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From:   Avri Altman <Avri.Altman@wdc.com>
To:     Can Guo <cang@codeaurora.org>,
        "daejun7.park@samsung.com" <daejun7.park@samsung.com>
CC:     "James E . J . Bottomley" <jejb@linux.vnet.ibm.com>,
        "Martin K . Petersen" <martin.petersen@oracle.com>,
        "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        Bart Van Assche <bvanassche@acm.org>,
        yongmyung lee <ymhungry.lee@samsung.com>,
        ALIM AKHTAR <alim.akhtar@samsung.com>,
        "asutoshd@codeaurora.org" <asutoshd@codeaurora.org>,
        Zang Leigang <zangleigang@hisilicon.com>,
        Avi Shchislowski <Avi.Shchislowski@wdc.com>,
        Bean Huo <beanhuo@micron.com>,
        "stanley.chu@mediatek.com" <stanley.chu@mediatek.com>
Subject: RE: [PATCH v5 05/10] scsi: ufshpb: Region inactivation in host mode
Thread-Topic: [PATCH v5 05/10] scsi: ufshpb: Region inactivation in host mode
Thread-Index: AQHXGufzsAcNB2kctkO70hG9mtiIo6qH0HMg
Date:   Wed, 17 Mar 2021 07:59:42 +0000
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> 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 =3D 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.
>=20
> 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.
>=20
> lock(rgn_state_lock)
>    ufshpb_issue_umap_single_req()
>      ufshpb_prep()
>         lock(rgn_state_lock)   <---------- recursive spin_lock
Will fix.   Will wait for Daejun's v30 to see if anything applies to unmap_=
single.

Thanks,
Avri=20

>=20
> 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.
>=20
>           if (!ufshpb_is_write_or_discard_cmd(cmd) &&
>               !ufshpb_is_read_cmd(cmd))
>                   return 0;
>=20
> Thanks,
> Can Guo.
>=20
> >
> > Thanks,
> > Daejun
> >
> >
> >> Thanks,
> >> Avri
> >>
> >>>
> >>> Can Guo.
> >>>
> >>> > Thanks.
> >>> > Can Guo.
> >>> >
> >>> >> +            return;
> >>> >> +
> >>> >>      lru_info =3D &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[] =3D {
> >>> >>      &dev_attr_hit_cnt.attr,
> >>> >> @@ -1863,6 +1875,7 @@ static struct attribute *hpb_dev_stat_attrs[=
]
> =3D
> >>> >> {
> >>> >>      &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_l=
u
> >>> >> *hpb)
> >>> >>      hpb->stats.rb_active_cnt =3D 0;
> >>> >>      hpb->stats.rb_inactive_cnt =3D 0;
> >>> >>      hpb->stats.map_req_cnt =3D 0;
> >>> >> +    hpb->stats.umap_req_cnt =3D 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 {
> >>
> >>
> >>