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    SubjectRe: [RFC] [PATCH 0/6] Provide cgroup isolation for buffered writes.
    On Thu, Mar 10, 2011 at 10:08:03AM -0800, Justin TerAvest wrote:

    [..]
    > > I don't like to increase size of page_cgroup but I think you can record
    > > information without increasing size of page_cgroup.
    > >
    > > A) As Andrea did, encode it to pc->flags.
    > >   But I'm afraid that there is a racy case because memory cgroup uses some
    > >   test_and_set() bits.
    > > B) I wonder why the information cannot be recorded in page->private.
    > >   When page has buffers, you can record the information to buffer struct.
    > >   About swapio (if you take care of), you can record information to bio.
    >
    > Hi Kame,
    >
    > I'm concerned that by using something like buffer_heads stored in
    > page->private, we will only be supported on some filesystems and not
    > others. In addition, I'm not sure if all filesystems attach buffer
    > heads at the same time; if page->private is modified in the flusher
    > thread, we might not be able to determine the thread that dirtied the
    > page in the first place.

    I think the person who dirtied the page can store the information in
    page->private (assuming buffer heads were not generated) and if flusher
    thread later ends up generating buffer heads and ends up modifying
    page->private, this can be copied in buffer heads?

    Thanks
    Vivek
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