IRQL Questions

NTFSD
1

Hi,

is DPC_Level and Dispatch_Level the same? If not, which is higher?

Also, since the (IFS-Kit) Minifilter sources say that the Post Operations
are called at DPC_Level, I assume I can’t use most FltManager functions (for
example, I am currently using FltIsDirectory in the post ops, and it says it
should be called at <= APC_Level - so even though for my limited testing it
has been working I assume it’s not generally safe?)

I am having the same trouble for getting the filenames. Especially for
IRP_NOCACHE flag, I can never get the file name in pre operations, but can’t
use FltGetFileNameInformation in the Post Operation. Is the best way to deal
with that to store the filename from the Precreate and then use it later
when I get the IRP_NOCACHE?

Thanks a lot, bjorn

2

DPC_LEVEL == DISPATCH_LEVEL == IRQL 2

Just as in a legacy filter, you need to control your IRQL by synchronizing
and/or posting completion routines. Filter Manager has facilities that
make it easier to do this.

You don’t want to retrieve file names in the I/O path. The best place to
get the name is in post-create. Squirrel it away in your stream context.

  • Dan.

At 11:11 AM 11/11/2005 -0800, Bjorn wrote:

Hi,

is DPC_Level and Dispatch_Level the same? If not, which is higher?

Also, since the (IFS-Kit) Minifilter sources say that the Post Operations
are called at DPC_Level, I assume I can’t use most FltManager functions (for
example, I am currently using FltIsDirectory in the post ops, and it says it
should be called at <= APC_Level - so even though for my limited testing it
has been working I assume it’s not generally safe?)

I am having the same trouble for getting the filenames. Especially for
IRP_NOCACHE flag, I can never get the file name in pre operations, but can’t
use FltGetFileNameInformation in the Post Operation. Is the best way to deal
with that to store the filename from the Precreate and then use it later
when I get the IRP_NOCACHE?

Thanks a lot, bjorn

Questions? First check the IFS FAQ at
https://www.osronline.com/article.cfm?id=17

You are currently subscribed to ntfsd as: xxxxx@privtek.com
To unsubscribe send a blank email to xxxxx@lists.osr.com

3

Thanks Dan. Your answer and the previous “Minifilter questions”, which I
just now saw, helped a lot.

bjorn

“Dan Kyler” wrote in message news:xxxxx@ntfsd…
> DPC_LEVEL == DISPATCH_LEVEL == IRQL 2
>
> Just as in a legacy filter, you need to control your IRQL by synchronizing
> and/or posting completion routines. Filter Manager has facilities that
> make it easier to do this.
>
> You don’t want to retrieve file names in the I/O path. The best place to
> get the name is in post-create. Squirrel it away in your stream context.
>
> - Dan.
>
> At 11:11 AM 11/11/2005 -0800, Bjorn wrote:
>>Hi,
>>
>>is DPC_Level and Dispatch_Level the same? If not, which is higher?
>>
>>Also, since the (IFS-Kit) Minifilter sources say that the Post Operations
>>are called at DPC_Level, I assume I can’t use most FltManager functions
>>(for
>>example, I am currently using FltIsDirectory in the post ops, and it says
>>it
>>should be called at <= APC_Level - so even though for my limited testing
>>it
>>has been working I assume it’s not generally safe?)
>>
>>I am having the same trouble for getting the filenames. Especially for
>>IRP_NOCACHE flag, I can never get the file name in pre operations, but
>>can’t
>>use FltGetFileNameInformation in the Post Operation. Is the best way to
>>deal
>>with that to store the filename from the Precreate and then use it later
>>when I get the IRP_NOCACHE?
>>
>>Thanks a lot, bjorn
>>
>>
>>
>>—
>>Questions? First check the IFS FAQ at
>>https://www.osronline.com/article.cfm?id=17
>>
>>You are currently subscribed to ntfsd as: xxxxx@privtek.com
>>To unsubscribe send a blank email to xxxxx@lists.osr.com
>
>
>

4

> is DPC_Level and Dispatch_Level the same?

Yes.

Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
xxxxx@storagecraft.com
http://www.storagecraft.com