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

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Date:   Tue, 23 Jul 2019 16:57:49 +0530
From:   Sreekanth Reddy <sreekanth.reddy@...adcom.com>
To:     Hannes Reinecke <hare@...e.de>
Cc:     minwoo.im@...sung.com,
        "sathya.prakash@...adcom.com" <sathya.prakash@...adcom.com>,
        "suganath-prabu.subramani@...adcom.com" 
        <suganath-prabu.subramani@...adcom.com>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "MPT-FusionLinux.pdl@...adcom.com" <MPT-FusionLinux.pdl@...adcom.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        Euihyeok Kwon <eh81.kwon@...sung.com>,
        Sarah Cho <sohyeon.jo@...sung.com>,
        Sanggwan Lee <sanggwan.lee@...sung.com>,
        Gyeongmin Nam <gm.nam@...sung.com>,
        Sungjun Park <sj1228.park@...sung.com>,
        "minwoo.im.dev@...il.com" <minwoo.im.dev@...il.com>
Subject: Re: [PATCH V2] mpt3sas: support target smid for [abort|query] task

On Mon, Jul 15, 2019 at 11:43 AM Hannes Reinecke <hare@...e.de> 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@...adcom.com>
> > Cc: Suganath Prabu Subramani <suganath-prabu.subramani@...adcom.com>
> > Cc: Sathya Prakash <sathya.prakash@...adcom.com>
> > Cc: James E.J. Bottomley <jejb@...ux.ibm.com>
> > Cc: Martin K. Petersen <martin.petersen@...cle.com>
> > Cc: MPT-FusionLinux.pdl@...adcom.com
> > Signed-off-by: Minwoo Im <minwoo.im@...sung.com>
> > ---
> >  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@...e.de                                   +49 911 74053 688
> SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
> GF: Felix Imendörffer, Mary Higgins, Sri Rasiah
> HRB 21284 (AG Nürnberg)