ovl: warn instead of error if d_type is not supported

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.

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 <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 45aebeaf4f67 ("ovl: Ensure upper filesystem supports d_type")
Cc: <stable@vger.kernel.org> 4.6

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index ce02f46029da7c3aa7c69be9291d62c81baeb642..9a7693d5f8fffb38bd4a07804e4627ed7f50361a 100644 (file)
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1082,11 +1082,13 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
                        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");
                }
        }