Force windows to refresh a disk FAT [closed]

Question

I have a separate partition on my disk formatted with FAT32. When I hibernate windows, I want to be able to load another OS, create/modify files that are on that partition, then bring Windows out of hibernation and be able to see the changes that I've made.

I know what you're going to type, "Well, you're not supposed to do that!" and then link me to some specs about how what I'm trying to do is wrong/impossible/going to break EVERYTHING. However, I'm sure there's some way I can get around that. :)

I don't need the FAT32 partition in Windows, except to read the files that were written there, then I'm done - so whatever the solution is, it's acceptable for the disk to be completely inaccessible for a period of time. Unfortunately, I can't take the entire physical disk offline because it is just a partition of the same physical device that windows is installed on -- just the partition.

These are the things I've tried so far...

1. Google it. I got at least one "this is NEVER going to happen" answer. Unacceptable! :)
2. Unmount the disk before hibernating. Mount after coming out of hibernation. This seems to have no effect. Windows still thinks the FAT is the same as it was before, so whatever data I wrote to disk is lost, and any files I resized are corrupted. If any of the file was cached, it's even worse.
3. Use DeviceIoControl to call IOCTL_DISK_UPDATE_PROPERTIES to try and refresh the disk (but the partition table hasn't changed, so this doesn't really do anything).

Is there any way to invalidate the disk/volume read cache to force windows to go back to the disk?

I thought about opening the partition and reading/writing directly by using libfat and bypassing the cache or something is overkill.

Answer 1

So I finally got a solution to my problem. In my mind, I associated Mount Point with Mount. These are NOT the same thing. Removing all of the volume mount points does not make the volume unmounted. It's still mounted but not in the sense that you have a path you can access in explorer.

This is the article that started it all. It also goes to show that searching for your EXACT problem, as opposed to the perceived problem can help a lot!

So there were a couple of solutions, one was to constantly call NtSetSystemInformation() in a tight loop to set the "SYSTEMCACHEINFORMATION" property to essentially empty/clear the cache whenever the system is going to hibernation. Then stop the loop when you come out. This, to me, seemed like it could affect system performance. So I discarded it.

Even better though, is the recommended solution to a slightly different problem presented in this MSDN article, which provides direction to an even better solution to the problem: Dismounting Volumes in a Hibernate Once/Resume Many Configuration

Now I have a service which will flush the write caches, then lock and dismount the volume whenever the system goes into hibernation/sleep and release the lock on the volume as soon as it comes out.

Here's a little bit of code. OnHibernate>

volumeHandle = CreateFile(volumePath,
                          GENERIC_READ|GENERIC_WRITE, 
                          FILE_SHARE_READ|FILE_SHARE_WRITE,
                          NULL,
                          OPEN_EXISTING, 
                          FILE_ATTRIBUTE_NORMAL,
                          0 );
FlushFileBuffers( volumeHandle );
DeviceIoControl( volumeHandle, FSCTL_LOCK_VOLUME, NULL, 0, NULL, 0, &cbReturned, NULL ) ;
DeviceIoControl( volumeHandle, FSCTL_DISMOUNT_VOLUME, NULL, 0, NULL, 0, &cbReturned, NULL );
//Keep the handle open here.
//System hibernates.

OnResume>

DeviceIoControl( volumeHandle, FSCTL_UNLOCK_VOLUME, NULL, 0, NULL, 0, &cbReturned, NULL )
CloseHandle(volumeHandle)

Hopefully this helps someone else out in the future :)