]> git.sesse.net Git - bcachefs-tools-debian/blobdiff - libbcachefs/subvolume.c
New upstream release
[bcachefs-tools-debian] / libbcachefs / subvolume.c
index 736afb626a8945b75d4bc3300fb15fb60d594de8..1cbf9e3a09ecf67bbcc59951ce4df45e48f87c1c 100644 (file)
 #include "errcode.h"
 #include "error.h"
 #include "fs.h"
+#include "snapshot.h"
 #include "subvolume.h"
 
 #include <linux/random.h>
 
 static int bch2_subvolume_delete(struct btree_trans *, u32);
 
-static inline u32 get_ancestor_below(struct snapshot_table *t, u32 id, u32 ancestor)
-{
-       const struct snapshot_t *s = __snapshot_t(t, id);
-
-       if (s->skip[2] <= ancestor)
-               return s->skip[2];
-       if (s->skip[1] <= ancestor)
-               return s->skip[1];
-       if (s->skip[0] <= ancestor)
-               return s->skip[0];
-       return s->parent;
-}
-
-bool __bch2_snapshot_is_ancestor(struct bch_fs *c, u32 id, u32 ancestor)
-{
-       struct snapshot_table *t;
-       bool ret;
-
-       EBUG_ON(c->curr_recovery_pass <= BCH_RECOVERY_PASS_check_snapshots);
-
-       rcu_read_lock();
-       t = rcu_dereference(c->snapshots);
-
-       while (id && id < ancestor - IS_ANCESTOR_BITMAP)
-               id = get_ancestor_below(t, id, ancestor);
-
-       ret = id && id < ancestor
-               ? test_bit(ancestor - id - 1, __snapshot_t(t, id)->is_ancestor)
-               : id == ancestor;
-       rcu_read_unlock();
-
-       return ret;
-}
-
-static bool bch2_snapshot_is_ancestor_early(struct bch_fs *c, u32 id, u32 ancestor)
-{
-       struct snapshot_table *t;
-
-       rcu_read_lock();
-       t = rcu_dereference(c->snapshots);
-
-       while (id && id < ancestor)
-               id = __snapshot_t(t, id)->parent;
-       rcu_read_unlock();
-
-       return id == ancestor;
-}
-
-static inline u32 bch2_snapshot_depth(struct bch_fs *c, u32 parent)
-{
-       u32 depth;
-
-       rcu_read_lock();
-       depth = parent ? snapshot_t(c, parent)->depth + 1 : 0;
-       rcu_read_unlock();
-
-       return depth;
-}
-
-static noinline struct snapshot_t *__snapshot_t_mut(struct bch_fs *c, u32 id)
-{
-       size_t idx = U32_MAX - id;
-       size_t new_size;
-       struct snapshot_table *new, *old;
-
-       new_size = max(16UL, roundup_pow_of_two(idx + 1));
-
-       new = kvzalloc(struct_size(new, s, new_size), GFP_KERNEL);
-       if (!new)
-               return NULL;
-
-       old = rcu_dereference_protected(c->snapshots, true);
-       if (old)
-               memcpy(new->s,
-                      rcu_dereference_protected(c->snapshots, true)->s,
-                      sizeof(new->s[0]) * c->snapshot_table_size);
-
-       rcu_assign_pointer(c->snapshots, new);
-       c->snapshot_table_size = new_size;
-       if (old)
-               kvfree_rcu(old);
-
-       return &rcu_dereference_protected(c->snapshots, true)->s[idx];
-}
-
-static inline struct snapshot_t *snapshot_t_mut(struct bch_fs *c, u32 id)
-{
-       size_t idx = U32_MAX - id;
-
-       lockdep_assert_held(&c->snapshot_table_lock);
-
-       if (likely(idx < c->snapshot_table_size))
-               return &rcu_dereference_protected(c->snapshots, true)->s[idx];
-
-       return __snapshot_t_mut(c, id);
-}
-
-/* Snapshot tree: */
-
-void bch2_snapshot_tree_to_text(struct printbuf *out, struct bch_fs *c,
-                               struct bkey_s_c k)
-{
-       struct bkey_s_c_snapshot_tree t = bkey_s_c_to_snapshot_tree(k);
-
-       prt_printf(out, "subvol %u root snapshot %u",
-                  le32_to_cpu(t.v->master_subvol),
-                  le32_to_cpu(t.v->root_snapshot));
-}
-
-int bch2_snapshot_tree_invalid(const struct bch_fs *c, struct bkey_s_c k,
-                              enum bkey_invalid_flags flags,
-                              struct printbuf *err)
-{
-       if (bkey_gt(k.k->p, POS(0, U32_MAX)) ||
-           bkey_lt(k.k->p, POS(0, 1))) {
-               prt_printf(err, "bad pos");
-               return -BCH_ERR_invalid_bkey;
-       }
-
-       return 0;
-}
-
-int bch2_snapshot_tree_lookup(struct btree_trans *trans, u32 id,
-                             struct bch_snapshot_tree *s)
-{
-       int ret = bch2_bkey_get_val_typed(trans, BTREE_ID_snapshot_trees, POS(0, id),
-                                         BTREE_ITER_WITH_UPDATES, snapshot_tree, s);
-
-       if (bch2_err_matches(ret, ENOENT))
-               ret = -BCH_ERR_ENOENT_snapshot_tree;
-       return ret;
-}
-
-static struct bkey_i_snapshot_tree *
-__snapshot_tree_create(struct btree_trans *trans)
-{
-       struct btree_iter iter;
-       int ret = bch2_bkey_get_empty_slot(trans, &iter,
-                       BTREE_ID_snapshot_trees, POS(0, U32_MAX));
-       struct bkey_i_snapshot_tree *s_t;
-
-       if (ret == -BCH_ERR_ENOSPC_btree_slot)
-               ret = -BCH_ERR_ENOSPC_snapshot_tree;
-       if (ret)
-               return ERR_PTR(ret);
-
-       s_t = bch2_bkey_alloc(trans, &iter, 0, snapshot_tree);
-       ret = PTR_ERR_OR_ZERO(s_t);
-       bch2_trans_iter_exit(trans, &iter);
-       return ret ? ERR_PTR(ret) : s_t;
-}
-
-static int snapshot_tree_create(struct btree_trans *trans,
-                               u32 root_id, u32 subvol_id, u32 *tree_id)
-{
-       struct bkey_i_snapshot_tree *n_tree =
-               __snapshot_tree_create(trans);
-
-       if (IS_ERR(n_tree))
-               return PTR_ERR(n_tree);
-
-       n_tree->v.master_subvol = cpu_to_le32(subvol_id);
-       n_tree->v.root_snapshot = cpu_to_le32(root_id);
-       *tree_id = n_tree->k.p.offset;
-       return 0;
-}
-
-/* Snapshot nodes: */
-
-void bch2_snapshot_to_text(struct printbuf *out, struct bch_fs *c,
-                          struct bkey_s_c k)
-{
-       struct bkey_s_c_snapshot s = bkey_s_c_to_snapshot(k);
-
-       prt_printf(out, "is_subvol %llu deleted %llu parent %10u children %10u %10u subvol %u tree %u",
-              BCH_SNAPSHOT_SUBVOL(s.v),
-              BCH_SNAPSHOT_DELETED(s.v),
-              le32_to_cpu(s.v->parent),
-              le32_to_cpu(s.v->children[0]),
-              le32_to_cpu(s.v->children[1]),
-              le32_to_cpu(s.v->subvol),
-              le32_to_cpu(s.v->tree));
-
-       if (bkey_val_bytes(k.k) > offsetof(struct bch_snapshot, depth))
-               prt_printf(out, " depth %u skiplist %u %u %u",
-                          le32_to_cpu(s.v->depth),
-                          le32_to_cpu(s.v->skip[0]),
-                          le32_to_cpu(s.v->skip[1]),
-                          le32_to_cpu(s.v->skip[2]));
-}
-
-int bch2_snapshot_invalid(const struct bch_fs *c, struct bkey_s_c k,
-                         enum bkey_invalid_flags flags,
-                         struct printbuf *err)
-{
-       struct bkey_s_c_snapshot s;
-       u32 i, id;
-
-       if (bkey_gt(k.k->p, POS(0, U32_MAX)) ||
-           bkey_lt(k.k->p, POS(0, 1))) {
-               prt_printf(err, "bad pos");
-               return -BCH_ERR_invalid_bkey;
-       }
-
-       s = bkey_s_c_to_snapshot(k);
-
-       id = le32_to_cpu(s.v->parent);
-       if (id && id <= k.k->p.offset) {
-               prt_printf(err, "bad parent node (%u <= %llu)",
-                      id, k.k->p.offset);
-               return -BCH_ERR_invalid_bkey;
-       }
-
-       if (le32_to_cpu(s.v->children[0]) < le32_to_cpu(s.v->children[1])) {
-               prt_printf(err, "children not normalized");
-               return -BCH_ERR_invalid_bkey;
-       }
-
-       if (s.v->children[0] &&
-           s.v->children[0] == s.v->children[1]) {
-               prt_printf(err, "duplicate child nodes");
-               return -BCH_ERR_invalid_bkey;
-       }
-
-       for (i = 0; i < 2; i++) {
-               id = le32_to_cpu(s.v->children[i]);
-
-               if (id >= k.k->p.offset) {
-                       prt_printf(err, "bad child node (%u >= %llu)",
-                              id, k.k->p.offset);
-                       return -BCH_ERR_invalid_bkey;
-               }
-       }
-
-       if (bkey_val_bytes(k.k) > offsetof(struct bch_snapshot, skip)) {
-               if (le32_to_cpu(s.v->skip[0]) > le32_to_cpu(s.v->skip[1]) ||
-                   le32_to_cpu(s.v->skip[1]) > le32_to_cpu(s.v->skip[2])) {
-                       prt_printf(err, "skiplist not normalized");
-                       return -BCH_ERR_invalid_bkey;
-               }
-
-               for (i = 0; i < ARRAY_SIZE(s.v->skip); i++) {
-                       id = le32_to_cpu(s.v->skip[i]);
-
-                       if (!id != !s.v->parent ||
-                           (s.v->parent &&
-                            id <= k.k->p.offset)) {
-                               prt_printf(err, "bad skiplist node %u)", id);
-                               return -BCH_ERR_invalid_bkey;
-                       }
-               }
-       }
-
-       return 0;
-}
-
-int bch2_mark_snapshot(struct btree_trans *trans,
-                      enum btree_id btree, unsigned level,
-                      struct bkey_s_c old, struct bkey_s_c new,
-                      unsigned flags)
-{
-       struct bch_fs *c = trans->c;
-       struct snapshot_t *t;
-       u32 id = new.k->p.offset;
-       int ret = 0;
-
-       mutex_lock(&c->snapshot_table_lock);
-
-       t = snapshot_t_mut(c, id);
-       if (!t) {
-               ret = -BCH_ERR_ENOMEM_mark_snapshot;
-               goto err;
-       }
-
-       if (new.k->type == KEY_TYPE_snapshot) {
-               struct bkey_s_c_snapshot s = bkey_s_c_to_snapshot(new);
-               u32 parent = id;
-
-               t->parent       = le32_to_cpu(s.v->parent);
-               t->children[0]  = le32_to_cpu(s.v->children[0]);
-               t->children[1]  = le32_to_cpu(s.v->children[1]);
-               t->subvol       = BCH_SNAPSHOT_SUBVOL(s.v) ? le32_to_cpu(s.v->subvol) : 0;
-               t->tree         = le32_to_cpu(s.v->tree);
-
-               if (bkey_val_bytes(s.k) > offsetof(struct bch_snapshot, depth)) {
-                       t->depth        = le32_to_cpu(s.v->depth);
-                       t->skip[0]      = le32_to_cpu(s.v->skip[0]);
-                       t->skip[1]      = le32_to_cpu(s.v->skip[1]);
-                       t->skip[2]      = le32_to_cpu(s.v->skip[2]);
-               } else {
-                       t->depth        = 0;
-                       t->skip[0]      = 0;
-                       t->skip[1]      = 0;
-                       t->skip[2]      = 0;
-               }
-
-               while ((parent = bch2_snapshot_parent_early(c, parent)) &&
-                      parent - id - 1 < IS_ANCESTOR_BITMAP)
-                       __set_bit(parent - id - 1, t->is_ancestor);
-
-               if (BCH_SNAPSHOT_DELETED(s.v)) {
-                       set_bit(BCH_FS_HAVE_DELETED_SNAPSHOTS, &c->flags);
-                       c->recovery_passes_explicit |= BIT_ULL(BCH_RECOVERY_PASS_delete_dead_snapshots);
-               }
-       } else {
-               memset(t, 0, sizeof(*t));
-       }
-err:
-       mutex_unlock(&c->snapshot_table_lock);
-       return ret;
-}
-
-static int snapshot_lookup(struct btree_trans *trans, u32 id,
-                          struct bch_snapshot *s)
-{
-       return bch2_bkey_get_val_typed(trans, BTREE_ID_snapshots, POS(0, id),
-                                      BTREE_ITER_WITH_UPDATES, snapshot, s);
-}
-
-static int snapshot_live(struct btree_trans *trans, u32 id)
-{
-       struct bch_snapshot v;
-       int ret;
-
-       if (!id)
-               return 0;
-
-       ret = snapshot_lookup(trans, id, &v);
-       if (bch2_err_matches(ret, ENOENT))
-               bch_err(trans->c, "snapshot node %u not found", id);
-       if (ret)
-               return ret;
-
-       return !BCH_SNAPSHOT_DELETED(&v);
-}
-
-static int bch2_snapshot_set_equiv(struct btree_trans *trans, struct bkey_s_c k)
-{
-       struct bch_fs *c = trans->c;
-       unsigned i, nr_live = 0, live_idx = 0;
-       struct bkey_s_c_snapshot snap;
-       u32 id = k.k->p.offset, child[2];
-
-       if (k.k->type != KEY_TYPE_snapshot)
-               return 0;
-
-       snap = bkey_s_c_to_snapshot(k);
-
-       child[0] = le32_to_cpu(snap.v->children[0]);
-       child[1] = le32_to_cpu(snap.v->children[1]);
-
-       for (i = 0; i < 2; i++) {
-               int ret = snapshot_live(trans, child[i]);
-
-               if (ret < 0)
-                       return ret;
-
-               if (ret)
-                       live_idx = i;
-               nr_live += ret;
-       }
-
-       mutex_lock(&c->snapshot_table_lock);
-
-       snapshot_t_mut(c, id)->equiv = nr_live == 1
-               ? snapshot_t_mut(c, child[live_idx])->equiv
-               : id;
-
-       mutex_unlock(&c->snapshot_table_lock);
-
-       return 0;
-}
-
-/* fsck: */
-
-static u32 bch2_snapshot_child(struct bch_fs *c, u32 id, unsigned child)
-{
-       return snapshot_t(c, id)->children[child];
-}
-
-static u32 bch2_snapshot_left_child(struct bch_fs *c, u32 id)
-{
-       return bch2_snapshot_child(c, id, 0);
-}
-
-static u32 bch2_snapshot_right_child(struct bch_fs *c, u32 id)
-{
-       return bch2_snapshot_child(c, id, 1);
-}
-
-static u32 bch2_snapshot_tree_next(struct bch_fs *c, u32 id)
-{
-       u32 n, parent;
-
-       n = bch2_snapshot_left_child(c, id);
-       if (n)
-               return n;
-
-       while ((parent = bch2_snapshot_parent(c, id))) {
-               n = bch2_snapshot_right_child(c, parent);
-               if (n && n != id)
-                       return n;
-               id = parent;
-       }
-
-       return 0;
-}
-
-static u32 bch2_snapshot_tree_oldest_subvol(struct bch_fs *c, u32 snapshot_root)
-{
-       u32 id = snapshot_root;
-       u32 subvol = 0, s;
-
-       while (id) {
-               s = snapshot_t(c, id)->subvol;
-
-               if (s && (!subvol || s < subvol))
-                       subvol = s;
-
-               id = bch2_snapshot_tree_next(c, id);
-       }
-
-       return subvol;
-}
-
-static int bch2_snapshot_tree_master_subvol(struct btree_trans *trans,
-                                           u32 snapshot_root, u32 *subvol_id)
-{
-       struct bch_fs *c = trans->c;
-       struct btree_iter iter;
-       struct bkey_s_c k;
-       struct bkey_s_c_subvolume s;
-       bool found = false;
-       int ret;
-
-       for_each_btree_key_norestart(trans, iter, BTREE_ID_subvolumes, POS_MIN,
-                                    0, k, ret) {
-               if (k.k->type != KEY_TYPE_subvolume)
-                       continue;
-
-               s = bkey_s_c_to_subvolume(k);
-               if (!bch2_snapshot_is_ancestor(c, le32_to_cpu(s.v->snapshot), snapshot_root))
-                       continue;
-               if (!BCH_SUBVOLUME_SNAP(s.v)) {
-                       *subvol_id = s.k->p.offset;
-                       found = true;
-                       break;
-               }
-       }
-
-       bch2_trans_iter_exit(trans, &iter);
-
-       if (!ret && !found) {
-               struct bkey_i_subvolume *s;
-
-               *subvol_id = bch2_snapshot_tree_oldest_subvol(c, snapshot_root);
-
-               s = bch2_bkey_get_mut_typed(trans, &iter,
-                                           BTREE_ID_subvolumes, POS(0, *subvol_id),
-                                           0, subvolume);
-               ret = PTR_ERR_OR_ZERO(s);
-               if (ret)
-                       return ret;
-
-               SET_BCH_SUBVOLUME_SNAP(&s->v, false);
-       }
-
-       return ret;
-}
-
-static int check_snapshot_tree(struct btree_trans *trans,
-                              struct btree_iter *iter,
-                              struct bkey_s_c k)
-{
-       struct bch_fs *c = trans->c;
-       struct bkey_s_c_snapshot_tree st;
-       struct bch_snapshot s;
-       struct bch_subvolume subvol;
-       struct printbuf buf = PRINTBUF;
-       u32 root_id;
-       int ret;
-
-       if (k.k->type != KEY_TYPE_snapshot_tree)
-               return 0;
-
-       st = bkey_s_c_to_snapshot_tree(k);
-       root_id = le32_to_cpu(st.v->root_snapshot);
-
-       ret = snapshot_lookup(trans, root_id, &s);
-       if (ret && !bch2_err_matches(ret, ENOENT))
-               goto err;
-
-       if (fsck_err_on(ret ||
-                       root_id != bch2_snapshot_root(c, root_id) ||
-                       st.k->p.offset != le32_to_cpu(s.tree),
-                       c,
-                       "snapshot tree points to missing/incorrect snapshot:\n  %s",
-                       (bch2_bkey_val_to_text(&buf, c, st.s_c), buf.buf))) {
-               ret = bch2_btree_delete_at(trans, iter, 0);
-               goto err;
-       }
-
-       ret = bch2_subvolume_get(trans, le32_to_cpu(st.v->master_subvol),
-                                false, 0, &subvol);
-       if (ret && !bch2_err_matches(ret, ENOENT))
-               goto err;
-
-       if (fsck_err_on(ret, c,
-                       "snapshot tree points to missing subvolume:\n  %s",
-                       (printbuf_reset(&buf),
-                        bch2_bkey_val_to_text(&buf, c, st.s_c), buf.buf)) ||
-           fsck_err_on(!bch2_snapshot_is_ancestor_early(c,
-                                               le32_to_cpu(subvol.snapshot),
-                                               root_id), c,
-                       "snapshot tree points to subvolume that does not point to snapshot in this tree:\n  %s",
-                       (printbuf_reset(&buf),
-                        bch2_bkey_val_to_text(&buf, c, st.s_c), buf.buf)) ||
-           fsck_err_on(BCH_SUBVOLUME_SNAP(&subvol), c,
-                       "snapshot tree points to snapshot subvolume:\n  %s",
-                       (printbuf_reset(&buf),
-                        bch2_bkey_val_to_text(&buf, c, st.s_c), buf.buf))) {
-               struct bkey_i_snapshot_tree *u;
-               u32 subvol_id;
-
-               ret = bch2_snapshot_tree_master_subvol(trans, root_id, &subvol_id);
-               if (ret)
-                       goto err;
-
-               u = bch2_bkey_make_mut_typed(trans, iter, &k, 0, snapshot_tree);
-               ret = PTR_ERR_OR_ZERO(u);
-               if (ret)
-                       goto err;
-
-               u->v.master_subvol = cpu_to_le32(subvol_id);
-               st = snapshot_tree_i_to_s_c(u);
-       }
-err:
-fsck_err:
-       printbuf_exit(&buf);
-       return ret;
-}
-
-/*
- * For each snapshot_tree, make sure it points to the root of a snapshot tree
- * and that snapshot entry points back to it, or delete it.
- *
- * And, make sure it points to a subvolume within that snapshot tree, or correct
- * it to point to the oldest subvolume within that snapshot tree.
- */
-int bch2_check_snapshot_trees(struct bch_fs *c)
-{
-       struct btree_iter iter;
-       struct bkey_s_c k;
-       int ret;
-
-       ret = bch2_trans_run(c,
-               for_each_btree_key_commit(&trans, iter,
-                       BTREE_ID_snapshot_trees, POS_MIN,
-                       BTREE_ITER_PREFETCH, k,
-                       NULL, NULL, BTREE_INSERT_LAZY_RW|BTREE_INSERT_NOFAIL,
-               check_snapshot_tree(&trans, &iter, k)));
-
-       if (ret)
-               bch_err(c, "error %i checking snapshot trees", ret);
-       return ret;
-}
-
-/*
- * Look up snapshot tree for @tree_id and find root,
- * make sure @snap_id is a descendent:
- */
-static int snapshot_tree_ptr_good(struct btree_trans *trans,
-                                 u32 snap_id, u32 tree_id)
-{
-       struct bch_snapshot_tree s_t;
-       int ret = bch2_snapshot_tree_lookup(trans, tree_id, &s_t);
-
-       if (bch2_err_matches(ret, ENOENT))
-               return 0;
-       if (ret)
-               return ret;
-
-       return bch2_snapshot_is_ancestor_early(trans->c, snap_id, le32_to_cpu(s_t.root_snapshot));
-}
-
-static u32 snapshot_skiplist_get(struct bch_fs *c, u32 id)
-{
-       const struct snapshot_t *s;
-
-       if (!id)
-               return 0;
-
-       rcu_read_lock();
-       s = snapshot_t(c, id);
-       if (s->parent)
-               id = bch2_snapshot_nth_parent(c, id, get_random_u32_below(s->depth));
-       rcu_read_unlock();
-
-       return id;
-}
-
-static int snapshot_skiplist_good(struct btree_trans *trans, struct bch_snapshot s)
-{
-       struct bch_snapshot a;
-       unsigned i;
-       int ret;
-
-       for (i = 0; i < 3; i++) {
-               if (!s.parent != !s.skip[i])
-                       return false;
-
-               if (!s.parent)
-                       continue;
-
-               ret = snapshot_lookup(trans, le32_to_cpu(s.skip[i]), &a);
-               if (bch2_err_matches(ret, ENOENT))
-                       return false;
-               if (ret)
-                       return ret;
-
-               if (a.tree != s.tree)
-                       return false;
-       }
-
-       return true;
-}
-
-/*
- * snapshot_tree pointer was incorrect: look up root snapshot node, make sure
- * its snapshot_tree pointer is correct (allocate new one if necessary), then
- * update this node's pointer to root node's pointer:
- */
-static int snapshot_tree_ptr_repair(struct btree_trans *trans,
-                                   struct btree_iter *iter,
-                                   struct bkey_s_c k,
-                                   struct bch_snapshot *s)
-{
-       struct bch_fs *c = trans->c;
-       struct btree_iter root_iter;
-       struct bch_snapshot_tree s_t;
-       struct bkey_s_c_snapshot root;
-       struct bkey_i_snapshot *u;
-       u32 root_id = bch2_snapshot_root(c, k.k->p.offset), tree_id;
-       int ret;
-
-       root = bch2_bkey_get_iter_typed(trans, &root_iter,
-                              BTREE_ID_snapshots, POS(0, root_id),
-                              BTREE_ITER_WITH_UPDATES, snapshot);
-       ret = bkey_err(root);
-       if (ret)
-               goto err;
-
-       tree_id = le32_to_cpu(root.v->tree);
-
-       ret = bch2_snapshot_tree_lookup(trans, tree_id, &s_t);
-       if (ret && !bch2_err_matches(ret, ENOENT))
-               return ret;
-
-       if (ret || le32_to_cpu(s_t.root_snapshot) != root_id) {
-               u = bch2_bkey_make_mut_typed(trans, &root_iter, &root.s_c, 0, snapshot);
-               ret =   PTR_ERR_OR_ZERO(u) ?:
-                       snapshot_tree_create(trans, root_id,
-                               bch2_snapshot_tree_oldest_subvol(c, root_id),
-                               &tree_id);
-               if (ret)
-                       goto err;
-
-               u->v.tree = cpu_to_le32(tree_id);
-               if (k.k->p.offset == root_id)
-                       *s = u->v;
-       }
-
-       if (k.k->p.offset != root_id) {
-               u = bch2_bkey_make_mut_typed(trans, iter, &k, 0, snapshot);
-               ret = PTR_ERR_OR_ZERO(u);
-               if (ret)
-                       goto err;
-
-               u->v.tree = cpu_to_le32(tree_id);
-               *s = u->v;
-       }
-err:
-       bch2_trans_iter_exit(trans, &root_iter);
-       return ret;
-}
-
-static int cmp_le32(__le32 l, __le32 r)
-{
-       return cmp_int(le32_to_cpu(l), le32_to_cpu(r));
-}
-
-static int check_snapshot(struct btree_trans *trans,
-                         struct btree_iter *iter,
-                         struct bkey_s_c k)
-{
-       struct bch_fs *c = trans->c;
-       struct bch_snapshot s;
-       struct bch_subvolume subvol;
-       struct bch_snapshot v;
-       struct bkey_i_snapshot *u;
-       u32 parent_id = bch2_snapshot_parent_early(c, k.k->p.offset);
-       u32 real_depth;
-       struct printbuf buf = PRINTBUF;
-       bool should_have_subvol;
-       u32 i, id;
-       int ret = 0;
-
-       if (k.k->type != KEY_TYPE_snapshot)
-               return 0;
-
-       memset(&s, 0, sizeof(s));
-       memcpy(&s, k.v, bkey_val_bytes(k.k));
-
-       id = le32_to_cpu(s.parent);
-       if (id) {
-               ret = snapshot_lookup(trans, id, &v);
-               if (bch2_err_matches(ret, ENOENT))
-                       bch_err(c, "snapshot with nonexistent parent:\n  %s",
-                               (bch2_bkey_val_to_text(&buf, c, k), buf.buf));
-               if (ret)
-                       goto err;
-
-               if (le32_to_cpu(v.children[0]) != k.k->p.offset &&
-                   le32_to_cpu(v.children[1]) != k.k->p.offset) {
-                       bch_err(c, "snapshot parent %u missing pointer to child %llu",
-                               id, k.k->p.offset);
-                       ret = -EINVAL;
-                       goto err;
-               }
-       }
-
-       for (i = 0; i < 2 && s.children[i]; i++) {
-               id = le32_to_cpu(s.children[i]);
-
-               ret = snapshot_lookup(trans, id, &v);
-               if (bch2_err_matches(ret, ENOENT))
-                       bch_err(c, "snapshot node %llu has nonexistent child %u",
-                               k.k->p.offset, id);
-               if (ret)
-                       goto err;
-
-               if (le32_to_cpu(v.parent) != k.k->p.offset) {
-                       bch_err(c, "snapshot child %u has wrong parent (got %u should be %llu)",
-                               id, le32_to_cpu(v.parent), k.k->p.offset);
-                       ret = -EINVAL;
-                       goto err;
-               }
-       }
-
-       should_have_subvol = BCH_SNAPSHOT_SUBVOL(&s) &&
-               !BCH_SNAPSHOT_DELETED(&s);
-
-       if (should_have_subvol) {
-               id = le32_to_cpu(s.subvol);
-               ret = bch2_subvolume_get(trans, id, 0, false, &subvol);
-               if (bch2_err_matches(ret, ENOENT))
-                       bch_err(c, "snapshot points to nonexistent subvolume:\n  %s",
-                               (bch2_bkey_val_to_text(&buf, c, k), buf.buf));
-               if (ret)
-                       goto err;
-
-               if (BCH_SNAPSHOT_SUBVOL(&s) != (le32_to_cpu(subvol.snapshot) == k.k->p.offset)) {
-                       bch_err(c, "snapshot node %llu has wrong BCH_SNAPSHOT_SUBVOL",
-                               k.k->p.offset);
-                       ret = -EINVAL;
-                       goto err;
-               }
-       } else {
-               if (fsck_err_on(s.subvol, c, "snapshot should not point to subvol:\n  %s",
-                               (bch2_bkey_val_to_text(&buf, c, k), buf.buf))) {
-                       u = bch2_bkey_make_mut_typed(trans, iter, &k, 0, snapshot);
-                       ret = PTR_ERR_OR_ZERO(u);
-                       if (ret)
-                               goto err;
-
-                       u->v.subvol = 0;
-                       s = u->v;
-               }
-       }
-
-       ret = snapshot_tree_ptr_good(trans, k.k->p.offset, le32_to_cpu(s.tree));
-       if (ret < 0)
-               goto err;
-
-       if (fsck_err_on(!ret, c, "snapshot points to missing/incorrect tree:\n  %s",
-                       (bch2_bkey_val_to_text(&buf, c, k), buf.buf))) {
-               ret = snapshot_tree_ptr_repair(trans, iter, k, &s);
-               if (ret)
-                       goto err;
-       }
-       ret = 0;
-
-       real_depth = bch2_snapshot_depth(c, parent_id);
-
-       if (le32_to_cpu(s.depth) != real_depth &&
-           (c->sb.version_upgrade_complete < bcachefs_metadata_version_snapshot_skiplists ||
-            fsck_err(c, "snapshot with incorrect depth field, should be %u:\n  %s",
-                     real_depth, (bch2_bkey_val_to_text(&buf, c, k), buf.buf)))) {
-               u = bch2_bkey_make_mut_typed(trans, iter, &k, 0, snapshot);
-               ret = PTR_ERR_OR_ZERO(u);
-               if (ret)
-                       goto err;
-
-               u->v.depth = cpu_to_le32(real_depth);
-               s = u->v;
-       }
-
-       ret = snapshot_skiplist_good(trans, s);
-       if (ret < 0)
-               goto err;
-
-       if (!ret &&
-           (c->sb.version_upgrade_complete < bcachefs_metadata_version_snapshot_skiplists ||
-            fsck_err(c, "snapshot with bad skiplist field:\n  %s",
-                     (bch2_bkey_val_to_text(&buf, c, k), buf.buf)))) {
-               u = bch2_bkey_make_mut_typed(trans, iter, &k, 0, snapshot);
-               ret = PTR_ERR_OR_ZERO(u);
-               if (ret)
-                       goto err;
-
-               for (i = 0; i < ARRAY_SIZE(u->v.skip); i++)
-                       u->v.skip[i] = cpu_to_le32(snapshot_skiplist_get(c, parent_id));
-
-               bubble_sort(u->v.skip, ARRAY_SIZE(u->v.skip), cmp_le32);
-               s = u->v;
-       }
-       ret = 0;
-err:
-fsck_err:
-       printbuf_exit(&buf);
-       return ret;
-}
-
-int bch2_check_snapshots(struct bch_fs *c)
-{
-       struct btree_iter iter;
-       struct bkey_s_c k;
-       int ret;
-
-       /*
-        * We iterate backwards as checking/fixing the depth field requires that
-        * the parent's depth already be correct:
-        */
-       ret = bch2_trans_run(c,
-               for_each_btree_key_reverse_commit(&trans, iter,
-                       BTREE_ID_snapshots, POS_MAX,
-                       BTREE_ITER_PREFETCH, k,
-                       NULL, NULL, BTREE_INSERT_LAZY_RW|BTREE_INSERT_NOFAIL,
-               check_snapshot(&trans, &iter, k)));
-       if (ret)
-               bch_err_fn(c, ret);
-       return ret;
-}
-
 static int check_subvol(struct btree_trans *trans,
                        struct btree_iter *iter,
                        struct bkey_s_c k)
@@ -881,7 +28,7 @@ static int check_subvol(struct btree_trans *trans,
 
        subvol = bkey_s_c_to_subvolume(k);
        snapid = le32_to_cpu(subvol.v->snapshot);
-       ret = snapshot_lookup(trans, snapid, &snapshot);
+       ret = bch2_snapshot_lookup(trans, snapid, &snapshot);
 
        if (bch2_err_matches(ret, ENOENT))
                bch_err(c, "subvolume %llu points to nonexistent snapshot %u",
@@ -894,8 +41,7 @@ static int check_subvol(struct btree_trans *trans,
 
                ret = bch2_subvolume_delete(trans, iter->pos.offset);
                if (ret)
-                       bch_err(c, "error deleting subvolume %llu: %s",
-                               iter->pos.offset, bch2_err_str(ret));
+                       bch_err_msg(c, ret, "deleting subvolume %llu", iter->pos.offset);
                return ret ?: -BCH_ERR_transaction_restart_nested;
        }
 
@@ -916,7 +62,8 @@ static int check_subvol(struct btree_trans *trans,
                if (ret)
                        return ret;
 
-               if (fsck_err_on(le32_to_cpu(st.master_subvol) != subvol.k->p.offset, c,
+               if (fsck_err_on(le32_to_cpu(st.master_subvol) != subvol.k->p.offset,
+                               c, subvol_not_master_and_not_snapshot,
                                "subvolume %llu is not set as snapshot but is not master subvolume",
                                k.k->p.offset)) {
                        struct bkey_i_subvolume *s =
@@ -940,485 +87,30 @@ int bch2_check_subvols(struct bch_fs *c)
        int ret;
 
        ret = bch2_trans_run(c,
-               for_each_btree_key_commit(&trans, iter,
+               for_each_btree_key_commit(trans, iter,
                        BTREE_ID_subvolumes, POS_MIN, BTREE_ITER_PREFETCH, k,
-                       NULL, NULL, BTREE_INSERT_LAZY_RW|BTREE_INSERT_NOFAIL,
-               check_subvol(&trans, &iter, k)));
-       if (ret)
-               bch_err_fn(c, ret);
-       return ret;
-}
-
-void bch2_fs_snapshots_exit(struct bch_fs *c)
-{
-       kfree(rcu_dereference_protected(c->snapshots, true));
-}
-
-int bch2_snapshots_read(struct bch_fs *c)
-{
-       struct btree_iter iter;
-       struct bkey_s_c k;
-       int ret = 0;
-
-       ret = bch2_trans_run(c,
-               for_each_btree_key2(&trans, iter, BTREE_ID_snapshots,
-                          POS_MIN, 0, k,
-                       bch2_mark_snapshot(&trans, BTREE_ID_snapshots, 0, bkey_s_c_null, k, 0) ?:
-                       bch2_snapshot_set_equiv(&trans, k)));
+                       NULL, NULL, BCH_TRANS_COMMIT_lazy_rw|BCH_TRANS_COMMIT_no_enospc,
+               check_subvol(trans, &iter, k)));
        if (ret)
                bch_err_fn(c, ret);
        return ret;
 }
 
-/*
- * Mark a snapshot as deleted, for future cleanup:
- */
-static int bch2_snapshot_node_set_deleted(struct btree_trans *trans, u32 id)
-{
-       struct btree_iter iter;
-       struct bkey_i_snapshot *s;
-       int ret = 0;
-
-       s = bch2_bkey_get_mut_typed(trans, &iter,
-                                   BTREE_ID_snapshots, POS(0, id),
-                                   0, snapshot);
-       ret = PTR_ERR_OR_ZERO(s);
-       if (unlikely(ret)) {
-               bch2_fs_inconsistent_on(bch2_err_matches(ret, ENOENT),
-                                       trans->c, "missing snapshot %u", id);
-               return ret;
-       }
-
-       /* already deleted? */
-       if (BCH_SNAPSHOT_DELETED(&s->v))
-               goto err;
-
-       SET_BCH_SNAPSHOT_DELETED(&s->v, true);
-       SET_BCH_SNAPSHOT_SUBVOL(&s->v, false);
-       s->v.subvol = 0;
-err:
-       bch2_trans_iter_exit(trans, &iter);
-       return ret;
-}
-
-static int bch2_snapshot_node_delete(struct btree_trans *trans, u32 id)
-{
-       struct bch_fs *c = trans->c;
-       struct btree_iter iter, p_iter = (struct btree_iter) { NULL };
-       struct btree_iter tree_iter = (struct btree_iter) { NULL };
-       struct bkey_s_c_snapshot s;
-       u32 parent_id;
-       unsigned i;
-       int ret = 0;
-
-       s = bch2_bkey_get_iter_typed(trans, &iter, BTREE_ID_snapshots, POS(0, id),
-                                    BTREE_ITER_INTENT, snapshot);
-       ret = bkey_err(s);
-       bch2_fs_inconsistent_on(bch2_err_matches(ret, ENOENT), c,
-                               "missing snapshot %u", id);
-
-       if (ret)
-               goto err;
-
-       BUG_ON(!BCH_SNAPSHOT_DELETED(s.v));
-       parent_id = le32_to_cpu(s.v->parent);
-
-       if (parent_id) {
-               struct bkey_i_snapshot *parent;
-
-               parent = bch2_bkey_get_mut_typed(trans, &p_iter,
-                                    BTREE_ID_snapshots, POS(0, parent_id),
-                                    0, snapshot);
-               ret = PTR_ERR_OR_ZERO(parent);
-               if (unlikely(ret)) {
-                       bch2_fs_inconsistent_on(bch2_err_matches(ret, ENOENT), c,
-                                               "missing snapshot %u", parent_id);
-                       goto err;
-               }
-
-               for (i = 0; i < 2; i++)
-                       if (le32_to_cpu(parent->v.children[i]) == id)
-                               break;
-
-               if (i == 2)
-                       bch_err(c, "snapshot %u missing child pointer to %u",
-                               parent_id, id);
-               else
-                       parent->v.children[i] = 0;
-
-               if (le32_to_cpu(parent->v.children[0]) <
-                   le32_to_cpu(parent->v.children[1]))
-                       swap(parent->v.children[0],
-                            parent->v.children[1]);
-       } else {
-               /*
-                * We're deleting the root of a snapshot tree: update the
-                * snapshot_tree entry to point to the new root, or delete it if
-                * this is the last snapshot ID in this tree:
-                */
-               struct bkey_i_snapshot_tree *s_t;
-
-               BUG_ON(s.v->children[1]);
-
-               s_t = bch2_bkey_get_mut_typed(trans, &tree_iter,
-                               BTREE_ID_snapshot_trees, POS(0, le32_to_cpu(s.v->tree)),
-                               0, snapshot_tree);
-               ret = PTR_ERR_OR_ZERO(s_t);
-               if (ret)
-                       goto err;
-
-               if (s.v->children[0]) {
-                       s_t->v.root_snapshot = s.v->children[0];
-               } else {
-                       s_t->k.type = KEY_TYPE_deleted;
-                       set_bkey_val_u64s(&s_t->k, 0);
-               }
-       }
-
-       ret = bch2_btree_delete_at(trans, &iter, 0);
-err:
-       bch2_trans_iter_exit(trans, &tree_iter);
-       bch2_trans_iter_exit(trans, &p_iter);
-       bch2_trans_iter_exit(trans, &iter);
-       return ret;
-}
-
-static int create_snapids(struct btree_trans *trans, u32 parent, u32 tree,
-                         u32 *new_snapids,
-                         u32 *snapshot_subvols,
-                         unsigned nr_snapids)
-{
-       struct bch_fs *c = trans->c;
-       struct btree_iter iter;
-       struct bkey_i_snapshot *n;
-       struct bkey_s_c k;
-       unsigned i, j;
-       u32 depth = bch2_snapshot_depth(c, parent);
-       int ret;
-
-       bch2_trans_iter_init(trans, &iter, BTREE_ID_snapshots,
-                            POS_MIN, BTREE_ITER_INTENT);
-       k = bch2_btree_iter_peek(&iter);
-       ret = bkey_err(k);
-       if (ret)
-               goto err;
-
-       for (i = 0; i < nr_snapids; i++) {
-               k = bch2_btree_iter_prev_slot(&iter);
-               ret = bkey_err(k);
-               if (ret)
-                       goto err;
-
-               if (!k.k || !k.k->p.offset) {
-                       ret = -BCH_ERR_ENOSPC_snapshot_create;
-                       goto err;
-               }
-
-               n = bch2_bkey_alloc(trans, &iter, 0, snapshot);
-               ret = PTR_ERR_OR_ZERO(n);
-               if (ret)
-                       goto err;
-
-               n->v.flags      = 0;
-               n->v.parent     = cpu_to_le32(parent);
-               n->v.subvol     = cpu_to_le32(snapshot_subvols[i]);
-               n->v.tree       = cpu_to_le32(tree);
-               n->v.depth      = cpu_to_le32(depth);
-
-               for (j = 0; j < ARRAY_SIZE(n->v.skip); j++)
-                       n->v.skip[j] = cpu_to_le32(snapshot_skiplist_get(c, parent));
-
-               bubble_sort(n->v.skip, ARRAY_SIZE(n->v.skip), cmp_le32);
-               SET_BCH_SNAPSHOT_SUBVOL(&n->v, true);
-
-               ret = bch2_mark_snapshot(trans, BTREE_ID_snapshots, 0,
-                                        bkey_s_c_null, bkey_i_to_s_c(&n->k_i), 0);
-               if (ret)
-                       goto err;
-
-               new_snapids[i]  = iter.pos.offset;
-       }
-err:
-       bch2_trans_iter_exit(trans, &iter);
-       return ret;
-}
-
-/*
- * Create new snapshot IDs as children of an existing snapshot ID:
- */
-static int bch2_snapshot_node_create_children(struct btree_trans *trans, u32 parent,
-                             u32 *new_snapids,
-                             u32 *snapshot_subvols,
-                             unsigned nr_snapids)
-{
-       struct btree_iter iter;
-       struct bkey_i_snapshot *n_parent;
-       int ret = 0;
-
-       n_parent = bch2_bkey_get_mut_typed(trans, &iter,
-                       BTREE_ID_snapshots, POS(0, parent),
-                       0, snapshot);
-       ret = PTR_ERR_OR_ZERO(n_parent);
-       if (unlikely(ret)) {
-               if (bch2_err_matches(ret, ENOENT))
-                       bch_err(trans->c, "snapshot %u not found", parent);
-               return ret;
-       }
-
-       if (n_parent->v.children[0] || n_parent->v.children[1]) {
-               bch_err(trans->c, "Trying to add child snapshot nodes to parent that already has children");
-               ret = -EINVAL;
-               goto err;
-       }
-
-       ret = create_snapids(trans, parent, le32_to_cpu(n_parent->v.tree),
-                            new_snapids, snapshot_subvols, nr_snapids);
-       if (ret)
-               goto err;
-
-       n_parent->v.children[0] = cpu_to_le32(new_snapids[0]);
-       n_parent->v.children[1] = cpu_to_le32(new_snapids[1]);
-       n_parent->v.subvol = 0;
-       SET_BCH_SNAPSHOT_SUBVOL(&n_parent->v, false);
-err:
-       bch2_trans_iter_exit(trans, &iter);
-       return ret;
-}
-
-/*
- * Create a snapshot node that is the root of a new tree:
- */
-static int bch2_snapshot_node_create_tree(struct btree_trans *trans,
-                             u32 *new_snapids,
-                             u32 *snapshot_subvols,
-                             unsigned nr_snapids)
-{
-       struct bkey_i_snapshot_tree *n_tree;
-       int ret;
-
-       n_tree = __snapshot_tree_create(trans);
-       ret =   PTR_ERR_OR_ZERO(n_tree) ?:
-               create_snapids(trans, 0, n_tree->k.p.offset,
-                            new_snapids, snapshot_subvols, nr_snapids);
-       if (ret)
-               return ret;
-
-       n_tree->v.master_subvol = cpu_to_le32(snapshot_subvols[0]);
-       n_tree->v.root_snapshot = cpu_to_le32(new_snapids[0]);
-       return 0;
-}
-
-int bch2_snapshot_node_create(struct btree_trans *trans, u32 parent,
-                             u32 *new_snapids,
-                             u32 *snapshot_subvols,
-                             unsigned nr_snapids)
-{
-       BUG_ON((parent == 0) != (nr_snapids == 1));
-       BUG_ON((parent != 0) != (nr_snapids == 2));
-
-       return parent
-               ? bch2_snapshot_node_create_children(trans, parent,
-                               new_snapids, snapshot_subvols, nr_snapids)
-               : bch2_snapshot_node_create_tree(trans,
-                               new_snapids, snapshot_subvols, nr_snapids);
-
-}
-
-static int snapshot_delete_key(struct btree_trans *trans,
-                              struct btree_iter *iter,
-                              struct bkey_s_c k,
-                              snapshot_id_list *deleted,
-                              snapshot_id_list *equiv_seen,
-                              struct bpos *last_pos)
-{
-       struct bch_fs *c = trans->c;
-       u32 equiv = bch2_snapshot_equiv(c, k.k->p.snapshot);
-
-       if (!bkey_eq(k.k->p, *last_pos))
-               equiv_seen->nr = 0;
-       *last_pos = k.k->p;
-
-       if (snapshot_list_has_id(deleted, k.k->p.snapshot) ||
-           snapshot_list_has_id(equiv_seen, equiv)) {
-               return bch2_btree_delete_at(trans, iter,
-                                           BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE);
-       } else {
-               return snapshot_list_add(c, equiv_seen, equiv);
-       }
-}
-
-static int bch2_delete_redundant_snapshot(struct btree_trans *trans, struct btree_iter *iter,
-                                         struct bkey_s_c k)
-{
-       struct bkey_s_c_snapshot snap;
-       u32 children[2];
-       int ret;
-
-       if (k.k->type != KEY_TYPE_snapshot)
-               return 0;
-
-       snap = bkey_s_c_to_snapshot(k);
-       if (BCH_SNAPSHOT_DELETED(snap.v) ||
-           BCH_SNAPSHOT_SUBVOL(snap.v))
-               return 0;
-
-       children[0] = le32_to_cpu(snap.v->children[0]);
-       children[1] = le32_to_cpu(snap.v->children[1]);
-
-       ret   = snapshot_live(trans, children[0]) ?:
-               snapshot_live(trans, children[1]);
-       if (ret < 0)
-               return ret;
-
-       if (!ret)
-               return bch2_snapshot_node_set_deleted(trans, k.k->p.offset);
-       return 0;
-}
+/* Subvolumes: */
 
-int bch2_delete_dead_snapshots(struct bch_fs *c)
+int bch2_subvolume_invalid(struct bch_fs *c, struct bkey_s_c k,
+                          enum bkey_invalid_flags flags, struct printbuf *err)
 {
-       struct btree_trans trans;
-       struct btree_iter iter;
-       struct bkey_s_c k;
-       struct bkey_s_c_snapshot snap;
-       snapshot_id_list deleted = { 0 };
-       u32 i, id;
        int ret = 0;
 
-       if (!test_bit(BCH_FS_STARTED, &c->flags)) {
-               ret = bch2_fs_read_write_early(c);
-               if (ret) {
-                       bch_err(c, "error deleleting dead snapshots: error going rw: %s", bch2_err_str(ret));
-                       return ret;
-               }
-       }
-
-       bch2_trans_init(&trans, c, 0, 0);
-
-       /*
-        * For every snapshot node: If we have no live children and it's not
-        * pointed to by a subvolume, delete it:
-        */
-       ret = for_each_btree_key_commit(&trans, iter, BTREE_ID_snapshots,
-                       POS_MIN, 0, k,
-                       NULL, NULL, 0,
-               bch2_delete_redundant_snapshot(&trans, &iter, k));
-       if (ret) {
-               bch_err(c, "error deleting redundant snapshots: %s", bch2_err_str(ret));
-               goto err;
-       }
-
-       for_each_btree_key2(&trans, iter, BTREE_ID_snapshots,
-                          POS_MIN, 0, k,
-               bch2_snapshot_set_equiv(&trans, k));
-       if (ret) {
-               bch_err(c, "error in bch2_snapshots_set_equiv: %s", bch2_err_str(ret));
-               goto err;
-       }
-
-       for_each_btree_key(&trans, iter, BTREE_ID_snapshots,
-                          POS_MIN, 0, k, ret) {
-               if (k.k->type != KEY_TYPE_snapshot)
-                       continue;
-
-               snap = bkey_s_c_to_snapshot(k);
-               if (BCH_SNAPSHOT_DELETED(snap.v)) {
-                       ret = snapshot_list_add(c, &deleted, k.k->p.offset);
-                       if (ret)
-                               break;
-               }
-       }
-       bch2_trans_iter_exit(&trans, &iter);
-
-       if (ret) {
-               bch_err(c, "error walking snapshots: %s", bch2_err_str(ret));
-               goto err;
-       }
-
-       for (id = 0; id < BTREE_ID_NR; id++) {
-               struct bpos last_pos = POS_MIN;
-               snapshot_id_list equiv_seen = { 0 };
-
-               if (!btree_type_has_snapshots(id))
-                       continue;
-
-               ret = for_each_btree_key_commit(&trans, iter,
-                               id, POS_MIN,
-                               BTREE_ITER_PREFETCH|BTREE_ITER_ALL_SNAPSHOTS, k,
-                               NULL, NULL, BTREE_INSERT_NOFAIL,
-                       snapshot_delete_key(&trans, &iter, k, &deleted, &equiv_seen, &last_pos));
-
-               darray_exit(&equiv_seen);
-
-               if (ret) {
-                       bch_err(c, "error deleting snapshot keys: %s", bch2_err_str(ret));
-                       goto err;
-               }
-       }
-
-       for (i = 0; i < deleted.nr; i++) {
-               ret = commit_do(&trans, NULL, NULL, 0,
-                       bch2_snapshot_node_delete(&trans, deleted.data[i]));
-               if (ret) {
-                       bch_err(c, "error deleting snapshot %u: %s",
-                               deleted.data[i], bch2_err_str(ret));
-                       goto err;
-               }
-       }
-
-       clear_bit(BCH_FS_HAVE_DELETED_SNAPSHOTS, &c->flags);
-err:
-       darray_exit(&deleted);
-       bch2_trans_exit(&trans);
-       if (ret)
-               bch_err_fn(c, ret);
+       bkey_fsck_err_on(bkey_lt(k.k->p, SUBVOL_POS_MIN) ||
+                        bkey_gt(k.k->p, SUBVOL_POS_MAX), c, err,
+                        subvol_pos_bad,
+                        "invalid pos");
+fsck_err:
        return ret;
 }
 
-static void bch2_delete_dead_snapshots_work(struct work_struct *work)
-{
-       struct bch_fs *c = container_of(work, struct bch_fs, snapshot_delete_work);
-
-       if (test_bit(BCH_FS_HAVE_DELETED_SNAPSHOTS, &c->flags))
-               bch2_delete_dead_snapshots(c);
-       bch2_write_ref_put(c, BCH_WRITE_REF_delete_dead_snapshots);
-}
-
-void bch2_delete_dead_snapshots_async(struct bch_fs *c)
-{
-       if (bch2_write_ref_tryget(c, BCH_WRITE_REF_delete_dead_snapshots) &&
-           !queue_work(c->write_ref_wq, &c->snapshot_delete_work))
-               bch2_write_ref_put(c, BCH_WRITE_REF_delete_dead_snapshots);
-}
-
-static int bch2_delete_dead_snapshots_hook(struct btree_trans *trans,
-                                          struct btree_trans_commit_hook *h)
-{
-       struct bch_fs *c = trans->c;
-
-       set_bit(BCH_FS_HAVE_DELETED_SNAPSHOTS, &c->flags);
-
-       if (c->curr_recovery_pass <= BCH_RECOVERY_PASS_delete_dead_snapshots)
-               return 0;
-
-       bch2_delete_dead_snapshots_async(c);
-       return 0;
-}
-
-/* Subvolumes: */
-
-int bch2_subvolume_invalid(const struct bch_fs *c, struct bkey_s_c k,
-                          unsigned flags, struct printbuf *err)
-{
-       if (bkey_lt(k.k->p, SUBVOL_POS_MIN) ||
-           bkey_gt(k.k->p, SUBVOL_POS_MAX)) {
-               prt_printf(err, "invalid pos");
-               return -BCH_ERR_invalid_bkey;
-       }
-
-       return 0;
-}
-
 void bch2_subvolume_to_text(struct printbuf *out, struct bch_fs *c,
                            struct bkey_s_c k)
 {
@@ -1459,26 +151,27 @@ int bch2_snapshot_get_subvol(struct btree_trans *trans, u32 snapshot,
 {
        struct bch_snapshot snap;
 
-       return  snapshot_lookup(trans, snapshot, &snap) ?:
+       return  bch2_snapshot_lookup(trans, snapshot, &snap) ?:
                bch2_subvolume_get(trans, le32_to_cpu(snap.subvol), true, 0, subvol);
 }
 
-int bch2_subvolume_get_snapshot(struct btree_trans *trans, u32 subvol,
+int bch2_subvolume_get_snapshot(struct btree_trans *trans, u32 subvolid,
                                u32 *snapid)
 {
        struct btree_iter iter;
-       struct bkey_s_c k;
+       struct bkey_s_c_subvolume subvol;
        int ret;
 
-       k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_subvolumes, POS(0, subvol),
-                              BTREE_ITER_CACHED|
-                              BTREE_ITER_WITH_UPDATES);
-       ret = bkey_err(k) ?: k.k->type == KEY_TYPE_subvolume ? 0 : -BCH_ERR_ENOENT_subvolume;
+       subvol = bch2_bkey_get_iter_typed(trans, &iter,
+                                         BTREE_ID_subvolumes, POS(0, subvolid),
+                                         BTREE_ITER_CACHED|BTREE_ITER_WITH_UPDATES,
+                                         subvolume);
+       ret = bkey_err(subvol);
+       bch2_fs_inconsistent_on(bch2_err_matches(ret, ENOENT), trans->c,
+                               "missing subvolume %u", subvolid);
 
        if (likely(!ret))
-               *snapid = le32_to_cpu(bkey_s_c_to_subvolume(k).v->snapshot);
-       else if (bch2_err_matches(ret, ENOENT))
-               bch2_fs_inconsistent(trans->c, "missing subvolume %u", subvol);
+               *snapid = le32_to_cpu(subvol.v->snapshot);
        bch2_trans_iter_exit(trans, &iter);
        return ret;
 }
@@ -1508,7 +201,12 @@ static int bch2_subvolume_reparent(struct btree_trans *trans,
 }
 
 /*
- * Scan for subvolumes with parent @subvolid_to_delete, reparent:
+ * Separate from the snapshot tree in the snapshots btree, we record the tree
+ * structure of how snapshot subvolumes were created - the parent subvolume of
+ * each snapshot subvolume.
+ *
+ * When a subvolume is deleted, we scan for child subvolumes and reparant them,
+ * to avoid dangling references:
  */
 static int bch2_subvolumes_reparent(struct btree_trans *trans, u32 subvolid_to_delete)
 {
@@ -1521,7 +219,7 @@ static int bch2_subvolumes_reparent(struct btree_trans *trans, u32 subvolid_to_d
                                   BTREE_ITER_CACHED, &s)) ?:
                for_each_btree_key_commit(trans, iter,
                                BTREE_ID_subvolumes, POS_MIN, BTREE_ITER_PREFETCH, k,
-                               NULL, NULL, BTREE_INSERT_NOFAIL,
+                               NULL, NULL, BCH_TRANS_COMMIT_no_enospc,
                        bch2_subvolume_reparent(trans, &iter, k,
                                        subvolid_to_delete, le32_to_cpu(s.parent)));
 }
@@ -1534,7 +232,6 @@ static int __bch2_subvolume_delete(struct btree_trans *trans, u32 subvolid)
 {
        struct btree_iter iter;
        struct bkey_s_c_subvolume subvol;
-       struct btree_trans_commit_hook *h;
        u32 snapid;
        int ret = 0;
 
@@ -1550,22 +247,8 @@ static int __bch2_subvolume_delete(struct btree_trans *trans, u32 subvolid)
 
        snapid = le32_to_cpu(subvol.v->snapshot);
 
-       ret = bch2_btree_delete_at(trans, &iter, 0);
-       if (ret)
-               goto err;
-
-       ret = bch2_snapshot_node_set_deleted(trans, snapid);
-       if (ret)
-               goto err;
-
-       h = bch2_trans_kmalloc(trans, sizeof(*h));
-       ret = PTR_ERR_OR_ZERO(h);
-       if (ret)
-               goto err;
-
-       h->fn = bch2_delete_dead_snapshots_hook;
-       bch2_trans_commit_hook(trans, h);
-err:
+       ret =   bch2_btree_delete_at(trans, &iter, 0) ?:
+               bch2_snapshot_node_set_deleted(trans, snapid);
        bch2_trans_iter_exit(trans, &iter);
        return ret;
 }
@@ -1573,7 +256,7 @@ err:
 static int bch2_subvolume_delete(struct btree_trans *trans, u32 subvolid)
 {
        return bch2_subvolumes_reparent(trans, subvolid) ?:
-               commit_do(trans, NULL, NULL, BTREE_INSERT_NOFAIL,
+               commit_do(trans, NULL, NULL, BCH_TRANS_COMMIT_no_enospc,
                          __bch2_subvolume_delete(trans, subvolid));
 }
 
@@ -1597,9 +280,9 @@ static void bch2_subvolume_wait_for_pagecache_and_delete(struct work_struct *wor
                bch2_evict_subvolume_inodes(c, &s);
 
                for (id = s.data; id < s.data + s.nr; id++) {
-                       ret = bch2_trans_run(c, bch2_subvolume_delete(&trans, *id));
+                       ret = bch2_trans_run(c, bch2_subvolume_delete(trans, *id));
                        if (ret) {
-                               bch_err(c, "error deleting subvolume %u: %s", *id, bch2_err_str(ret));
+                               bch_err_msg(c, ret, "deleting subvolume %u", *id);
                                break;
                        }
                }