[PATCH v4 5/6] xfs: Add alignment check for DAX mount

Toshi Kani
2016-05-10T16:33:15Z

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_dax_supported() to perform proper precondition checks
which includes this partition alignment check.

Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Boaz Harrosh <boaz@plexistor.com>
---
fs/xfs/xfs_super.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 187e14b..39f4e6a 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1558,14 +1558,12 @@ xfs_fs_fill_super(

if (mp->m_flags & XFS_MOUNT_DAX) {
xfs_warn(mp,
- "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.");
- mp->m_flags &= ~XFS_MOUNT_DAX;
- } else if (!sb->s_bdev->bd_disk->fops->direct_access) {
+ "DAX enabled. Warning: EXPERIMENTAL, use at your own risk");
+
+ error = bdev_dax_supported(sb, sb->s_blocksize);
+ if (error) {
xfs_alert(mp,
- "Block device does not support DAX Turning DAX off.");
+ "DAX unsupported by block device. Turning off DAX.");
mp->m_flags &= ~XFS_MOUNT_DAX;
}
}