thin-provisioning-tools/btree_checker.h

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#ifndef BTREE_CHECKER_H
#define BTREE_CHECKER_H
#include "btree.h"
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#include "checksum.h"
#include "error_set.h"
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#include "hex_dump.h"
#include <sstream>
#include <map>
#include <set>
using namespace persistent_data;
using namespace std;
//----------------------------------------------------------------
namespace persistent_data {
//----------------------------------------------------------------
// Little helper class that keeps track of how many times blocks
// are referenced.
//----------------------------------------------------------------
class block_counter {
public:
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typedef std::map<block_address, unsigned> count_map;
void inc(block_address b) {
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count_map::iterator it = counts_.find(b);
if (it == counts_.end())
counts_.insert(make_pair(b, 1));
else
it->second++;
}
unsigned get_count(block_address b) const {
count_map::const_iterator it = counts_.find(b);
return (it == counts_.end()) ? 0 : it->second;
}
count_map const &get_counts() const {
return counts_;
}
private:
count_map counts_;
};
//----------------------------------------------------------------
// This class implements consistency checking for the btrees in
// general. 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
// ---------------
//
// - checksum
// - leaf | internal flags (this can be inferred from siblings)
//----------------------------------------------------------------
template <uint32_t Levels, typename ValueTraits>
class btree_checker : public btree<Levels, ValueTraits>::visitor {
public:
btree_checker(block_counter &counter)
: counter_(counter),
errs_(new error_set("btree errors")) {
}
bool visit_internal(unsigned level,
optional<uint64_t> key,
btree_detail::node_ref<uint64_traits> const &n) {
if (already_visited(n))
return false;
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check_sum(n);
if (!key)
new_root(level);
check_block_nr(n);
check_max_entries(n);
check_nr_entries(n, !key);
check_ordered_keys(n);
check_parent_key(key, n);
return true;
}
bool visit_internal_leaf(unsigned level,
optional<uint64_t> key,
btree_detail::node_ref<uint64_traits> const &n) {
if (already_visited(n))
return false;
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check_sum(n);
if (!key)
new_root(level);
check_block_nr(n);
check_max_entries(n);
check_nr_entries(n, !key);
check_ordered_keys(n);
check_parent_key(key, n);
check_leaf_key(level, n);
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return true;
}
bool visit_leaf(unsigned level,
optional<uint64_t> key,
btree_detail::node_ref<ValueTraits> const &n) {
if (already_visited(n))
return false;
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check_sum(n);
if (!key)
new_root(level);
check_block_nr(n);
check_max_entries(n);
check_nr_entries(n, !key);
check_ordered_keys(n);
check_parent_key(key, n);
check_leaf_key(level, n);
return true;
}
boost::optional<error_set::ptr> get_errors() const {
return errs_;
}
protected:
block_counter &get_counter() {
return counter_;
}
private:
template <typename node>
bool already_visited(node const &n) {
block_address b = n.get_location();
counter_.inc(b);
if (seen_.count(b) > 0)
return true;
seen_.insert(b);
return false;
}
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template <typename node>
void check_sum(node const &n) const {
crc32c sum(BTREE_CSUM_XOR);
disk_node const *data = n.raw();
sum.append(&data->header.flags, MD_BLOCK_SIZE - sizeof(uint32_t));
if (sum.get_sum() != n.get_checksum()) {
std::ostringstream out;
out << "checksum error for block " << n.get_block_nr()
<< ", sum was " << sum.get_sum()
<< ", expected " << n.get_checksum();
errs_->add_child(out.str());
throw runtime_error(out.str());
}
}
template <typename node>
void check_block_nr(node const &n) const {
if (n.get_location() != n.get_block_nr()) {
std::ostringstream out;
out << "block number mismatch: actually "
<< n.get_location()
<< ", claims " << n.get_block_nr();
errs_->add_child(out.str());
throw runtime_error(out.str());
}
}
template <typename node>
void check_max_entries(node const &n) const {
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();
errs_->add_child(out.str());
}
if (n.get_max_entries() % 3) {
std::ostringstream out;
out << "max entries is not divisible by 3: " << n.get_max_entries();
errs_->add_child(out.str());
throw runtime_error(out.str());
}
}
template <typename node>
void check_nr_entries(node const &n, bool is_root) const {
if (n.get_nr_entries() > n.get_max_entries()) {
std::ostringstream out;
out << "bad nr_entries: "
<< n.get_nr_entries() << " < "
<< n.get_max_entries();
errs_->add_child(out.str());
throw std::runtime_error(out.str());
}
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;
errs_->add_child(out.str());
throw runtime_error(out.str());
}
}
template <typename node>
void check_ordered_keys(node const &n) const {
unsigned nr_entries = n.get_nr_entries();
if (nr_entries == 0)
return; // 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;
throw runtime_error(out.str());
}
last_key = k;
}
}
template <typename node>
void check_parent_key(boost::optional<uint64_t> key, node const &n) const {
if (!key)
return;
if (*key > n.key_at(0)) {
ostringstream out;
out << "parent key mismatch: parent was " << *key
<< ", but lowest in node was " << n.key_at(0);
throw runtime_error(out.str());
}
}
template <typename node>
void check_leaf_key(unsigned level, node const &n) {
if (n.get_nr_entries() == 0)
return; // 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);
throw runtime_error(out.str());
}
last_leaf_key_[level] = n.key_at(n.get_nr_entries() - 1);
}
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>();
}
block_counter &counter_;
std::set<block_address> seen_;
error_set::ptr errs_;
boost::optional<uint64_t> last_leaf_key_[Levels];
};
}
//----------------------------------------------------------------
#endif