Move c_src dirs back to toplevel

We just wanted c sourcefiles out of the top level, not c source
directories.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

1 files changed, 0 insertions, 1685 deletions

diff --git a/c_src/libbcachefs/snapshot.c b/c_src/libbcachefs/snapshot.c
deleted file mode 100644
index 56af9375..00000000
--- a/c_src/libbcachefs/snapshot.c
+++ /dev/null
@@ -1,1685 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-
-#include "bcachefs.h"
-#include "bkey_buf.h"
-#include "btree_key_cache.h"
-#include "btree_update.h"
-#include "buckets.h"
-#include "errcode.h"
-#include "error.h"
-#include "fs.h"
-#include "snapshot.h"
-
-#include <linux/random.h>
-
-/*
- * Snapshot trees:
- *
- * Keys in BTREE_ID_snapshot_trees identify a whole tree of snapshot nodes; they
- * exist to provide a stable identifier for the whole lifetime of a 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(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_gt(k.k->p, POS(0, U32_MAX)) ||
-			 bkey_lt(k.k->p, POS(0, 1)), c, err,
-			 snapshot_tree_pos_bad,
-			 "bad pos");
-fsck_err:
-	return ret;
-}
-
-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;
-}
-
-struct bkey_i_snapshot_tree *
-__bch2_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 bch2_snapshot_tree_create(struct btree_trans *trans,
-				u32 root_id, u32 subvol_id, u32 *tree_id)
-{
-	struct bkey_i_snapshot_tree *n_tree =
-		__bch2_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: */
-
-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 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->recovery_pass_done <= 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);
-
-	if (id && id < ancestor) {
-		ret = test_bit(ancestor - id - 1, __snapshot_t(t, id)->is_ancestor);
-
-		EBUG_ON(ret != bch2_snapshot_is_ancestor_early(c, id, ancestor));
-	} else {
-		ret = id == ancestor;
-	}
-
-	rcu_read_unlock();
-
-	return ret;
-}
-
-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;
-	kvfree_rcu_mightsleep(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);
-}
-
-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(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;
-	int ret = 0;
-
-	bkey_fsck_err_on(bkey_gt(k.k->p, POS(0, U32_MAX)) ||
-			 bkey_lt(k.k->p, POS(0, 1)), c, err,
-			 snapshot_pos_bad,
-			 "bad pos");
-
-	s = bkey_s_c_to_snapshot(k);
-
-	id = le32_to_cpu(s.v->parent);
-	bkey_fsck_err_on(id && id <= k.k->p.offset, c, err,
-			 snapshot_parent_bad,
-			 "bad parent node (%u <= %llu)",
-			 id, k.k->p.offset);
-
-	bkey_fsck_err_on(le32_to_cpu(s.v->children[0]) < le32_to_cpu(s.v->children[1]), c, err,
-			 snapshot_children_not_normalized,
-			 "children not normalized");
-
-	bkey_fsck_err_on(s.v->children[0] && s.v->children[0] == s.v->children[1], c, err,
-			 snapshot_child_duplicate,
-			 "duplicate child nodes");
-
-	for (i = 0; i < 2; i++) {
-		id = le32_to_cpu(s.v->children[i]);
-
-		bkey_fsck_err_on(id >= k.k->p.offset, c, err,
-				 snapshot_child_bad,
-				 "bad child node (%u >= %llu)",
-				 id, k.k->p.offset);
-	}
-
-	if (bkey_val_bytes(k.k) > offsetof(struct bch_snapshot, skip)) {
-		bkey_fsck_err_on(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]), c, err,
-				 snapshot_skiplist_not_normalized,
-				 "skiplist not normalized");
-
-		for (i = 0; i < ARRAY_SIZE(s.v->skip); i++) {
-			id = le32_to_cpu(s.v->skip[i]);
-
-			bkey_fsck_err_on(id && id < le32_to_cpu(s.v->parent), c, err,
-					 snapshot_skiplist_bad,
-					 "bad skiplist node %u", id);
-		}
-	}
-fsck_err:
-	return ret;
-}
-
-static void __set_is_ancestor_bitmap(struct bch_fs *c, u32 id)
-{
-	struct snapshot_t *t = snapshot_t_mut(c, id);
-	u32 parent = id;
-
-	while ((parent = bch2_snapshot_parent_early(c, parent)) &&
-	       parent - id - 1 < IS_ANCESTOR_BITMAP)
-		__set_bit(parent - id - 1, t->is_ancestor);
-}
-
-static void set_is_ancestor_bitmap(struct bch_fs *c, u32 id)
-{
-	mutex_lock(&c->snapshot_table_lock);
-	__set_is_ancestor_bitmap(c, id);
-	mutex_unlock(&c->snapshot_table_lock);
-}
-
-static 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);
-
-		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;
-		}
-
-		__set_is_ancestor_bitmap(c, id);
-
-		if (BCH_SNAPSHOT_DELETED(s.v)) {
-			set_bit(BCH_FS_need_delete_dead_snapshots, &c->flags);
-			if (c->curr_recovery_pass > BCH_RECOVERY_PASS_delete_dead_snapshots)
-				bch2_delete_dead_snapshots_async(c);
-		}
-	} else {
-		memset(t, 0, sizeof(*t));
-	}
-err:
-	mutex_unlock(&c->snapshot_table_lock);
-	return ret;
-}
-
-int bch2_mark_snapshot(struct btree_trans *trans,
-		       enum btree_id btree, unsigned level,
-		       struct bkey_s_c old, struct bkey_s new,
-		       unsigned flags)
-{
-	return __bch2_mark_snapshot(trans, btree, level, old, new.s_c, flags);
-}
-
-int bch2_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 bch2_snapshot_live(struct btree_trans *trans, u32 id)
-{
-	struct bch_snapshot v;
-	int ret;
-
-	if (!id)
-		return 0;
-
-	ret = bch2_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);
-}
-
-/*
- * If @k is a snapshot with just one live child, it's part of a linear chain,
- * which we consider to be an equivalence class: and then after snapshot
- * deletion cleanup, there should only be a single key at a given position in
- * this equivalence class.
- *
- * This sets the equivalence class of @k to be the child's equivalence class, if
- * it's part of such a linear chain: this correctly sets equivalence classes on
- * startup if we run leaf to root (i.e. in natural key order).
- */
-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 = bch2_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;
-	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;
-
-		struct bkey_s_c_subvolume 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 *u;
-
-		*subvol_id = bch2_snapshot_tree_oldest_subvol(c, snapshot_root);
-
-		u = bch2_bkey_get_mut_typed(trans, &iter,
-					    BTREE_ID_subvolumes, POS(0, *subvol_id),
-					    0, subvolume);
-		ret = PTR_ERR_OR_ZERO(u);
-		if (ret)
-			return ret;
-
-		SET_BCH_SUBVOLUME_SNAP(&u->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 = bch2_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_to_missing_snapshot,
-			"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_to_missing_subvol,
-			"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_to_wrong_subvol,
-			"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_to_snapshot_subvol,
-			"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)
-{
-	int ret = bch2_trans_run(c,
-		for_each_btree_key_commit(trans, iter,
-			BTREE_ID_snapshot_trees, POS_MIN,
-			BTREE_ITER_PREFETCH, k,
-			NULL, NULL, BCH_TRANS_COMMIT_no_enospc,
-		check_snapshot_tree(trans, &iter, k)));
-	bch_err_fn(c, 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));
-}
-
-u32 bch2_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, u32 id, struct bch_snapshot s)
-{
-	unsigned i;
-
-	for (i = 0; i < 3; i++)
-		if (!s.parent) {
-			if (s.skip[i])
-				return false;
-		} else {
-			if (!bch2_snapshot_is_ancestor_early(trans->c, id, le32_to_cpu(s.skip[i])))
-				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) ?:
-			bch2_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 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 = bch2_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 = bch2_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_have_subvol,
-				"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_to_bad_snapshot_tree,
-			"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 (fsck_err_on(le32_to_cpu(s.depth) != real_depth,
-			c, snapshot_bad_depth,
-			"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, k.k->p.offset, s);
-	if (ret < 0)
-		goto err;
-
-	if (fsck_err_on(!ret, c, snapshot_bad_skiplist,
-			"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(bch2_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)
-{
-	/*
-	 * We iterate backwards as checking/fixing the depth field requires that
-	 * the parent's depth already be correct:
-	 */
-	int ret = bch2_trans_run(c,
-		for_each_btree_key_reverse_commit(trans, iter,
-				BTREE_ID_snapshots, POS_MAX,
-				BTREE_ITER_PREFETCH, k,
-				NULL, NULL, BCH_TRANS_COMMIT_no_enospc,
-			check_snapshot(trans, &iter, k)));
-	bch_err_fn(c, ret);
-	return ret;
-}
-
-/*
- * Mark a snapshot as deleted, for future cleanup:
- */
-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 inline void normalize_snapshot_child_pointers(struct bch_snapshot *s)
-{
-	if (le32_to_cpu(s->children[0]) < le32_to_cpu(s->children[1]))
-		swap(s->children[0], s->children[1]);
-}
-
-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 c_iter = (struct btree_iter) { NULL };
-	struct btree_iter tree_iter = (struct btree_iter) { NULL };
-	struct bkey_s_c_snapshot s;
-	u32 parent_id, child_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(s.v->children[1]);
-
-	parent_id = le32_to_cpu(s.v->parent);
-	child_id = le32_to_cpu(s.v->children[0]);
-
-	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);
-		bch2_fs_inconsistent_on(bch2_err_matches(ret, ENOENT), c,
-					"missing snapshot %u", parent_id);
-		if (unlikely(ret))
-			goto err;
-
-		/* find entry in parent->children for node being deleted */
-		for (i = 0; i < 2; i++)
-			if (le32_to_cpu(parent->v.children[i]) == id)
-				break;
-
-		if (bch2_fs_inconsistent_on(i == 2, c,
-					"snapshot %u missing child pointer to %u",
-					parent_id, id))
-			goto err;
-
-		parent->v.children[i] = cpu_to_le32(child_id);
-
-		normalize_snapshot_child_pointers(&parent->v);
-	}
-
-	if (child_id) {
-		struct bkey_i_snapshot *child;
-
-		child = bch2_bkey_get_mut_typed(trans, &c_iter,
-				     BTREE_ID_snapshots, POS(0, child_id),
-				     0, snapshot);
-		ret = PTR_ERR_OR_ZERO(child);
-		bch2_fs_inconsistent_on(bch2_err_matches(ret, ENOENT), c,
-					"missing snapshot %u", child_id);
-		if (unlikely(ret))
-			goto err;
-
-		child->v.parent = cpu_to_le32(parent_id);
-
-		if (!child->v.parent) {
-			child->v.skip[0] = 0;
-			child->v.skip[1] = 0;
-			child->v.skip[2] = 0;
-		}
-	}
-
-	if (!parent_id) {
-		/*
-		 * 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, &c_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(bch2_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;
-
-		mutex_lock(&c->snapshot_table_lock);
-		snapshot_t_mut(c, new_snapids[i])->equiv = new_snapids[i];
-		mutex_unlock(&c->snapshot_table_lock);
-	}
-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 = __bch2_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);
-
-}
-
-/*
- * If we have an unlinked inode in an internal snapshot node, and the inode
- * really has been deleted in all child snapshots, how does this get cleaned up?
- *
- * first there is the problem of how keys that have been overwritten in all
- * child snapshots get deleted (unimplemented?), but inodes may perhaps be
- * special?
- *
- * also: unlinked inode in internal snapshot appears to not be getting deleted
- * correctly if inode doesn't exist in leaf snapshots
- *
- * solution:
- *
- * for a key in an interior snapshot node that needs work to be done that
- * requires it to be mutated: iterate over all descendent leaf nodes and copy
- * that key to snapshot leaf nodes, where we can mutate it
- */
-
-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 move_key_to_correct_snapshot(struct btree_trans *trans,
-			       struct btree_iter *iter,
-			       struct bkey_s_c k)
-{
-	struct bch_fs *c = trans->c;
-	u32 equiv = bch2_snapshot_equiv(c, k.k->p.snapshot);
-
-	/*
-	 * When we have a linear chain of snapshot nodes, we consider
-	 * those to form an equivalence class: we're going to collapse
-	 * them all down to a single node, and keep the leaf-most node -
-	 * which has the same id as the equivalence class id.
-	 *
-	 * If there are multiple keys in different snapshots at the same
-	 * position, we're only going to keep the one in the newest
-	 * snapshot - the rest have been overwritten and are redundant,
-	 * and for the key we're going to keep we need to move it to the
-	 * equivalance class ID if it's not there already.
-	 */
-	if (equiv != k.k->p.snapshot) {
-		struct bkey_i *new = bch2_bkey_make_mut_noupdate(trans, k);
-		struct btree_iter new_iter;
-		int ret;
-
-		ret = PTR_ERR_OR_ZERO(new);
-		if (ret)
-			return ret;
-
-		new->k.p.snapshot = equiv;
-
-		bch2_trans_iter_init(trans, &new_iter, iter->btree_id, new->k.p,
-				     BTREE_ITER_ALL_SNAPSHOTS|
-				     BTREE_ITER_CACHED|
-				     BTREE_ITER_INTENT);
-
-		ret =   bch2_btree_iter_traverse(&new_iter) ?:
-			bch2_trans_update(trans, &new_iter, new,
-					BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE) ?:
-			bch2_btree_delete_at(trans, iter,
-					BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE);
-		bch2_trans_iter_exit(trans, &new_iter);
-		if (ret)
-			return ret;
-	}
-
-	return 0;
-}
-
-static int bch2_snapshot_needs_delete(struct btree_trans *trans, 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   = bch2_snapshot_live(trans, children[0]) ?:
-		bch2_snapshot_live(trans, children[1]);
-	if (ret < 0)
-		return ret;
-	return !ret;
-}
-
-/*
- * For a given snapshot, if it doesn't have a subvolume that points to it, and
- * it doesn't have child snapshot nodes - it's now redundant and we can mark it
- * as deleted.
- */
-static int bch2_delete_redundant_snapshot(struct btree_trans *trans, struct bkey_s_c k)
-{
-	int ret = bch2_snapshot_needs_delete(trans, k);
-
-	return ret <= 0
-		? ret
-		: bch2_snapshot_node_set_deleted(trans, k.k->p.offset);
-}
-
-static inline u32 bch2_snapshot_nth_parent_skip(struct bch_fs *c, u32 id, u32 n,
-						snapshot_id_list *skip)
-{
-	rcu_read_lock();
-	while (snapshot_list_has_id(skip, id))
-		id = __bch2_snapshot_parent(c, id);
-
-	while (n--) {
-		do {
-			id = __bch2_snapshot_parent(c, id);
-		} while (snapshot_list_has_id(skip, id));
-	}
-	rcu_read_unlock();
-
-	return id;
-}
-
-static int bch2_fix_child_of_deleted_snapshot(struct btree_trans *trans,
-					      struct btree_iter *iter, struct bkey_s_c k,
-					      snapshot_id_list *deleted)
-{
-	struct bch_fs *c = trans->c;
-	u32 nr_deleted_ancestors = 0;
-	struct bkey_i_snapshot *s;
-	int ret;
-
-	if (k.k->type != KEY_TYPE_snapshot)
-		return 0;
-
-	if (snapshot_list_has_id(deleted, k.k->p.offset))
-		return 0;
-
-	s = bch2_bkey_make_mut_noupdate_typed(trans, k, snapshot);
-	ret = PTR_ERR_OR_ZERO(s);
-	if (ret)
-		return ret;
-
-	darray_for_each(*deleted, i)
-		nr_deleted_ancestors += bch2_snapshot_is_ancestor(c, s->k.p.offset, *i);
-
-	if (!nr_deleted_ancestors)
-		return 0;
-
-	le32_add_cpu(&s->v.depth, -nr_deleted_ancestors);
-
-	if (!s->v.depth) {
-		s->v.skip[0] = 0;
-		s->v.skip[1] = 0;
-		s->v.skip[2] = 0;
-	} else {
-		u32 depth = le32_to_cpu(s->v.depth);
-		u32 parent = bch2_snapshot_parent(c, s->k.p.offset);
-
-		for (unsigned j = 0; j < ARRAY_SIZE(s->v.skip); j++) {
-			u32 id = le32_to_cpu(s->v.skip[j]);
-
-			if (snapshot_list_has_id(deleted, id)) {
-				id = bch2_snapshot_nth_parent_skip(c,
-							parent,
-							depth > 1
-							? get_random_u32_below(depth - 1)
-							: 0,
-							deleted);
-				s->v.skip[j] = cpu_to_le32(id);
-			}
-		}
-
-		bubble_sort(s->v.skip, ARRAY_SIZE(s->v.skip), cmp_le32);
-	}
-
-	return bch2_trans_update(trans, iter, &s->k_i, 0);
-}
-
-int bch2_delete_dead_snapshots(struct bch_fs *c)
-{
-	struct btree_trans *trans;
-	snapshot_id_list deleted = { 0 };
-	snapshot_id_list deleted_interior = { 0 };
-	u32 id;
-	int ret = 0;
-
-	if (!test_and_clear_bit(BCH_FS_need_delete_dead_snapshots, &c->flags))
-		return 0;
-
-	if (!test_bit(BCH_FS_started, &c->flags)) {
-		ret = bch2_fs_read_write_early(c);
-		bch_err_msg(c, ret, "deleting dead snapshots: error going rw");
-		if (ret)
-			return ret;
-	}
-
-	trans = bch2_trans_get(c);
-
-	/*
-	 * 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, k));
-	bch_err_msg(c, ret, "deleting redundant snapshots");
-	if (ret)
-		goto err;
-
-	ret = for_each_btree_key(trans, iter, BTREE_ID_snapshots,
-				 POS_MIN, 0, k,
-		bch2_snapshot_set_equiv(trans, k));
-	bch_err_msg(c, ret, "in bch2_snapshots_set_equiv");
-	if (ret)
-		goto err;
-
-	ret = for_each_btree_key(trans, iter, BTREE_ID_snapshots,
-				 POS_MIN, 0, k, ({
-		if (k.k->type != KEY_TYPE_snapshot)
-			continue;
-
-		BCH_SNAPSHOT_DELETED(bkey_s_c_to_snapshot(k).v)
-			? snapshot_list_add(c, &deleted, k.k->p.offset)
-			: 0;
-	}));
-	bch_err_msg(c, ret, "walking snapshots");
-	if (ret)
-		goto err;
-
-	for (id = 0; id < BTREE_ID_NR; id++) {
-		struct bpos last_pos = POS_MIN;
-		snapshot_id_list equiv_seen = { 0 };
-		struct disk_reservation res = { 0 };
-
-		if (!btree_type_has_snapshots(id))
-			continue;
-
-		/*
-		 * deleted inodes btree is maintained by a trigger on the inodes
-		 * btree - no work for us to do here, and it's not safe to scan
-		 * it because we'll see out of date keys due to the btree write
-		 * buffer:
-		 */
-		if (id == BTREE_ID_deleted_inodes)
-			continue;
-
-		ret = for_each_btree_key_commit(trans, iter,
-				id, POS_MIN,
-				BTREE_ITER_PREFETCH|BTREE_ITER_ALL_SNAPSHOTS, k,
-				&res, NULL, BCH_TRANS_COMMIT_no_enospc,
-			snapshot_delete_key(trans, &iter, k, &deleted, &equiv_seen, &last_pos)) ?:
-		      for_each_btree_key_commit(trans, iter,
-				id, POS_MIN,
-				BTREE_ITER_PREFETCH|BTREE_ITER_ALL_SNAPSHOTS, k,
-				&res, NULL, BCH_TRANS_COMMIT_no_enospc,
-			move_key_to_correct_snapshot(trans, &iter, k));
-
-		bch2_disk_reservation_put(c, &res);
-		darray_exit(&equiv_seen);
-
-		bch_err_msg(c, ret, "deleting keys from dying snapshots");
-		if (ret)
-			goto err;
-	}
-
-	bch2_trans_unlock(trans);
-	down_write(&c->snapshot_create_lock);
-
-	ret = for_each_btree_key(trans, iter, BTREE_ID_snapshots,
-				 POS_MIN, 0, k, ({
-		u32 snapshot = k.k->p.offset;
-		u32 equiv = bch2_snapshot_equiv(c, snapshot);
-
-		equiv != snapshot
-			? snapshot_list_add(c, &deleted_interior, snapshot)
-			: 0;
-	}));
-
-	bch_err_msg(c, ret, "walking snapshots");
-	if (ret)
-		goto err_create_lock;
-
-	/*
-	 * Fixing children of deleted snapshots can't be done completely
-	 * atomically, if we crash between here and when we delete the interior
-	 * nodes some depth fields will be off:
-	 */
-	ret = for_each_btree_key_commit(trans, iter, BTREE_ID_snapshots, POS_MIN,
-				  BTREE_ITER_INTENT, k,
-				  NULL, NULL, BCH_TRANS_COMMIT_no_enospc,
-		bch2_fix_child_of_deleted_snapshot(trans, &iter, k, &deleted_interior));
-	if (ret)
-		goto err_create_lock;
-
-	darray_for_each(deleted, i) {
-		ret = commit_do(trans, NULL, NULL, 0,
-			bch2_snapshot_node_delete(trans, *i));
-		bch_err_msg(c, ret, "deleting snapshot %u", *i);
-		if (ret)
-			goto err_create_lock;
-	}
-
-	darray_for_each(deleted_interior, i) {
-		ret = commit_do(trans, NULL, NULL, 0,
-			bch2_snapshot_node_delete(trans, *i));
-		bch_err_msg(c, ret, "deleting snapshot %u", *i);
-		if (ret)
-			goto err_create_lock;
-	}
-err_create_lock:
-	up_write(&c->snapshot_create_lock);
-err:
-	darray_exit(&deleted_interior);
-	darray_exit(&deleted);
-	bch2_trans_put(trans);
-	bch_err_fn(c, ret);
-	return ret;
-}
-
-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);
-	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);
-}
-
-int __bch2_key_has_snapshot_overwrites(struct btree_trans *trans,
-				       enum btree_id id,
-				       struct bpos pos)
-{
-	struct bch_fs *c = trans->c;
-	struct btree_iter iter;
-	struct bkey_s_c k;
-	int ret;
-
-	bch2_trans_iter_init(trans, &iter, id, pos,
-			     BTREE_ITER_NOT_EXTENTS|
-			     BTREE_ITER_ALL_SNAPSHOTS);
-	while (1) {
-		k = bch2_btree_iter_prev(&iter);
-		ret = bkey_err(k);
-		if (ret)
-			break;
-
-		if (!k.k)
-			break;
-
-		if (!bkey_eq(pos, k.k->p))
-			break;
-
-		if (bch2_snapshot_is_ancestor(c, k.k->p.snapshot, pos.snapshot)) {
-			ret = 1;
-			break;
-		}
-	}
-	bch2_trans_iter_exit(trans, &iter);
-
-	return ret;
-}
-
-static u32 bch2_snapshot_smallest_child(struct bch_fs *c, u32 id)
-{
-	const struct snapshot_t *s = snapshot_t(c, id);
-
-	return s->children[1] ?: s->children[0];
-}
-
-static u32 bch2_snapshot_smallest_descendent(struct bch_fs *c, u32 id)
-{
-	u32 child;
-
-	while ((child = bch2_snapshot_smallest_child(c, id)))
-		id = child;
-	return id;
-}
-
-static int bch2_propagate_key_to_snapshot_leaf(struct btree_trans *trans,
-					       enum btree_id btree,
-					       struct bkey_s_c interior_k,
-					       u32 leaf_id, struct bpos *new_min_pos)
-{
-	struct btree_iter iter;
-	struct bpos pos = interior_k.k->p;
-	struct bkey_s_c k;
-	struct bkey_i *new;
-	int ret;
-
-	pos.snapshot = leaf_id;
-
-	bch2_trans_iter_init(trans, &iter, btree, pos, BTREE_ITER_INTENT);
-	k = bch2_btree_iter_peek_slot(&iter);
-	ret = bkey_err(k);
-	if (ret)
-		goto out;
-
-	/* key already overwritten in this snapshot? */
-	if (k.k->p.snapshot != interior_k.k->p.snapshot)
-		goto out;
-
-	if (bpos_eq(*new_min_pos, POS_MIN)) {
-		*new_min_pos = k.k->p;
-		new_min_pos->snapshot = leaf_id;
-	}
-
-	new = bch2_bkey_make_mut_noupdate(trans, interior_k);
-	ret = PTR_ERR_OR_ZERO(new);
-	if (ret)
-		goto out;
-
-	new->k.p.snapshot = leaf_id;
-	ret = bch2_trans_update(trans, &iter, new, 0);
-out:
-	bch2_trans_iter_exit(trans, &iter);
-	return ret;
-}
-
-int bch2_propagate_key_to_snapshot_leaves(struct btree_trans *trans,
-					  enum btree_id btree,
-					  struct bkey_s_c k,
-					  struct bpos *new_min_pos)
-{
-	struct bch_fs *c = trans->c;
-	struct bkey_buf sk;
-	u32 restart_count = trans->restart_count;
-	int ret = 0;
-
-	bch2_bkey_buf_init(&sk);
-	bch2_bkey_buf_reassemble(&sk, c, k);
-	k = bkey_i_to_s_c(sk.k);
-
-	*new_min_pos = POS_MIN;
-
-	for (u32 id = bch2_snapshot_smallest_descendent(c, k.k->p.snapshot);
-	     id < k.k->p.snapshot;
-	     id++) {
-		if (!bch2_snapshot_is_ancestor(c, id, k.k->p.snapshot) ||
-		    !bch2_snapshot_is_leaf(c, id))
-			continue;
-again:
-		ret =   btree_trans_too_many_iters(trans) ?:
-			bch2_propagate_key_to_snapshot_leaf(trans, btree, k, id, new_min_pos) ?:
-			bch2_trans_commit(trans, NULL, NULL, 0);
-		if (ret && bch2_err_matches(ret, BCH_ERR_transaction_restart)) {
-			bch2_trans_begin(trans);
-			goto again;
-		}
-
-		if (ret)
-			break;
-	}
-
-	bch2_bkey_buf_exit(&sk, c);
-
-	return ret ?: trans_was_restarted(trans, restart_count);
-}
-
-static int bch2_check_snapshot_needs_deletion(struct btree_trans *trans, struct bkey_s_c k)
-{
-	struct bch_fs *c = trans->c;
-	struct bkey_s_c_snapshot snap;
-	int ret = 0;
-
-	if (k.k->type != KEY_TYPE_snapshot)
-		return 0;
-
-	snap = bkey_s_c_to_snapshot(k);
-	if (BCH_SNAPSHOT_DELETED(snap.v) ||
-	    bch2_snapshot_equiv(c, k.k->p.offset) != k.k->p.offset ||
-	    (ret = bch2_snapshot_needs_delete(trans, k)) > 0) {
-		set_bit(BCH_FS_need_delete_dead_snapshots, &c->flags);
-		return 0;
-	}
-
-	return ret;
-}
-
-int bch2_snapshots_read(struct bch_fs *c)
-{
-	int ret = bch2_trans_run(c,
-		for_each_btree_key(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) ?:
-			bch2_check_snapshot_needs_deletion(trans, k)) ?:
-		for_each_btree_key(trans, iter, BTREE_ID_snapshots,
-				   POS_MIN, 0, k,
-			   (set_is_ancestor_bitmap(c, k.k->p.offset), 0)));
-	bch_err_fn(c, ret);
-	return ret;
-}
-
-void bch2_fs_snapshots_exit(struct bch_fs *c)
-{
-	kfree(rcu_dereference_protected(c->snapshots, true));
-}