Fast I/O &. IRP_MJ_xxx

NTFSD
1

Hi,

As it comes from OSR FAQ there is no description of Fast I/O calls
and I just need to pass them through without any processing.
However I need to block I/O operations which can modify information
on disk on some conditions for a particular period of time. As I
understand I can do it by handling regular IRP_MJ_xxx calls and
doesn’t need to think about Fast I/O at all. Am I right?

P.S.
I’ve used FileMon and found that for every Fast I/O call, which is
interesting for me a corresponding IRP_MJ_xx call is received by the
filter, for example FileMon intercepts FASTIO_WRITE sent by the
process and then IRP_MJ_WRITE sent by the system.

Is it always true?

–
Roman

mailto:xxxxx@rbcmail.ru

2

Fast I/O read and write operate against the cache in all of the Windows
file systems. A 3rd party file system could do something “tricky” here,
I suppose, but in our implementations we obey this same rule - no
caching, no fast I/O.

Regards,

Tony

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

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Roman Kudinov
Sent: Friday, July 23, 2004 5:51 AM
To: ntfsd redirect
Subject: [ntfsd] Fast I/O &. IRP_MJ_xxx

Hi,

As it comes from OSR FAQ there is no description of Fast I/O calls and
I just need to pass them through without any processing.
However I need to block I/O operations which can modify information on
disk on some conditions for a particular period of time. As I
understand I can do it by handling regular IRP_MJ_xxx calls and doesn’t
need to think about Fast I/O at all. Am I right?

P.S.
I’ve used FileMon and found that for every Fast I/O call, which is
interesting for me a corresponding IRP_MJ_xx call is received by the
filter, for example FileMon intercepts FASTIO_WRITE sent by the process
and then IRP_MJ_WRITE sent by the system.

Is it always true?

–
Roman

mailto:xxxxx@rbcmail.ru

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

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