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Date: Mon, 18 Sep 2017 12:22:54 +0800 From: Huacai Chen <chenhc@...ote.com> To: "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com> Cc: "Martin K . Petersen" <martin.petersen@...cle.com>, Andrew Morton <akpm@...ux-foundation.org>, Fuxin Zhang <zhangfx@...ote.com>, linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org, Huacai Chen <chenhc@...ote.com>, stable@...r.kernel.org Subject: [PATCH V5 3/3] scsi: Align queue to ARCH_DMA_MINALIGN in non-coherent DMA mode 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, it will cause data corruption, at least on MIPS: Step 1, dma_map_single Step 2, cache_invalidate (no writeback) Step 3, dma_from_device Step 4, dma_unmap_single 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 lost. Cc: stable@...r.kernel.org Signed-off-by: Huacai Chen <chenhc@...ote.com> --- drivers/scsi/scsi_lib.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 9cf6a80..d5059b9 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -2132,11 +2132,14 @@ 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); + if (device_is_coherent(dev)) + blk_queue_dma_alignment(q, 0x04 - 1); + else + blk_queue_dma_alignment(q, dma_get_cache_alignment() - 1); } EXPORT_SYMBOL_GPL(__scsi_init_queue); -- 2.7.0
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