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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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