On Fri, Aug 05, 2016 at 06:47:16AM -0400, Jeff Layton wrote:
> On Fri, 2016-08-05 at 10:30 +0300, Nikolay Borisov wrote:
> > 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@xxxxxxxx>
> > > Suggested-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
> > ---
> > fs/locks.c | 20 +++++++++++++++++---
> > 1 file changed, 17 insertions(+), 3 deletions(-)
> >
> > diff --git a/fs/locks.c b/fs/locks.c
> > index ee1b15f6fc13..484b7e106076 100644
> > --- a/fs/locks.c
> > +++ b/fs/locks.c
> > @@ -2574,9 +2574,19 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
> > > struct inode *inode = NULL;
> > > unsigned int fl_pid;
> >
> > > - if (fl->fl_nspid)
> > > - fl_pid = pid_vnr(fl->fl_nspid);
> > > - else
> > > + if (fl->fl_nspid) {
> > > + struct pid_namespace *proc_pidns = file_inode(f->file)->i_sb->s_fs_info;
> > +
> > > + /* Don't let fl_pid change depending on who is reading the file */
> > > + fl_pid = pid_nr_ns(fl->fl_nspid, proc_pidns);
> > +
> > > + /* If there isn't a fl_pid don't display who is waiting on the lock
> > > + * if we are called from locks_show, or if we are called from
> > > + * __show_fd_info - skip lock entirely
> > > + */
> > > + if (fl_pid == 0)
> > > + return;
> > > + } else
> > > fl_pid = fl->fl_pid;
> >
> > > if (fl->fl_file != NULL)
> > @@ -2648,9 +2658,13 @@ 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 (fl->fl_nspid && !pid_nr_ns(fl->fl_nspid, proc_pidns))
> > > + return 0;
> > +
> > > lock_get_status(f, fl, iter->li_pos, "");
> >
> > > list_for_each_entry(bfl, &fl->fl_block, fl_block)
>
> Looks good to me. I'll go ahead and merge this into my locks branch for
> v4.9 and get it into -next.
Makes sense to me. Thanks also to Eric for the help.
--b.
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