Re: [PATCHv3] locks: Filter /proc/locks output on proc pid ns

[ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org (Eric W. Biederman)]

Nikolay Borisov <kernel-6AxghH7DbtA@public.gmane.org> writes:

> On busy container servers reading /proc/locks shows all the locks
> created by all clients. This can cause large latency spikes. In my
> case I observed lsof taking up to 5-10 seconds while processing around
> 50k locks. Fix this by limiting the locks shown only to those created
> in the same pidns as the one the proc fs was mounted in. When reading
> /proc/locks from the init_pid_ns proc instance then perform no
> filtering
>
> Signed-off-by: Nikolay Borisov <kernel-6AxghH7DbtA@public.gmane.org>
> ---
>  fs/locks.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/fs/locks.c b/fs/locks.c
> index ee1b15f6fc13..65e75810a836 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -2648,9 +2648,14 @@ static int locks_show(struct seq_file *f, void *v)
>  {
>  	struct locks_iterator *iter = f->private;
>  	struct file_lock *fl, *bfl;
> +	struct pid_namespace *proc_pidns = file_inode(f->file)->i_sb->s_fs_info;
>  
>  	fl = hlist_entry(v, struct file_lock, fl_link);
>  
> +	if ((proc_pidns != &init_pid_ns) && fl->fl_nspid
> +	    && (proc_pidns != ns_of_pid(fl->fl_nspid)))
> +		return 0;
> +

With no loss of generality you can simplify this check to:

	if ((fl->fl_ns_pid) && (pid_nr_ns(fl->fl_nspid, prod_pidns)))
        	return 0;

>  	lock_get_status(f, fl, iter->li_pos, "");
>  
>  	list_for_each_entry(bfl, &fl->fl_block, fl_block)


Of course now I am staring at the crazy use of pid_vnr in
lock_get_status.  That should probably be pid_nr_ns(proc_pidns) as well.


Eric