ceph: support hidden vxattrs

Add ability to flag virtual xattrs as hidden, such that you can
getxattr them but they do not appear in listxattr.
Signed-off-by: Sage Weil <sage@inktank.com>
Reviewed-by: Sam Lang <sam.lang@inktank.com>

fs/ceph/xattr.c

@@ -29,7 +29,7 @@ struct ceph_vxattr {
 	size_t name_size;	/* strlen(name) + 1 (for '\0') */
 	size_t (*getxattr_cb)(struct ceph_inode_info *ci, char *val,
 			      size_t size);
-	bool readonly;
+	bool readonly, hidden;
 };
 
 /* directories */
@@ -91,6 +91,7 @@ static size_t ceph_vxattrcb_dir_rctime(struct ceph_inode_info *ci, char *val,
 		.name_size = sizeof (CEPH_XATTR_NAME(_type, _name)), \
 		.getxattr_cb = ceph_vxattrcb_ ## _type ## _ ## _name, \
 		.readonly = true,				\
+		.hidden = false,				\
 	}
 
 static struct ceph_vxattr ceph_dir_vxattrs[] = {
@@ -157,6 +158,7 @@ static size_t __init vxattrs_name_size(struct ceph_vxattr *vxattrs)
 	size_t size = 0;
 
 	for (vxattr = vxattrs; vxattr->name; vxattr++)
+		if (!vxattr->hidden)
 			size += vxattr->name_size;
 
 	return size;