nsfs: generalize ns_get_path() for path resolution with a task

ns_get_path() takes struct task_struct and proc_ns_ops as its
parameters.  For path resolution directly from a namespace,
e.g. based on a networking device's net name space, we need
more flexibility.  Add a ns_get_path_cb() helper which will
allow callers to use any method of obtaining the name space
reference.  Convert ns_get_path() to use ns_get_path_cb().

Following patches will bring a networking user.

CC: Eric W. Biederman <ebiederm@xmission.com>
Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/proc_ns.h b/include/linux/proc_ns.h
index 2ff18c9840a7..d31cb6215905 100644
--- a/include/linux/proc_ns.h
+++ b/include/linux/proc_ns.h
@@ -78,6 +78,9 @@ extern struct file *proc_ns_fget(int fd);
 #define get_proc_ns(inode) ((struct ns_common *)(inode)->i_private)
 extern void *ns_get_path(struct path *path, struct task_struct *task,
 			const struct proc_ns_operations *ns_ops);
+typedef struct ns_common *ns_get_path_helper_t(void *);
+extern void *ns_get_path_cb(struct path *path, ns_get_path_helper_t ns_get_cb,
+			    void *private_data);
 
 extern int ns_get_name(char *buf, size_t size, struct task_struct *task,
 			const struct proc_ns_operations *ns_ops);