overlay needs underlying fs to support d_type. Recently I put in a patch in to detect this condition and started failing mount if underlying fs did not support d_type.
45aebea ovl: Ensure upper filesystem supports d_type But this breaks existing configurations over kernel upgrade. Those who are running docker (partially broken configuration) with xfs not supporting d_type, are surprised that after kernel upgrade docker does not run anymore. https://github.com/docker/docker/issues/22937#issuecomment-229881315 So instead of erroring out, detect broken configuration and warn about it. This should allow existing docker setups to continue working after kernel upgrade. Signed-off-by: Vivek Goyal <[email protected]> --- fs/overlayfs/super.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) Index: rhvgoyal-linux/fs/overlayfs/super.c =================================================================== --- rhvgoyal-linux.orig/fs/overlayfs/super.c 2016-07-01 09:25:48.642807088 -0400 +++ rhvgoyal-linux/fs/overlayfs/super.c 2016-07-01 09:31:58.194807088 -0400 @@ -1082,11 +1082,13 @@ static int ovl_fill_super(struct super_b if (err < 0) goto out_put_workdir; - if (!err) { - pr_err("overlayfs: upper fs needs to support d_type.\n"); - err = -EINVAL; - goto out_put_workdir; - } + /* + * We allowed this configuration and don't want to + * break users over kernel upgrade. So warn instead + * of erroring out. + */ + if (!err) + pr_warn("overlayfs: upper fs needs to support d_type.\n"); } }
