Re-read the original reply. MmGetSystemAddressForMdlSafe is an allocation
request for system PTEs. MmAllocateMappingAddress and
MmMapLockedPagesWithReservedMapping can help here. They are XP and later
however.
=====================
Mark Roddy
-----Original Message-----
From: Jos? Vicente S?nchez Ortega [mailto:xxxxx@secuware.com]
Sent: Monday, December 01, 2003 11:56 AM
To: Windows System Software Devs Interest List
Subject: [ntdev] RE: Right value to return in a dispatch
function of a hard disk filter driver when
MmGetSystemAddressForMdlSafe failsThank you very much for your answer. I use a pre-allocated
memory pool in my driver in order to avoid memory allocation
problems in low resource situations but, as I mentioned, the
function which fails is MmGetSystemAddressForMdlSafe not an
allocation function. The problem is that if this function
fails, I don’t know how to map user buffer in order to
manipulate it as I need. I can use the set of functions which
you have mentioned but I still will have a problem in W2K
(since my driver must work in that platform too) In W2K, I
can pre-allocate a memory pool too but, how can I acomplish
the task of reserve a virtual address mapping range to ensure
that I will always able to map the MDL I receive?Best regards,
Jose Vicente.
-----Mensaje original-----
De: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] En nombre de Henry
Gabryjelski Enviado el: s?bado, 29 de noviembre de 2003 19:10
Para: Windows System Software Devs Interest List
Asunto: [ntdev] RE: Right value to return in a dispatch
function of a hard disk filter driver when
MmGetSystemAddressForMdlSafe failsUnfortunately, your filter driver is now causing data
corruption. That message means that some data which the user
thinks is properly written was not. There is very little
chance you can determine what data that is after the fact,
and the original writer of that data is likely gone, so it
cannot be recreated.This is why such a huge emphasis on forward progress
guarantee was made in the storage stack for Windows XP/WS03.
Paging requests are guaranteed never to fail due to
insufficient resource in a “stock” Windows XP installation
(no 3rd party stuff). The port drivers ensure they can
handle a single-page request without resources, the class
drivers (disk, cdrom) ensure they can handle any size request
without resources (even if they have to pend the IO), and the
memory manager retries paging requests that fail with
out-of-memory errors as single-page requests.If you can find a way to prevent disk IO from failing (by
pre-allocating in
StartDevice() enough memory to handle a single request, and
then serializing as needed when out-of-memory occurs). When
using the pre-allocated request resources, use a
pre-allocated mapping address too:MmAllocateMappingAddress() allows you to reserve a range of
virtual address space to use in out-of-memory conditions when
you absolutely must not fail IO, such as disk IO (WinXP and
later); use the related functions
MmMapLockedPagesWithReservedMapping(), MmUnmapReservedMapping(), and
MmFreeMappingAddress() to finish the job. Please use this
sparingly, as virtual address space is limited on 32 bit machines.This does require adding some more logic attached to each
request you handle in the completion routine: Was the request
using the preallocated resources?
If so, you must unmap the reserved mapping and then check if
anything else was queued to use the preallocated resources.
Of course, checking the queue and leaving the preallocated
resources for the next person requires appropriate
synchronization (just use a spinlock – you’re already in a
low-memory condition, so perf isn’t key).I encourage you to go that last mile to really make your
driver 100% reliable. Data corruption is a very bad thing
for customers, and out-of-memory conditions really do occur
in the real world. (mostly due to drivers leaking memory,
but I’ve seen at least two other causes in heavy loads).Good luck!
.-----Original Message-----
From: Nick Ryan [mailto:xxxxx@nryan.com]
Sent: Friday, November 28, 2003 12:14 PM
Subject: Re: Right value to return in a dispatch function of
a hard disk filter driver when MmGetSystemAddressForMdlSafe failsNo, you’re doing the correct thing. The lazy writer is
attempting to push out dirty data from the filesystem cache
to disk, and the paging writes are failing because of your
driver. Everything is behaving as it should under this
simulated error condition.Jos? Vicente S?nchez Ortega wrote:
> Hello,
>
> I have developed a filter driver for hard disk class and, when I
> activate Driver Verifier to test it (enabling the “inject faults”
> option) I see that, for example, the function
> MmGetSystemAddressForMdlSafe fails repeatedly when I call it in my
> READ and WRITE dispatch functions to map the the buffer. I’m
> completing the IRP in that case with STATUS_INSUFFICIENT_RESOURCES.
> Some times, the system shows a message informing me that the lazzy
> writer was unable to READ/WRITE data (and the file name) I have not
> seen any secondary effect but I would like to know if it is
possible
> to return another status code or do a different process to
avoid this
> error (in any case the error message appears only when I run Driver
> Verifier)
>
> Thanks in advance,
>
>
> Jose Vicente.
>
>
>–
Nick Ryan (MVP for DDK)
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