On Mon, 2 Apr 2018 15:57:29 -0600 nagarathnam.muthusamy@xxxxxxxxxx wrote: > pid_t translate_pid(pid_t pid, int source, int target); > > This syscall converts pid from source pid-ns into pid in target pid-ns. > If pid is unreachable from target pid-ns it returns zero. > > Pid-namespaces are referred file descriptors opened to proc files > /proc/[pid]/ns/pid or /proc/[pid]/ns/pid_for_children. Negative argument > refers to current pid namespace, same as file /proc/self/ns/pid. > > Kernel expose virtual pids in /proc/[pid]/status:NSpid, but backward > translation requires scanning all tasks. Also pids could be translated > by sending them through unix socket between namespaces, this method is > slow and insecure because other side is exposed inside pid namespace. > > Examples: > translate_pid(pid, ns, -1) - get pid in our pid namespace > translate_pid(pid, -1, ns) - get pid in other pid namespace > translate_pid(1, ns, -1) - get pid of init task for namespace > translate_pid(pid, -1, ns) > 0 - is pid is reachable from ns? > translate_pid(1, ns1, ns2) > 0 - is ns1 inside ns2? > translate_pid(1, ns1, ns2) == 0 - is ns1 outside ns2? > translate_pid(1, ns1, ns2) == 1 - is ns1 equal ns2? > > Error codes: > EBADF - file descriptor is closed > EINVAL - file descriptor isn't pid-namespace > ESRCH - task not found in @source namespace Presumably a manpage is planned? This changelog doesn't explain what the value is to our users. I assume it is a performance optimization because "backward translation requires scanning all tasks"? If so, please show us real-world examples of the performance benefit from this patch, and please go to great lengths to explain to us why this optimisation is needed by our users. -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
