From: Jolly Shah <jollys@google.com>

Date: Thu, 18 Mar 2021 15:56:32 -0700

Subject: scsi: libsas: Reset num_scatter if libata marks qc as NODATA

Git-commit: 176ddd89171ddcf661862d90c5d257877f7326d6

Patch-mainline: v5.12-rc8

References: bsc#1187068

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 the following 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"

Update libsas to handle ATA non-data commands separately so num_scatter and

total_xfer_len remain 0.

Link: https://lore.kernel.org/r/20210318225632.2481291-1-jollys@google.com

Fixes: 53de092f47ff ("scsi: libsas: Set data_dir as DMA_NONE if libata marks qc as NODATA")

Tested-by: Luo Jiaxing <luojiaxing@huawei.com>

Reviewed-by: John Garry <john.garry@huawei.com>

Signed-off-by: Jolly Shah <jollys@google.com>

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Acked-by: Lee Duncan <lduncan@suse.com>

---

 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;