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    Subject[PATCH 3.2 009/140] scsi: libsas: align sata_device's rps_resp on a cacheline
    3.2.100-rc1 review patch.  If anyone has any objections, please let me know.

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

    From: Huacai Chen <chenhc@lemote.com>

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

    --- 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];
    };

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