Messages in this thread Patch in this message | | | Date | Fri, 20 Oct 2017 10:21:01 -0700 | From | Andrei Vagin <> | Subject | Re: [v6,1/2] pid: Replace pid bitmap implementation with IDR API |
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On Fri, Oct 20, 2017 at 05:06:47PM +0100, Gargi Sharma wrote: > On Thu, Oct 19, 2017 at 5:18 PM, Oleg Nesterov <oleg@redhat.com> wrote: > > On 10/19, Andrei Vagin wrote: > >> > >> Hi Gargi, > >> > >> This patch breaks CRIU, because it changes a meaning of ns_last_pid. > > > > ... > > > >> > @@ -311,7 +297,7 @@ static int pid_ns_ctl_handler(struct ctl_table *table, int write, > >> > * it should synchronize its usage with external means. > >> > */ > >> > > >> > - tmp.data = &pid_ns->last_pid; > >> > + tmp.data = &pid_ns->idr.idr_next; > > > > Ah, yes, off-by-one error... > > > > Gargi, I don't think you need to make another version, I'd suggest you to send > > the trivial fix to Andrew, afaics you just need to replace these 2 lines with > > > > unsigned int last; > > int err; > > > > tmp.data = &last; > > err = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos); > > if (!err) > > idr_set_cursor(&pid_ns->idr, last + 1); > > return err; > I'm not sure entirely understand how this takes care of rolling over of PIDs? > Can we ignore that? If yes, won't the tests for CRIU still break?
Gargi, I don't understand what you mean. Could you elaborate? Do you mean a case when idr_next is bigger than pid_max? I think this logic remains the same what we had before switching to idr.
CRIU tests works with a following patch. It is slightly modified version of Oleg's patch.
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c index fea2c24..1c791b3 100644 --- a/kernel/pid_namespace.c +++ b/kernel/pid_namespace.c @@ -287,6 +287,7 @@ static int pid_ns_ctl_handler(struct ctl_table *table, int write, { struct pid_namespace *pid_ns = task_active_pid_ns(current); struct ctl_table tmp = *table; + int ret; if (write && !ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN)) return -EPERM; @@ -298,7 +299,12 @@ static int pid_ns_ctl_handler(struct ctl_table *table, int write, */ tmp.data = &pid_ns->idr.idr_next; - return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos); + ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos); + if (ret < 0) + return ret; + + idr_set_cursor(&pid_ns->idr, pid_ns->idr.idr_next + 1); + return 0; } extern int pid_max;
> > Thanks, > Gargi > > > > Oleg. > >
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