[PATCH] libata: align ap->sector_buf to cacheline

[Tejun Heo <htejun@gmail.com>]

ap->sector_buf is used as DMA target and misalignment can cause data
corruption on non-coherent architectures.  This problem is spotted and
initial patch is submitted by Mark Mason.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Mark Mason <mason@postdiluvian.org>
---
I thought about it more and marking up with ___cacheline_aligned seems
to be the right thing to do.  For older ones where ata_port is
allocated as part of scsi_host, I think what should be done is to
align private area of scsi_host to cacheline.  Will post another patch
for that.

Thanks.

 include/linux/libata.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
diff --git a/include/linux/libata.h b/include/linux/libata.h
index bc5a8d0..7604763 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -671,7 +671,8 @@ struct ata_port {
 	acpi_handle		acpi_handle;
 	struct ata_acpi_gtm	__acpi_init_gtm; /* use ata_acpi_init_gtm() */
 #endif
-	u8			sector_buf[ATA_SECT_SIZE]; /* owned by EH */
+	/* owned by EH, must be cache line aligned as it's used as DMA target */
+	u8			sector_buf[ATA_SECT_SIZE] ____cacheline_aligned;
 };
 
 struct ata_port_operations {