linux-kernel - [PATCH V9 4/4] libsas: Align sata_device's rps

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Date:   Mon, 23 Oct 2017 15:12:47 +0800
From:   Huacai Chen <chenhc@...ote.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Fuxin Zhang <zhangfx@...ote.com>, linux-kernel@...r.kernel.org,
        Ralf Baechle <ralf@...ux-mips.org>,
        James Hogan <james.hogan@...tec.com>,
        linux-mips@...ux-mips.org,
        "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, Huacai Chen <chenhc@...ote.com>,
        stable@...r.kernel.org
Subject: [PATCH V9 4/4] libsas: Align sata_device's rps_resp on a cacheline

The rps_resp buffer in ata_device is a DMA target, but it isn't
explicitly cacheline aligned. Due to this, adjacent fields can be
overwritten with stale data from memory on non-coherent architectures.
As a result, the kernel is sometimes unable to communicate with an
SATA device behind a SAS expander.

Fix this by ensuring that the rps_resp buffer is cacheline aligned.

This issue is similar to that fixed by Commit 84bda12af31f93 ("libata:
align ap->sector_buf") and Commit 4ee34ea3a12396f35b26 ("libata: Align
ata_device's id on a cacheline").

Cc: stable@...r.kernel.org
Signed-off-by: Huacai Chen <chenhc@...ote.com>
---
 include/scsi/libsas.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/scsi/libsas.h b/include/scsi/libsas.h
index 6c0dc61..a966d28 100644
--- a/include/scsi/libsas.h
+++ b/include/scsi/libsas.h
@@ -165,11 +165,11 @@ struct expander_device {
 
 struct sata_device {
 	unsigned int class;
-	struct smp_resp        rps_resp; /* report_phy_sata_resp */
 	u8     port_no;        /* port number, if this is a PM (Port) */
 
 	struct ata_port *ap;
 	struct ata_host ata_host;
+	struct smp_resp rps_resp ____cacheline_aligned; /* report_phy_sata_resp */
 	u8     fis[ATA_RESP_FIS_SIZE];
 };
 
-- 
2.7.0