Messages in this thread | | | Subject | Re: [PATCH v1] scsi: libsas: set data_dir as DMA_NONE if libata mark qc as NODATA | From | Jason Yan <> | Date | Mon, 31 Aug 2020 15:29:49 +0800 |
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在 2020/8/26 15:24, Luo Jiaxing 写道: > We found that it will fail every time when set feature to SATA disk by > "sdparm -s WCE=0 /dev/sde". > > After checking protocol, we know that MODE SELECT is the SCSI command for > setting WCE, and it do not exist in the SATA protocol. Therefore, this > commands are encapsulated in the SET FEATURE command in SATA protocol. > The difference is that the MODE SELECT command sent to SAS disk contains > data and is sent through the DMA. But when send to SATA disk through > SET FEATURE command, it does not contain data. > > I think libsas was not thorough enough in dealing with the situation, at > sas_ata_qc_issue(), task->dma_dir is inherited from qc->dma_dir(qc->dma_dir > is also inherited from SCSI). However, in ATA driver, if qc->tf.protocol is > set to ATA_PROT_NODATA, ata_sg_setup() will not invoked by ata_qc_issue(). > It mean that ATA didn't use dma_dir and it's not reliable. So, if libsas > still inherits from qc->dma_dir when there is no data need to be send. As a > result, task with no data are mistakenly considered as carrying data and it > will make LLDD report an error on IO completion. > > So, When ATA driver mark tf->protocol as NODATA, dma_dir should be set as > DMA_NONE. And we can see WCE is successfully disable for SATA disk then. > > Euler:~ # sdparm -s WCE=0 /dev/sde > /dev/sde: ATA ST4000NM0035-1V4 TN03 > Euler:~ # sdparm /dev/sde > /dev/sde: ATA ST4000NM0035-1V4 TN03 > Read write error recovery mode page: > AWRE 1 [cha: n, def: 1] > ARRE 0 [cha: n, def: 0] > PER 0 [cha: n, def: 0] > Caching (SBC) mode page: > WCE 0 [cha: y, def: 0] > RCD 0 [cha: n, def: 0] > Control mode page: > SWP 0 [cha: n, def: 0] > > Fixes: fa1c1e8f1ece ("[SCSI] Add SATA support to libsas") > > Signed-off-by: Luo Jiaxing <luojiaxing@huawei.com> > Reviewed-by: John Garry <john.garry@huawei.com> > --- > drivers/scsi/libsas/sas_ata.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/scsi/libsas/sas_ata.c b/drivers/scsi/libsas/sas_ata.c > index 6a521ba..a488798 100644 > --- a/drivers/scsi/libsas/sas_ata.c > +++ b/drivers/scsi/libsas/sas_ata.c > @@ -209,7 +209,10 @@ static unsigned int sas_ata_qc_issue(struct ata_queued_cmd *qc) > task->num_scatter = si; > } > > - task->data_dir = qc->dma_dir; > + if (qc->tf.protocol == ATA_PROT_NODATA) > + task->data_dir = DMA_NONE; > + else > + task->data_dir = qc->dma_dir; > task->scatter = qc->sg; > task->ata_task.retry_count = 1; > task->task_state_flags = SAS_TASK_STATE_PENDING; >
Reviewed-by: Jason Yan <yanaijie@huawei.com>
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