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Keep NAND moves internal and prevent destination overwrite races

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patchzyy
2026-09-07 22:50:13 +02:00
parent 58bfd32022
commit afb8f49866
7 changed files with 224 additions and 85 deletions
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runtime/tests/nand_move_tests.cpp
+64 -12
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@@ -1,6 +1,12 @@
#include "nand_move.h"
#include "nand_file_ops.h"
#include <atomic>
#include <chrono>
#include <fstream>
#include <functional>
#include <iterator>
#include <string>
#include <thread>
#include <iostream>
#include <stdexcept>
@@ -30,6 +36,40 @@ static std::string Read(const fs::path& path) {
return {std::istreambuf_iterator<char>(input), std::istreambuf_iterator<char>()};
}
// Competing moves must have exactly one winner, retain the losing source, and
// publish the winner's complete contents. Exercise both direct and staged moves.
static void CheckCompetingMoves(const fs::path& sourceRoot, const fs::path& destinationRoot) {
const auto left = sourceRoot / "race-left";
const auto right = sourceRoot / "race-right";
const auto target = destinationRoot / "race-target";
const std::string leftBytes(65536, 'L'), rightBytes(65536, 'R');
for (int attempt = 0; attempt < 128; ++attempt) {
Write(left, leftBytes);
Write(right, rightBytes);
std::atomic<int> ready{0};
std::error_code leftError, rightError;
auto move = [&](const fs::path& source, std::error_code& ec) {
++ready;
while (ready.load() != 2) std::this_thread::yield();
NandMove(source, target, ec);
};
std::thread first(move, std::cref(left), std::ref(leftError));
std::thread second(move, std::cref(right), std::ref(rightError));
first.join();
second.join();
Require(bool(leftError) != bool(rightError), "Competing moves must have exactly one winner");
const bool leftWon = !leftError;
Require((leftWon ? rightError : leftError) == std::errc::file_exists,
"Losing move must report an existing destination");
Require(Read(target) == (leftWon ? leftBytes : rightBytes), "Winner's contents were overwritten");
Require(!fs::exists(leftWon ? left : right), "Winning source was not removed");
Require(Read(leftWon ? right : left) == (leftWon ? rightBytes : leftBytes),
"Losing source must remain intact");
fs::remove(leftWon ? right : left);
fs::remove(target);
}
}
int main() {
const auto name = "wiicomp-nand-move-" +
std::to_string(std::chrono::steady_clock::now().time_since_epoch().count());
@@ -41,19 +81,29 @@ int main() {
const auto destination = root / "moved.bin";
std::error_code ec;
Write(source, "banner");
RuntimeNandMove::Move(source, destination, ec);
NandMove(source, destination, ec);
Require(!ec && !fs::exists(source) && Read(destination) == "banner", "Same-device move failed");
CheckCompetingMoves(root, root);
Write(source, "keep source");
RuntimeNandMove::Move(source, destination, ec);
NandMove(source, destination, ec);
Require(ec == std::errc::file_exists && Read(source) == "keep source" && Read(destination) == "banner",
"Existing destination must not be overwritten");
RuntimeNandMove::Move(root / "missing", root / "absent", ec);
NandMove(root / "missing", root / "absent", ec);
Require(bool(ec) && !fs::exists(root / "absent"), "Missing source must fail");
NandMove(source, root / "missing-parent/file", ec);
Require(bool(ec) && Read(source) == "keep source", "Missing parent must preserve source");
fs::create_directory(root / "directory");
Write(root / "directory/child", "child");
RuntimeNandMove::Move(root / "directory", root / "renamed-directory", ec);
NandMove(root / "directory", root / "renamed-directory", ec);
Require(!ec && Read(root / "renamed-directory/child") == "child", "Same-device directory move regressed");
#ifndef _WIN32
fs::create_symlink(root / "missing", root / "same-link");
NandMove(root / "same-link", root / "moved-link", ec);
Require(!ec && fs::is_symlink(fs::symlink_status(root / "moved-link")) &&
!fs::is_symlink(fs::symlink_status(root / "same-link")), "Same-device symlink move regressed");
#endif
#ifdef __linux__
// /dev/shm is a separate tmpfs on ordinary Linux systems, including CI
// and WSL. Fail rather than silently passing without exercising EXDEV.
@@ -62,30 +112,32 @@ int main() {
struct stat left{}, right{};
Require(::stat(root.c_str(), &left) == 0 && ::stat(other.c_str(), &right) == 0 && left.st_dev != right.st_dev,
"Cross-device test requires /tmp and /dev/shm on separate filesystems");
CheckCompetingMoves(root, other);
Require(fs::is_empty(other), "Competing moves left staging files behind");
const auto target = other / "banner.bin";
const std::string bytes = std::string(8192, '\0') + "banner payload";
Write(source, bytes);
fs::rename(source, target, ec);
Require(ec == std::errc::cross_device_link, "Fixture must reproduce the original EXDEV failure");
RuntimeNandMove::Move(source, target, ec);
NandMove(source, target, ec);
Require(!ec && !fs::exists(source) && Read(target) == bytes, "Cross-device move must preserve every byte");
Write(source, "do not overwrite");
RuntimeNandMove::Move(source, target, ec);
NandMove(source, target, ec);
Require(ec == std::errc::file_exists && Read(source) == "do not overwrite" && Read(target) == bytes,
"Cross-device move must preserve an existing destination");
fs::remove(target);
fs::create_symlink(other / "missing", target);
RuntimeNandMove::Move(source, target, ec);
NandMove(source, target, ec);
Require(ec == std::errc::file_exists && fs::is_symlink(target) && Read(source) == "do not overwrite",
"Dangling destination symlink must not be replaced");
fs::remove(target);
RuntimeNandMove::Move(root / "renamed-directory", other / "directory", ec);
NandMove(root / "renamed-directory", other / "directory", ec);
Require(ec == std::errc::cross_device_link && Read(root / "renamed-directory/child") == "child" &&
!fs::exists(other / "directory"), "Unsupported directory move must leave source intact");
fs::create_symlink(source, root / "link");
RuntimeNandMove::Move(root / "link", other / "link", ec);
NandMove(root / "link", other / "link", ec);
Require(ec == std::errc::cross_device_link && fs::is_symlink(root / "link") && !fs::exists(other / "link"),
"Cross-device source symlinks must not be dereferenced");
@@ -97,7 +149,7 @@ int main() {
limited.rlim_cur = 1024;
const auto oldHandler = std::signal(SIGXFSZ, SIG_IGN);
Require(setrlimit(RLIMIT_FSIZE, &limited) == 0, "Cannot set file-size limit");
RuntimeNandMove::Move(source, target, ec);
NandMove(source, target, ec);
const auto copyError = ec;
const auto restored = setrlimit(RLIMIT_FSIZE, &saved);
std::signal(SIGXFSZ, oldHandler);
@@ -107,7 +159,7 @@ int main() {
Require(geteuid() != 0, "Run permission tests as an unprivileged user");
fs::permissions(root, fs::perms::owner_read | fs::perms::owner_exec);
RuntimeNandMove::Move(source, target, ec);
NandMove(source, target, ec);
fs::permissions(root, fs::perms::owner_all);
Require(bool(ec) && Read(source) == bytes && Read(target) == bytes,
"Failed source deletion must leave both complete copies");