]> git.sesse.net Git - bcachefs-tools-debian/blobdiff - libbcachefs/alloc_background.c
Update bcachefs sources to d82da7126f fixup! bcachefs: for_each_btree_key2()
[bcachefs-tools-debian] / libbcachefs / alloc_background.c
index 899291633f98f87fadaf2832cade166d91131458..ca1f45cc80b7f24de2be1cf86886e7cb796ecbfb 100644 (file)
@@ -1,17 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0
 #include "bcachefs.h"
 #include "alloc_background.h"
 #include "alloc_foreground.h"
+#include "backpointers.h"
 #include "btree_cache.h"
 #include "btree_io.h"
+#include "btree_key_cache.h"
 #include "btree_update.h"
 #include "btree_update_interior.h"
 #include "btree_gc.h"
 #include "buckets.h"
+#include "buckets_waiting_for_journal.h"
 #include "clock.h"
 #include "debug.h"
 #include "ec.h"
 #include "error.h"
-#include "journal_io.h"
+#include "lru.h"
+#include "recovery.h"
+#include "varint.h"
 
 #include <linux/kthread.h>
 #include <linux/math64.h>
 #include <linux/sort.h>
 #include <trace/events/bcachefs.h>
 
-static void bch2_recalc_oldest_io(struct bch_fs *, struct bch_dev *, int);
-
-/* Ratelimiting/PD controllers */
-
-static void pd_controllers_update(struct work_struct *work)
-{
-       struct bch_fs *c = container_of(to_delayed_work(work),
-                                          struct bch_fs,
-                                          pd_controllers_update);
-       struct bch_dev *ca;
-       unsigned i;
-
-       for_each_member_device(ca, c, i) {
-               struct bch_dev_usage stats = bch2_dev_usage_read(c, ca);
-
-               u64 free = bucket_to_sector(ca,
-                               __dev_buckets_free(ca, stats)) << 9;
-               /*
-                * Bytes of internal fragmentation, which can be
-                * reclaimed by copy GC
-                */
-               s64 fragmented = (bucket_to_sector(ca,
-                                       stats.buckets[BCH_DATA_USER] +
-                                       stats.buckets[BCH_DATA_CACHED]) -
-                                 (stats.sectors[BCH_DATA_USER] +
-                                  stats.sectors[BCH_DATA_CACHED])) << 9;
-
-               fragmented = max(0LL, fragmented);
-
-               bch2_pd_controller_update(&ca->copygc_pd,
-                                        free, fragmented, -1);
-       }
-
-       schedule_delayed_work(&c->pd_controllers_update,
-                             c->pd_controllers_update_seconds * HZ);
-}
-
 /* Persistent alloc info: */
 
-static unsigned bch_alloc_val_u64s(const struct bch_alloc *a)
-{
-       unsigned bytes = offsetof(struct bch_alloc, data);
-
-       if (a->fields & (1 << BCH_ALLOC_FIELD_READ_TIME))
-               bytes += 2;
-       if (a->fields & (1 << BCH_ALLOC_FIELD_WRITE_TIME))
-               bytes += 2;
-
-       return DIV_ROUND_UP(bytes, sizeof(u64));
-}
-
-const char *bch2_alloc_invalid(const struct bch_fs *c, struct bkey_s_c k)
-{
-       if (k.k->p.inode >= c->sb.nr_devices ||
-           !c->devs[k.k->p.inode])
-               return "invalid device";
-
-       switch (k.k->type) {
-       case BCH_ALLOC: {
-               struct bkey_s_c_alloc a = bkey_s_c_to_alloc(k);
-
-               /* allow for unknown fields */
-               if (bkey_val_u64s(a.k) < bch_alloc_val_u64s(a.v))
-                       return "incorrect value size";
-               break;
-       }
-       default:
-               return "invalid type";
-       }
-
-       return NULL;
-}
-
-void bch2_alloc_to_text(struct printbuf *out, struct bch_fs *c,
-                       struct bkey_s_c k)
+static const unsigned BCH_ALLOC_V1_FIELD_BYTES[] = {
+#define x(name, bits) [BCH_ALLOC_FIELD_V1_##name] = bits / 8,
+       BCH_ALLOC_FIELDS_V1()
+#undef x
+};
+
+struct bkey_alloc_unpacked {
+       u64             journal_seq;
+       u8              gen;
+       u8              oldest_gen;
+       u8              data_type;
+       bool            need_discard:1;
+       bool            need_inc_gen:1;
+#define x(_name, _bits)        u##_bits _name;
+       BCH_ALLOC_FIELDS_V2()
+#undef  x
+};
+
+static inline u64 alloc_field_v1_get(const struct bch_alloc *a,
+                                    const void **p, unsigned field)
 {
-       switch (k.k->type) {
-       case BCH_ALLOC: {
-               struct bkey_s_c_alloc a = bkey_s_c_to_alloc(k);
-
-               pr_buf(out, "gen %u", a.v->gen);
-               break;
-       }
-       }
-}
+       unsigned bytes = BCH_ALLOC_V1_FIELD_BYTES[field];
+       u64 v;
 
-static inline unsigned get_alloc_field(const u8 **p, unsigned bytes)
-{
-       unsigned v;
+       if (!(a->fields & (1 << field)))
+               return 0;
 
        switch (bytes) {
        case 1:
-               v = **p;
+               v = *((const u8 *) *p);
                break;
        case 2:
-               v = le16_to_cpup((void *) *p);
+               v = le16_to_cpup(*p);
                break;
        case 4:
-               v = le32_to_cpup((void *) *p);
+               v = le32_to_cpup(*p);
+               break;
+       case 8:
+               v = le64_to_cpup(*p);
                break;
        default:
                BUG();
@@ -130,11 +78,19 @@ static inline unsigned get_alloc_field(const u8 **p, unsigned bytes)
        return v;
 }
 
-static inline void put_alloc_field(u8 **p, unsigned bytes, unsigned v)
+static inline void alloc_field_v1_put(struct bkey_i_alloc *a, void **p,
+                                     unsigned field, u64 v)
 {
+       unsigned bytes = BCH_ALLOC_V1_FIELD_BYTES[field];
+
+       if (!v)
+               return;
+
+       a->v.fields |= 1 << field;
+
        switch (bytes) {
        case 1:
-               **p = v;
+               *((u8 *) *p) = v;
                break;
        case 2:
                *((__le16 *) *p) = cpu_to_le16(v);
@@ -142,6 +98,9 @@ static inline void put_alloc_field(u8 **p, unsigned bytes, unsigned v)
        case 4:
                *((__le32 *) *p) = cpu_to_le32(v);
                break;
+       case 8:
+               *((__le64 *) *p) = cpu_to_le64(v);
+               break;
        default:
                BUG();
        }
@@ -149,843 +108,1314 @@ static inline void put_alloc_field(u8 **p, unsigned bytes, unsigned v)
        *p += bytes;
 }
 
-static void bch2_alloc_read_key(struct bch_fs *c, struct bkey_s_c k)
+static void bch2_alloc_unpack_v1(struct bkey_alloc_unpacked *out,
+                                struct bkey_s_c k)
 {
-       struct bch_dev *ca;
-       struct bkey_s_c_alloc a;
-       struct bucket_mark new;
-       struct bucket *g;
-       const u8 *d;
+       const struct bch_alloc *in = bkey_s_c_to_alloc(k).v;
+       const void *d = in->data;
+       unsigned idx = 0;
 
-       if (k.k->type != BCH_ALLOC)
-               return;
+       out->gen = in->gen;
 
-       a = bkey_s_c_to_alloc(k);
-       ca = bch_dev_bkey_exists(c, a.k->p.inode);
+#define x(_name, _bits) out->_name = alloc_field_v1_get(in, &d, idx++);
+       BCH_ALLOC_FIELDS_V1()
+#undef  x
+}
 
-       if (a.k->p.offset >= ca->mi.nbuckets)
-               return;
+static int bch2_alloc_unpack_v2(struct bkey_alloc_unpacked *out,
+                               struct bkey_s_c k)
+{
+       struct bkey_s_c_alloc_v2 a = bkey_s_c_to_alloc_v2(k);
+       const u8 *in = a.v->data;
+       const u8 *end = bkey_val_end(a);
+       unsigned fieldnr = 0;
+       int ret;
+       u64 v;
+
+       out->gen        = a.v->gen;
+       out->oldest_gen = a.v->oldest_gen;
+       out->data_type  = a.v->data_type;
+
+#define x(_name, _bits)                                                        \
+       if (fieldnr < a.v->nr_fields) {                                 \
+               ret = bch2_varint_decode_fast(in, end, &v);             \
+               if (ret < 0)                                            \
+                       return ret;                                     \
+               in += ret;                                              \
+       } else {                                                        \
+               v = 0;                                                  \
+       }                                                               \
+       out->_name = v;                                                 \
+       if (v != out->_name)                                            \
+               return -1;                                              \
+       fieldnr++;
+
+       BCH_ALLOC_FIELDS_V2()
+#undef  x
+       return 0;
+}
 
-       percpu_down_read_preempt_disable(&c->usage_lock);
+static int bch2_alloc_unpack_v3(struct bkey_alloc_unpacked *out,
+                               struct bkey_s_c k)
+{
+       struct bkey_s_c_alloc_v3 a = bkey_s_c_to_alloc_v3(k);
+       const u8 *in = a.v->data;
+       const u8 *end = bkey_val_end(a);
+       unsigned fieldnr = 0;
+       int ret;
+       u64 v;
+
+       out->gen        = a.v->gen;
+       out->oldest_gen = a.v->oldest_gen;
+       out->data_type  = a.v->data_type;
+       out->need_discard = BCH_ALLOC_V3_NEED_DISCARD(a.v);
+       out->need_inc_gen = BCH_ALLOC_V3_NEED_INC_GEN(a.v);
+       out->journal_seq = le64_to_cpu(a.v->journal_seq);
+
+#define x(_name, _bits)                                                        \
+       if (fieldnr < a.v->nr_fields) {                                 \
+               ret = bch2_varint_decode_fast(in, end, &v);             \
+               if (ret < 0)                                            \
+                       return ret;                                     \
+               in += ret;                                              \
+       } else {                                                        \
+               v = 0;                                                  \
+       }                                                               \
+       out->_name = v;                                                 \
+       if (v != out->_name)                                            \
+               return -1;                                              \
+       fieldnr++;
+
+       BCH_ALLOC_FIELDS_V2()
+#undef  x
+       return 0;
+}
 
-       g = bucket(ca, a.k->p.offset);
-       bucket_cmpxchg(g, new, ({
-               new.gen = a.v->gen;
-               new.gen_valid = 1;
-       }));
+static struct bkey_alloc_unpacked bch2_alloc_unpack(struct bkey_s_c k)
+{
+       struct bkey_alloc_unpacked ret = { .gen = 0 };
 
-       d = a.v->data;
-       if (a.v->fields & (1 << BCH_ALLOC_FIELD_READ_TIME))
-               g->io_time[READ] = get_alloc_field(&d, 2);
-       if (a.v->fields & (1 << BCH_ALLOC_FIELD_WRITE_TIME))
-               g->io_time[WRITE] = get_alloc_field(&d, 2);
+       switch (k.k->type) {
+       case KEY_TYPE_alloc:
+               bch2_alloc_unpack_v1(&ret, k);
+               break;
+       case KEY_TYPE_alloc_v2:
+               bch2_alloc_unpack_v2(&ret, k);
+               break;
+       case KEY_TYPE_alloc_v3:
+               bch2_alloc_unpack_v3(&ret, k);
+               break;
+       }
 
-       percpu_up_read_preempt_enable(&c->usage_lock);
+       return ret;
 }
 
-int bch2_alloc_read(struct bch_fs *c, struct list_head *journal_replay_list)
+struct bkey_i_alloc_v4 *
+bch2_trans_start_alloc_update(struct btree_trans *trans, struct btree_iter *iter,
+                             struct bpos pos)
 {
-       struct journal_replay *r;
-       struct btree_iter iter;
        struct bkey_s_c k;
-       struct bch_dev *ca;
-       unsigned i;
+       struct bkey_i_alloc_v4 *a;
        int ret;
 
-       for_each_btree_key(&iter, c, BTREE_ID_ALLOC, POS_MIN, 0, k) {
-               bch2_alloc_read_key(c, k);
-               bch2_btree_iter_cond_resched(&iter);
+       bch2_trans_iter_init(trans, iter, BTREE_ID_alloc, pos,
+                            BTREE_ITER_WITH_UPDATES|
+                            BTREE_ITER_CACHED|
+                            BTREE_ITER_INTENT);
+       k = bch2_btree_iter_peek_slot(iter);
+       ret = bkey_err(k);
+       if (ret) {
+               bch2_trans_iter_exit(trans, iter);
+               return ERR_PTR(ret);
        }
 
-       ret = bch2_btree_iter_unlock(&iter);
-       if (ret)
-               return ret;
+       a = bch2_alloc_to_v4_mut(trans, k);
+       if (IS_ERR(a))
+               bch2_trans_iter_exit(trans, iter);
+       return a;
+}
+
+static unsigned bch_alloc_v1_val_u64s(const struct bch_alloc *a)
+{
+       unsigned i, bytes = offsetof(struct bch_alloc, data);
+
+       for (i = 0; i < ARRAY_SIZE(BCH_ALLOC_V1_FIELD_BYTES); i++)
+               if (a->fields & (1 << i))
+                       bytes += BCH_ALLOC_V1_FIELD_BYTES[i];
 
-       list_for_each_entry(r, journal_replay_list, list) {
-               struct bkey_i *k, *n;
-               struct jset_entry *entry;
+       return DIV_ROUND_UP(bytes, sizeof(u64));
+}
+
+int bch2_alloc_v1_invalid(const struct bch_fs *c, struct bkey_s_c k,
+                         int rw, struct printbuf *err)
+{
+       struct bkey_s_c_alloc a = bkey_s_c_to_alloc(k);
 
-               for_each_jset_key(k, n, entry, &r->j)
-                       if (entry->btree_id == BTREE_ID_ALLOC)
-                               bch2_alloc_read_key(c, bkey_i_to_s_c(k));
+       /* allow for unknown fields */
+       if (bkey_val_u64s(a.k) < bch_alloc_v1_val_u64s(a.v)) {
+               prt_printf(err, "incorrect value size (%zu < %u)",
+                      bkey_val_u64s(a.k), bch_alloc_v1_val_u64s(a.v));
+               return -EINVAL;
        }
 
-       mutex_lock(&c->bucket_clock[READ].lock);
-       for_each_member_device(ca, c, i) {
-               down_read(&ca->bucket_lock);
-               bch2_recalc_oldest_io(c, ca, READ);
-               up_read(&ca->bucket_lock);
+       return 0;
+}
+
+int bch2_alloc_v2_invalid(const struct bch_fs *c, struct bkey_s_c k,
+                         int rw, struct printbuf *err)
+{
+       struct bkey_alloc_unpacked u;
+
+       if (bch2_alloc_unpack_v2(&u, k)) {
+               prt_printf(err, "unpack error");
+               return -EINVAL;
        }
-       mutex_unlock(&c->bucket_clock[READ].lock);
 
-       mutex_lock(&c->bucket_clock[WRITE].lock);
-       for_each_member_device(ca, c, i) {
-               down_read(&ca->bucket_lock);
-               bch2_recalc_oldest_io(c, ca, WRITE);
-               up_read(&ca->bucket_lock);
+       return 0;
+}
+
+int bch2_alloc_v3_invalid(const struct bch_fs *c, struct bkey_s_c k,
+                         int rw, struct printbuf *err)
+{
+       struct bkey_alloc_unpacked u;
+
+       if (bch2_alloc_unpack_v3(&u, k)) {
+               prt_printf(err, "unpack error");
+               return -EINVAL;
        }
-       mutex_unlock(&c->bucket_clock[WRITE].lock);
 
        return 0;
 }
 
-static int __bch2_alloc_write_key(struct bch_fs *c, struct bch_dev *ca,
-                                 size_t b, struct btree_iter *iter,
-                                 u64 *journal_seq, unsigned flags)
+int bch2_alloc_v4_invalid(const struct bch_fs *c, struct bkey_s_c k,
+                         int rw, struct printbuf *err)
 {
-       struct bucket_mark m;
-       __BKEY_PADDED(k, DIV_ROUND_UP(sizeof(struct bch_alloc), 8)) alloc_key;
-       struct bucket *g;
-       struct bkey_i_alloc *a;
-       int ret;
-       u8 *d;
+       struct bkey_s_c_alloc_v4 a = bkey_s_c_to_alloc_v4(k);
 
-       percpu_down_read_preempt_disable(&c->usage_lock);
-       g = bucket(ca, b);
+       if (alloc_v4_u64s(a.v) != bkey_val_u64s(k.k)) {
+               prt_printf(err, "bad val size (%lu != %u)",
+                      bkey_val_u64s(k.k), alloc_v4_u64s(a.v));
+               return -EINVAL;
+       }
 
-       m = READ_ONCE(g->mark);
-       a = bkey_alloc_init(&alloc_key.k);
-       a->k.p          = POS(ca->dev_idx, b);
-       a->v.fields     = 0;
-       a->v.gen        = m.gen;
-       set_bkey_val_u64s(&a->k, bch_alloc_val_u64s(&a->v));
+       if (!BCH_ALLOC_V4_BACKPOINTERS_START(a.v) &&
+           BCH_ALLOC_V4_NR_BACKPOINTERS(a.v)) {
+               prt_printf(err, "invalid backpointers_start");
+               return -EINVAL;
+       }
 
-       d = a->v.data;
-       if (a->v.fields & (1 << BCH_ALLOC_FIELD_READ_TIME))
-               put_alloc_field(&d, 2, g->io_time[READ]);
-       if (a->v.fields & (1 << BCH_ALLOC_FIELD_WRITE_TIME))
-               put_alloc_field(&d, 2, g->io_time[WRITE]);
-       percpu_up_read_preempt_enable(&c->usage_lock);
+       if (rw == WRITE) {
+               if (alloc_data_type(*a.v, a.v->data_type) != a.v->data_type) {
+                       prt_printf(err, "invalid data type (got %u should be %u)",
+                              a.v->data_type, alloc_data_type(*a.v, a.v->data_type));
+                       return -EINVAL;
+               }
 
-       bch2_btree_iter_cond_resched(iter);
+               switch (a.v->data_type) {
+               case BCH_DATA_free:
+               case BCH_DATA_need_gc_gens:
+               case BCH_DATA_need_discard:
+                       if (a.v->dirty_sectors ||
+                           a.v->cached_sectors ||
+                           a.v->stripe) {
+                               prt_printf(err, "empty data type free but have data");
+                               return -EINVAL;
+                       }
+                       break;
+               case BCH_DATA_sb:
+               case BCH_DATA_journal:
+               case BCH_DATA_btree:
+               case BCH_DATA_user:
+               case BCH_DATA_parity:
+                       if (!a.v->dirty_sectors) {
+                               prt_printf(err, "data_type %s but dirty_sectors==0",
+                                      bch2_data_types[a.v->data_type]);
+                               return -EINVAL;
+                       }
+                       break;
+               case BCH_DATA_cached:
+                       if (!a.v->cached_sectors ||
+                           a.v->dirty_sectors ||
+                           a.v->stripe) {
+                               prt_printf(err, "data type inconsistency");
+                               return -EINVAL;
+                       }
 
-       bch2_btree_iter_set_pos(iter, a->k.p);
+                       if (!a.v->io_time[READ] &&
+                           test_bit(BCH_FS_CHECK_ALLOC_TO_LRU_REFS_DONE, &c->flags)) {
+                               prt_printf(err, "cached bucket with read_time == 0");
+                               return -EINVAL;
+                       }
+                       break;
+               case BCH_DATA_stripe:
+                       if (!a.v->stripe) {
+                               prt_printf(err, "data_type %s but stripe==0",
+                                      bch2_data_types[a.v->data_type]);
+                               return -EINVAL;
+                       }
+                       break;
+               }
+       }
 
-       ret = bch2_btree_insert_at(c, NULL, journal_seq,
-                                  BTREE_INSERT_NOFAIL|
-                                  BTREE_INSERT_USE_RESERVE|
-                                  BTREE_INSERT_USE_ALLOC_RESERVE|
-                                  flags,
-                                  BTREE_INSERT_ENTRY(iter, &a->k_i));
+       return 0;
+}
 
-       if (!ret && ca->buckets_written)
-               set_bit(b, ca->buckets_written);
+static inline u64 swab40(u64 x)
+{
+       return (((x & 0x00000000ffULL) << 32)|
+               ((x & 0x000000ff00ULL) << 16)|
+               ((x & 0x0000ff0000ULL) >>  0)|
+               ((x & 0x00ff000000ULL) >> 16)|
+               ((x & 0xff00000000ULL) >> 32));
+}
 
-       return ret;
+void bch2_alloc_v4_swab(struct bkey_s k)
+{
+       struct bch_alloc_v4 *a = bkey_s_to_alloc_v4(k).v;
+       struct bch_backpointer *bp, *bps;
+
+       a->journal_seq          = swab64(a->journal_seq);
+       a->flags                = swab32(a->flags);
+       a->dirty_sectors        = swab32(a->dirty_sectors);
+       a->cached_sectors       = swab32(a->cached_sectors);
+       a->io_time[0]           = swab64(a->io_time[0]);
+       a->io_time[1]           = swab64(a->io_time[1]);
+       a->stripe               = swab32(a->stripe);
+       a->nr_external_backpointers = swab32(a->nr_external_backpointers);
+
+       bps = alloc_v4_backpointers(a);
+       for (bp = bps; bp < bps + BCH_ALLOC_V4_NR_BACKPOINTERS(a); bp++) {
+               bp->bucket_offset       = swab40(bp->bucket_offset);
+               bp->bucket_len          = swab32(bp->bucket_len);
+               bch2_bpos_swab(&bp->pos);
+       }
 }
 
-int bch2_alloc_replay_key(struct bch_fs *c, struct bkey_i *k)
+void bch2_alloc_to_text(struct printbuf *out, struct bch_fs *c, struct bkey_s_c k)
 {
-       struct bch_dev *ca;
-       struct btree_iter iter;
-       int ret;
+       struct bch_alloc_v4 _a;
+       const struct bch_alloc_v4 *a = &_a;
+       const struct bch_backpointer *bps;
+       unsigned i;
 
-       if (k->k.p.inode >= c->sb.nr_devices ||
-           !c->devs[k->k.p.inode])
-               return 0;
+       if (k.k->type == KEY_TYPE_alloc_v4)
+               a = bkey_s_c_to_alloc_v4(k).v;
+       else
+               bch2_alloc_to_v4(k, &_a);
+
+       prt_newline(out);
+       printbuf_indent_add(out, 2);
+
+       prt_printf(out, "gen %u oldest_gen %u data_type %s",
+              a->gen, a->oldest_gen, bch2_data_types[a->data_type]);
+       prt_newline(out);
+       prt_printf(out, "journal_seq       %llu",       a->journal_seq);
+       prt_newline(out);
+       prt_printf(out, "need_discard      %llu",       BCH_ALLOC_V4_NEED_DISCARD(a));
+       prt_newline(out);
+       prt_printf(out, "need_inc_gen      %llu",       BCH_ALLOC_V4_NEED_INC_GEN(a));
+       prt_newline(out);
+       prt_printf(out, "dirty_sectors     %u", a->dirty_sectors);
+       prt_newline(out);
+       prt_printf(out, "cached_sectors    %u", a->cached_sectors);
+       prt_newline(out);
+       prt_printf(out, "stripe            %u", a->stripe);
+       prt_newline(out);
+       prt_printf(out, "stripe_redundancy %u", a->stripe_redundancy);
+       prt_newline(out);
+       prt_printf(out, "io_time[READ]     %llu",       a->io_time[READ]);
+       prt_newline(out);
+       prt_printf(out, "io_time[WRITE]    %llu",       a->io_time[WRITE]);
+       prt_newline(out);
+       prt_printf(out, "backpointers:     %llu",       BCH_ALLOC_V4_NR_BACKPOINTERS(a));
+       printbuf_indent_add(out, 2);
+
+       bps = alloc_v4_backpointers_c(a);
+       for (i = 0; i < BCH_ALLOC_V4_NR_BACKPOINTERS(a); i++) {
+               prt_newline(out);
+               bch2_backpointer_to_text(out, &bps[i]);
+       }
 
-       ca = bch_dev_bkey_exists(c, k->k.p.inode);
+       printbuf_indent_sub(out, 4);
+}
 
-       if (k->k.p.offset >= ca->mi.nbuckets)
-               return 0;
+void bch2_alloc_to_v4(struct bkey_s_c k, struct bch_alloc_v4 *out)
+{
+       if (k.k->type == KEY_TYPE_alloc_v4) {
+               int d;
+
+               *out = *bkey_s_c_to_alloc_v4(k).v;
+
+               d = (int) BCH_ALLOC_V4_U64s -
+                       (int) (BCH_ALLOC_V4_BACKPOINTERS_START(out) ?: BCH_ALLOC_V4_U64s_V0);
+               if (unlikely(d > 0)) {
+                       memset((u64 *) out + BCH_ALLOC_V4_BACKPOINTERS_START(out),
+                              0,
+                              d * sizeof(u64));
+                       SET_BCH_ALLOC_V4_BACKPOINTERS_START(out, BCH_ALLOC_V4_U64s);
+               }
+       } else {
+               struct bkey_alloc_unpacked u = bch2_alloc_unpack(k);
+
+               *out = (struct bch_alloc_v4) {
+                       .journal_seq            = u.journal_seq,
+                       .flags                  = u.need_discard,
+                       .gen                    = u.gen,
+                       .oldest_gen             = u.oldest_gen,
+                       .data_type              = u.data_type,
+                       .stripe_redundancy      = u.stripe_redundancy,
+                       .dirty_sectors          = u.dirty_sectors,
+                       .cached_sectors         = u.cached_sectors,
+                       .io_time[READ]          = u.read_time,
+                       .io_time[WRITE]         = u.write_time,
+                       .stripe                 = u.stripe,
+               };
+
+               SET_BCH_ALLOC_V4_BACKPOINTERS_START(out, BCH_ALLOC_V4_U64s);
+       }
+}
 
-       bch2_btree_iter_init(&iter, c, BTREE_ID_ALLOC, k->k.p,
-                            BTREE_ITER_INTENT);
+struct bkey_i_alloc_v4 *bch2_alloc_to_v4_mut(struct btree_trans *trans, struct bkey_s_c k)
+{
+       unsigned bytes = k.k->type == KEY_TYPE_alloc_v4
+               ? bkey_bytes(k.k)
+               : sizeof(struct bkey_i_alloc_v4);
+       struct bkey_i_alloc_v4 *ret;
 
-       ret = bch2_btree_iter_traverse(&iter);
-       if (ret)
-               goto err;
+       /*
+        * Reserve space for one more backpointer here:
+        * Not sketchy at doing it this way, nope...
+        */
+       ret = bch2_trans_kmalloc(trans, bytes + sizeof(struct bch_backpointer));
+       if (IS_ERR(ret))
+               return ret;
 
-       /* check buckets_written with btree node locked: */
+       if (k.k->type == KEY_TYPE_alloc_v4) {
+               bkey_reassemble(&ret->k_i, k);
 
-       ret = test_bit(k->k.p.offset, ca->buckets_written)
-               ? 0
-               : bch2_btree_insert_at(c, NULL, NULL,
-                                      BTREE_INSERT_NOFAIL|
-                                      BTREE_INSERT_JOURNAL_REPLAY,
-                                      BTREE_INSERT_ENTRY(&iter, k));
-err:
-       bch2_btree_iter_unlock(&iter);
+               if (BCH_ALLOC_V4_BACKPOINTERS_START(&ret->v) < BCH_ALLOC_V4_U64s) {
+                       struct bch_backpointer *src, *dst;
+
+                       src = alloc_v4_backpointers(&ret->v);
+                       SET_BCH_ALLOC_V4_BACKPOINTERS_START(&ret->v, BCH_ALLOC_V4_U64s);
+                       dst = alloc_v4_backpointers(&ret->v);
+
+                       memmove(dst, src, BCH_ALLOC_V4_NR_BACKPOINTERS(&ret->v) *
+                               sizeof(struct bch_backpointer));
+                       memset(src, 0, dst - src);
+                       set_alloc_v4_u64s(ret);
+               }
+       } else {
+               bkey_alloc_v4_init(&ret->k_i);
+               ret->k.p = k.k->p;
+               bch2_alloc_to_v4(k, &ret->v);
+       }
        return ret;
 }
 
-int bch2_alloc_write(struct bch_fs *c)
+int bch2_alloc_read(struct bch_fs *c)
 {
+       struct btree_trans trans;
+       struct btree_iter iter;
+       struct bkey_s_c k;
+       struct bch_alloc_v4 a;
        struct bch_dev *ca;
-       unsigned i;
-       int ret = 0;
-
-       for_each_rw_member(ca, c, i) {
-               struct btree_iter iter;
-               unsigned long bucket;
+       int ret;
 
-               bch2_btree_iter_init(&iter, c, BTREE_ID_ALLOC, POS_MIN,
-                                    BTREE_ITER_SLOTS|BTREE_ITER_INTENT);
+       bch2_trans_init(&trans, c, 0, 0);
 
-               down_read(&ca->bucket_lock);
-               for_each_set_bit(bucket, ca->buckets_dirty, ca->mi.nbuckets) {
-                       ret = __bch2_alloc_write_key(c, ca, bucket,
-                                                    &iter, NULL, 0);
-                       if (ret)
-                               break;
+       for_each_btree_key(&trans, iter, BTREE_ID_alloc, POS_MIN,
+                          BTREE_ITER_PREFETCH, k, ret) {
+               /*
+                * Not a fsck error because this is checked/repaired by
+                * bch2_check_alloc_key() which runs later:
+                */
+               if (!bch2_dev_bucket_exists(c, k.k->p))
+                       continue;
 
-                       clear_bit(bucket, ca->buckets_dirty);
-               }
-               up_read(&ca->bucket_lock);
-               bch2_btree_iter_unlock(&iter);
+               ca = bch_dev_bkey_exists(c, k.k->p.inode);
+               bch2_alloc_to_v4(k, &a);
 
-               if (ret) {
-                       percpu_ref_put(&ca->io_ref);
-                       break;
-               }
+               *bucket_gen(ca, k.k->p.offset) = a.gen;
        }
+       bch2_trans_iter_exit(&trans, &iter);
+
+       bch2_trans_exit(&trans);
+
+       if (ret)
+               bch_err(c, "error reading alloc info: %i", ret);
 
        return ret;
 }
 
-/* Bucket IO clocks: */
+/* Free space/discard btree: */
 
-static void bch2_recalc_oldest_io(struct bch_fs *c, struct bch_dev *ca, int rw)
+static int bch2_bucket_do_index(struct btree_trans *trans,
+                               struct bkey_s_c alloc_k,
+                               const struct bch_alloc_v4 *a,
+                               bool set)
 {
-       struct bucket_clock *clock = &c->bucket_clock[rw];
-       struct bucket_array *buckets = bucket_array(ca);
-       struct bucket *g;
-       u16 max_last_io = 0;
-       unsigned i;
+       struct bch_fs *c = trans->c;
+       struct bch_dev *ca = bch_dev_bkey_exists(c, alloc_k.k->p.inode);
+       struct btree_iter iter;
+       struct bkey_s_c old;
+       struct bkey_i *k;
+       enum btree_id btree;
+       enum bch_bkey_type old_type = !set ? KEY_TYPE_set : KEY_TYPE_deleted;
+       enum bch_bkey_type new_type =  set ? KEY_TYPE_set : KEY_TYPE_deleted;
+       struct printbuf buf = PRINTBUF;
+       int ret;
+
+       if (a->data_type != BCH_DATA_free &&
+           a->data_type != BCH_DATA_need_discard)
+               return 0;
 
-       lockdep_assert_held(&c->bucket_clock[rw].lock);
+       k = bch2_trans_kmalloc(trans, sizeof(*k));
+       if (IS_ERR(k))
+               return PTR_ERR(k);
 
-       /* Recalculate max_last_io for this device: */
-       for_each_bucket(g, buckets)
-               max_last_io = max(max_last_io, bucket_last_io(c, g, rw));
+       bkey_init(&k->k);
+       k->k.type = new_type;
 
-       ca->max_last_bucket_io[rw] = max_last_io;
+       switch (a->data_type) {
+       case BCH_DATA_free:
+               btree = BTREE_ID_freespace;
+               k->k.p = alloc_freespace_pos(alloc_k.k->p, *a);
+               bch2_key_resize(&k->k, 1);
+               break;
+       case BCH_DATA_need_discard:
+               btree = BTREE_ID_need_discard;
+               k->k.p = alloc_k.k->p;
+               break;
+       default:
+               return 0;
+       }
 
-       /* Recalculate global max_last_io: */
-       max_last_io = 0;
+       bch2_trans_iter_init(trans, &iter, btree,
+                            bkey_start_pos(&k->k),
+                            BTREE_ITER_INTENT);
+       old = bch2_btree_iter_peek_slot(&iter);
+       ret = bkey_err(old);
+       if (ret)
+               goto err;
 
-       for_each_member_device(ca, c, i)
-               max_last_io = max(max_last_io, ca->max_last_bucket_io[rw]);
+       if (ca->mi.freespace_initialized &&
+           bch2_trans_inconsistent_on(old.k->type != old_type, trans,
+                       "incorrect key when %s %s btree (got %s should be %s)\n"
+                       "  for %s",
+                       set ? "setting" : "clearing",
+                       bch2_btree_ids[btree],
+                       bch2_bkey_types[old.k->type],
+                       bch2_bkey_types[old_type],
+                       (bch2_bkey_val_to_text(&buf, c, alloc_k), buf.buf))) {
+               ret = -EIO;
+               goto err;
+       }
 
-       clock->max_last_io = max_last_io;
+       ret = bch2_trans_update(trans, &iter, k, 0);
+err:
+       bch2_trans_iter_exit(trans, &iter);
+       printbuf_exit(&buf);
+       return ret;
 }
 
-static void bch2_rescale_bucket_io_times(struct bch_fs *c, int rw)
+int bch2_trans_mark_alloc(struct btree_trans *trans,
+                         enum btree_id btree_id, unsigned level,
+                         struct bkey_s_c old, struct bkey_i *new,
+                         unsigned flags)
 {
-       struct bucket_clock *clock = &c->bucket_clock[rw];
-       struct bucket_array *buckets;
-       struct bch_dev *ca;
-       struct bucket *g;
-       unsigned i;
+       struct bch_fs *c = trans->c;
+       struct bch_alloc_v4 old_a, *new_a;
+       u64 old_lru, new_lru;
+       int ret = 0;
 
-       trace_rescale_prios(c);
+       /*
+        * Deletion only happens in the device removal path, with
+        * BTREE_TRIGGER_NORUN:
+        */
+       BUG_ON(new->k.type != KEY_TYPE_alloc_v4);
 
-       for_each_member_device(ca, c, i) {
-               down_read(&ca->bucket_lock);
-               buckets = bucket_array(ca);
+       bch2_alloc_to_v4(old, &old_a);
+       new_a = &bkey_i_to_alloc_v4(new)->v;
 
-               for_each_bucket(g, buckets)
-                       g->io_time[rw] = clock->hand -
-                       bucket_last_io(c, g, rw) / 2;
+       new_a->data_type = alloc_data_type(*new_a, new_a->data_type);
 
-               bch2_recalc_oldest_io(c, ca, rw);
+       if (new_a->dirty_sectors > old_a.dirty_sectors ||
+           new_a->cached_sectors > old_a.cached_sectors) {
+               new_a->io_time[READ] = max_t(u64, 1, atomic64_read(&c->io_clock[READ].now));
+               new_a->io_time[WRITE]= max_t(u64, 1, atomic64_read(&c->io_clock[WRITE].now));
+               SET_BCH_ALLOC_V4_NEED_INC_GEN(new_a, true);
+               SET_BCH_ALLOC_V4_NEED_DISCARD(new_a, true);
+       }
 
-               up_read(&ca->bucket_lock);
+       if (data_type_is_empty(new_a->data_type) &&
+           BCH_ALLOC_V4_NEED_INC_GEN(new_a) &&
+           !bch2_bucket_is_open_safe(c, new->k.p.inode, new->k.p.offset)) {
+               new_a->gen++;
+               SET_BCH_ALLOC_V4_NEED_INC_GEN(new_a, false);
        }
-}
 
-static inline u64 bucket_clock_freq(u64 capacity)
-{
-       return max(capacity >> 10, 2028ULL);
+       if (old_a.data_type != new_a->data_type ||
+           (new_a->data_type == BCH_DATA_free &&
+            alloc_freespace_genbits(old_a) != alloc_freespace_genbits(*new_a))) {
+               ret =   bch2_bucket_do_index(trans, old, &old_a, false) ?:
+                       bch2_bucket_do_index(trans, bkey_i_to_s_c(new), new_a, true);
+               if (ret)
+                       return ret;
+       }
+
+       if (new_a->data_type == BCH_DATA_cached &&
+           !new_a->io_time[READ])
+               new_a->io_time[READ] = max_t(u64, 1, atomic64_read(&c->io_clock[READ].now));
+
+       old_lru = alloc_lru_idx(old_a);
+       new_lru = alloc_lru_idx(*new_a);
+
+       if (old_lru != new_lru) {
+               ret = bch2_lru_change(trans, new->k.p.inode, new->k.p.offset,
+                                     old_lru, &new_lru, old);
+               if (ret)
+                       return ret;
+
+               if (new_a->data_type == BCH_DATA_cached)
+                       new_a->io_time[READ] = new_lru;
+       }
+
+       return 0;
 }
 
-static void bch2_inc_clock_hand(struct io_timer *timer)
+static int bch2_check_alloc_key(struct btree_trans *trans,
+                               struct btree_iter *alloc_iter,
+                               struct btree_iter *discard_iter,
+                               struct btree_iter *freespace_iter)
 {
-       struct bucket_clock *clock = container_of(timer,
-                                               struct bucket_clock, rescale);
-       struct bch_fs *c = container_of(clock,
-                                       struct bch_fs, bucket_clock[clock->rw]);
+       struct bch_fs *c = trans->c;
        struct bch_dev *ca;
-       u64 capacity;
-       unsigned i;
+       struct bch_alloc_v4 a;
+       unsigned discard_key_type, freespace_key_type;
+       struct bkey_s_c alloc_k, k;
+       struct printbuf buf = PRINTBUF;
+       int ret;
 
-       mutex_lock(&clock->lock);
+       alloc_k = bch2_dev_bucket_exists(c, alloc_iter->pos)
+               ? bch2_btree_iter_peek_slot(alloc_iter)
+               : bch2_btree_iter_peek(alloc_iter);
+       if (!alloc_k.k)
+               return 1;
 
-       /* if clock cannot be advanced more, rescale prio */
-       if (clock->max_last_io >= U16_MAX - 2)
-               bch2_rescale_bucket_io_times(c, clock->rw);
+       ret = bkey_err(alloc_k);
+       if (ret)
+               return ret;
 
-       BUG_ON(clock->max_last_io >= U16_MAX - 2);
+       if (fsck_err_on(!bch2_dev_bucket_exists(c, alloc_k.k->p), c,
+                       "alloc key for invalid device:bucket %llu:%llu",
+                       alloc_k.k->p.inode, alloc_k.k->p.offset))
+               return bch2_btree_delete_at(trans, alloc_iter, 0);
 
-       for_each_member_device(ca, c, i)
-               ca->max_last_bucket_io[clock->rw]++;
-       clock->max_last_io++;
-       clock->hand++;
+       ca = bch_dev_bkey_exists(c, alloc_k.k->p.inode);
+       if (!ca->mi.freespace_initialized)
+               return 0;
 
-       mutex_unlock(&clock->lock);
+       bch2_alloc_to_v4(alloc_k, &a);
 
-       capacity = READ_ONCE(c->capacity);
+       discard_key_type = a.data_type == BCH_DATA_need_discard
+               ? KEY_TYPE_set : 0;
+       freespace_key_type = a.data_type == BCH_DATA_free
+               ? KEY_TYPE_set : 0;
 
-       if (!capacity)
-               return;
+       bch2_btree_iter_set_pos(discard_iter, alloc_k.k->p);
+       bch2_btree_iter_set_pos(freespace_iter, alloc_freespace_pos(alloc_k.k->p, a));
 
-       /*
-        * we only increment when 0.1% of the filesystem capacity has been read
-        * or written too, this determines if it's time
-        *
-        * XXX: we shouldn't really be going off of the capacity of devices in
-        * RW mode (that will be 0 when we're RO, yet we can still service
-        * reads)
-        */
-       timer->expire += bucket_clock_freq(capacity);
+       k = bch2_btree_iter_peek_slot(discard_iter);
+       ret = bkey_err(k);
+       if (ret)
+               goto err;
 
-       bch2_io_timer_add(&c->io_clock[clock->rw], timer);
-}
+       if (k.k->type != discard_key_type &&
+           (c->opts.reconstruct_alloc ||
+            fsck_err(c, "incorrect key in need_discard btree (got %s should be %s)\n"
+                     "  %s",
+                     bch2_bkey_types[k.k->type],
+                     bch2_bkey_types[discard_key_type],
+                     (bch2_bkey_val_to_text(&buf, c, alloc_k), buf.buf)))) {
+               struct bkey_i *update =
+                       bch2_trans_kmalloc(trans, sizeof(*update));
+
+               ret = PTR_ERR_OR_ZERO(update);
+               if (ret)
+                       goto err;
 
-static void bch2_bucket_clock_init(struct bch_fs *c, int rw)
-{
-       struct bucket_clock *clock = &c->bucket_clock[rw];
+               bkey_init(&update->k);
+               update->k.type  = discard_key_type;
+               update->k.p     = discard_iter->pos;
 
-       clock->hand             = 1;
-       clock->rw               = rw;
-       clock->rescale.fn       = bch2_inc_clock_hand;
-       clock->rescale.expire   = bucket_clock_freq(c->capacity);
-       mutex_init(&clock->lock);
-}
+               ret = bch2_trans_update(trans, discard_iter, update, 0);
+               if (ret)
+                       goto err;
+       }
 
-/* Background allocator thread: */
+       k = bch2_btree_iter_peek_slot(freespace_iter);
+       ret = bkey_err(k);
+       if (ret)
+               goto err;
 
-/*
- * Scans for buckets to be invalidated, invalidates them, rewrites prios/gens
- * (marking them as invalidated on disk), then optionally issues discard
- * commands to the newly free buckets, then puts them on the various freelists.
- */
+       if (k.k->type != freespace_key_type &&
+           (c->opts.reconstruct_alloc ||
+            fsck_err(c, "incorrect key in freespace btree (got %s should be %s)\n"
+                     "  %s",
+                     bch2_bkey_types[k.k->type],
+                     bch2_bkey_types[freespace_key_type],
+                     (printbuf_reset(&buf),
+                      bch2_bkey_val_to_text(&buf, c, alloc_k), buf.buf)))) {
+               struct bkey_i *update =
+                       bch2_trans_kmalloc(trans, sizeof(*update));
+
+               ret = PTR_ERR_OR_ZERO(update);
+               if (ret)
+                       goto err;
 
-#define BUCKET_GC_GEN_MAX      96U
+               bkey_init(&update->k);
+               update->k.type  = freespace_key_type;
+               update->k.p     = freespace_iter->pos;
+               bch2_key_resize(&update->k, 1);
+
+               ret = bch2_trans_update(trans, freespace_iter, update, 0);
+               if (ret)
+                       goto err;
+       }
+err:
+fsck_err:
+       printbuf_exit(&buf);
+       return ret;
+}
 
-/**
- * wait_buckets_available - wait on reclaimable buckets
- *
- * If there aren't enough available buckets to fill up free_inc, wait until
- * there are.
- */
-static int wait_buckets_available(struct bch_fs *c, struct bch_dev *ca)
+static int bch2_check_discard_freespace_key(struct btree_trans *trans,
+                                           struct btree_iter *iter)
 {
-       unsigned long gc_count = c->gc_count;
-       int ret = 0;
+       struct bch_fs *c = trans->c;
+       struct btree_iter alloc_iter;
+       struct bkey_s_c k, freespace_k;
+       struct bch_alloc_v4 a;
+       u64 genbits;
+       struct bpos pos;
+       enum bch_data_type state = iter->btree_id == BTREE_ID_need_discard
+               ? BCH_DATA_need_discard
+               : BCH_DATA_free;
+       struct printbuf buf = PRINTBUF;
+       int ret;
 
-       while (1) {
-               set_current_state(TASK_INTERRUPTIBLE);
-               if (kthread_should_stop()) {
-                       ret = 1;
-                       break;
-               }
+       freespace_k = bch2_btree_iter_peek(iter);
+       if (!freespace_k.k)
+               return 1;
 
-               if (gc_count != c->gc_count)
-                       ca->inc_gen_really_needs_gc = 0;
+       ret = bkey_err(freespace_k);
+       if (ret)
+               return ret;
 
-               if ((ssize_t) (dev_buckets_available(c, ca) -
-                              ca->inc_gen_really_needs_gc) >=
-                   (ssize_t) fifo_free(&ca->free_inc))
-                       break;
+       pos = iter->pos;
+       pos.offset &= ~(~0ULL << 56);
+       genbits = iter->pos.offset & (~0ULL << 56);
 
-               up_read(&c->gc_lock);
-               schedule();
-               try_to_freeze();
-               down_read(&c->gc_lock);
-       }
+       bch2_trans_iter_init(trans, &alloc_iter, BTREE_ID_alloc, pos, 0);
 
-       __set_current_state(TASK_RUNNING);
+       if (fsck_err_on(!bch2_dev_bucket_exists(c, pos), c,
+                       "entry in %s btree for nonexistant dev:bucket %llu:%llu",
+                       bch2_btree_ids[iter->btree_id], pos.inode, pos.offset))
+               goto delete;
+
+       k = bch2_btree_iter_peek_slot(&alloc_iter);
+       ret = bkey_err(k);
+       if (ret)
+               goto err;
+
+       bch2_alloc_to_v4(k, &a);
+
+       if (fsck_err_on(a.data_type != state ||
+                       (state == BCH_DATA_free &&
+                        genbits != alloc_freespace_genbits(a)), c,
+                       "%s\n  incorrectly set in %s index (free %u, genbits %llu should be %llu)",
+                       (bch2_bkey_val_to_text(&buf, c, k), buf.buf),
+                       bch2_btree_ids[iter->btree_id],
+                       a.data_type == state,
+                       genbits >> 56, alloc_freespace_genbits(a) >> 56))
+               goto delete;
+out:
+err:
+fsck_err:
+       bch2_trans_iter_exit(trans, &alloc_iter);
+       printbuf_exit(&buf);
        return ret;
+delete:
+       ret = bch2_btree_delete_extent_at(trans, iter,
+                       iter->btree_id == BTREE_ID_freespace ? 1 : 0, 0);
+       goto out;
 }
 
-static bool bch2_can_invalidate_bucket(struct bch_dev *ca,
-                                      size_t bucket,
-                                      struct bucket_mark mark)
+int bch2_check_alloc_info(struct bch_fs *c)
 {
-       u8 gc_gen;
+       struct btree_trans trans;
+       struct btree_iter iter, discard_iter, freespace_iter;
+       int ret = 0;
+
+       bch2_trans_init(&trans, c, 0, 0);
+
+       bch2_trans_iter_init(&trans, &iter, BTREE_ID_alloc, POS_MIN,
+                            BTREE_ITER_PREFETCH);
+       bch2_trans_iter_init(&trans, &discard_iter, BTREE_ID_need_discard, POS_MIN,
+                            BTREE_ITER_PREFETCH);
+       bch2_trans_iter_init(&trans, &freespace_iter, BTREE_ID_freespace, POS_MIN,
+                            BTREE_ITER_PREFETCH);
+       while (1) {
+               ret = commit_do(&trans, NULL, NULL,
+                                     BTREE_INSERT_NOFAIL|
+                                     BTREE_INSERT_LAZY_RW,
+                       bch2_check_alloc_key(&trans, &iter,
+                                            &discard_iter,
+                                            &freespace_iter));
+               if (ret)
+                       break;
 
-       if (!is_available_bucket(mark))
-               return false;
+               bch2_btree_iter_advance(&iter);
+       }
+       bch2_trans_iter_exit(&trans, &freespace_iter);
+       bch2_trans_iter_exit(&trans, &discard_iter);
+       bch2_trans_iter_exit(&trans, &iter);
 
-       gc_gen = bucket_gc_gen(ca, bucket);
+       if (ret < 0)
+               goto err;
 
-       if (gc_gen >= BUCKET_GC_GEN_MAX / 2)
-               ca->inc_gen_needs_gc++;
+       bch2_trans_iter_init(&trans, &iter, BTREE_ID_need_discard, POS_MIN,
+                            BTREE_ITER_PREFETCH);
+       while (1) {
+               ret = commit_do(&trans, NULL, NULL,
+                                     BTREE_INSERT_NOFAIL|
+                                     BTREE_INSERT_LAZY_RW,
+                       bch2_check_discard_freespace_key(&trans, &iter));
+               if (ret)
+                       break;
 
-       if (gc_gen >= BUCKET_GC_GEN_MAX)
-               ca->inc_gen_really_needs_gc++;
+               bch2_btree_iter_advance(&iter);
+       }
+       bch2_trans_iter_exit(&trans, &iter);
 
-       return gc_gen < BUCKET_GC_GEN_MAX;
+       if (ret < 0)
+               goto err;
+
+       bch2_trans_iter_init(&trans, &iter, BTREE_ID_freespace, POS_MIN,
+                            BTREE_ITER_PREFETCH);
+       while (1) {
+               ret = commit_do(&trans, NULL, NULL,
+                                     BTREE_INSERT_NOFAIL|
+                                     BTREE_INSERT_LAZY_RW,
+                       bch2_check_discard_freespace_key(&trans, &iter));
+               if (ret)
+                       break;
+
+               bch2_btree_iter_advance(&iter);
+       }
+       bch2_trans_iter_exit(&trans, &iter);
+err:
+       bch2_trans_exit(&trans);
+       return ret < 0 ? ret : 0;
 }
 
-/*
- * Determines what order we're going to reuse buckets, smallest bucket_key()
- * first.
- *
- *
- * - We take into account the read prio of the bucket, which gives us an
- *   indication of how hot the data is -- we scale the prio so that the prio
- *   farthest from the clock is worth 1/8th of the closest.
- *
- * - The number of sectors of cached data in the bucket, which gives us an
- *   indication of the cost in cache misses this eviction will cause.
- *
- * - If hotness * sectors used compares equal, we pick the bucket with the
- *   smallest bucket_gc_gen() - since incrementing the same bucket's generation
- *   number repeatedly forces us to run mark and sweep gc to avoid generation
- *   number wraparound.
- */
-
-static unsigned long bucket_sort_key(struct bch_fs *c, struct bch_dev *ca,
-                                    size_t b, struct bucket_mark m)
+static int bch2_check_alloc_to_lru_ref(struct btree_trans *trans,
+                                      struct btree_iter *alloc_iter)
 {
-       unsigned last_io = bucket_last_io(c, bucket(ca, b), READ);
-       unsigned max_last_io = ca->max_last_bucket_io[READ];
+       struct bch_fs *c = trans->c;
+       struct btree_iter lru_iter;
+       struct bch_alloc_v4 a;
+       struct bkey_s_c alloc_k, k;
+       struct printbuf buf = PRINTBUF;
+       struct printbuf buf2 = PRINTBUF;
+       int ret;
 
-       /*
-        * Time since last read, scaled to [0, 8) where larger value indicates
-        * more recently read data:
-        */
-       unsigned long hotness = (max_last_io - last_io) * 7 / max_last_io;
+       alloc_k = bch2_btree_iter_peek(alloc_iter);
+       if (!alloc_k.k)
+               return 0;
 
-       /* How much we want to keep the data in this bucket: */
-       unsigned long data_wantness =
-               (hotness + 1) * bucket_sectors_used(m);
+       ret = bkey_err(alloc_k);
+       if (ret)
+               return ret;
 
-       unsigned long needs_journal_commit =
-               bucket_needs_journal_commit(m, c->journal.last_seq_ondisk);
+       bch2_alloc_to_v4(alloc_k, &a);
 
-       return  (data_wantness << 9) |
-               (needs_journal_commit << 8) |
-               (bucket_gc_gen(ca, b) / 16);
-}
+       if (a.data_type != BCH_DATA_cached)
+               return 0;
 
-static inline int bucket_alloc_cmp(alloc_heap *h,
-                                  struct alloc_heap_entry l,
-                                  struct alloc_heap_entry r)
-{
-       return (l.key > r.key) - (l.key < r.key) ?:
-               (l.nr < r.nr)  - (l.nr  > r.nr) ?:
-               (l.bucket > r.bucket) - (l.bucket < r.bucket);
-}
+       bch2_trans_iter_init(trans, &lru_iter, BTREE_ID_lru,
+                            POS(alloc_k.k->p.inode, a.io_time[READ]), 0);
 
-static inline int bucket_idx_cmp(const void *_l, const void *_r)
-{
-       const struct alloc_heap_entry *l = _l, *r = _r;
+       k = bch2_btree_iter_peek_slot(&lru_iter);
+       ret = bkey_err(k);
+       if (ret)
+               goto err;
+
+       if (fsck_err_on(!a.io_time[READ], c,
+                       "cached bucket with read_time 0\n"
+                       "  %s",
+               (printbuf_reset(&buf),
+                bch2_bkey_val_to_text(&buf, c, alloc_k), buf.buf)) ||
+           fsck_err_on(k.k->type != KEY_TYPE_lru ||
+                       le64_to_cpu(bkey_s_c_to_lru(k).v->idx) != alloc_k.k->p.offset, c,
+                       "incorrect/missing lru entry\n"
+                       "  %s\n"
+                       "  %s",
+                       (printbuf_reset(&buf),
+                        bch2_bkey_val_to_text(&buf, c, alloc_k), buf.buf),
+                       (bch2_bkey_val_to_text(&buf2, c, k), buf2.buf))) {
+               u64 read_time = a.io_time[READ];
+
+               if (!a.io_time[READ])
+                       a.io_time[READ] = atomic64_read(&c->io_clock[READ].now);
+
+               ret = bch2_lru_set(trans,
+                                  alloc_k.k->p.inode,
+                                  alloc_k.k->p.offset,
+                                  &a.io_time[READ]);
+               if (ret)
+                       goto err;
 
-       return (l->bucket > r->bucket) - (l->bucket < r->bucket);
+               if (a.io_time[READ] != read_time) {
+                       struct bkey_i_alloc_v4 *a_mut =
+                               bch2_alloc_to_v4_mut(trans, alloc_k);
+                       ret = PTR_ERR_OR_ZERO(a_mut);
+                       if (ret)
+                               goto err;
+
+                       a_mut->v.io_time[READ] = a.io_time[READ];
+                       ret = bch2_trans_update(trans, alloc_iter,
+                                               &a_mut->k_i, BTREE_TRIGGER_NORUN);
+                       if (ret)
+                               goto err;
+               }
+       }
+err:
+fsck_err:
+       bch2_trans_iter_exit(trans, &lru_iter);
+       printbuf_exit(&buf2);
+       printbuf_exit(&buf);
+       return ret;
 }
 
-static void find_reclaimable_buckets_lru(struct bch_fs *c, struct bch_dev *ca)
+int bch2_check_alloc_to_lru_refs(struct bch_fs *c)
 {
-       struct bucket_array *buckets;
-       struct alloc_heap_entry e = { 0 };
-       size_t b, i, nr = 0;
-
-       ca->alloc_heap.used = 0;
+       struct btree_trans trans;
+       struct btree_iter iter;
+       struct bkey_s_c k;
+       int ret = 0;
 
-       mutex_lock(&c->bucket_clock[READ].lock);
-       down_read(&ca->bucket_lock);
+       bch2_trans_init(&trans, c, 0, 0);
 
-       buckets = bucket_array(ca);
+       for_each_btree_key_commit(&trans, iter, BTREE_ID_alloc,
+                       POS_MIN, BTREE_ITER_PREFETCH, k,
+                       NULL, NULL, BTREE_INSERT_NOFAIL|BTREE_INSERT_LAZY_RW,
+               bch2_check_alloc_to_lru_ref(&trans, &iter));
 
-       bch2_recalc_oldest_io(c, ca, READ);
+       bch2_trans_exit(&trans);
+       return ret < 0 ? ret : 0;
+}
 
-       /*
-        * Find buckets with lowest read priority, by building a maxheap sorted
-        * by read priority and repeatedly replacing the maximum element until
-        * all buckets have been visited.
-        */
-       for (b = ca->mi.first_bucket; b < ca->mi.nbuckets; b++) {
-               struct bucket_mark m = READ_ONCE(buckets->b[b].mark);
-               unsigned long key = bucket_sort_key(c, ca, b, m);
+static int bch2_clear_need_discard(struct btree_trans *trans, struct bpos pos,
+                                  struct bch_dev *ca, bool *discard_done)
+{
+       struct bch_fs *c = trans->c;
+       struct btree_iter iter;
+       struct bkey_s_c k;
+       struct bkey_i_alloc_v4 *a;
+       struct printbuf buf = PRINTBUF;
+       int ret;
 
-               if (!bch2_can_invalidate_bucket(ca, b, m))
-                       continue;
+       bch2_trans_iter_init(trans, &iter, BTREE_ID_alloc, pos,
+                            BTREE_ITER_CACHED);
+       k = bch2_btree_iter_peek_slot(&iter);
+       ret = bkey_err(k);
+       if (ret)
+               goto out;
 
-               if (e.nr && e.bucket + e.nr == b && e.key == key) {
-                       e.nr++;
-               } else {
-                       if (e.nr)
-                               heap_add_or_replace(&ca->alloc_heap, e,
-                                       -bucket_alloc_cmp, NULL);
-
-                       e = (struct alloc_heap_entry) {
-                               .bucket = b,
-                               .nr     = 1,
-                               .key    = key,
-                       };
-               }
+       a = bch2_alloc_to_v4_mut(trans, k);
+       ret = PTR_ERR_OR_ZERO(a);
+       if (ret)
+               goto out;
 
-               cond_resched();
+       if (BCH_ALLOC_V4_NEED_INC_GEN(&a->v)) {
+               a->v.gen++;
+               SET_BCH_ALLOC_V4_NEED_INC_GEN(&a->v, false);
+               goto write;
        }
 
-       if (e.nr)
-               heap_add_or_replace(&ca->alloc_heap, e,
-                               -bucket_alloc_cmp, NULL);
+       if (bch2_trans_inconsistent_on(a->v.journal_seq > c->journal.flushed_seq_ondisk, trans,
+                       "clearing need_discard but journal_seq %llu > flushed_seq %llu\n"
+                       "%s",
+                       a->v.journal_seq,
+                       c->journal.flushed_seq_ondisk,
+                       (bch2_bkey_val_to_text(&buf, c, k), buf.buf))) {
+               ret = -EIO;
+               goto out;
+       }
 
-       for (i = 0; i < ca->alloc_heap.used; i++)
-               nr += ca->alloc_heap.data[i].nr;
+       if (bch2_trans_inconsistent_on(a->v.data_type != BCH_DATA_need_discard, trans,
+                       "bucket incorrectly set in need_discard btree\n"
+                       "%s",
+                       (bch2_bkey_val_to_text(&buf, c, k), buf.buf))) {
+               ret = -EIO;
+               goto out;
+       }
 
-       while (nr - ca->alloc_heap.data[0].nr >= ALLOC_SCAN_BATCH(ca)) {
-               nr -= ca->alloc_heap.data[0].nr;
-               heap_pop(&ca->alloc_heap, e, -bucket_alloc_cmp, NULL);
+       if (!*discard_done && ca->mi.discard && !c->opts.nochanges) {
+               /*
+                * This works without any other locks because this is the only
+                * thread that removes items from the need_discard tree
+                */
+               bch2_trans_unlock(trans);
+               blkdev_issue_discard(ca->disk_sb.bdev,
+                                    k.k->p.offset * ca->mi.bucket_size,
+                                    ca->mi.bucket_size,
+                                    GFP_KERNEL, 0);
+               *discard_done = true;
+
+               ret = bch2_trans_relock(trans) ? 0 : -EINTR;
+               if (ret)
+                       goto out;
        }
 
-       up_read(&ca->bucket_lock);
-       mutex_unlock(&c->bucket_clock[READ].lock);
+       SET_BCH_ALLOC_V4_NEED_DISCARD(&a->v, false);
+       a->v.data_type = alloc_data_type(a->v, a->v.data_type);
+write:
+       ret = bch2_trans_update(trans, &iter, &a->k_i, 0);
+out:
+       bch2_trans_iter_exit(trans, &iter);
+       printbuf_exit(&buf);
+       return ret;
 }
 
-static void find_reclaimable_buckets_fifo(struct bch_fs *c, struct bch_dev *ca)
+static void bch2_do_discards_work(struct work_struct *work)
 {
-       struct bucket_array *buckets = bucket_array(ca);
-       struct bucket_mark m;
-       size_t b, start;
+       struct bch_fs *c = container_of(work, struct bch_fs, discard_work);
+       struct bch_dev *ca = NULL;
+       struct btree_trans trans;
+       struct btree_iter iter;
+       struct bkey_s_c k;
+       u64 seen = 0, open = 0, need_journal_commit = 0, discarded = 0;
+       int ret;
 
-       if (ca->fifo_last_bucket <  ca->mi.first_bucket ||
-           ca->fifo_last_bucket >= ca->mi.nbuckets)
-               ca->fifo_last_bucket = ca->mi.first_bucket;
+       bch2_trans_init(&trans, c, 0, 0);
 
-       start = ca->fifo_last_bucket;
+       for_each_btree_key(&trans, iter, BTREE_ID_need_discard,
+                          POS_MIN, 0, k, ret) {
+               bool discard_done = false;
 
-       do {
-               ca->fifo_last_bucket++;
-               if (ca->fifo_last_bucket == ca->mi.nbuckets)
-                       ca->fifo_last_bucket = ca->mi.first_bucket;
+               if (ca && k.k->p.inode != ca->dev_idx) {
+                       percpu_ref_put(&ca->io_ref);
+                       ca = NULL;
+               }
 
-               b = ca->fifo_last_bucket;
-               m = READ_ONCE(buckets->b[b].mark);
+               if (!ca) {
+                       ca = bch_dev_bkey_exists(c, k.k->p.inode);
+                       if (!percpu_ref_tryget(&ca->io_ref)) {
+                               ca = NULL;
+                               bch2_btree_iter_set_pos(&iter, POS(k.k->p.inode + 1, 0));
+                               continue;
+                       }
+               }
 
-               if (bch2_can_invalidate_bucket(ca, b, m)) {
-                       struct alloc_heap_entry e = { .bucket = b, .nr = 1, };
+               seen++;
 
-                       heap_add(&ca->alloc_heap, e, bucket_alloc_cmp, NULL);
-                       if (heap_full(&ca->alloc_heap))
-                               break;
+               if (bch2_bucket_is_open_safe(c, k.k->p.inode, k.k->p.offset)) {
+                       open++;
+                       continue;
                }
 
-               cond_resched();
-       } while (ca->fifo_last_bucket != start);
-}
+               if (bch2_bucket_needs_journal_commit(&c->buckets_waiting_for_journal,
+                               c->journal.flushed_seq_ondisk,
+                               k.k->p.inode, k.k->p.offset)) {
+                       need_journal_commit++;
+                       continue;
+               }
 
-static void find_reclaimable_buckets_random(struct bch_fs *c, struct bch_dev *ca)
-{
-       struct bucket_array *buckets = bucket_array(ca);
-       struct bucket_mark m;
-       size_t checked, i;
+               ret = commit_do(&trans, NULL, NULL,
+                                     BTREE_INSERT_USE_RESERVE|
+                                     BTREE_INSERT_NOFAIL,
+                               bch2_clear_need_discard(&trans, k.k->p, ca, &discard_done));
+               if (ret)
+                       break;
 
-       for (checked = 0;
-            checked < ca->mi.nbuckets / 2;
-            checked++) {
-               size_t b = bch2_rand_range(ca->mi.nbuckets -
-                                          ca->mi.first_bucket) +
-                       ca->mi.first_bucket;
+               this_cpu_inc(c->counters[BCH_COUNTER_bucket_discard]);
+               discarded++;
+       }
+       bch2_trans_iter_exit(&trans, &iter);
 
-               m = READ_ONCE(buckets->b[b].mark);
+       if (ca)
+               percpu_ref_put(&ca->io_ref);
 
-               if (bch2_can_invalidate_bucket(ca, b, m)) {
-                       struct alloc_heap_entry e = { .bucket = b, .nr = 1, };
+       bch2_trans_exit(&trans);
 
-                       heap_add(&ca->alloc_heap, e, bucket_alloc_cmp, NULL);
-                       if (heap_full(&ca->alloc_heap))
-                               break;
-               }
+       if (need_journal_commit * 2 > seen)
+               bch2_journal_flush_async(&c->journal, NULL);
 
-               cond_resched();
-       }
+       percpu_ref_put(&c->writes);
 
-       sort(ca->alloc_heap.data,
-            ca->alloc_heap.used,
-            sizeof(ca->alloc_heap.data[0]),
-            bucket_idx_cmp, NULL);
+       trace_discard_buckets(c, seen, open, need_journal_commit, discarded, ret);
+}
 
-       /* remove duplicates: */
-       for (i = 0; i + 1 < ca->alloc_heap.used; i++)
-               if (ca->alloc_heap.data[i].bucket ==
-                   ca->alloc_heap.data[i + 1].bucket)
-                       ca->alloc_heap.data[i].nr = 0;
+void bch2_do_discards(struct bch_fs *c)
+{
+       if (percpu_ref_tryget_live(&c->writes) &&
+           !queue_work(system_long_wq, &c->discard_work))
+               percpu_ref_put(&c->writes);
 }
 
-static size_t find_reclaimable_buckets(struct bch_fs *c, struct bch_dev *ca)
+static int invalidate_one_bucket(struct btree_trans *trans, struct bch_dev *ca,
+                                struct bpos *bucket_pos, unsigned *cached_sectors)
 {
-       size_t i, nr = 0;
+       struct bch_fs *c = trans->c;
+       struct btree_iter lru_iter, alloc_iter = { NULL };
+       struct bkey_s_c k;
+       struct bkey_i_alloc_v4 *a;
+       u64 bucket, idx;
+       struct printbuf buf = PRINTBUF;
+       int ret;
 
-       ca->inc_gen_needs_gc                    = 0;
+       bch2_trans_iter_init(trans, &lru_iter, BTREE_ID_lru,
+                            POS(ca->dev_idx, 0), 0);
+next_lru:
+       k = bch2_btree_iter_peek(&lru_iter);
+       ret = bkey_err(k);
+       if (ret)
+               goto out;
 
-       switch (ca->mi.replacement) {
-       case CACHE_REPLACEMENT_LRU:
-               find_reclaimable_buckets_lru(c, ca);
-               break;
-       case CACHE_REPLACEMENT_FIFO:
-               find_reclaimable_buckets_fifo(c, ca);
-               break;
-       case CACHE_REPLACEMENT_RANDOM:
-               find_reclaimable_buckets_random(c, ca);
-               break;
+       if (!k.k || k.k->p.inode != ca->dev_idx) {
+               ret = 1;
+               goto out;
        }
 
-       heap_resort(&ca->alloc_heap, bucket_alloc_cmp, NULL);
+       if (k.k->type != KEY_TYPE_lru) {
+               prt_printf(&buf, "non lru key in lru btree:\n  ");
+               bch2_bkey_val_to_text(&buf, c, k);
 
-       for (i = 0; i < ca->alloc_heap.used; i++)
-               nr += ca->alloc_heap.data[i].nr;
-
-       return nr;
-}
+               if (!test_bit(BCH_FS_CHECK_LRUS_DONE, &c->flags)) {
+                       bch_err(c, "%s", buf.buf);
+                       bch2_btree_iter_advance(&lru_iter);
+                       goto next_lru;
+               } else {
+                       bch2_trans_inconsistent(trans, "%s", buf.buf);
+                       ret = -EINVAL;
+                       goto out;
+               }
+       }
 
-static inline long next_alloc_bucket(struct bch_dev *ca)
-{
-       struct alloc_heap_entry e, *top = ca->alloc_heap.data;
+       idx     = k.k->p.offset;
+       bucket  = le64_to_cpu(bkey_s_c_to_lru(k).v->idx);
 
-       while (ca->alloc_heap.used) {
-               if (top->nr) {
-                       size_t b = top->bucket;
+       *bucket_pos = POS(ca->dev_idx, bucket);
 
-                       top->bucket++;
-                       top->nr--;
-                       return b;
+       a = bch2_trans_start_alloc_update(trans, &alloc_iter, *bucket_pos);
+       ret = PTR_ERR_OR_ZERO(a);
+       if (ret)
+               goto out;
+
+       if (idx != alloc_lru_idx(a->v)) {
+               prt_printf(&buf, "alloc key does not point back to lru entry when invalidating bucket:\n  ");
+               bch2_bkey_val_to_text(&buf, c, bkey_i_to_s_c(&a->k_i));
+               prt_printf(&buf, "\n  ");
+               bch2_bkey_val_to_text(&buf, c, k);
+
+               if (!test_bit(BCH_FS_CHECK_LRUS_DONE, &c->flags)) {
+                       bch_err(c, "%s", buf.buf);
+                       bch2_btree_iter_advance(&lru_iter);
+                       goto next_lru;
+               } else {
+                       bch2_trans_inconsistent(trans, "%s", buf.buf);
+                       ret = -EINVAL;
+                       goto out;
                }
-
-               heap_pop(&ca->alloc_heap, e, bucket_alloc_cmp, NULL);
        }
 
-       return -1;
-}
+       if (!a->v.cached_sectors)
+               bch_err(c, "invalidating empty bucket, confused");
 
-static bool bch2_invalidate_one_bucket(struct bch_fs *c, struct bch_dev *ca,
-                                      size_t bucket, u64 *flush_seq)
-{
-       struct bucket_mark m;
+       *cached_sectors = a->v.cached_sectors;
 
-       percpu_down_read_preempt_disable(&c->usage_lock);
-       spin_lock(&c->freelist_lock);
+       SET_BCH_ALLOC_V4_NEED_INC_GEN(&a->v, false);
+       a->v.gen++;
+       a->v.data_type          = 0;
+       a->v.dirty_sectors      = 0;
+       a->v.cached_sectors     = 0;
+       a->v.io_time[READ]      = atomic64_read(&c->io_clock[READ].now);
+       a->v.io_time[WRITE]     = atomic64_read(&c->io_clock[WRITE].now);
 
-       bch2_invalidate_bucket(c, ca, bucket, &m);
+       ret = bch2_trans_update(trans, &alloc_iter, &a->k_i,
+                               BTREE_TRIGGER_BUCKET_INVALIDATE);
+       if (ret)
+               goto out;
+out:
+       bch2_trans_iter_exit(trans, &alloc_iter);
+       bch2_trans_iter_exit(trans, &lru_iter);
+       printbuf_exit(&buf);
+       return ret;
+}
 
-       verify_not_on_freelist(c, ca, bucket);
-       BUG_ON(!fifo_push(&ca->free_inc, bucket));
+static void bch2_do_invalidates_work(struct work_struct *work)
+{
+       struct bch_fs *c = container_of(work, struct bch_fs, invalidate_work);
+       struct bch_dev *ca;
+       struct btree_trans trans;
+       struct bpos bucket;
+       unsigned i, sectors;
+       int ret = 0;
 
-       spin_unlock(&c->freelist_lock);
+       bch2_trans_init(&trans, c, 0, 0);
 
-       bucket_io_clock_reset(c, ca, bucket, READ);
-       bucket_io_clock_reset(c, ca, bucket, WRITE);
+       for_each_member_device(ca, c, i) {
+               s64 nr_to_invalidate =
+                       should_invalidate_buckets(ca, bch2_dev_usage_read(ca));
+
+               while (nr_to_invalidate-- >= 0) {
+                       ret = commit_do(&trans, NULL, NULL,
+                                             BTREE_INSERT_USE_RESERVE|
+                                             BTREE_INSERT_NOFAIL,
+                                       invalidate_one_bucket(&trans, ca, &bucket,
+                                                             &sectors));
+                       if (ret)
+                               break;
 
-       percpu_up_read_preempt_enable(&c->usage_lock);
+                       trace_invalidate_bucket(c, bucket.inode, bucket.offset, sectors);
+                       this_cpu_inc(c->counters[BCH_COUNTER_bucket_invalidate]);
+               }
+       }
 
-       if (m.journal_seq_valid) {
-               u64 journal_seq = atomic64_read(&c->journal.seq);
-               u64 bucket_seq  = journal_seq;
+       bch2_trans_exit(&trans);
+       percpu_ref_put(&c->writes);
+}
 
-               bucket_seq &= ~((u64) U16_MAX);
-               bucket_seq |= m.journal_seq;
+void bch2_do_invalidates(struct bch_fs *c)
+{
+       if (percpu_ref_tryget_live(&c->writes) &&
+           !queue_work(system_long_wq, &c->invalidate_work))
+               percpu_ref_put(&c->writes);
+}
 
-               if (bucket_seq > journal_seq)
-                       bucket_seq -= 1 << 16;
+static int bucket_freespace_init(struct btree_trans *trans, struct btree_iter *iter)
+{
+       struct bch_alloc_v4 a;
+       struct bkey_s_c k;
+       int ret;
 
-               *flush_seq = max(*flush_seq, bucket_seq);
-       }
+       k = bch2_btree_iter_peek_slot(iter);
+       ret = bkey_err(k);
+       if (ret)
+               return ret;
 
-       return m.cached_sectors != 0;
+       bch2_alloc_to_v4(k, &a);
+       return bch2_bucket_do_index(trans, k, &a, true);
 }
 
-/*
- * Pull buckets off ca->alloc_heap, invalidate them, move them to ca->free_inc:
- */
-static int bch2_invalidate_buckets(struct bch_fs *c, struct bch_dev *ca)
+static int bch2_dev_freespace_init(struct bch_fs *c, struct bch_dev *ca)
 {
+       struct btree_trans trans;
        struct btree_iter iter;
-       u64 journal_seq = 0;
-       int ret = 0;
-       long b;
+       struct bkey_s_c k;
+       struct bch_member *m;
+       int ret;
 
-       bch2_btree_iter_init(&iter, c, BTREE_ID_ALLOC, POS(ca->dev_idx, 0),
-                            BTREE_ITER_SLOTS|BTREE_ITER_INTENT);
+       bch2_trans_init(&trans, c, 0, 0);
 
-       /* Only use nowait if we've already invalidated at least one bucket: */
-       while (!ret &&
-              !fifo_full(&ca->free_inc) &&
-              (b = next_alloc_bucket(ca)) >= 0) {
-               bool must_flush =
-                       bch2_invalidate_one_bucket(c, ca, b, &journal_seq);
+       for_each_btree_key(&trans, iter, BTREE_ID_alloc,
+                          POS(ca->dev_idx, ca->mi.first_bucket),
+                          BTREE_ITER_SLOTS|
+                          BTREE_ITER_PREFETCH, k, ret) {
+               if (iter.pos.offset >= ca->mi.nbuckets)
+                       break;
 
-               ret = __bch2_alloc_write_key(c, ca, b, &iter,
-                               must_flush ? &journal_seq : NULL,
-                               !fifo_empty(&ca->free_inc) ? BTREE_INSERT_NOWAIT : 0);
+               ret = commit_do(&trans, NULL, NULL,
+                                     BTREE_INSERT_LAZY_RW,
+                                bucket_freespace_init(&trans, &iter));
+               if (ret)
+                       break;
        }
+       bch2_trans_iter_exit(&trans, &iter);
 
-       bch2_btree_iter_unlock(&iter);
+       bch2_trans_exit(&trans);
 
-       /* If we used NOWAIT, don't return the error: */
-       if (!fifo_empty(&ca->free_inc))
-               ret = 0;
        if (ret) {
-               bch_err(ca, "error invalidating buckets: %i", ret);
+               bch_err(ca, "error initializing free space: %i", ret);
                return ret;
        }
 
-       if (journal_seq)
-               ret = bch2_journal_flush_seq(&c->journal, journal_seq);
-       if (ret) {
-               bch_err(ca, "journal error: %i", ret);
-               return ret;
-       }
+       mutex_lock(&c->sb_lock);
+       m = bch2_sb_get_members(c->disk_sb.sb)->members + ca->dev_idx;
+       SET_BCH_MEMBER_FREESPACE_INITIALIZED(m, true);
+       mutex_unlock(&c->sb_lock);
 
-       return 0;
+       return ret;
 }
 
-static int push_invalidated_bucket(struct bch_fs *c, struct bch_dev *ca, size_t bucket)
+int bch2_fs_freespace_init(struct bch_fs *c)
 {
+       struct bch_dev *ca;
        unsigned i;
        int ret = 0;
+       bool doing_init = false;
 
-       while (1) {
-               set_current_state(TASK_INTERRUPTIBLE);
+       /*
+        * We can crash during the device add path, so we need to check this on
+        * every mount:
+        */
 
-               spin_lock(&c->freelist_lock);
-               for (i = 0; i < RESERVE_NR; i++)
-                       if (fifo_push(&ca->free[i], bucket)) {
-                               fifo_pop(&ca->free_inc, bucket);
-                               closure_wake_up(&c->freelist_wait);
-                               spin_unlock(&c->freelist_lock);
-                               goto out;
-                       }
-               spin_unlock(&c->freelist_lock);
+       for_each_member_device(ca, c, i) {
+               if (ca->mi.freespace_initialized)
+                       continue;
 
-               if ((current->flags & PF_KTHREAD) &&
-                   kthread_should_stop()) {
-                       ret = 1;
-                       break;
+               if (!doing_init) {
+                       bch_info(c, "initializing freespace");
+                       doing_init = true;
                }
 
-               schedule();
-               try_to_freeze();
+               ret = bch2_dev_freespace_init(c, ca);
+               if (ret) {
+                       percpu_ref_put(&ca->ref);
+                       return ret;
+               }
        }
-out:
-       __set_current_state(TASK_RUNNING);
-       return ret;
-}
-
-/*
- * Pulls buckets off free_inc, discards them (if enabled), then adds them to
- * freelists, waiting until there's room if necessary:
- */
-static int discard_invalidated_buckets(struct bch_fs *c, struct bch_dev *ca)
-{
-       while (!fifo_empty(&ca->free_inc)) {
-               size_t bucket = fifo_peek(&ca->free_inc);
 
-               if (ca->mi.discard &&
-                   blk_queue_discard(bdev_get_queue(ca->disk_sb.bdev)))
-                       blkdev_issue_discard(ca->disk_sb.bdev,
-                                            bucket_to_sector(ca, bucket),
-                                            ca->mi.bucket_size, GFP_NOIO, 0);
+       if (doing_init) {
+               mutex_lock(&c->sb_lock);
+               bch2_write_super(c);
+               mutex_unlock(&c->sb_lock);
 
-               if (push_invalidated_bucket(c, ca, bucket))
-                       return 1;
+               bch_verbose(c, "done initializing freespace");
        }
 
-       return 0;
+       return ret;
 }
 
-/**
- * bch_allocator_thread - move buckets from free_inc to reserves
- *
- * The free_inc FIFO is populated by find_reclaimable_buckets(), and
- * the reserves are depleted by bucket allocation. When we run out
- * of free_inc, try to invalidate some buckets and write out
- * prios and gens.
- */
-static int bch2_allocator_thread(void *arg)
-{
-       struct bch_dev *ca = arg;
-       struct bch_fs *c = ca->fs;
-       size_t nr;
-       int ret;
-
-       set_freezable();
-
-       while (1) {
-               cond_resched();
-
-               pr_debug("discarding %zu invalidated buckets",
-                        fifo_used(&ca->free_inc));
-
-               ret = discard_invalidated_buckets(c, ca);
-               if (ret)
-                       goto stop;
-
-               down_read(&c->gc_lock);
-
-               ret = bch2_invalidate_buckets(c, ca);
-               if (ret) {
-                       up_read(&c->gc_lock);
-                       goto stop;
-               }
-
-               if (!fifo_empty(&ca->free_inc)) {
-                       up_read(&c->gc_lock);
-                       continue;
-               }
-
-               pr_debug("free_inc now empty");
-
-               do {
-                       /*
-                        * Find some buckets that we can invalidate, either
-                        * they're completely unused, or only contain clean data
-                        * that's been written back to the backing device or
-                        * another cache tier
-                        */
-
-                       pr_debug("scanning for reclaimable buckets");
-
-                       nr = find_reclaimable_buckets(c, ca);
-
-                       pr_debug("found %zu buckets", nr);
-
-                       trace_alloc_batch(ca, nr, ca->alloc_heap.size);
-
-                       if ((ca->inc_gen_needs_gc >= ALLOC_SCAN_BATCH(ca) ||
-                            ca->inc_gen_really_needs_gc) &&
-                           c->gc_thread) {
-                               atomic_inc(&c->kick_gc);
-                               wake_up_process(c->gc_thread);
-                       }
+/* Bucket IO clocks: */
 
-                       /*
-                        * If we found any buckets, we have to invalidate them
-                        * before we scan for more - but if we didn't find very
-                        * many we may want to wait on more buckets being
-                        * available so we don't spin:
-                        */
-                       if (!nr ||
-                           (nr < ALLOC_SCAN_BATCH(ca) &&
-                            !fifo_full(&ca->free[RESERVE_MOVINGGC]))) {
-                               ca->allocator_blocked = true;
-                               closure_wake_up(&c->freelist_wait);
-
-                               ret = wait_buckets_available(c, ca);
-                               if (ret) {
-                                       up_read(&c->gc_lock);
-                                       goto stop;
-                               }
-                       }
-               } while (!nr);
+int bch2_bucket_io_time_reset(struct btree_trans *trans, unsigned dev,
+                             size_t bucket_nr, int rw)
+{
+       struct bch_fs *c = trans->c;
+       struct btree_iter iter;
+       struct bkey_i_alloc_v4 *a;
+       u64 now;
+       int ret = 0;
 
-               ca->allocator_blocked = false;
-               up_read(&c->gc_lock);
+       a = bch2_trans_start_alloc_update(trans, &iter,  POS(dev, bucket_nr));
+       ret = PTR_ERR_OR_ZERO(a);
+       if (ret)
+               return ret;
 
-               pr_debug("%zu buckets to invalidate", nr);
+       now = atomic64_read(&c->io_clock[rw].now);
+       if (a->v.io_time[rw] == now)
+               goto out;
 
-               /*
-                * alloc_heap is now full of newly-invalidated buckets: next,
-                * write out the new bucket gens:
-                */
-       }
+       a->v.io_time[rw] = now;
 
-stop:
-       pr_debug("alloc thread stopping (ret %i)", ret);
-       return 0;
+       ret   = bch2_trans_update(trans, &iter, &a->k_i, 0) ?:
+               bch2_trans_commit(trans, NULL, NULL, 0);
+out:
+       bch2_trans_iter_exit(trans, &iter);
+       return ret;
 }
 
 /* Startup/shutdown (ro/rw): */
@@ -996,12 +1426,12 @@ void bch2_recalc_capacity(struct bch_fs *c)
        u64 capacity = 0, reserved_sectors = 0, gc_reserve;
        unsigned bucket_size_max = 0;
        unsigned long ra_pages = 0;
-       unsigned i, j;
+       unsigned i;
 
        lockdep_assert_held(&c->state_lock);
 
        for_each_online_member(ca, c, i) {
-               struct backing_dev_info *bdi = ca->disk_sb.bdev->bd_bdi;
+               struct backing_dev_info *bdi = ca->disk_sb.bdev->bd_disk->bdi;
 
                ra_pages += bdi->ra_pages;
        }
@@ -1027,8 +1457,9 @@ void bch2_recalc_capacity(struct bch_fs *c)
                 * allocations for foreground writes must wait -
                 * not -ENOSPC calculations.
                 */
-               for (j = 0; j < RESERVE_NONE; j++)
-                       dev_reserve += ca->free[j].size;
+
+               dev_reserve += ca->nr_btree_reserve * 2;
+               dev_reserve += ca->mi.nbuckets >> 6; /* copygc reserve */
 
                dev_reserve += 1;       /* btree write point */
                dev_reserve += 1;       /* copygc write point */
@@ -1036,8 +1467,6 @@ void bch2_recalc_capacity(struct bch_fs *c)
 
                dev_reserve *= ca->mi.bucket_size;
 
-               ca->copygc_threshold = dev_reserve;
-
                capacity += bucket_to_sector(ca, ca->mi.nbuckets -
                                             ca->mi.first_bucket);
 
@@ -1059,18 +1488,6 @@ void bch2_recalc_capacity(struct bch_fs *c)
 
        c->bucket_size_max = bucket_size_max;
 
-       if (c->capacity) {
-               bch2_io_timer_add(&c->io_clock[READ],
-                                &c->bucket_clock[READ].rescale);
-               bch2_io_timer_add(&c->io_clock[WRITE],
-                                &c->bucket_clock[WRITE].rescale);
-       } else {
-               bch2_io_timer_del(&c->io_clock[READ],
-                                &c->bucket_clock[READ].rescale);
-               bch2_io_timer_del(&c->io_clock[WRITE],
-                                &c->bucket_clock[WRITE].rescale);
-       }
-
        /* Wake up case someone was waiting for buckets */
        closure_wake_up(&c->freelist_wait);
 }
@@ -1085,7 +1502,7 @@ static bool bch2_dev_has_open_write_point(struct bch_fs *c, struct bch_dev *ca)
             ob++) {
                spin_lock(&ob->lock);
                if (ob->valid && !ob->on_partial_list &&
-                   ob->ptr.dev == ca->dev_idx)
+                   ob->dev == ca->dev_idx)
                        ret = true;
                spin_unlock(&ob->lock);
        }
@@ -1098,8 +1515,6 @@ void bch2_dev_allocator_remove(struct bch_fs *c, struct bch_dev *ca)
 {
        unsigned i;
 
-       BUG_ON(ca->alloc_thread);
-
        /* First, remove device from allocation groups: */
 
        for (i = 0; i < ARRAY_SIZE(c->rw_devs); i++)
@@ -1114,7 +1529,7 @@ void bch2_dev_allocator_remove(struct bch_fs *c, struct bch_dev *ca)
        for (i = 0; i < ARRAY_SIZE(c->write_points); i++)
                bch2_writepoint_stop(c, ca, &c->write_points[i]);
 
-       bch2_writepoint_stop(c, ca, &ca->copygc_write_point);
+       bch2_writepoint_stop(c, ca, &c->copygc_write_point);
        bch2_writepoint_stop(c, ca, &c->rebalance_write_point);
        bch2_writepoint_stop(c, ca, &c->btree_write_point);
 
@@ -1173,259 +1588,9 @@ void bch2_dev_allocator_add(struct bch_fs *c, struct bch_dev *ca)
                        set_bit(ca->dev_idx, c->rw_devs[i].d);
 }
 
-/* stop allocator thread: */
-void bch2_dev_allocator_stop(struct bch_dev *ca)
-{
-       struct task_struct *p;
-
-       p = rcu_dereference_protected(ca->alloc_thread, 1);
-       ca->alloc_thread = NULL;
-
-       /*
-        * We need an rcu barrier between setting ca->alloc_thread = NULL and
-        * the thread shutting down to avoid bch2_wake_allocator() racing:
-        *
-        * XXX: it would be better to have the rcu barrier be asynchronous
-        * instead of blocking us here
-        */
-       synchronize_rcu();
-
-       if (p) {
-               kthread_stop(p);
-               put_task_struct(p);
-       }
-}
-
-/* start allocator thread: */
-int bch2_dev_allocator_start(struct bch_dev *ca)
-{
-       struct task_struct *p;
-
-       /*
-        * allocator thread already started?
-        */
-       if (ca->alloc_thread)
-               return 0;
-
-       p = kthread_create(bch2_allocator_thread, ca,
-                          "bch_alloc[%s]", ca->name);
-       if (IS_ERR(p))
-               return PTR_ERR(p);
-
-       get_task_struct(p);
-       rcu_assign_pointer(ca->alloc_thread, p);
-       wake_up_process(p);
-       return 0;
-}
-
-static void flush_held_btree_writes(struct bch_fs *c)
-{
-       struct bucket_table *tbl;
-       struct rhash_head *pos;
-       struct btree *b;
-       bool flush_updates;
-       size_t i, nr_pending_updates;
-
-       clear_bit(BCH_FS_HOLD_BTREE_WRITES, &c->flags);
-again:
-       pr_debug("flushing dirty btree nodes");
-       cond_resched();
-
-       flush_updates = false;
-       nr_pending_updates = bch2_btree_interior_updates_nr_pending(c);
-
-       rcu_read_lock();
-       for_each_cached_btree(b, c, tbl, i, pos)
-               if (btree_node_dirty(b) && (!b->written || b->level)) {
-                       if (btree_node_may_write(b)) {
-                               rcu_read_unlock();
-                               btree_node_lock_type(c, b, SIX_LOCK_read);
-                               bch2_btree_node_write(c, b, SIX_LOCK_read);
-                               six_unlock_read(&b->lock);
-                               goto again;
-                       } else {
-                               flush_updates = true;
-                       }
-               }
-       rcu_read_unlock();
-
-       if (c->btree_roots_dirty)
-               bch2_journal_meta(&c->journal);
-
-       /*
-        * This is ugly, but it's needed to flush btree node writes
-        * without spinning...
-        */
-       if (flush_updates) {
-               closure_wait_event(&c->btree_interior_update_wait,
-                                  bch2_btree_interior_updates_nr_pending(c) <
-                                  nr_pending_updates);
-               goto again;
-       }
-
-}
-
-static void allocator_start_issue_discards(struct bch_fs *c)
-{
-       struct bch_dev *ca;
-       unsigned dev_iter;
-       size_t bu;
-
-       for_each_rw_member(ca, c, dev_iter)
-               while (fifo_pop(&ca->free_inc, bu))
-                       blkdev_issue_discard(ca->disk_sb.bdev,
-                                            bucket_to_sector(ca, bu),
-                                            ca->mi.bucket_size, GFP_NOIO, 0);
-}
-
-static int __bch2_fs_allocator_start(struct bch_fs *c)
-{
-       struct bch_dev *ca;
-       unsigned dev_iter;
-       u64 journal_seq = 0;
-       long bu;
-       bool invalidating_data = false;
-       int ret = 0;
-
-       if (test_alloc_startup(c)) {
-               invalidating_data = true;
-               goto not_enough;
-       }
-
-       /* Scan for buckets that are already invalidated: */
-       for_each_rw_member(ca, c, dev_iter) {
-               struct bucket_array *buckets;
-               struct bucket_mark m;
-
-               down_read(&ca->bucket_lock);
-               percpu_down_read_preempt_disable(&c->usage_lock);
-
-               buckets = bucket_array(ca);
-
-               for (bu = buckets->first_bucket;
-                    bu < buckets->nbuckets; bu++) {
-                       m = READ_ONCE(buckets->b[bu].mark);
-
-                       if (!m.gen_valid ||
-                           !is_available_bucket(m) ||
-                           m.cached_sectors)
-                               continue;
-
-                       bch2_mark_alloc_bucket(c, ca, bu, true,
-                                       gc_pos_alloc(c, NULL), 0);
-
-                       fifo_push(&ca->free_inc, bu);
-
-                       discard_invalidated_buckets(c, ca);
-
-                       if (fifo_full(&ca->free[RESERVE_BTREE]))
-                               break;
-               }
-               percpu_up_read_preempt_enable(&c->usage_lock);
-               up_read(&ca->bucket_lock);
-       }
-
-       /* did we find enough buckets? */
-       for_each_rw_member(ca, c, dev_iter)
-               if (!fifo_full(&ca->free[RESERVE_BTREE])) {
-                       percpu_ref_put(&ca->io_ref);
-                       goto not_enough;
-               }
-
-       return 0;
-not_enough:
-       pr_debug("not enough empty buckets; scanning for reclaimable buckets");
-
-       for_each_rw_member(ca, c, dev_iter) {
-               find_reclaimable_buckets(c, ca);
-
-               while (!fifo_full(&ca->free[RESERVE_BTREE]) &&
-                      (bu = next_alloc_bucket(ca)) >= 0) {
-                       invalidating_data |=
-                               bch2_invalidate_one_bucket(c, ca, bu, &journal_seq);
-
-                       fifo_push(&ca->free[RESERVE_BTREE], bu);
-                       set_bit(bu, ca->buckets_dirty);
-               }
-       }
-
-       pr_debug("done scanning for reclaimable buckets");
-
-       /*
-        * We're moving buckets to freelists _before_ they've been marked as
-        * invalidated on disk - we have to so that we can allocate new btree
-        * nodes to mark them as invalidated on disk.
-        *
-        * However, we can't _write_ to any of these buckets yet - they might
-        * have cached data in them, which is live until they're marked as
-        * invalidated on disk:
-        */
-       if (invalidating_data) {
-               pr_debug("invalidating existing data");
-               set_bit(BCH_FS_HOLD_BTREE_WRITES, &c->flags);
-       } else {
-               pr_debug("issuing discards");
-               allocator_start_issue_discards(c);
-       }
-
-       /*
-        * XXX: it's possible for this to deadlock waiting on journal reclaim,
-        * since we're holding btree writes. What then?
-        */
-       ret = bch2_alloc_write(c);
-       if (ret)
-               return ret;
-
-       if (invalidating_data) {
-               pr_debug("flushing journal");
-
-               ret = bch2_journal_flush_seq(&c->journal, journal_seq);
-               if (ret)
-                       return ret;
-
-               pr_debug("issuing discards");
-               allocator_start_issue_discards(c);
-       }
-
-       set_bit(BCH_FS_ALLOCATOR_STARTED, &c->flags);
-
-       /* now flush dirty btree nodes: */
-       if (invalidating_data)
-               flush_held_btree_writes(c);
-
-       return 0;
-}
-
-int bch2_fs_allocator_start(struct bch_fs *c)
-{
-       struct bch_dev *ca;
-       unsigned i;
-       int ret;
-
-       down_read(&c->gc_lock);
-       ret = __bch2_fs_allocator_start(c);
-       up_read(&c->gc_lock);
-
-       if (ret)
-               return ret;
-
-       for_each_rw_member(ca, c, i) {
-               ret = bch2_dev_allocator_start(ca);
-               if (ret) {
-                       percpu_ref_put(&ca->io_ref);
-                       return ret;
-               }
-       }
-
-       return bch2_alloc_write(c);
-}
-
 void bch2_fs_allocator_background_init(struct bch_fs *c)
 {
        spin_lock_init(&c->freelist_lock);
-       bch2_bucket_clock_init(c, READ);
-       bch2_bucket_clock_init(c, WRITE);
-
-       c->pd_controllers_update_seconds = 5;
-       INIT_DELAYED_WORK(&c->pd_controllers_update, pd_controllers_update);
+       INIT_WORK(&c->discard_work, bch2_do_discards_work);
+       INIT_WORK(&c->invalidate_work, bch2_do_invalidates_work);
 }