cgroup: reorganize cgroup_subtree_control_write()
Make the following two reorganizations to
cgroup_subtree_control_write(). These are to prepare for future
changes and shouldn't cause any functional difference.
* Move availability above css offlining wait.
* Move cgrp->child_subsys_mask update above new css creation.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 7868fc3..a46d7e2 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2613,6 +2613,14 @@
continue;
}
+ /* unavailable or not enabled on the parent? */
+ if (!(cgrp_dfl_root.subsys_mask & (1 << ssid)) ||
+ (cgroup_parent(cgrp) &&
+ !(cgroup_parent(cgrp)->child_subsys_mask & (1 << ssid)))) {
+ ret = -ENOENT;
+ goto out_unlock;
+ }
+
/*
* Because css offlining is asynchronous, userland
* might try to re-enable the same controller while
@@ -2635,14 +2643,6 @@
return restart_syscall();
}
-
- /* unavailable or not enabled on the parent? */
- if (!(cgrp_dfl_root.subsys_mask & (1 << ssid)) ||
- (cgroup_parent(cgrp) &&
- !(cgroup_parent(cgrp)->child_subsys_mask & (1 << ssid)))) {
- ret = -ENOENT;
- goto out_unlock;
- }
} else if (disable & (1 << ssid)) {
if (!(cgrp->child_subsys_mask & (1 << ssid))) {
disable &= ~(1 << ssid);
@@ -2673,12 +2673,10 @@
goto out_unlock;
}
- /*
- * Create csses for enables and update child_subsys_mask. This
- * changes cgroup_e_css() results which in turn makes the
- * subsequent cgroup_update_dfl_csses() associate all tasks in the
- * subtree to the updated csses.
- */
+ cgrp->child_subsys_mask |= enable;
+ cgrp->child_subsys_mask &= ~disable;
+
+ /* create new csses */
for_each_subsys(ss, ssid) {
if (!(enable & (1 << ssid)))
continue;
@@ -2690,9 +2688,11 @@
}
}
- cgrp->child_subsys_mask |= enable;
- cgrp->child_subsys_mask &= ~disable;
-
+ /*
+ * At this point, cgroup_e_css() results reflect the new csses
+ * making the following cgroup_update_dfl_csses() properly update
+ * css associations of all tasks in the subtree.
+ */
ret = cgroup_update_dfl_csses(cgrp);
if (ret)
goto err_undo_css;
