xfs: Make xfs_vn_rename compliant with renameat2() syscall

To be able to support RENAME_EXCHANGE flag from renameat2() system
call, XFS must have its inode_operations updated, exporting .rename2
method, instead of .rename.

This patch just replaces the (now old) .rename method by .rename2,
using the same infra-structure, but checking rename flags.  Calls to
.rename2 using RENAME_EXCHANGE flag, although now handled inside
XFS, still return -EINVAL.

RENAME_NOREPLACE is handled via VFS and we don't need to care about
it inside xfs_vn_rename.
Signed-off-by: NCarlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDave Chinner <david@fromorbit.com>

fs/xfs/xfs_iops.c

@@ -380,18 +380,23 @@ xfs_vn_rename(
 	struct inode	*odir,
 	struct dentry	*odentry,
 	struct inode	*ndir,
-	struct dentry	*ndentry)
+	struct dentry	*ndentry,
+	unsigned int	flags)
 {
 	struct inode	*new_inode = ndentry->d_inode;
 	struct xfs_name	oname;
 	struct xfs_name	nname;
 
+	/* XFS does not support RENAME_EXCHANGE yet */
+	if (flags & ~RENAME_NOREPLACE)
+		return -EINVAL;
+
 	xfs_dentry_to_name(&oname, odentry, 0);
 	xfs_dentry_to_name(&nname, ndentry, odentry->d_inode->i_mode);
 
 	return xfs_rename(XFS_I(odir), &oname, XFS_I(odentry->d_inode),
-			  XFS_I(ndir), &nname, new_inode ?
-						XFS_I(new_inode) : NULL);
+			  XFS_I(ndir), &nname,
+			  new_inode ? XFS_I(new_inode) : NULL);
 }
 
 /*
@@ -1144,7 +1149,7 @@ static const struct inode_operations xfs_dir_inode_operations = {
 	 */
 	.rmdir			= xfs_vn_unlink,
 	.mknod			= xfs_vn_mknod,
-	.rename			= xfs_vn_rename,
+	.rename2		= xfs_vn_rename,
 	.get_acl		= xfs_get_acl,
 	.set_acl		= xfs_set_acl,
 	.getattr		= xfs_vn_getattr,
@@ -1172,7 +1177,7 @@ static const struct inode_operations xfs_dir_ci_inode_operations = {
 	 */
 	.rmdir			= xfs_vn_unlink,
 	.mknod			= xfs_vn_mknod,
-	.rename			= xfs_vn_rename,
+	.rename2		= xfs_vn_rename,
 	.get_acl		= xfs_get_acl,
 	.set_acl		= xfs_set_acl,
 	.getattr		= xfs_vn_getattr,