OverlayFS already has comprehensive support for idmapped mounts through its ovl_copyattr() function and proper mnt_idmap() handling throughout the codebase. The infrastructure correctly maps UIDs/GIDs from idmapped upper and lower layers. However, the filesystem was missing the FS_ALLOW_IDMAP flag, which caused mount_setattr() calls with MOUNT_ATTR_IDMAP to fail with -EINVAL. This change enables idmapped mount support by adding the FS_ALLOW_IDMAP flag to the overlayfs file_system_type, allowing containers and other applications to use idmapped mounts with overlay filesystems. Signed-off-by: Sohan Kunkerkar --- fs/overlayfs/super.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index e19940d64..c628f9179 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -1516,7 +1516,7 @@ struct file_system_type ovl_fs_type = { .name = "overlay", .init_fs_context = ovl_init_fs_context, .parameters = ovl_parameter_spec, - .fs_flags = FS_USERNS_MOUNT, + .fs_flags = FS_USERNS_MOUNT | FS_ALLOW_IDMAP, .kill_sb = kill_anon_super, }; MODULE_ALIAS_FS("overlay"); -- 2.50.1