Adding upstream version 18.2.2.upstream/18.2.2

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

13 files changed, 1742 insertions, 0 deletions

diff --git a/src/tools/rbd_ggate/CMakeLists.txt b/src/tools/rbd_ggate/CMakeLists.txt
new file mode 100644
index 000000000..5c5572c48
--- /dev/null
+++ b/src/tools/rbd_ggate/CMakeLists.txt
@@ -0,0 +1,9 @@
+add_executable(rbd-ggate
+  Driver.cc
+  Server.cc
+  Watcher.cc
+  debug.cc
+  ggate_drv.c
+  main.cc)
+target_link_libraries(rbd-ggate geom librbd librados global)
+install(TARGETS rbd-ggate DESTINATION bin)
diff --git a/src/tools/rbd_ggate/Driver.cc b/src/tools/rbd_ggate/Driver.cc
new file mode 100644
index 000000000..80acfe00c
--- /dev/null
+++ b/src/tools/rbd_ggate/Driver.cc
@@ -0,0 +1,165 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#include <stdlib.h>
+
+#include "common/debug.h"
+#include "common/errno.h"
+#include "Driver.h"
+#include "Request.h"
+
+#define dout_context g_ceph_context
+#define dout_subsys ceph_subsys_rbd
+#undef dout_prefix
+#define dout_prefix *_dout << "rbd::ggate::Driver: " << this \
+                           << " " << __func__ << ": "
+
+namespace rbd {
+namespace ggate {
+
+int Driver::load() {
+
+  return ggate_drv_load();
+}
+
+int Driver::kill(const std::string &devname) {
+
+  int r = ggate_drv_kill(devname.c_str());
+
+  return r;
+}
+
+int Driver::list(std::map<std::string, DevInfo> *devices) {
+  size_t size = 1024;
+  ggate_drv_info *devs = nullptr;
+  int r;
+
+  while (size <= 1024 * 1024) {
+    devs = static_cast<ggate_drv_info *>(
+        realloc(static_cast<void *>(devs), size * sizeof(*devs)));
+    r = ggate_drv_list(devs, &size);
+    if (r != -ERANGE) {
+      break;
+    }
+  }
+  if (r < 0) {
+    goto free;
+  }
+
+  devices->clear();
+  for (size_t i = 0; i < size; i++) {
+    auto &dev = devs[i];
+    (*devices)[dev.id] = {dev.name, dev.info};
+  }
+
+free:
+  free(devs);
+
+  return r;
+}
+
+Driver::Driver(const std::string &devname, size_t sectorsize, size_t mediasize,
+               bool readonly, const std::string &info)
+  : m_devname(devname), m_sectorsize(sectorsize), m_mediasize(mediasize),
+    m_readonly(readonly), m_info(info) {
+}
+
+int Driver::init() {
+  dout(20) << dendl;
+
+  char name[PATH_MAX];
+  size_t namelen;
+
+  if (m_devname.empty()) {
+    name[0] = '\0';
+    namelen = PATH_MAX;
+  } else {
+    namelen = m_devname.size();
+    if (namelen >= PATH_MAX) {
+      return -ENAMETOOLONG;
+    }
+    strncpy(name, m_devname.c_str(), namelen + 1);
+  }
+
+  int r = ggate_drv_create(name, namelen, m_sectorsize, m_mediasize, m_readonly,
+                           m_info.c_str(), &m_drv);
+  if (r < 0) {
+    return r;
+  }
+
+  if (m_devname.empty()) {
+    m_devname = name;
+  }
+
+  return 0;
+}
+
+std::string Driver::get_devname() const {
+  dout(30) << m_devname << dendl;
+
+  return m_devname;
+}
+
+void Driver::shut_down() {
+  dout(20) << dendl;
+
+  ggate_drv_destroy(m_drv);
+}
+
+int Driver::resize(size_t newsize) {
+  dout(20) << "newsize=" << newsize << dendl;
+
+  int r = ggate_drv_resize(m_drv, newsize);
+  if (r < 0) {
+    return r;
+  }
+
+  m_mediasize = newsize;
+  return 0;
+}
+
+int Driver::recv(Request **req) {
+  dout(20) << dendl;
+
+  ggate_drv_req_t req_;
+
+  int r = ggate_drv_recv(m_drv, &req_);
+  if (r < 0) {
+    return r;
+  }
+
+  *req = new Request(req_);
+
+  dout(20) << "req=" << *req << dendl;
+
+  if (ggate_drv_req_cmd(req_) == GGATE_DRV_CMD_WRITE) {
+    bufferptr ptr(buffer::claim_malloc(
+                    ggate_drv_req_length(req_),
+                    static_cast<char *>(ggate_drv_req_release_buf(req_))));
+    (*req)->bl.push_back(ptr);
+  }
+
+  return 0;
+}
+
+int Driver::send(Request *req) {
+  dout(20) << "req=" << req << dendl;
+
+  if (ggate_drv_req_cmd(req->req) == GGATE_DRV_CMD_READ &&
+      ggate_drv_req_error(req->req) == 0) {
+    ceph_assert(req->bl.length() == ggate_drv_req_length(req->req));
+    // TODO: avoid copying?
+    req->bl.begin().copy(ggate_drv_req_length(req->req),
+                 static_cast<char *>(ggate_drv_req_buf(req->req)));
+    dout(20) << "copied resulting " << req->bl.length() << " bytes to "
+             << ggate_drv_req_buf(req->req) << dendl;
+  }
+
+  int r = ggate_drv_send(m_drv, req->req);
+
+  delete req;
+  return r;
+}
+
+} // namespace ggate
+} // namespace rbd
diff --git a/src/tools/rbd_ggate/Driver.h b/src/tools/rbd_ggate/Driver.h
new file mode 100644
index 000000000..50be72b9c
--- /dev/null
+++ b/src/tools/rbd_ggate/Driver.h
@@ -0,0 +1,50 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#ifndef CEPH_RBD_GGATE_DRIVER_H
+#define CEPH_RBD_GGATE_DRIVER_H
+
+#include <map>
+#include <string>
+
+#include "ggate_drv.h"
+
+namespace rbd {
+namespace ggate {
+
+struct Request;
+
+class Driver {
+public:
+  typedef std::pair<std::string, std::string> DevInfo;
+  static int load();
+  static int kill(const std::string &devname);
+  static int list(std::map<std::string, DevInfo> *devices);
+
+  Driver(const std::string &devname, size_t sectorsize, size_t mediasize,
+         bool readonly, const std::string &info);
+
+  int init();
+  void shut_down();
+
+  std::string get_devname() const;
+
+  int recv(Request **req);
+  int send(Request *req);
+
+  int resize(size_t newsize);
+
+private:
+  std::string m_devname;
+  size_t m_sectorsize;
+  size_t m_mediasize;
+  bool m_readonly;
+  std::string m_info;
+  ggate_drv_t m_drv = 0;
+};
+
+} // namespace ggate
+} // namespace rbd
+
+#endif // CEPH_RBD_GGATE_DRIVER_H
+
diff --git a/src/tools/rbd_ggate/Request.h b/src/tools/rbd_ggate/Request.h
new file mode 100644
index 000000000..66f219858
--- /dev/null
+++ b/src/tools/rbd_ggate/Request.h
@@ -0,0 +1,55 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#ifndef CEPH_RBD_GGATE_REQUEST_H
+#define CEPH_RBD_GGATE_REQUEST_H
+
+#include "ggate_drv.h"
+
+namespace rbd {
+namespace ggate {
+
+struct Request {
+  enum Command {
+    Unknown = 0,
+    Write = 1,
+    Read = 2,
+    Flush = 3,
+    Discard = 4,
+  };
+
+  ggate_drv_req_t req;
+  bufferlist bl;
+
+  Request(ggate_drv_req_t req) : req(req) {
+  }
+
+  uint64_t get_id() {
+    return ggate_drv_req_id(req);
+  }
+
+  Command get_cmd() {
+    return static_cast<Command>(ggate_drv_req_cmd(req));
+  }
+
+  size_t get_length() {
+    return ggate_drv_req_length(req);
+  }
+
+  uint64_t get_offset() {
+    return ggate_drv_req_offset(req);
+  }
+
+  uint64_t get_error() {
+    return ggate_drv_req_error(req);
+  }
+
+  void set_error(int error) {
+    ggate_drv_req_set_error(req, error);
+  }
+};
+
+} // namespace ggate
+} // namespace rbd
+
+#endif // CEPH_RBD_GGATE_REQUEST_H
diff --git a/src/tools/rbd_ggate/Server.cc b/src/tools/rbd_ggate/Server.cc
new file mode 100644
index 000000000..2565ba10f
--- /dev/null
+++ b/src/tools/rbd_ggate/Server.cc
@@ -0,0 +1,262 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#include "common/debug.h"
+#include "common/errno.h"
+#include "Driver.h"
+#include "Server.h"
+#include "Request.h"
+
+#define dout_context g_ceph_context
+#define dout_subsys ceph_subsys_rbd
+#undef dout_prefix
+#define dout_prefix *_dout << "rbd::ggate::Server: " << this \
+                           << " " << __func__ << ": "
+
+namespace rbd {
+namespace ggate {
+
+Server::Server(Driver *drv, librbd::Image& image)
+  : m_drv(drv), m_image(image),
+    m_reader_thread(this, &Server::reader_entry),
+    m_writer_thread(this, &Server::writer_entry) {
+}
+
+void Server::run() {
+  dout(10) << dendl;
+
+  int r = start();
+  ceph_assert(r == 0);
+
+  dout(20) << "entering run loop" << dendl;
+
+  {
+    std::unique_lock locker{m_lock};
+    m_cond.wait(locker, [this] { return m_stopping;});
+  }
+
+  dout(20) << "exiting run loop" << dendl;
+
+  stop();
+}
+
+int Server::start() {
+  dout(10) << dendl;
+
+  m_reader_thread.create("rbd_reader");
+  m_writer_thread.create("rbd_writer");
+  return 0;
+}
+
+void Server::stop() {
+  dout(10) << dendl;
+
+  {
+    std::lock_guard locker{m_lock};
+    ceph_assert(m_stopping);
+  }
+
+  m_reader_thread.join();
+  m_writer_thread.join();
+
+  wait_clean();
+}
+
+void Server::io_start(IOContext *ctx) {
+  dout(20) << ctx << dendl;
+
+  std::lock_guard locker{m_lock};
+  m_io_pending.push_back(&ctx->item);
+}
+
+void Server::io_finish(IOContext *ctx) {
+  dout(20) << ctx << dendl;
+
+  std::lock_guard locker{m_lock};
+  ceph_assert(ctx->item.is_on_list());
+
+  ctx->item.remove_myself();
+  m_io_finished.push_back(&ctx->item);
+  m_cond.notify_all();
+}
+
+Server::IOContext *Server::wait_io_finish() {
+  dout(20) << dendl;
+
+  std::unique_lock locker{m_lock};
+  m_cond.wait(locker, [this] { return !m_io_finished.empty() || m_stopping;});
+
+  if (m_io_finished.empty()) {
+    return nullptr;
+  }
+
+  IOContext *ret = m_io_finished.front();
+  m_io_finished.pop_front();
+
+  return ret;
+}
+
+void Server::wait_clean() {
+  dout(20) << dendl;
+
+  ceph_assert(!m_reader_thread.is_started());
+
+  std::unique_lock locker{m_lock};
+  m_cond.wait(locker, [this] { return m_io_pending.empty();});
+
+  while (!m_io_finished.empty()) {
+    std::unique_ptr<IOContext> free_ctx(m_io_finished.front());
+    m_io_finished.pop_front();
+  }
+}
+
+void Server::aio_callback(librbd::completion_t cb, void *arg) {
+  librbd::RBD::AioCompletion *aio_completion =
+    reinterpret_cast<librbd::RBD::AioCompletion*>(cb);
+
+  IOContext *ctx = reinterpret_cast<IOContext *>(arg);
+  int r = aio_completion->get_return_value();
+
+  ctx->server->handle_aio(ctx, r);
+  aio_completion->release();
+}
+
+void Server::handle_aio(IOContext *ctx, int r) {
+  dout(20) << ctx << ": r=" << r << dendl;
+
+  if (r == -EINVAL) {
+    // if shrinking an image, a pagecache writeback might reference
+    // extents outside of the range of the new image extents
+    dout(5) << "masking IO out-of-bounds error" << dendl;
+    ctx->req->bl.clear();
+    r = 0;
+  }
+
+  if (r < 0) {
+    ctx->req->set_error(-r);
+  } else if ((ctx->req->get_cmd() == Request::Read) &&
+             r != static_cast<int>(ctx->req->get_length())) {
+    int pad_byte_count = static_cast<int> (ctx->req->get_length()) - r;
+    ctx->req->bl.append_zero(pad_byte_count);
+    dout(20) << ctx << ": pad byte count: " << pad_byte_count << dendl;
+    ctx->req->set_error(0);
+  } else {
+    ctx->req->set_error(0);
+  }
+  io_finish(ctx);
+}
+
+void Server::reader_entry() {
+  dout(20) << dendl;
+
+  while (!m_stopping) {
+    std::unique_ptr<IOContext> ctx(new IOContext(this));
+
+    dout(20) << "waiting for ggate request" << dendl;
+
+    int r = m_drv->recv(&ctx->req);
+    if (r < 0) {
+      if (r != -ECANCELED) {
+        derr << "recv: " << cpp_strerror(r) << dendl;
+      }
+      std::lock_guard locker{m_lock};
+      m_stopping = true;
+      m_cond.notify_all();
+      return;
+    }
+
+    IOContext *pctx = ctx.release();
+
+    dout(20) << pctx << ": start: " << *pctx << dendl;
+
+    io_start(pctx);
+    librbd::RBD::AioCompletion *c =
+      new librbd::RBD::AioCompletion(pctx, aio_callback);
+    switch (pctx->req->get_cmd())
+    {
+    case rbd::ggate::Request::Write:
+      m_image.aio_write(pctx->req->get_offset(), pctx->req->get_length(),
+                        pctx->req->bl, c);
+      break;
+    case rbd::ggate::Request::Read:
+      m_image.aio_read(pctx->req->get_offset(), pctx->req->get_length(),
+                       pctx->req->bl, c);
+      break;
+    case rbd::ggate::Request::Flush:
+      m_image.aio_flush(c);
+      break;
+    case rbd::ggate::Request::Discard:
+      m_image.aio_discard(pctx->req->get_offset(), pctx->req->get_length(), c);
+      break;
+    default:
+      derr << pctx << ": invalid request command: " << pctx->req->get_cmd()
+           << dendl;
+      c->release();
+      std::lock_guard locker{m_lock};
+      m_stopping = true;
+      m_cond.notify_all();
+      return;
+    }
+  }
+  dout(20) << "terminated" << dendl;
+}
+
+void Server::writer_entry() {
+  dout(20) << dendl;
+
+  while (!m_stopping) {
+    dout(20) << "waiting for io request" << dendl;
+
+    std::unique_ptr<IOContext> ctx(wait_io_finish());
+    if (!ctx) {
+      dout(20) << "no io requests, terminating" << dendl;
+      return;
+    }
+
+    dout(20) << ctx.get() << ": got: " << *ctx << dendl;
+
+    int r = m_drv->send(ctx->req);
+    if (r < 0) {
+      derr << ctx.get() << ": send: " << cpp_strerror(r) << dendl;
+      std::lock_guard locker{m_lock};
+      m_stopping = true;
+      m_cond.notify_all();
+      return;
+    }
+    dout(20) << ctx.get() << " finish" << dendl;
+  }
+  dout(20) << "terminated" << dendl;
+}
+
+std::ostream &operator<<(std::ostream &os, const Server::IOContext &ctx) {
+
+  os << "[" << ctx.req->get_id();
+
+  switch (ctx.req->get_cmd())
+  {
+  case rbd::ggate::Request::Write:
+    os << " Write ";
+    break;
+  case rbd::ggate::Request::Read:
+    os << " Read ";
+    break;
+  case rbd::ggate::Request::Flush:
+    os << " Flush ";
+    break;
+  case rbd::ggate::Request::Discard:
+    os << " Discard ";
+    break;
+  default:
+    os << " Unknow(" << ctx.req->get_cmd() << ") ";
+    break;
+  }
+
+  os << ctx.req->get_offset() << "~" << ctx.req->get_length() << " "
+     << ctx.req->get_error() << "]";
+
+  return os;
+}
+
+} // namespace ggate
+} // namespace rbd
+
diff --git a/src/tools/rbd_ggate/Server.h b/src/tools/rbd_ggate/Server.h
new file mode 100644
index 000000000..bb31b89f7
--- /dev/null
+++ b/src/tools/rbd_ggate/Server.h
@@ -0,0 +1,88 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#ifndef CEPH_RBD_GGATE_SERVER_H
+#define CEPH_RBD_GGATE_SERVER_H
+
+#include "include/rbd/librbd.hpp"
+#include "include/xlist.h"
+#include "common/ceph_mutex.h"
+#include "common/Thread.h"
+
+namespace rbd {
+namespace ggate {
+
+class Driver;
+struct Request;
+
+class Server {
+public:
+  Server(Driver *drv, librbd::Image& image);
+
+  void run();
+
+private:
+  struct IOContext {
+    xlist<IOContext*>::item item;
+    Server *server;
+    Request *req = nullptr;
+
+    IOContext(Server *server) : item(this), server(server) {
+    }
+  };
+
+  class ThreadHelper : public Thread {
+  public:
+    typedef void (Server::*entry_func)();
+
+    ThreadHelper(Server *server, entry_func func)
+      : server(server), func(func) {
+    }
+
+  protected:
+    virtual void* entry() {
+      (server->*func)();
+      return nullptr;
+    }
+
+  private:
+    Server *server;
+    entry_func func;
+  };
+
+  friend std::ostream &operator<<(std::ostream &os, const IOContext &ctx);
+
+  Driver *m_drv;
+  librbd::Image &m_image;
+
+  mutable ceph::mutex m_lock =
+    ceph::make_mutex("rbd::ggate::Server::m_lock");
+  ceph::condition_variable m_cond;
+  bool m_stopping = false;
+  ThreadHelper m_reader_thread, m_writer_thread;
+  xlist<IOContext*> m_io_pending;
+  xlist<IOContext*> m_io_finished;
+
+  static void aio_callback(librbd::completion_t cb, void *arg);
+
+  int start();
+  void stop();
+
+  void reader_entry();
+  void writer_entry();
+
+  void io_start(IOContext *ctx);
+  void io_finish(IOContext *ctx);
+
+  IOContext *wait_io_finish();
+  void wait_clean();
+
+  void handle_aio(IOContext *ctx, int r);
+};
+
+std::ostream &operator<<(std::ostream &os, const Server::IOContext &ctx);
+
+} // namespace ggate
+} // namespace rbd
+
+#endif // CEPH_RBD_GGATE_SERVER_H
diff --git a/src/tools/rbd_ggate/Watcher.cc b/src/tools/rbd_ggate/Watcher.cc
new file mode 100644
index 000000000..57b3f960e
--- /dev/null
+++ b/src/tools/rbd_ggate/Watcher.cc
@@ -0,0 +1,48 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#include "common/debug.h"
+#include "common/errno.h"
+#include "Driver.h"
+#include "Watcher.h"
+
+#define dout_context g_ceph_context
+#define dout_subsys ceph_subsys_rbd
+#undef dout_prefix
+#define dout_prefix *_dout << "rbd::ggate::Watcher: " << this \
+                           << " " << __func__ << ": "
+
+namespace rbd {
+namespace ggate {
+
+Watcher::Watcher(Driver *drv, librados::IoCtx &ioctx, librbd::Image &image,
+                 size_t size)
+  : m_drv(drv), m_ioctx(ioctx), m_image(image), m_size(size) {
+}
+
+void Watcher::handle_notify() {
+  dout(20) << dendl;
+
+  librbd::image_info_t info;
+
+  if (m_image.stat(info, sizeof(info)) == 0) {
+    size_t new_size = info.size;
+
+    if (new_size != m_size) {
+      int r = m_drv->resize(new_size);
+      if (r < 0) {
+        derr << "resize failed: " << cpp_strerror(r) << dendl;
+        m_drv->shut_down();
+      }
+      r = m_image.invalidate_cache();
+      if (r < 0) {
+        derr << "invalidate rbd cache failed: " << cpp_strerror(r) << dendl;
+        m_drv->shut_down();
+      }
+      m_size = new_size;
+    }
+  }
+}
+
+} // namespace ggate
+} // namespace rbd
diff --git a/src/tools/rbd_ggate/Watcher.h b/src/tools/rbd_ggate/Watcher.h
new file mode 100644
index 000000000..8f524b43f
--- /dev/null
+++ b/src/tools/rbd_ggate/Watcher.h
@@ -0,0 +1,34 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#ifndef CEPH_RBD_GGATE_WATCHER_H
+#define CEPH_RBD_GGATE_WATCHER_H
+
+#include "include/rbd/librbd.hpp"
+
+namespace rbd {
+namespace ggate {
+
+class Driver;
+
+class Watcher : public librbd::UpdateWatchCtx
+{
+public:
+  Watcher(Driver *m_drv, librados::IoCtx &ioctx, librbd::Image &image,
+          size_t size);
+
+  void handle_notify() override;
+
+private:
+  Driver *m_drv;
+  librados::IoCtx &m_ioctx;
+  librbd::Image &m_image;
+  size_t m_size;
+};
+
+
+} // namespace ggate
+} // namespace rbd
+
+#endif // CEPH_RBD_GGATE_WATCHER_H
+
diff --git a/src/tools/rbd_ggate/debug.cc b/src/tools/rbd_ggate/debug.cc
new file mode 100644
index 000000000..b675ba5b3
--- /dev/null
+++ b/src/tools/rbd_ggate/debug.cc
@@ -0,0 +1,55 @@
+#include "common/debug.h"
+#include "common/errno.h"
+#include "debug.h"
+
+#define dout_context g_ceph_context
+#define dout_subsys ceph_subsys_rbd
+#undef dout_prefix
+#define dout_prefix *_dout << "rbd::ggate: "
+
+extern "C" void debugv(int level, const char *fmt, va_list ap) {
+    char *msg;
+    int saved_errno = errno;
+
+    if (g_ceph_context == nullptr) {
+        return;
+    }
+
+    vasprintf(&msg, fmt, ap);
+
+    dout(ceph::dout::need_dynamic(level)) << msg << dendl;
+
+    free(msg);
+    errno = saved_errno;
+}
+
+extern "C" void debug(int level, const char *fmt, ...) {
+    va_list ap;
+
+    va_start(ap, fmt);
+    debugv(level, fmt, ap);
+    va_end(ap);
+}
+
+extern "C" void errx(const char *fmt, ...) {
+    va_list ap;
+
+    va_start(ap, fmt);
+    debugv(-1, fmt, ap);
+    va_end(ap);
+}
+
+extern "C" void err(const char *fmt, ...) {
+    va_list ap;
+    char *msg;
+    int saved_errno = errno;
+
+    va_start(ap, fmt);
+    vasprintf(&msg, fmt, ap);
+    va_end(ap);
+    errno = saved_errno;
+
+    errx("%s: %s", msg, cpp_strerror(errno).c_str());
+
+    free(msg);
+}
diff --git a/src/tools/rbd_ggate/debug.h b/src/tools/rbd_ggate/debug.h
new file mode 100644
index 000000000..da9b46a38
--- /dev/null
+++ b/src/tools/rbd_ggate/debug.h
@@ -0,0 +1,17 @@
+#ifndef CEPH_RBD_GGATE_DEBUG_H
+#define CEPH_RBD_GGATE_DEBUG_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+void debug(int level, const char *fmt, ...) __printflike(2, 3);
+void debugv(int level, const char *fmt, va_list ap) __printflike(2, 0);
+void err(const char *fmt, ...) __printflike(1, 2);
+void errx(const char *fmt, ...) __printflike(1, 2);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // CEPH_RBD_GGATE_DEBUG_H
diff --git a/src/tools/rbd_ggate/ggate_drv.c b/src/tools/rbd_ggate/ggate_drv.c
new file mode 100644
index 000000000..11f6cf0a4
--- /dev/null
+++ b/src/tools/rbd_ggate/ggate_drv.c
@@ -0,0 +1,379 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#include <sys/param.h>
+#include <sys/bio.h>
+#include <sys/disk.h>
+#include <sys/linker.h>
+#include <sys/queue.h>
+#include <sys/stat.h>
+
+#include <geom/gate/g_gate.h>
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <libgeom.h>
+
+#include "debug.h"
+#include "ggate_drv.h"
+
+uint64_t ggate_drv_req_id(ggate_drv_req_t req) {
+  struct g_gate_ctl_io *ggio = (struct g_gate_ctl_io *)req;
+
+  return ggio->gctl_seq;
+}
+
+int ggate_drv_req_cmd(ggate_drv_req_t req) {
+  struct g_gate_ctl_io *ggio = (struct g_gate_ctl_io *)req;
+
+  switch (ggio->gctl_cmd) {
+  case BIO_WRITE:
+    return GGATE_DRV_CMD_WRITE;
+  case BIO_READ:
+    return GGATE_DRV_CMD_READ;
+  case BIO_FLUSH:
+    return GGATE_DRV_CMD_FLUSH;
+  case BIO_DELETE:
+    return GGATE_DRV_CMD_DISCARD;
+  default:
+    return GGATE_DRV_CMD_UNKNOWN;
+  }
+}
+
+uint64_t ggate_drv_req_offset(ggate_drv_req_t req) {
+  struct g_gate_ctl_io *ggio = (struct g_gate_ctl_io *)req;
+
+  return ggio->gctl_offset;
+}
+
+size_t ggate_drv_req_length(ggate_drv_req_t req) {
+  struct g_gate_ctl_io *ggio = (struct g_gate_ctl_io *)req;
+
+  return ggio->gctl_length;
+}
+
+void *ggate_drv_req_buf(ggate_drv_req_t req) {
+  struct g_gate_ctl_io *ggio = (struct g_gate_ctl_io *)req;
+
+  return ggio->gctl_data;
+}
+
+int ggate_drv_req_error(ggate_drv_req_t req) {
+  struct g_gate_ctl_io *ggio = (struct g_gate_ctl_io *)req;
+
+  return ggio->gctl_error;
+}
+
+void ggate_drv_req_set_error(ggate_drv_req_t req, int error) {
+  struct g_gate_ctl_io *ggio = (struct g_gate_ctl_io *)req;
+
+  ggio->gctl_error = error;
+}
+
+void *ggate_drv_req_release_buf(ggate_drv_req_t req) {
+  struct g_gate_ctl_io *ggio = (struct g_gate_ctl_io *)req;
+
+  void *data = ggio->gctl_data;
+  ggio->gctl_data = NULL;
+
+  return data;
+}
+
+struct ggate_drv {
+  int fd;
+  int unit;
+};
+
+int ggate_drv_load() {
+  if (modfind("g_gate") != -1) {
+    /* Present in kernel. */
+    return 0;
+  }
+
+  if (kldload("geom_gate") == -1 || modfind("g_gate") == -1) {
+    if (errno != EEXIST) {
+      err("failed to load geom_gate module");
+      return -errno;
+    }
+  }
+  return 0;
+}
+
+int ggate_drv_create(char *name, size_t namelen, size_t sectorsize,
+    size_t mediasize, bool readonly, const char *info, ggate_drv_t *drv_) {
+  struct ggate_drv *drv;
+  struct g_gate_ctl_create ggiocreate;
+
+  debug(20, "%s: name=%s, sectorsize=%zd, mediasize=%zd, readonly=%d, info=%s",
+      __func__, name, sectorsize, mediasize, (int)readonly, info);
+
+  if (*name != '\0') {
+    if (namelen > sizeof(ggiocreate.gctl_name) - 1) {
+      return -ENAMETOOLONG;
+    }
+  }
+
+  /*
+   * We communicate with ggate via /dev/ggctl. Open it.
+   */
+  int fd = open("/dev/" G_GATE_CTL_NAME, O_RDWR);
+  if (fd == -1) {
+    err("failed to open /dev/" G_GATE_CTL_NAME);
+    return -errno;
+  }
+
+  drv = calloc(1, sizeof(*drv));
+  if (drv == NULL) {
+    errno = -ENOMEM;
+    goto fail_close;
+  }
+
+  /*
+   * Create provider.
+   */
+  memset(&ggiocreate, 0, sizeof(ggiocreate));
+  ggiocreate.gctl_version = G_GATE_VERSION;
+  ggiocreate.gctl_mediasize = mediasize;
+  ggiocreate.gctl_sectorsize = sectorsize;
+  ggiocreate.gctl_flags = readonly ? G_GATE_FLAG_READONLY : 0;
+  ggiocreate.gctl_maxcount = 0;
+  ggiocreate.gctl_timeout = 0;
+  if (*name != '\0') {
+    ggiocreate.gctl_unit = G_GATE_NAME_GIVEN;
+    strlcpy(ggiocreate.gctl_name, name, sizeof(ggiocreate.gctl_name));
+  } else {
+    ggiocreate.gctl_unit = G_GATE_UNIT_AUTO;
+  }
+  strlcpy(ggiocreate.gctl_info, info, sizeof(ggiocreate.gctl_info));
+  if (ioctl(fd, G_GATE_CMD_CREATE, &ggiocreate) == -1) {
+    err("failed to create " G_GATE_PROVIDER_NAME " device");
+    goto fail;
+  }
+
+  debug(20, "%s: created, unit: %d, name: %s", __func__, ggiocreate.gctl_unit,
+      ggiocreate.gctl_name);
+
+  drv->fd = fd;
+  drv->unit = ggiocreate.gctl_unit;
+  *drv_ = drv;
+
+  if (*name == '\0') {
+    snprintf(name, namelen, "%s%d", G_GATE_PROVIDER_NAME, drv->unit);
+  }
+
+  return 0;
+
+fail:
+  free(drv);
+fail_close:
+  close(fd);
+  return -errno;
+}
+
+void ggate_drv_destroy(ggate_drv_t drv_) {
+  struct ggate_drv *drv = (struct ggate_drv *)drv_;
+  struct g_gate_ctl_destroy ggiodestroy;
+
+  debug(20, "%s %p", __func__, drv);
+
+  memset(&ggiodestroy, 0, sizeof(ggiodestroy));
+  ggiodestroy.gctl_version = G_GATE_VERSION;
+  ggiodestroy.gctl_unit = drv->unit;
+  ggiodestroy.gctl_force = 1;
+
+  // Remember errno.
+  int rerrno = errno;
+
+  int r = ioctl(drv->fd, G_GATE_CMD_DESTROY, &ggiodestroy);
+  if (r == -1) {
+    err("failed to destroy /dev/%s%d device", G_GATE_PROVIDER_NAME,
+        drv->unit);
+  }
+  // Restore errno.
+  errno = rerrno;
+
+  free(drv);
+}
+
+int ggate_drv_resize(ggate_drv_t drv_, size_t newsize) {
+  struct ggate_drv *drv = (struct ggate_drv *)drv_;
+
+  debug(20, "%s %p: newsize=%zd", __func__, drv, newsize);
+
+  struct g_gate_ctl_modify ggiomodify;
+
+  memset(&ggiomodify, 0, sizeof(ggiomodify));
+  ggiomodify.gctl_version = G_GATE_VERSION;
+  ggiomodify.gctl_unit = drv->unit;
+  ggiomodify.gctl_modify = GG_MODIFY_MEDIASIZE;
+  ggiomodify.gctl_mediasize = newsize;
+
+  int r = ioctl(drv->fd, G_GATE_CMD_MODIFY, &ggiomodify);
+  if (r == -1) {
+    r = -errno;
+    err("failed to resize /dev/%s%d device", G_GATE_PROVIDER_NAME, drv->unit);
+  }
+  return r;
+}
+
+int ggate_drv_kill(const char *devname) {
+  debug(20, "%s %s", __func__, devname);
+
+  int fd = open("/dev/" G_GATE_CTL_NAME, O_RDWR);
+  if (fd == -1) {
+    err("failed to open /dev/" G_GATE_CTL_NAME);
+    return -errno;
+  }
+
+  struct g_gate_ctl_destroy ggiodestroy;
+  memset(&ggiodestroy, 0, sizeof(ggiodestroy));
+  ggiodestroy.gctl_version = G_GATE_VERSION;
+  ggiodestroy.gctl_unit = G_GATE_NAME_GIVEN;
+  ggiodestroy.gctl_force = 1;
+
+  strlcpy(ggiodestroy.gctl_name, devname, sizeof(ggiodestroy.gctl_name));
+
+  int r = ioctl(fd, G_GATE_CMD_DESTROY, &ggiodestroy);
+  if (r == -1) {
+    r = -errno;
+    err("failed to destroy %s device", devname);
+  }
+
+  close(fd);
+  return r;
+}
+
+int ggate_drv_recv(ggate_drv_t drv_, ggate_drv_req_t *req) {
+  struct ggate_drv *drv = (struct ggate_drv *)drv_;
+  struct g_gate_ctl_io *ggio;
+  int error, r;
+
+  debug(20, "%s", __func__);
+
+  ggio = calloc(1, sizeof(*ggio));
+  if (ggio == NULL) {
+    return -ENOMEM;
+  }
+
+  ggio->gctl_version = G_GATE_VERSION;
+  ggio->gctl_unit = drv->unit;
+  ggio->gctl_data = malloc(MAXPHYS);
+  ggio->gctl_length = MAXPHYS;
+
+  debug(20, "%s: waiting for request from kernel",  __func__);
+  if (ioctl(drv->fd, G_GATE_CMD_START, ggio) == -1) {
+    err("%s: G_GATE_CMD_START failed", __func__);
+    return -errno;
+  }
+
+  debug(20, "%s: got request from kernel: "
+        "unit=%d, seq=%ju, cmd=%u, offset=%ju, length=%ju, error=%d, data=%p",
+        __func__, ggio->gctl_unit, (uintmax_t)ggio->gctl_seq, ggio->gctl_cmd,
+        (uintmax_t)ggio->gctl_offset, (uintmax_t)ggio->gctl_length,
+        ggio->gctl_error, ggio->gctl_data);
+
+  error = ggio->gctl_error;
+  switch (error) {
+  case 0:
+    break;
+  case ECANCELED:
+    debug(10, "%s: canceled: exit gracefully",  __func__);
+    r = -error;
+    goto fail;
+  case ENOMEM:
+    /*
+     * Buffer too small? Impossible, we allocate MAXPHYS
+     * bytes - request can't be bigger than that.
+     */
+    /* FALLTHROUGH */
+  case ENXIO:
+  default:
+    errno = error;
+    err("%s: G_GATE_CMD_START failed", __func__);
+    r = -error;
+    goto fail;
+  }
+
+  *req = ggio;
+  return 0;
+
+fail:
+  free(ggio->gctl_data);
+  free(ggio);
+  return r;
+}
+
+int ggate_drv_send(ggate_drv_t drv_, ggate_drv_req_t req) {
+  struct ggate_drv *drv = (struct ggate_drv *)drv_;
+  struct g_gate_ctl_io *ggio = (struct g_gate_ctl_io *)req;
+  int r = 0;
+
+  debug(20, "%s: send request to kernel: "
+        "unit=%d, seq=%ju, cmd=%u, offset=%ju, length=%ju, error=%d, data=%p",
+        __func__, ggio->gctl_unit, (uintmax_t)ggio->gctl_seq, ggio->gctl_cmd,
+        (uintmax_t)ggio->gctl_offset, (uintmax_t)ggio->gctl_length,
+        ggio->gctl_error, ggio->gctl_data);
+
+  if (ioctl(drv->fd, G_GATE_CMD_DONE, ggio) == -1) {
+    err("%s: G_GATE_CMD_DONE failed", __func__);
+    r = -errno;
+  }
+
+  free(ggio->gctl_data);
+  free(ggio);
+  return r;
+}
+
+static const char * get_conf(struct ggeom *gp, const char *name) {
+	struct gconfig *conf;
+
+	LIST_FOREACH(conf, &gp->lg_config, lg_config) {
+		if (strcmp(conf->lg_name, name) == 0)
+			return (conf->lg_val);
+	}
+	return "";
+}
+
+int ggate_drv_list(struct ggate_drv_info *info, size_t *size) {
+  struct gmesh mesh;
+  struct gclass *class;
+  struct ggeom *gp;
+  int r;
+  size_t max_size;
+
+  r = geom_gettree(&mesh);
+  if (r != 0) {
+    return -errno;
+  }
+
+  max_size = *size;
+  *size = 0;
+
+  LIST_FOREACH(class, &mesh.lg_class, lg_class) {
+    if (strcmp(class->lg_name, G_GATE_CLASS_NAME) == 0) {
+      LIST_FOREACH(gp, &class->lg_geom, lg_geom) {
+        (*size)++;
+      }
+      if (*size > max_size) {
+        r = -ERANGE;
+        goto done;
+      }
+      LIST_FOREACH(gp, &class->lg_geom, lg_geom) {
+        strlcpy(info->id, get_conf(gp, "unit"), sizeof(info->id));
+        strlcpy(info->name, gp->lg_name, sizeof(info->name));
+        strlcpy(info->info, get_conf(gp, "info"), sizeof(info->info));
+        info++;
+      }
+    }
+  }
+
+done:
+  geom_deletetree(&mesh);
+  return r;
+}
diff --git a/src/tools/rbd_ggate/ggate_drv.h b/src/tools/rbd_ggate/ggate_drv.h
new file mode 100644
index 000000000..69268ebd4
--- /dev/null
+++ b/src/tools/rbd_ggate/ggate_drv.h
@@ -0,0 +1,64 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#ifndef CEPH_RBD_GGATE_GGATE_DRV_H
+#define CEPH_RBD_GGATE_GGATE_DRV_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <sys/param.h>
+
+#include <stdbool.h>
+#include <stdint.h>
+
+typedef void *ggate_drv_t;
+typedef void *ggate_drv_req_t;
+
+/*
+ * GGATE driver commands. They are mapped to GgateReq::Command.
+ */
+enum {
+  GGATE_DRV_CMD_UNKNOWN = 0,
+  GGATE_DRV_CMD_WRITE = 1,
+  GGATE_DRV_CMD_READ = 2,
+  GGATE_DRV_CMD_FLUSH = 3,
+  GGATE_DRV_CMD_DISCARD = 4,
+};
+
+struct ggate_drv_info {
+  char id[16];
+  char name[NAME_MAX];
+  char info[2048]; /* G_GATE_INFOSIZE */
+};
+
+uint64_t ggate_drv_req_id(ggate_drv_req_t req);
+int ggate_drv_req_cmd(ggate_drv_req_t req);
+void *ggate_drv_req_buf(ggate_drv_req_t req);
+size_t ggate_drv_req_length(ggate_drv_req_t req);
+uint64_t ggate_drv_req_offset(ggate_drv_req_t req);
+int ggate_drv_req_error(ggate_drv_req_t req);
+
+void ggate_drv_req_set_error(ggate_drv_req_t req, int error);
+void *ggate_drv_req_release_buf(ggate_drv_req_t req);
+
+int ggate_drv_load();
+
+int ggate_drv_create(char *name, size_t namelen, size_t sectorsize,
+    size_t mediasize, bool readonly, const char *info, ggate_drv_t *drv);
+void ggate_drv_destroy(ggate_drv_t drv);
+
+int ggate_drv_recv(ggate_drv_t drv, ggate_drv_req_t *req);
+int ggate_drv_send(ggate_drv_t drv, ggate_drv_req_t req);
+
+int ggate_drv_resize(ggate_drv_t drv, size_t newsize);
+
+int ggate_drv_kill(const char *devname);
+int ggate_drv_list(struct ggate_drv_info *info, size_t *size);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // CEPH_RBD_GGATE_GGATE_DRV_H
diff --git a/src/tools/rbd_ggate/main.cc b/src/tools/rbd_ggate/main.cc
new file mode 100644
index 000000000..0942f5689
--- /dev/null
+++ b/src/tools/rbd_ggate/main.cc
@@ -0,0 +1,516 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#include "include/int_types.h"
+
+#include <sys/types.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include <errno.h>
+#include <string.h>
+#include <assert.h>
+
+#include <iostream>
+#include <memory>
+#include <boost/algorithm/string/predicate.hpp>
+#include <regex>
+
+#include "common/Formatter.h"
+#include "common/Preforker.h"
+#include "common/TextTable.h"
+#include "common/ceph_argparse.h"
+#include "common/config_proxy.h"
+#include "common/debug.h"
+#include "common/errno.h"
+#include "global/global_init.h"
+#include "global/signal_handler.h"
+
+#include "include/rados/librados.hpp"
+#include "include/rbd/librbd.hpp"
+#include "include/stringify.h"
+
+#include "Driver.h"
+#include "Server.h"
+#include "Watcher.h"
+
+#define dout_context g_ceph_context
+#define dout_subsys ceph_subsys_rbd
+#undef dout_prefix
+#define dout_prefix *_dout << "rbd-ggate: " << __func__ << ": "
+
+static void usage() {
+  std::cout << "Usage: rbd-ggate [options] map <image-or-snap-spec>  Map an image to ggate device\n"
+            << "                           unmap <device path>       Unmap ggate device\n"
+            << "                           list                      List mapped ggate devices\n"
+            << "\n"
+            << "Map options:\n"
+            << "  --device <device path>  Specify ggate device path\n"
+            << "  --read-only             Map readonly\n"
+            << "  --exclusive             Forbid writes by other clients\n"
+            << "\n"
+            << "List options:\n"
+            << "  --format plain|json|xml Output format (default: plain)\n"
+            << "  --pretty-format         Pretty formatting (json and xml)\n"
+            << std::endl;
+  generic_server_usage();
+}
+
+static std::string devpath, poolname, nsname, imgname, snapname;
+static bool readonly = false;
+static bool exclusive = false;
+
+static std::unique_ptr<rbd::ggate::Driver> drv;
+
+static void handle_signal(int signum)
+{
+  derr << "*** Got signal " << sig_str(signum) << " ***" << dendl;
+
+  ceph_assert(signum == SIGINT || signum == SIGTERM);
+  ceph_assert(drv);
+
+  drv->shut_down();
+}
+
+static int do_map(int argc, const char *argv[])
+{
+  int r;
+
+  librados::Rados rados;
+  librbd::RBD rbd;
+  librados::IoCtx io_ctx;
+  librbd::Image image;
+
+  librbd::image_info_t info;
+  std::string desc;
+
+  Preforker forker;
+
+  auto args = argv_to_vec(argc, argv);
+  auto cct = global_init(NULL, args, CEPH_ENTITY_TYPE_CLIENT,
+                         CODE_ENVIRONMENT_DAEMON,
+                         CINIT_FLAG_UNPRIVILEGED_DAEMON_DEFAULTS);
+  g_ceph_context->_conf.set_val_or_die("pid_file", "");
+
+  if (global_init_prefork(g_ceph_context) >= 0) {
+    std::string err;
+    r = forker.prefork(err);
+    if (r < 0) {
+      std::cerr << err << std::endl;
+      return r;
+    }
+    if (forker.is_parent()) {
+      if (forker.parent_wait(err) != 0) {
+        return -ENXIO;
+      }
+      return 0;
+    }
+    global_init_postfork_start(g_ceph_context);
+  }
+
+  common_init_finish(g_ceph_context);
+  global_init_chdir(g_ceph_context);
+
+  if (poolname.empty()) {
+    poolname = g_ceph_context->_conf.get_val<std::string>("rbd_default_pool");
+  }
+
+  std::string devname = boost::starts_with(devpath, "/dev/") ?
+    devpath.substr(5) : devpath;
+  std::unique_ptr<rbd::ggate::Watcher> watcher;
+  uint64_t handle;
+
+  r = rados.init_with_context(g_ceph_context);
+  if (r < 0) {
+    goto done;
+  }
+
+  r = rados.connect();
+  if (r < 0) {
+    std::cerr << "rbd-ggate: failed to connect to cluster: " << cpp_strerror(r)
+              << std::endl;
+    goto done;
+  }
+
+  r = rados.ioctx_create(poolname.c_str(), io_ctx);
+  if (r < 0) {
+    std::cerr << "rbd-ggate: failed to acces pool " << poolname << ": "
+              << cpp_strerror(r) << std::endl;
+    goto done;
+  }
+
+  io_ctx.set_namespace(nsname);
+
+  r = rbd.open(io_ctx, image, imgname.c_str());
+  if (r < 0) {
+    std::cerr << "rbd-ggate: failed to open image " << imgname << ": "
+              << cpp_strerror(r) << std::endl;
+    goto done;
+  }
+
+  if (exclusive) {
+    r = image.lock_acquire(RBD_LOCK_MODE_EXCLUSIVE);
+    if (r < 0) {
+      std::cerr << "rbd-ggate: failed to acquire exclusive lock: "
+                << cpp_strerror(r) << std::endl;
+      goto done;
+    }
+  }
+
+  desc = "RBD " + poolname + "/" + (nsname.empty() ? "" : nsname + "/") +
+    imgname;
+
+  if (!snapname.empty()) {
+    r = image.snap_set(snapname.c_str());
+    if (r < 0) {
+      std::cerr << "rbd-ggate: failed to set snapshot " << snapname << ": "
+                << cpp_strerror(r) << std::endl;
+      goto done;
+    }
+    readonly = true;
+    desc += "@" + snapname;
+  }
+
+  r = image.stat(info, sizeof(info));
+  if (r < 0) {
+    std::cerr << "rbd-ggate: image stat failed: " << cpp_strerror(r)
+              << std::endl;
+    goto done;
+  }
+
+  rbd::ggate::Driver::load();
+  drv.reset(new rbd::ggate::Driver(devname, 512, info.size, readonly, desc));
+  r = drv->init();
+  if (r < 0) {
+    r = -errno;
+    std::cerr << "rbd-ggate: failed to create ggate device: " << cpp_strerror(r)
+              << std::endl;
+    goto done;
+  }
+
+  watcher.reset(new rbd::ggate::Watcher(drv.get(), io_ctx, image, info.size));
+  r = image.update_watch(watcher.get(), &handle);
+  if (r < 0) {
+    std::cerr << "rbd-ggate: failed to set watcher: " << cpp_strerror(r)
+              << std::endl;
+    drv->shut_down();
+    goto done;
+  }
+
+  std::cout << "/dev/" << drv->get_devname() << std::endl;
+
+  if (g_conf()->daemonize) {
+    global_init_postfork_finish(g_ceph_context);
+    forker.daemonize();
+  }
+
+  init_async_signal_handler();
+  register_async_signal_handler(SIGHUP, sighup_handler);
+  register_async_signal_handler_oneshot(SIGINT, handle_signal);
+  register_async_signal_handler_oneshot(SIGTERM, handle_signal);
+
+  rbd::ggate::Server(drv.get(), image).run();
+
+  unregister_async_signal_handler(SIGHUP, sighup_handler);
+  unregister_async_signal_handler(SIGINT, handle_signal);
+  unregister_async_signal_handler(SIGTERM, handle_signal);
+  shutdown_async_signal_handler();
+
+  r = image.update_unwatch(handle);
+  ceph_assert(r == 0);
+
+done:
+  image.close();
+  io_ctx.close();
+  rados.shutdown();
+
+  if (r < 0) {
+    std::cerr << "rbd-ggate: failed to map: " << cpp_strerror(r) << std::endl;
+  }
+
+  forker.exit(r < 0 ? EXIT_FAILURE : 0);
+  // Unreachable;
+  return r;
+}
+
+static int do_unmap()
+{
+  std::string devname = boost::starts_with(devpath, "/dev/") ?
+    devpath.substr(5) : devpath;
+
+  int r = rbd::ggate::Driver::kill(devname);
+  if (r < 0) {
+    cerr << "rbd-ggate: failed to destroy " << devname << ": "
+         << cpp_strerror(r) << std::endl;
+    return r;
+  }
+
+  return 0;
+}
+
+static int parse_imgpath(const std::string &imgpath, std::string *poolname,
+                         std::string *nsname, std::string *imgname,
+                         std::string *snapname) {
+  std::regex pattern("^(?:([^/]+)/(?:([^/@]+)/)?)?([^@]+)(?:@([^/@]+))?$");
+  std::smatch match;
+  if (!std::regex_match(imgpath, match, pattern)) {
+    std::cerr << "rbd-ggate: invalid spec '" << imgpath << "'" << std::endl;
+    return -EINVAL;
+  }
+
+  if (match[1].matched) {
+    *poolname = match[1];
+  }
+
+  if (match[2].matched) {
+    *nsname = match[2];
+  }
+
+  *imgname = match[3];
+
+  if (match[4].matched) {
+    *snapname = match[4];
+  }
+
+  return 0;
+}
+
+static bool find_mapped_dev_by_spec(const std::string &spec,
+                                    std::string *devname) {
+  std::string poolname, nsname, imgname, snapname;
+  int r = parse_imgpath(spec, &poolname, &nsname, &imgname, &snapname);
+  if (r < 0) {
+    return false;
+  }
+  if (poolname.empty()) {
+    // We could use rbd_default_pool config to set pool name but then
+    // we would need to initialize the global context. So right now it
+    // is mandatory for the user to specify a pool. Fortunately the
+    // preferred way for users to call rbd-ggate is via rbd, which
+    // cares to set the pool name.
+    return false;
+  }
+
+  std::map<std::string, rbd::ggate::Driver::DevInfo> devs;
+  r = rbd::ggate::Driver::list(&devs);
+  if (r < 0) {
+    return false;
+  }
+
+  for (auto &it : devs) {
+    auto &name = it.second.first;
+    auto &info = it.second.second;
+    if (!boost::starts_with(info, "RBD ")) {
+      continue;
+    }
+
+    std::string p, n, i, s;
+    parse_imgpath(info.substr(4), &p, &n, &i, &s);
+    if (p == poolname && n == nsname && i == imgname && s == snapname) {
+      *devname = name;
+      return true;
+    }
+  }
+
+  return false;
+}
+
+static int do_list(const std::string &format, bool pretty_format)
+{
+  rbd::ggate::Driver::load();
+
+  std::map<std::string, rbd::ggate::Driver::DevInfo> devs;
+  int r = rbd::ggate::Driver::list(&devs);
+  if (r < 0) {
+    return -r;
+  }
+
+  std::unique_ptr<ceph::Formatter> f;
+  TextTable tbl;
+
+  if (format == "json") {
+    f.reset(new JSONFormatter(pretty_format));
+  } else if (format == "xml") {
+    f.reset(new XMLFormatter(pretty_format));
+  } else if (!format.empty() && format != "plain") {
+    std::cerr << "rbd-ggate: invalid output format: " << format << std::endl;
+    return -EINVAL;
+  }
+
+  if (f) {
+    f->open_array_section("devices");
+  } else {
+    tbl.define_column("id", TextTable::LEFT, TextTable::LEFT);
+    tbl.define_column("pool", TextTable::LEFT, TextTable::LEFT);
+    tbl.define_column("namespace", TextTable::LEFT, TextTable::LEFT);
+    tbl.define_column("image", TextTable::LEFT, TextTable::LEFT);
+    tbl.define_column("snap", TextTable::LEFT, TextTable::LEFT);
+    tbl.define_column("device", TextTable::LEFT, TextTable::LEFT);
+  }
+
+  int count = 0;
+
+  for (auto &it : devs) {
+    auto &id = it.first;
+    auto &name = it.second.first;
+    auto &info = it.second.second;
+    if (!boost::starts_with(info, "RBD ")) {
+      continue;
+    }
+
+    std::string poolname;
+    std::string nsname;
+    std::string imgname;
+    std::string snapname(f ? "" : "-");
+    parse_imgpath(info.substr(4), &poolname, &nsname, &imgname, &snapname);
+
+    if (f) {
+      f->open_object_section("device");
+      f->dump_string("id", id);
+      f->dump_string("pool", poolname);
+      f->dump_string("namespace", nsname);
+      f->dump_string("image", imgname);
+      f->dump_string("snap", snapname);
+      f->dump_string("device", "/dev/" + name);
+      f->close_section();
+    } else {
+      tbl << id << poolname << nsname << imgname << snapname << "/dev/" + name
+          << TextTable::endrow;
+    }
+    count++;
+  }
+
+  if (f) {
+    f->close_section(); // devices
+    f->flush(std::cout);
+  } else if (count > 0) {
+    std::cout << tbl;
+  }
+
+  return 0;
+}
+
+int main(int argc, const char *argv[]) {
+  int r;
+  enum {
+    None,
+    Connect,
+    Disconnect,
+    List
+  } cmd = None;
+
+  auto args = argv_to_vec(argc, argv);
+  if (args.empty()) {
+    cerr << argv[0] << ": -h or --help for usage" << std::endl;
+    exit(1);
+  }
+  if (ceph_argparse_need_usage(args)) {
+    usage();
+    exit(0);
+  }
+  // filter out ceph config options
+  ConfigProxy{false}.parse_argv(args);
+
+  std::string format;
+  bool pretty_format = false;
+
+  for (auto i = args.begin(); i != args.end(); ) {
+    if (ceph_argparse_flag(args, i, "-h", "--help", (char*)NULL)) {
+      usage();
+      return 0;
+    } else if (ceph_argparse_witharg(args, i, &devpath, "--device",
+                                     (char *)NULL)) {
+    } else if (ceph_argparse_flag(args, i, "--read-only", (char *)NULL)) {
+      readonly = true;
+    } else if (ceph_argparse_flag(args, i, "--exclusive", (char *)NULL)) {
+      exclusive = true;
+    } else if (ceph_argparse_witharg(args, i, &format, "--format",
+                                     (char *)NULL)) {
+    } else if (ceph_argparse_flag(args, i, "--pretty-format", (char *)NULL)) {
+      pretty_format = true;
+    } else {
+      ++i;
+    }
+  }
+
+  if (args.begin() != args.end()) {
+    if (strcmp(*args.begin(), "map") == 0) {
+      cmd = Connect;
+    } else if (strcmp(*args.begin(), "unmap") == 0) {
+      cmd = Disconnect;
+    } else if (strcmp(*args.begin(), "list") == 0) {
+      cmd = List;
+    } else {
+      cerr << "rbd-ggate: unknown command: " << *args.begin() << std::endl;
+      return EXIT_FAILURE;
+    }
+    args.erase(args.begin());
+  }
+
+  if (cmd == None) {
+    cerr << "rbd-ggate: must specify command" << std::endl;
+    return EXIT_FAILURE;
+  }
+
+  switch (cmd) {
+    case Connect:
+      if (args.begin() == args.end()) {
+        cerr << "rbd-ggate: must specify image-or-snap-spec" << std::endl;
+        return EXIT_FAILURE;
+      }
+      if (parse_imgpath(*args.begin(), &poolname, &nsname, &imgname,
+                        &snapname) < 0) {
+        return EXIT_FAILURE;
+      }
+      args.erase(args.begin());
+      break;
+    case Disconnect:
+      if (args.begin() == args.end()) {
+        std::cerr << "rbd-ggate: must specify ggate device or image-or-snap-spec"
+                  << std::endl;
+        return EXIT_FAILURE;
+      }
+      if (boost::starts_with(*args.begin(), "/dev/") ||
+          !find_mapped_dev_by_spec(*args.begin(), &devpath)) {
+        devpath = *args.begin();
+      }
+      args.erase(args.begin());
+      break;
+    default:
+      break;
+  }
+
+  if (args.begin() != args.end()) {
+    cerr << "rbd-ggate: unknown args: " << *args.begin() << std::endl;
+    return EXIT_FAILURE;
+  }
+
+  switch (cmd) {
+    case Connect:
+      if (imgname.empty()) {
+        cerr << "rbd-ggate: image name was not specified" << std::endl;
+        return EXIT_FAILURE;
+      }
+
+      r = do_map(argc, argv);
+      if (r < 0)
+        return EXIT_FAILURE;
+      break;
+    case Disconnect:
+      r = do_unmap();
+      if (r < 0)
+        return EXIT_FAILURE;
+      break;
+    case List:
+      r = do_list(format, pretty_format);
+      if (r < 0)
+        return EXIT_FAILURE;
+      break;
+    default:
+      usage();
+      return EXIT_FAILURE;
+  }
+
+  return 0;
+}