gecko/dom/system/gonk/Volume.cpp

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "Volume.h"
#include "VolumeCommand.h"
#include "VolumeManager.h"
#include "VolumeManagerLog.h"
#include "nsIVolume.h"
#include "nsXULAppAPI.h"

#include <vold/ResponseCode.h>

namespace mozilla {
namespace system {

Volume::EventObserverList Volume::mEventObserverList;

// We have a feature where volumes can be locked when mounted. This
// is used to prevent a volume from being shared with the PC while
// it is actively being used (say for storing an update image)
//
// We use WakeLocks (a poor choice of name, but it does what we want)
// from the PowerManagerService to determine when we're locked.
// In particular we'll create a wakelock called volume-NAME-GENERATION
// (where NAME is the volume name, and GENERATION is its generation
// number), and if this wakelock is locked, then we'll prevent a volume
// from being shared.
//
// Implementation Details:
//
// Since the AutoMounter can only control when something gets mounted
// and not when it gets unmounted (for example: a user pulls the SDCard)
// and because Volume and nsVolume data structures are maintained on
// separate threads, we have the potential for some race conditions.
// We eliminate the race conditions by introducing the concept of a
// generation number. Every time a volume transitions to the Mounted
// state, it gets assigned a new generation number. Whenever the state
// of a Volume changes, we send the updated state and current generation
// number to the main thread where it gets updated in the nsVolume.
//
// Since WakeLocks can only be queried from the main-thread, the
// nsVolumeService looks for WakeLock status changes, and forwards
// the results to the IOThread.
//
// If the Volume (IOThread) recieves a volume update where the generation
// number mismatches, then the update is simply ignored.
//
// When a Volume (IOThread) initially becomes mounted, we assume it to
// be locked until we get our first update from nsVolume (MainThread).
static int32_t sMountGeneration = 0;

// We don't get media inserted/removed events at startup. So we
// assume it's present, and we'll be told that it's missing.
Volume::Volume(const nsCSubstring &aName)
  : mMediaPresent(true),
    mState(nsIVolume::STATE_INIT),
    mName(aName),
    mMountGeneration(-1),
    mMountLocked(true)  // Needs to agree with nsVolume::nsVolume
{
  DBG("Volume %s: created", NameStr());
}

void
Volume::SetMediaPresent(bool aMediaPresent)
{
  // mMediaPresent is slightly redunant to the state, however
  // when media is removed (while Idle), we get the following:
  //    631 Volume sdcard /mnt/sdcard disk removed (179:0)
  //    605 Volume sdcard /mnt/sdcard state changed from 1 (Idle-Unmounted) to 0 (No-Media)
  //
  // And on media insertion, we get:
  //    630 Volume sdcard /mnt/sdcard disk inserted (179:0)
  //    605 Volume sdcard /mnt/sdcard state changed from 0 (No-Media) to 2 (Pending)
  //    605 Volume sdcard /mnt/sdcard state changed from 2 (Pending) to 1 (Idle-Unmounted)
  //
  // On media removal while the media is mounted:
  //    632 Volume sdcard /mnt/sdcard bad removal (179:1)
  //    605 Volume sdcard /mnt/sdcard state changed from 4 (Mounted) to 5 (Unmounting)
  //    605 Volume sdcard /mnt/sdcard state changed from 5 (Unmounting) to 1 (Idle-Unmounted)
  //    631 Volume sdcard /mnt/sdcard disk removed (179:0)
  //    605 Volume sdcard /mnt/sdcard state changed from 1 (Idle-Unmounted) to 0 (No-Media)
  //
  // When sharing with a PC, it goes Mounted -> Idle -> Shared
  // When unsharing with a PC, it goes Shared -> Idle -> Mounted
  //
  // The AutoMounter needs to know whether the media is present or not when
  // processing the Idle state.

  if (mMediaPresent == aMediaPresent) {
    return;
  }

  LOG("Volume: %s media %s", NameStr(), aMediaPresent ? "inserted" : "removed");
  mMediaPresent = aMediaPresent;
  mEventObserverList.Broadcast(this);
}

void
Volume::SetState(Volume::STATE aNewState)
{
  if (aNewState == mState) {
    return;
  }
  if (aNewState == nsIVolume::STATE_MOUNTED) {
    mMountGeneration = ++sMountGeneration;
    LOG("Volume %s: changing state from %s to %s @ '%s' (%d observers) "
        "mountGeneration = %d, locked = %d",
        NameStr(), StateStr(mState),
        StateStr(aNewState), mMountPoint.get(), mEventObserverList.Length(),
        mMountGeneration, (int)mMountLocked);
  } else {
    LOG("Volume %s: changing state from %s to %s (%d observers)",
        NameStr(), StateStr(mState),
        StateStr(aNewState), mEventObserverList.Length());
  }

  if (aNewState == nsIVolume::STATE_NOMEDIA) {
    // Cover the startup case where we don't get insertion/removal events
    mMediaPresent = false;
  }
  mState = aNewState;
  mEventObserverList.Broadcast(this);
}

void
Volume::SetMountPoint(const nsCSubstring &aMountPoint)
{
  if (mMountPoint.Equals(aMountPoint)) {
    return;
  }
  mMountPoint = aMountPoint;
  DBG("Volume %s: Setting mountpoint to '%s'", NameStr(), mMountPoint.get());
}

void
Volume::StartMount(VolumeResponseCallback *aCallback)
{
  StartCommand(new VolumeActionCommand(this, "mount", "", aCallback));
}

void
Volume::StartUnmount(VolumeResponseCallback *aCallback)
{
  StartCommand(new VolumeActionCommand(this, "unmount", "force", aCallback));
}

void
Volume::StartShare(VolumeResponseCallback *aCallback)
{
  StartCommand(new VolumeActionCommand(this, "share", "ums", aCallback));
}

void
Volume::StartUnshare(VolumeResponseCallback *aCallback)
{
  StartCommand(new VolumeActionCommand(this, "unshare", "ums", aCallback));
}

void
Volume::StartCommand(VolumeCommand *aCommand)
{
  VolumeManager::PostCommand(aCommand);
}

//static
void
Volume::RegisterObserver(Volume::EventObserver *aObserver)
{
  MOZ_ASSERT(MessageLoop::current() == XRE_GetIOMessageLoop());

  mEventObserverList.AddObserver(aObserver);
  // Send an initial event to the observer (for each volume)
  size_t numVolumes = VolumeManager::NumVolumes();
  for (size_t volIndex = 0; volIndex < numVolumes; volIndex++) {
    RefPtr<Volume> vol = VolumeManager::GetVolume(volIndex);
    aObserver->Notify(vol);
  }
}

//static
void
Volume::UnregisterObserver(Volume::EventObserver *aObserver)
{
  MOZ_ASSERT(MessageLoop::current() == XRE_GetIOMessageLoop());

  mEventObserverList.RemoveObserver(aObserver);
}

//static
void
Volume::UpdateMountLock(const nsACString &aVolumeName,
                        const int32_t &aMountGeneration,
                        const bool &aMountLocked)
{
  RefPtr<Volume> vol = VolumeManager::FindVolumeByName(aVolumeName);
  if (!vol || (vol->mMountGeneration != aMountGeneration)) {
    return;
  }
  if (vol->mMountLocked != aMountLocked) {
    vol->mMountLocked = aMountLocked;
    DBG("Volume::UpdateMountLock for '%s' to %d\n", vol->NameStr(), (int)aMountLocked);
    mEventObserverList.Broadcast(vol);
  }
}

void
Volume::HandleVoldResponse(int aResponseCode, nsCWhitespaceTokenizer &aTokenizer)
{
  // The volume name will have already been parsed, and the tokenizer will point
  // to the token after the volume name
  switch (aResponseCode) {
    case ResponseCode::VolumeListResult: {
      // Each line will look something like:
      //
      //  sdcard /mnt/sdcard 1
      //
      nsDependentCSubstring mntPoint(aTokenizer.nextToken());
      SetMountPoint(mntPoint);
      nsresult errCode;
      nsCString state(aTokenizer.nextToken());
      SetState((STATE)state.ToInteger(&errCode));
      break;
    }

    case ResponseCode::VolumeStateChange: {
      // Format of the line looks something like:
      //
      //  Volume sdcard /mnt/sdcard state changed from 7 (Shared-Unmounted) to 1 (Idle-Unmounted)
      //
      // So we parse out the state after the string " to "
      while (aTokenizer.hasMoreTokens()) {
        nsAutoCString token(aTokenizer.nextToken());
        if (token.Equals("to")) {
          nsresult errCode;
          token = aTokenizer.nextToken();
          SetState((STATE)token.ToInteger(&errCode));
          break;
        }
      }
      break;
    }

    case ResponseCode::VolumeDiskInserted:
      SetMediaPresent(true);
      break;

    case ResponseCode::VolumeDiskRemoved: // fall-thru
    case ResponseCode::VolumeBadRemoval:
      SetMediaPresent(false);
      break;

    default:
      LOG("Volume: %s unrecognized reponse code (ignored)", NameStr());
      break;
  }
}

} // namespace system
} // namespace mozilla