linux-kernel - [PATCH v2-UPDATE 3/3] xfs: Add alignment check for DAX mount

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Message-Id: <1462376761-15584-1-git-send-email-toshi.kani@hpe.com>
Date:	Wed,  4 May 2016 09:46:01 -0600
From:	Toshi Kani <toshi.kani@....com>
To:	dan.j.williams@...el.com, david@...morbit.com
Cc:	jack@...e.cz, hch@...radead.org, boaz@...xistor.com, tytso@....edu,
	adilger.kernel@...ger.ca, ross.zwisler@...ux.intel.com,
	toshi.kani@....com, micah.parrish@....com,
	linux-nvdimm@...ts.01.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2-UPDATE 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.

Call bdev_direct_access to check the alignment when -o dax is
specified.

Signed-off-by: Toshi Kani <toshi.kani@....com>
Reviewed-by: Boaz Harrosh <boaz@...xistor.com>
Reviewed-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
Cc: Dave Chinner <david@...morbit.com>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>
Cc: Christoph Hellwig <hch@...radead.org>
Cc: Boaz Harrosh <boaz@...xistor.com>
---
v2-UPDATE
 - Add a period and fix a typo in error messages (Ross Zwisler)
---
 fs/xfs/xfs_super.c |   25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 187e14b..ac18fae 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1557,15 +1557,30 @@ xfs_fs_fill_super(
 		sb->s_flags |= MS_I_VERSION;
 
 	if (mp->m_flags & XFS_MOUNT_DAX) {
+		struct blk_dax_ctl dax = {
+			.sector = 0,
+			.size = PAGE_SIZE,
+		};
 		xfs_warn(mp,
-	"DAX enabled. Warning: EXPERIMENTAL, use at your own risk");
+		"DAX enabled. Warning: EXPERIMENTAL, use at your own risk");
 		if (sb->s_blocksize != PAGE_SIZE) {
 			xfs_alert(mp,
-		"Filesystem block size invalid for DAX Turning DAX off.");
+		"Filesystem block size 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.");
+		} else if ((error = bdev_direct_access(sb->s_bdev, &dax)) < 0) {
+			switch (error) {
+			case -EOPNOTSUPP:
+				xfs_alert(mp,
+			"Block device does not support DAX. Turning DAX off.");
+				break;
+			case -EINVAL:
+				xfs_alert(mp,
+			"Partition alignment invalid for DAX. Turning DAX off.");
+				break;
+			default:
+				xfs_alert(mp,
+			"DAX access failed (%d). Turning DAX off.", error);
+			}
 			mp->m_flags &= ~XFS_MOUNT_DAX;
 		}
 	}