ovl: check on mount time if upper fs supports setting xattr

xattr are needed by overlayfs for setting opaque dir, redirect dir
and copy up origin.

Check at mount time by trying to set the overlay.opaque xattr on the
workdir and if that fails issue a warning message.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index cfdea47..b5a0dc3 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -303,3 +303,24 @@ void ovl_copy_up_end(struct dentry *dentry)
 	wake_up_locked(&ofs->copyup_wq);
 	spin_unlock(&ofs->copyup_wq.lock);
 }
+
+int ovl_check_setxattr(struct dentry *dentry, struct dentry *upperdentry,
+		       const char *name, const void *value, size_t size,
+		       int xerr)
+{
+	int err;
+	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+
+	if (ofs->noxattr)
+		return xerr;
+
+	err = ovl_do_setxattr(upperdentry, name, value, size, 0);
+
+	if (err == -EOPNOTSUPP) {
+		pr_warn("overlayfs: cannot set %s xattr on upper\n", name);
+		ofs->noxattr = true;
+		return xerr;
+	}
+
+	return err;
+}