nbd: prevent mounted device to unmap

nbd/src/NBDTool.cpp

@@ -27,6 +27,7 @@
 #include <memory>
 #include <string>
 #include "nbd/src/NBDTool.h"
+#include "nbd/src/util.h"
 #include "nbd/src/argparse.h"
 #include "nbd/src/texttable.h"
 
@@ -115,7 +116,12 @@ int NBDTool::Disconnect(const NBDConfig* config) {
     pid_t devpid = -1;
     std::vector<DeviceInfo> devices;
 
-    int ret = List(&devices);
+    auto ret = check_dev_can_unmap(config);
+    if (0 != ret) {
+        return ret;
+    }
+
+    ret = List(&devices);
     for (const auto& device : devices) {
         if (device.config.devpath == config->devpath) {
             devpid = device.pid;

nbd/src/define.h

@@ -89,6 +89,8 @@ struct NBDConfig {
     std::string imgname;
     // 指定需要映射的nbd设备路径
     std::string devpath;
+    // force unmap even if the device is mounted
+    bool force_unmap = false;
     // unmap等待进程退出的重试次数
     int retry_times = 25;
     // unmap重试之间的睡眠间隔

nbd/src/main.cpp

@@ -90,6 +90,7 @@ static void Usage() {
         << "  --block-size            NBD Devices's block size, default is 4096, support 512 and 4096\n"  // NOLINT
         << "  --nebd-conf             LibNebd config file\n"
         << "Unmap options:\n"
+        << "  -f, --force                 Force unmap even if the device is mounted\n"              // NOLINT
         << "  --retry_times <limit>       The number of retries waiting for the process to exit\n"  // NOLINT
         << "                              (default: " << nbdConfig->retry_times << ")\n"            // NOLINT
         << "  --sleep_ms <milliseconds>   Retry interval in milliseconds\n"                         // NOLINT

nbd/src/util.cpp

@@ -201,6 +201,8 @@ int parse_args(std::vector<const char*>& args, std::ostream *err_msg,   // NOLIN
             }
         } else if (argparse_flag(args, i, "--try-netlink", (char *)NULL)) { // NOLINT
             cfg->try_netlink = true;
+        }  else if (argparse_flag(args, i, "-f", "--force", (char *)NULL)) {  // NOLINT
+            cfg->force_unmap = true;
         } else if (argparse_witharg(args, i, &cfg->retry_times, err, "--retry_times", (char*)(NULL))) {  // NOLINT
             if (!err.str().empty()) {
                 *err_msg << "curve-nbd: " << err.str();
@@ -342,6 +344,38 @@ int get_mapped_info(int pid, NBDConfig *cfg) {
     return 0;
 }
 
+int check_dev_can_unmap(const NBDConfig *cfg) {
+    std::ifstream ifs("/proc/mounts", std::ifstream::in);
+
+    if (!ifs.is_open()) {
+        dout << "curve-nbd: failed to open /proc/mounts" << std::endl;
+        return -EINVAL;
+    }
+
+    std::string line, device, mountPath;
+    bool mounted = false;
+    while (std::getline(ifs, line)) {
+        std::istringstream iss(line);
+        iss >> device >> mountPath;
+        if (device == cfg->devpath) {
+            mounted = true;
+            break;
+        }
+    }
+
+    if (!mounted) {
+        return 0;
+    } else if (cfg->force_unmap) {
+        dout << "curve-nbd: the " << device << " is still mount on "
+             << mountPath << ", force unmap it" << std::endl;
+        return 0;
+    }
+
+    dout << "curve-nbd: the " << device << " is still mount on " << mountPath
+         << ", you can't unmap it or specify -f parameter" << std::endl;
+    return -EINVAL;
+}
+
 int check_size_from_file(const std::string& path, uint64_t expected_size) {
     std::ifstream ifs;
     ifs.open(path.c_str(), std::ifstream::in);

nbd/src/util.h

@@ -62,6 +62,8 @@ extern int check_block_size(int nbd_index, uint64_t expected_size);
 extern int check_device_size(int nbd_index, uint64_t expected_size);
 // 如果当前系统还未加载nbd模块，则进行加载；如果已经加载，则不作任何操作
 extern int load_module(NBDConfig *cfg);
+// Check whether the device can be unmap
+int check_dev_can_unmap(const NBDConfig *cfg);
 
 // 安全读写文件或socket，对异常情况进行处理后返回
 ssize_t safe_read_exact(int fd, void* buf, size_t count);