fs: add mnt_ns_empty() helper

Add a helper that checks whether a give mount namespace is empty instead
of open-coding the specific data structure check. This also be will be
used in follow-up patches.

Link: https://lore.kernel.org/r/20250221-brauner-open_tree-v1-2-dbcfcb98c676@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/mount.h b/fs/mount.h
index 820a79f1f735..e2501a724688 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -157,6 +157,11 @@ static inline bool mnt_ns_attached(const struct mount *mnt)
 	return !RB_EMPTY_NODE(&mnt->mnt_node);
 }
 
+static inline bool mnt_ns_empty(const struct mnt_namespace *ns)
+{
+	return RB_EMPTY_ROOT(&ns->mounts);
+}
+
 static inline void move_from_ns(struct mount *mnt, struct list_head *dt_list)
 {
 	struct mnt_namespace *ns = mnt->mnt_ns;