[PATCH V10 3/4] scsi: Align block queue to dma_get_cache_alignment()

[PATCH V10 3/4] scsi: Align block queue to dma_get_cache_alignment()

[Huacai Chen]

In non-coherent DMA mode, kernel uses cache flushing operations to
maintain I/O coherency, so scsi's block queue should be aligned to
ARCH_DMA_MINALIGN. Otherwise, If a DMA buffer and a kernel structure
share a same cache line, and if the kernel structure has dirty data,
cache_invalidate (no writeback) will cause data corruption.

Signed-off-by: Huacai Chen <chenhc@lemote.com>
---
 drivers/scsi/scsi_lib.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 1cbc497..cc4ac97 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2148,11 +2148,11 @@ void __scsi_init_queue(struct Scsi_Host *shost, struct request_queue *q)
 		q->limits.cluster = 0;
 
 	/*
-	 * set a reasonable default alignment on word boundaries: the
-	 * host and device may alter it using
+	 * set a reasonable default alignment on word/cacheline boundaries:
+	 * the host and device may alter it using
 	 * blk_queue_update_dma_alignment() later.
 	 */
-	blk_queue_dma_alignment(q, 0x03);
+	blk_queue_dma_alignment(q, max(4, dma_get_cache_alignment(dev)) - 1);
 }
 EXPORT_SYMBOL_GPL(__scsi_init_queue);
 
-- 
2.7.0