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    SubjectRe: Getting FS access events

    On Tue, 15 May 2001, Richard Gooch wrote:

    > > What happens if you create a buffer cache entry? Does that
    > > invalidate the page cache one? Or do you just allow invalidates one
    > > way, and not the other? And why=
    > I just figured on one way invalidates, because that seems cheap and
    > easy and has some benefits. Invalidating the other way is costly, so
    > don't bother, even if there were some benefits.

    * create an instance in pagecache
    * start reading into buffer cache (doesn't invalidate, right?)
    * start writing using pagecache
    * lose the page
    * try to read it (via pagecache)
    Woops - just found a copy in buffer cache, let's pick data from it.
    Pity that said data is obsolete...

    > So what happens if I dd from the block device and also from a file on
    > the mounted FS, where that file overlaps the bnums I dd'ed? Do we get
    > two copies in the page cache? One for the block device access, and one
    > for the file access?


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