From: Huacai Chen Date: Tue, 21 Nov 2017 13:23:38 +0000 (+0100) Subject: scsi: use dma_get_cache_alignment() as minimum DMA alignment X-Git-Tag: v3.2.100~134 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d8c8a1a737d61e2e9b152564591f62ea8e62a434;p=thirdparty%2Fkernel%2Fstable.git scsi: use dma_get_cache_alignment() as minimum DMA alignment commit 90addc6b3c9cda0146fbd62a08e234c2b224a80c upstream. 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. Signed-off-by: Huacai Chen [hch: rebased and updated the comment and changelog] Signed-off-by: Christoph Hellwig Signed-off-by: Martin K. Petersen [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index f6a464a80a3fb..823f0e95869a3 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -1688,11 +1688,13 @@ struct request_queue *__scsi_alloc_queue(struct Scsi_Host *shost, 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); return q; }