[PATCH] xfs: return correct XFS_IOC_DIOINFO for DAX inode

[Eric Sandeen <sandeen@xxxxxxxxxx>]

pmem is byte addressable, and indeed byte-aligned DIO works on
a DAX file.  So, teach XFS_IOC_DIOINFO to return the correct
alignment information if IS_DAX(inode).

Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
---

diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 6ecdbb3..35eae7d 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -1919,12 +1919,21 @@ xfs_file_ioctl(
 	}
 	case XFS_IOC_DIOINFO: {
 		struct dioattr	da;
-		xfs_buftarg_t	*target =
-			XFS_IS_REALTIME_INODE(ip) ?
-			mp->m_rtdev_targp : mp->m_ddev_targp;
 
-		da.d_mem =  da.d_miniosz = target->bt_logical_sectorsize;
-		da.d_maxiosz = INT_MAX & ~(da.d_miniosz - 1);
+		if (IS_DAX(inode)) {
+			/* pmem is byte addressable */
+			da.d_mem = 1;
+			da.d_miniosz = 1;
+			da.d_maxiosz = INT_MAX;
+		} else {
+			xfs_buftarg_t	*target =
+				XFS_IS_REALTIME_INODE(ip) ?
+				mp->m_rtdev_targp : mp->m_ddev_targp;
+
+			da.d_mem = target->bt_logical_sectorsize;
+			da.d_miniosz = target->bt_logical_sectorsize;
+			da.d_maxiosz = INT_MAX & ~(da.d_miniosz - 1);
+		}
 
 		if (copy_to_user(arg, &da, sizeof(da)))
 			return -EFAULT;