fast io in filters

NTFSD
1

For File system filter from what i know only following 3 fast io
calls are compulsory (because no return value for them):
AcquireFileForNtCreateSection
ReleaseFileForNtCreateSection
FastIoDetachDevice

3 questions
1> for other fast ios, can a filter return FALSE.
i.e. will returning FALSE have any side effects/performance issue.
2> somewhere in the archives i read that it doesn’t make much
sense to use the fast I/O device control path. so is it
a strong recommendation (or we may say it a rule)
“don’t implement fast I/O device control path”?
3> can we say the above point for other fast ios
(except last 3) i.e. “don’t implement fast I/O path.
just return FALSE”.

2

Hi,

for other fast ios, can a filter return FALSE.
i.e. will returning FALSE have any side effects/performance issue.
If filter or FSD return FALSE then IRP created and send to file system
driver stack. This decrease performance.

somewhere in the archives i read that it doesn’t make much
sense to use the fast I/O device control path. so is it
a strong recommendation (or we may say it a rule)
“don’t implement fast I/O device control path”?

It is strong recommended for filter drivers to implement fast I/O.

can we say the above point for other fast ios
(except last 3) i.e. “don’t implement fast I/O path.
just return FALSE”.

Filter drivers in fast I/O dispatch procedures must call next lower driver
fast I/O procedure and return value returned by this procedure.

Best regards,
Victor Fisyuk
EMail/MSN: xxxxx@rambler.ru
Web: http://rockdbg.siteburg.com

3

Mani

It is very important that you (a) have a look at the filespy example in the
ifs kit regards how to implement fastio (b) read the OSR paper about fastio
which comes with the ifs kit.

Regards
Lyndon

“Mani” wrote in message news:xxxxx@ntfsd…
>
> For File system filter from what i know only following 3 fast io
> calls are compulsory (because no return value for them):
> AcquireFileForNtCreateSection
> ReleaseFileForNtCreateSection
> FastIoDetachDevice
>
> 3 questions
> 1> for other fast ios, can a filter return FALSE.
> i.e. will returning FALSE have any side effects/performance issue.
> 2> somewhere in the archives i read that it doesn’t make much
> sense to use the fast I/O device control path. so is it
> a strong recommendation (or we may say it a rule)
> “don’t implement fast I/O device control path”?
> 3> can we say the above point for other fast ios
> (except last 3) i.e. “don’t implement fast I/O path.
> just return FALSE”.
>
>
>