This seems strange. I understand that NT 5.x has a limitation of 64 MB MDLs on x86, but direct I/O was designed for exactly this case of large I/O operations. Has anyone verified that 2k3 doesn’t do MDL chaining for direct I/O when the transfer is larger than a single MDL can hold?
Also aren’t there changes to the IRP dispatch routines required to cope with not having an Irp->MdlAddress pointer anymore?
Cameron
From: tfaber@svn.reactos.org Sent: Tuesday, August 26, 2014 6:41 AM To: ros-diffs@reactos.org
Author: tfaber Date: Tue Aug 26 13:41:57 2014 New Revision: 63953
URL: http://svn.reactos.org/svn/reactos?rev=63953&view=rev Log: [FASTFAT] - Do not use direct I/O since it limits read/write operations to 64 MB CORE-8410 #resolve
Modified: trunk/reactos/drivers/filesystems/fastfat/fsctl.c
Modified: trunk/reactos/drivers/filesystems/fastfat/fsctl.c URL: http://svn.reactos.org/svn/reactos/trunk/reactos/drivers/filesystems/fastfat... ============================================================================== --- trunk/reactos/drivers/filesystems/fastfat/fsctl.c [iso-8859-1] (original) +++ trunk/reactos/drivers/filesystems/fastfat/fsctl.c [iso-8859-1] Tue Aug 26 13:41:57 2014 @@ -442,8 +442,7 @@ goto ByeBye; }
- DeviceObject->Flags = DeviceObject->Flags | DO_DIRECT_IO; - DeviceExt = (PVOID) DeviceObject->DeviceExtension; + DeviceExt = DeviceObject->DeviceExtension; RtlZeroMemory(DeviceExt, ROUND_UP(sizeof(DEVICE_EXTENSION), sizeof(ULONG)) + sizeof(HASHENTRY*) * HashTableSize); DeviceExt->FcbHashTable = (HASHENTRY**)((ULONG_PTR)DeviceExt + ROUND_UP(sizeof(DEVICE_EXTENSION), sizeof(ULONG))); DeviceExt->HashTableSize = HashTableSize;