From: Huacai Chen <che...@lemote.com>
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: sta...@vger.kernel.org
Signed-off-by: Huacai Chen <che...@lemote.com>
[hch: rebased and updated the comment and changelog]
Signed-off-by: Christoph Hellwig <h...@lst.de>
---
drivers/scsi/scsi_lib.c | 10 ++++++----
1 file 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);
--
2.14.2
