scsi: libsas: align sata_device's rps_resp on a cacheline

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@lemote.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/include/scsi/libsas.h b/include/scsi/libsas.h
index 44b1c75..40e5fb9 100644 (file)
--- a/include/scsi/libsas.h
+++ b/include/scsi/libsas.h
@@ -163,7 +163,6 @@ enum ata_command_set {
 
 struct sata_device {
         enum   ata_command_set command_set;
-        struct smp_resp        rps_resp; /* report_phy_sata_resp */
         __le16 *identify_device;
         __le16 *identify_packet_device;
 
@@ -172,6 +171,7 @@ struct sata_device {
 
        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];
 };