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    SubjectRe: [PATCH 1/9] io-throttle documentation
    On Fri, Apr 17, 2009 at 12:25:40PM +0200, Andrea Righi wrote:
    > So, what about implementing the bio-cgroup functionality as cgroup "page
    > tracking" infrastructure and provide the following interfaces:
    >
    > /*
    > * Encode the cgrp->css.id in page_group->flags

    sorry, I meant css_id(struct cgroup_subsys_state *css) here.

    > */
    > void set_cgroup_page_owner(struct page *page, struct cgroup *cgrp);
    >
    > /*
    > * Returns the cgroup owner of a page, decoding the cgroup id from
    > * page_cgroup->flags.
    > */
    > struct cgroup *get_cgroup_page_owner(struct page *page);

    Or better, even more generic:

    /*
    * Encode id in page_group->flags.
    */
    void set_page_id(struct page *page, unsigned short id);

    /*
    * Returns the id of a page, decoding it from page_cgroup->flags.
    */
    unsigned short get_page_id(struct page *page);

    Then we can use css_id() for cgroups, or any kind of ID for other
    potential users (dm-ioband, etc.).

    -Andrea

    >
    > This also wouldn't increase the size of page_cgroup because we can
    > encode the cgroup id in the unused bits of page_cgroup->flags, as
    > originally suggested by Kame.
    >
    > And I think it could be used also by dm-ioband, even if it's not a
    > cgroup-based subsystem... but I may be wrong. Ryo what's your opinion?


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