Re: [PATCH v5 07/10] scsi: ufshpb: Add "Cold" regions timer

[Can Guo]

On 2021-03-16 17:21, Avri Altman wrote:
> > > +static void ufshpb_read_to_handler(struct work_struct *work)
> > > +{
> > > +     struct delayed_work *dwork = to_delayed_work(work);
> > > +     struct ufshpb_lu *hpb;
> > > +     struct victim_select_info *lru_info;
> > > +     struct ufshpb_region *rgn;
> > > +     unsigned long flags;
> > > +     LIST_HEAD(expired_list);
> > > +
> > > +     hpb = container_of(dwork, struct ufshpb_lu, ufshpb_read_to_work);
> > > +
> > > +     spin_lock_irqsave(&hpb->rgn_state_lock, flags);
> > > +
> > > +     lru_info = &hpb->lru_info;
> > > +
> > > +     list_for_each_entry(rgn, &lru_info->lh_lru_rgn, list_lru_rgn) {
> > > +             bool timedout = ktime_after(ktime_get(), rgn->read_timeout);
> > > +
> > > +             if (timedout) {
> > > +                     rgn->read_timeout_expiries--;
> > > +                     if (is_rgn_dirty(rgn) ||
> > > +                         rgn->read_timeout_expiries == 0)
> > > +                             list_add(&rgn->list_expired_rgn, &expired_list);
> > > +                     else
> > > +                             rgn->read_timeout = ktime_add_ms(ktime_get(),
> > > +                                                      READ_TO_MS);
> > > +             }
> > > +     }
> > > +
> > > +     spin_unlock_irqrestore(&hpb->rgn_state_lock, flags);
> > > +
> > > +     list_for_each_entry(rgn, &expired_list, list_expired_rgn) {
> >
> > Here can be problematic - since you don't have the native expired_list
> > initialized
> > before use, if above loop did not insert anything to expired_list, it
> > shall become
> > a dead loop here.
> Not sure what you meant by native initialization.
> LIST_HEAD is statically initializing an empty list, resulting the same
> outcome as INIT_LIST_HEAD.

Sorry for making you confused, you should use list_for_each_entry_safe()
instead of list_for_each_entry() as you are deleting entries within the 
loop,
otherwise, this can become an infinite loop. Again, have you tested this 
patch
before upload? I am sure this is problematic - when it becomes an 
inifinite
loop, below path will hang...

ufshcd_suspend()->ufshpb_suspend()->cancel_jobs()->cancel_delayed_work()

> > And, which lock is protecting rgn->list_expired_rgn? If two
> > read_to_handler works
> > are running in parallel, one can be inserting it to its expired_list
> > while another
> > can be deleting it.
> The timeout handler, being a delayed work, is meant to run every 
> polling period.
> Originally, I had it protected from 2 handlers running concurrently,
> But I removed it following Daejun's comment, which I accepted,
> Since it is always scheduled using the same polling period.

But one can set the delay to 0 through sysfs, right?

Thanks,
Can Guo.

> Thanks,
> Avri
>
> > Can Guo.
> >
> > > +             list_del_init(&rgn->list_expired_rgn);
> > > +             spin_lock_irqsave(&hpb->rsp_list_lock, flags);
> > > +             ufshpb_update_inactive_info(hpb, rgn->rgn_idx);
> > > +             hpb->stats.rb_inactive_cnt++;
> > > +             spin_unlock_irqrestore(&hpb->rsp_list_lock, flags);
> > > +     }
> > > +
> > > +     ufshpb_kick_map_work(hpb);
> > > +
> > > +     schedule_delayed_work(&hpb->ufshpb_read_to_work,
> > > +                           msecs_to_jiffies(POLLING_INTERVAL_MS));
> > > +}
> > > +
> > >  static void ufshpb_add_lru_info(struct victim_select_info *lru_info,
> > >                               struct ufshpb_region *rgn)
> > >  {
> > >       rgn->rgn_state = HPB_RGN_ACTIVE;
> > >       list_add_tail(&rgn->list_lru_rgn, &lru_info->lh_lru_rgn);
> > >       atomic_inc(&lru_info->active_cnt);
> > > +     if (rgn->hpb->is_hcm) {
> > > +             rgn->read_timeout = ktime_add_ms(ktime_get(), READ_TO_MS);
> > > +             rgn->read_timeout_expiries = READ_TO_EXPIRIES;
> > > +     }
> > >  }
> > >
> > >  static void ufshpb_hit_lru_info(struct victim_select_info *lru_info,
> > > @@ -1813,6 +1865,7 @@ static int ufshpb_alloc_region_tbl(struct
> > > ufs_hba *hba, struct ufshpb_lu *hpb)
> > >
> > >               INIT_LIST_HEAD(&rgn->list_inact_rgn);
> > >               INIT_LIST_HEAD(&rgn->list_lru_rgn);
> > > +             INIT_LIST_HEAD(&rgn->list_expired_rgn);
> > >
> > >               if (rgn_idx == hpb->rgns_per_lu - 1) {
> > >                       srgn_cnt = ((hpb->srgns_per_lu - 1) %
> > > @@ -1834,6 +1887,7 @@ static int ufshpb_alloc_region_tbl(struct
> > > ufs_hba *hba, struct ufshpb_lu *hpb)
> > >               }
> > >
> > >               rgn->rgn_flags = 0;
> > > +             rgn->hpb = hpb;
> > >       }
> > >
> > >       return 0;
> > > @@ -2053,6 +2107,8 @@ static int ufshpb_lu_hpb_init(struct ufs_hba
> > > *hba, struct ufshpb_lu *hpb)
> > >                         ufshpb_normalization_work_handler);
> > >               INIT_WORK(&hpb->ufshpb_lun_reset_work,
> > >                         ufshpb_reset_work_handler);
> > > +             INIT_DELAYED_WORK(&hpb->ufshpb_read_to_work,
> > > +                               ufshpb_read_to_handler);
> > >       }
> > >
> > >       hpb->map_req_cache = kmem_cache_create("ufshpb_req_cache",
> > > @@ -2087,6 +2143,10 @@ static int ufshpb_lu_hpb_init(struct ufs_hba
> > > *hba, struct ufshpb_lu *hpb)
> > >       ufshpb_stat_init(hpb);
> > >       ufshpb_param_init(hpb);
> > >
> > > +     if (hpb->is_hcm)
> > > +             schedule_delayed_work(&hpb->ufshpb_read_to_work,
> > > +                                   msecs_to_jiffies(POLLING_INTERVAL_MS));
> > > +
> > >       return 0;
> > >
> > >  release_pre_req_mempool:
> > > @@ -2154,6 +2214,7 @@ static void ufshpb_discard_rsp_lists(struct
> > > ufshpb_lu *hpb)
> > >  static void ufshpb_cancel_jobs(struct ufshpb_lu *hpb)
> > >  {
> > >       if (hpb->is_hcm) {
> > > +             cancel_delayed_work_sync(&hpb->ufshpb_read_to_work);
> > >               cancel_work_sync(&hpb->ufshpb_lun_reset_work);
> > >               cancel_work_sync(&hpb->ufshpb_normalization_work);
> > >       }
> > > @@ -2264,6 +2325,10 @@ void ufshpb_resume(struct ufs_hba *hba)
> > >                       continue;
> > >               ufshpb_set_state(hpb, HPB_PRESENT);
> > >               ufshpb_kick_map_work(hpb);
> > > +             if (hpb->is_hcm)
> > > +                     schedule_delayed_work(&hpb->ufshpb_read_to_work,
> > > +                             msecs_to_jiffies(POLLING_INTERVAL_MS));
> > > +
> > >       }
> > >  }
> > >
> > > diff --git a/drivers/scsi/ufs/ufshpb.h b/drivers/scsi/ufs/ufshpb.h
> > > index 37c1b0ea0c0a..b49e9a34267f 100644
> > > --- a/drivers/scsi/ufs/ufshpb.h
> > > +++ b/drivers/scsi/ufs/ufshpb.h
> > > @@ -109,6 +109,7 @@ struct ufshpb_subregion {
> > >  };
> > >
> > >  struct ufshpb_region {
> > > +     struct ufshpb_lu *hpb;
> > >       struct ufshpb_subregion *srgn_tbl;
> > >       enum HPB_RGN_STATE rgn_state;
> > >       int rgn_idx;
> > > @@ -126,6 +127,10 @@ struct ufshpb_region {
> > >       /* region reads - for host mode */
> > >       spinlock_t rgn_lock;
> > >       unsigned int reads;
> > > +     /* region "cold" timer - for host mode */
> > > +     ktime_t read_timeout;
> > > +     unsigned int read_timeout_expiries;
> > > +     struct list_head list_expired_rgn;
> > >  };
> > >
> > >  #define for_each_sub_region(rgn, i, srgn)                            \
> > > @@ -219,6 +224,7 @@ struct ufshpb_lu {
> > >       struct victim_select_info lru_info;
> > >       struct work_struct ufshpb_normalization_work;
> > >       struct work_struct ufshpb_lun_reset_work;
> > > +     struct delayed_work ufshpb_read_to_work;
> > >
> > >       /* pinned region information */
> > >       u32 lu_pinned_start;