Allow to pass remount option to Mount method of cros_disks_client.

chromeos/dbus/cros_disks_client.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROMEOS_DBUS_CROS_DISKS_CLIENT_H_
 #define CHROMEOS_DBUS_CROS_DISKS_CLIENT_H_
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 90 matching lines @@
   UNMOUNT_OPTIONS_NONE,
   UNMOUNT_OPTIONS_LAZY,  // Do lazy unmount.
 };
 
 // Mount option to control write permission to a device.
 enum MountAccessMode {
   MOUNT_ACCESS_MODE_READ_WRITE,
   MOUNT_ACCESS_MODE_READ_ONLY,
 };
 
+// Whether to mount to a new path or remount an existing one.

[hashimoto, 2016/10/19 08:46:23]

What does "remount an existing one" mean?
Please clarify what happens with each option.

IIUC when an already mounted disk is mounted again, mount fails with
REMOUNT_OPTION_DISABLED unless unmount is done before, while it succeeds with
REMOUNT_OPTION_ENABLED.
Am I understanding it right?
Also, what happens if REMOUNT_OPTION_ENABLED is used against a disk which hasn't
mounted yet?

BTW, why doesn't CrosDisks automatically adds "remount" to the options when
mounting an already mounted disk?

[yamaguchi1, 2016/10/19 10:34:10]

Revised the comments.
I made it this way to minimize the change preserving existing behavior which
have been returning errors for duplicated mount attempts.
Now I think we may change it (by another patch), if there is no special need to
fail mounting same device twice from Chrome.

+enum RemountOption {
+  REMOUNT_OPTION_DISABLED,
+  REMOUNT_OPTION_ENABLED,
+};
+
 // A class to represent information about a disk sent from cros-disks.
 class CHROMEOS_EXPORT DiskInfo {
  public:
   DiskInfo(const std::string& device_path, dbus::Response* response);
   ~DiskInfo();
 
   // Device path. (e.g. /sys/devices/pci0000:00/.../8:0:0:0/block/sdb/sdb1)
   const std::string& device_path() const { return device_path_; }
 
   // Disk mount path. (e.g. /media/removable/VOLUME)
@@ skipping 150 matching lines @@
   // - The |source_format| argument passes the file extension (with the leading
   //   dot, for example ".zip"). If |source_format| is empty then the source
   //   format is auto-detected.
   // - The |mount_label| argument passes an optional mount label to be used as
   //   the directory name of the mount point. If |mount_label| is empty, the
   //   mount label will be based on the |source_path|.
   virtual void Mount(const std::string& source_path,
                      const std::string& source_format,
                      const std::string& mount_label,
                      MountAccessMode access_mode,
+                     RemountOption remount,
                      const base::Closure& callback,
                      const base::Closure& error_callback) = 0;
 
   // Calls Unmount method.  |callback| is called after the method call succeeds,
   // otherwise, |error_callback| is called.
   virtual void Unmount(const std::string& device_path,
                        UnmountOptions options,
                        const base::Closure& callback,
                        const base::Closure& error_callback) = 0;
 
@@ skipping 43 matching lines @@
 
   // Returns the path of the mount point for archive files.
   static base::FilePath GetArchiveMountPoint();
 
   // Returns the path of the mount point for removable disks.
   static base::FilePath GetRemovableDiskMountPoint();
 
   // Composes a list of mount options.
   static std::vector<std::string> ComposeMountOptions(
       const std::string& mount_label,
-      MountAccessMode access_mode);
+      MountAccessMode access_mode,
+      RemountOption remount);
 
  protected:
   // Create() should be used instead.
   CrosDisksClient();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(CrosDisksClient);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_DBUS_CROS_DISKS_CLIENT_H_