Re: Help Please! FSD failure in FsRtlAcquireFileForM- odWrite

NTFSD
1

In your file system, are you filling in the
FileObject->SectionObjectPointers field? If so, this indicates (to the
memory manager) that you support memory mapped files. That is a separate
issue from caching (which must be established via a call to the cache
manager).

Just as a guess - is it possible that the file in question was recently
accessed via notepad? I ask because Notepad DOES use memory mapped files.

Finally, you say “I also tell the I/O mgr that I don’t support paging…”
and I am curious as to what you mean by this.

Regards,

Tony

Tony Mason
Consulting Partner
OSR Open Systems Resources, Inc.
http://www.osr.com

-----Original Message-----
From: Greg Pearce [mailto:xxxxx@filetek.com]
Sent: Wednesday, December 26, 2001 7:44 AM
To: File Systems Developers
Subject: [ntfsd] Re: Help Please! FSD failure in FsRtlAcquireFileForModWrite

Thanks Dan - I appreciate the quick response!

I will admit that I’m still pretty new to all this stuff, and I’m amazed at
how quickly you responded and figured this out. I have a lot to learn!

My driver is a FSD, not a FSFD, and it’s running on win2k. I don’t support
fast i/o or paging at all, so I’m trying to figure out why this request
came to my FSD in the first place.

When the system inits my FSD, doesn’t it ask if fast i/o is possible, then
it remembers that (in the device object?) and should not attempt fast i/o
to my device? I also tell the I/O mgr that I don’t support paging… so
I’m confused as to why anything/anyone is bothering my FSD with these
IRPs.

Any more of your insight into this would be VERY welcome, and appreciated.

Thanks - Greg

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2

Tony,

I just discovered that I do actually set the
FileObject->SectionObjectPointers field… so I do support memory mapped
files (DOH!). The file in question wasn’t previously opened by Notepad,
but the program that does open it probably is (or MUST be) using memory
mapped files.

What I meant when I stated that “I also tell the I/O mgr that I dont
support paging” is really that I check a flag in the stack location
(SL_OPEN_PAGING_FILE) when I get an open request and fail the IRP with
“STATUS_ACCESS_DENIED” if it is paging I/O.

I should also add that I have determined that my FSD does not have a fast
i/o dispatch table at all, so I’m sure it doesn’t support fast i/o.

So I guess that answers that - about the memory mapped files - but I still
can’t understand why I’m getting the access violation in
FsRtlAcquireFileForModWrite. I can open files with notepad and it works
fine. I’d like to figure out which IRP is causing this to happen so I can
set a breakpoint on it’s processing routine and see what’s going on.

Again, I really appreciate any help you (and anyone else) can provide…

Thanks - Greg

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