From: Huacai Chen chenhc@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: 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 --- 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);