Hi > -----Original Message----- > From: Richard Weinberger [mailto:richard@xxxxxx] > Sent: Friday, June 20, 2014 7:02 PM > To: Chen, Hanxiao/陈 晗霄; containers@xxxxxxxxxxxxxxxxxxxxxxxxxx; > linux-kernel@xxxxxxxxxxxxxxx > Cc: Eric W. Biederman; Serge Hallyn; Daniel P. Berrange; Oleg Nesterov; Al Viro; > David Howells; Pavel Emelyanov; Vasiliy Kulikov; Gotou, Yasunori/五? 康文; > linux-api@xxxxxxxxxxxxxxx > Subject: Re: [PATCH v2] ns: introduce getnspid syscall > > Am 20.06.2014 12:18, schrieb Chen Hanxiao: > > We need a direct method of getting the pid inside containers. > > If some issues occurred inside container guest, host user > > could not know which process is in trouble just by guest pid: > > the users of container guest only knew the pid inside containers. > > This will bring obstacle for trouble shooting. > > > > int getnspid(pid_t pid, int fd1, int fd2); > > > > pid: the pid number need to be translated. > > > > fd: a file descriptor referring to one of > > the namespace entries in a /proc/[pid]/ns/pid. > > fd1 for destination ns(ns1), where the pid came from. > > fd2 for reference ns(ns2), while fd2 = -2 means for current ns. > > > > return value: > > >0 : translated pid in ns1(fd1) seen from ns2(fd2). > > <=0: on failure. > > > > I don't think that adding a new system call for this is a good solution. > We need a more generic way. I bet people are interested in more than just PID > numbers. Could you please give some hints on how to expand this interface? > > I agree with Eric that a procfs solution is more appropriate. > Procfs is a good solution, but syscall is not bad though. Procfs works for me, but that seems could not fit Pavel's requirement. His opinion is that a syscall is a more generic interface than proc files, and also very helpful. And syscall could tell whether a pid lives in a specific pid namespace, much convenient than procfs. Thanks, - Chen
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