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Subject[PATCH 3.12 112/142] scsi: libsas: fix ata xfer length
From: John Garry <>

3.12-stable review patch. If anyone has any objections, please let me know.


commit 9702c67c6066f583b629cf037d2056245bb7a8e6 upstream.

The total ata xfer length may not be calculated properly, in that we do
not use the proper method to get an sg element dma length.

According to the code comment, sg_dma_len() should be used after
dma_map_sg() is called.

This issue was found by turning on the SMMUv3 in front of the hisi_sas
controller in hip07. Multiple sg elements were being combined into a
single element, but the original first element length was being use as
the total xfer length.

Fixes: ff2aeb1eb64c8a4770a6 ("libata: convert to chained sg")
Signed-off-by: John Garry <>
Signed-off-by: Martin K. Petersen <>
Signed-off-by: Jiri Slaby <>
drivers/scsi/libsas/sas_ata.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/libsas/sas_ata.c b/drivers/scsi/libsas/sas_ata.c
index d2895836f9fa..83e3ca703cd1 100644
--- a/drivers/scsi/libsas/sas_ata.c
+++ b/drivers/scsi/libsas/sas_ata.c
@@ -219,7 +219,7 @@ static unsigned int sas_ata_qc_issue(struct ata_queued_cmd *qc)
task->num_scatter = qc->n_elem;
} else {
for_each_sg(qc->sg, sg, qc->n_elem, si)
- xfer += sg->length;
+ xfer += sg_dma_len(sg);

task->total_xfer_len = xfer;
task->num_scatter = si;
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