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

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

Nauman Rafique wrote, on 08/12/2010 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.
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
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>>
>

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