The newly introduced cpuset_can_fork() and cpuset_cancel_fork() calls
are only needed when the CLONE_INTO_CGROUP flag is set which is not
likely. Adding an extra cpuset_can_fork() call does introduce a bit
of performance overhead in the fork/clone fastpath. To reduce this
performance overhead, introduce a new clone_into_cgroup_can_fork flag
into the cgroup_subsys structure. This flag, when set, will call the
can_fork and cancel_fork methods only if the CLONE_INTO_CGROUP flag
is set.
The cpuset code is now modified to set this flag. The same cpuset
checking code in cpuset_can_fork() and cpuset_cancel_fork() will have
to stay as the cgroups can be different, but the cpusets may still be
the same. So the same check must be present in both cpuset_fork() and
cpuset_can_fork() to make sure that attach_in_progress is correctly set.
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
---
include/linux/cgroup-defs.h | 6 ++++++
kernel/cgroup/cgroup.c | 23 ++++++++++++++++++-----
kernel/cgroup/cpuset.c | 1 +
3 files changed, 25 insertions(+), 5 deletions(-)
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 8a0d5466c7be..0087a47d80a2 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -701,6 +701,12 @@ struct cgroup_subsys {
*/
bool threaded:1;
+ /*
+ * If %true, the controller will call can_fork and cancel_fork
+ * methods only if CLONE_INTO_CGROUP flag is set.
+ */
+ bool clone_into_cgroup_can_fork:1;
+
/* the following two fields are initialized automatically during boot */
int id;
const char *name;
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 83ea13f2ccb1..23701e959ef5 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -6517,6 +6517,10 @@ int cgroup_can_fork(struct task_struct *child, struct kernel_clone_args *kargs)
return ret;
do_each_subsys_mask(ss, i, have_canfork_callback) {
+ if (ss->clone_into_cgroup_can_fork &&
+ !(kargs->flags & CLONE_INTO_CGROUP))
+ continue;
+
ret = ss->can_fork(child, kargs->cset);
if (ret)
goto out_revert;
@@ -6528,8 +6532,12 @@ int cgroup_can_fork(struct task_struct *child, struct kernel_clone_args *kargs)
for_each_subsys(ss, j) {
if (j >= i)
break;
- if (ss->cancel_fork)
- ss->cancel_fork(child, kargs->cset);
+ if (!ss->cancel_fork ||
+ (ss->clone_into_cgroup_can_fork &&
+ !(kargs->flags & CLONE_INTO_CGROUP)))
+ continue;
+
+ ss->cancel_fork(child, kargs->cset);
}
cgroup_css_set_put_fork(kargs);
@@ -6552,9 +6560,14 @@ void cgroup_cancel_fork(struct task_struct *child,
struct cgroup_subsys *ss;
int i;
- for_each_subsys(ss, i)
- if (ss->cancel_fork)
- ss->cancel_fork(child, kargs->cset);
+ for_each_subsys(ss, i) {
+ if (!ss->cancel_fork ||
+ (ss->clone_into_cgroup_can_fork &&
+ !(kargs->flags & CLONE_INTO_CGROUP)))
+ continue;
+
+ ss->cancel_fork(child, kargs->cset);
+ }
cgroup_css_set_put_fork(kargs);
}
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index e4ca2dd2b764..937ef4d60cd4 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -3391,6 +3391,7 @@ struct cgroup_subsys cpuset_cgrp_subsys = {
.dfl_cftypes = dfl_files,
.early_init = true,
.threaded = true,
+ .clone_into_cgroup_can_fork = true,
};
/**
--
2.31.1
