Commit 1bf67c8f authored by T.J. Mercier's avatar T.J. Mercier Committed by Tejun Heo
Browse files

cgroup/cpuset-v1: Add missing support for cpuset_v2_mode 

Android has mounted the v1 cpuset controller using filesystem type
"cpuset" (not "cgroup") since 2015 [1], and depends on the resulting
behavior where the controller name is not added as a prefix for cgroupfs
files. [2]

Later, a problem was discovered where cpu hotplug onlining did not
affect the cpuset/cpus files, which Android carried an out-of-tree patch
to address for a while. An attempt was made to upstream this patch, but
the recommendation was to use the "cpuset_v2_mode" mount option
instead. [3]

An effort was made to do so, but this fails with "cgroup: Unknown
parameter 'cpuset_v2_mode'" because commit e1cba4b8 ("cgroup: Add
mount flag to enable cpuset to use v2 behavior in v1 cgroup") did not
update the special cased cpuset_mount(), and only the cgroup (v1)
filesystem type was updated.

Add parameter parsing to the cpuset filesystem type so that
cpuset_v2_mode works like the cgroup filesystem type:

$ mkdir /dev/cpuset
$ mount -t cpuset -ocpuset_v2_mode none /dev/cpuset
$ mount|grep cpuset
none on /dev/cpuset type cgroup (rw,relatime,cpuset,noprefix,cpuset_v2_mode,release_agent=/sbin/cpuset_release_agent)

[1] https://cs.android.com/android/_/android/platform/system/core/+/b769c8d24fd7be96f8968aa4c80b669525b930d3
[2] https://cs.android.com/android/platform/superproject/main/+/main:system/core/libprocessgroup/setup/cgroup_map_write.cpp;drc=2dac5d89a0f024a2d0cc46a80ba4ee13472f1681;l=192
[3] https://lore.kernel.org/lkml/f795f8be-a184-408a-0b5a-553d26061385@redhat.com/T/



Fixes: e1cba4b8 ("cgroup: Add mount flag to enable cpuset to use v2 behavior in v1 cgroup")
Signed-off-by: default avatarT.J. Mercier <tjmercier@google.com>
Acked-by: default avatarWaiman Long <longman@redhat.com>
Reviewed-by: default avatarKamalesh Babulal <kamalesh.babulal@oracle.com>
Acked-by: default avatarMichal Koutný <mkoutny@suse.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 87c259a7

kernel/cgroup/cgroup.c

+29 −0
Original line number Diff line number Diff line
@@ -2353,9 +2353,37 @@ static struct file_system_type cgroup2_fs_type = { 
};



#ifdef CONFIG_CPUSETS_V1

enum cpuset_param {

	Opt_cpuset_v2_mode,

};



static const struct fs_parameter_spec cpuset_fs_parameters[] = {

	fsparam_flag  ("cpuset_v2_mode", Opt_cpuset_v2_mode),

	{}

};



static int cpuset_parse_param(struct fs_context *fc, struct fs_parameter *param)

{

	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);

	struct fs_parse_result result;

	int opt;



	opt = fs_parse(fc, cpuset_fs_parameters, param, &result);

	if (opt < 0)

		return opt;



	switch (opt) {

	case Opt_cpuset_v2_mode:

		ctx->flags |= CGRP_ROOT_CPUSET_V2_MODE;

		return 0;

	}

	return -EINVAL;

}



static const struct fs_context_operations cpuset_fs_context_ops = {

	.get_tree	= cgroup1_get_tree,

	.free		= cgroup_fs_context_free,

	.parse_param	= cpuset_parse_param,

};



/*
@@ -2392,6 +2420,7 @@ static int cpuset_init_fs_context(struct fs_context *fc) 
static struct file_system_type cpuset_fs_type = {

	.name			= "cpuset",

	.init_fs_context	= cpuset_init_fs_context,

	.parameters		= cpuset_fs_parameters,

	.fs_flags		= FS_USERNS_MOUNT,

};

#endif