kmalloc(GFP_NOIO, bucket_pages(ca))) ||
+           !(ca->sb_read_scratch = (void *) __get_free_page(GFP_KERNEL)) ||
+           bch2_dev_buckets_alloc(c, ca) ||
            bioset_init(&ca->replica_set, 4,
-                       offsetof(struct bch_write_bio, bio)) ||
-           !(ca->sectors_written = alloc_percpu(*ca->sectors_written)))
+                       offsetof(struct bch_write_bio, bio), 0) ||
+           !(ca->io_done       = alloc_percpu(*ca->io_done)))
                goto err;
 
-       ca->prio_last_buckets = ca->prio_buckets + prio_buckets(ca);
-
-       total_reserve = ca->free_inc.size;
-       for (i = 0; i < RESERVE_NR; i++)
-               total_reserve += ca->free[i].size;
+       return ca;
+err:
+       bch2_dev_free(ca);
+       return NULL;
+}
 
-       ca->copygc_write_point.group = &ca->self;
-       ca->tiering_write_point.group = &ca->self;
+static void bch2_dev_attach(struct bch_fs *c, struct bch_dev *ca,
+                           unsigned dev_idx)
+{
+       ca->dev_idx = dev_idx;
+       __set_bit(ca->dev_idx, ca->self.d);
+       scnprintf(ca->name, sizeof(ca->name), "dev-%u", dev_idx);
 
        ca->fs = c;
        rcu_assign_pointer(c->devs[ca->dev_idx], ca);
 
-       if (bch2_dev_sysfs_online(ca))
+       if (bch2_dev_sysfs_online(c, ca))
                pr_warn("error creating sysfs objects");
-
-       return 0;
-err:
-       bch2_dev_free(ca);
-       return -ENOMEM;
 }
 
-static int __bch2_dev_online(struct bch_fs *c, struct bcache_superblock *sb)
+static int bch2_dev_alloc(struct bch_fs *c, unsigned dev_idx)
 {
-       struct bch_dev *ca;
-       int ret;
+       struct bch_member member = bch2_sb_member_get(c->disk_sb.sb, dev_idx);
+       struct bch_dev *ca = NULL;
+       int ret = 0;
 
-       lockdep_assert_held(&c->sb_lock);
+       if (bch2_fs_init_fault("dev_alloc"))
+               goto err;
 
-       if (le64_to_cpu(sb->sb->seq) >
-           le64_to_cpu(c->disk_sb->seq))
-               bch2_sb_to_fs(c, sb->sb);
+       ca = __bch2_dev_alloc(c, &member);
+       if (!ca)
+               goto err;
 
-       BUG_ON(sb->sb->dev_idx >= c->sb.nr_devices ||
-              !c->devs[sb->sb->dev_idx]);
+       ca->fs = c;
 
-       ca = c->devs[sb->sb->dev_idx];
-       if (ca->disk_sb.bdev) {
-               bch_err(c, "already have device online in slot %u",
+       bch2_dev_attach(c, ca, dev_idx);
+       return ret;
+err:
+       if (ca)
+               bch2_dev_free(ca);
+       return -BCH_ERR_ENOMEM_dev_alloc;
+}
+
+static int __bch2_dev_attach_bdev(struct bch_dev *ca, struct bch_sb_handle *sb)
+{
+       unsigned ret;
+
+       if (bch2_dev_is_online(ca)) {
+               bch_err(ca, "already have device online in slot %u",
                        sb->sb->dev_idx);
-               return -EINVAL;
+               return -BCH_ERR_device_already_online;
        }
 
+       if (get_capacity(sb->bdev->bd_disk) <
+           ca->mi.bucket_size * ca->mi.nbuckets) {
+               bch_err(ca, "cannot online: device too small");
+               return -BCH_ERR_device_size_too_small;
+       }
+
+       BUG_ON(!percpu_ref_is_zero(&ca->io_ref));
+
        ret = bch2_dev_journal_init(ca, sb->sb);
        if (ret)
                return ret;
 
-       /*
-        * Increase journal write timeout if flushes to this device are
-        * expensive:
-        */
-       if (!blk_queue_nonrot(bdev_get_queue(sb->bdev)) &&
-           journal_flushes_device(ca))
-               c->journal.write_delay_ms =
-                       max(c->journal.write_delay_ms, 1000U);
-
        /* Commit: */
        ca->disk_sb = *sb;
-       if (sb->mode & FMODE_EXCL)
-               ca->disk_sb.bdev->bd_holder = ca;
        memset(sb, 0, sizeof(*sb));
 
-       if (c->sb.nr_devices == 1)
-               bdevname(ca->disk_sb.bdev, c->name);
-       bdevname(ca->disk_sb.bdev, ca->name);
-
-       if (bch2_dev_sysfs_online(ca))
-               pr_warn("error creating sysfs objects");
-
-       lg_local_lock(&c->usage_lock);
-       if (!gc_will_visit(c, gc_phase(GC_PHASE_SB_METADATA)))
-               bch2_mark_dev_metadata(ca->fs, ca);
-       lg_local_unlock(&c->usage_lock);
+       ca->dev = ca->disk_sb.bdev->bd_dev;
 
        percpu_ref_reinit(&ca->io_ref);
+
        return 0;
 }
 
-/* Device management: */
-
-bool bch2_fs_may_start(struct bch_fs *c, int flags)
+static int bch2_dev_attach_bdev(struct bch_fs *c, struct bch_sb_handle *sb)
 {
-       struct bch_sb_field_members *mi;
-       unsigned meta_missing = 0;
-       unsigned data_missing = 0;
-       bool degraded = false;
-       unsigned i;
+       struct bch_dev *ca;
+       int ret;
 
-       mutex_lock(&c->sb_lock);
-       mi = bch2_sb_get_members(c->disk_sb);
-
-       for (i = 0; i < c->disk_sb->nr_devices; i++)
-               if (!c->devs[i] &&
-                   !bch2_is_zero(mi->members[i].uuid.b, sizeof(uuid_le))) {
-                       degraded = true;
-                       if (BCH_MEMBER_HAS_METADATA(&mi->members[i]))
-                               meta_missing++;
-                       if (BCH_MEMBER_HAS_DATA(&mi->members[i]))
-                               data_missing++;
-               }
-       mutex_unlock(&c->sb_lock);
+       lockdep_assert_held(&c->state_lock);
 
-       if (degraded &&
-           !(flags & BCH_FORCE_IF_DEGRADED))
-               return false;
+       if (le64_to_cpu(sb->sb->seq) >
+           le64_to_cpu(c->disk_sb.sb->seq))
+               bch2_sb_to_fs(c, sb->sb);
 
-       if (meta_missing &&
-           !(flags & BCH_FORCE_IF_METADATA_DEGRADED))
-               return false;
+       BUG_ON(sb->sb->dev_idx >= c->sb.nr_devices ||
+              !c->devs[sb->sb->dev_idx]);
 
-       if (meta_missing >= BCH_SB_META_REPLICAS_HAVE(c->disk_sb) &&
-           !(flags & BCH_FORCE_IF_METADATA_LOST))
-               return false;
+       ca = bch_dev_locked(c, sb->sb->dev_idx);
 
-       if (data_missing && !(flags & BCH_FORCE_IF_DATA_DEGRADED))
-               return false;
+       ret = __bch2_dev_attach_bdev(ca, sb);
+       if (ret)
+               return ret;
 
-       if (data_missing >= BCH_SB_DATA_REPLICAS_HAVE(c->disk_sb) &&
-           !(flags & BCH_FORCE_IF_DATA_LOST))
-               return false;
+       bch2_dev_sysfs_online(c, ca);
 
-       return true;
+       struct printbuf name = PRINTBUF;
+       prt_bdevname(&name, ca->disk_sb.bdev);
+
+       if (c->sb.nr_devices == 1)
+               strlcpy(c->name, name.buf, sizeof(c->name));
+       strlcpy(ca->name, name.buf, sizeof(ca->name));
+
+       printbuf_exit(&name);
+
+       rebalance_wakeup(c);
+       return 0;
 }
 
+/* Device management: */
+
 /*
  * Note: this function is also used by the error paths - when a particular
  * device sees an error, we call it to determine whether we can just set the
@@ -1287,101 +1409,129 @@ bool bch2_fs_may_start(struct bch_fs *c, int flags)
 bool bch2_dev_state_allowed(struct bch_fs *c, struct bch_dev *ca,
                            enum bch_member_state new_state, int flags)
 {
+       struct bch_devs_mask new_online_devs;
+       int nr_rw = 0, required;
+
        lockdep_assert_held(&c->state_lock);
 
-       if (new_state == BCH_MEMBER_STATE_RW)
+       switch (new_state) {
+       case BCH_MEMBER_STATE_rw:
                return true;
+       case BCH_MEMBER_STATE_ro:
+               if (ca->mi.state != BCH_MEMBER_STATE_rw)
+                       return true;
+
+               /* do we have enough devices to write to?  */
+               for_each_member_device(c, ca2)
+                       if (ca2 != ca)
+                               nr_rw += ca2->mi.state == BCH_MEMBER_STATE_rw;
+
+               required = max(!(flags & BCH_FORCE_IF_METADATA_DEGRADED)
+                              ? c->opts.metadata_replicas
+                              : c->opts.metadata_replicas_required,
+                              !(flags & BCH_FORCE_IF_DATA_DEGRADED)
+                              ? c->opts.data_replicas
+                              : c->opts.data_replicas_required);
+
+               return nr_rw >= required;
+       case BCH_MEMBER_STATE_failed:
+       case BCH_MEMBER_STATE_spare:
+               if (ca->mi.state != BCH_MEMBER_STATE_rw &&
+                   ca->mi.state != BCH_MEMBER_STATE_ro)
+                       return true;
+
+               /* do we have enough devices to read from?  */
+               new_online_devs = bch2_online_devs(c);
+               __clear_bit(ca->dev_idx, new_online_devs.d);
+
+               return bch2_have_enough_devs(c, new_online_devs, flags, false);
+       default:
+               BUG();
+       }
+}
 
-       if (ca->mi.state == BCH_MEMBER_STATE_FAILED)
-               return true;
+static bool bch2_fs_may_start(struct bch_fs *c)
+{
+       struct bch_dev *ca;
+       unsigned i, flags = 0;
 
-       /*
-        * If the device is already offline - whatever is going on with it can't
-        * possible make the FS need to go RO:
-        */
-       if (!bch2_dev_is_online(ca))
-               return true;
+       if (c->opts.very_degraded)
+               flags |= BCH_FORCE_IF_DEGRADED|BCH_FORCE_IF_LOST;
 
-       if (ca->mi.has_data &&
-           !(flags & BCH_FORCE_IF_DATA_DEGRADED))
-               return false;
+       if (c->opts.degraded)
+               flags |= BCH_FORCE_IF_DEGRADED;
 
-       if (ca->mi.has_data &&
-           c->sb.data_replicas_have <= 1 &&
-           !(flags & BCH_FORCE_IF_DATA_LOST))
-               return false;
+       if (!c->opts.degraded &&
+           !c->opts.very_degraded) {
+               mutex_lock(&c->sb_lock);
 
-       if (ca->mi.has_metadata &&
-           !(flags & BCH_FORCE_IF_METADATA_DEGRADED))
-               return false;
+               for (i = 0; i < c->disk_sb.sb->nr_devices; i++) {
+                       if (!bch2_dev_exists(c->disk_sb.sb, i))
+                               continue;
 
-       if (ca->mi.has_metadata &&
-           c->sb.meta_replicas_have <= 1 &&
-           !(flags & BCH_FORCE_IF_METADATA_LOST))
-               return false;
+                       ca = bch_dev_locked(c, i);
 
-       return true;
+                       if (!bch2_dev_is_online(ca) &&
+                           (ca->mi.state == BCH_MEMBER_STATE_rw ||
+                            ca->mi.state == BCH_MEMBER_STATE_ro)) {
+                               mutex_unlock(&c->sb_lock);
+                               return false;
+                       }
+               }
+               mutex_unlock(&c->sb_lock);
+       }
+
+       return bch2_have_enough_devs(c, bch2_online_devs(c), flags, true);
 }
 
 static void __bch2_dev_read_only(struct bch_fs *c, struct bch_dev *ca)
 {
-       bch2_moving_gc_stop(ca);
-
        /*
-        * This stops new data writes (e.g. to existing open data
-        * buckets) and then waits for all existing writes to
-        * complete.
+        * The allocator thread itself allocates btree nodes, so stop it first:
         */
-       bch2_dev_allocator_stop(ca);
-
-       bch2_dev_group_remove(&c->journal.devs, ca);
+       bch2_dev_allocator_remove(c, ca);
+       bch2_dev_journal_stop(&c->journal, ca);
 }
 
-static const char *__bch2_dev_read_write(struct bch_fs *c, struct bch_dev *ca)
+static void __bch2_dev_read_write(struct bch_fs *c, struct bch_dev *ca)
 {
        lockdep_assert_held(&c->state_lock);
 
-       BUG_ON(ca->mi.state != BCH_MEMBER_STATE_RW);
-
-       if (bch2_dev_allocator_start(ca))
-               return "error starting allocator thread";
-
-       if (bch2_moving_gc_start(ca))
-               return "error starting moving GC thread";
+       BUG_ON(ca->mi.state != BCH_MEMBER_STATE_rw);
 
-       if (bch2_tiering_start(c))
-               return "error starting tiering thread";
-
-       return NULL;
+       bch2_dev_allocator_add(c, ca);
+       bch2_recalc_capacity(c);
 }
 
 int __bch2_dev_set_state(struct bch_fs *c, struct bch_dev *ca,
                         enum bch_member_state new_state, int flags)
 {
-       struct bch_sb_field_members *mi;
+       struct bch_member *m;
+       int ret = 0;
 
        if (ca->mi.state == new_state)
                return 0;
 
        if (!bch2_dev_state_allowed(c, ca, new_state, flags))
-               return -EINVAL;
+               return -BCH_ERR_device_state_not_allowed;
 
-       if (new_state == BCH_MEMBER_STATE_RW) {
-               if (__bch2_dev_read_write(c, ca))
-                       return -ENOMEM;
-       } else {
+       if (new_state != BCH_MEMBER_STATE_rw)
                __bch2_dev_read_only(c, ca);
-       }
 
-       bch_notice(ca, "%s", bch2_dev_state[new_state]);
+       bch_notice(ca, "%s", bch2_member_states[new_state]);
 
        mutex_lock(&c->sb_lock);
-       mi = bch2_sb_get_members(c->disk_sb);
-       SET_BCH_MEMBER_STATE(&mi->members[ca->dev_idx], new_state);
+       m = bch2_members_v2_get_mut(c->disk_sb.sb, ca->dev_idx);
+       SET_BCH_MEMBER_STATE(m, new_state);
        bch2_write_super(c);
        mutex_unlock(&c->sb_lock);
 
-       return 0;
+       if (new_state == BCH_MEMBER_STATE_rw)
+               __bch2_dev_read_write(c, ca);
+
+       rebalance_wakeup(c);
+
+       return ret;
 }
 
 int bch2_dev_set_state(struct bch_fs *c, struct bch_dev *ca,
@@ -1389,470 +1539,545 @@ int bch2_dev_set_state(struct bch_fs *c, struct bch_dev *ca,
 {
        int ret;
 
-       mutex_lock(&c->state_lock);
+       down_write(&c->state_lock);
        ret = __bch2_dev_set_state(c, ca, new_state, flags);
-       mutex_unlock(&c->state_lock);
+       up_write(&c->state_lock);
 
        return ret;
 }
 
 /* Device add/removal: */
 
+static int bch2_dev_remove_alloc(struct bch_fs *c, struct bch_dev *ca)
+{
+       struct bpos start       = POS(ca->dev_idx, 0);
+       struct bpos end         = POS(ca->dev_idx, U64_MAX);
+       int ret;
+
+       /*
+        * We clear the LRU and need_discard btrees first so that we don't race
+        * with bch2_do_invalidates() and bch2_do_discards()
+        */
+       ret =   bch2_btree_delete_range(c, BTREE_ID_lru, start, end,
+                                       BTREE_TRIGGER_NORUN, NULL) ?:
+               bch2_btree_delete_range(c, BTREE_ID_need_discard, start, end,
+                                       BTREE_TRIGGER_NORUN, NULL) ?:
+               bch2_btree_delete_range(c, BTREE_ID_freespace, start, end,
+                                       BTREE_TRIGGER_NORUN, NULL) ?:
+               bch2_btree_delete_range(c, BTREE_ID_backpointers, start, end,
+                                       BTREE_TRIGGER_NORUN, NULL) ?:
+               bch2_btree_delete_range(c, BTREE_ID_alloc, start, end,
+                                       BTREE_TRIGGER_NORUN, NULL) ?:
+               bch2_btree_delete_range(c, BTREE_ID_bucket_gens, start, end,
+                                       BTREE_TRIGGER_NORUN, NULL);
+       bch_err_msg(c, ret, "removing dev alloc info");
+       return ret;
+}
+
 int bch2_dev_remove(struct bch_fs *c, struct bch_dev *ca, int flags)
 {
-       struct bch_sb_field_members *mi;
-       unsigned dev_idx = ca->dev_idx;
-       int ret = -EINVAL;
+       struct bch_member *m;
+       unsigned dev_idx = ca->dev_idx, data;
+       int ret;
 
-       mutex_lock(&c->state_lock);
+       down_write(&c->state_lock);
 
-       percpu_ref_put(&ca->ref); /* XXX */
+       /*
+        * We consume a reference to ca->ref, regardless of whether we succeed
+        * or fail:
+        */
+       percpu_ref_put(&ca->ref);
 
-       if (ca->mi.state == BCH_MEMBER_STATE_RW) {
-               bch_err(ca, "Cannot remove RW device");
+       if (!bch2_dev_state_allowed(c, ca, BCH_MEMBER_STATE_failed, flags)) {
+               bch_err(ca, "Cannot remove without losing data");
+               ret = -BCH_ERR_device_state_not_allowed;
                goto err;
        }
 
-       if (!bch2_dev_state_allowed(c, ca, BCH_MEMBER_STATE_FAILED, flags)) {
-               bch_err(ca, "Cannot remove without losing data");
+       __bch2_dev_read_only(c, ca);
+
+       ret = bch2_dev_data_drop(c, ca->dev_idx, flags);
+       bch_err_msg(ca, ret, "dropping data");
+       if (ret)
                goto err;
-       }
 
-       /*
-        * XXX: verify that dev_idx is really not in use anymore, anywhere
-        *
-        * flag_data_bad() does not check btree pointers
-        */
-       ret = bch2_flag_data_bad(ca);
-       if (ret) {
-               bch_err(ca, "Remove failed");
+       ret = bch2_dev_remove_alloc(c, ca);
+       bch_err_msg(ca, ret, "deleting alloc info");
+       if (ret)
                goto err;
-       }
 
-       if (ca->mi.has_data || ca->mi.has_metadata) {
-               bch_err(ca, "Remove failed, still has data");
+       ret = bch2_journal_flush_device_pins(&c->journal, ca->dev_idx);
+       bch_err_msg(ca, ret, "flushing journal");
+       if (ret)
+               goto err;
+
+       ret = bch2_journal_flush(&c->journal);
+       bch_err(ca, "journal error");
+       if (ret)
+               goto err;
+
+       ret = bch2_replicas_gc2(c);
+       bch_err_msg(ca, ret, "in replicas_gc2()");
+       if (ret)
+               goto err;
+
+       data = bch2_dev_has_data(c, ca);
+       if (data) {
+               struct printbuf data_has = PRINTBUF;
+
+               prt_bitflags(&data_has, bch2_data_types, data);
+               bch_err(ca, "Remove failed, still has data (%s)", data_has.buf);
+               printbuf_exit(&data_has);
+               ret = -EBUSY;
                goto err;
        }
 
-       /*
-        * Ok, really doing the remove:
-        * Drop device's prio pointer before removing it from superblock:
-        */
-       spin_lock(&c->journal.lock);
-       c->journal.prio_buckets[dev_idx] = 0;
-       spin_unlock(&c->journal.lock);
+       __bch2_dev_offline(c, ca);
 
-       bch2_journal_meta(&c->journal);
+       mutex_lock(&c->sb_lock);
+       rcu_assign_pointer(c->devs[ca->dev_idx], NULL);
+       mutex_unlock(&c->sb_lock);
+
+       percpu_ref_kill(&ca->ref);
+       wait_for_completion(&ca->ref_completion);
 
-       __bch2_dev_offline(ca);
-       bch2_dev_stop(ca);
        bch2_dev_free(ca);
 
+       /*
+        * At this point the device object has been removed in-core, but the
+        * on-disk journal might still refer to the device index via sb device
+        * usage entries. Recovery fails if it sees usage information for an
+        * invalid device. Flush journal pins to push the back of the journal
+        * past now invalid device index references before we update the
+        * superblock, but after the device object has been removed so any
+        * further journal writes elide usage info for the device.
+        */
+       bch2_journal_flush_all_pins(&c->journal);
+
        /*
         * Free this device's slot in the bch_member array - all pointers to
         * this device must be gone:
         */
        mutex_lock(&c->sb_lock);
-       mi = bch2_sb_get_members(c->disk_sb);
-       memset(&mi->members[dev_idx].uuid, 0, sizeof(mi->members[dev_idx].uuid));
+       m = bch2_members_v2_get_mut(c->disk_sb.sb, dev_idx);
+       memset(&m->uuid, 0, sizeof(m->uuid));
 
        bch2_write_super(c);
 
        mutex_unlock(&c->sb_lock);
-       mutex_unlock(&c->state_lock);
+       up_write(&c->state_lock);
+
+       bch2_dev_usage_journal_reserve(c);
        return 0;
 err:
-       mutex_unlock(&c->state_lock);
+       if (ca->mi.state == BCH_MEMBER_STATE_rw &&
+           !percpu_ref_is_zero(&ca->io_ref))
+               __bch2_dev_read_write(c, ca);
+       up_write(&c->state_lock);
        return ret;
 }
 
+/* Add new device to running filesystem: */
 int bch2_dev_add(struct bch_fs *c, const char *path)
 {
-       struct bcache_superblock sb;
-       const char *err;
+       struct bch_opts opts = bch2_opts_empty();
+       struct bch_sb_handle sb;
        struct bch_dev *ca = NULL;
-       struct bch_sb_field_members *mi, *dev_mi;
-       struct bch_member saved_mi;
+       struct bch_sb_field_members_v2 *mi;
+       struct bch_member dev_mi;
        unsigned dev_idx, nr_devices, u64s;
-       int ret = -EINVAL;
+       struct printbuf errbuf = PRINTBUF;
+       struct printbuf label = PRINTBUF;
+       int ret;
 
-       err = bch2_read_super(&sb, bch2_opts_empty(), path);
-       if (err)
-               return -EINVAL;
+       ret = bch2_read_super(path, &opts, &sb);
+       bch_err_msg(c, ret, "reading super");
+       if (ret)
+               goto err;
 
-       err = bch2_validate_cache_super(&sb);
-       if (err)
-               return -EINVAL;
+       dev_mi = bch2_sb_member_get(sb.sb, sb.sb->dev_idx);
 
-       err = bch2_dev_may_add(sb.sb, c);
-       if (err)
-               return -EINVAL;
+       if (BCH_MEMBER_GROUP(&dev_mi)) {
+               bch2_disk_path_to_text_sb(&label, sb.sb, BCH_MEMBER_GROUP(&dev_mi) - 1);
+               if (label.allocation_failure) {
+                       ret = -ENOMEM;
+                       goto err;
+               }
+       }
+
+       ret = bch2_dev_may_add(sb.sb, c);
+       if (ret)
+               goto err;
 
-       mutex_lock(&c->state_lock);
+       ca = __bch2_dev_alloc(c, &dev_mi);
+       if (!ca) {
+               ret = -ENOMEM;
+               goto err;
+       }
+
+       bch2_dev_usage_init(ca);
+
+       ret = __bch2_dev_attach_bdev(ca, &sb);
+       if (ret)
+               goto err;
+
+       ret = bch2_dev_journal_alloc(ca);
+       bch_err_msg(c, ret, "allocating journal");
+       if (ret)
+               goto err;
+
+       down_write(&c->state_lock);
        mutex_lock(&c->sb_lock);
 
-       /*
-        * Preserve the old cache member information (esp. tier)
-        * before we start bashing the disk stuff.
-        */
-       dev_mi = bch2_sb_get_members(sb.sb);
-       saved_mi = dev_mi->members[sb.sb->dev_idx];
-       saved_mi.last_mount = cpu_to_le64(ktime_get_seconds());
+       ret = bch2_sb_from_fs(c, ca);
+       bch_err_msg(c, ret, "setting up new superblock");
+       if (ret)
+               goto err_unlock;
 
        if (dynamic_fault("bcachefs:add:no_slot"))
                goto no_slot;
 
-       mi = bch2_sb_get_members(c->disk_sb);
        for (dev_idx = 0; dev_idx < BCH_SB_MEMBERS_MAX; dev_idx++)
-               if (dev_idx >= c->sb.nr_devices ||
-                   bch2_is_zero(mi->members[dev_idx].uuid.b,
-                                sizeof(uuid_le)))
+               if (!bch2_dev_exists(c->disk_sb.sb, dev_idx))
                        goto have_slot;
 no_slot:
-       err = "no slots available in superblock";
-       ret = -ENOSPC;
+       ret = -BCH_ERR_ENOSPC_sb_members;
+       bch_err_msg(c, ret, "setting up new superblock");
        goto err_unlock;
 
 have_slot:
        nr_devices = max_t(unsigned, dev_idx + 1, c->sb.nr_devices);
-       u64s = (sizeof(struct bch_sb_field_members) +
-               sizeof(struct bch_member) * nr_devices) / sizeof(u64);
-       err = "no space in superblock for member info";
 
-       mi = bch2_fs_sb_resize_members(c, u64s);
-       if (!mi)
-               goto err_unlock;
+       mi = bch2_sb_field_get(c->disk_sb.sb, members_v2);
+       u64s = DIV_ROUND_UP(sizeof(struct bch_sb_field_members_v2) +
+                           le16_to_cpu(mi->member_bytes) * nr_devices, sizeof(u64));
 
-       dev_mi = bch2_sb_resize_members(&sb, u64s);
-       if (!dev_mi)
+       mi = bch2_sb_field_resize(&c->disk_sb, members_v2, u64s);
+       if (!mi) {
+               ret = -BCH_ERR_ENOSPC_sb_members;
+               bch_err_msg(c, ret, "setting up new superblock");
                goto err_unlock;
+       }
+       struct bch_member *m = bch2_members_v2_get_mut(c->disk_sb.sb, dev_idx);
 
-       memcpy(dev_mi, mi, u64s * sizeof(u64));
-       dev_mi->members[dev_idx] = saved_mi;
-
-       sb.sb->uuid             = c->disk_sb->uuid;
-       sb.sb->dev_idx          = dev_idx;
-       sb.sb->nr_devices       = nr_devices;
+       /* success: */
 
-       /* commit new member info */
-       memcpy(mi, dev_mi, u64s * sizeof(u64));
-       c->disk_sb->nr_devices  = nr_devices;
-       c->sb.nr_devices        = nr_devices;
+       *m = dev_mi;
+       m->last_mount = cpu_to_le64(ktime_get_real_seconds());
+       c->disk_sb.sb->nr_devices       = nr_devices;
 
-       if (bch2_dev_alloc(c, dev_idx)) {
-               err = "cannot allocate memory";
-               ret = -ENOMEM;
-               goto err_unlock;
-       }
+       ca->disk_sb.sb->dev_idx = dev_idx;
+       bch2_dev_attach(c, ca, dev_idx);
 
-       if (__bch2_dev_online(c, &sb)) {
-               err = "bch2_dev_online() error";
-               ret = -ENOMEM;
-               goto err_unlock;
+       if (BCH_MEMBER_GROUP(&dev_mi)) {
+               ret = __bch2_dev_group_set(c, ca, label.buf);
+               bch_err_msg(c, ret, "creating new label");
+               if (ret)
+                       goto err_unlock;
        }
 
        bch2_write_super(c);
        mutex_unlock(&c->sb_lock);
 
-       ca = c->devs[dev_idx];
-       if (ca->mi.state == BCH_MEMBER_STATE_RW) {
-               err = "journal alloc failed";
-               if (bch2_dev_journal_alloc(ca))
-                       goto err;
+       bch2_dev_usage_journal_reserve(c);
 
-               err = __bch2_dev_read_write(c, ca);
-               if (err)
-                       goto err;
-       }
+       ret = bch2_trans_mark_dev_sb(c, ca);
+       bch_err_msg(ca, ret, "marking new superblock");
+       if (ret)
+               goto err_late;
+
+       ret = bch2_fs_freespace_init(c);
+       bch_err_msg(ca, ret, "initializing free space");
+       if (ret)
+               goto err_late;
 
-       mutex_unlock(&c->state_lock);
+       ca->new_fs_bucket_idx = 0;
+
+       if (ca->mi.state == BCH_MEMBER_STATE_rw)
+               __bch2_dev_read_write(c, ca);
+
+       up_write(&c->state_lock);
        return 0;
+
 err_unlock:
        mutex_unlock(&c->sb_lock);
+       up_write(&c->state_lock);
 err:
-       mutex_unlock(&c->state_lock);
+       if (ca)
+               bch2_dev_free(ca);
        bch2_free_super(&sb);
-
-       bch_err(c, "Unable to add device: %s", err);
-       return ret ?: -EINVAL;
+       printbuf_exit(&label);
+       printbuf_exit(&errbuf);
+       bch_err_fn(c, ret);
+       return ret;
+err_late:
+       up_write(&c->state_lock);
+       ca = NULL;
+       goto err;
 }
 
+/* Hot add existing device to running filesystem: */
 int bch2_dev_online(struct bch_fs *c, const char *path)
 {
-       struct bcache_superblock sb = { 0 };
+       struct bch_opts opts = bch2_opts_empty();
+       struct bch_sb_handle sb = { NULL };
        struct bch_dev *ca;
        unsigned dev_idx;
-       const char *err;
        int ret;
 
-       mutex_lock(&c->state_lock);
+       down_write(&c->state_lock);
 
-       err = bch2_read_super(&sb, bch2_opts_empty(), path);
-       if (err)
-               goto err;
+       ret = bch2_read_super(path, &opts, &sb);
+       if (ret) {
+               up_write(&c->state_lock);
+               return ret;
+       }
 
        dev_idx = sb.sb->dev_idx;
 
-       err = bch2_dev_in_fs(c->disk_sb, sb.sb);
-       if (err)
+       ret = bch2_dev_in_fs(&c->disk_sb, &sb);
+       bch_err_msg(c, ret, "bringing %s online", path);
+       if (ret)
                goto err;
 
-       mutex_lock(&c->sb_lock);
-       if (__bch2_dev_online(c, &sb)) {
-               err = "__bch2_dev_online() error";
-               mutex_unlock(&c->sb_lock);
+       ret = bch2_dev_attach_bdev(c, &sb);
+       if (ret)
                goto err;
-       }
-       mutex_unlock(&c->sb_lock);
 
-       ca = c->devs[dev_idx];
-       ret = bch2_prio_read(ca);
-       if (ret) {
-               err = "error reading priorities";
+       ca = bch_dev_locked(c, dev_idx);
+
+       ret = bch2_trans_mark_dev_sb(c, ca);
+       bch_err_msg(c, ret, "bringing %s online: error from bch2_trans_mark_dev_sb", path);
+       if (ret)
                goto err;
+
+       if (ca->mi.state == BCH_MEMBER_STATE_rw)
+               __bch2_dev_read_write(c, ca);
+
+       if (!ca->mi.freespace_initialized) {
+               ret = bch2_dev_freespace_init(c, ca, 0, ca->mi.nbuckets);
+               bch_err_msg(ca, ret, "initializing free space");
+               if (ret)
+                       goto err;
        }
 
-       if (ca->mi.state == BCH_MEMBER_STATE_RW) {
-               err = __bch2_dev_read_write(c, ca);
-               if (err)
+       if (!ca->journal.nr) {
+               ret = bch2_dev_journal_alloc(ca);
+               bch_err_msg(ca, ret, "allocating journal");
+               if (ret)
                        goto err;
        }
 
-       mutex_unlock(&c->state_lock);
+       mutex_lock(&c->sb_lock);
+       bch2_members_v2_get_mut(c->disk_sb.sb, ca->dev_idx)->last_mount =
+               cpu_to_le64(ktime_get_real_seconds());
+       bch2_write_super(c);
+       mutex_unlock(&c->sb_lock);
+
+       up_write(&c->state_lock);
        return 0;
 err:
-       mutex_unlock(&c->state_lock);
+       up_write(&c->state_lock);
        bch2_free_super(&sb);
-       bch_err(c, "error bringing %s online: %s", path, err);
-       return -EINVAL;
+       return ret;
 }
 
 int bch2_dev_offline(struct bch_fs *c, struct bch_dev *ca, int flags)
 {
-       mutex_lock(&c->state_lock);
+       down_write(&c->state_lock);
 
-       if (!bch2_dev_state_allowed(c, ca, BCH_MEMBER_STATE_FAILED, flags)) {
+       if (!bch2_dev_is_online(ca)) {
+               bch_err(ca, "Already offline");
+               up_write(&c->state_lock);
+               return 0;
+       }
+
+       if (!bch2_dev_state_allowed(c, ca, BCH_MEMBER_STATE_failed, flags)) {
                bch_err(ca, "Cannot offline required disk");
-               mutex_unlock(&c->state_lock);
-               return -EINVAL;
+               up_write(&c->state_lock);
+               return -BCH_ERR_device_state_not_allowed;
        }
 
-       __bch2_dev_read_only(c, ca);
-       __bch2_dev_offline(ca);
+       __bch2_dev_offline(c, ca);
 
-       mutex_unlock(&c->state_lock);
+       up_write(&c->state_lock);
        return 0;
 }
 
-int bch2_dev_evacuate(struct bch_fs *c, struct bch_dev *ca)
+int bch2_dev_resize(struct bch_fs *c, struct bch_dev *ca, u64 nbuckets)
 {
-       int ret;
+       struct bch_member *m;
+       u64 old_nbuckets;
+       int ret = 0;
 
-       mutex_lock(&c->state_lock);
+       down_write(&c->state_lock);
+       old_nbuckets = ca->mi.nbuckets;
 
-       if (ca->mi.state == BCH_MEMBER_STATE_RW) {
-               bch_err(ca, "Cannot migrate data off RW device");
-               mutex_unlock(&c->state_lock);
-               return -EINVAL;
+       if (nbuckets < ca->mi.nbuckets) {
+               bch_err(ca, "Cannot shrink yet");
+               ret = -EINVAL;
+               goto err;
        }
 
-       mutex_unlock(&c->state_lock);
-
-       ret = bch2_move_data_off_device(ca);
-       if (ret) {
-               bch_err(ca, "Error migrating data: %i", ret);
-               return ret;
+       if (bch2_dev_is_online(ca) &&
+           get_capacity(ca->disk_sb.bdev->bd_disk) <
+           ca->mi.bucket_size * nbuckets) {
+               bch_err(ca, "New size larger than device");
+               ret = -BCH_ERR_device_size_too_small;
+               goto err;
        }
 
-       ret = bch2_move_metadata_off_device(ca);
-       if (ret) {
-               bch_err(ca, "Error migrating metadata: %i", ret);
-               return ret;
-       }
+       ret = bch2_dev_buckets_resize(c, ca, nbuckets);
+       bch_err_msg(ca, ret, "resizing buckets");
+       if (ret)
+               goto err;
 
-       if (ca->mi.has_data || ca->mi.has_metadata) {
-               bch_err(ca, "Migrate error: data still present");
-               return -EINVAL;
+       ret = bch2_trans_mark_dev_sb(c, ca);
+       if (ret)
+               goto err;
+
+       mutex_lock(&c->sb_lock);
+       m = bch2_members_v2_get_mut(c->disk_sb.sb, ca->dev_idx);
+       m->nbuckets = cpu_to_le64(nbuckets);
+
+       bch2_write_super(c);
+       mutex_unlock(&c->sb_lock);
+
+       if (ca->mi.freespace_initialized) {
+               ret = bch2_dev_freespace_init(c, ca, old_nbuckets, nbuckets);
+               if (ret)
+                       goto err;
+
+               /*
+                * XXX: this is all wrong transactionally - we'll be able to do
+                * this correctly after the disk space accounting rewrite
+                */
+               ca->usage_base->d[BCH_DATA_free].buckets += nbuckets - old_nbuckets;
        }
 
-       return 0;
+       bch2_recalc_capacity(c);
+err:
+       up_write(&c->state_lock);
+       return ret;
+}
+
+/* return with ref on ca->ref: */
+struct bch_dev *bch2_dev_lookup(struct bch_fs *c, const char *name)
+{
+       rcu_read_lock();
+       for_each_member_device_rcu(c, ca, NULL)
+               if (!strcmp(name, ca->name)) {
+                       rcu_read_unlock();
+                       return ca;
+               }
+       rcu_read_unlock();
+       return ERR_PTR(-BCH_ERR_ENOENT_dev_not_found);
 }
 
 /* Filesystem open: */
 
-const char *bch2_fs_open(char * const *devices, unsigned nr_devices,
-                        struct bch_opts opts, struct bch_fs **ret)
+static inline int sb_cmp(struct bch_sb *l, struct bch_sb *r)
 {
-       const char *err;
-       struct bch_fs *c = NULL;
-       struct bcache_superblock *sb;
-       unsigned i, best_sb = 0;
+       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));
+}
 
-       if (!nr_devices)
-               return "need at least one device";
+struct bch_fs *bch2_fs_open(char * const *devices, unsigned nr_devices,
+                           struct bch_opts opts)
+{
+       DARRAY(struct bch_sb_handle) sbs = { 0 };
+       struct bch_fs *c = NULL;
+       struct bch_sb_handle *best = NULL;
+       struct printbuf errbuf = PRINTBUF;
+       int ret = 0;
 
        if (!try_module_get(THIS_MODULE))
-               return "module unloading";
+               return ERR_PTR(-ENODEV);
 
-       err = "cannot allocate memory";
-       sb = kcalloc(nr_devices, sizeof(*sb), GFP_KERNEL);
-       if (!sb)
+       if (!nr_devices) {
+               ret = -EINVAL;
                goto err;
+       }
 
-       for (i = 0; i < nr_devices; i++) {
-               err = bch2_read_super(&sb[i], opts, devices[i]);
-               if (err)
-                       goto err;
+       ret = darray_make_room(&sbs, nr_devices);
+       if (ret)
+               goto err;
 
-               err = "attempting to register backing device";
-               if (__SB_IS_BDEV(le64_to_cpu(sb[i].sb->version)))
-                       goto err;
+       for (unsigned i = 0; i < nr_devices; i++) {
+               struct bch_sb_handle sb = { NULL };
 
-               err = bch2_validate_cache_super(&sb[i]);
-               if (err)
+               ret = bch2_read_super(devices[i], &opts, &sb);
+               if (ret)
                        goto err;
-       }
 
-       for (i = 1; i < nr_devices; i++)
-               if (le64_to_cpu(sb[i].sb->seq) >
-                   le64_to_cpu(sb[best_sb].sb->seq))
-                       best_sb = i;
+               BUG_ON(darray_push(&sbs, sb));
+       }
 
-       for (i = 0; i < nr_devices; i++) {
-               err = bch2_dev_in_fs(sb[best_sb].sb, sb[i].sb);
-               if (err)
-                       goto err;
+       if (opts.nochanges && !opts.read_only) {
+               ret = -BCH_ERR_erofs_nochanges;
+               goto err_print;
        }
 
-       err = "cannot allocate memory";
-       c = bch2_fs_alloc(sb[best_sb].sb, opts);
-       if (!c)
-               goto err;
+       darray_for_each(sbs, sb)
+               if (!best || sb_cmp(sb->sb, best->sb) > 0)
+                       best = sb;
 
-       err = "bch2_dev_online() error";
-       mutex_lock(&c->sb_lock);
-       for (i = 0; i < nr_devices; i++)
-               if (__bch2_dev_online(c, &sb[i])) {
-                       mutex_unlock(&c->sb_lock);
-                       goto err;
-               }
-       mutex_unlock(&c->sb_lock);
+       darray_for_each_reverse(sbs, sb) {
+               ret = bch2_dev_in_fs(best, sb);
 
-       err = "insufficient devices";
-       if (!bch2_fs_may_start(c, 0))
-               goto err;
+               if (ret == -BCH_ERR_device_has_been_removed ||
+                   ret == -BCH_ERR_device_splitbrain) {
+                       bch2_free_super(sb);
+                       darray_remove_item(&sbs, sb);
+                       best -= best > sb;
+                       ret = 0;
+                       continue;
+               }
 
-       if (!c->opts.nostart) {
-               err = __bch2_fs_start(c);
-               if (err)
-                       goto err;
+               if (ret)
+                       goto err_print;
        }
 
-       err = bch2_fs_online(c);
-       if (err)
-               goto err;
-
+       c = bch2_fs_alloc(best->sb, opts);
+       ret = PTR_ERR_OR_ZERO(c);
        if (ret)
-               *ret = c;
-       else
-               closure_put(&c->cl);
-
-       err = NULL;
-out:
-       kfree(sb);
-       module_put(THIS_MODULE);
-       if (err)
-               c = NULL;
-       return err;
-err:
-       if (c)
-               bch2_fs_stop(c);
-
-       for (i = 0; i < nr_devices; i++)
-               bch2_free_super(&sb[i]);
-       goto out;
-}
-
-static const char *__bch2_fs_open_incremental(struct bcache_superblock *sb,
-                                             struct bch_opts opts)
-{
-       const char *err;
-       struct bch_fs *c;
-       bool allocated_fs = false;
-
-       err = bch2_validate_cache_super(sb);
-       if (err)
-               return err;
-
-       mutex_lock(&bch_fs_list_lock);
-       c = __bch2_uuid_to_fs(sb->sb->uuid);
-       if (c) {
-               closure_get(&c->cl);
+               goto err;
 
-               err = bch2_dev_in_fs(c->disk_sb, sb->sb);
-               if (err)
-                       goto err;
-       } else {
-               c = bch2_fs_alloc(sb->sb, opts);
-               err = "cannot allocate memory";
-               if (!c)
+       down_write(&c->state_lock);
+       darray_for_each(sbs, sb) {
+               ret = bch2_dev_attach_bdev(c, sb);
+               if (ret) {
+                       up_write(&c->state_lock);
                        goto err;
-
-               allocated_fs = true;
+               }
        }
+       up_write(&c->state_lock);
 
-       err = "bch2_dev_online() error";
-
-       mutex_lock(&c->sb_lock);
-       if (__bch2_dev_online(c, sb)) {
-               mutex_unlock(&c->sb_lock);
-               goto err;
+       if (!bch2_fs_may_start(c)) {
+               ret = -BCH_ERR_insufficient_devices_to_start;
+               goto err_print;
        }
-       mutex_unlock(&c->sb_lock);
 
-       if (!c->opts.nostart && bch2_fs_may_start(c, 0)) {
-               err = __bch2_fs_start(c);
-               if (err)
+       if (!c->opts.nostart) {
+               ret = bch2_fs_start(c);
+               if (ret)
                        goto err;
        }
-
-       err = __bch2_fs_online(c);
-       if (err)
-               goto err;
-
-       closure_put(&c->cl);
-       mutex_unlock(&bch_fs_list_lock);
-
-       return NULL;
+out:
+       darray_for_each(sbs, sb)
+               bch2_free_super(sb);
+       darray_exit(&sbs);
+       printbuf_exit(&errbuf);
+       module_put(THIS_MODULE);
+       return c;
+err_print:
+       pr_err("bch_fs_open err opening %s: %s",
+              devices[0], bch2_err_str(ret));
 err:
-       mutex_unlock(&bch_fs_list_lock);
-
-       if (allocated_fs)
+       if (!IS_ERR_OR_NULL(c))
                bch2_fs_stop(c);
-       else if (c)
-               closure_put(&c->cl);
-
-       return err;
-}
-
-const char *bch2_fs_open_incremental(const char *path)
-{
-       struct bcache_superblock sb;
-       struct bch_opts opts = bch2_opts_empty();
-       const char *err;
-
-       err = bch2_read_super(&sb, opts, path);
-       if (err)
-               return err;
-
-       if (!__SB_IS_BDEV(le64_to_cpu(sb.sb->version)))
-               err = __bch2_fs_open_incremental(&sb, opts);
-       else
-               err = "not a bcachefs superblock";
-
-       bch2_free_super(&sb);
-
-       return err;
+       c = ERR_PTR(ret);
+       goto out;
 }
 
 /* Global interfaces/init */
@@ -1862,6 +2087,7 @@ static void bcachefs_exit(void)
        bch2_debug_exit();
        bch2_vfs_exit();
        bch2_chardev_exit();
+       bch2_btree_key_cache_exit();
        if (bcachefs_kset)
                kset_unregister(bcachefs_kset);
 }
@@ -1871,6 +2097,7 @@ static int __init bcachefs_init(void)
        bch2_bkey_pack_test();
 
        if (!(bcachefs_kset = kset_create_and_add("bcachefs", NULL, fs_kobj)) ||
+           bch2_btree_key_cache_init() ||
            bch2_chardev_init() ||
            bch2_vfs_init() ||
            bch2_debug_init())
@@ -1889,5 +2116,9 @@ err:
 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, 0400);
+
 module_exit(bcachefs_exit);
 module_init(bcachefs_init);