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    SubjectRe: [PATCH 2/2] Replace pid_t in autofs with struct pid reference
    Quoting Ian Kent (raven@themaw.net):
    > On Wed, 2007-03-21 at 21:19 -0500, Serge E. Hallyn wrote:
    > > Quoting Ian Kent (raven@themaw.net):
    > > > On Tue, 2007-03-20 at 16:01 -0600, Eric W. Biederman wrote:
    > > > > "Serge E. Hallyn" <serue@us.ibm.com> writes:
    > > > >
    > > > > >> > void autofs4_dentry_release(struct dentry *);
    > > > > >> > extern void autofs4_kill_sb(struct super_block *);
    > > > > >> > diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
    > > > > >> > index 9857543..4a9ad9b 100644
    > > > > >> > --- a/fs/autofs4/waitq.c
    > > > > >> > +++ b/fs/autofs4/waitq.c
    > > > > >> > @@ -141,8 +141,8 @@ static void autofs4_notify_daemon(struct
    > > > > >> > packet->ino = wq->ino;
    > > > > >> > packet->uid = wq->uid;
    > > > > >> > packet->gid = wq->gid;
    > > > > >> > - packet->pid = wq->pid;
    > > > > >> > - packet->tgid = wq->tgid;
    > > > > >> > + packet->pid = pid_nr(wq->pid);
    > > > > >> > + packet->tgid = pid_nr(wq->tgid);
    > > > > >> > break;
    > > > > >>
    > > > > >> I'm assuming we build the packet in the process context of the
    > > > > >> daemon we are sending it to. If not we have a problem here.
    > > > > >
    > > > > > Yes this is data being sent to a userspace daemon (Ian pls correct me if
    > > > > > I'm wrong) so the pid_nr is the only thing we can send.
    > > > >
    > > > > Agreed. The question is are we in the user space daemon's process when
    > > > > we generate the pid_nr. Or do we stuff this in some kind of socket,
    > > > > and the socket switch locations of the packet.
    > > >
    > > > The context here is the automount daemon only for expire runs.
    > > >
    > > > Mount request packets are triggered by user processes walking over an
    > > > autofs mount point directory. So "current" in this case isn't the autofs
    > > > daemon.
    > > >
    > > > Requests are sent via a pipe to the daemon.
    > >
    > > So is the pid used for anything other than debugging?
    > >
    > > In any case, here is a replacement patch which sends the pid number
    > > in the pid_namespace of the process which did the autofs4 mount.
    > >
    > > Still not sure whether that is actually what makes sense...
    > >
    > > From: "Serge E. Hallyn" <serue@us.ibm.com>
    > > Subject: [PATCH] autofs: prevent pid wraparound in waitqs
    > >
    > > Instead of storing pid numbers for waitqs, store references
    > > to struct pids. Also store a reference to the mounter's pid
    > > namespace in the autofs4 sb info so that pid numbers for
    > > mount miss and expiry msgs can send the pid# in the mounter's
    > > pidns.
    >
    > I think this amounts to what I suggested in my previous replies.
    > Hopefully my comments are enough to clear up any questions on
    > correctness of this approach.
    >
    > Sorry to be a pain but I'm having a little trouble reviewing the patch
    > because I'm not clear on where the code to handle the automount process
    > group (so called oz_pgrp), from the first patch, fits in with this.

    It also has pidspace infrastructure code in it, so I think we will just
    hold off on this until we have that infrastructure merged into the
    pidspace code and into -mm. Then we can send you a single, more concise
    patch.

    > Is this patch in addition to the original?

    Yes.

    > If so are the references to pid_nr still OK?

    I think so, because AIUI the rest are all executed in a context where
    current is both the actor and recipient.

    Thanks for your help.

    thanks,
    -serge
    -
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