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Reasons for volume teardown not completing

Alnoor_AllidinaAlnoor_Allidina Member Posts: 11

Hi,

I'm helping out with an issue where a product caches data for each volume on the system. When a volume is torn down, the product cleans up its cached data. In some cases, when running alongside a particular backup application (they believe), volumes are occasionally not completely torn down and the product cache grows unwieldly.

I'm trying to understand why a particular volume has not fully dismounted.

What might I be missing or not understanding? Thanks in advance for any pointers.

Here's what I have deduced, given a manual dump that has my minifilter running in it.

  1. I see that my minifilter has seen the InstanceTeardownStartCallback but I see no evidence that it has seen InstanceTeardownComplete.
  2. I've searched the dump for any mention of the DiskDeviceObject in a an allocation with the 'File' pooltag, thinking there may be an open FILE_OBJECT. I found none.
  3. If I look at the DiskDeviceObject, I see that it's in remove pending state and the VPB has been mostly cleaned out:

    ##             0: kd> !devobj ffffe0015c24fca0
    ##         Device object (ffffe0015c24fca0) is for:
    ##          HarddiskVolume5 \Driver\volmgr DriverObject ffffe001537e13e0
    ##         Current Irp 00000000 RefCount 8 Type 00000007 Flags 00003050
    ##         Vpb ffffe0015a394120 SecurityDescriptor ffffc00077cae200 DevExt ffffe0015c24fdf0 DevObjExt ffffe0015c24ffa0 Dope ffffe0015aecbd90 DevNode ffffe00154c36d30 
    ##         ExtensionFlags (0x00000004)  DOE_REMOVE_PENDING
    ##         Characteristics (0x00060000)  FILE_DEVICE_ALLOW_APPCONTAINER_TRAVERSAL, FILE_PORTABLE_DEVICE
    ##         AttachedDevice (Upper) ffffe0015ca24310 \Driver\volsnap
    ##         Device queue is not busy.
    ##     
    ##     0: kd> dt _VPB ffffe0015a394120 
    ##     ntdll!_VPB
    ##        +0x000 Type             : 0n10
    ##        +0x002 Size             : 0n96
    ##        +0x004 Flags            : 0x28
    ##        +0x006 VolumeLabelLength : 0
    ##        +0x008 DeviceObject     : (null) 
    ##        +0x010 RealDevice       : 0xffffe001`5c24fca0 _DEVICE_OBJECT
    ##        +0x018 SerialNumber     : 0xffffffff
    ##        +0x01c ReferenceCount   : 0
    ##        +0x020 VolumeLabel      : [32]  ""
    
  4. Here's what !fltkd says about the volume (there are a few open STREAM_LIST_CTRLs but no open contexts within them...) I'm attaching the verbose output as a file.

FLT_VOLUME: ffffe001587de7f0 "\Device\HarddiskVolume5"
FLT_OBJECT: ffffe001587de7f0 [04000000] Volume
RundownRef : 0x0000000000000006 (3)
PointerCount : 0x00000002
PrimaryLink : [ffffe00153dd0650-ffffe001542901a0]
Frame : ffffe00153dd0520 "Frame 0"
Flags : [00000164] SetupNotifyCalled EnableNameCaching FilterAttached +100!!
FileSystemType : [00000002] FLT_FSTYPE_NTFS
VolumeLink : [ffffe00153dd0650-ffffe001542901a0]
DeviceObject : ffffe0015679d3e0
DiskDeviceObject : ffffe0015c24fca0
FrameZeroVolume : ffffe001587de7f0
VolumeInNextFrame : 0000000000000000
Guid : "\??\Volume{75f14783-51e1-11ea-80f0-005056a67746}"
CDODeviceName : "\Ntfs"
CDODriverName : "\FileSystem\Ntfs"
TargetedOpenCount : 0
Callbacks : (ffffe001587de900)
ContextLock : (ffffe001587dece8)
VolumeContexts : (ffffe001587decf0) Count=1
StreamListCtrls : (ffffe001587decf8) rCount=9
FileListCtrls : (ffffe001587ded78) rCount=0
NameCacheCtrl : (ffffe001587dedf8)
InstanceList : (ffffe001587de880)
FLT_INSTANCE: ffffe0015bdbf010 "MpFilter Instance" "328000"
FLT_INSTANCE: ffffe0015c421010 "mfehidk" "321300.00"

Thanks,
Alnoor

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