mount: simplify __do_loopback()

Remove the OPEN_TREE_NAMESPACE flag checking from __do_loopback() and
instead have callers pass CL_COPY_MNT_NS_FILE directly in copy_flags.

Link: https://patch.msgid.link/20260122-work-fsmount-namespace-v1-2-5ef0a886e646@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/namespace.c b/fs/namespace.c
index 9fd5114e5eb71b8a2cd362a7ac1496cd09e3064d..b098d1131e69d809e5b61e64e92d46dfbbba3ba0 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2958,10 +2958,9 @@ static inline bool may_copy_tree(const struct path *path)
 }
 
 static struct mount *__do_loopback(const struct path *old_path,
-                                  unsigned int flags, unsigned int copy_flags)
+                                  bool recurse, unsigned int copy_flags)
 {
        struct mount *old = real_mount(old_path->mnt);
-       bool recurse = flags & AT_RECURSIVE;
 
        if (IS_MNT_UNBINDABLE(old))
                return ERR_PTR(-EINVAL);
@@ -2972,18 +2971,6 @@ static struct mount *__do_loopback(const struct path *old_path,
        if (!recurse && __has_locked_children(old, old_path->dentry))
                return ERR_PTR(-EINVAL);
 
-       /*
-        * When creating a new mount namespace we don't want to copy over
-        * mounts of mount namespaces to avoid the risk of cycles and also to
-        * minimize the default complex interdependencies between mount
-        * namespaces.
-        *
-        * We could ofc just check whether all mount namespace files aren't
-        * creating cycles but really let's keep this simple.
-        */
-       if (!(flags & OPEN_TREE_NAMESPACE))
-               copy_flags |= CL_COPY_MNT_NS_FILE;
-
        if (recurse)
                return copy_tree(old, old_path->dentry, copy_flags);
 
@@ -2998,7 +2985,6 @@ static int do_loopback(const struct path *path, const char *old_name,
 {
        struct path old_path __free(path_put) = {};
        struct mount *mnt = NULL;
-       unsigned int flags = recurse ? AT_RECURSIVE : 0;
        int err;
 
        if (!old_name || !*old_name)
@@ -3017,7 +3003,7 @@ static int do_loopback(const struct path *path, const char *old_name,
        if (!check_mnt(mp.parent))
                return -EINVAL;
 
-       mnt = __do_loopback(&old_path, flags, 0);
+       mnt = __do_loopback(&old_path, recurse, CL_COPY_MNT_NS_FILE);
        if (IS_ERR(mnt))
                return PTR_ERR(mnt);
 
@@ -3055,7 +3041,7 @@ static struct mnt_namespace *get_detached_copy(const struct path *path, unsigned
                        ns->seq_origin = src_mnt_ns->ns.ns_id;
        }
 
-       mnt = __do_loopback(path, flags, 0);
+       mnt = __do_loopback(path, (flags & AT_RECURSIVE), CL_COPY_MNT_NS_FILE);
        if (IS_ERR(mnt)) {
                emptied_ns = ns;
                return ERR_CAST(mnt);
@@ -3087,7 +3073,8 @@ static struct file *open_detached_copy(struct path *path, unsigned int flags)
        return file;
 }
 
-static struct mnt_namespace *create_new_namespace(struct path *path, unsigned int flags)
+static struct mnt_namespace *create_new_namespace(struct path *path,
+                                                 bool recurse)
 {
        struct mnt_namespace *ns = current->nsproxy->mnt_ns;
        struct user_namespace *user_ns = current_user_ns();
@@ -3135,7 +3122,7 @@ static struct mnt_namespace *create_new_namespace(struct path *path, unsigned in
         * to the restrictions of creating detached bind-mounts. It
         * has a lot saner and simpler semantics.
         */
-       mnt = __do_loopback(path, flags, copy_flags);
+       mnt = __do_loopback(path, recurse, copy_flags);
        scoped_guard(mount_writer) {
                if (IS_ERR(mnt)) {
                        emptied_ns = new_ns;
@@ -3164,11 +3151,11 @@ static struct mnt_namespace *create_new_namespace(struct path *path, unsigned in
        return new_ns;
 }
 
-static struct file *open_new_namespace(struct path *path, unsigned int flags)
+static struct file *open_new_namespace(struct path *path, bool recurse)
 {
        struct mnt_namespace *new_ns;
 
-       new_ns = create_new_namespace(path, flags);
+       new_ns = create_new_namespace(path, recurse);
        if (IS_ERR(new_ns))
                return ERR_CAST(new_ns);
        return open_namespace_file(to_ns_common(new_ns));
@@ -3217,7 +3204,7 @@ static struct file *vfs_open_tree(int dfd, const char __user *filename, unsigned
                return ERR_PTR(ret);
 
        if (flags & OPEN_TREE_NAMESPACE)
-               return open_new_namespace(&path, flags);
+               return open_new_namespace(&path, (flags & AT_RECURSIVE));
 
        if (flags & OPEN_TREE_CLONE)
                return open_detached_copy(&path, flags);