linux-kernel - [PATCH 3/3] xfs: Add alignment check for DAX mount

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Date:	Fri, 29 Apr 2016 14:39:35 -0600
From:	Toshi Kani <toshi.kani@....com>
To:	dan.j.williams@...el.com, david@...morbit.com, jack@...e.cz
Cc:	tytso@....edu, adilger.kernel@...ger.ca,
	ross.zwisler@...ux.intel.com, toshi.kani@....com,
	linux-nvdimm@...ts.01.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] xfs: Add alignment check for DAX mount

When a partition is not aligned by 4KB, mount -o dax succeeds,
but any read/write access to the filesystem fails, except for
metadata update.

Add alignment check to xfs_fs_fill_super() when -o dax is
specified.

Signed-off-by: Toshi Kani <toshi.kani@....com>
Cc: Dave Chinner <david@...morbit.com> (supporter:XFS FILESYSTEM)
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>
---
 fs/xfs/xfs_super.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 187e14b..a17aebc 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1563,6 +1563,11 @@ xfs_fs_fill_super(
 			xfs_alert(mp,
 		"Filesystem block size invalid for DAX Turning DAX off.");
 			mp->m_flags &= ~XFS_MOUNT_DAX;
+		} else if (sb->s_bdev->bd_part->start_sect % (PAGE_SIZE / 512)
+		   || sb->s_bdev->bd_part->nr_sects % (PAGE_SIZE / 512)) {
+			xfs_alert(mp,
+		"Partition alignment invalid for DAX Turning DAX off.");
+			mp->m_flags &= ~XFS_MOUNT_DAX;
 		} else if (!sb->s_bdev->bd_disk->fops->direct_access) {
 			xfs_alert(mp,
 		"Block device does not support DAX Turning DAX off.");