scsi: use dma_get_cache_alignment() as minimum DMA alignment

In non-coherent DMA mode, kernel uses cache flushing operations to
maintain I/O coherency, so scsi's block queue should be aligned to the
value returned by dma_get_cache_alignment().  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.

Cc: stable@vger.kernel.org
Signed-off-by: Huacai Chen <chenhc@lemote.com>
[hch: rebased and updated the comment and changelog]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 1cbc497e00bd..00742c50cd44 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2148,11 +2148,13 @@ 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
-         * blk_queue_update_dma_alignment() later.
+         * Set a reasonable default alignment:  The larger of 32-byte (dword),
+         * which is a common minimum for HBAs, and the minimum DMA alignment,
+         * which is set by the platform.
+         *
+         * Devices that require a bigger alignment can increase it later.
          */
-        blk_queue_dma_alignment(q, 0x03);
+        blk_queue_dma_alignment(q, max(4, dma_get_cache_alignment()) - 1);
 }
 EXPORT_SYMBOL_GPL(__scsi_init_queue);