[RFC PATCH] locks: Show only file_locks created in the same pidns as current process

[Nikolay Borisov <kernel-6AxghH7DbtA@public.gmane.org>]

Currently when /proc/locks is read it will show all the file locks
which are currently created on the machine. On containers, hosted
on busy servers this means that doing lsof can be very slow. I
observed up to 5 seconds stalls reading 50k locks, while the container
itself had only a small number of relevant entries. Fix it by
filtering the locks listed by the pidns of the current process
and the process which created the lock.

Signed-off-by: Nikolay Borisov <kernel-6AxghH7DbtA@public.gmane.org>
---
 fs/locks.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/locks.c b/fs/locks.c
index 6333263b7bc8..53e96df4c583 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -2615,9 +2615,17 @@ static int locks_show(struct seq_file *f, void *v)
 {
 	struct locks_iterator *iter = f->private;
 	struct file_lock *fl, *bfl;
+	struct pid_namespace *pid_ns = task_active_pid_ns(current);
+
 
 	fl = hlist_entry(v, struct file_lock, fl_link);
 
+	pr_info ("Current pid_ns: %p init_pid_ns: %p, fl->fl_nspid: %p nspidof:%p\n", pid_ns, &init_pid_ns,
+		 fl->fl_nspid, ns_of_pid(fl->fl_nspid));
+	if ((pid_ns != &init_pid_ns) && fl->fl_nspid &&
+		(pid_ns != ns_of_pid(fl->fl_nspid)))
+		    return 0;
+
 	lock_get_status(f, fl, iter->li_pos, "");
 
 	list_for_each_entry(bfl, &fl->fl_block, fl_block)
-- 
2.5.0