Improve error msg on idmap mounts

Some filesystems don't support idmap mounts and just showing to the user invalid argument is not super clear. When errno is EINVAL, let's add a text hinting that the cause could be that idmap mounts are not supported on that filesystem used. Signed-off-by: Rodrigo Campos <[email protected]>
kinvolk · Dec 27, 2023 · 9917c3b · 9917c3b
1 parent f987a57
commit 9917c3b
Showing 1 changed file with 7 additions and 2 deletions.
diff --git a/src/libcrun/linux.c b/src/libcrun/linux.c
@@ -4018,6 +4018,7 @@ maybe_get_idmapped_mount (runtime_spec_schema_config_schema *def, runtime_spec_s
  char proc_path[64];
  bool has_mappings;
  int ret;
+ char *extraMsg = "";
 
  *out_fd = -1;
 
@@ -4081,8 +4082,12 @@ maybe_get_idmapped_mount (runtime_spec_schema_config_schema *def, runtime_spec_s
  attr.userns_fd = fd;
 
  ret = syscall_mount_setattr (newfs_fd, "", AT_EMPTY_PATH | (recursive ? AT_RECURSIVE : 0), &attr);
- if (UNLIKELY (ret < 0))
- return crun_make_error (err, errno, "mount_setattr `%s`", mnt->destination);
+ if (UNLIKELY (ret < 0)) {
+ if (errno == EINVAL) {
+ extraMsg = "(maybe the filesystem used doesn't support idmap mounts on this kernel?)";
+ }
+ return crun_make_error (err, errno, "mount_setattr `%s` %s", mnt->destination, extraMsg);
+ }
 
  *out_fd = get_and_reset (&newfs_fd);
  return 0;