thin-provisioning-tools/persistent-data/data-structures/btree_damage_visitor.h

#ifndef PERSISTENT_DATA_DATA_STRUCTURES_DAMAGE_VISITOR_H
#define PERSISTENT_DATA_DATA_STRUCTURES_DAMAGE_VISITOR_H

#include "persistent-data/data-structures/btree.h"
#include "persistent-data/range.h"

//----------------------------------------------------------------

namespace persistent_data {

	namespace btree_detail {
		struct damage {
			typedef boost::shared_ptr<damage> ptr;

			damage(unsigned level,
			       range<uint64_t> lost_keys,
			       std::string const &desc)
				: level_(level),
				  lost_keys_(lost_keys),
				  desc_(desc) {
			}

			// Does _not_ compare the descriptions
			bool operator ==(damage const &rhs) const {
				return (level_ == rhs.level_) &&
					(lost_keys_ == rhs.lost_keys_);
			}

			unsigned level_;
			range<uint64_t> lost_keys_;
			std::string desc_;
		};
	}

	//----------------------------------------------------------------

	// This class implements consistency checking for the btrees.  It
	// also allows the caller to visit all accessible values.

	// Derive from this if you want some additional checks.  It's worth
	// summarising what is checked:

	//
	// Implemented
	// -----------
	//
	// - block_nr
	// - nr_entries < max_entries
	// - max_entries fits in block
	// - max_entries is divisible by 3
	// - nr_entries > minimum (except for root nodes)
	//
	// Not implemented
	// ---------------
	//
	// - leaf | internal flags (this can be inferred from siblings)

	//----------------------------------------------------------------

	template <typename ValueVisitor, typename DamageVisitor, uint32_t Levels, typename ValueTraits>
	class btree_damage_visitor : public btree<Levels, ValueTraits>::visitor {
	public:
		typedef btree_detail::node_location node_location;

		btree_damage_visitor(block_counter &counter,
				     ValueVisitor &value_visitor,
				     DamageVisitor &damage_visitor)
			: counter_(counter),
			  avoid_repeated_visits_(true),
			  value_visitor_(value_visitor),
			  damage_visitor_(damage_visitor) {
		}

		bool visit_internal(node_location const &loc,
				    btree_detail::node_ref<uint64_traits> const &n) {
			return check_internal(loc, n);
		}

		bool visit_internal_leaf(node_location const &loc,
					 btree_detail::node_ref<uint64_traits> const &n) {
			return check_leaf(loc, n);
		}

		bool visit_leaf(node_location const &loc,
				btree_detail::node_ref<ValueTraits> const &n) {
			bool r = check_leaf(loc, n);

			// If anything goes wrong with the checks, we skip
			// the value visiting.
			if (!r)
				return false;

			visit_values(n);

			return true;
		}

		typedef typename btree<Levels, ValueTraits>::visitor::error_outcome error_outcome;

		error_outcome error_accessing_node(node_location const &l, block_address b,
						   std::string const &what) {
			report_damage(what);
			return btree<Levels, ValueTraits>::visitor::EXCEPTION_HANDLED;
		}

	private:
		void visit_values(btree_detail::node_ref<ValueTraits> const &n) {
			unsigned nr = n.get_nr_entries();
			for (unsigned i = 0; i < nr; i++)
				value_visitor_.visit(n.value_at(i));
		}

		bool check_internal(node_location const &loc,
				    btree_detail::node_ref<uint64_traits> const &n) {
			if (!already_visited(n) &&
			    check_block_nr(n) &&
			    check_max_entries(n) &&
			    check_nr_entries(n, loc.sub_root) &&
			    check_ordered_keys(n) &&
			    check_parent_key(loc.sub_root ? optional<uint64_t>() : loc.key, n)) {
				if (loc.sub_root)
					new_root(loc.level);

				return true;
			}

			return false;
		}

		template <typename ValueTraits2>
		bool check_leaf(node_location const &loc,
				btree_detail::node_ref<ValueTraits2> const &n) {
			if (!already_visited(n) &&
			    check_block_nr(n) &&
			    check_max_entries(n) &&
			    check_nr_entries(n, loc.sub_root) &&
			    check_ordered_keys(n) &&
			    check_parent_key(loc.sub_root ? optional<uint64_t>() : loc.key, n)) {
				if (loc.sub_root)
					new_root(loc.level);

				return check_leaf_key(loc.level, n);
			}

			return false;
		}


		template <typename node>
		bool already_visited(node const &n) {
			block_address b = n.get_location();

			counter_.inc(b);

			if (avoid_repeated_visits_) {
				if (seen_.count(b) > 0)
					return true;

				seen_.insert(b);
			}

			return false;
		}

		template <typename node>
		bool check_block_nr(node const &n) {
			if (n.get_location() != n.get_block_nr()) {
				std::ostringstream out;
				out << "block number mismatch: actually "
				    << n.get_location()
				    << ", claims " << n.get_block_nr();

				report_damage(n, out.str());
				return false;
			}

			return true;
		}

		template <typename node>
		bool check_max_entries(node const &n) {
			size_t elt_size = sizeof(uint64_t) + n.get_value_size();
			if (elt_size * n.get_max_entries() + sizeof(node_header) > MD_BLOCK_SIZE) {
				std::ostringstream out;
				out << "max entries too large: " << n.get_max_entries();
				report_damage(n, out.str());
				return false;
			}

			if (n.get_max_entries() % 3) {
				std::ostringstream out;
				out << "max entries is not divisible by 3: " << n.get_max_entries();
				report_damage(n, out.str());
				return false;
			}

			return true;
		}

		template <typename node>
		bool check_nr_entries(node const &n, bool is_root) {
			if (n.get_nr_entries() > n.get_max_entries()) {
				std::ostringstream out;
				out << "bad nr_entries: "
				    << n.get_nr_entries() << " < "
				    << n.get_max_entries();
				report_damage(n, out.str());
				return false;
			}

			block_address min = n.get_max_entries() / 3;
			if (!is_root && (n.get_nr_entries() < min)) {
				ostringstream out;
				out << "too few entries in btree: "
				    << n.get_nr_entries()
				    << ", expected at least "
				    << min
				    << "(max_entries = " << n.get_max_entries() << ")";
				report_damage(n, out.str());
				return false;
			}

			return true;
		}

		template <typename node>
		bool check_ordered_keys(node const &n) {
			unsigned nr_entries = n.get_nr_entries();

			if (nr_entries == 0)
				return true; // can only happen if a root node

			uint64_t last_key = n.key_at(0);

			for (unsigned i = 1; i < nr_entries; i++) {
				uint64_t k = n.key_at(i);
				if (k <= last_key) {
					ostringstream out;
					out << "keys are out of order, " << k << " <= " << last_key;
					report_damage(n, out.str());
					return false;
				}
				last_key = k;
			}

			return true;
		}

		template <typename node>
		bool check_parent_key(boost::optional<uint64_t> key, node const &n) {
			if (!key)
				return true;

			if (*key > n.key_at(0)) {
				ostringstream out;
				out << "parent key mismatch: parent was " << *key
				    << ", but lowest in node was " << n.key_at(0);
				report_damage(n, out.str());
				return false;
			}

			return true;
		}

		template <typename node>
		bool check_leaf_key(unsigned level, node const &n) {
			if (n.get_nr_entries() == 0)
				return true; // can only happen if a root node

			if (last_leaf_key_[level] && *last_leaf_key_[level] >= n.key_at(0)) {
				ostringstream out;
				out << "the last key of the previous leaf was " << *last_leaf_key_[level]
				    << " and the first key of this leaf is " << n.key_at(0);
				report_damage(n, out.str());
				return false;
			}

			last_leaf_key_[level] = n.key_at(n.get_nr_entries() - 1);
			return true;
		}

		void new_root(unsigned level) {
			// we're starting a new subtree, so should
			// reset the last_leaf value.
			last_leaf_key_[level] = boost::optional<uint64_t>();
		}

		template <typename node>
		void report_damage(node const &n, std::string const &desc) {
			range<uint64_t> lost_keys;
			damage d(0, lost_keys, desc);
			damage_visitor_.visit(d);
		}

		void report_damage(std::string const &desc) {
			range<uint64_t> lost_keys;
			damage d(0, lost_keys, desc);
			damage_visitor_.visit(d);
		}

		block_counter &counter_;
		bool avoid_repeated_visits_;

		ValueVisitor &value_visitor_;
		DamageVisitor &damage_visitor_;

		std::set<block_address> seen_;
		boost::optional<uint64_t> last_leaf_key_[Levels];
	};
}

//----------------------------------------------------------------

#endif