Commit 9b81d3a5 authored by Luiz Capitulino's avatar Luiz Capitulino Committed by Tejun Heo
Browse files

cgroup: add cgroup_favordynmods= command-line option 



We have a need of using favordynmods with cgroup v1, which doesn't support
changing mount flags during remount. Enabling CONFIG_CGROUP_FAVOR_DYNMODS at
build-time is not an option because we want to be able to selectively
enable it for certain systems.

This commit addresses this by introducing the cgroup_favordynmods=
command-line option. This option works for both cgroup v1 and v2 and also
allows for disabling favorynmods when the kernel built with
CONFIG_CGROUP_FAVOR_DYNMODS=y.

Also, note that when cgroup_favordynmods=true favordynmods is never
disabled in cgroup_destroy_root().

Signed-off-by: default avatarLuiz Capitulino <luizcap@amazon.com>
Reviewed-by: default avatarMichal Koutný <mkoutny@suse.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 105f3fe9

Documentation/admin-guide/kernel-parameters.txt

+4 −0
Original line number Diff line number Diff line
@@ -580,6 +580,10 @@ 
			named mounts. Specifying both "all" and "named" disables

			all v1 hierarchies.



	cgroup_favordynmods= [KNL] Enable or Disable favordynmods.

			Format: { "true" | "false" }

			Defaults to the value of CONFIG_CGROUP_FAVOR_DYNMODS.



	cgroup.memory=	[KNL] Pass options to the cgroup memory controller.

			Format: <string>

			nosocket -- Disable socket memory accounting.

kernel/cgroup/cgroup.c

+14 −4
Original line number Diff line number Diff line
@@ -207,6 +207,8 @@ static u16 have_exit_callback __read_mostly; 
static u16 have_release_callback __read_mostly;

static u16 have_canfork_callback __read_mostly;



static bool have_favordynmods __ro_after_init = IS_ENABLED(CONFIG_CGROUP_FAVOR_DYNMODS);



/* cgroup namespace for init task */

struct cgroup_namespace init_cgroup_ns = {

	.ns.count	= REFCOUNT_INIT(2),
@@ -1350,7 +1352,9 @@ static void cgroup_destroy_root(struct cgroup_root *root) 
		cgroup_root_count--;

	}



	if (!have_favordynmods)

		cgroup_favor_dynmods(root, false);



	cgroup_exit_root_id(root);



	cgroup_unlock();
@@ -2245,9 +2249,9 @@ static int cgroup_init_fs_context(struct fs_context *fc) 
	fc->user_ns = get_user_ns(ctx->ns->user_ns);

	fc->global = true;



#ifdef CONFIG_CGROUP_FAVOR_DYNMODS

	if (have_favordynmods)

		ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS;

#endif



	return 0;

}
@@ -6766,6 +6770,12 @@ static int __init enable_cgroup_debug(char *str) 
}

__setup("cgroup_debug", enable_cgroup_debug);



static int __init cgroup_favordynmods_setup(char *str)

{

	return (kstrtobool(str, &have_favordynmods) == 0);

}

__setup("cgroup_favordynmods=", cgroup_favordynmods_setup);



/**

 * css_tryget_online_from_dir - get corresponding css from a cgroup dentry

 * @dentry: directory dentry of interest