[PATCH 4.4 012/105] scsi: libsas: align sata_devices rps_resp on a cacheline

[Greg Kroah-Hartman]

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

------------------

From: Huacai Chen <chenhc@xxxxxxxxxx>

commit c2e8fbf908afd81ad502b567a6639598f92c9b9d upstream.

The rps_resp buffer in ata_device is a DMA target, but it isn't
explicitly cacheline aligned. Due to this, adjacent fields can be
overwritten with stale data from memory on non-coherent architectures.
As a result, the kernel is sometimes unable to communicate with an SATA
device behind a SAS expander.

Fix this by ensuring that the rps_resp buffer is cacheline aligned.

This issue is similar to that fixed by Commit 84bda12af31f93 ("libata:
align ap->sector_buf") and Commit 4ee34ea3a12396f35b26 ("libata: Align
ata_device's id on a cacheline").

Signed-off-by: Huacai Chen <chenhc@xxxxxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 include/scsi/libsas.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/scsi/libsas.h
+++ b/include/scsi/libsas.h
@@ -165,11 +165,11 @@ struct expander_device {
 
 struct sata_device {
 	unsigned int class;
-	struct smp_resp        rps_resp; /* report_phy_sata_resp */
 	u8     port_no;        /* port number, if this is a PM (Port) */
 
 	struct ata_port *ap;
 	struct ata_host ata_host;
+	struct smp_resp rps_resp ____cacheline_aligned; /* report_phy_sata_resp */
 	u8     fis[ATA_RESP_FIS_SIZE];
 };