Re: [RFC][PATCH 10/11] blkiocg async: Async queue per cfq_group

[Munehiro Ikeda <m-ikeda@ds.jp.nec.com>]

Nauman Rafique wrote, on 08/13/2010 07:01 PM:
> On Fri, Aug 13, 2010 at 2:00 PM, Munehiro Ikeda<m-ikeda@ds.jp.nec.com>  wrote:
>> Nauman Rafique wrote, on 08/12/2010 09:24 PM:
>>>
>>> Muuhh,
>>> I do not understand the motivation behind making cfq_io_context per
>>> cgroup. We can extract cgroup id from bio, use that to lookup cgroup
>>> and its async queues. What am I missing?
>>
>> What cgroup ID can suggest is only cgroup to which the thread belongs,
>> but not the thread itself.  This means that IO priority and IO prio-class
>> can't be determined by cgroup ID.
>
> One way to do it would be to get ioprio and class from the context
> that is used to submit the async request. IO priority and class is
> tied to a thread anyways. And the io context of that thread can be
> used to retrieve those values. Even if a thread is submitting IOs to
> different cgroups, I don't see how you can apply different IO priority
> and class to its async IOs for different cgroups. Please let me know
> if it does not make sense.

My talking about IO prio might be misleading and pointless, sorry.
I was confused IO context of flush thread and thread which dirtied
a page.

Then, reason why making cfq_io_context per cgroup.
That is simply because the current code retrieves cfqq from
cfq_io_context by cic_to_cfqq().

As you said, we can lookup cgroup by cgroup ID and its async queue.
This is done by cfq_get_queue() and cfq_async_queue_prio().  So if
we change all call of cic_to_cfqq() into cfq_get_queue() (or slightly
changed version of cfq_get_queue() ), we may avoid making cfq_io_context
per cgroup.

Which approach is better depends on the complexity of the patch.  I chose
the former approach, but if the second approach is more simple,
it is better.  I need to think it over and am feeling that the second
approach would be nicer.  Thanks for the suggestion.


>> The pointers of async queues are held in cfqg->async_cfqq[class][prio].
>> It is impossible to find out which queue is appropriate by only cgroup
>> ID if considering IO priority.
>>
>> Frankly speaking, I'm not 100% confident if IO priority should be
>> applied on async write IOs, but anyway, I made up my mind to keep the
>> current scheme.
>>
>> Do I make sense?  If you have any other idea, I am glad to hear.
>>
>>
>> Thanks,
>> Muuhh
>>
>>
>>>
>>> On Thu, Jul 8, 2010 at 8:22 PM, Munehiro Ikeda<m-ikeda@ds.jp.nec.com>
>>>   wrote:
>>>>
>>>> This is the main body for async capability of blkio controller.
>>>> The basic ideas are
>>>>   - To move async queues from cfq_data to cfq_group, and
>>>>   - To associate cfq_io_context with cfq_group
>>>>
>>>> Each cfq_io_context, which was created per an io_context
>>>> per a device, is now created per an io_context per a cfq_group.
>>>> Each cfq_group is created per a cgroup per a device, so
>>>> cfq_io_context is now resulted in to be created per
>>>> an io_context per a cgroup per a device.
>>>>
>>>> To protect link between cfq_io_context and cfq_group,
>>>> locking code is modified in several parts.
>>>>
>>>> ToDo:
>>>> - Lock protection still might be imperfect and more investigation
>>>>   is needed.
>>>>
>>>> - cic_index of root cfq_group (cfqd->root_group.cic_index) is not
>>>>   removed and lasts beyond elevator switching.
>>>>   This issues should be solved.
>>>>
>>>> Signed-off-by: Munehiro "Muuhh" Ikeda<m-ikeda@ds.jp.nec.com>
>>>> ---
>>>>   block/cfq-iosched.c       |  277
>>>> ++++++++++++++++++++++++++++-----------------
>>>>   include/linux/iocontext.h |    2 +-
>>>>   2 files changed, 175 insertions(+), 104 deletions(-)
>>>>
>>>> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
>>>> index 68f76e9..4186c30 100644
>>>> --- a/block/cfq-iosched.c
>>>> +++ b/block/cfq-iosched.c
>>>> @@ -191,10 +191,23 @@ struct cfq_group {
>>>>         struct cfq_rb_root service_trees[2][3];
>>>>         struct cfq_rb_root service_tree_idle;
>>>>
>>>> +       /*
>>>> +        * async queue for each priority case
>>>> +        */
>>>> +       struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
>>>> +       struct cfq_queue *async_idle_cfqq;
>>>> +
>>>>         unsigned long saved_workload_slice;
>>>>         enum wl_type_t saved_workload;
>>>>         enum wl_prio_t saved_serving_prio;
>>>>         struct blkio_group blkg;
>>>> +       struct cfq_data *cfqd;
>>>> +
>>>> +       /* lock for cic_list */
>>>> +       spinlock_t lock;
>>>> +       unsigned int cic_index;
>>>> +       struct list_head cic_list;
>>>> +
>>>>   #ifdef CONFIG_CFQ_GROUP_IOSCHED
>>>>         struct hlist_node cfqd_node;
>>>>         atomic_t ref;
>>>> @@ -254,12 +267,6 @@ struct cfq_data {
>>>>         struct cfq_queue *active_queue;
>>>>         struct cfq_io_context *active_cic;
>>>>
>>>> -       /*
>>>> -        * async queue for each priority case
>>>> -        */
>>>> -       struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
>>>> -       struct cfq_queue *async_idle_cfqq;
>>>> -
>>>>         sector_t last_position;
>>>>
>>>>         /*
>>>> @@ -275,8 +282,6 @@ struct cfq_data {
>>>>         unsigned int cfq_latency;
>>>>         unsigned int cfq_group_isolation;
>>>>
>>>> -       unsigned int cic_index;
>>>> -       struct list_head cic_list;
>>>>
>>>>         /*
>>>>          * Fallback dummy cfqq for extreme OOM conditions
>>>> @@ -418,10 +423,16 @@ static inline int cfqg_busy_async_queues(struct
>>>> cfq_data *cfqd,
>>>>   }
>>>>
>>>>   static void cfq_dispatch_insert(struct request_queue *, struct request
>>>> *);
>>>> +static void __cfq_exit_single_io_context(struct cfq_data *,
>>>> +                                        struct cfq_group *,
>>>> +                                        struct cfq_io_context *);
>>>>   static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool,
>>>> -                                      struct io_context *, gfp_t);
>>>> +                                      struct cfq_io_context *, gfp_t);
>>>>   static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
>>>> -                                               struct io_context *);
>>>> +                                            struct cfq_group *,
>>>> +                                            struct io_context *);
>>>> +static void cfq_put_async_queues(struct cfq_group *);
>>>> +static int cfq_alloc_cic_index(void);
>>>>
>>>>   static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
>>>>                                             bool is_sync)
>>>> @@ -438,17 +449,28 @@ static inline void cic_set_cfqq(struct
>>>> cfq_io_context *cic,
>>>>   #define CIC_DEAD_KEY   1ul
>>>>   #define CIC_DEAD_INDEX_SHIFT   1
>>>>
>>>> -static inline void *cfqd_dead_key(struct cfq_data *cfqd)
>>>> +static inline void *cfqg_dead_key(struct cfq_group *cfqg)
>>>>   {
>>>> -       return (void *)(cfqd->cic_index<<    CIC_DEAD_INDEX_SHIFT |
>>>> CIC_DEAD_KEY);
>>>> +       return (void *)(cfqg->cic_index<<    CIC_DEAD_INDEX_SHIFT |
>>>> CIC_DEAD_KEY);
>>>> +}
>>>> +
>>>> +static inline struct cfq_group *cic_to_cfqg(struct cfq_io_context *cic)
>>>> +{
>>>> +       struct cfq_group *cfqg = cic->key;
>>>> +
>>>> +       if (unlikely((unsigned long) cfqg&    CIC_DEAD_KEY))
>>>> +               cfqg = NULL;
>>>> +
>>>> +       return cfqg;
>>>>   }
>>>>
>>>>   static inline struct cfq_data *cic_to_cfqd(struct cfq_io_context *cic)
>>>>   {
>>>> -       struct cfq_data *cfqd = cic->key;
>>>> +       struct cfq_data *cfqd = NULL;
>>>> +       struct cfq_group *cfqg = cic_to_cfqg(cic);
>>>>
>>>> -       if (unlikely((unsigned long) cfqd&    CIC_DEAD_KEY))
>>>> -               return NULL;
>>>> +       if (likely(cfqg))
>>>> +               cfqd =  cfqg->cfqd;
>>>>
>>>>         return cfqd;
>>>>   }
>>>> @@ -959,12 +981,12 @@ cfq_update_blkio_group_weight(struct blkio_group
>>>> *blkg, unsigned int weight)
>>>>   }
>>>>
>>>>   static struct cfq_group *
>>>> -cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int
>>>> create)
>>>> +cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct blkio_cgroup *blkcg,
>>>> +                   int create)
>>>>   {
>>>> -       struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
>>>>         struct cfq_group *cfqg = NULL;
>>>>         void *key = cfqd;
>>>> -       int i, j;
>>>> +       int i, j, idx;
>>>>         struct cfq_rb_root *st;
>>>>         struct backing_dev_info *bdi =&cfqd->queue->backing_dev_info;
>>>>         unsigned int major, minor;
>>>> @@ -978,14 +1000,21 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct
>>>> cgroup *cgroup, int create)
>>>>         if (cfqg || !create)
>>>>                 goto done;
>>>>
>>>> +       idx = cfq_alloc_cic_index();
>>>> +       if (idx<    0)
>>>> +               goto done;
>>>> +
>>>>         cfqg = kzalloc_node(sizeof(*cfqg), GFP_ATOMIC, cfqd->queue->node);
>>>>         if (!cfqg)
>>>> -               goto done;
>>>> +               goto err;
>>>>
>>>>         for_each_cfqg_st(cfqg, i, j, st)
>>>>                 *st = CFQ_RB_ROOT;
>>>>         RB_CLEAR_NODE(&cfqg->rb_node);
>>>>
>>>> +       spin_lock_init(&cfqg->lock);
>>>> +       INIT_LIST_HEAD(&cfqg->cic_list);
>>>> +
>>>>         /*
>>>>          * Take the initial reference that will be released on destroy
>>>>          * This can be thought of a joint reference by cgroup and
>>>> @@ -1002,7 +1031,14 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct
>>>> cgroup *cgroup, int create)
>>>>
>>>>         /* Add group on cfqd list */
>>>>         hlist_add_head(&cfqg->cfqd_node,&cfqd->cfqg_list);
>>>> +       cfqg->cfqd = cfqd;
>>>> +       cfqg->cic_index = idx;
>>>> +       goto done;
>>>>
>>>> +err:
>>>> +       spin_lock(&cic_index_lock);
>>>> +       ida_remove(&cic_index_ida, idx);
>>>> +       spin_unlock(&cic_index_lock);
>>>>   done:
>>>>         return cfqg;
>>>>   }
>>>> @@ -1095,10 +1131,6 @@ static inline struct cfq_group
>>>> *cfq_ref_get_cfqg(struct cfq_group *cfqg)
>>>>
>>>>   static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group
>>>> *cfqg)
>>>>   {
>>>> -       /* Currently, all async queues are mapped to root group */
>>>> -       if (!cfq_cfqq_sync(cfqq))
>>>> -               cfqg =&cfqq->cfqd->root_group;
>>>> -
>>>>         cfqq->cfqg = cfqg;
>>>>         /* cfqq reference on cfqg */
>>>>         atomic_inc(&cfqq->cfqg->ref);
>>>> @@ -1114,6 +1146,16 @@ static void cfq_put_cfqg(struct cfq_group *cfqg)
>>>>                 return;
>>>>         for_each_cfqg_st(cfqg, i, j, st)
>>>>                 BUG_ON(!RB_EMPTY_ROOT(&st->rb) || st->active != NULL);
>>>> +
>>>> +       /**
>>>> +        * ToDo:
>>>> +        * root_group never reaches here and cic_index is never
>>>> +        * removed.  Unused cic_index lasts by elevator switching.
>>>> +        */
>>>> +       spin_lock(&cic_index_lock);
>>>> +       ida_remove(&cic_index_ida, cfqg->cic_index);
>>>> +       spin_unlock(&cic_index_lock);
>>>> +
>>>>         kfree(cfqg);
>>>>   }
>>>>
>>>> @@ -1122,6 +1164,15 @@ static void cfq_destroy_cfqg(struct cfq_data
>>>> *cfqd, struct cfq_group *cfqg)
>>>>         /* Something wrong if we are trying to remove same group twice */
>>>>         BUG_ON(hlist_unhashed(&cfqg->cfqd_node));
>>>>
>>>> +       while (!list_empty(&cfqg->cic_list)) {
>>>> +               struct cfq_io_context *cic =
>>>> list_entry(cfqg->cic_list.next,
>>>> +                                                       struct
>>>> cfq_io_context,
>>>> +                                                       group_list);
>>>> +
>>>> +               __cfq_exit_single_io_context(cfqd, cfqg, cic);
>>>> +       }
>>>> +
>>>> +       cfq_put_async_queues(cfqg);
>>>>         hlist_del_init(&cfqg->cfqd_node);
>>>>
>>>>         /*
>>>> @@ -1497,10 +1548,12 @@ static struct request *
>>>>   cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
>>>>   {
>>>>         struct task_struct *tsk = current;
>>>> +       struct cfq_group *cfqg;
>>>>         struct cfq_io_context *cic;
>>>>         struct cfq_queue *cfqq;
>>>>
>>>> -       cic = cfq_cic_lookup(cfqd, tsk->io_context);
>>>> +       cfqg = cfq_get_cfqg(cfqd, bio, 0);
>>>> +       cic = cfq_cic_lookup(cfqd, cfqg, tsk->io_context);
>>>>         if (!cic)
>>>>                 return NULL;
>>>>
>>>> @@ -1611,6 +1664,7 @@ static int cfq_allow_merge(struct request_queue *q,
>>>> struct request *rq,
>>>>                            struct bio *bio)
>>>>   {
>>>>         struct cfq_data *cfqd = q->elevator->elevator_data;
>>>> +       struct cfq_group *cfqg;
>>>>         struct cfq_io_context *cic;
>>>>         struct cfq_queue *cfqq;
>>>>
>>>> @@ -1624,7 +1678,8 @@ static int cfq_allow_merge(struct request_queue *q,
>>>> struct request *rq,
>>>>          * Lookup the cfqq that this bio will be queued with. Allow
>>>>          * merge only if rq is queued there.
>>>>          */
>>>> -       cic = cfq_cic_lookup(cfqd, current->io_context);
>>>> +       cfqg = cfq_get_cfqg(cfqd, bio, 0);
>>>> +       cic = cfq_cic_lookup(cfqd, cfqg, current->io_context);
>>>>         if (!cic)
>>>>                 return false;
>>>>
>>>> @@ -2667,17 +2722,18 @@ static void cfq_exit_cfqq(struct cfq_data *cfqd,
>>>> struct cfq_queue *cfqq)
>>>>   }
>>>>
>>>>   static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
>>>> +                                        struct cfq_group *cfqg,
>>>>                                          struct cfq_io_context *cic)
>>>>   {
>>>>         struct io_context *ioc = cic->ioc;
>>>>
>>>> -       list_del_init(&cic->queue_list);
>>>> +       list_del_init(&cic->group_list);
>>>>
>>>>         /*
>>>>          * Make sure dead mark is seen for dead queues
>>>>          */
>>>>         smp_wmb();
>>>> -       cic->key = cfqd_dead_key(cfqd);
>>>> +       cic->key = cfqg_dead_key(cfqg);
>>>>
>>>>         if (ioc->ioc_data == cic)
>>>>                 rcu_assign_pointer(ioc->ioc_data, NULL);
>>>> @@ -2696,23 +2752,23 @@ static void __cfq_exit_single_io_context(struct
>>>> cfq_data *cfqd,
>>>>   static void cfq_exit_single_io_context(struct io_context *ioc,
>>>>                                        struct cfq_io_context *cic)
>>>>   {
>>>> -       struct cfq_data *cfqd = cic_to_cfqd(cic);
>>>> +       struct cfq_group *cfqg = cic_to_cfqg(cic);
>>>>
>>>> -       if (cfqd) {
>>>> -               struct request_queue *q = cfqd->queue;
>>>> +       if (cfqg) {
>>>> +               struct cfq_data *cfqd = cfqg->cfqd;
>>>>                 unsigned long flags;
>>>>
>>>> -               spin_lock_irqsave(q->queue_lock, flags);
>>>> +               spin_lock_irqsave(&cfqg->lock, flags);
>>>>
>>>>                 /*
>>>>                  * Ensure we get a fresh copy of the ->key to prevent
>>>>                  * race between exiting task and queue
>>>>                  */
>>>>                 smp_read_barrier_depends();
>>>> -               if (cic->key == cfqd)
>>>> -                       __cfq_exit_single_io_context(cfqd, cic);
>>>> +               if (cic->key == cfqg)
>>>> +                       __cfq_exit_single_io_context(cfqd, cfqg, cic);
>>>>
>>>> -               spin_unlock_irqrestore(q->queue_lock, flags);
>>>> +               spin_unlock_irqrestore(&cfqg->lock, flags);
>>>>         }
>>>>   }
>>>>
>>>> @@ -2734,7 +2790,7 @@ cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t
>>>> gfp_mask)
>>>>
>>>>   cfqd->queue->node);
>>>>         if (cic) {
>>>>                 cic->last_end_request = jiffies;
>>>> -               INIT_LIST_HEAD(&cic->queue_list);
>>>> +               INIT_LIST_HEAD(&cic->group_list);
>>>>                 INIT_HLIST_NODE(&cic->cic_list);
>>>>                 cic->dtor = cfq_free_io_context;
>>>>                 cic->exit = cfq_exit_io_context;
>>>> @@ -2801,8 +2857,7 @@ static void changed_ioprio(struct io_context *ioc,
>>>> struct cfq_io_context *cic)
>>>>         cfqq = cic->cfqq[BLK_RW_ASYNC];
>>>>         if (cfqq) {
>>>>                 struct cfq_queue *new_cfqq;
>>>> -               new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc,
>>>> -                                               GFP_ATOMIC);
>>>> +               new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic,
>>>> GFP_ATOMIC);
>>>>                 if (new_cfqq) {
>>>>                         cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
>>>>                         cfq_put_queue(cfqq);
>>>> @@ -2879,16 +2934,14 @@ static void cfq_ioc_set_cgroup(struct io_context
>>>> *ioc)
>>>>
>>>>   static struct cfq_queue *
>>>>   cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
>>>> -                    struct io_context *ioc, gfp_t gfp_mask)
>>>> +                    struct cfq_io_context *cic, gfp_t gfp_mask)
>>>>   {
>>>>         struct cfq_queue *cfqq, *new_cfqq = NULL;
>>>> -       struct cfq_io_context *cic;
>>>> +       struct io_context *ioc = cic->ioc;
>>>>         struct cfq_group *cfqg;
>>>>
>>>>   retry:
>>>> -       cfqg = cfq_get_cfqg(cfqd, NULL, 1);
>>>> -       cic = cfq_cic_lookup(cfqd, ioc);
>>>> -       /* cic always exists here */
>>>> +       cfqg = cic_to_cfqg(cic);
>>>>         cfqq = cic_to_cfqq(cic, is_sync);
>>>>
>>>>         /*
>>>> @@ -2930,36 +2983,38 @@ retry:
>>>>   }
>>>>
>>>>   static struct cfq_queue **
>>>> -cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int
>>>> ioprio)
>>>> +cfq_async_queue_prio(struct cfq_group *cfqg, int ioprio_class, int
>>>> ioprio)
>>>>   {
>>>>         switch (ioprio_class) {
>>>>         case IOPRIO_CLASS_RT:
>>>> -               return&cfqd->async_cfqq[0][ioprio];
>>>> +               return&cfqg->async_cfqq[0][ioprio];
>>>>         case IOPRIO_CLASS_BE:
>>>> -               return&cfqd->async_cfqq[1][ioprio];
>>>> +               return&cfqg->async_cfqq[1][ioprio];
>>>>         case IOPRIO_CLASS_IDLE:
>>>> -               return&cfqd->async_idle_cfqq;
>>>> +               return&cfqg->async_idle_cfqq;
>>>>         default:
>>>>                 BUG();
>>>>         }
>>>>   }
>>>>
>>>>   static struct cfq_queue *
>>>> -cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context
>>>> *ioc,
>>>> +cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_context
>>>> *cic,
>>>>               gfp_t gfp_mask)
>>>>   {
>>>> +       struct io_context *ioc = cic->ioc;
>>>>         const int ioprio = task_ioprio(ioc);
>>>>         const int ioprio_class = task_ioprio_class(ioc);
>>>> +       struct cfq_group *cfqg = cic_to_cfqg(cic);
>>>>         struct cfq_queue **async_cfqq = NULL;
>>>>         struct cfq_queue *cfqq = NULL;
>>>>
>>>>         if (!is_sync) {
>>>> -               async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class,
>>>> ioprio);
>>>> +               async_cfqq = cfq_async_queue_prio(cfqg, ioprio_class,
>>>> ioprio);
>>>>                 cfqq = *async_cfqq;
>>>>         }
>>>>
>>>>         if (!cfqq)
>>>> -               cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc,
>>>> gfp_mask);
>>>> +               cfqq = cfq_find_alloc_queue(cfqd, is_sync, cic,
>>>> gfp_mask);
>>>>
>>>>         /*
>>>>          * pin the queue now that it's allocated, scheduler exit will
>>>> prune it
>>>> @@ -2977,19 +3032,19 @@ cfq_get_queue(struct cfq_data *cfqd, bool
>>>> is_sync, struct io_context *ioc,
>>>>   * We drop cfq io contexts lazily, so we may find a dead one.
>>>>   */
>>>>   static void
>>>> -cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
>>>> -                 struct cfq_io_context *cic)
>>>> +cfq_drop_dead_cic(struct cfq_data *cfqd, struct cfq_group *cfqg,
>>>> +                 struct io_context *ioc, struct cfq_io_context *cic)
>>>>   {
>>>>         unsigned long flags;
>>>>
>>>> -       WARN_ON(!list_empty(&cic->queue_list));
>>>> -       BUG_ON(cic->key != cfqd_dead_key(cfqd));
>>>> +       WARN_ON(!list_empty(&cic->group_list));
>>>> +       BUG_ON(cic->key != cfqg_dead_key(cfqg));
>>>>
>>>>         spin_lock_irqsave(&ioc->lock, flags);
>>>>
>>>>         BUG_ON(ioc->ioc_data == cic);
>>>>
>>>> -       radix_tree_delete(&ioc->radix_root, cfqd->cic_index);
>>>> +       radix_tree_delete(&ioc->radix_root, cfqg->cic_index);
>>>>         hlist_del_rcu(&cic->cic_list);
>>>>         spin_unlock_irqrestore(&ioc->lock, flags);
>>>>
>>>> @@ -2997,11 +3052,14 @@ cfq_drop_dead_cic(struct cfq_data *cfqd, struct
>>>> io_context *ioc,
>>>>   }
>>>>
>>>>   static struct cfq_io_context *
>>>> -cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
>>>> +cfq_cic_lookup(struct cfq_data *cfqd, struct cfq_group *cfqg,
>>>> +              struct io_context *ioc)
>>>>   {
>>>>         struct cfq_io_context *cic;
>>>>         unsigned long flags;
>>>>
>>>> +       if (!cfqg)
>>>> +               return NULL;
>>>>         if (unlikely(!ioc))
>>>>                 return NULL;
>>>>
>>>> @@ -3011,18 +3069,18 @@ cfq_cic_lookup(struct cfq_data *cfqd, struct
>>>> io_context *ioc)
>>>>          * we maintain a last-hit cache, to avoid browsing over the tree
>>>>          */
>>>>         cic = rcu_dereference(ioc->ioc_data);
>>>> -       if (cic&&    cic->key == cfqd) {
>>>> +       if (cic&&    cic->key == cfqg) {
>>>>                 rcu_read_unlock();
>>>>                 return cic;
>>>>         }
>>>>
>>>>         do {
>>>> -               cic = radix_tree_lookup(&ioc->radix_root,
>>>> cfqd->cic_index);
>>>> +               cic = radix_tree_lookup(&ioc->radix_root,
>>>> cfqg->cic_index);
>>>>                 rcu_read_unlock();
>>>>                 if (!cic)
>>>>                         break;
>>>> -               if (unlikely(cic->key != cfqd)) {
>>>> -                       cfq_drop_dead_cic(cfqd, ioc, cic);
>>>> +               if (unlikely(cic->key != cfqg)) {
>>>> +                       cfq_drop_dead_cic(cfqd, cfqg, ioc, cic);
>>>>                         rcu_read_lock();
>>>>                         continue;
>>>>                 }
>>>> @@ -3037,24 +3095,25 @@ cfq_cic_lookup(struct cfq_data *cfqd, struct
>>>> io_context *ioc)
>>>>   }
>>>>
>>>>   /*
>>>> - * Add cic into ioc, using cfqd as the search key. This enables us to
>>>> lookup
>>>> + * Add cic into ioc, using cfqg as the search key. This enables us to
>>>> lookup
>>>>   * the process specific cfq io context when entered from the block layer.
>>>> - * Also adds the cic to a per-cfqd list, used when this queue is
>>>> removed.
>>>> + * Also adds the cic to a per-cfqg list, used when the group is removed.
>>>> + * request_queue lock must be held.
>>>>   */
>>>> -static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
>>>> -                       struct cfq_io_context *cic, gfp_t gfp_mask)
>>>> +static int cfq_cic_link(struct cfq_data *cfqd, struct cfq_group *cfqg,
>>>> +                       struct io_context *ioc, struct cfq_io_context
>>>> *cic)
>>>>   {
>>>>         unsigned long flags;
>>>>         int ret;
>>>>
>>>> -       ret = radix_tree_preload(gfp_mask);
>>>> +       ret = radix_tree_preload(GFP_ATOMIC);
>>>>         if (!ret) {
>>>>                 cic->ioc = ioc;
>>>> -               cic->key = cfqd;
>>>> +               cic->key = cfqg;
>>>>
>>>>                 spin_lock_irqsave(&ioc->lock, flags);
>>>>                 ret = radix_tree_insert(&ioc->radix_root,
>>>> -                                               cfqd->cic_index, cic);
>>>> +                                               cfqg->cic_index, cic);
>>>>                 if (!ret)
>>>>                         hlist_add_head_rcu(&cic->cic_list,&ioc->cic_list);
>>>>                 spin_unlock_irqrestore(&ioc->lock, flags);
>>>> @@ -3062,9 +3121,9 @@ static int cfq_cic_link(struct cfq_data *cfqd,
>>>> struct io_context *ioc,
>>>>                 radix_tree_preload_end();
>>>>
>>>>                 if (!ret) {
>>>> -                       spin_lock_irqsave(cfqd->queue->queue_lock,
>>>> flags);
>>>> -                       list_add(&cic->queue_list,&cfqd->cic_list);
>>>> -                       spin_unlock_irqrestore(cfqd->queue->queue_lock,
>>>> flags);
>>>> +                       spin_lock_irqsave(&cfqg->lock, flags);
>>>> +                       list_add(&cic->group_list,&cfqg->cic_list);
>>>> +                       spin_unlock_irqrestore(&cfqg->lock, flags);
>>>>                 }
>>>>         }
>>>>
>>>> @@ -3080,10 +3139,12 @@ static int cfq_cic_link(struct cfq_data *cfqd,
>>>> struct io_context *ioc,
>>>>   * than one device managed by cfq.
>>>>   */
>>>>   static struct cfq_io_context *
>>>> -cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
>>>> +cfq_get_io_context(struct cfq_data *cfqd, struct bio *bio, gfp_t
>>>> gfp_mask)
>>>>   {
>>>>         struct io_context *ioc = NULL;
>>>>         struct cfq_io_context *cic;
>>>> +       struct cfq_group *cfqg, *cfqg2;
>>>> +       unsigned long flags;
>>>>
>>>>         might_sleep_if(gfp_mask&    __GFP_WAIT);
>>>>
>>>> @@ -3091,18 +3152,38 @@ cfq_get_io_context(struct cfq_data *cfqd, gfp_t
>>>> gfp_mask)
>>>>         if (!ioc)
>>>>                 return NULL;
>>>>
>>>> -       cic = cfq_cic_lookup(cfqd, ioc);
>>>> +       spin_lock_irqsave(cfqd->queue->queue_lock, flags);
>>>> +retry_cfqg:
>>>> +       cfqg = cfq_get_cfqg(cfqd, bio, 1);
>>>> +retry_cic:
>>>> +       cic = cfq_cic_lookup(cfqd, cfqg, ioc);
>>>>         if (cic)
>>>>                 goto out;
>>>> +       spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
>>>>
>>>>         cic = cfq_alloc_io_context(cfqd, gfp_mask);
>>>>         if (cic == NULL)
>>>>                 goto err;
>>>>
>>>> -       if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
>>>> +       spin_lock_irqsave(cfqd->queue->queue_lock, flags);
>>>> +
>>>> +       /* check the consistency breakage during unlock period */
>>>> +       cfqg2 = cfq_get_cfqg(cfqd, bio, 0);
>>>> +       if (cfqg != cfqg2) {
>>>> +               cfq_cic_free(cic);
>>>> +               if (!cfqg2)
>>>> +                       goto retry_cfqg;
>>>> +               else {
>>>> +                       cfqg = cfqg2;
>>>> +                       goto retry_cic;
>>>> +               }
>>>> +       }
>>>> +
>>>> +       if (cfq_cic_link(cfqd, cfqg, ioc, cic))
>>>>                 goto err_free;
>>>>
>>>>   out:
>>>> +       spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
>>>>         smp_read_barrier_depends();
>>>>         if (unlikely(ioc->ioprio_changed))
>>>>                 cfq_ioc_set_ioprio(ioc);
>>>> @@ -3113,6 +3194,7 @@ out:
>>>>   #endif
>>>>         return cic;
>>>>   err_free:
>>>> +       spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
>>>>         cfq_cic_free(cic);
>>>>   err:
>>>>         put_io_context(ioc);
>>>> @@ -3537,6 +3619,7 @@ static inline int __cfq_may_queue(struct cfq_queue
>>>> *cfqq)
>>>>   static int cfq_may_queue(struct request_queue *q, struct bio *bio, int
>>>> rw)
>>>>   {
>>>>         struct cfq_data *cfqd = q->elevator->elevator_data;
>>>> +       struct cfq_group *cfqg;
>>>>         struct task_struct *tsk = current;
>>>>         struct cfq_io_context *cic;
>>>>         struct cfq_queue *cfqq;
>>>> @@ -3547,7 +3630,8 @@ static int cfq_may_queue(struct request_queue *q,
>>>> struct bio *bio, int rw)
>>>>          * so just lookup a possibly existing queue, or return 'may queue'
>>>>          * if that fails
>>>>          */
>>>> -       cic = cfq_cic_lookup(cfqd, tsk->io_context);
>>>> +       cfqg = cfq_get_cfqg(cfqd, bio, 0);
>>>> +       cic = cfq_cic_lookup(cfqd, cfqg, tsk->io_context);
>>>>         if (!cic)
>>>>                 return ELV_MQUEUE_MAY;
>>>>
>>>> @@ -3636,7 +3720,7 @@ cfq_set_request(struct request_queue *q, struct
>>>> request *rq, struct bio *bio,
>>>>
>>>>         might_sleep_if(gfp_mask&    __GFP_WAIT);
>>>>
>>>> -       cic = cfq_get_io_context(cfqd, gfp_mask);
>>>> +       cic = cfq_get_io_context(cfqd, bio, gfp_mask);
>>>>
>>>>         spin_lock_irqsave(q->queue_lock, flags);
>>>>
>>>> @@ -3646,7 +3730,7 @@ cfq_set_request(struct request_queue *q, struct
>>>> request *rq, struct bio *bio,
>>>>   new_queue:
>>>>         cfqq = cic_to_cfqq(cic, is_sync);
>>>>         if (!cfqq || cfqq ==&cfqd->oom_cfqq) {
>>>> -               cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
>>>> +               cfqq = cfq_get_queue(cfqd, is_sync, cic, gfp_mask);
>>>>                 cic_set_cfqq(cic, cfqq, is_sync);
>>>>         } else {
>>>>                 /*
>>>> @@ -3762,19 +3846,19 @@ static void cfq_shutdown_timer_wq(struct cfq_data
>>>> *cfqd)
>>>>         cancel_work_sync(&cfqd->unplug_work);
>>>>   }
>>>>
>>>> -static void cfq_put_async_queues(struct cfq_data *cfqd)
>>>> +static void cfq_put_async_queues(struct cfq_group *cfqg)
>>>>   {
>>>>         int i;
>>>>
>>>>         for (i = 0; i<    IOPRIO_BE_NR; i++) {
>>>> -               if (cfqd->async_cfqq[0][i])
>>>> -                       cfq_put_queue(cfqd->async_cfqq[0][i]);
>>>> -               if (cfqd->async_cfqq[1][i])
>>>> -                       cfq_put_queue(cfqd->async_cfqq[1][i]);
>>>> +               if (cfqg->async_cfqq[0][i])
>>>> +                       cfq_put_queue(cfqg->async_cfqq[0][i]);
>>>> +               if (cfqg->async_cfqq[1][i])
>>>> +                       cfq_put_queue(cfqg->async_cfqq[1][i]);
>>>>         }
>>>>
>>>> -       if (cfqd->async_idle_cfqq)
>>>> -               cfq_put_queue(cfqd->async_idle_cfqq);
>>>> +       if (cfqg->async_idle_cfqq)
>>>> +               cfq_put_queue(cfqg->async_idle_cfqq);
>>>>   }
>>>>
>>>>   static void cfq_cfqd_free(struct rcu_head *head)
>>>> @@ -3794,15 +3878,6 @@ static void cfq_exit_queue(struct elevator_queue
>>>> *e)
>>>>         if (cfqd->active_queue)
>>>>                 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
>>>>
>>>> -       while (!list_empty(&cfqd->cic_list)) {
>>>> -               struct cfq_io_context *cic =
>>>> list_entry(cfqd->cic_list.next,
>>>> -                                                       struct
>>>> cfq_io_context,
>>>> -                                                       queue_list);
>>>> -
>>>> -               __cfq_exit_single_io_context(cfqd, cic);
>>>> -       }
>>>> -
>>>> -       cfq_put_async_queues(cfqd);
>>>>         cfq_release_cfq_groups(cfqd);
>>>>         cfq_blkiocg_del_blkio_group(&cfqd->root_group.blkg);
>>>>
>>>> @@ -3810,10 +3885,6 @@ static void cfq_exit_queue(struct elevator_queue
>>>> *e)
>>>>
>>>>         cfq_shutdown_timer_wq(cfqd);
>>>>
>>>> -       spin_lock(&cic_index_lock);
>>>> -       ida_remove(&cic_index_ida, cfqd->cic_index);
>>>> -       spin_unlock(&cic_index_lock);
>>>> -
>>>>         /* Wait for cfqg->blkg->key accessors to exit their grace periods.
>>>> */
>>>>         call_rcu(&cfqd->rcu, cfq_cfqd_free);
>>>>   }
>>>> @@ -3823,7 +3894,7 @@ static int cfq_alloc_cic_index(void)
>>>>         int index, error;
>>>>
>>>>         do {
>>>> -               if (!ida_pre_get(&cic_index_ida, GFP_KERNEL))
>>>> +               if (!ida_pre_get(&cic_index_ida, GFP_ATOMIC))
>>>>                         return -ENOMEM;
>>>>
>>>>                 spin_lock(&cic_index_lock);
>>>> @@ -3839,20 +3910,18 @@ static int cfq_alloc_cic_index(void)
>>>>   static void *cfq_init_queue(struct request_queue *q)
>>>>   {
>>>>         struct cfq_data *cfqd;
>>>> -       int i, j;
>>>> +       int i, j, idx;
>>>>         struct cfq_group *cfqg;
>>>>         struct cfq_rb_root *st;
>>>>
>>>> -       i = cfq_alloc_cic_index();
>>>> -       if (i<    0)
>>>> +       idx = cfq_alloc_cic_index();
>>>> +       if (idx<    0)
>>>>                 return NULL;
>>>>
>>>>         cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO,
>>>> q->node);
>>>>         if (!cfqd)
>>>>                 return NULL;
>>>>
>>>> -       cfqd->cic_index = i;
>>>> -
>>>>         /* Init root service tree */
>>>>         cfqd->grp_service_tree = CFQ_RB_ROOT;
>>>>
>>>> @@ -3861,6 +3930,9 @@ static void *cfq_init_queue(struct request_queue
>>>> *q)
>>>>         for_each_cfqg_st(cfqg, i, j, st)
>>>>                 *st = CFQ_RB_ROOT;
>>>>         RB_CLEAR_NODE(&cfqg->rb_node);
>>>> +       cfqg->cfqd = cfqd;
>>>> +       cfqg->cic_index = idx;
>>>> +       INIT_LIST_HEAD(&cfqg->cic_list);
>>>>
>>>>         /* Give preference to root group over other groups */
>>>>         cfqg->weight = 2*BLKIO_WEIGHT_DEFAULT;
>>>> @@ -3874,6 +3946,7 @@ static void *cfq_init_queue(struct request_queue
>>>> *q)
>>>>         rcu_read_lock();
>>>>         cfq_blkiocg_add_blkio_group(&blkio_root_cgroup,&cfqg->blkg,
>>>>                                         (void *)cfqd, 0);
>>>> +       hlist_add_head(&cfqg->cfqd_node,&cfqd->cfqg_list);
>>>>         rcu_read_unlock();
>>>>   #endif
>>>>         /*
>>>> @@ -3893,8 +3966,6 @@ static void *cfq_init_queue(struct request_queue
>>>> *q)
>>>>         atomic_inc(&cfqd->oom_cfqq.ref);
>>>>         cfq_link_cfqq_cfqg(&cfqd->oom_cfqq,&cfqd->root_group);
>>>>
>>>> -       INIT_LIST_HEAD(&cfqd->cic_list);
>>>> -
>>>>         cfqd->queue = q;
>>>>
>>>>         init_timer(&cfqd->idle_slice_timer);
>>>> diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h
>>>> index 64d5291..6c05b54 100644
>>>> --- a/include/linux/iocontext.h
>>>> +++ b/include/linux/iocontext.h
>>>> @@ -18,7 +18,7 @@ struct cfq_io_context {
>>>>         unsigned long ttime_samples;
>>>>         unsigned long ttime_mean;
>>>>
>>>> -       struct list_head queue_list;
>>>> +       struct list_head group_list;
>>>>         struct hlist_node cic_list;
>>>>
>>>>         void (*dtor)(struct io_context *); /* destructor */
>>>> --
>>>> 1.6.2.5
>>>> --
>>>> To unsubscribe from this list: send the line "unsubscribe linux-kernel"
>>>> in
>>>> the body of a message to majordomo@vger.kernel.org
>>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>> Please read the FAQ at  http://www.tux.org/lkml/
>>>>
>>>
>>
>> --
>> IKEDA, Munehiro
>>   NEC Corporation of America
>>     m-ikeda@ds.jp.nec.com
>>
>>
>

-- 
IKEDA, Munehiro
   NEC Corporation of America
     m-ikeda@ds.jp.nec.com