Commit c808f463 authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: remove "no" prefixed mount options 



30312730 ("cgroup: Add "no" prefixed mount options") added "no" prefixed
mount options to allow turning them off and 6a010a49 ("cgroup: Make
!percpu threadgroup_rwsem operations optional") added one more "no" prefixed
mount option. However, Michal pointed out that the "no" prefixed options
aren't necessary in allowing mount options to be turned off:

  # grep group /proc/mounts
  cgroup2 /sys/fs/cgroup cgroup2 rw,nosuid,nodev,relatime,nsdelegate,memory_recursiveprot 0 0
  # mount -o remount,nsdelegate,memory_recursiveprot none /sys/fs/cgroup
  # grep cgroup /proc/mounts
  cgroup2 /sys/fs/cgroup cgroup2 rw,relatime,nsdelegate,memory_recursiveprot 0 0

Note that this is different from the remount behavior when the mount(1) is
invoked without the device argument - "none":

 # grep cgroup /proc/mounts
 cgroup2 /sys/fs/cgroup cgroup2 rw,nosuid,nodev,noexec,relatime,nsdelegate,memory_recursiveprot 0 0
 # mount -o remount,nsdelegate,memory_recursiveprot /sys/fs/cgroup
 # grep cgroup /proc/mounts
 cgroup2 /sys/fs/cgroup cgroup2 rw,nosuid,nodev,noexec,relatime,nsdelegate,memory_recursiveprot 0 0

While a bit confusing, given that there is a way to turn off the options,
there's no reason to have the explicit "no" prefixed options. Let's remove
them.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Michal Koutný <mkoutny@suse.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 6a010a49

Documentation/admin-guide/cgroup-v2.rst

+4 −4
Original line number Diff line number Diff line
@@ -177,14 +177,14 @@ disabling controllers in v1 and make them always available in v2. 


cgroup v2 currently supports the following mount options.



  [no]nsdelegate

  nsdelegate

	Consider cgroup namespaces as delegation boundaries.  This

	option is system wide and can only be set on mount or modified

	through remount from the init namespace.  The mount option is

	ignored on non-init namespace mounts.  Please refer to the

	Delegation section for details.



  [no]favordynmods

  favordynmods

        Reduce the latencies of dynamic cgroup modifications such as

        task migrations and controller on/offs at the cost of making

        hot path operations such as forks and exits more expensive.
@@ -192,7 +192,7 @@ cgroup v2 currently supports the following mount options. 
        controllers, and then seeding it with CLONE_INTO_CGROUP is

        not affected by this option.



  memory_[no]localevents

  memory_localevents

        Only populate memory.events with data for the current cgroup,

        and not any subtrees. This is legacy behaviour, the default

        behaviour without this option is to include subtree counts.
@@ -200,7 +200,7 @@ cgroup v2 currently supports the following mount options. 
        modified through remount from the init namespace. The mount

        option is ignored on non-init namespace mounts.



  memory_[no]recursiveprot

  memory_recursiveprot

        Recursively apply memory.min and memory.low protection to

        entire subtrees, without requiring explicit downward

        propagation into leaf cgroups.  This allows protecting entire

kernel/cgroup/cgroup.c

+4 −20
Original line number Diff line number Diff line
@@ -1872,22 +1872,18 @@ int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node, 
}



enum cgroup2_param {

	Opt_nsdelegate, Opt_nonsdelegate,

	Opt_favordynmods, Opt_nofavordynmods,

	Opt_memory_localevents, Opt_memory_nolocalevents,

	Opt_memory_recursiveprot, Opt_memory_norecursiveprot,

	Opt_nsdelegate,

	Opt_favordynmods,

	Opt_memory_localevents,

	Opt_memory_recursiveprot,

	nr__cgroup2_params

};



static const struct fs_parameter_spec cgroup2_fs_parameters[] = {

	fsparam_flag("nsdelegate",		Opt_nsdelegate),

	fsparam_flag("nonsdelegate",		Opt_nonsdelegate),

	fsparam_flag("favordynmods",		Opt_favordynmods),

	fsparam_flag("nofavordynmods",		Opt_nofavordynmods),

	fsparam_flag("memory_localevents",	Opt_memory_localevents),

	fsparam_flag("memory_nolocalevents",	Opt_memory_nolocalevents),

	fsparam_flag("memory_recursiveprot",	Opt_memory_recursiveprot),

	fsparam_flag("memory_norecursiveprot",	Opt_memory_norecursiveprot),

	{}

};
@@ -1905,27 +1901,15 @@ static int cgroup2_parse_param(struct fs_context *fc, struct fs_parameter *param 
	case Opt_nsdelegate:

		ctx->flags |= CGRP_ROOT_NS_DELEGATE;

		return 0;

	case Opt_nonsdelegate:

		ctx->flags &= ~CGRP_ROOT_NS_DELEGATE;

		return 0;

	case Opt_favordynmods:

		ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS;

		return 0;

	case Opt_nofavordynmods:

		ctx->flags &= ~CGRP_ROOT_FAVOR_DYNMODS;

		return 0;

	case Opt_memory_localevents:

		ctx->flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS;

		return 0;

	case Opt_memory_nolocalevents:

		ctx->flags &= ~CGRP_ROOT_MEMORY_LOCAL_EVENTS;

		return 0;

	case Opt_memory_recursiveprot:

		ctx->flags |= CGRP_ROOT_MEMORY_RECURSIVE_PROT;

		return 0;

	case Opt_memory_norecursiveprot:

		ctx->flags &= ~CGRP_ROOT_MEMORY_RECURSIVE_PROT;

		return 0;

	}

	return -EINVAL;

}