Patch "scsi: use dma_get_cache_alignment() as minimum DMA alignment" has been added to the 4.9-stable tree

Patch "scsi: use dma_get_cache_alignment() as minimum DMA alignment" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    scsi: use dma_get_cache_alignment() as minimum DMA alignment

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     scsi-use-dma_get_cache_alignment-as-minimum-dma-alignment.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 90addc6b3c9cda0146fbd62a08e234c2b224a80c Mon Sep 17 00:00:00 2001
From: Huacai Chen <chenhc@lemote.com>
Date: Tue, 21 Nov 2017 14:23:38 +0100
Subject: scsi: use dma_get_cache_alignment() as minimum DMA alignment

From: Huacai Chen <chenhc@lemote.com>

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 <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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/scsi/scsi_lib.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2041,11 +2041,13 @@ static void __scsi_init_queue(struct Scs
 		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);
 }
 
 struct request_queue *__scsi_alloc_queue(struct Scsi_Host *shost,


Patches currently in stable-queue which might be from chenhc@lemote.com are

queue-4.9/scsi-use-dma_get_cache_alignment-as-minimum-dma-alignment.patch
queue-4.9/scsi-libsas-align-sata_device-s-rps_resp-on-a-cacheline.patch