Re: The INN/mmap bug

From: Alexander Viro (viro@math.psu.edu)
Date: Mon Sep 18 2000 - 17:29:24 EDT

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    On Mon, 18 Sep 2000, Andreas Dilger wrote:

    > Alexander writes:
    > > * uptodate pages should never become non-uptodate.
    > > uptodate .. pages ... never have data _older_ than on disk
    >
    > This may actually be a problem in the future... what about shared access
    > block devices like FCAL or a distributed filesystem? It has to be
    > possible for pages to become non-uptodate in a sane way.

    So what the heck do you do when something modifies mmaped page when you
    get the change of on-disk one? Say it, writer is notified that write had
    been completed, sends packet to you and you flip a bit on a page that
    happens to be mmaped on the place where write had happened.

    Write-through-pagecache is OK, but write straight to disk bypassing the
    cache? Welcome to the fun with aliases...

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