Re: [PATCH V2] mpt3sas: support target smid for [abort|query] task

[Sreekanth Reddy]

On Mon, Jul 15, 2019 at 11:43 AM Hannes Reinecke <hare@xxxxxxx> wrote:
>
> On 7/14/19 5:44 AM, Minwoo Im wrote:
> > We can request task management IOCTL command(MPI2_FUNCTION_SCSI_TASK_MGMT)
> > to /dev/mpt3ctl.  If the given task_type is either abort task or query
> > task, it may need a field named "Initiator Port Transfer Tag to Manage"
> > in the IU.
> >
> > Current code does not support to check target IPTT tag from the
> > tm_request.  This patch introduces to check TaskMID given from the
> > userspace as a target tag.  We have a rule of relationship between
> > (struct request *req->tag) and smid in mpt3sas_base.c:
> >
> > 3318 u16
> > 3319 mpt3sas_base_get_smid_scsiio(struct MPT3SAS_ADAPTER *ioc, u8 cb_idx,
> > 3320         struct scsi_cmnd *scmd)
> > 3321 {
> > 3322         struct scsiio_tracker *request = scsi_cmd_priv(scmd);
> > 3323         unsigned int tag = scmd->request->tag;
> > 3324         u16 smid;
> > 3325
> > 3326         smid = tag + 1;
> >
> > So if we want to abort a request tagged #X, then we can pass (X + 1) to
> > this IOCTL handler.  Otherwise, user space just can pass 0 TaskMID to
> > abort the first outstanding smid which is legacy behaviour.
> >
> > Cc: Sreekanth Reddy <sreekanth.reddy@xxxxxxxxxxxx>
> > Cc: Suganath Prabu Subramani <suganath-prabu.subramani@xxxxxxxxxxxx>
> > Cc: Sathya Prakash <sathya.prakash@xxxxxxxxxxxx>
> > Cc: James E.J. Bottomley <jejb@xxxxxxxxxxxxx>
> > Cc: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
> > Cc: MPT-FusionLinux.pdl@xxxxxxxxxxxx
> > Signed-off-by: Minwoo Im <minwoo.im@xxxxxxxxxxx>
> > ---
> >  drivers/scsi/mpt3sas/mpt3sas_ctl.c | 12 ++++++++++--
> >  1 file changed, 10 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/scsi/mpt3sas/mpt3sas_ctl.c b/drivers/scsi/mpt3sas/mpt3sas_ctl.c
> > index b2bb47c14d35..f6b8fd90610a 100644
> > --- a/drivers/scsi/mpt3sas/mpt3sas_ctl.c
> > +++ b/drivers/scsi/mpt3sas/mpt3sas_ctl.c
> > @@ -596,8 +596,16 @@ _ctl_set_task_mid(struct MPT3SAS_ADAPTER *ioc, struct mpt3_ioctl_command *karg,
> >               if (priv_data->sas_target->handle != handle)
> >                       continue;
> >               st = scsi_cmd_priv(scmd);
> > -             tm_request->TaskMID = cpu_to_le16(st->smid);
> > -             found = 1;
> > +
> > +             /*
> > +              * If the given TaskMID from the user space is zero, then the
> > +              * first outstanding smid will be picked up.  Otherwise,
> > +              * targeted smid will be the one.
> > +              */
> > +             if (!tm_request->TaskMID || tm_request->TaskMID == st->smid) {
> > +                     tm_request->TaskMID = cpu_to_le16(st->smid);
> > +                     found = 1;
> > +             }
> >       }
> >
> >       if (!found) {
> >
> I think this is fundamentally wrong.
> ABORT_TASK is used to abort a single task, which of course has to be
> known beforehand. If you don't know the task, what exactly do you hope
> to achieve here? Aborting random I/O?
> Or, even worse, aborting I/O the driver uses internally and corrupt the
> internal workflow of the driver?
>
> We should simply disallow any ABORT TASK from userspace if the TaskMID
> is zero. And I would even argue to disabllow ABORT TASK from userspace
> completely, as the smid is never relayed to userland, and as such the
> user cannot know which task should be aborted.

Hannes,

This interface was added long time back in mpt2sas driver and I don't
have exact reason of adding this interface at that time.
But I know that this interface is still used by BRCM test team & few
customers only for some functionality and regression testing.

Thanks,
Sreekanth

>
> Cheers,
>
> Hannes
> --
> Dr. Hannes Reinecke                Teamlead Storage & Networking
> hare@xxxxxxx                                   +49 911 74053 688
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