X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=libbcachefs%2Fsubvolume.c;h=7c67c28d3ef88ff32d1805257faf37ebc79f0d2d;hb=b5fd066153c40a70a29caa1ea7987723ab687763;hp=24244bc3d2fbff6703dcf5b4e27d513ebb7082dc;hpb=ddac1641ee1e2686c2211a8d671ea723634dfc89;p=bcachefs-tools-debian

diff --git a/libbcachefs/subvolume.c b/libbcachefs/subvolume.c
index 24244bc..7c67c28 100644
--- a/libbcachefs/subvolume.c
+++ b/libbcachefs/subvolume.c
@@ -6,893 +6,269 @@
 #include "errcode.h"
 #include "error.h"
 #include "fs.h"
+#include "snapshot.h"
 #include "subvolume.h"
 
-/* Snapshot tree: */
+#include <linux/random.h>
 
-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",
-	       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));
-}
-
-int bch2_snapshot_invalid(const struct bch_fs *c, struct bkey_s_c k,
-			  int rw, struct printbuf *err)
-{
-	struct bkey_s_c_snapshot s;
-	u32 i, id;
-
-	if (bkey_cmp(k.k->p, POS(0, U32_MAX)) > 0 ||
-	    bkey_cmp(k.k->p, POS(0, 1)) < 0) {
-		prt_printf(err, "bad pos");
-		return -EINVAL;
-	}
-
-	if (bkey_val_bytes(k.k) != sizeof(struct bch_snapshot)) {
-		prt_printf(err, "bad val size (%zu != %zu)",
-		       bkey_val_bytes(k.k), sizeof(struct bch_snapshot));
-		return -EINVAL;
-	}
-
-	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 -EINVAL;
-	}
-
-	if (le32_to_cpu(s.v->children[0]) < le32_to_cpu(s.v->children[1])) {
-		prt_printf(err, "children not normalized");
-		return -EINVAL;
-	}
-
-	if (s.v->children[0] &&
-	    s.v->children[0] == s.v->children[1]) {
-		prt_printf(err, "duplicate child nodes");
-		return -EINVAL;
-	}
-
-	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 -EINVAL;
-		}
-	}
-
-	return 0;
-}
-
-int bch2_mark_snapshot(struct btree_trans *trans,
-		       struct bkey_s_c old, struct bkey_s_c new,
-		       unsigned flags)
-{
-	struct bch_fs *c = trans->c;
-	struct snapshot_t *t;
-
-	t = genradix_ptr_alloc(&c->snapshots,
-			       U32_MAX - new.k->p.offset,
-			       GFP_KERNEL);
-	if (!t)
-		return -ENOMEM;
-
-	if (new.k->type == KEY_TYPE_snapshot) {
-		struct bkey_s_c_snapshot s = bkey_s_c_to_snapshot(new);
-
-		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;
-	} else {
-		t->parent	= 0;
-		t->children[0]	= 0;
-		t->children[1]	= 0;
-		t->subvol	= 0;
-	}
-
-	return 0;
-}
-
-static int snapshot_lookup(struct btree_trans *trans, u32 id,
-			   struct bch_snapshot *s)
-{
-	struct btree_iter iter;
-	struct bkey_s_c k;
-	int ret;
-
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_snapshots, POS(0, id),
-			     BTREE_ITER_WITH_UPDATES);
-	k = bch2_btree_iter_peek_slot(&iter);
-	ret = bkey_err(k) ?: k.k->type == KEY_TYPE_snapshot ? 0 : -ENOENT;
-
-	if (!ret)
-		*s = *bkey_s_c_to_snapshot(k).v;
-
-	bch2_trans_iter_exit(trans, &iter);
-	return ret;
-}
-
-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 (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;
-	}
-
-	snapshot_t(c, id)->equiv = nr_live == 1
-		? snapshot_t(c, child[live_idx])->equiv
-		: id;
-	return 0;
-}
-
-/* fsck: */
-static int check_snapshot(struct btree_trans *trans,
-			  struct btree_iter *iter,
-			  struct bkey_s_c k)
-{
-	struct bch_fs *c = trans->c;
-	struct bkey_s_c_snapshot s;
-	struct bch_subvolume subvol;
-	struct bch_snapshot v;
-	struct printbuf buf = PRINTBUF;
-	bool should_have_subvol;
-	u32 i, id;
-	int ret = 0;
-
-	if (k.k->type != KEY_TYPE_snapshot)
-		return 0;
-
-	s = bkey_s_c_to_snapshot(k);
-	id = le32_to_cpu(s.v->parent);
-	if (id) {
-		ret = snapshot_lookup(trans, id, &v);
-		if (ret == -ENOENT)
-			bch_err(c, "snapshot with nonexistent parent:\n  %s",
-				(bch2_bkey_val_to_text(&buf, c, s.s_c), buf.buf));
-		if (ret)
-			goto err;
-
-		if (le32_to_cpu(v.children[0]) != s.k->p.offset &&
-		    le32_to_cpu(v.children[1]) != s.k->p.offset) {
-			bch_err(c, "snapshot parent %u missing pointer to child %llu",
-				id, s.k->p.offset);
-			ret = -EINVAL;
-			goto err;
-		}
-	}
-
-	for (i = 0; i < 2 && s.v->children[i]; i++) {
-		id = le32_to_cpu(s.v->children[i]);
-
-		ret = snapshot_lookup(trans, id, &v);
-		if (ret == -ENOENT)
-			bch_err(c, "snapshot node %llu has nonexistent child %u",
-				s.k->p.offset, id);
-		if (ret)
-			goto err;
-
-		if (le32_to_cpu(v.parent) != s.k->p.offset) {
-			bch_err(c, "snapshot child %u has wrong parent (got %u should be %llu)",
-				id, le32_to_cpu(v.parent), s.k->p.offset);
-			ret = -EINVAL;
-			goto err;
-		}
-	}
-
-	should_have_subvol = BCH_SNAPSHOT_SUBVOL(s.v) &&
-		!BCH_SNAPSHOT_DELETED(s.v);
-
-	if (should_have_subvol) {
-		id = le32_to_cpu(s.v->subvol);
-		ret = bch2_subvolume_get(trans, id, 0, false, &subvol);
-		if (ret == -ENOENT)
-			bch_err(c, "snapshot points to nonexistent subvolume:\n  %s",
-				(bch2_bkey_val_to_text(&buf, c, s.s_c), buf.buf));
-		if (ret)
-			goto err;
-
-		if (BCH_SNAPSHOT_SUBVOL(s.v) != (le32_to_cpu(subvol.snapshot) == s.k->p.offset)) {
-			bch_err(c, "snapshot node %llu has wrong BCH_SNAPSHOT_SUBVOL",
-				s.k->p.offset);
-			ret = -EINVAL;
-			goto err;
-		}
-	} else {
-		if (fsck_err_on(s.v->subvol, c, "snapshot should not point to subvol:\n  %s",
-				(bch2_bkey_val_to_text(&buf, c, s.s_c), buf.buf))) {
-			struct bkey_i_snapshot *u = bch2_trans_kmalloc(trans, sizeof(*u));
-
-			ret = PTR_ERR_OR_ZERO(u);
-			if (ret)
-				goto err;
-
-			bkey_reassemble(&u->k_i, s.s_c);
-			u->v.subvol = 0;
-			ret = bch2_trans_update(trans, iter, &u->k_i, 0);
-			if (ret)
-				goto err;
-		}
-	}
-
-	if (BCH_SNAPSHOT_DELETED(s.v))
-		set_bit(BCH_FS_HAVE_DELETED_SNAPSHOTS, &c->flags);
-err:
-fsck_err:
-	printbuf_exit(&buf);
-	return ret;
-}
-
-int bch2_fs_check_snapshots(struct bch_fs *c)
-{
-	struct btree_trans trans;
-	struct btree_iter iter;
-	struct bkey_s_c k;
-	int ret;
-
-	bch2_trans_init(&trans, c, 0, 0);
-
-	ret = for_each_btree_key_commit(&trans, iter, BTREE_ID_snapshots,
-			POS(BCACHEFS_ROOT_INO, 0),
-			BTREE_ITER_PREFETCH, k,
-			NULL, NULL, BTREE_INSERT_LAZY_RW|BTREE_INSERT_NOFAIL,
-		check_snapshot(&trans, &iter, k));
-
-	if (ret)
-		bch_err(c, "error %i checking snapshots", ret);
-
-	bch2_trans_exit(&trans);
-	return ret;
-}
+static int bch2_subvolume_delete(struct btree_trans *, u32);
 
 static int check_subvol(struct btree_trans *trans,
 			struct btree_iter *iter,
 			struct bkey_s_c k)
 {
+	struct bch_fs *c = trans->c;
 	struct bkey_s_c_subvolume subvol;
 	struct bch_snapshot snapshot;
 	unsigned snapid;
-	int ret;
+	int ret = 0;
 
 	if (k.k->type != KEY_TYPE_subvolume)
 		return 0;
 
 	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 (ret == -ENOENT)
-		bch_err(trans->c, "subvolume %llu points to nonexistent snapshot %u",
+	if (bch2_err_matches(ret, ENOENT))
+		bch_err(c, "subvolume %llu points to nonexistent snapshot %u",
 			k.k->p.offset, snapid);
 	if (ret)
 		return ret;
 
 	if (BCH_SUBVOLUME_UNLINKED(subvol.v)) {
 		ret = bch2_subvolume_delete(trans, iter->pos.offset);
-		if (ret && !bch2_err_matches(ret, BCH_ERR_transaction_restart))
-			bch_err(trans->c, "error deleting subvolume %llu: %s",
-				iter->pos.offset, bch2_err_str(ret));
-		if (ret)
-			return ret;
+		bch_err_msg(c, ret, "deleting subvolume %llu", iter->pos.offset);
+		return ret ?: -BCH_ERR_transaction_restart_nested;
 	}
 
-	return 0;
-}
-
-int bch2_fs_check_subvols(struct bch_fs *c)
-{
-	struct btree_trans trans;
-	struct btree_iter iter;
-	struct bkey_s_c k;
-	int ret;
-
-	bch2_trans_init(&trans, c, 0, 0);
-
-	ret = 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));
-
-	bch2_trans_exit(&trans);
-
-	return ret;
-}
+	if (!BCH_SUBVOLUME_SNAP(subvol.v)) {
+		u32 snapshot_root = bch2_snapshot_root(c, le32_to_cpu(subvol.v->snapshot));
+		u32 snapshot_tree;
+		struct bch_snapshot_tree st;
 
-void bch2_fs_snapshots_exit(struct bch_fs *c)
-{
-	genradix_free(&c->snapshots);
-}
+		rcu_read_lock();
+		snapshot_tree = snapshot_t(c, snapshot_root)->tree;
+		rcu_read_unlock();
 
-int bch2_fs_snapshots_start(struct bch_fs *c)
-{
-	struct btree_trans trans;
-	struct btree_iter iter;
-	struct bkey_s_c k;
-	int ret = 0;
+		ret = bch2_snapshot_tree_lookup(trans, snapshot_tree, &st);
 
-	bch2_trans_init(&trans, c, 0, 0);
-
-	for_each_btree_key2(&trans, iter, BTREE_ID_snapshots,
-			   POS_MIN, 0, k,
-		bch2_mark_snapshot(&trans, bkey_s_c_null, k, 0) ?:
-		bch2_snapshot_set_equiv(&trans, k));
-
-	bch2_trans_exit(&trans);
-
-	if (ret)
-		bch_err(c, "error starting snapshots: %s", bch2_err_str(ret));
-	return ret;
-}
+		bch2_fs_inconsistent_on(bch2_err_matches(ret, ENOENT), c,
+				"%s: snapshot tree %u not found", __func__, snapshot_tree);
 
-/*
- * 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_s_c k;
-	struct bkey_i_snapshot *s;
-	int ret = 0;
+		if (ret)
+			return ret;
 
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_snapshots, POS(0, id),
-			     BTREE_ITER_INTENT);
-	k = bch2_btree_iter_peek_slot(&iter);
-	ret = bkey_err(k);
-	if (ret)
-		goto err;
+		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 =
+				bch2_bkey_make_mut_typed(trans, iter, &subvol.s_c, 0, subvolume);
+			ret = PTR_ERR_OR_ZERO(s);
+			if (ret)
+				return ret;
 
-	if (k.k->type != KEY_TYPE_snapshot) {
-		bch2_fs_inconsistent(trans->c, "missing snapshot %u", id);
-		ret = -ENOENT;
-		goto err;
+			SET_BCH_SUBVOLUME_SNAP(&s->v, true);
+		}
 	}
 
-	/* already deleted? */
-	if (BCH_SNAPSHOT_DELETED(bkey_s_c_to_snapshot(k).v))
-		goto err;
-
-	s = bch2_trans_kmalloc(trans, sizeof(*s));
-	ret = PTR_ERR_OR_ZERO(s);
-	if (ret)
-		goto err;
-
-	bkey_reassemble(&s->k_i, k);
-	SET_BCH_SNAPSHOT_DELETED(&s->v, true);
-	SET_BCH_SNAPSHOT_SUBVOL(&s->v, false);
-	s->v.subvol = 0;
-
-	ret = bch2_trans_update(trans, &iter, &s->k_i, 0);
-	if (ret)
-		goto err;
-err:
-	bch2_trans_iter_exit(trans, &iter);
+fsck_err:
 	return ret;
 }
 
-static int bch2_snapshot_node_delete(struct btree_trans *trans, u32 id)
+int bch2_check_subvols(struct bch_fs *c)
 {
-	struct btree_iter iter, p_iter = (struct btree_iter) { NULL };
-	struct bkey_s_c k;
-	struct bkey_s_c_snapshot s;
-	struct bkey_i_snapshot *parent;
-	u32 parent_id;
-	unsigned i;
-	int ret = 0;
-
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_snapshots, POS(0, id),
-			     BTREE_ITER_INTENT);
-	k = bch2_btree_iter_peek_slot(&iter);
-	ret = bkey_err(k);
-	if (ret)
-		goto err;
-
-	if (k.k->type != KEY_TYPE_snapshot) {
-		bch2_fs_inconsistent(trans->c, "missing snapshot %u", id);
-		ret = -ENOENT;
-		goto err;
-	}
-
-	s = bkey_s_c_to_snapshot(k);
-
-	BUG_ON(!BCH_SNAPSHOT_DELETED(s.v));
-	parent_id = le32_to_cpu(s.v->parent);
-
-	if (parent_id) {
-		bch2_trans_iter_init(trans, &p_iter, BTREE_ID_snapshots,
-				     POS(0, parent_id),
-				     BTREE_ITER_INTENT);
-		k = bch2_btree_iter_peek_slot(&p_iter);
-		ret = bkey_err(k);
-		if (ret)
-			goto err;
-
-		if (k.k->type != KEY_TYPE_snapshot) {
-			bch2_fs_inconsistent(trans->c, "missing snapshot %u", parent_id);
-			ret = -ENOENT;
-			goto err;
-		}
-
-		parent = bch2_trans_kmalloc(trans, sizeof(*parent));
-		ret = PTR_ERR_OR_ZERO(parent);
-		if (ret)
-			goto err;
-
-		bkey_reassemble(&parent->k_i, k);
-
-		for (i = 0; i < 2; i++)
-			if (le32_to_cpu(parent->v.children[i]) == id)
-				break;
-
-		if (i == 2)
-			bch_err(trans->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]);
-
-		ret = bch2_trans_update(trans, &p_iter, &parent->k_i, 0);
-		if (ret)
-			goto err;
-	}
-
-	ret = bch2_btree_delete_at(trans, &iter, 0);
-err:
-	bch2_trans_iter_exit(trans, &p_iter);
-	bch2_trans_iter_exit(trans, &iter);
+	int ret = bch2_trans_run(c,
+		for_each_btree_key_commit(trans, iter,
+				BTREE_ID_subvolumes, POS_MIN, BTREE_ITER_PREFETCH, k,
+				NULL, NULL, BCH_TRANS_COMMIT_no_enospc,
+			check_subvol(trans, &iter, k)));
+	bch_err_fn(c, ret);
 	return ret;
 }
 
-int bch2_snapshot_node_create(struct btree_trans *trans, u32 parent,
-			      u32 *new_snapids,
-			      u32 *snapshot_subvols,
-			      unsigned nr_snapids)
+/* Subvolumes: */
+
+int bch2_subvolume_invalid(struct bch_fs *c, struct bkey_s_c k,
+			   enum bkey_invalid_flags flags, struct printbuf *err)
 {
-	struct btree_iter iter;
-	struct bkey_i_snapshot *n;
-	struct bkey_s_c k;
-	unsigned i;
 	int ret = 0;
 
-	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 = -ENOSPC;
-			goto err;
-		}
-
-		n = bch2_trans_kmalloc(trans, sizeof(*n));
-		ret = PTR_ERR_OR_ZERO(n);
-		if (ret)
-			goto err;
-
-		bkey_snapshot_init(&n->k_i);
-		n->k.p		= iter.pos;
-		n->v.flags	= 0;
-		n->v.parent	= cpu_to_le32(parent);
-		n->v.subvol	= cpu_to_le32(snapshot_subvols[i]);
-		n->v.pad	= 0;
-		SET_BCH_SNAPSHOT_SUBVOL(&n->v, true);
-
-		ret   = bch2_trans_update(trans, &iter, &n->k_i, 0) ?:
-			bch2_mark_snapshot(trans, bkey_s_c_null, bkey_i_to_s_c(&n->k_i), 0);
-		if (ret)
-			goto err;
-
-		new_snapids[i]	= iter.pos.offset;
-	}
-
-	if (parent) {
-		bch2_btree_iter_set_pos(&iter, POS(0, parent));
-		k = bch2_btree_iter_peek(&iter);
-		ret = bkey_err(k);
-		if (ret)
-			goto err;
-
-		if (k.k->type != KEY_TYPE_snapshot) {
-			bch_err(trans->c, "snapshot %u not found", parent);
-			ret = -ENOENT;
-			goto err;
-		}
-
-		n = bch2_trans_kmalloc(trans, sizeof(*n));
-		ret = PTR_ERR_OR_ZERO(n);
-		if (ret)
-			goto err;
-
-		bkey_reassemble(&n->k_i, k);
-
-		if (n->v.children[0] || n->v.children[1]) {
-			bch_err(trans->c, "Trying to add child snapshot nodes to parent that already has children");
-			ret = -EINVAL;
-			goto err;
-		}
-
-		n->v.children[0] = cpu_to_le32(new_snapids[0]);
-		n->v.children[1] = cpu_to_le32(new_snapids[1]);
-		n->v.subvol = 0;
-		SET_BCH_SNAPSHOT_SUBVOL(&n->v, false);
-		ret = bch2_trans_update(trans, &iter, &n->k_i, 0);
-		if (ret)
-			goto err;
-	}
-err:
-	bch2_trans_iter_exit(trans, &iter);
+	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 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 = snapshot_t(c, k.k->p.snapshot)->equiv;
-
-	if (bkey_cmp(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)
+void bch2_subvolume_to_text(struct printbuf *out, struct bch_fs *c,
+			    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]);
+	struct bkey_s_c_subvolume s = bkey_s_c_to_subvolume(k);
 
-	ret   = snapshot_live(trans, children[0]) ?:
-		snapshot_live(trans, children[1]);
-	if (ret < 0)
-		return ret;
+	prt_printf(out, "root %llu snapshot id %u",
+		   le64_to_cpu(s.v->inode),
+		   le32_to_cpu(s.v->snapshot));
 
-	if (!ret)
-		return bch2_snapshot_node_set_deleted(trans, k.k->p.offset);
-	return 0;
+	if (bkey_val_bytes(s.k) > offsetof(struct bch_subvolume, parent))
+		prt_printf(out, " parent %u", le32_to_cpu(s.v->parent));
 }
 
-int bch2_delete_dead_snapshots(struct bch_fs *c)
+static __always_inline int
+bch2_subvolume_get_inlined(struct btree_trans *trans, unsigned subvol,
+			   bool inconsistent_if_not_found,
+			   int iter_flags,
+			   struct bch_subvolume *s)
 {
-	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_HAVE_DELETED_SNAPSHOTS, &c->flags))
-		return 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);
+	int ret = bch2_bkey_get_val_typed(trans, BTREE_ID_subvolumes, POS(0, subvol),
+					  iter_flags, subvolume, s);
+	bch2_fs_inconsistent_on(bch2_err_matches(ret, ENOENT) &&
+				inconsistent_if_not_found,
+				trans->c, "missing subvolume %u", subvol);
 	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);
-
-	bch2_delete_dead_snapshots(c);
-	percpu_ref_put(&c->writes);
-}
-
-void bch2_delete_dead_snapshots_async(struct bch_fs *c)
+int bch2_subvolume_get(struct btree_trans *trans, unsigned subvol,
+		       bool inconsistent_if_not_found,
+		       int iter_flags,
+		       struct bch_subvolume *s)
 {
-	if (!percpu_ref_tryget_live(&c->writes))
-		return;
-
-	if (!queue_work(system_long_wq, &c->snapshot_delete_work))
-		percpu_ref_put(&c->writes);
+	return bch2_subvolume_get_inlined(trans, subvol, inconsistent_if_not_found, iter_flags, s);
 }
 
-static int bch2_delete_dead_snapshots_hook(struct btree_trans *trans,
-					   struct btree_trans_commit_hook *h)
+int bch2_subvol_is_ro_trans(struct btree_trans *trans, u32 subvol)
 {
-	struct bch_fs *c = trans->c;
-
-	set_bit(BCH_FS_HAVE_DELETED_SNAPSHOTS, &c->flags);
-
-	if (!test_bit(BCH_FS_FSCK_DONE, &c->flags))
-		return 0;
+	struct bch_subvolume s;
+	int ret = bch2_subvolume_get_inlined(trans, subvol, true, 0, &s);
+	if (ret)
+		return ret;
 
-	bch2_delete_dead_snapshots_async(c);
+	if (BCH_SUBVOLUME_RO(&s))
+		return -EROFS;
 	return 0;
 }
 
-/* Subvolumes: */
-
-int bch2_subvolume_invalid(const struct bch_fs *c, struct bkey_s_c k,
-			   int rw, struct printbuf *err)
+int bch2_subvol_is_ro(struct bch_fs *c, u32 subvol)
 {
-	if (bkey_cmp(k.k->p, SUBVOL_POS_MIN) < 0 ||
-	    bkey_cmp(k.k->p, SUBVOL_POS_MAX) > 0) {
-		prt_printf(err, "invalid pos");
-		return -EINVAL;
-	}
-
-	if (bkey_val_bytes(k.k) != sizeof(struct bch_subvolume)) {
-		prt_printf(err, "incorrect value size (%zu != %zu)",
-		       bkey_val_bytes(k.k), sizeof(struct bch_subvolume));
-		return -EINVAL;
-	}
-
-	return 0;
+	return bch2_trans_do(c, NULL, NULL, 0,
+		bch2_subvol_is_ro_trans(trans, subvol));
 }
 
-void bch2_subvolume_to_text(struct printbuf *out, struct bch_fs *c,
-			    struct bkey_s_c k)
+int bch2_snapshot_get_subvol(struct btree_trans *trans, u32 snapshot,
+			     struct bch_subvolume *subvol)
 {
-	struct bkey_s_c_subvolume s = bkey_s_c_to_subvolume(k);
+	struct bch_snapshot snap;
 
-	prt_printf(out, "root %llu snapshot id %u",
-	       le64_to_cpu(s.v->inode),
-	       le32_to_cpu(s.v->snapshot));
+	return  bch2_snapshot_lookup(trans, snapshot, &snap) ?:
+		bch2_subvolume_get(trans, le32_to_cpu(snap.subvol), true, 0, subvol);
 }
 
-int bch2_subvolume_get(struct btree_trans *trans, unsigned subvol,
-		       bool inconsistent_if_not_found,
-		       int iter_flags,
-		       struct bch_subvolume *s)
+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;
 
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_subvolumes, POS(0, subvol),
-			     iter_flags);
-	k = bch2_btree_iter_peek_slot(&iter);
-	ret = bkey_err(k) ?: k.k->type == KEY_TYPE_subvolume ? 0 : -ENOENT;
-
-	if (ret == -ENOENT && inconsistent_if_not_found)
-		bch2_fs_inconsistent(trans->c, "missing subvolume %u", subvol);
-	if (!ret)
-		*s = *bkey_s_c_to_subvolume(k).v;
+	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(subvol.v->snapshot);
 	bch2_trans_iter_exit(trans, &iter);
 	return ret;
 }
 
-int bch2_snapshot_get_subvol(struct btree_trans *trans, u32 snapshot,
-			     struct bch_subvolume *subvol)
+static int bch2_subvolume_reparent(struct btree_trans *trans,
+				   struct btree_iter *iter,
+				   struct bkey_s_c k,
+				   u32 old_parent, u32 new_parent)
 {
-	struct bch_snapshot snap;
+	struct bkey_i_subvolume *s;
+	int ret;
 
-	return  snapshot_lookup(trans, snapshot, &snap) ?:
-		bch2_subvolume_get(trans, le32_to_cpu(snap.subvol), true, 0, subvol);
+	if (k.k->type != KEY_TYPE_subvolume)
+		return 0;
+
+	if (bkey_val_bytes(k.k) > offsetof(struct bch_subvolume, parent) &&
+	    le32_to_cpu(bkey_s_c_to_subvolume(k).v->parent) != old_parent)
+		return 0;
+
+	s = bch2_bkey_make_mut_typed(trans, iter, &k, 0, subvolume);
+	ret = PTR_ERR_OR_ZERO(s);
+	if (ret)
+		return ret;
+
+	s->v.parent = cpu_to_le32(new_parent);
+	return 0;
 }
 
-int bch2_subvolume_get_snapshot(struct btree_trans *trans, u32 subvol,
-				u32 *snapid)
+/*
+ * 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)
 {
 	struct bch_subvolume s;
-	int ret;
 
-	ret = bch2_subvolume_get(trans, subvol, true,
-				 BTREE_ITER_CACHED|
-				 BTREE_ITER_WITH_UPDATES,
-				 &s);
-
-	*snapid = le32_to_cpu(s.snapshot);
-	return ret;
+	return lockrestart_do(trans,
+			bch2_subvolume_get(trans, subvolid_to_delete, true,
+				   BTREE_ITER_CACHED, &s)) ?:
+		for_each_btree_key_commit(trans, iter,
+				BTREE_ID_subvolumes, POS_MIN, BTREE_ITER_PREFETCH, k,
+				NULL, NULL, BCH_TRANS_COMMIT_no_enospc,
+			bch2_subvolume_reparent(trans, &iter, k,
+					subvolid_to_delete, le32_to_cpu(s.parent)));
 }
 
 /*
  * Delete subvolume, mark snapshot ID as deleted, queue up snapshot
  * deletion/cleanup:
  */
-int bch2_subvolume_delete(struct btree_trans *trans, u32 subvolid)
+static int __bch2_subvolume_delete(struct btree_trans *trans, u32 subvolid)
 {
 	struct btree_iter iter;
-	struct bkey_s_c k;
 	struct bkey_s_c_subvolume subvol;
-	struct btree_trans_commit_hook *h;
 	u32 snapid;
 	int ret = 0;
 
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_subvolumes,
-			     POS(0, subvolid),
-			     BTREE_ITER_CACHED|
-			     BTREE_ITER_INTENT);
-	k = bch2_btree_iter_peek_slot(&iter);
-	ret = bkey_err(k);
+	subvol = bch2_bkey_get_iter_typed(trans, &iter,
+				BTREE_ID_subvolumes, POS(0, subvolid),
+				BTREE_ITER_CACHED|BTREE_ITER_INTENT,
+				subvolume);
+	ret = bkey_err(subvol);
+	bch2_fs_inconsistent_on(bch2_err_matches(ret, ENOENT), trans->c,
+				"missing subvolume %u", subvolid);
 	if (ret)
-		goto err;
-
-	if (k.k->type != KEY_TYPE_subvolume) {
-		bch2_fs_inconsistent(trans->c, "missing subvolume %u", subvolid);
-		ret = -EIO;
-		goto err;
-	}
+		return ret;
 
-	subvol = bkey_s_c_to_subvolume(k);
 	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;
 }
 
-void bch2_subvolume_wait_for_pagecache_and_delete(struct work_struct *work)
+static int bch2_subvolume_delete(struct btree_trans *trans, u32 subvolid)
+{
+	return bch2_subvolumes_reparent(trans, subvolid) ?:
+		commit_do(trans, NULL, NULL, BCH_TRANS_COMMIT_no_enospc,
+			  __bch2_subvolume_delete(trans, subvolid));
+}
+
+static void bch2_subvolume_wait_for_pagecache_and_delete(struct work_struct *work)
 {
 	struct bch_fs *c = container_of(work, struct bch_fs,
 				snapshot_wait_for_pagecache_and_delete_work);
@@ -912,18 +288,16 @@ void bch2_subvolume_wait_for_pagecache_and_delete(struct work_struct *work)
 		bch2_evict_subvolume_inodes(c, &s);
 
 		for (id = s.data; id < s.data + s.nr; id++) {
-			ret = bch2_trans_do(c, NULL, NULL, BTREE_INSERT_NOFAIL,
-				      bch2_subvolume_delete(&trans, *id));
-			if (ret) {
-				bch_err(c, "error deleting subvolume %u: %s", *id, bch2_err_str(ret));
+			ret = bch2_trans_run(c, bch2_subvolume_delete(trans, *id));
+			bch_err_msg(c, ret, "deleting subvolume %u", *id);
+			if (ret)
 				break;
-			}
 		}
 
 		darray_exit(&s);
 	}
 
-	percpu_ref_put(&c->writes);
+	bch2_write_ref_put(c, BCH_WRITE_REF_snapshot_delete_pagecache);
 }
 
 struct subvolume_unlink_hook {
@@ -931,7 +305,7 @@ struct subvolume_unlink_hook {
 	u32				subvol;
 };
 
-int bch2_subvolume_wait_for_pagecache_and_delete_hook(struct btree_trans *trans,
+static int bch2_subvolume_wait_for_pagecache_and_delete_hook(struct btree_trans *trans,
 						      struct btree_trans_commit_hook *_h)
 {
 	struct subvolume_unlink_hook *h = container_of(_h, struct subvolume_unlink_hook, h);
@@ -946,58 +320,41 @@ int bch2_subvolume_wait_for_pagecache_and_delete_hook(struct btree_trans *trans,
 	if (ret)
 		return ret;
 
-	if (unlikely(!percpu_ref_tryget_live(&c->writes)))
+	if (!bch2_write_ref_tryget(c, BCH_WRITE_REF_snapshot_delete_pagecache))
 		return -EROFS;
 
-	if (!queue_work(system_long_wq, &c->snapshot_wait_for_pagecache_and_delete_work))
-		percpu_ref_put(&c->writes);
+	if (!queue_work(c->write_ref_wq, &c->snapshot_wait_for_pagecache_and_delete_work))
+		bch2_write_ref_put(c, BCH_WRITE_REF_snapshot_delete_pagecache);
 	return 0;
 }
 
 int bch2_subvolume_unlink(struct btree_trans *trans, u32 subvolid)
 {
 	struct btree_iter iter;
-	struct bkey_s_c k;
 	struct bkey_i_subvolume *n;
 	struct subvolume_unlink_hook *h;
 	int ret = 0;
 
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_subvolumes,
-			     POS(0, subvolid),
-			     BTREE_ITER_CACHED|
-			     BTREE_ITER_INTENT);
-	k = bch2_btree_iter_peek_slot(&iter);
-	ret = bkey_err(k);
-	if (ret)
-		goto err;
-
-	if (k.k->type != KEY_TYPE_subvolume) {
-		bch2_fs_inconsistent(trans->c, "missing subvolume %u", subvolid);
-		ret = -EIO;
-		goto err;
-	}
-
-	n = bch2_trans_kmalloc(trans, sizeof(*n));
-	ret = PTR_ERR_OR_ZERO(n);
-	if (ret)
-		goto err;
-
-	bkey_reassemble(&n->k_i, k);
-	SET_BCH_SUBVOLUME_UNLINKED(&n->v, true);
-
-	ret = bch2_trans_update(trans, &iter, &n->k_i, 0);
-	if (ret)
-		goto err;
-
 	h = bch2_trans_kmalloc(trans, sizeof(*h));
 	ret = PTR_ERR_OR_ZERO(h);
 	if (ret)
-		goto err;
+		return ret;
 
 	h->h.fn		= bch2_subvolume_wait_for_pagecache_and_delete_hook;
 	h->subvol	= subvolid;
 	bch2_trans_commit_hook(trans, &h->h);
-err:
+
+	n = bch2_bkey_get_mut_typed(trans, &iter,
+			BTREE_ID_subvolumes, POS(0, subvolid),
+			BTREE_ITER_CACHED, subvolume);
+	ret = PTR_ERR_OR_ZERO(n);
+	if (unlikely(ret)) {
+		bch2_fs_inconsistent_on(bch2_err_matches(ret, ENOENT), trans->c,
+					"missing subvolume %u", subvolid);
+		return ret;
+	}
+
+	SET_BCH_SUBVOLUME_UNLINKED(&n->v, true);
 	bch2_trans_iter_exit(trans, &iter);
 	return ret;
 }
@@ -1012,54 +369,32 @@ int bch2_subvolume_create(struct btree_trans *trans, u64 inode,
 	struct btree_iter dst_iter, src_iter = (struct btree_iter) { NULL };
 	struct bkey_i_subvolume *new_subvol = NULL;
 	struct bkey_i_subvolume *src_subvol = NULL;
-	struct bkey_s_c k;
 	u32 parent = 0, new_nodes[2], snapshot_subvols[2];
 	int ret = 0;
 
-	for_each_btree_key(trans, dst_iter, BTREE_ID_subvolumes, SUBVOL_POS_MIN,
-			   BTREE_ITER_SLOTS|BTREE_ITER_INTENT, k, ret) {
-		if (bkey_cmp(k.k->p, SUBVOL_POS_MAX) > 0)
-			break;
-
-		/*
-		 * bch2_subvolume_delete() doesn't flush the btree key cache -
-		 * ideally it would but that's tricky
-		 */
-		if (bkey_deleted(k.k) &&
-		    !bch2_btree_key_cache_find(c, BTREE_ID_subvolumes, dst_iter.pos))
-			goto found_slot;
-	}
+	ret = bch2_bkey_get_empty_slot(trans, &dst_iter,
+				BTREE_ID_subvolumes, POS(0, U32_MAX));
+	if (ret == -BCH_ERR_ENOSPC_btree_slot)
+		ret = -BCH_ERR_ENOSPC_subvolume_create;
+	if (ret)
+		return ret;
 
-	if (!ret)
-		ret = -ENOSPC;
-	goto err;
-found_slot:
 	snapshot_subvols[0] = dst_iter.pos.offset;
 	snapshot_subvols[1] = src_subvolid;
 
 	if (src_subvolid) {
 		/* Creating a snapshot: */
-		src_subvol = bch2_trans_kmalloc(trans, sizeof(*src_subvol));
-		ret = PTR_ERR_OR_ZERO(src_subvol);
-		if (ret)
-			goto err;
-
-		bch2_trans_iter_init(trans, &src_iter, BTREE_ID_subvolumes,
-				     POS(0, src_subvolid),
-				     BTREE_ITER_CACHED|
-				     BTREE_ITER_INTENT);
-		k = bch2_btree_iter_peek_slot(&src_iter);
-		ret = bkey_err(k);
-		if (ret)
-			goto err;
 
-		if (k.k->type != KEY_TYPE_subvolume) {
-			bch_err(c, "subvolume %u not found", src_subvolid);
-			ret = -ENOENT;
+		src_subvol = bch2_bkey_get_mut_typed(trans, &src_iter,
+				BTREE_ID_subvolumes, POS(0, src_subvolid),
+				BTREE_ITER_CACHED, subvolume);
+		ret = PTR_ERR_OR_ZERO(src_subvol);
+		if (unlikely(ret)) {
+			bch2_fs_inconsistent_on(bch2_err_matches(ret, ENOENT), c,
+						"subvolume %u not found", src_subvolid);
 			goto err;
 		}
 
-		bkey_reassemble(&src_subvol->k_i, k);
 		parent = le32_to_cpu(src_subvol->v.snapshot);
 	}
 
@@ -1076,21 +411,20 @@ found_slot:
 			goto err;
 	}
 
-	new_subvol = bch2_trans_kmalloc(trans, sizeof(*new_subvol));
+	new_subvol = bch2_bkey_alloc(trans, &dst_iter, 0, subvolume);
 	ret = PTR_ERR_OR_ZERO(new_subvol);
 	if (ret)
 		goto err;
 
-	bkey_subvolume_init(&new_subvol->k_i);
 	new_subvol->v.flags	= 0;
 	new_subvol->v.snapshot	= cpu_to_le32(new_nodes[0]);
 	new_subvol->v.inode	= cpu_to_le64(inode);
+	new_subvol->v.parent	= cpu_to_le32(src_subvolid);
+	new_subvol->v.otime.lo	= cpu_to_le64(bch2_current_time(c));
+	new_subvol->v.otime.hi	= 0;
+
 	SET_BCH_SUBVOLUME_RO(&new_subvol->v, ro);
 	SET_BCH_SUBVOLUME_SNAP(&new_subvol->v, src_subvolid != 0);
-	new_subvol->k.p		= dst_iter.pos;
-	ret = bch2_trans_update(trans, &dst_iter, &new_subvol->k_i, 0);
-	if (ret)
-		goto err;
 
 	*new_subvolid	= new_subvol->k.p.offset;
 	*new_snapshotid	= new_nodes[0];