And if I recall corectly , even in the case of cached IO there is a big
coherency problem with networked (remote)
files in the case of writes.
Dan
----- Original Message -----
From: “Carl Appellof”
Newsgroups: ntfsd
To: “File Systems Developers”
Sent: Tuesday, March 11, 2003 6:46 PM
Subject: [ntfsd] Coherency - memory mapped & file write
> On a different subject, Nicholas Ryan recently wrote:
>
> > Since memory-mapping a file exposes the same pages used by the NT cache
> > manager to manage the filesystem cache for the file’s data,
> > modifications made by WriteFile (assuming you didn’t open the file with
> > the no-buffering flag) will immediately appear in the mapped memory, and
> > will be flushed out to disk by the lazy writer at some point in the
> > future
>
> Unless I misunderstand, this statement seems to imply that data written by
> WriteFile (buffered) will appear in any memory mapped section for that
file
> in a coherent manner. Is that true? Documentation on the Win32
> MapViewOfFile API says:
>
> > A mapped view of a file is not guaranteed to be coherent with a file
being
> accessed by the ReadFile or WriteFile function:
> My question: ARE there cases where the data in a mapped section ARE
coherent
> with data written to the same file by WriteFile ?
>
> Carl
>
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