Hello Michael,
On Wed, Jan 10, 2018 at 05:23:32AM +0100, Michael Kerrisk (man-pages) wrote:
> Hello Roman,
>
> On 8 January 2018 at 22:11, Michael Kerrisk (man-pages)
> <mtk.manpages@xxxxxxxxx> wrote:
> > Hello Roman,
> >
> > I wrote cgroups(7) text below to document the files added by you in
> > Linux 4.15. Could you let me know if the following text is okay please:
> >
> > /sys/kernel/cgroup files
> > /sys/kernel/cgroup/delegate (since Linux 4.15)
> > This file exports a list of the cgroups v2 files (one per
> > line) that are delegatable (i.e., whose ownership should be
> > changed to the user ID of the delegatee). In the future,
> > the set of delegatable files may change or grow, and this
> > file provides a way for the kernel to inform user-space
> > applications of which files must be delegated. As at Linux
> > 4.15, one sees the following when inspecting this file:
> >
> > $ cat /sys/kernel/cgroup/delegate
> > cgroup.procs
> > cgroup.subtree_control
>
> I have a question about /sys/kernel/cgroup/delegate: why does this
> file not list cgroup.threads, since that is also a file that
> (potentially) should be delegated?
cc Tejun
cgroup.threads is not listed because it's not delegatable (doesn't have
CFTYPE_NS_DELEGATABLE flag set). I don't know if it was intended or just
an accident (I believe the latter).
Thanks!
PS In the latter case the following patch should fix it:
>From fdf19edb6e9594e48e89d4510767b9eb6ca2d9dd Mon Sep 17 00:00:00 2001
From: Roman Gushchin <guro@xxxxxx>
Date: Wed, 10 Jan 2018 04:35:12 -0800
Subject: [PATCH] cgroup: make cgroup.threads delegatable
Make cgroup.threads file delegatable.
The behavior of cgroup.threads should follow the behavior of cgroup.procs.
Signed-off-by: Roman Gushchin <guro@xxxxxx>
Discovered-by: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
---
kernel/cgroup/cgroup.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 0b1ffe147f24..b74d9ee1425c 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -4449,6 +4449,7 @@ static struct cftype cgroup_base_files[] = {
},
{
.name = "cgroup.threads",
+ .flags = CFTYPE_NS_DELEGATABLE,
.release = cgroup_procs_release,
.seq_start = cgroup_threads_start,
.seq_next = cgroup_procs_next,
--
2.14.3
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