Merge "Log lock time if it takes too long" into main

#include <sys/types.h>

#include <sys/unistd.h>

#include <chrono>

#include <filesystem>

#include <optional>

#include <thread>

auto SnapshotManager::OpenFile(const std::string& file,

                               int lock_flags) -> std::unique_ptr<LockedFile> {

    const auto start = std::chrono::system_clock::now();

    unique_fd fd(open(file.c_str(), O_RDONLY | O_CLOEXEC | O_NOFOLLOW));

    if (fd < 0) {

        PLOG(ERROR) << "Open failed: " << file;

    // For simplicity, we want to CHECK that lock_mode == LOCK_EX, in some

    // calls, so strip extra flags.

    int lock_mode = lock_flags & (LOCK_EX | LOCK_SH);

    const auto end = std::chrono::system_clock::now();

    const auto duration_ms = std::chrono::duration_cast<std::chrono::milliseconds>(end - start);

    if (duration_ms >= 1000ms) {

        LOG(INFO) << "Taking lock on " << file << " took " << duration_ms.count() << "ms";

    }

    return std::make_unique<LockedFile>(file, std::move(fd), lock_mode);

}