--- /dev/null
+// 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));
+}
projects / bcachefs-tools-debian / blobdiff