Handle read/write operations

NTFSD
1

I’ve tried to handle read/write operations in order to perform
modifications with data being written to/read from but have
collided with the following problem:

  • trying open a file with notepad before I’ve started to handle
    r/w ops then close it and starting to handle these r/w ops -
    notepad ignores further request to this file through my routines
    displaying the same content on the file.

As I suggested it is connected with cache manager, but I’ve tried
some suggestions I had with no result.

What do I wrong? What can I check/read to research it?

-Alex

2

Have a look into the fastfat code provided with IFS kit.

Thanks,
Amit

This posting is provided “AS IS” with no warranties, and confers no
rights.

3

Could you explain a little bit more on your problem?

-htfv

----- Original Message -----
From: “Alex Vardugin”
To: “File Systems Developers”
Sent: Thursday, September 19, 2002 7:50 AM
Subject: [ntfsd] Handle read/write operations

> I’ve tried to handle read/write operations in order to perform
> modifications with data being written to/read from but have
> collided with the following problem:
> - trying open a file with notepad before I’ve started to handle
> r/w ops then close it and starting to handle these r/w ops -
> notepad ignores further request to this file through my routines
> displaying the same content on the file.
>
> As I suggested it is connected with cache manager, but I’ve tried
> some suggestions I had with no result.
>
> What do I wrong? What can I check/read to research it?
>
> -Alex
>
>
>
> —
> You are currently subscribed to ntfsd as: xxxxx@vba.com.by
> To unsubscribe send a blank email to %%email.unsub%%
>

4

Alex: What’s happening here is that when a file gets opened by Notepad
first time, it gets memory mapped and then read. Thus, (most likely) the
entire file contents gets cached in the memory. MM works in such a way
that as long as there is enough free pages to satisfy system’s demand it
will not purge (free) pages that are taken by memory mapping / caching.
So, next time you open the same file in Notepad, new memory mapping will
be “inherited” from the previous open and (since the content is still in
memory) you will not see any FS calls, not even Fast I/O ones because
Notepad accesses file’s contents directly in the memory and as long as
those pages stay resident (not swapped away) nothing forces the system to
make FS calls.

Regards,

Vladimir