When the cache_type for the scsi device is changed, the scsi layer
issues a MODE_SELECT command. The caching mode details are communicated
via a request buffer associated with the scsi command with data
direction set as DMA_TO_DEVICE (scsi_mode_select). When this command
reaches the libata layer, as a part of generic initial setup, libata
layer sets up the scatterlist for the command using the scsi command
(ata_scsi_qc_new). This command is then translated by the libata layer
into ATA_CMD_SET_FEATURES (ata_scsi_mode_select_xlat). The libata layer
treats this as a non data command (ata_mselect_caching), since it only
needs an ata taskfile to pass the caching on/off information to the
device. It does not need the scatterlist that has been setup, so it does
not perform dma_map_sg on the scatterlist (ata_qc_issue). Unfortunately,
when this command reaches the libsas layer(sas_ata_qc_issue), libsas
layer sees it as a non data command with a scatterlist. It cannot
extract the correct dma length, since the scatterlist has not been
mapped with dma_map_sg for a DMA operation. When this partially
constructed SAS task reaches pm80xx LLDD, it results in below warning.
"pm80xx_chip_sata_req 6058: The sg list address
start_addr=0x0000000000000000 data_len=0x0end_addr_high=0xffffffff
end_addr_low=0xffffffff has crossed 4G boundary"
This patch updates code to handle ata non data commands separately so
num_scatter and total_xfer_len remain 0.
Fixes: 53de092f47ff ("scsi: libsas: Set data_dir as DMA_NONE if libata marks qc as NODATA")
Signed-off-by: Jolly Shah <[email protected]>
---
v2:
- reorganized code to avoid setting num_scatter twice
drivers/scsi/libsas/sas_ata.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/drivers/scsi/libsas/sas_ata.c b/drivers/scsi/libsas/sas_ata.c
index 024e5a550759..8b9a39077dba 100644
--- a/drivers/scsi/libsas/sas_ata.c
+++ b/drivers/scsi/libsas/sas_ata.c
@@ -201,18 +201,17 @@ static unsigned int sas_ata_qc_issue(struct ata_queued_cmd *qc)
memcpy(task->ata_task.atapi_packet, qc->cdb, qc->dev->cdb_len);
task->total_xfer_len = qc->nbytes;
task->num_scatter = qc->n_elem;
+ task->data_dir = qc->dma_dir;
+ } else if (qc->tf.protocol == ATA_PROT_NODATA) {
+ task->data_dir = DMA_NONE;
} else {
for_each_sg(qc->sg, sg, qc->n_elem, si)
xfer += sg_dma_len(sg);
task->total_xfer_len = xfer;
task->num_scatter = si;
- }
-
- 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;
--
2.31.0.rc2.261.g7f71774620-goog
在 2021/3/19 6:56, Jolly Shah 写道:
> When the cache_type for the scsi device is changed, the scsi layer
> issues a MODE_SELECT command. The caching mode details are communicated
> via a request buffer associated with the scsi command with data
> direction set as DMA_TO_DEVICE (scsi_mode_select). When this command
> reaches the libata layer, as a part of generic initial setup, libata
> layer sets up the scatterlist for the command using the scsi command
> (ata_scsi_qc_new). This command is then translated by the libata layer
> into ATA_CMD_SET_FEATURES (ata_scsi_mode_select_xlat). The libata layer
> treats this as a non data command (ata_mselect_caching), since it only
> needs an ata taskfile to pass the caching on/off information to the
> device. It does not need the scatterlist that has been setup, so it does
> not perform dma_map_sg on the scatterlist (ata_qc_issue). Unfortunately,
> when this command reaches the libsas layer(sas_ata_qc_issue), libsas
> layer sees it as a non data command with a scatterlist. It cannot
> extract the correct dma length, since the scatterlist has not been
> mapped with dma_map_sg for a DMA operation. When this partially
> constructed SAS task reaches pm80xx LLDD, it results in below warning.
>
> "pm80xx_chip_sata_req 6058: The sg list address
> start_addr=0x0000000000000000 data_len=0x0end_addr_high=0xffffffff
> end_addr_low=0xffffffff has crossed 4G boundary"
>
> This patch updates code to handle ata non data commands separately so
> num_scatter and total_xfer_len remain 0.
>
> Fixes: 53de092f47ff ("scsi: libsas: Set data_dir as DMA_NONE if libata marks qc as NODATA")
> Signed-off-by: Jolly Shah <[email protected]>
> ---
> v2:
> - reorganized code to avoid setting num_scatter twice
>
> drivers/scsi/libsas/sas_ata.c | 9 ++++-----
> 1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/scsi/libsas/sas_ata.c b/drivers/scsi/libsas/sas_ata.c
> index 024e5a550759..8b9a39077dba 100644
> --- a/drivers/scsi/libsas/sas_ata.c
> +++ b/drivers/scsi/libsas/sas_ata.c
> @@ -201,18 +201,17 @@ static unsigned int sas_ata_qc_issue(struct ata_queued_cmd *qc)
> memcpy(task->ata_task.atapi_packet, qc->cdb, qc->dev->cdb_len);
> task->total_xfer_len = qc->nbytes;
> task->num_scatter = qc->n_elem;
> + task->data_dir = qc->dma_dir;
> + } else if (qc->tf.protocol == ATA_PROT_NODATA) {
> + task->data_dir = DMA_NONE;
Hi Jolly & John,
We only set DMA_NONE for ATA_PROT_NODATA, I'm curious about why
ATA_PROT_NCQ_NODATA and ATAPI_PROT_NODATA do not need to set DMA_NONE?
Thanks,
Jason
> } else {
> for_each_sg(qc->sg, sg, qc->n_elem, si)
> xfer += sg_dma_len(sg);
>
> task->total_xfer_len = xfer;
> task->num_scatter = si;
> - }
> -
> - 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;
>
On 19/03/2021 01:43, Jason Yan wrote:
>
>
> 在 2021/3/19 6:56, Jolly Shah 写道:
>> When the cache_type for the scsi device is changed, the scsi layer
>> issues a MODE_SELECT command. The caching mode details are communicated
>> via a request buffer associated with the scsi command with data
>> direction set as DMA_TO_DEVICE (scsi_mode_select). When this command
>> reaches the libata layer, as a part of generic initial setup, libata
>> layer sets up the scatterlist for the command using the scsi command
>> (ata_scsi_qc_new). This command is then translated by the libata layer
>> into ATA_CMD_SET_FEATURES (ata_scsi_mode_select_xlat). The libata layer
>> treats this as a non data command (ata_mselect_caching), since it only
>> needs an ata taskfile to pass the caching on/off information to the
>> device. It does not need the scatterlist that has been setup, so it does
>> not perform dma_map_sg on the scatterlist (ata_qc_issue). Unfortunately,
>> when this command reaches the libsas layer(sas_ata_qc_issue), libsas
>> layer sees it as a non data command with a scatterlist. It cannot
>> extract the correct dma length, since the scatterlist has not been
>> mapped with dma_map_sg for a DMA operation. When this partially
>> constructed SAS task reaches pm80xx LLDD, it results in below warning.
>>
>> "pm80xx_chip_sata_req 6058: The sg list address
>> start_addr=0x0000000000000000 data_len=0x0end_addr_high=0xffffffff
>> end_addr_low=0xffffffff has crossed 4G boundary"
>>
>> This patch updates code to handle ata non data commands separately so
>> num_scatter and total_xfer_len remain 0.
>>
>> Fixes: 53de092f47ff ("scsi: libsas: Set data_dir as DMA_NONE if libata
>> marks qc as NODATA")
>> Signed-off-by: Jolly Shah <[email protected]>
Reviewed-by: John Garry <[email protected]>
@luojiaxing, can you please test this?
>> ---
>> v2:
>> - reorganized code to avoid setting num_scatter twice
>>
>> drivers/scsi/libsas/sas_ata.c | 9 ++++-----
>> 1 file changed, 4 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/scsi/libsas/sas_ata.c
>> b/drivers/scsi/libsas/sas_ata.c
>> index 024e5a550759..8b9a39077dba 100644
>> --- a/drivers/scsi/libsas/sas_ata.c
>> +++ b/drivers/scsi/libsas/sas_ata.c
>> @@ -201,18 +201,17 @@ static unsigned int sas_ata_qc_issue(struct
>> ata_queued_cmd *qc)
>> memcpy(task->ata_task.atapi_packet, qc->cdb, qc->dev->cdb_len);
>> task->total_xfer_len = qc->nbytes;
>> task->num_scatter = qc->n_elem;
>> + task->data_dir = qc->dma_dir;
>> + } else if (qc->tf.protocol == ATA_PROT_NODATA) {
>> + task->data_dir = DMA_NONE;
>
> Hi Jolly & John,
>
> We only set DMA_NONE for ATA_PROT_NODATA, I'm curious about why
> ATA_PROT_NCQ_NODATA and ATAPI_PROT_NODATA do not need to set DMA_NONE?
So we can see something like atapi_eh_tur() -> ata_exec_internal(),
which is a ATAPI NONDATA and has DMA_NONE, so should be ok.
Other cases, like those using the xlate function on the qc for
ATA_PROT_NCQ_NODATA, could be checked further.
For now, we're just trying to fix the fix.
>
> Thanks,
> Jason
>
>
>> } else {
>> for_each_sg(qc->sg, sg, qc->n_elem, si)
>> xfer += sg_dma_len(sg);
>> task->total_xfer_len = xfer;
>> task->num_scatter = si;
>> - }
>> -
>> - 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;
>>
> .
On 2021/3/20 20:14, John Garry wrote:
> On 19/03/2021 01:43, Jason Yan wrote:
>>
>>
>> 在 2021/3/19 6:56, Jolly Shah 写道:
>>> When the cache_type for the scsi device is changed, the scsi layer
>>> issues a MODE_SELECT command. The caching mode details are communicated
>>> via a request buffer associated with the scsi command with data
>>> direction set as DMA_TO_DEVICE (scsi_mode_select). When this command
>>> reaches the libata layer, as a part of generic initial setup, libata
>>> layer sets up the scatterlist for the command using the scsi command
>>> (ata_scsi_qc_new). This command is then translated by the libata layer
>>> into ATA_CMD_SET_FEATURES (ata_scsi_mode_select_xlat). The libata layer
>>> treats this as a non data command (ata_mselect_caching), since it only
>>> needs an ata taskfile to pass the caching on/off information to the
>>> device. It does not need the scatterlist that has been setup, so it
>>> does
>>> not perform dma_map_sg on the scatterlist (ata_qc_issue).
>>> Unfortunately,
>>> when this command reaches the libsas layer(sas_ata_qc_issue), libsas
>>> layer sees it as a non data command with a scatterlist. It cannot
>>> extract the correct dma length, since the scatterlist has not been
>>> mapped with dma_map_sg for a DMA operation. When this partially
>>> constructed SAS task reaches pm80xx LLDD, it results in below warning.
>>>
>>> "pm80xx_chip_sata_req 6058: The sg list address
>>> start_addr=0x0000000000000000 data_len=0x0end_addr_high=0xffffffff
>>> end_addr_low=0xffffffff has crossed 4G boundary"
>>>
>>> This patch updates code to handle ata non data commands separately so
>>> num_scatter and total_xfer_len remain 0.
>>>
>>> Fixes: 53de092f47ff ("scsi: libsas: Set data_dir as DMA_NONE if
>>> libata marks qc as NODATA")
>>> Signed-off-by: Jolly Shah <[email protected]>
>
> Reviewed-by: John Garry <[email protected]>
>
> @luojiaxing, can you please test this?
Sure, let me take a look, and reply the test result here later
Thanks
Jiaxing
>
>>> ---
>>> v2:
>>> - reorganized code to avoid setting num_scatter twice
>>>
>>> drivers/scsi/libsas/sas_ata.c | 9 ++++-----
>>> 1 file changed, 4 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/scsi/libsas/sas_ata.c
>>> b/drivers/scsi/libsas/sas_ata.c
>>> index 024e5a550759..8b9a39077dba 100644
>>> --- a/drivers/scsi/libsas/sas_ata.c
>>> +++ b/drivers/scsi/libsas/sas_ata.c
>>> @@ -201,18 +201,17 @@ static unsigned int sas_ata_qc_issue(struct
>>> ata_queued_cmd *qc)
>>> memcpy(task->ata_task.atapi_packet, qc->cdb,
>>> qc->dev->cdb_len);
>>> task->total_xfer_len = qc->nbytes;
>>> task->num_scatter = qc->n_elem;
>>> + task->data_dir = qc->dma_dir;
>>> + } else if (qc->tf.protocol == ATA_PROT_NODATA) {
>>> + task->data_dir = DMA_NONE;
>>
>> Hi Jolly & John,
>>
>> We only set DMA_NONE for ATA_PROT_NODATA, I'm curious about why
>> ATA_PROT_NCQ_NODATA and ATAPI_PROT_NODATA do not need to set DMA_NONE?
>
> So we can see something like atapi_eh_tur() -> ata_exec_internal(),
> which is a ATAPI NONDATA and has DMA_NONE, so should be ok.
>
> Other cases, like those using the xlate function on the qc for
> ATA_PROT_NCQ_NODATA, could be checked further.
>
> For now, we're just trying to fix the fix.
>
>>
>> Thanks,
>> Jason
>>
>>
>>> } else {
>>> for_each_sg(qc->sg, sg, qc->n_elem, si)
>>> xfer += sg_dma_len(sg);
>>> task->total_xfer_len = xfer;
>>> task->num_scatter = si;
>>> - }
>>> -
>>> - 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;
>>>
>> .
>
>
> .
>
Hi Luojiaxing,
On Mon, Mar 22, 2021 at 1:41 AM luojiaxing <[email protected]> wrote:
>
>
> On 2021/3/20 20:14, John Garry wrote:
> > On 19/03/2021 01:43, Jason Yan wrote:
> >>
> >>
> >> 在 2021/3/19 6:56, Jolly Shah 写道:
> >>> When the cache_type for the scsi device is changed, the scsi layer
> >>> issues a MODE_SELECT command. The caching mode details are communicated
> >>> via a request buffer associated with the scsi command with data
> >>> direction set as DMA_TO_DEVICE (scsi_mode_select). When this command
> >>> reaches the libata layer, as a part of generic initial setup, libata
> >>> layer sets up the scatterlist for the command using the scsi command
> >>> (ata_scsi_qc_new). This command is then translated by the libata layer
> >>> into ATA_CMD_SET_FEATURES (ata_scsi_mode_select_xlat). The libata layer
> >>> treats this as a non data command (ata_mselect_caching), since it only
> >>> needs an ata taskfile to pass the caching on/off information to the
> >>> device. It does not need the scatterlist that has been setup, so it
> >>> does
> >>> not perform dma_map_sg on the scatterlist (ata_qc_issue).
> >>> Unfortunately,
> >>> when this command reaches the libsas layer(sas_ata_qc_issue), libsas
> >>> layer sees it as a non data command with a scatterlist. It cannot
> >>> extract the correct dma length, since the scatterlist has not been
> >>> mapped with dma_map_sg for a DMA operation. When this partially
> >>> constructed SAS task reaches pm80xx LLDD, it results in below warning.
> >>>
> >>> "pm80xx_chip_sata_req 6058: The sg list address
> >>> start_addr=0x0000000000000000 data_len=0x0end_addr_high=0xffffffff
> >>> end_addr_low=0xffffffff has crossed 4G boundary"
> >>>
> >>> This patch updates code to handle ata non data commands separately so
> >>> num_scatter and total_xfer_len remain 0.
> >>>
> >>> Fixes: 53de092f47ff ("scsi: libsas: Set data_dir as DMA_NONE if
> >>> libata marks qc as NODATA")
> >>> Signed-off-by: Jolly Shah <[email protected]>
> >
> > Reviewed-by: John Garry <[email protected]>
> >
> > @luojiaxing, can you please test this?
>
>
> Sure, let me take a look, and reply the test result here later
>
Wanted to follow up on test results. Any updates?
Thanks,
Jolly
>
> Thanks
>
> Jiaxing
>
>
> >
> >>> ---
> >>> v2:
> >>> - reorganized code to avoid setting num_scatter twice
> >>>
> >>> drivers/scsi/libsas/sas_ata.c | 9 ++++-----
> >>> 1 file changed, 4 insertions(+), 5 deletions(-)
> >>>
> >>> diff --git a/drivers/scsi/libsas/sas_ata.c
> >>> b/drivers/scsi/libsas/sas_ata.c
> >>> index 024e5a550759..8b9a39077dba 100644
> >>> --- a/drivers/scsi/libsas/sas_ata.c
> >>> +++ b/drivers/scsi/libsas/sas_ata.c
> >>> @@ -201,18 +201,17 @@ static unsigned int sas_ata_qc_issue(struct
> >>> ata_queued_cmd *qc)
> >>> memcpy(task->ata_task.atapi_packet, qc->cdb,
> >>> qc->dev->cdb_len);
> >>> task->total_xfer_len = qc->nbytes;
> >>> task->num_scatter = qc->n_elem;
> >>> + task->data_dir = qc->dma_dir;
> >>> + } else if (qc->tf.protocol == ATA_PROT_NODATA) {
> >>> + task->data_dir = DMA_NONE;
> >>
> >> Hi Jolly & John,
> >>
> >> We only set DMA_NONE for ATA_PROT_NODATA, I'm curious about why
> >> ATA_PROT_NCQ_NODATA and ATAPI_PROT_NODATA do not need to set DMA_NONE?
> >
> > So we can see something like atapi_eh_tur() -> ata_exec_internal(),
> > which is a ATAPI NONDATA and has DMA_NONE, so should be ok.
> >
> > Other cases, like those using the xlate function on the qc for
> > ATA_PROT_NCQ_NODATA, could be checked further.
> >
> > For now, we're just trying to fix the fix.
> >
> >>
> >> Thanks,
> >> Jason
> >>
> >>
> >>> } else {
> >>> for_each_sg(qc->sg, sg, qc->n_elem, si)
> >>> xfer += sg_dma_len(sg);
> >>> task->total_xfer_len = xfer;
> >>> task->num_scatter = si;
> >>> - }
> >>> -
> >>> - 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;
> >>>
> >> .
> >
> >
> > .
> >
>
On 2021/4/2 6:34, Jolly Shah wrote:
> Hi Luojiaxing,
>
>
> On Mon, Mar 22, 2021 at 1:41 AM luojiaxing <[email protected]> wrote:
>>
>> On 2021/3/20 20:14, John Garry wrote:
>>> On 19/03/2021 01:43, Jason Yan wrote:
>>>>
>>>> 在 2021/3/19 6:56, Jolly Shah 写道:
>>>>> When the cache_type for the scsi device is changed, the scsi layer
>>>>> issues a MODE_SELECT command. The caching mode details are communicated
>>>>> via a request buffer associated with the scsi command with data
>>>>> direction set as DMA_TO_DEVICE (scsi_mode_select). When this command
>>>>> reaches the libata layer, as a part of generic initial setup, libata
>>>>> layer sets up the scatterlist for the command using the scsi command
>>>>> (ata_scsi_qc_new). This command is then translated by the libata layer
>>>>> into ATA_CMD_SET_FEATURES (ata_scsi_mode_select_xlat). The libata layer
>>>>> treats this as a non data command (ata_mselect_caching), since it only
>>>>> needs an ata taskfile to pass the caching on/off information to the
>>>>> device. It does not need the scatterlist that has been setup, so it
>>>>> does
>>>>> not perform dma_map_sg on the scatterlist (ata_qc_issue).
>>>>> Unfortunately,
>>>>> when this command reaches the libsas layer(sas_ata_qc_issue), libsas
>>>>> layer sees it as a non data command with a scatterlist. It cannot
>>>>> extract the correct dma length, since the scatterlist has not been
>>>>> mapped with dma_map_sg for a DMA operation. When this partially
>>>>> constructed SAS task reaches pm80xx LLDD, it results in below warning.
>>>>>
>>>>> "pm80xx_chip_sata_req 6058: The sg list address
>>>>> start_addr=0x0000000000000000 data_len=0x0end_addr_high=0xffffffff
>>>>> end_addr_low=0xffffffff has crossed 4G boundary"
>>>>>
>>>>> This patch updates code to handle ata non data commands separately so
>>>>> num_scatter and total_xfer_len remain 0.
>>>>>
>>>>> Fixes: 53de092f47ff ("scsi: libsas: Set data_dir as DMA_NONE if
>>>>> libata marks qc as NODATA")
>>>>> Signed-off-by: Jolly Shah <[email protected]>
>>> Reviewed-by: John Garry <[email protected]>
>>>
>>> @luojiaxing, can you please test this?
>>
>> Sure, let me take a look, and reply the test result here later
>>
> Wanted to follow up on test results. Any updates?
Sorry for reply to you so late.
I use sdparm to change cache type of SATA disk, and it's ok with my test.
In addition, some other functional tests result have no problem too, So
I think this patch is ok to me.
Tested-by: Luo Jiaxing <[email protected]>
Thanks
Jiaxing
>
> Thanks,
> Jolly
>
>> Thanks
>>
>> Jiaxing
>>
>>
>>>>> ---
>>>>> v2:
>>>>> - reorganized code to avoid setting num_scatter twice
>>>>>
>>>>> drivers/scsi/libsas/sas_ata.c | 9 ++++-----
>>>>> 1 file changed, 4 insertions(+), 5 deletions(-)
>>>>>
>>>>> diff --git a/drivers/scsi/libsas/sas_ata.c
>>>>> b/drivers/scsi/libsas/sas_ata.c
>>>>> index 024e5a550759..8b9a39077dba 100644
>>>>> --- a/drivers/scsi/libsas/sas_ata.c
>>>>> +++ b/drivers/scsi/libsas/sas_ata.c
>>>>> @@ -201,18 +201,17 @@ static unsigned int sas_ata_qc_issue(struct
>>>>> ata_queued_cmd *qc)
>>>>> memcpy(task->ata_task.atapi_packet, qc->cdb,
>>>>> qc->dev->cdb_len);
>>>>> task->total_xfer_len = qc->nbytes;
>>>>> task->num_scatter = qc->n_elem;
>>>>> + task->data_dir = qc->dma_dir;
>>>>> + } else if (qc->tf.protocol == ATA_PROT_NODATA) {
>>>>> + task->data_dir = DMA_NONE;
>>>> Hi Jolly & John,
>>>>
>>>> We only set DMA_NONE for ATA_PROT_NODATA, I'm curious about why
>>>> ATA_PROT_NCQ_NODATA and ATAPI_PROT_NODATA do not need to set DMA_NONE?
>>> So we can see something like atapi_eh_tur() -> ata_exec_internal(),
>>> which is a ATAPI NONDATA and has DMA_NONE, so should be ok.
>>>
>>> Other cases, like those using the xlate function on the qc for
>>> ATA_PROT_NCQ_NODATA, could be checked further.
>>>
>>> For now, we're just trying to fix the fix.
>>>
>>>> Thanks,
>>>> Jason
>>>>
>>>>
>>>>> } else {
>>>>> for_each_sg(qc->sg, sg, qc->n_elem, si)
>>>>> xfer += sg_dma_len(sg);
>>>>> task->total_xfer_len = xfer;
>>>>> task->num_scatter = si;
>>>>> - }
>>>>> -
>>>>> - 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;
>>>>>
>>>> .
>>>
>>> .
>>>
> .
>
On Thu, 18 Mar 2021 15:56:32 -0700, Jolly Shah wrote:
> When the cache_type for the scsi device is changed, the scsi layer
> issues a MODE_SELECT command. The caching mode details are communicated
> via a request buffer associated with the scsi command with data
> direction set as DMA_TO_DEVICE (scsi_mode_select). When this command
> reaches the libata layer, as a part of generic initial setup, libata
> layer sets up the scatterlist for the command using the scsi command
> (ata_scsi_qc_new). This command is then translated by the libata layer
> into ATA_CMD_SET_FEATURES (ata_scsi_mode_select_xlat). The libata layer
> treats this as a non data command (ata_mselect_caching), since it only
> needs an ata taskfile to pass the caching on/off information to the
> device. It does not need the scatterlist that has been setup, so it does
> not perform dma_map_sg on the scatterlist (ata_qc_issue). Unfortunately,
> when this command reaches the libsas layer(sas_ata_qc_issue), libsas
> layer sees it as a non data command with a scatterlist. It cannot
> extract the correct dma length, since the scatterlist has not been
> mapped with dma_map_sg for a DMA operation. When this partially
> constructed SAS task reaches pm80xx LLDD, it results in below warning.
>
> [...]
Applied to 5.12/scsi-fixes, thanks!
[1/1] scsi: libsas: Reset num_scatter if libata mark qc as NODATA
https://git.kernel.org/mkp/scsi/c/176ddd89171d
--
Martin K. Petersen Oracle Linux Engineering