[PATCH 10/17] fs: use boolean to indicate anonymous mount namespace

Christian Brauner
2025-11-10T15:09:33Z

Stop playing games with the namespace id and use a boolean instead:

* This will remove the special-casing we need to do everywhere for mount
namespaces.

* It will allow us to use asserts on the namespace id for initial
namespaces everywhere.

* It will allow us to put anonymous mount namespaces on the namespaces
trees in the future and thus make them available to statmount() and
listmount().

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
fs/mount.h | 3 ++-
fs/namespace.c | 5 +++--
2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/mount.h b/fs/mount.h
index f13a28752d0b..2d28ef2a3aed 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -27,6 +27,7 @@ struct mnt_namespace {
unsigned int nr_mounts; /* # of mounts in the namespace */
unsigned int pending_mounts;
refcount_t passive; /* number references not pinning @mounts */
+ bool is_anon;
} __randomize_layout;

struct mnt_pcp {
@@ -175,7 +176,7 @@ static inline bool is_local_mountpoint(const struct dentry *dentry)

static inline bool is_anon_ns(struct mnt_namespace *ns)
{
- return ns->ns.ns_id == 0;
+ return ns->is_anon;
}

static inline bool anon_ns_root(const struct mount *m)
diff --git a/fs/namespace.c b/fs/namespace.c
index ad19530a13b2..efaff8680eaf 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4093,8 +4093,9 @@ static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns, bool a
dec_mnt_namespaces(ucounts);
return ERR_PTR(ret);
}
- if (!anon)
- ns_tree_gen_id(new_ns);
+ ns_tree_gen_id(new_ns);
+
+ new_ns->is_anon = anon;
refcount_set(&new_ns->passive, 1);
new_ns->mounts = RB_ROOT;
init_waitqueue_head(&new_ns->poll);

--
2.47.3