[0.4.9] cherry-pick [FASTFAT] When extending a file, also lock the DirResource.

This avoids race conditions under high IOs and thus corruption on
the FS, or assertions failures in the kernel.
Easily triggered by building ReactOS on ReactOS ;-).

(cherry picked from commit 30b836b)

Author: HeisSpiter

drivers/filesystems/fastfat/rw.c

@@ -1064,9 +1064,18 @@ VfatWrite(
         ByteOffset.u.LowPart + Length > Fcb->RFCB.FileSize.u.LowPart)
     {
         LARGE_INTEGER AllocationSize;
+
+        if (!ExAcquireResourceExclusiveLite(&IrpContext->DeviceExt->DirResource, CanWait))
+        {
+            goto ByeBye;
+        }
+
         AllocationSize.QuadPart = ByteOffset.u.LowPart + Length;
         Status = VfatSetAllocationSizeInformation(IrpContext->FileObject, Fcb,
                                                   IrpContext->DeviceExt, &AllocationSize);
+
+        ExReleaseResourceLite(&IrpContext->DeviceExt->DirResource);
+
         if (!NT_SUCCESS (Status))
         {
             goto ByeBye;