Dave Hansen <[EMAIL PROTECTED]> writes: > I was tracking down why we need find_get_pid(1) in > proc_get_sb(), when I realized that we apparently > don't need a pid at all in the non-pid parts of /proc. > > Anyone see any problems with this approach?
The thing is these are pid related parts of /proc you are working with. I'm trying to remember what the actual semantics were. I do know doing this means if our pid namespace goes away these functions do the right thing. This may have been how I was getting the pid namespace in originally so this code may be obsolete. Partly I think doing this made the code a little more symmetric. Regardless I would like to see a little farther down on how we test to see if the pid namespace is alive and how we make these functions do nothing if it has died. I would also like to see how we perform the appropriate lookups by pid namespace. Basically I want to see how we finish up multiple namespace support for /proc before we start with the micro optimizations. I'm fairly certain this patch causes us to do the wrong thing when the pid namespace exits, and I don't see much gain except for the death of find_get_pid. > For what I would imagine are historical reasons, we set > all struct proc_inode->pid fields. We use the init > process for all non-/proc/<pid> inodes. > > We get a handle to the init process in proc_get_sb() > then fetch it out in proc_pid_readdir(): > > struct task_struct *reaper = > get_proc_task(filp->f_path.dentry->d_inode); > > The filp in that case is always the root inode on which > someone is doing a readdir. This reaper variable gets > passed down into proc_base_instantiate() and eventually > set in the new inode's ->pid field. > > The problem is that I don't see anywhere that we > actually go and use this, outside of the /proc/<pid> > directories. Just referencing the init process like > this is a pain for containers because our init process > (pid == 1) can actually go away. Which as far as can recall is part of the point. If you have a pid namespace with normal semantics the child reaper pid == 1 is the last pid in the pid namespace to exit. Therefore when it exists the pid namespace exists and with it doesn't the pid namespace does not exist. Eric _______________________________________________ Containers mailing list [EMAIL PROTECTED] https://lists.linux-foundation.org/mailman/listinfo/containers _______________________________________________ Devel mailing list Devel@openvz.org https://openvz.org/mailman/listinfo/devel
