linux-kernel - RE: [PATCH 2/2] scsi: ufs: Return a bsg request immediatley if eh-in-progress

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Date:   Mon, 8 Nov 2021 17:24:29 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Bart Van Assche <bvanassche@....org>,
        "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>
CC:     "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Adrian Hunter <adrian.hunter@...el.com>
Subject: RE: [PATCH 2/2] scsi: ufs: Return a bsg request immediatley if
 eh-in-progress

> On 11/8/21 4:08 AM, Avri Altman wrote:
> > ufs-bsg is attempting to access the device from user-space, and it is
> > unaware of the internal driver flows, specifically if error handling is
> > currently ongoing.
> >
> > Fixes: 5e0a86eed846 (scsi: ufs: Add API to execute raw upiu commands)
> >
> > Signed-off-by: Avri Altman <avri.altman@....com>
> > ---
> >   drivers/scsi/ufs/ufshcd.c | 3 +++
> >   1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> > index 3869bb57769b..828061c05909 100644
> > --- a/drivers/scsi/ufs/ufshcd.c
> > +++ b/drivers/scsi/ufs/ufshcd.c
> > @@ -6830,6 +6830,9 @@ int ufshcd_exec_raw_upiu_cmd(struct ufs_hba
> *hba,
> >       enum utp_ocs ocs_value;
> >       u8 tm_f = be32_to_cpu(req_upiu->header.dword_1) >> 16 &
> MASK_TM_FUNC;
> >
> > +     if (!ufshcd_is_user_access_allowed(hba))
> > +             return -EBUSY;
> > +
> >       switch (msgcode) {
> >       case UPIU_TRANSACTION_NOP_OUT:
> >               cmd_type = DEV_CMD_TYPE_NOP;
> 
> Making operations fail if error handling is in progress makes it harder than
> necessary to write user space software that uses the BSG interface. Has it
> been considered to wait inside ufshcd_exec_raw_upiu_cmd() until error
> handling
> has finished?
I am not sure.
I would expect a retry / polling / other, if any, to be done in user-space and not in the kernel.
e.g. a common practice in the code that send SG_IO or other ioctls is to retry on EBUSY.
Not sure that this is the case in ufs-utils though.

Thanks,
Avri

Thanks,
Avri

> 
> Thanks,
> 
> Bart.
>