[PATCH V7 5/9] fs/xfs: Create function xfs_inode_enable_dax()

[ira.weiny@intel.com]

From: Ira Weiny <ira.weiny@intel.com>

xfs_inode_supports_dax() should reflect if the inode can support DAX not
that it is enabled for DAX.

Change the use of xfs_inode_supports_dax() to reflect only if the inode
and underlying storage support dax.

Add a new function xfs_inode_enable_dax() which reflects if the inode
should be enabled for DAX.

Signed-off-by: Ira Weiny <ira.weiny@intel.com>

---
Changes from v6:
	Change enable checks to be sequential logic.
	Update for 2 bit tri-state option.
	Make 'static' consistent.
	Don't set S_DAX if !CONFIG_FS_DAX

Changes from v5:
	Update to reflect the new tri-state mount option

Changes from v3:
	Update functions and names to be more clear
	Update commit message
	Merge with
		'fs/xfs: Clean up DAX support check'
		don't allow IS_DAX() on a directory
		use STATIC macro for static
		make xfs_inode_supports_dax() static
---
 fs/xfs/xfs_iops.c | 34 +++++++++++++++++++++++++++++-----
 1 file changed, 29 insertions(+), 5 deletions(-)

diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 81f2f93caec0..37bd15b55878 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -1244,12 +1244,11 @@ xfs_inode_supports_dax(
 	struct xfs_mount	*mp = ip->i_mount;
 
 	/* Only supported on non-reflinked files. */
-	if (!S_ISREG(VFS_I(ip)->i_mode) || xfs_is_reflink_inode(ip))
+	if (xfs_is_reflink_inode(ip))
 		return false;
 
-	/* DAX mount option or DAX iflag must be set. */
-	if (!(mp->m_flags & XFS_MOUNT_DAX) &&
-	    !(ip->i_d.di_flags2 & XFS_DIFLAG2_DAX))
+	/* Only supported on regular files. */
+	if (!S_ISREG(VFS_I(ip)->i_mode))
 		return false;
 
 	/* Block size must match page size */
@@ -1260,6 +1259,31 @@ xfs_inode_supports_dax(
 	return xfs_inode_buftarg(ip)->bt_daxdev != NULL;
 }
 
+#ifdef CONFIG_FS_DAX
+static bool
+xfs_inode_enable_dax(
+	struct xfs_inode *ip)
+{
+	if (ip->i_mount->m_flags & XFS_MOUNT_NODAX)
+		return false;
+	if (!xfs_inode_supports_dax(ip))
+		return false;
+	if (ip->i_mount->m_flags & XFS_MOUNT_DAX)
+		return true;
+	if (ip->i_d.di_flags2 & XFS_DIFLAG2_DAX)
+		return true;
+	return false;
+}
+#else /* !CONFIG_FS_DAX */
+static bool
+xfs_inode_enable_dax(
+	struct xfs_inode *ip)
+{
+	return false;
+}
+#endif /* CONFIG_FS_DAX */
+
+
 STATIC void
 xfs_diflags_to_iflags(
 	struct inode		*inode,
@@ -1278,7 +1302,7 @@ xfs_diflags_to_iflags(
 		inode->i_flags |= S_SYNC;
 	if (flags & XFS_DIFLAG_NOATIME)
 		inode->i_flags |= S_NOATIME;
-	if (xfs_inode_supports_dax(ip))
+	if (xfs_inode_enable_dax(ip))
 		inode->i_flags |= S_DAX;
 }
 
-- 
2.25.1