fs/xfs: Combine xfs_diflags_to_linux() and xfs_diflags_to_iflags()

The functionality in xfs_diflags_to_linux() and xfs_diflags_to_iflags() are
nearly identical.  The only difference is that *_to_linux() is called after
inode setup and disallows changing the DAX flag.

Combining them can be done with a flag which indicates if this is the initial
setup to allow the DAX flag to be properly set only at init time.

So remove xfs_diflags_to_linux() and call the modified xfs_diflags_to_iflags()
directly.

While we are here simplify xfs_diflags_to_iflags() to take struct xfs_inode and
use xfs_ip2xflags() to ensure future diflags are included correctly.

Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/xfs_inode.h

@@ -466,6 +466,7 @@ int	xfs_break_layouts(struct inode *inode, uint *iolock,
 /* from xfs_iops.c */
 extern void xfs_setup_inode(struct xfs_inode *ip);
 extern void xfs_setup_iops(struct xfs_inode *ip);
+extern void xfs_diflags_to_iflags(struct xfs_inode *ip, bool init);
 
 /*
  * When setting up a newly allocated inode, we need to call

fs/xfs/xfs_ioctl.c

@@ -1201,37 +1201,6 @@ xfs_flags2diflags2(
 	return di_flags2;
 }
 
-STATIC void
-xfs_diflags_to_linux(
-	struct xfs_inode	*ip)
-{
-	struct inode		*inode = VFS_I(ip);
-	unsigned int		xflags = xfs_ip2xflags(ip);
-
-	if (xflags & FS_XFLAG_IMMUTABLE)
-		inode->i_flags |= S_IMMUTABLE;
-	else
-		inode->i_flags &= ~S_IMMUTABLE;
-	if (xflags & FS_XFLAG_APPEND)
-		inode->i_flags |= S_APPEND;
-	else
-		inode->i_flags &= ~S_APPEND;
-	if (xflags & FS_XFLAG_SYNC)
-		inode->i_flags |= S_SYNC;
-	else
-		inode->i_flags &= ~S_SYNC;
-	if (xflags & FS_XFLAG_NOATIME)
-		inode->i_flags |= S_NOATIME;
-	else
-		inode->i_flags &= ~S_NOATIME;
-#if 0	/* disabled until the flag switching races are sorted out */
-	if (xflags & FS_XFLAG_DAX)
-		inode->i_flags |= S_DAX;
-	else
-		inode->i_flags &= ~S_DAX;
-#endif
-}
-
 static int
 xfs_ioctl_setattr_xflags(
 	struct xfs_trans	*tp,
@@ -1269,7 +1238,7 @@ xfs_ioctl_setattr_xflags(
 	ip->i_d.di_flags = xfs_flags2diflags(ip, fa->fsx_xflags);
 	ip->i_d.di_flags2 = di_flags2;
 
-	xfs_diflags_to_linux(ip);
+	xfs_diflags_to_iflags(ip, false);
 	xfs_trans_ichgtime(tp, ip, XFS_ICHGTIME_CHG);
 	xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 	XFS_STATS_INC(mp, xs_ig_attrchg);

fs/xfs/xfs_iops.c

@@ -1276,26 +1276,34 @@ xfs_inode_should_enable_dax(
 	return false;
 }
 
-STATIC void
+void
 xfs_diflags_to_iflags(
-	struct inode		*inode,
+	struct xfs_inode	*ip,
-	struct xfs_inode	*ip)
+	bool init)
 {
-	uint16_t		flags = ip->i_d.di_flags;
+	struct inode            *inode = VFS_I(ip);
+	unsigned int            xflags = xfs_ip2xflags(ip);
+	unsigned int            flags = 0;
 
-	inode->i_flags &= ~(S_IMMUTABLE | S_APPEND | S_SYNC |
+	ASSERT(!(IS_DAX(inode) && init));
-			    S_NOATIME | S_DAX);
 
-	if (flags & XFS_DIFLAG_IMMUTABLE)
+	if (xflags & FS_XFLAG_IMMUTABLE)
-		inode->i_flags |= S_IMMUTABLE;
+		flags |= S_IMMUTABLE;
-	if (flags & XFS_DIFLAG_APPEND)
+	if (xflags & FS_XFLAG_APPEND)
-		inode->i_flags |= S_APPEND;
+		flags |= S_APPEND;
-	if (flags & XFS_DIFLAG_SYNC)
+	if (xflags & FS_XFLAG_SYNC)
-		inode->i_flags |= S_SYNC;
+		flags |= S_SYNC;
-	if (flags & XFS_DIFLAG_NOATIME)
+	if (xflags & FS_XFLAG_NOATIME)
-		inode->i_flags |= S_NOATIME;
+		flags |= S_NOATIME;
-	if (xfs_inode_should_enable_dax(ip))
+	if (init && xfs_inode_should_enable_dax(ip))
-		inode->i_flags |= S_DAX;
+		flags |= S_DAX;
+
+	/*
+	 * S_DAX can only be set during inode initialization and is never set by
+	 * the VFS, so we cannot mask off S_DAX in i_flags.
+	 */
+	inode->i_flags &= ~(S_IMMUTABLE | S_APPEND | S_SYNC | S_NOATIME);
+	inode->i_flags |= flags;
 }
 
 /*
@@ -1321,7 +1329,7 @@ xfs_setup_inode(
 	inode_fake_hash(inode);
 
 	i_size_write(inode, ip->i_d.di_size);
-	xfs_diflags_to_iflags(inode, ip);
+	xfs_diflags_to_iflags(ip, true);
 
 	if (S_ISDIR(inode->i_mode)) {
 		/*