]> git.sesse.net Git - bcachefs-tools-debian/blobdiff - libbcachefs/alloc_background.c
Update bcachefs sources to 9a555a741e80 bcachefs: omit alignment attribute on big...
[bcachefs-tools-debian] / libbcachefs / alloc_background.c
index d9bc2d0f844aa589682d9abf70ae5dec07a6cb84..c7be6afe89553b154ff8ba1d2899908026c5451a 100644 (file)
@@ -9,6 +9,7 @@
 #include "btree_update.h"
 #include "btree_update_interior.h"
 #include "btree_gc.h"
+#include "btree_write_buffer.h"
 #include "buckets.h"
 #include "buckets_waiting_for_journal.h"
 #include "clock.h"
@@ -17,6 +18,7 @@
 #include "error.h"
 #include "lru.h"
 #include "recovery.h"
+#include "trace.h"
 #include "varint.h"
 
 #include <linux/kthread.h>
@@ -26,7 +28,6 @@
 #include <linux/rcupdate.h>
 #include <linux/sched/task.h>
 #include <linux/sort.h>
-#include <trace/events/bcachefs.h>
 
 /* Persistent alloc info: */
 
@@ -78,36 +79,6 @@ static inline u64 alloc_field_v1_get(const struct bch_alloc *a,
        return 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:
-               *((u8 *) *p) = v;
-               break;
-       case 2:
-               *((__le16 *) *p) = cpu_to_le16(v);
-               break;
-       case 4:
-               *((__le32 *) *p) = cpu_to_le32(v);
-               break;
-       case 8:
-               *((__le64 *) *p) = cpu_to_le64(v);
-               break;
-       default:
-               BUG();
-       }
-
-       *p += bytes;
-}
-
 static void bch2_alloc_unpack_v1(struct bkey_alloc_unpacked *out,
                                 struct bkey_s_c k)
 {
@@ -221,143 +192,106 @@ static unsigned bch_alloc_v1_val_u64s(const struct bch_alloc *a)
        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)
+int bch2_alloc_v1_invalid(struct bch_fs *c, struct bkey_s_c k,
+                         enum bkey_invalid_flags flags,
+                         struct printbuf *err)
 {
        struct bkey_s_c_alloc a = bkey_s_c_to_alloc(k);
+       int ret = 0;
 
        /* 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 -BCH_ERR_invalid_bkey;
-       }
-
-       return 0;
+       bkey_fsck_err_on(bkey_val_u64s(a.k) < bch_alloc_v1_val_u64s(a.v), c, err,
+                        alloc_v1_val_size_bad,
+                        "incorrect value size (%zu < %u)",
+                        bkey_val_u64s(a.k), bch_alloc_v1_val_u64s(a.v));
+fsck_err:
+       return ret;
 }
 
-int bch2_alloc_v2_invalid(const struct bch_fs *c, struct bkey_s_c k,
-                         int rw, struct printbuf *err)
+int bch2_alloc_v2_invalid(struct bch_fs *c, struct bkey_s_c k,
+                         enum bkey_invalid_flags flags,
+                         struct printbuf *err)
 {
        struct bkey_alloc_unpacked u;
+       int ret = 0;
 
-       if (bch2_alloc_unpack_v2(&u, k)) {
-               prt_printf(err, "unpack error");
-               return -BCH_ERR_invalid_bkey;
-       }
-
-       return 0;
+       bkey_fsck_err_on(bch2_alloc_unpack_v2(&u, k), c, err,
+                        alloc_v2_unpack_error,
+                        "unpack error");
+fsck_err:
+       return ret;
 }
 
-int bch2_alloc_v3_invalid(const struct bch_fs *c, struct bkey_s_c k,
-                         int rw, struct printbuf *err)
+int bch2_alloc_v3_invalid(struct bch_fs *c, struct bkey_s_c k,
+                         enum bkey_invalid_flags flags,
+                         struct printbuf *err)
 {
        struct bkey_alloc_unpacked u;
+       int ret = 0;
 
-       if (bch2_alloc_unpack_v3(&u, k)) {
-               prt_printf(err, "unpack error");
-               return -BCH_ERR_invalid_bkey;
-       }
-
-       return 0;
+       bkey_fsck_err_on(bch2_alloc_unpack_v3(&u, k), c, err,
+                        alloc_v2_unpack_error,
+                        "unpack error");
+fsck_err:
+       return ret;
 }
 
-int bch2_alloc_v4_invalid(const struct bch_fs *c, struct bkey_s_c k,
-                         int rw, struct printbuf *err)
+int bch2_alloc_v4_invalid(struct bch_fs *c, struct bkey_s_c k,
+                         enum bkey_invalid_flags flags, struct printbuf *err)
 {
        struct bkey_s_c_alloc_v4 a = bkey_s_c_to_alloc_v4(k);
+       int ret = 0;
 
-       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 -BCH_ERR_invalid_bkey;
-       }
-
-       if (!BCH_ALLOC_V4_BACKPOINTERS_START(a.v) &&
-           BCH_ALLOC_V4_NR_BACKPOINTERS(a.v)) {
-               prt_printf(err, "invalid backpointers_start");
-               return -BCH_ERR_invalid_bkey;
-       }
-
-       /*
-        * XXX this is wrong, we'll be checking updates that happened from
-        * before BCH_FS_CHECK_BACKPOINTERS_DONE
-        */
-       if (rw == WRITE && test_bit(BCH_FS_CHECK_BACKPOINTERS_DONE, &c->flags)) {
-               unsigned i, bp_len = 0;
-
-               for (i = 0; i < BCH_ALLOC_V4_NR_BACKPOINTERS(a.v); i++)
-                       bp_len += alloc_v4_backpointers_c(a.v)[i].bucket_len;
+       bkey_fsck_err_on(alloc_v4_u64s(a.v) > bkey_val_u64s(k.k), c, err,
+                        alloc_v4_val_size_bad,
+                        "bad val size (%u > %zu)",
+                        alloc_v4_u64s(a.v), bkey_val_u64s(k.k));
 
-               if (bp_len > a.v->dirty_sectors) {
-                       prt_printf(err, "too many backpointers");
-                       return -BCH_ERR_invalid_bkey;
-               }
-       }
-
-       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 -BCH_ERR_invalid_bkey;
-               }
+       bkey_fsck_err_on(!BCH_ALLOC_V4_BACKPOINTERS_START(a.v) &&
+                        BCH_ALLOC_V4_NR_BACKPOINTERS(a.v), c, err,
+                        alloc_v4_backpointers_start_bad,
+                        "invalid backpointers_start");
 
-               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 -BCH_ERR_invalid_bkey;
-                       }
-                       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 -BCH_ERR_invalid_bkey;
-                       }
-                       break;
-               case BCH_DATA_cached:
-                       if (!a.v->cached_sectors ||
-                           a.v->dirty_sectors ||
-                           a.v->stripe) {
-                               prt_printf(err, "data type inconsistency");
-                               return -BCH_ERR_invalid_bkey;
-                       }
+       bkey_fsck_err_on(alloc_data_type(*a.v, a.v->data_type) != a.v->data_type, c, err,
+                        alloc_key_data_type_bad,
+                        "invalid data type (got %u should be %u)",
+                        a.v->data_type, alloc_data_type(*a.v, a.v->data_type));
 
-                       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 -BCH_ERR_invalid_bkey;
-                       }
-                       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 -BCH_ERR_invalid_bkey;
-                       }
-                       break;
-               }
+       switch (a.v->data_type) {
+       case BCH_DATA_free:
+       case BCH_DATA_need_gc_gens:
+       case BCH_DATA_need_discard:
+               bkey_fsck_err_on(bch2_bucket_sectors(*a.v) || a.v->stripe,
+                                c, err, alloc_key_empty_but_have_data,
+                                "empty data type free but have data");
+               break;
+       case BCH_DATA_sb:
+       case BCH_DATA_journal:
+       case BCH_DATA_btree:
+       case BCH_DATA_user:
+       case BCH_DATA_parity:
+               bkey_fsck_err_on(!bch2_bucket_sectors_dirty(*a.v),
+                                c, err, alloc_key_dirty_sectors_0,
+                                "data_type %s but dirty_sectors==0",
+                                bch2_data_type_str(a.v->data_type));
+               break;
+       case BCH_DATA_cached:
+               bkey_fsck_err_on(!a.v->cached_sectors ||
+                                bch2_bucket_sectors_dirty(*a.v) ||
+                                a.v->stripe,
+                                c, err, alloc_key_cached_inconsistency,
+                                "data type inconsistency");
+
+               bkey_fsck_err_on(!a.v->io_time[READ] &&
+                                c->curr_recovery_pass > BCH_RECOVERY_PASS_check_alloc_to_lru_refs,
+                                c, err, alloc_key_cached_but_read_time_zero,
+                                "cached bucket with read_time == 0");
+               break;
+       case BCH_DATA_stripe:
+               break;
        }
-
-       return 0;
-}
-
-static inline u64 swab40(u64 x)
-{
-       return (((x & 0x00000000ffULL) << 32)|
-               ((x & 0x000000ff00ULL) << 16)|
-               ((x & 0x0000ff0000ULL) >>  0)|
-               ((x & 0x00ff000000ULL) >> 16)|
-               ((x & 0xff00000000ULL) >> 32));
+fsck_err:
+       return ret;
 }
 
 void bch2_alloc_v4_swab(struct bkey_s k)
@@ -373,6 +307,7 @@ void bch2_alloc_v4_swab(struct bkey_s k)
        a->io_time[1]           = swab64(a->io_time[1]);
        a->stripe               = swab32(a->stripe);
        a->nr_external_backpointers = swab32(a->nr_external_backpointers);
+       a->fragmentation_lru    = swab64(a->fragmentation_lru);
 
        bps = alloc_v4_backpointers(a);
        for (bp = bps; bp < bps + BCH_ALLOC_V4_NR_BACKPOINTERS(a); bp++) {
@@ -386,14 +321,12 @@ void bch2_alloc_to_text(struct printbuf *out, struct bch_fs *c, struct bkey_s_c
 {
        struct bch_alloc_v4 _a;
        const struct bch_alloc_v4 *a = bch2_alloc_to_v4(k, &_a);
-       const struct bch_backpointer *bps;
-       unsigned i;
 
        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_printf(out, "gen %u oldest_gen %u data_type ", a->gen, a->oldest_gen);
+       bch2_prt_data_type(out, a->data_type);
        prt_newline(out);
        prt_printf(out, "journal_seq       %llu",       a->journal_seq);
        prt_newline(out);
@@ -413,33 +346,27 @@ void bch2_alloc_to_text(struct printbuf *out, struct bch_fs *c, struct bkey_s_c
        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]);
-       }
-
-       printbuf_indent_sub(out, 4);
+       prt_printf(out, "fragmentation     %llu",       a->fragmentation_lru);
+       prt_newline(out);
+       prt_printf(out, "bp_start          %llu", BCH_ALLOC_V4_BACKPOINTERS_START(a));
+       printbuf_indent_sub(out, 2);
 }
 
 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;
+               void *src, *dst;
 
                *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);
-               }
+               src = alloc_v4_backpointers(out);
+               SET_BCH_ALLOC_V4_BACKPOINTERS_START(out, BCH_ALLOC_V4_U64s);
+               dst = alloc_v4_backpointers(out);
+
+               if (src < dst)
+                       memset(src, 0, dst - src);
+
+               SET_BCH_ALLOC_V4_NR_BACKPOINTERS(out, 0);
        } else {
                struct bkey_alloc_unpacked u = bch2_alloc_unpack(k);
 
@@ -465,20 +392,13 @@ static noinline struct bkey_i_alloc_v4 *
 __bch2_alloc_to_v4_mut(struct btree_trans *trans, struct bkey_s_c k)
 {
        struct bkey_i_alloc_v4 *ret;
-       unsigned bytes = k.k->type == KEY_TYPE_alloc_v4
-               ? bkey_bytes(k.k)
-               : sizeof(struct bkey_i_alloc_v4);
 
-       /*
-        * 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));
+       ret = bch2_trans_kmalloc(trans, max(bkey_bytes(k.k), sizeof(struct bkey_i_alloc_v4)));
        if (IS_ERR(ret))
                return ret;
 
        if (k.k->type == KEY_TYPE_alloc_v4) {
-               struct bch_backpointer *src, *dst;
+               void *src, *dst;
 
                bkey_reassemble(&ret->k_i, k);
 
@@ -486,9 +406,10 @@ __bch2_alloc_to_v4_mut(struct btree_trans *trans, struct bkey_s_c k)
                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);
+               if (src < dst)
+                       memset(src, 0, dst - src);
+
+               SET_BCH_ALLOC_V4_NR_BACKPOINTERS(&ret->v, 0);
                set_alloc_v4_u64s(ret);
        } else {
                bkey_alloc_v4_init(&ret->k_i);
@@ -500,20 +421,12 @@ __bch2_alloc_to_v4_mut(struct btree_trans *trans, struct bkey_s_c k)
 
 static inline struct bkey_i_alloc_v4 *bch2_alloc_to_v4_mut_inlined(struct btree_trans *trans, struct bkey_s_c k)
 {
+       struct bkey_s_c_alloc_v4 a;
+
        if (likely(k.k->type == KEY_TYPE_alloc_v4) &&
-           BCH_ALLOC_V4_BACKPOINTERS_START(bkey_s_c_to_alloc_v4(k).v) == BCH_ALLOC_V4_U64s) {
-               /*
-                * Reserve space for one more backpointer here:
-                * Not sketchy at doing it this way, nope...
-                */
-               struct bkey_i_alloc_v4 *ret =
-                       bch2_trans_kmalloc_nomemzero(trans, bkey_bytes(k.k) + sizeof(struct bch_backpointer));
-               if (!IS_ERR(ret)) {
-                       bkey_reassemble(&ret->k_i, k);
-                       memset((void *) ret + bkey_bytes(k.k), 0, sizeof(struct bch_backpointer));
-               }
-               return ret;
-       }
+           ((a = bkey_s_c_to_alloc_v4(k), true) &&
+            BCH_ALLOC_V4_NR_BACKPOINTERS(a.v) == 0))
+               return bch2_bkey_make_mut_noupdate_typed(trans, k, alloc_v4);
 
        return __bch2_alloc_to_v4_mut(trans, k);
 }
@@ -531,14 +444,13 @@ bch2_trans_start_alloc_update(struct btree_trans *trans, struct btree_iter *iter
        struct bkey_i_alloc_v4 *a;
        int ret;
 
-       bch2_trans_iter_init(trans, iter, BTREE_ID_alloc, pos,
+       k = bch2_bkey_get_iter(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 (unlikely(ret))
-               goto err;
+               return ERR_PTR(ret);
 
        a = bch2_alloc_to_v4_mut_inlined(trans, k);
        ret = PTR_ERR_OR_ZERO(a);
@@ -550,19 +462,63 @@ err:
        return ERR_PTR(ret);
 }
 
-int bch2_alloc_read(struct bch_fs *c)
+static struct bpos alloc_gens_pos(struct bpos pos, unsigned *offset)
 {
-       struct btree_trans trans;
-       struct btree_iter iter;
-       struct bkey_s_c k;
-       struct bch_alloc_v4 a;
-       struct bch_dev *ca;
-       int ret;
+       *offset = pos.offset & KEY_TYPE_BUCKET_GENS_MASK;
 
-       bch2_trans_init(&trans, c, 0, 0);
+       pos.offset >>= KEY_TYPE_BUCKET_GENS_BITS;
+       return pos;
+}
+
+static struct bpos bucket_gens_pos_to_alloc(struct bpos pos, unsigned offset)
+{
+       pos.offset <<= KEY_TYPE_BUCKET_GENS_BITS;
+       pos.offset += offset;
+       return pos;
+}
+
+static unsigned alloc_gen(struct bkey_s_c k, unsigned offset)
+{
+       return k.k->type == KEY_TYPE_bucket_gens
+               ? bkey_s_c_to_bucket_gens(k).v->gens[offset]
+               : 0;
+}
+
+int bch2_bucket_gens_invalid(struct bch_fs *c, struct bkey_s_c k,
+                            enum bkey_invalid_flags flags,
+                            struct printbuf *err)
+{
+       int ret = 0;
+
+       bkey_fsck_err_on(bkey_val_bytes(k.k) != sizeof(struct bch_bucket_gens), c, err,
+                        bucket_gens_val_size_bad,
+                        "bad val size (%zu != %zu)",
+                        bkey_val_bytes(k.k), sizeof(struct bch_bucket_gens));
+fsck_err:
+       return ret;
+}
+
+void bch2_bucket_gens_to_text(struct printbuf *out, struct bch_fs *c, struct bkey_s_c k)
+{
+       struct bkey_s_c_bucket_gens g = bkey_s_c_to_bucket_gens(k);
+       unsigned i;
 
-       for_each_btree_key(&trans, iter, BTREE_ID_alloc, POS_MIN,
-                          BTREE_ITER_PREFETCH, k, ret) {
+       for (i = 0; i < ARRAY_SIZE(g.v->gens); i++) {
+               if (i)
+                       prt_char(out, ' ');
+               prt_printf(out, "%u", g.v->gens[i]);
+       }
+}
+
+int bch2_bucket_gens_init(struct bch_fs *c)
+{
+       struct btree_trans *trans = bch2_trans_get(c);
+       struct bkey_i_bucket_gens g;
+       bool have_bucket_gens_key = false;
+       int ret;
+
+       ret = for_each_btree_key(trans, iter, BTREE_ID_alloc, POS_MIN,
+                                BTREE_ITER_PREFETCH, k, ({
                /*
                 * Not a fsck error because this is checked/repaired by
                 * bch2_check_alloc_key() which runs later:
@@ -570,17 +526,96 @@ int bch2_alloc_read(struct bch_fs *c)
                if (!bch2_dev_bucket_exists(c, k.k->p))
                        continue;
 
-               ca = bch_dev_bkey_exists(c, k.k->p.inode);
+               struct bch_alloc_v4 a;
+               u8 gen = bch2_alloc_to_v4(k, &a)->gen;
+               unsigned offset;
+               struct bpos pos = alloc_gens_pos(iter.pos, &offset);
 
-               *bucket_gen(ca, k.k->p.offset) = bch2_alloc_to_v4(k, &a)->gen;
-       }
-       bch2_trans_iter_exit(&trans, &iter);
+               if (have_bucket_gens_key && bkey_cmp(iter.pos, pos)) {
+                       ret = commit_do(trans, NULL, NULL,
+                                       BCH_TRANS_COMMIT_no_enospc,
+                               bch2_btree_insert_trans(trans, BTREE_ID_bucket_gens, &g.k_i, 0));
+                       if (ret)
+                               break;
+                       have_bucket_gens_key = false;
+               }
 
-       bch2_trans_exit(&trans);
+               if (!have_bucket_gens_key) {
+                       bkey_bucket_gens_init(&g.k_i);
+                       g.k.p = pos;
+                       have_bucket_gens_key = true;
+               }
 
-       if (ret)
-               bch_err(c, "error reading alloc info: %s", bch2_err_str(ret));
+               g.v.gens[offset] = gen;
+               0;
+       }));
+
+       if (have_bucket_gens_key && !ret)
+               ret = commit_do(trans, NULL, NULL,
+                               BCH_TRANS_COMMIT_no_enospc,
+                       bch2_btree_insert_trans(trans, BTREE_ID_bucket_gens, &g.k_i, 0));
+
+       bch2_trans_put(trans);
+
+       bch_err_fn(c, ret);
+       return ret;
+}
+
+int bch2_alloc_read(struct bch_fs *c)
+{
+       struct btree_trans *trans = bch2_trans_get(c);
+       int ret;
+
+       down_read(&c->gc_lock);
+
+       if (c->sb.version_upgrade_complete >= bcachefs_metadata_version_bucket_gens) {
+               ret = for_each_btree_key(trans, iter, BTREE_ID_bucket_gens, POS_MIN,
+                                        BTREE_ITER_PREFETCH, k, ({
+                       u64 start = bucket_gens_pos_to_alloc(k.k->p, 0).offset;
+                       u64 end = bucket_gens_pos_to_alloc(bpos_nosnap_successor(k.k->p), 0).offset;
+
+                       if (k.k->type != KEY_TYPE_bucket_gens)
+                               continue;
+
+                       const struct bch_bucket_gens *g = bkey_s_c_to_bucket_gens(k).v;
+
+                       /*
+                        * Not a fsck error because this is checked/repaired by
+                        * bch2_check_alloc_key() which runs later:
+                        */
+                       if (!bch2_dev_exists2(c, k.k->p.inode))
+                               continue;
+
+                       struct bch_dev *ca = bch_dev_bkey_exists(c, k.k->p.inode);
 
+                       for (u64 b = max_t(u64, ca->mi.first_bucket, start);
+                            b < min_t(u64, ca->mi.nbuckets, end);
+                            b++)
+                               *bucket_gen(ca, b) = g->gens[b & KEY_TYPE_BUCKET_GENS_MASK];
+                       0;
+               }));
+       } else {
+               ret = for_each_btree_key(trans, iter, BTREE_ID_alloc, POS_MIN,
+                                        BTREE_ITER_PREFETCH, k, ({
+                       /*
+                        * 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;
+
+                       struct bch_dev *ca = bch_dev_bkey_exists(c, k.k->p.inode);
+
+                       struct bch_alloc_v4 a;
+                       *bucket_gen(ca, k.k->p.offset) = bch2_alloc_to_v4(k, &a)->gen;
+                       0;
+               }));
+       }
+
+       bch2_trans_put(trans);
+       up_read(&c->gc_lock);
+
+       bch_err_fn(c, ret);
        return ret;
 }
 
@@ -627,20 +662,22 @@ static int bch2_bucket_do_index(struct btree_trans *trans,
                return 0;
        }
 
-       bch2_trans_iter_init(trans, &iter, btree,
+       old = bch2_bkey_get_iter(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;
+               return ret;
 
        if (ca->mi.freespace_initialized &&
+           c->curr_recovery_pass > BCH_RECOVERY_PASS_check_alloc_info &&
            bch2_trans_inconsistent_on(old.k->type != old_type, trans,
-                       "incorrect key when %s %s btree (got %s should be %s)\n"
+                       "incorrect key when %s %s:%llu:%llu:0 (got %s should be %s)\n"
                        "  for %s",
                        set ? "setting" : "clearing",
-                       bch2_btree_ids[btree],
+                       bch2_btree_id_str(btree),
+                       iter.pos.inode,
+                       iter.pos.offset,
                        bch2_bkey_types[old.k->type],
                        bch2_bkey_types[old_type],
                        (bch2_bkey_val_to_text(&buf, c, alloc_k), buf.buf))) {
@@ -655,67 +692,218 @@ err:
        return ret;
 }
 
-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)
+static noinline int bch2_bucket_gen_update(struct btree_trans *trans,
+                                          struct bpos bucket, u8 gen)
+{
+       struct btree_iter iter;
+       unsigned offset;
+       struct bpos pos = alloc_gens_pos(bucket, &offset);
+       struct bkey_i_bucket_gens *g;
+       struct bkey_s_c k;
+       int ret;
+
+       g = bch2_trans_kmalloc(trans, sizeof(*g));
+       ret = PTR_ERR_OR_ZERO(g);
+       if (ret)
+               return ret;
+
+       k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_bucket_gens, pos,
+                              BTREE_ITER_INTENT|
+                              BTREE_ITER_WITH_UPDATES);
+       ret = bkey_err(k);
+       if (ret)
+               return ret;
+
+       if (k.k->type != KEY_TYPE_bucket_gens) {
+               bkey_bucket_gens_init(&g->k_i);
+               g->k.p = iter.pos;
+       } else {
+               bkey_reassemble(&g->k_i, k);
+       }
+
+       g->v.gens[offset] = gen;
+
+       ret = bch2_trans_update(trans, &iter, &g->k_i, 0);
+       bch2_trans_iter_exit(trans, &iter);
+       return ret;
+}
+
+int bch2_trigger_alloc(struct btree_trans *trans,
+                      enum btree_id btree, unsigned level,
+                      struct bkey_s_c old, struct bkey_s new,
+                      unsigned flags)
 {
        struct bch_fs *c = trans->c;
-       struct bch_alloc_v4 old_a_convert, *new_a;
-       const struct bch_alloc_v4 *old_a;
-       u64 old_lru, new_lru;
        int ret = 0;
 
-       /*
-        * Deletion only happens in the device removal path, with
-        * BTREE_TRIGGER_NORUN:
-        */
-       BUG_ON(new->k.type != KEY_TYPE_alloc_v4);
+       if (bch2_trans_inconsistent_on(!bch2_dev_bucket_exists(c, new.k->p), trans,
+                                      "alloc key for invalid device or bucket"))
+               return -EIO;
 
-       old_a = bch2_alloc_to_v4(old, &old_a_convert);
-       new_a = &bkey_i_to_alloc_v4(new)->v;
+       struct bch_dev *ca = bch_dev_bkey_exists(c, new.k->p.inode);
 
-       new_a->data_type = alloc_data_type(*new_a, new_a->data_type);
+       struct bch_alloc_v4 old_a_convert;
+       const struct bch_alloc_v4 *old_a = bch2_alloc_to_v4(old, &old_a_convert);
 
-       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);
-       }
+       if (flags & BTREE_TRIGGER_TRANSACTIONAL) {
+               struct bch_alloc_v4 *new_a = bkey_s_to_alloc_v4(new).v;
 
-       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);
+               new_a->data_type = alloc_data_type(*new_a, new_a->data_type);
+
+               if (bch2_bucket_sectors(*new_a) > bch2_bucket_sectors(*old_a)) {
+                       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);
+               }
+
+               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);
+               }
+
+               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, new.s_c, 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));
+
+               u64 old_lru = alloc_lru_idx_read(*old_a);
+               u64 new_lru = alloc_lru_idx_read(*new_a);
+               if (old_lru != new_lru) {
+                       ret = bch2_lru_change(trans, new.k->p.inode,
+                                             bucket_to_u64(new.k->p),
+                                             old_lru, new_lru);
+                       if (ret)
+                               return ret;
+               }
+
+               new_a->fragmentation_lru = alloc_lru_idx_fragmentation(*new_a,
+                                               bch_dev_bkey_exists(c, new.k->p.inode));
+               if (old_a->fragmentation_lru != new_a->fragmentation_lru) {
+                       ret = bch2_lru_change(trans,
+                                       BCH_LRU_FRAGMENTATION_START,
+                                       bucket_to_u64(new.k->p),
+                                       old_a->fragmentation_lru, new_a->fragmentation_lru);
+                       if (ret)
+                               return ret;
+               }
+
+               if (old_a->gen != new_a->gen) {
+                       ret = bch2_bucket_gen_update(trans, new.k->p, new_a->gen);
+                       if (ret)
+                               return ret;
+               }
+
+               /*
+                * need to know if we're getting called from the invalidate path or
+                * not:
+                */
+
+               if ((flags & BTREE_TRIGGER_BUCKET_INVALIDATE) &&
+                   old_a->cached_sectors) {
+                       ret = bch2_update_cached_sectors_list(trans, new.k->p.inode,
+                                                             -((s64) old_a->cached_sectors));
+                       if (ret)
+                               return ret;
+               }
        }
 
-       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 ((flags & BTREE_TRIGGER_ATOMIC) && (flags & BTREE_TRIGGER_INSERT)) {
+               struct bch_alloc_v4 *new_a = bkey_s_to_alloc_v4(new).v;
+               u64 journal_seq = trans->journal_res.seq;
+               u64 bucket_journal_seq = new_a->journal_seq;
+
+               if ((flags & BTREE_TRIGGER_INSERT) &&
+                   data_type_is_empty(old_a->data_type) !=
+                   data_type_is_empty(new_a->data_type) &&
+                   new.k->type == KEY_TYPE_alloc_v4) {
+                       struct bch_alloc_v4 *v = bkey_s_to_alloc_v4(new).v;
+
+                       /*
+                        * If the btree updates referring to a bucket weren't flushed
+                        * before the bucket became empty again, then the we don't have
+                        * to wait on a journal flush before we can reuse the bucket:
+                        */
+                       v->journal_seq = bucket_journal_seq =
+                               data_type_is_empty(new_a->data_type) &&
+                               (journal_seq == v->journal_seq ||
+                                bch2_journal_noflush_seq(&c->journal, v->journal_seq))
+                               ? 0 : journal_seq;
+               }
+
+               if (!data_type_is_empty(old_a->data_type) &&
+                   data_type_is_empty(new_a->data_type) &&
+                   bucket_journal_seq) {
+                       ret = bch2_set_bucket_needs_journal_commit(&c->buckets_waiting_for_journal,
+                                       c->journal.flushed_seq_ondisk,
+                                       new.k->p.inode, new.k->p.offset,
+                                       bucket_journal_seq);
+                       if (ret) {
+                               bch2_fs_fatal_error(c,
+                                       "error setting bucket_needs_journal_commit: %i", ret);
+                               return ret;
+                       }
+               }
+
+               percpu_down_read(&c->mark_lock);
+               if (new_a->gen != old_a->gen)
+                       *bucket_gen(ca, new.k->p.offset) = new_a->gen;
+
+               bch2_dev_usage_update(c, ca, old_a, new_a, journal_seq, false);
+               percpu_up_read(&c->mark_lock);
+
+#define eval_state(_a, expr)           ({ const struct bch_alloc_v4 *a = _a; expr; })
+#define statechange(expr)              !eval_state(old_a, expr) && eval_state(new_a, expr)
+#define bucket_flushed(a)              (!a->journal_seq || a->journal_seq <= c->journal.flushed_seq_ondisk)
+
+               if (statechange(a->data_type == BCH_DATA_free &&
+                               bucket_flushed(a)))
+                       closure_wake_up(&c->freelist_wait);
+
+               if (statechange(a->data_type == BCH_DATA_need_discard &&
+                               bucket_flushed(a)) &&
+                   !bch2_bucket_is_open(c, new.k->p.inode, new.k->p.offset))
+                       bch2_do_discards(c);
+
+               if (statechange(a->data_type == BCH_DATA_cached) &&
+                   !bch2_bucket_is_open(c, new.k->p.inode, new.k->p.offset) &&
+                   should_invalidate_buckets(ca, bch2_dev_usage_read(ca)))
+                       bch2_do_invalidates(c);
+
+               if (statechange(a->data_type == BCH_DATA_need_gc_gens))
+                       bch2_do_gc_gens(c);
        }
 
-       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));
+       if ((flags & BTREE_TRIGGER_GC) &&
+           (flags & BTREE_TRIGGER_BUCKET_INVALIDATE)) {
+               struct bch_alloc_v4 new_a_convert;
+               const struct bch_alloc_v4 *new_a = bch2_alloc_to_v4(new.s_c, &new_a_convert);
 
-       old_lru = alloc_lru_idx(*old_a);
-       new_lru = alloc_lru_idx(*new_a);
+               percpu_down_read(&c->mark_lock);
+               struct bucket *g = gc_bucket(ca, new.k->p.offset);
 
-       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;
+               bucket_lock(g);
 
-               if (new_a->data_type == BCH_DATA_cached)
-                       new_a->io_time[READ] = new_lru;
+               g->gen_valid            = 1;
+               g->gen                  = new_a->gen;
+               g->data_type            = new_a->data_type;
+               g->stripe               = new_a->stripe;
+               g->stripe_redundancy    = new_a->stripe_redundancy;
+               g->dirty_sectors        = new_a->dirty_sectors;
+               g->cached_sectors       = new_a->cached_sectors;
+
+               bucket_unlock(g);
+               percpu_up_read(&c->mark_lock);
        }
 
        return 0;
@@ -725,7 +913,7 @@ int bch2_trans_mark_alloc(struct btree_trans *trans,
  * This synthesizes deleted extents for holes, similar to BTREE_ITER_SLOTS for
  * extents style btrees, but works on non-extents btrees:
  */
-struct bkey_s_c bch2_get_key_or_hole(struct btree_iter *iter, struct bpos end, struct bkey *hole)
+static struct bkey_s_c bch2_get_key_or_hole(struct btree_iter *iter, struct bpos end, struct bkey *hole)
 {
        struct bkey_s_c k = bch2_btree_iter_peek_slot(iter);
 
@@ -739,10 +927,18 @@ struct bkey_s_c bch2_get_key_or_hole(struct btree_iter *iter, struct bpos end, s
                struct bpos next;
 
                bch2_trans_copy_iter(&iter2, iter);
-               k = bch2_btree_iter_peek_upto(&iter2,
-                               bkey_min(bkey_min(end,
-                                                 iter->path->l[0].b->key.k.p),
-                                                 POS(iter->pos.inode, iter->pos.offset + U32_MAX - 1)));
+
+               struct btree_path *path = btree_iter_path(iter->trans, iter);
+               if (!bpos_eq(path->l[0].b->key.k.p, SPOS_MAX))
+                       end = bkey_min(end, bpos_nosnap_successor(path->l[0].b->key.k.p));
+
+               end = bkey_min(end, POS(iter->pos.inode, iter->pos.offset + U32_MAX - 1));
+
+               /*
+                * btree node min/max is a closed interval, upto takes a half
+                * open interval:
+                */
+               k = bch2_btree_iter_peek_upto(&iter2, end);
                next = iter2.pos;
                bch2_trans_iter_exit(iter->trans, &iter2);
 
@@ -762,7 +958,6 @@ struct bkey_s_c bch2_get_key_or_hole(struct btree_iter *iter, struct bpos end, s
 static bool next_bucket(struct bch_fs *c, struct bpos *bucket)
 {
        struct bch_dev *ca;
-       unsigned iter;
 
        if (bch2_dev_bucket_exists(c, *bucket))
                return true;
@@ -780,16 +975,15 @@ static bool next_bucket(struct bch_fs *c, struct bpos *bucket)
        }
 
        rcu_read_lock();
-       iter = bucket->inode;
-       ca = __bch2_next_dev(c, &iter, NULL);
+       ca = __bch2_next_dev_idx(c, bucket->inode, NULL);
        if (ca)
-               bucket->offset = ca->mi.first_bucket;
+               *bucket = POS(ca->dev_idx, ca->mi.first_bucket);
        rcu_read_unlock();
 
        return ca != NULL;
 }
 
-struct bkey_s_c bch2_get_key_or_real_bucket_hole(struct btree_iter *iter, struct bkey *hole)
+static struct bkey_s_c bch2_get_key_or_real_bucket_hole(struct btree_iter *iter, struct bkey *hole)
 {
        struct bch_fs *c = iter->trans->c;
        struct bkey_s_c k;
@@ -819,22 +1013,26 @@ again:
        return k;
 }
 
-static int bch2_check_alloc_key(struct btree_trans *trans,
-                               struct bkey_s_c alloc_k,
-                               struct btree_iter *alloc_iter,
-                               struct btree_iter *discard_iter,
-                               struct btree_iter *freespace_iter)
+static noinline_for_stack
+int bch2_check_alloc_key(struct btree_trans *trans,
+                        struct bkey_s_c alloc_k,
+                        struct btree_iter *alloc_iter,
+                        struct btree_iter *discard_iter,
+                        struct btree_iter *freespace_iter,
+                        struct btree_iter *bucket_gens_iter)
 {
        struct bch_fs *c = trans->c;
        struct bch_dev *ca;
        struct bch_alloc_v4 a_convert;
        const struct bch_alloc_v4 *a;
        unsigned discard_key_type, freespace_key_type;
+       unsigned gens_offset;
        struct bkey_s_c k;
        struct printbuf buf = PRINTBUF;
        int ret;
 
        if (fsck_err_on(!bch2_dev_bucket_exists(c, alloc_k.k->p), c,
+                       alloc_key_to_missing_dev_bucket,
                        "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);
@@ -845,14 +1043,8 @@ static int bch2_check_alloc_key(struct btree_trans *trans,
 
        a = bch2_alloc_to_v4(alloc_k, &a_convert);
 
-       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;
-
+       discard_key_type = a->data_type == BCH_DATA_need_discard ? KEY_TYPE_set : 0;
        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));
-
        k = bch2_btree_iter_peek_slot(discard_iter);
        ret = bkey_err(k);
        if (ret)
@@ -860,7 +1052,8 @@ static int bch2_check_alloc_key(struct btree_trans *trans,
 
        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"
+            fsck_err(c, need_discard_key_wrong,
+                     "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],
@@ -881,6 +1074,8 @@ static int bch2_check_alloc_key(struct btree_trans *trans,
                        goto err;
        }
 
+       freespace_key_type = a->data_type == BCH_DATA_free ? KEY_TYPE_set : 0;
+       bch2_btree_iter_set_pos(freespace_iter, alloc_freespace_pos(alloc_k.k->p, *a));
        k = bch2_btree_iter_peek_slot(freespace_iter);
        ret = bkey_err(k);
        if (ret)
@@ -888,7 +1083,8 @@ static int bch2_check_alloc_key(struct btree_trans *trans,
 
        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"
+            fsck_err(c, freespace_key_wrong,
+                     "incorrect key in freespace btree (got %s should be %s)\n"
                      "  %s",
                      bch2_bkey_types[k.k->type],
                      bch2_bkey_types[freespace_key_type],
@@ -910,16 +1106,52 @@ static int bch2_check_alloc_key(struct btree_trans *trans,
                if (ret)
                        goto err;
        }
+
+       bch2_btree_iter_set_pos(bucket_gens_iter, alloc_gens_pos(alloc_k.k->p, &gens_offset));
+       k = bch2_btree_iter_peek_slot(bucket_gens_iter);
+       ret = bkey_err(k);
+       if (ret)
+               goto err;
+
+       if (a->gen != alloc_gen(k, gens_offset) &&
+           (c->opts.reconstruct_alloc ||
+            fsck_err(c, bucket_gens_key_wrong,
+                     "incorrect gen in bucket_gens btree (got %u should be %u)\n"
+                     "  %s",
+                     alloc_gen(k, gens_offset), a->gen,
+                     (printbuf_reset(&buf),
+                      bch2_bkey_val_to_text(&buf, c, alloc_k), buf.buf)))) {
+               struct bkey_i_bucket_gens *g =
+                       bch2_trans_kmalloc(trans, sizeof(*g));
+
+               ret = PTR_ERR_OR_ZERO(g);
+               if (ret)
+                       goto err;
+
+               if (k.k->type == KEY_TYPE_bucket_gens) {
+                       bkey_reassemble(&g->k_i, k);
+               } else {
+                       bkey_bucket_gens_init(&g->k_i);
+                       g->k.p = alloc_gens_pos(alloc_k.k->p, &gens_offset);
+               }
+
+               g->v.gens[gens_offset] = a->gen;
+
+               ret = bch2_trans_update(trans, bucket_gens_iter, &g->k_i, 0);
+               if (ret)
+                       goto err;
+       }
 err:
 fsck_err:
        printbuf_exit(&buf);
        return ret;
 }
 
-static int bch2_check_alloc_hole(struct btree_trans *trans,
-                                struct bpos start,
-                                struct bpos *end,
-                                struct btree_iter *freespace_iter)
+static noinline_for_stack
+int bch2_check_alloc_hole_freespace(struct btree_trans *trans,
+                                   struct bpos start,
+                                   struct bpos *end,
+                                   struct btree_iter *freespace_iter)
 {
        struct bch_fs *c = trans->c;
        struct bch_dev *ca;
@@ -942,7 +1174,8 @@ static int bch2_check_alloc_hole(struct btree_trans *trans,
 
        if (k.k->type != KEY_TYPE_set &&
            (c->opts.reconstruct_alloc ||
-            fsck_err(c, "hole in alloc btree missing in freespace btree\n"
+            fsck_err(c, freespace_hole_missing,
+                     "hole in alloc btree missing in freespace btree\n"
                      "  device %llu buckets %llu-%llu",
                      freespace_iter->pos.inode,
                      freespace_iter->pos.offset,
@@ -971,8 +1204,71 @@ fsck_err:
        return ret;
 }
 
-static int bch2_check_discard_freespace_key(struct btree_trans *trans,
-                                           struct btree_iter *iter)
+static noinline_for_stack
+int bch2_check_alloc_hole_bucket_gens(struct btree_trans *trans,
+                                     struct bpos start,
+                                     struct bpos *end,
+                                     struct btree_iter *bucket_gens_iter)
+{
+       struct bch_fs *c = trans->c;
+       struct bkey_s_c k;
+       struct printbuf buf = PRINTBUF;
+       unsigned i, gens_offset, gens_end_offset;
+       int ret;
+
+       bch2_btree_iter_set_pos(bucket_gens_iter, alloc_gens_pos(start, &gens_offset));
+
+       k = bch2_btree_iter_peek_slot(bucket_gens_iter);
+       ret = bkey_err(k);
+       if (ret)
+               goto err;
+
+       if (bkey_cmp(alloc_gens_pos(start, &gens_offset),
+                    alloc_gens_pos(*end,  &gens_end_offset)))
+               gens_end_offset = KEY_TYPE_BUCKET_GENS_NR;
+
+       if (k.k->type == KEY_TYPE_bucket_gens) {
+               struct bkey_i_bucket_gens g;
+               bool need_update = false;
+
+               bkey_reassemble(&g.k_i, k);
+
+               for (i = gens_offset; i < gens_end_offset; i++) {
+                       if (fsck_err_on(g.v.gens[i], c,
+                                       bucket_gens_hole_wrong,
+                                       "hole in alloc btree at %llu:%llu with nonzero gen in bucket_gens btree (%u)",
+                                       bucket_gens_pos_to_alloc(k.k->p, i).inode,
+                                       bucket_gens_pos_to_alloc(k.k->p, i).offset,
+                                       g.v.gens[i])) {
+                               g.v.gens[i] = 0;
+                               need_update = true;
+                       }
+               }
+
+               if (need_update) {
+                       struct bkey_i *u = bch2_trans_kmalloc(trans, sizeof(g));
+
+                       ret = PTR_ERR_OR_ZERO(u);
+                       if (ret)
+                               goto err;
+
+                       memcpy(u, &g, sizeof(g));
+
+                       ret = bch2_trans_update(trans, bucket_gens_iter, u, 0);
+                       if (ret)
+                               goto err;
+               }
+       }
+
+       *end = bkey_min(*end, bucket_gens_pos_to_alloc(bpos_nosnap_successor(k.k->p), 0));
+err:
+fsck_err:
+       printbuf_exit(&buf);
+       return ret;
+}
+
+static noinline_for_stack int bch2_check_discard_freespace_key(struct btree_trans *trans,
+                                             struct btree_iter *iter)
 {
        struct bch_fs *c = trans->c;
        struct btree_iter alloc_iter;
@@ -991,62 +1287,143 @@ static int bch2_check_discard_freespace_key(struct btree_trans *trans,
        pos.offset &= ~(~0ULL << 56);
        genbits = iter->pos.offset & (~0ULL << 56);
 
-       bch2_trans_iter_init(trans, &alloc_iter, BTREE_ID_alloc, pos, 0);
+       alloc_k = bch2_bkey_get_iter(trans, &alloc_iter, BTREE_ID_alloc, pos, 0);
+       ret = bkey_err(alloc_k);
+       if (ret)
+               return ret;
 
        if (fsck_err_on(!bch2_dev_bucket_exists(c, pos), c,
+                       need_discard_freespace_key_to_invalid_dev_bucket,
                        "entry in %s btree for nonexistant dev:bucket %llu:%llu",
-                       bch2_btree_ids[iter->btree_id], pos.inode, pos.offset))
+                       bch2_btree_id_str(iter->btree_id), pos.inode, pos.offset))
                goto delete;
 
-       alloc_k = bch2_btree_iter_peek_slot(&alloc_iter);
-       ret = bkey_err(alloc_k);
-       if (ret)
-               goto err;
-
        a = bch2_alloc_to_v4(alloc_k, &a_convert);
 
        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)",
+                       need_discard_freespace_key_bad,
+                       "%s\n  incorrectly set at %s:%llu:%llu:0 (free %u, genbits %llu should be %llu)",
                        (bch2_bkey_val_to_text(&buf, c, alloc_k), buf.buf),
-                       bch2_btree_ids[iter->btree_id],
+                       bch2_btree_id_str(iter->btree_id),
+                       iter->pos.inode,
+                       iter->pos.offset,
                        a->data_type == state,
                        genbits >> 56, alloc_freespace_genbits(*a) >> 56))
                goto delete;
 out:
-err:
 fsck_err:
+       set_btree_iter_dontneed(&alloc_iter);
        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);
+       ret =   bch2_btree_delete_extent_at(trans, iter,
+                       iter->btree_id == BTREE_ID_freespace ? 1 : 0, 0) ?:
+               bch2_trans_commit(trans, NULL, NULL,
+                       BCH_TRANS_COMMIT_no_enospc);
        goto out;
 }
 
+/*
+ * We've already checked that generation numbers in the bucket_gens btree are
+ * valid for buckets that exist; this just checks for keys for nonexistent
+ * buckets.
+ */
+static noinline_for_stack
+int bch2_check_bucket_gens_key(struct btree_trans *trans,
+                              struct btree_iter *iter,
+                              struct bkey_s_c k)
+{
+       struct bch_fs *c = trans->c;
+       struct bkey_i_bucket_gens g;
+       struct bch_dev *ca;
+       u64 start = bucket_gens_pos_to_alloc(k.k->p, 0).offset;
+       u64 end = bucket_gens_pos_to_alloc(bpos_nosnap_successor(k.k->p), 0).offset;
+       u64 b;
+       bool need_update = false, dev_exists;
+       struct printbuf buf = PRINTBUF;
+       int ret = 0;
+
+       BUG_ON(k.k->type != KEY_TYPE_bucket_gens);
+       bkey_reassemble(&g.k_i, k);
+
+       /* if no bch_dev, skip out whether we repair or not */
+       dev_exists = bch2_dev_exists2(c, k.k->p.inode);
+       if (!dev_exists) {
+               if (fsck_err_on(!dev_exists, c,
+                               bucket_gens_to_invalid_dev,
+                               "bucket_gens key for invalid device:\n  %s",
+                               (bch2_bkey_val_to_text(&buf, c, k), buf.buf))) {
+                       ret = bch2_btree_delete_at(trans, iter, 0);
+               }
+               goto out;
+       }
+
+       ca = bch_dev_bkey_exists(c, k.k->p.inode);
+       if (fsck_err_on(end <= ca->mi.first_bucket ||
+                       start >= ca->mi.nbuckets, c,
+                       bucket_gens_to_invalid_buckets,
+                       "bucket_gens key for invalid buckets:\n  %s",
+                       (bch2_bkey_val_to_text(&buf, c, k), buf.buf))) {
+               ret = bch2_btree_delete_at(trans, iter, 0);
+               goto out;
+       }
+
+       for (b = start; b < ca->mi.first_bucket; b++)
+               if (fsck_err_on(g.v.gens[b & KEY_TYPE_BUCKET_GENS_MASK], c,
+                               bucket_gens_nonzero_for_invalid_buckets,
+                               "bucket_gens key has nonzero gen for invalid bucket")) {
+                       g.v.gens[b & KEY_TYPE_BUCKET_GENS_MASK] = 0;
+                       need_update = true;
+               }
+
+       for (b = ca->mi.nbuckets; b < end; b++)
+               if (fsck_err_on(g.v.gens[b & KEY_TYPE_BUCKET_GENS_MASK], c,
+                               bucket_gens_nonzero_for_invalid_buckets,
+                               "bucket_gens key has nonzero gen for invalid bucket")) {
+                       g.v.gens[b & KEY_TYPE_BUCKET_GENS_MASK] = 0;
+                       need_update = true;
+               }
+
+       if (need_update) {
+               struct bkey_i *u = bch2_trans_kmalloc(trans, sizeof(g));
+
+               ret = PTR_ERR_OR_ZERO(u);
+               if (ret)
+                       goto out;
+
+               memcpy(u, &g, sizeof(g));
+               ret = bch2_trans_update(trans, iter, u, 0);
+       }
+out:
+fsck_err:
+       printbuf_exit(&buf);
+       return ret;
+}
+
 int bch2_check_alloc_info(struct bch_fs *c)
 {
-       struct btree_trans trans;
-       struct btree_iter iter, discard_iter, freespace_iter;
+       struct btree_trans *trans = bch2_trans_get(c);
+       struct btree_iter iter, discard_iter, freespace_iter, bucket_gens_iter;
        struct bkey hole;
        struct bkey_s_c k;
        int ret = 0;
 
-       bch2_trans_init(&trans, c, 0, 0);
-
-       bch2_trans_iter_init(&trans, &iter, BTREE_ID_alloc, POS_MIN,
+       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,
+       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,
+       bch2_trans_iter_init(trans, &freespace_iter, BTREE_ID_freespace, POS_MIN,
+                            BTREE_ITER_PREFETCH);
+       bch2_trans_iter_init(trans, &bucket_gens_iter, BTREE_ID_bucket_gens, POS_MIN,
                             BTREE_ITER_PREFETCH);
 
        while (1) {
                struct bpos next;
 
-               bch2_trans_begin(&trans);
+               bch2_trans_begin(trans);
 
                k = bch2_get_key_or_real_bucket_hole(&iter, &hole);
                ret = bkey_err(k);
@@ -1059,26 +1436,30 @@ int bch2_check_alloc_info(struct bch_fs *c)
                if (k.k->type) {
                        next = bpos_nosnap_successor(k.k->p);
 
-                       ret = bch2_check_alloc_key(&trans,
+                       ret = bch2_check_alloc_key(trans,
                                                   k, &iter,
                                                   &discard_iter,
-                                                  &freespace_iter);
+                                                  &freespace_iter,
+                                                  &bucket_gens_iter);
                        if (ret)
-                               break;
+                               goto bkey_err;
                } else {
                        next = k.k->p;
 
-                       ret = bch2_check_alloc_hole(&trans,
+                       ret = bch2_check_alloc_hole_freespace(trans,
+                                                   bkey_start_pos(k.k),
+                                                   &next,
+                                                   &freespace_iter) ?:
+                               bch2_check_alloc_hole_bucket_gens(trans,
                                                    bkey_start_pos(k.k),
                                                    &next,
-                                                   &freespace_iter);
+                                                   &bucket_gens_iter);
                        if (ret)
                                goto bkey_err;
                }
 
-               ret = bch2_trans_commit(&trans, NULL, NULL,
-                                       BTREE_INSERT_NOFAIL|
-                                       BTREE_INSERT_LAZY_RW);
+               ret = bch2_trans_commit(trans, NULL, NULL,
+                                       BCH_TRANS_COMMIT_no_enospc);
                if (ret)
                        goto bkey_err;
 
@@ -1089,26 +1470,59 @@ bkey_err:
                if (ret)
                        break;
        }
-       bch2_trans_iter_exit(&trans, &freespace_iter);
-       bch2_trans_iter_exit(&trans, &discard_iter);
-       bch2_trans_iter_exit(&trans, &iter);
+       bch2_trans_iter_exit(trans, &bucket_gens_iter);
+       bch2_trans_iter_exit(trans, &freespace_iter);
+       bch2_trans_iter_exit(trans, &discard_iter);
+       bch2_trans_iter_exit(trans, &iter);
 
        if (ret < 0)
                goto err;
 
-       ret = for_each_btree_key_commit(&trans, iter,
+       ret = for_each_btree_key(trans, iter,
                        BTREE_ID_need_discard, POS_MIN,
                        BTREE_ITER_PREFETCH, k,
-                       NULL, NULL, BTREE_INSERT_NOFAIL|BTREE_INSERT_LAZY_RW,
-               bch2_check_discard_freespace_key(&trans, &iter)) ?:
-             for_each_btree_key_commit(&trans, iter,
-                       BTREE_ID_freespace, POS_MIN,
+               bch2_check_discard_freespace_key(trans, &iter));
+       if (ret)
+               goto err;
+
+       bch2_trans_iter_init(trans, &iter, BTREE_ID_freespace, POS_MIN,
+                            BTREE_ITER_PREFETCH);
+       while (1) {
+               bch2_trans_begin(trans);
+               k = bch2_btree_iter_peek(&iter);
+               if (!k.k)
+                       break;
+
+               ret = bkey_err(k) ?:
+                       bch2_check_discard_freespace_key(trans, &iter);
+               if (bch2_err_matches(ret, BCH_ERR_transaction_restart)) {
+                       ret = 0;
+                       continue;
+               }
+               if (ret) {
+                       struct printbuf buf = PRINTBUF;
+                       bch2_bkey_val_to_text(&buf, c, k);
+
+                       bch_err(c, "while checking %s", buf.buf);
+                       printbuf_exit(&buf);
+                       break;
+               }
+
+               bch2_btree_iter_set_pos(&iter, bpos_nosnap_successor(iter.pos));
+       }
+       bch2_trans_iter_exit(trans, &iter);
+       if (ret)
+               goto err;
+
+       ret = for_each_btree_key_commit(trans, iter,
+                       BTREE_ID_bucket_gens, POS_MIN,
                        BTREE_ITER_PREFETCH, k,
-                       NULL, NULL, BTREE_INSERT_NOFAIL|BTREE_INSERT_LAZY_RW,
-               bch2_check_discard_freespace_key(&trans, &iter));
+                       NULL, NULL, BCH_TRANS_COMMIT_no_enospc,
+               bch2_check_bucket_gens_key(trans, &iter, k));
 err:
-       bch2_trans_exit(&trans);
-       return ret < 0 ? ret : 0;
+       bch2_trans_put(trans);
+       bch_err_fn(c, ret);
+       return ret;
 }
 
 static int bch2_check_alloc_to_lru_ref(struct btree_trans *trans,
@@ -1118,9 +1532,8 @@ static int bch2_check_alloc_to_lru_ref(struct btree_trans *trans,
        struct btree_iter lru_iter;
        struct bch_alloc_v4 a_convert;
        const struct bch_alloc_v4 *a;
-       struct bkey_s_c alloc_k, k;
+       struct bkey_s_c alloc_k, lru_k;
        struct printbuf buf = PRINTBUF;
-       struct printbuf buf2 = PRINTBUF;
        int ret;
 
        alloc_k = bch2_btree_iter_peek(alloc_iter);
@@ -1136,84 +1549,96 @@ static int bch2_check_alloc_to_lru_ref(struct btree_trans *trans,
        if (a->data_type != BCH_DATA_cached)
                return 0;
 
-       bch2_trans_iter_init(trans, &lru_iter, BTREE_ID_lru,
-                            POS(alloc_k.k->p.inode, a->io_time[READ]), 0);
-
-       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,
+                       alloc_key_cached_but_read_time_zero,
                        "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"
+                bch2_bkey_val_to_text(&buf, c, alloc_k), buf.buf))) {
+               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] = atomic64_read(&c->io_clock[READ].now);
+               ret = bch2_trans_update(trans, alloc_iter,
+                                       &a_mut->k_i, BTREE_TRIGGER_NORUN);
+               if (ret)
+                       goto err;
+
+               a = &a_mut->v;
+       }
+
+       lru_k = bch2_bkey_get_iter(trans, &lru_iter, BTREE_ID_lru,
+                            lru_pos(alloc_k.k->p.inode,
+                                    bucket_to_u64(alloc_k.k->p),
+                                    a->io_time[READ]), 0);
+       ret = bkey_err(lru_k);
+       if (ret)
+               return ret;
+
+       if (fsck_err_on(lru_k.k->type != KEY_TYPE_set, c,
+                       alloc_key_to_missing_lru_entry,
+                       "missing lru entry\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] ?:
-                       atomic64_read(&c->io_clock[READ].now);
-
+                        bch2_bkey_val_to_text(&buf, c, alloc_k), buf.buf))) {
                ret = bch2_lru_set(trans,
                                   alloc_k.k->p.inode,
-                                  alloc_k.k->p.offset,
-                                  &read_time);
+                                  bucket_to_u64(alloc_k.k->p),
+                                  a->io_time[READ]);
                if (ret)
                        goto err;
-
-               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] = read_time;
-                       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;
 }
 
 int bch2_check_alloc_to_lru_refs(struct bch_fs *c)
 {
-       struct btree_trans trans;
-       struct btree_iter iter;
-       struct bkey_s_c k;
-       int ret = 0;
+       int ret = bch2_trans_run(c,
+               for_each_btree_key_commit(trans, iter, BTREE_ID_alloc,
+                               POS_MIN, BTREE_ITER_PREFETCH, k,
+                               NULL, NULL, BCH_TRANS_COMMIT_no_enospc,
+                       bch2_check_alloc_to_lru_ref(trans, &iter)));
+       bch_err_fn(c, ret);
+       return ret;
+}
+
+struct discard_buckets_state {
+       u64             seen;
+       u64             open;
+       u64             need_journal_commit;
+       u64             discarded;
+       struct bch_dev  *ca;
+       u64             need_journal_commit_this_dev;
+};
 
-       bch2_trans_init(&trans, c, 0, 0);
+static void discard_buckets_next_dev(struct bch_fs *c, struct discard_buckets_state *s, struct bch_dev *ca)
+{
+       if (s->ca == ca)
+               return;
 
-       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));
+       if (s->ca && s->need_journal_commit_this_dev >
+           bch2_dev_usage_read(s->ca).d[BCH_DATA_free].buckets)
+               bch2_journal_flush_async(&c->journal, NULL);
 
-       bch2_trans_exit(&trans);
-       return ret < 0 ? ret : 0;
+       if (s->ca)
+               percpu_ref_put(&s->ca->ref);
+       if (ca)
+               percpu_ref_get(&ca->ref);
+       s->ca = ca;
+       s->need_journal_commit_this_dev = 0;
 }
 
 static int bch2_discard_one_bucket(struct btree_trans *trans,
                                   struct btree_iter *need_discard_iter,
                                   struct bpos *discard_pos_done,
-                                  u64 *seen,
-                                  u64 *open,
-                                  u64 *need_journal_commit,
-                                  u64 *discarded)
+                                  struct discard_buckets_state *s)
 {
        struct bch_fs *c = trans->c;
        struct bpos pos = need_discard_iter->pos;
@@ -1222,31 +1647,33 @@ static int bch2_discard_one_bucket(struct btree_trans *trans,
        struct bch_dev *ca;
        struct bkey_i_alloc_v4 *a;
        struct printbuf buf = PRINTBUF;
-       bool did_discard = false;
        int ret = 0;
 
        ca = bch_dev_bkey_exists(c, pos.inode);
+
        if (!percpu_ref_tryget(&ca->io_ref)) {
                bch2_btree_iter_set_pos(need_discard_iter, POS(pos.inode + 1, 0));
                return 0;
        }
 
+       discard_buckets_next_dev(c, s, ca);
+
        if (bch2_bucket_is_open_safe(c, pos.inode, pos.offset)) {
-               (*open)++;
+               s->open++;
                goto out;
        }
 
        if (bch2_bucket_needs_journal_commit(&c->buckets_waiting_for_journal,
                        c->journal.flushed_seq_ondisk,
                        pos.inode, pos.offset)) {
-               (*need_journal_commit)++;
+               s->need_journal_commit++;
+               s->need_journal_commit_this_dev++;
                goto out;
        }
 
-       bch2_trans_iter_init(trans, &iter, BTREE_ID_alloc,
-                            need_discard_iter->pos,
-                            BTREE_ITER_CACHED);
-       k = bch2_btree_iter_peek_slot(&iter);
+       k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_alloc,
+                              need_discard_iter->pos,
+                              BTREE_ITER_CACHED);
        ret = bkey_err(k);
        if (ret)
                goto out;
@@ -1262,21 +1689,28 @@ static int bch2_discard_one_bucket(struct btree_trans *trans,
                goto write;
        }
 
-       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;
+       if (a->v.journal_seq > c->journal.flushed_seq_ondisk) {
+               if (c->curr_recovery_pass > BCH_RECOVERY_PASS_check_alloc_info) {
+                       bch2_trans_inconsistent(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;
        }
 
-       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;
+       if (a->v.data_type != BCH_DATA_need_discard) {
+               if (c->curr_recovery_pass > BCH_RECOVERY_PASS_check_alloc_info) {
+                       bch2_trans_inconsistent(trans,
+                               "bucket incorrectly set in need_discard btree\n"
+                               "%s",
+                               (bch2_bkey_val_to_text(&buf, c, k), buf.buf));
+                       ret = -EIO;
+               }
+
                goto out;
        }
 
@@ -1286,34 +1720,32 @@ static int bch2_discard_one_bucket(struct btree_trans *trans,
                 * This works without any other locks because this is the only
                 * thread that removes items from the need_discard tree
                 */
-               bch2_trans_unlock(trans);
+               bch2_trans_unlock_long(trans);
                blkdev_issue_discard(ca->disk_sb.bdev,
                                     k.k->p.offset * ca->mi.bucket_size,
                                     ca->mi.bucket_size,
                                     GFP_KERNEL);
+               *discard_pos_done = iter.pos;
 
-               ret = bch2_trans_relock(trans);
+               ret = bch2_trans_relock_notrace(trans);
                if (ret)
                        goto out;
        }
 
-       *discard_pos_done = iter.pos;
-       did_discard = true;
-
        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) ?:
                bch2_trans_commit(trans, NULL, NULL,
-                                 BTREE_INSERT_USE_RESERVE|BTREE_INSERT_NOFAIL);
+                                 BCH_WATERMARK_btree|
+                                 BCH_TRANS_COMMIT_no_enospc);
        if (ret)
                goto out;
 
-       if (did_discard) {
-               this_cpu_inc(c->counters[BCH_COUNTER_bucket_discard]);
-               (*discarded)++;
-       }
+       count_event(c, bucket_discard);
+       s->discarded++;
 out:
+       s->seen++;
        bch2_trans_iter_exit(trans, &iter);
        percpu_ref_put(&ca->io_ref);
        printbuf_exit(&buf);
@@ -1323,97 +1755,69 @@ out:
 static void bch2_do_discards_work(struct work_struct *work)
 {
        struct bch_fs *c = container_of(work, struct bch_fs, discard_work);
-       struct btree_trans trans;
-       struct btree_iter iter;
-       struct bkey_s_c k;
-       u64 seen = 0, open = 0, need_journal_commit = 0, discarded = 0;
+       struct discard_buckets_state s = {};
        struct bpos discard_pos_done = POS_MAX;
        int ret;
 
-       bch2_trans_init(&trans, c, 0, 0);
-
        /*
         * We're doing the commit in bch2_discard_one_bucket instead of using
         * for_each_btree_key_commit() so that we can increment counters after
         * successful commit:
         */
-       ret = for_each_btree_key2(&trans, iter,
-                       BTREE_ID_need_discard, POS_MIN, 0, k,
-               bch2_discard_one_bucket(&trans, &iter, &discard_pos_done,
-                                       &seen,
-                                       &open,
-                                       &need_journal_commit,
-                                       &discarded));
-
-       bch2_trans_exit(&trans);
-
-       if (need_journal_commit * 2 > seen)
-               bch2_journal_flush_async(&c->journal, NULL);
+       ret = bch2_trans_run(c,
+               for_each_btree_key(trans, iter,
+                                  BTREE_ID_need_discard, POS_MIN, 0, k,
+                       bch2_discard_one_bucket(trans, &iter, &discard_pos_done, &s)));
 
-       percpu_ref_put(&c->writes);
+       discard_buckets_next_dev(c, &s, NULL);
 
-       trace_discard_buckets(c, seen, open, need_journal_commit, discarded,
+       trace_discard_buckets(c, s.seen, s.open, s.need_journal_commit, s.discarded,
                              bch2_err_str(ret));
+
+       bch2_write_ref_put(c, BCH_WRITE_REF_discard);
 }
 
 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);
+       if (bch2_write_ref_tryget(c, BCH_WRITE_REF_discard) &&
+           !queue_work(c->write_ref_wq, &c->discard_work))
+               bch2_write_ref_put(c, BCH_WRITE_REF_discard);
 }
 
 static int invalidate_one_bucket(struct btree_trans *trans,
-                                struct btree_iter *lru_iter, struct bkey_s_c k,
-                                unsigned dev_idx, s64 *nr_to_invalidate)
+                                struct btree_iter *lru_iter,
+                                struct bkey_s_c lru_k,
+                                s64 *nr_to_invalidate)
 {
        struct bch_fs *c = trans->c;
        struct btree_iter alloc_iter = { NULL };
-       struct bkey_i_alloc_v4 *a;
-       struct bpos bucket;
+       struct bkey_i_alloc_v4 *a = NULL;
        struct printbuf buf = PRINTBUF;
+       struct bpos bucket = u64_to_bucket(lru_k.k->p.offset);
        unsigned cached_sectors;
        int ret = 0;
 
-       if (*nr_to_invalidate <= 0 || k.k->p.inode != dev_idx)
+       if (*nr_to_invalidate <= 0)
                return 1;
 
-       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);
-
-               if (!test_bit(BCH_FS_CHECK_LRUS_DONE, &c->flags)) {
-                       bch_err(c, "%s", buf.buf);
-               } else {
-                       bch2_trans_inconsistent(trans, "%s", buf.buf);
-                       ret = -EINVAL;
-               }
-
-               goto out;
+       if (!bch2_dev_bucket_exists(c, bucket)) {
+               prt_str(&buf, "lru entry points to invalid bucket");
+               goto err;
        }
 
-       bucket = POS(dev_idx, le64_to_cpu(bkey_s_c_to_lru(k).v->idx));
+       if (bch2_bucket_is_open_safe(c, bucket.inode, bucket.offset))
+               return 0;
 
        a = bch2_trans_start_alloc_update(trans, &alloc_iter, bucket);
        ret = PTR_ERR_OR_ZERO(a);
        if (ret)
                goto out;
 
-       if (k.k->p.offset != 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);
-               } else {
-                       bch2_trans_inconsistent(trans, "%s", buf.buf);
-                       ret = -EINVAL;
-               }
-
+       /* We expect harmless races here due to the btree write buffer: */
+       if (lru_pos_time(lru_iter->pos) != alloc_lru_idx_read(a->v))
                goto out;
-       }
+
+       BUG_ON(a->v.data_type != BCH_DATA_cached);
 
        if (!a->v.cached_sectors)
                bch_err(c, "invalidating empty bucket, confused");
@@ -1431,7 +1835,8 @@ static int invalidate_one_bucket(struct btree_trans *trans,
        ret =   bch2_trans_update(trans, &alloc_iter, &a->k_i,
                                BTREE_TRIGGER_BUCKET_INVALIDATE) ?:
                bch2_trans_commit(trans, NULL, NULL,
-                                 BTREE_INSERT_USE_RESERVE|BTREE_INSERT_NOFAIL);
+                                 BCH_WATERMARK_btree|
+                                 BCH_TRANS_COMMIT_no_enospc);
        if (ret)
                goto out;
 
@@ -1441,66 +1846,95 @@ out:
        bch2_trans_iter_exit(trans, &alloc_iter);
        printbuf_exit(&buf);
        return ret;
+err:
+       prt_str(&buf, "\n  lru key: ");
+       bch2_bkey_val_to_text(&buf, c, lru_k);
+
+       prt_str(&buf, "\n  lru entry: ");
+       bch2_lru_pos_to_text(&buf, lru_iter->pos);
+
+       prt_str(&buf, "\n  alloc key: ");
+       if (!a)
+               bch2_bpos_to_text(&buf, bucket);
+       else
+               bch2_bkey_val_to_text(&buf, c, bkey_i_to_s_c(&a->k_i));
+
+       bch_err(c, "%s", buf.buf);
+       if (c->curr_recovery_pass > BCH_RECOVERY_PASS_check_lrus) {
+               bch2_inconsistent_error(c);
+               ret = -EINVAL;
+       }
+
+       goto out;
 }
 
 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 btree_iter iter;
-       struct bkey_s_c k;
-       unsigned i;
+       struct btree_trans *trans = bch2_trans_get(c);
        int ret = 0;
 
-       bch2_trans_init(&trans, c, 0, 0);
+       ret = bch2_btree_write_buffer_tryflush(trans);
+       if (ret)
+               goto err;
 
-       for_each_member_device(ca, c, i) {
+       for_each_member_device(c, ca) {
                s64 nr_to_invalidate =
                        should_invalidate_buckets(ca, bch2_dev_usage_read(ca));
 
-               ret = for_each_btree_key2(&trans, iter, BTREE_ID_lru,
-                               POS(ca->dev_idx, 0), BTREE_ITER_INTENT, k,
-                       invalidate_one_bucket(&trans, &iter, k, ca->dev_idx, &nr_to_invalidate));
+               ret = for_each_btree_key_upto(trans, iter, BTREE_ID_lru,
+                               lru_pos(ca->dev_idx, 0, 0),
+                               lru_pos(ca->dev_idx, U64_MAX, LRU_TIME_MAX),
+                               BTREE_ITER_INTENT, k,
+                       invalidate_one_bucket(trans, &iter, k, &nr_to_invalidate));
 
                if (ret < 0) {
                        percpu_ref_put(&ca->ref);
                        break;
                }
        }
-
-       bch2_trans_exit(&trans);
-       percpu_ref_put(&c->writes);
+err:
+       bch2_trans_put(trans);
+       bch2_write_ref_put(c, BCH_WRITE_REF_invalidate);
 }
 
 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 (bch2_write_ref_tryget(c, BCH_WRITE_REF_invalidate) &&
+           !queue_work(c->write_ref_wq, &c->invalidate_work))
+               bch2_write_ref_put(c, BCH_WRITE_REF_invalidate);
 }
 
-static int bch2_dev_freespace_init(struct bch_fs *c, struct bch_dev *ca)
+int bch2_dev_freespace_init(struct bch_fs *c, struct bch_dev *ca,
+                           u64 bucket_start, u64 bucket_end)
 {
-       struct btree_trans trans;
+       struct btree_trans *trans = bch2_trans_get(c);
        struct btree_iter iter;
        struct bkey_s_c k;
        struct bkey hole;
-       struct bpos end = POS(ca->dev_idx, ca->mi.nbuckets);
+       struct bpos end = POS(ca->dev_idx, bucket_end);
        struct bch_member *m;
+       unsigned long last_updated = jiffies;
        int ret;
 
-       bch2_trans_init(&trans, c, 0, 0);
+       BUG_ON(bucket_start > bucket_end);
+       BUG_ON(bucket_end > ca->mi.nbuckets);
 
-       bch2_trans_iter_init(&trans, &iter, BTREE_ID_alloc,
-                            POS(ca->dev_idx, ca->mi.first_bucket),
-                            BTREE_ITER_PREFETCH);
+       bch2_trans_iter_init(trans, &iter, BTREE_ID_alloc,
+               POS(ca->dev_idx, max_t(u64, ca->mi.first_bucket, bucket_start)),
+               BTREE_ITER_PREFETCH);
        /*
         * Scan the alloc btree for every bucket on @ca, and add buckets to the
         * freespace/need_discard/need_gc_gens btrees as needed:
         */
        while (1) {
-               bch2_trans_begin(&trans);
+               if (last_updated + HZ * 10 < jiffies) {
+                       bch_info(ca, "%s: currently at %llu/%llu",
+                                __func__, iter.pos.offset, ca->mi.nbuckets);
+                       last_updated = jiffies;
+               }
+
+               bch2_trans_begin(trans);
 
                if (bkey_ge(iter.pos, end)) {
                        ret = 0;
@@ -1520,10 +1954,9 @@ static int bch2_dev_freespace_init(struct bch_fs *c, struct bch_dev *ca)
                        struct bch_alloc_v4 a_convert;
                        const struct bch_alloc_v4 *a = bch2_alloc_to_v4(k, &a_convert);
 
-                       ret =   bch2_bucket_do_index(&trans, k, a, true) ?:
-                               bch2_trans_commit(&trans, NULL, NULL,
-                                                 BTREE_INSERT_LAZY_RW|
-                                                 BTREE_INSERT_NOFAIL);
+                       ret =   bch2_bucket_do_index(trans, k, a, true) ?:
+                               bch2_trans_commit(trans, NULL, NULL,
+                                                 BCH_TRANS_COMMIT_no_enospc);
                        if (ret)
                                goto bkey_err;
 
@@ -1531,7 +1964,7 @@ static int bch2_dev_freespace_init(struct bch_fs *c, struct bch_dev *ca)
                } else {
                        struct bkey_i *freespace;
 
-                       freespace = bch2_trans_kmalloc(&trans, sizeof(*freespace));
+                       freespace = bch2_trans_kmalloc(trans, sizeof(*freespace));
                        ret = PTR_ERR_OR_ZERO(freespace);
                        if (ret)
                                goto bkey_err;
@@ -1541,10 +1974,9 @@ static int bch2_dev_freespace_init(struct bch_fs *c, struct bch_dev *ca)
                        freespace->k.p          = k.k->p;
                        freespace->k.size       = k.k->size;
 
-                       ret = __bch2_btree_insert(&trans, BTREE_ID_freespace, freespace) ?:
-                               bch2_trans_commit(&trans, NULL, NULL,
-                                                 BTREE_INSERT_LAZY_RW|
-                                                 BTREE_INSERT_NOFAIL);
+                       ret = bch2_btree_insert_trans(trans, BTREE_ID_freespace, freespace, 0) ?:
+                               bch2_trans_commit(trans, NULL, NULL,
+                                                 BCH_TRANS_COMMIT_no_enospc);
                        if (ret)
                                goto bkey_err;
 
@@ -1557,16 +1989,16 @@ bkey_err:
                        break;
        }
 
-       bch2_trans_iter_exit(&trans, &iter);
-       bch2_trans_exit(&trans);
+       bch2_trans_iter_exit(trans, &iter);
+       bch2_trans_put(trans);
 
        if (ret < 0) {
-               bch_err(ca, "error initializing free space: %s", bch2_err_str(ret));
+               bch_err_msg(ca, ret, "initializing free space");
                return ret;
        }
 
        mutex_lock(&c->sb_lock);
-       m = bch2_sb_get_members(c->disk_sb.sb)->members + ca->dev_idx;
+       m = bch2_members_v2_get_mut(c->disk_sb.sb, ca->dev_idx);
        SET_BCH_MEMBER_FREESPACE_INITIALIZED(m, true);
        mutex_unlock(&c->sb_lock);
 
@@ -1575,8 +2007,6 @@ bkey_err:
 
 int bch2_fs_freespace_init(struct bch_fs *c)
 {
-       struct bch_dev *ca;
-       unsigned i;
        int ret = 0;
        bool doing_init = false;
 
@@ -1585,7 +2015,7 @@ int bch2_fs_freespace_init(struct bch_fs *c)
         * every mount:
         */
 
-       for_each_member_device(ca, c, i) {
+       for_each_member_device(c, ca) {
                if (ca->mi.freespace_initialized)
                        continue;
 
@@ -1594,9 +2024,10 @@ int bch2_fs_freespace_init(struct bch_fs *c)
                        doing_init = true;
                }
 
-               ret = bch2_dev_freespace_init(c, ca);
+               ret = bch2_dev_freespace_init(c, ca, 0, ca->mi.nbuckets);
                if (ret) {
                        percpu_ref_put(&ca->ref);
+                       bch_err_fn(c, ret);
                        return ret;
                }
        }
@@ -1605,11 +2036,10 @@ int bch2_fs_freespace_init(struct bch_fs *c)
                mutex_lock(&c->sb_lock);
                bch2_write_super(c);
                mutex_unlock(&c->sb_lock);
-
                bch_verbose(c, "done initializing freespace");
        }
 
-       return ret;
+       return 0;
 }
 
 /* Bucket IO clocks: */
@@ -1645,15 +2075,13 @@ out:
 
 void bch2_recalc_capacity(struct bch_fs *c)
 {
-       struct bch_dev *ca;
        u64 capacity = 0, reserved_sectors = 0, gc_reserve;
        unsigned bucket_size_max = 0;
        unsigned long ra_pages = 0;
-       unsigned i;
 
        lockdep_assert_held(&c->state_lock);
 
-       for_each_online_member(ca, c, i) {
+       for_each_online_member(c, ca) {
                struct backing_dev_info *bdi = ca->disk_sb.bdev->bd_disk->bdi;
 
                ra_pages += bdi->ra_pages;
@@ -1661,7 +2089,7 @@ void bch2_recalc_capacity(struct bch_fs *c)
 
        bch2_set_ra_pages(c, ra_pages);
 
-       for_each_rw_member(ca, c, i) {
+       for_each_rw_member(c, ca) {
                u64 dev_reserve = 0;
 
                /*
@@ -1715,6 +2143,15 @@ void bch2_recalc_capacity(struct bch_fs *c)
        closure_wake_up(&c->freelist_wait);
 }
 
+u64 bch2_min_rw_member_capacity(struct bch_fs *c)
+{
+       u64 ret = U64_MAX;
+
+       for_each_rw_member(c, ca)
+               ret = min(ret, ca->mi.nbuckets * ca->mi.bucket_size);
+       return ret;
+}
+
 static bool bch2_dev_has_open_write_point(struct bch_fs *c, struct bch_dev *ca)
 {
        struct open_bucket *ob;
@@ -1748,40 +2185,7 @@ void bch2_dev_allocator_remove(struct bch_fs *c, struct bch_dev *ca)
         */
        bch2_recalc_capacity(c);
 
-       /* Next, close write points that point to this device... */
-       for (i = 0; i < ARRAY_SIZE(c->write_points); i++)
-               bch2_writepoint_stop(c, ca, &c->write_points[i]);
-
-       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);
-
-       mutex_lock(&c->btree_reserve_cache_lock);
-       while (c->btree_reserve_cache_nr) {
-               struct btree_alloc *a =
-                       &c->btree_reserve_cache[--c->btree_reserve_cache_nr];
-
-               bch2_open_buckets_put(c, &a->ob);
-       }
-       mutex_unlock(&c->btree_reserve_cache_lock);
-
-       while (1) {
-               struct open_bucket *ob;
-
-               spin_lock(&c->freelist_lock);
-               if (!ca->open_buckets_partial_nr) {
-                       spin_unlock(&c->freelist_lock);
-                       break;
-               }
-               ob = c->open_buckets +
-                       ca->open_buckets_partial[--ca->open_buckets_partial_nr];
-               ob->on_partial_list = false;
-               spin_unlock(&c->freelist_lock);
-
-               bch2_open_bucket_put(c, ob);
-       }
-
-       bch2_ec_stop_dev(c, ca);
+       bch2_open_buckets_stop(c, ca, false);
 
        /*
         * Wake up threads that were blocked on allocation, so they can notice