From 7fd8c565d8a501486d63d7ee07fd6582e97db437 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Wed, 23 Apr 2014 11:13:16 -0400 Subject: [PATCH] cgroup: update subsystem rebind restrictions Because the default root couldn't have any non-root csses attached to it, rebinding away from it was always allowed; however, the default hierarchy will soon host the unified hierarchy and have non-root csses so the rebind restrictions need to be updated accordingly. Instead of special casing rebinding from the default hierarchy and then checking whether the source hierarchy has children cgroups, which implies non-root csses for !dfl hierarchies, simply check whether the source hierarchy has non-root csses for the subsystem using css_next_child(). Signed-off-by: Tejun Heo Acked-by: Li Zefan --- kernel/cgroup.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index c66bfc8ee8a7..15eb2273d80b 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1051,16 +1051,12 @@ static int rebind_subsystems(struct cgroup_root *dst_root, if (!(ss_mask & (1 << ssid))) continue; - /* if @ss is on the dummy_root, we can always move it */ - if (ss->root == &cgrp_dfl_root) - continue; - - /* if @ss has non-root cgroups attached to it, can't move */ - if (!list_empty(&ss->root->cgrp.children)) + /* if @ss has non-root csses attached to it, can't move */ + if (css_next_child(NULL, cgroup_css(&ss->root->cgrp, ss))) return -EBUSY; /* can't move between two non-dummy roots either */ - if (dst_root != &cgrp_dfl_root) + if (ss->root != &cgrp_dfl_root && dst_root != &cgrp_dfl_root) return -EBUSY; } -- 2.39.2