Re: [PATCH RFC v2] pidns: introduce syscall getvpid

On 09/24, Konstantin Khlebnikov wrote:

On Thu, Sep 24, 2015 at 5:56 PM, Oleg Nesterov [off-list ref] wrote:

quoted

On 09/24, Konstantin Khlebnikov wrote:

quoted

+SYSCALL_DEFINE3(getvpid, pid_t, pid, int, source, int, target)
+{
+     struct file *source_file = NULL, *target_file = NULL;
+     struct pid_namespace *source_ns, *target_ns;
+     struct pid *struct_pid;
+     struct ns_common *ns;
+     pid_t result;
+
+     if (source >= 0) {
+             source_file = proc_ns_fget(source);
+             result = PTR_ERR(source_file);
+             if (IS_ERR(source_file))
+                     goto out;
+             ns = get_proc_ns(file_inode(source_file));
+             result = -EINVAL;
+             if (ns->ops->type != CLONE_NEWPID)
+                     goto out;
+             source_ns = container_of(ns, struct pid_namespace, ns);
+     } else
+             source_ns = task_active_pid_ns(current);
+
+     if (target >= 0) {
+             target_file = proc_ns_fget(target);
+             result = PTR_ERR(target_file);
+             if (IS_ERR(target_file))
+                     goto out;
+             ns = get_proc_ns(file_inode(target_file));
+             result = -EINVAL;
+             if (ns->ops->type != CLONE_NEWPID)
+                     goto out;
+             target_ns = container_of(ns, struct pid_namespace, ns);
+     } else
+             target_ns = task_active_pid_ns(current);
+

Hmm. Eric, Konstantin, how about (uncompiled/untested) patch below
in a preparation? The code above doesn't look very readable.

I've tried to do something like that but that comes too far so send patch as is.

OK, I won't insist.

The code above asks for cleanup/factorization, but we can do this
later.

Actually we can go deeper and replace struct file* with struct fd: this saves
couple atomic ops for singlethreaded task.

it's not about performance...

But yes, we can do more and create get_pid_ns_by_fd() similar to
get_net_ns_by_fd(). We do not need file at all, we need pid_ns.

Oleg.