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    SubjectRe: [PATCH 02/10] Common flat fair queuing code in elevaotor layer
    On Wed, Apr 01, 2009 at 09:06:40PM -0700, Divyesh Shah wrote:
    > On Wed, Mar 11, 2009 at 6:56 PM, Vivek Goyal <vgoyal@redhat.com> wrote:
    > > +/*
    > > + * elv_exit_fq_data is called before we call elevator_exit_fn. Before
    > > + * we ask elevator to cleanup its queues, we do the cleanup here so
    > > + * that all the group and idle tree references to ioq are dropped. Later
    > > + * during elevator cleanup, ioc reference will be dropped which will lead
    > > + * to removal of ioscheduler queue as well as associated ioq object.
    > > + */
    > > +void elv_exit_fq_data(struct elevator_queue *e)
    > > +{
    > > + struct elv_fq_data *efqd = &e->efqd;
    > > + struct request_queue *q = efqd->queue;
    > > +
    > > + if (!elv_iosched_fair_queuing_enabled(e))
    > > + return;
    > > +
    > > + elv_shutdown_timer_wq(e);
    > > +
    > > + spin_lock_irq(q->queue_lock);
    > > + /* This should drop all the idle tree references of ioq */
    > > + elv_free_idle_ioq_list(e);
    > > + spin_unlock_irq(q->queue_lock);
    > > +
    > > + elv_shutdown_timer_wq(e);
    > > +
    > > + BUG_ON(timer_pending(&efqd->idle_slice_timer));
    > > + io_free_root_group(e);
    > > +}
    > >
    >
    > Hi Vivek,
    > When cleaning up the elv_fq_data and ioqs for the iogs
    > associated with a device on elv_exit(), I don't see any iogs except
    > the root group being freed. In io_disconnect_groups() you remove the
    > ioqs from each of the iog and move them to the root iog and then
    > delete the root iog. Am I missing something here or are there leftover
    > iogs at elv_exit?

    Hi Divyesh,

    io_groups are linked in two lists. One list is maintained by io_cgroup
    to keep track of how many io_groups are there associated with this
    cgroup and other list is maintained in elv_fq_data to keep track of
    how many io_groups are actually doing IO to this device.

    Upon elevator exit, we remove the io_groups (io_disconnect_groups())from the
    list maintained by elv_fq_data but we don't free them up. Freeing up is
    finally done when cgroup is being deleted (iocg_destroy()).

    Thanks
    Vivek


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