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Subject: Re: [PATCH V2] mpt3sas: support target smid for [abort|query] task
To:     minwoo.im@samsung.com,
        "sreekanth.reddy@broadcom.com" <sreekanth.reddy@broadcom.com>,
        "sathya.prakash@broadcom.com" <sathya.prakash@broadcom.com>,
        "suganath-prabu.subramani@broadcom.com" 
        <suganath-prabu.subramani@broadcom.com>,
        "jejb@linux.ibm.com" <jejb@linux.ibm.com>,
        "martin.petersen@oracle.com" <martin.petersen@oracle.com>
Cc:     "MPT-FusionLinux.pdl@broadcom.com" <MPT-FusionLinux.pdl@broadcom.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
        Euihyeok Kwon <eh81.kwon@samsung.com>,
        Sarah Cho <sohyeon.jo@samsung.com>,
        Sanggwan Lee <sanggwan.lee@samsung.com>,
        Gyeongmin Nam <gm.nam@samsung.com>,
        Sungjun Park <sj1228.park@samsung.com>,
        "minwoo.im.dev@gmail.com" <minwoo.im.dev@gmail.com>
References: <CGME20190714034415epcms2p25f9787cb71993a30f58524d2f355b543@epcms2p2>
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From:   Hannes Reinecke <hare@suse.de>
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Message-ID: <860cc8cf-6419-c649-b2d9-19b82f6ebc99@suse.de>
Date:   Mon, 15 Jul 2019 08:13:36 +0200
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Sender: linux-kernel-owner@vger.kernel.org
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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@broadcom.com>
> Cc: Suganath Prabu Subramani <suganath-prabu.subramani@broadcom.com>
> Cc: Sathya Prakash <sathya.prakash@broadcom.com>
> Cc: James E.J. Bottomley <jejb@linux.ibm.com>
> Cc: Martin K. Petersen <martin.petersen@oracle.com>
> Cc: MPT-FusionLinux.pdl@broadcom.com
> Signed-off-by: Minwoo Im <minwoo.im@samsung.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.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare@suse.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
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