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    Subject[PATCH 17/91] libata: set queue DMA alignment to sector size for ATAPI too
    2.6.27-longterm review patch.  If anyone has any objections, please let us know.

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

    commit 729a6a300e628a48cf12bac93a964a535e83cd1d upstream.

    ata_pio_sectors() expects buffer for each sector to be contained in a
    single page; otherwise, it ends up overrunning the first page. This
    is achieved by setting queue DMA alignment. If sector_size is smaller
    than PAGE_SIZE and all buffers are sector_size aligned, buffer for
    each sector is always contained in a single page.

    This wasn't applied to ATAPI devices but IDENTIFY_PACKET is executed
    as ATA_PROT_PIO and thus uses ata_pio_sectors(). Newer versions of
    udev issue IDENTIFY_PACKET with unaligned buffer triggering the
    problem and causing oops.

    This patch fixes the problem by setting sdev->sector_size to
    ATA_SECT_SIZE on ATATPI devices and always setting DMA alignment to
    sector_size. While at it, add a warning for the unlikely but still
    possible scenario where sector_size is larger than PAGE_SIZE, in which
    case the alignment wouldn't be enough.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    Reported-by: John Stanley <jpsinthemix@verizon.net>
    Tested-by: John Stanley <jpsinthemix@verizon.net>
    Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
    Signed-off-by: Jonathan Liu <net147@gmail.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    ---
    drivers/ata/libata-scsi.c | 24 ++++++++++++++++++------
    1 files changed, 18 insertions(+), 6 deletions(-)

    Index: longterm-2.6.27/drivers/ata/libata-scsi.c
    ===================================================================
    --- longterm-2.6.27.orig/drivers/ata/libata-scsi.c 2012-02-05 22:34:34.505914937 +0100
    +++ longterm-2.6.27/drivers/ata/libata-scsi.c 2012-02-05 22:34:37.312916183 +0100
    @@ -957,13 +957,13 @@
    /* configure max sectors */
    blk_queue_max_sectors(sdev->request_queue, dev->max_sectors);

    + sdev->sector_size = ATA_SECT_SIZE;
    +
    if (dev->class == ATA_DEV_ATAPI) {
    struct request_queue *q = sdev->request_queue;
    void *buf;

    - /* set the min alignment and padding */
    - blk_queue_update_dma_alignment(sdev->request_queue,
    - ATA_DMA_PAD_SZ - 1);
    + /* set DMA padding */
    blk_queue_update_dma_pad(sdev->request_queue,
    ATA_DMA_PAD_SZ - 1);

    @@ -977,12 +977,24 @@

    blk_queue_dma_drain(q, atapi_drain_needed, buf, ATAPI_MAX_DRAIN);
    } else {
    - /* ATA devices must be sector aligned */
    - blk_queue_update_dma_alignment(sdev->request_queue,
    - ATA_SECT_SIZE - 1);
    sdev->manage_start_stop = 1;
    }

    + /*
    + * ata_pio_sectors() expects buffer for each sector to not cross
    + * page boundary. Enforce it by requiring buffers to be sector
    + * aligned, which works iff sector_size is not larger than
    + * PAGE_SIZE. ATAPI devices also need the alignment as
    + * IDENTIFY_PACKET is executed as ATA_PROT_PIO.
    + */
    + if (sdev->sector_size > PAGE_SIZE)
    + ata_dev_printk(dev, KERN_WARNING,
    + "sector_size=%u > PAGE_SIZE, PIO may malfunction\n",
    + sdev->sector_size);
    +
    + blk_queue_update_dma_alignment(sdev->request_queue,
    + sdev->sector_size - 1);
    +
    if (dev->flags & ATA_DFLAG_AN)
    set_bit(SDEV_EVT_MEDIA_CHANGE, sdev->supported_events);




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