Date:   Wed, 17 Mar 2021 12:41:18 +0800
From:   Can Guo <cang@...eaurora.org>
To:     daejun7.park@...sung.com
Cc:     Avri Altman <Avri.Altman@....com>,
        "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        gregkh@...uxfoundation.org, Bart Van Assche <bvanassche@....org>,
        yongmyung lee <ymhungry.lee@...sung.com>,
        ALIM AKHTAR <alim.akhtar@...sung.com>, asutoshd@...eaurora.org,
        Zang Leigang <zangleigang@...ilicon.com>,
        Avi Shchislowski <Avi.Shchislowski@....com>,
        Bean Huo <beanhuo@...ron.com>, stanley.chu@...iatek.com
Subject: Re: [PATCH v5 05/10] scsi: ufshpb: Region inactivation in host mode

On 2021-03-17 10:28, Daejun Park wrote:
>>> >> ---
>>> >>  drivers/scsi/ufs/ufshpb.c | 14 ++++++++++++++
>>> >>  drivers/scsi/ufs/ufshpb.h |  1 +
>>> >>  2 files changed, 15 insertions(+)
>>> >>
>>> >> diff --git a/drivers/scsi/ufs/ufshpb.c b/drivers/scsi/ufs/ufshpb.c
>>> >> index 6f4fd22eaf2f..0744feb4d484 100644
>>> >> --- a/drivers/scsi/ufs/ufshpb.c
>>> >> +++ b/drivers/scsi/ufs/ufshpb.c
>>> >> @@ -907,6 +907,7 @@ static int ufshpb_execute_umap_req(struct
>>> >> ufshpb_lu *hpb,
>>> >>
>>> >>      blk_execute_rq_nowait(q, NULL, req, 1, ufshpb_umap_req_compl_fn);
>>> >>
>>> >> +    hpb->stats.umap_req_cnt++;
>>> >>      return 0;
>>> >>  }
>>> >>
>>> >> @@ -1103,6 +1104,12 @@ static int ufshpb_issue_umap_req(struct
>>> >> ufshpb_lu *hpb,
>>> >>      return -EAGAIN;
>>> >>  }
>>> >>
>>> >> +static int ufshpb_issue_umap_single_req(struct ufshpb_lu *hpb,
>>> >> +                                    struct ufshpb_region *rgn)
>>> >> +{
>>> >> +    return ufshpb_issue_umap_req(hpb, rgn);
>>> >> +}
>>> >> +
>>> >>  static int ufshpb_issue_umap_all_req(struct ufshpb_lu *hpb)
>>> >>  {
>>> >>      return ufshpb_issue_umap_req(hpb, NULL);
>>> >> @@ -1115,6 +1122,10 @@ static void __ufshpb_evict_region(struct
>>> >> ufshpb_lu *hpb,
>>> >>      struct ufshpb_subregion *srgn;
>>> >>      int srgn_idx;
>>> >>
>>> >> +
>>> >> +    if (hpb->is_hcm && ufshpb_issue_umap_single_req(hpb, rgn))
>>> >
>>> > __ufshpb_evict_region() is called with rgn_state_lock held and IRQ
>>> > disabled,
>>> > when ufshpb_issue_umap_single_req() invokes blk_execute_rq_nowait(),
>>> > below
>>> > warning shall pop up every time, fix it?
>>> >
>>> > void blk_execute_rq_nowait(struct request_queue *q, struct gendisk
>>> > *bd_disk,
>>> >                  struct request *rq, int at_head,
>>> >                          rq_end_io_fn *done)
>>> > {
>>> >       WARN_ON(irqs_disabled());
>>> > ...
>>> >
>>> 
>>> Moreover, since we are here with rgn_state_lock held and IRQ 
>>> disabled,
>>> in ufshpb_get_req(), rq = kmem_cache_alloc(hpb->map_req_cache,
>>> GFP_KERNEL)
>>> has the GFP_KERNEL flag, scheduling while atomic???
>> I think your comment applies to  ufshpb_issue_umap_all_req as well,
>> Which is called from slave_configure/scsi_add_lun.
>> 
>> Since the host-mode series is utilizing the framework laid by the 
>> device-mode,
>> Maybe you can add this comment to  Daejun's last version?
> 
> Hi Avri, Can Guo
> 
> I think ufshpb_issue_umap_single_req() can be moved to end of
> ufshpb_evict_region().
> Then we can avoid rgn_state_lock when it sends unmap command.

I am not the expert here, please you two fix it. I am just reporting
what can be wrong. Anyways, ufshpb_issue_umap_single_req() should not
be called with rgn_state_lock held - think about below (another deadly)
scenario.

lock(rgn_state_lock)
   ufshpb_issue_umap_single_req()
     ufshpb_prep()
        lock(rgn_state_lock)   <---------- recursive spin_lock

BTW, @Daejun shouldn't we stop passthrough cmds from stepping
into ufshpb_prep()? In current code, you are trying to use below
check to block cmds other than write/discard/read, but a passthrough
cmd can not be blocked by the check.

          if (!ufshpb_is_write_or_discard_cmd(cmd) &&
              !ufshpb_is_read_cmd(cmd))
                  return 0;

Thanks,
Can Guo.

> 
> Thanks,
> Daejun
> 
> 
>> Thanks,
>> Avri
>> 
>>> 
>>> Can Guo.
>>> 
>>> > Thanks.
>>> > Can Guo.
>>> >
>>> >> +            return;
>>> >> +
>>> >>      lru_info = &hpb->lru_info;
>>> >>
>>> >>      dev_dbg(&hpb->sdev_ufs_lu->sdev_dev, "evict region %d\n",
>>> >> rgn->rgn_idx);
>>> >> @@ -1855,6 +1866,7 @@ ufshpb_sysfs_attr_show_func(rb_noti_cnt);
>>> >>  ufshpb_sysfs_attr_show_func(rb_active_cnt);
>>> >>  ufshpb_sysfs_attr_show_func(rb_inactive_cnt);
>>> >>  ufshpb_sysfs_attr_show_func(map_req_cnt);
>>> >> +ufshpb_sysfs_attr_show_func(umap_req_cnt);
>>> >>
>>> >>  static struct attribute *hpb_dev_stat_attrs[] = {
>>> >>      &dev_attr_hit_cnt.attr,
>>> >> @@ -1863,6 +1875,7 @@ static struct attribute *hpb_dev_stat_attrs[] =
>>> >> {
>>> >>      &dev_attr_rb_active_cnt.attr,
>>> >>      &dev_attr_rb_inactive_cnt.attr,
>>> >>      &dev_attr_map_req_cnt.attr,
>>> >> +    &dev_attr_umap_req_cnt.attr,
>>> >>      NULL,
>>> >>  };
>>> >>
>>> >> @@ -1978,6 +1991,7 @@ static void ufshpb_stat_init(struct ufshpb_lu
>>> >> *hpb)
>>> >>      hpb->stats.rb_active_cnt = 0;
>>> >>      hpb->stats.rb_inactive_cnt = 0;
>>> >>      hpb->stats.map_req_cnt = 0;
>>> >> +    hpb->stats.umap_req_cnt = 0;
>>> >>  }
>>> >>
>>> >>  static void ufshpb_param_init(struct ufshpb_lu *hpb)
>>> >> diff --git a/drivers/scsi/ufs/ufshpb.h b/drivers/scsi/ufs/ufshpb.h
>>> >> index bd4308010466..84598a317897 100644
>>> >> --- a/drivers/scsi/ufs/ufshpb.h
>>> >> +++ b/drivers/scsi/ufs/ufshpb.h
>>> >> @@ -186,6 +186,7 @@ struct ufshpb_stats {
>>> >>      u64 rb_inactive_cnt;
>>> >>      u64 map_req_cnt;
>>> >>      u64 pre_req_cnt;
>>> >> +    u64 umap_req_cnt;
>>> >>  };
>>> >>
>>> >>  struct ufshpb_lu {
>> 
>> 
>> 

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