We have a need of using favordynmods with cgroup v1, which doesn't support
changing mount flags during remount. Enabling CONFIG_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_FAVOR_DYNMODS=y.
Signed-off-by: Luiz Capitulino <luizcap@xxxxxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 4 ++++
kernel/cgroup/cgroup.c | 14 +++++++++++---
2 files changed, 15 insertions(+), 3 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 0c38a8af95ce..672f76a3c002 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -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.
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 5fa95f86cb4d..b625825e270b 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -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 __read_mostly = IS_ENABLED(CONFIG_CGROUP_FAVOR_DYNMODS);
+
/* cgroup namespace for init task */
struct cgroup_namespace init_cgroup_ns = {
.ns.count = REFCOUNT_INIT(2),
@@ -2265,9 +2267,9 @@ 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
- ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS;
-#endif
+ if (have_favordynmods)
+ ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS;
+
return 0;
}
@@ -6767,6 +6769,12 @@ 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
--
2.40.1
