Hi, On Fri, Jul 25, 2014 at 05:34:43PM +0000, Serge Hallyn wrote: > Quoting chenhanxiao@xxxxxxxxxxxxxx (chenhanxiao@xxxxxxxxxxxxxx): > > Hi, > > > > > -----Original Message----- > > > From: Serge Hallyn [mailto:serge.hallyn@xxxxxxxxxx] > > > Sent: Tuesday, July 15, 2014 12:16 PM > > > To: Chen, Hanxiao/陈 晗霄 > > > Subject: Re: [RFC]Pid conversion between pid namespace > > > > A-2) syscall pid_t getnspid(pid_t query_pid, pid_t observer_pid) > > > > pros: > > > > - ns procfs free, easy to use. > > > > We could get rid of mounted ns procfs. > > > > > > > > cons: > > > > - may find multiple results in nested ns. > > > > We wished the new API could tell us the exact answer. > > > > But if getnspid return more than one results will bring trouble to admins, > > > > > > (See below for more, but) the question being posed to getnspid has precisely > > > one answer. > > > > > > > they had to make another decision. > > > > Or we marked the deepest level for translation as prerequisite. > > > > > > > > -based on current pidns, no reference ns. > > > > > > Hm, no. The intent here was that > > > > > > observer_pid would be in current ns > > > query_pid would be in observer_pid's ns. > > > > > > So this would be ideal for "I got a pid in a logfile created by rsyslog in > > > a nested contaner, what is the logged pid in my pidns." > > > > > > Taking a set of tasks (like a container with nesting) and bulding a tree > > > of all pids shouldn't be too difficult either. Start with the init pid, > > > call getnspid($pid, $init_pid) for every $pid in the container; to figure > > > out whether any $pid is itself a nested init_pid, we can compare the > > > /proc/$$/ns/pid, as well as look at getnspid($pid, $pid). > > I'm a little confused in this section: > > > > Ex: > > init_pid_ns ns1 ns2 > > t1 2 > > t2 `- 3 1 > > t3 `- 4 `- 5 1 > > t4 `-6 `-8 `-9 > > t5 `-10 `-9 `-10 > > > > For getnspid($pid, $init_pid), > > Does init_pid means container's init_pid such as 3 for t2? > > Right, if you're in init_pid_ns and making the query, then > you'd pass 3. Sorry for jumping in, but I'm not quite understanding the purpose of $init_pid here, does it identify the ns which the process to be queried is in? Also see my questions below: 1. Given the example above, what's the return of getnspid(9, 3)? Is it 6(task t4) or 10(task t5)? 2. if there is a process in ns1 which is a child of process 1 has pid 10, but not in ns2, like below: init_pid_ns ns1 ns2 t1 2 t2 `- 3 1 t3 `- 4 +- 5 1 t4 `-6 | `-8 `-9 t5 `-10 | `-9 `-10 t6 `-11 `-10 then what is the return of getnspid(10, 3)? Regards, Hu > > > > In nested containers, does this syscall work as: > > getnspid(9, 4) -> (6, 8, 9) > > No, assuming the querying task is in init_pid_ns, > getnspid(9, 4) would return 6. > > 4 is the observer pid given in the querier's own pidns, so > it refers to t3. 9 is the pid being queried, in the oberver's > pidns, so it revers to t4. The result is, the pid in our own > pidns. > > Does that help clarify at all? I'm not sure whether the problem is that > I didn't explain well enough from the start, or whether this just shows > that the API is one only its mother could love :) > > -serge > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
