cgroup v1 or v2 or both controller names can be passed as arguments to
the 'cgroup_no_v1' kernel parameter, though most of the controller's
names are the same for both cgroup versions. This can be confusing when
both versions are used interchangeably, i.e., passing cgroup_no_v1=io

$ sudo dmesg |grep cgroup
...
cgroup: Disabling io control group subsystem in v1 mounts
cgroup: Disabled controller 'blkio'

Restrict the check to ss->legacy_name only, when parsing the controller
names passed to cgroup_no_v1 parameter and also, use ss->legacy_name in
pr_info(), that prints the controller disabling information.

Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
---
 kernel/cgroup/cgroup-v1.c | 3 +--
 kernel/cgroup/cgroup.c    | 2 +-
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index c487ffef6652..942872b83bf2 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -1297,8 +1297,7 @@ static int __init cgroup_no_v1(char *str)
 		}
 
 		for_each_subsys(ss, i) {
-			if (strcmp(token, ss->name) &&
-			    strcmp(token, ss->legacy_name))
+			if (strcmp(token, ss->legacy_name))
 				continue;
 
 			cgroup_no_v1_mask |= 1 << i;
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 1fb7f562289d..622fb53a806b 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -6121,7 +6121,7 @@ int __init cgroup_init(void)
 
 		if (cgroup1_ssid_disabled(ssid))
 			pr_info("Disabling %s control group subsystem in v1 mounts\n",
-				ss->name);
+				ss->legacy_name);
 
 		cgrp_dfl_root.subsys_mask |= 1 << ss->id;
 

base-commit: 2cf0f715623872823a72e451243bbf555d10d032
-- 
2.41.0

On Wed, Sep 20, 2023 at 03:55:12PM +0530, Kamalesh Babulal wrote:
> cgroup v1 or v2 or both controller names can be passed as arguments to
> the 'cgroup_no_v1' kernel parameter, though most of the controller's
> names are the same for both cgroup versions. This can be confusing when
> both versions are used interchangeably, i.e., passing cgroup_no_v1=io
> 
> $ sudo dmesg |grep cgroup
> ...
> cgroup: Disabling io control group subsystem in v1 mounts
> cgroup: Disabled controller 'blkio'

So, making the printed names consistent makes sense but I'm not sure about
not matching "io" anymore. That's gonna break users who already use them,
right?

Thanks.

-- 
tejun

On 10/5/23 00:47, Tejun Heo wrote:
> On Wed, Sep 20, 2023 at 03:55:12PM +0530, Kamalesh Babulal wrote:
>> cgroup v1 or v2 or both controller names can be passed as arguments to
>> the 'cgroup_no_v1' kernel parameter, though most of the controller's
>> names are the same for both cgroup versions. This can be confusing when
>> both versions are used interchangeably, i.e., passing cgroup_no_v1=io
>>
>> $ sudo dmesg |grep cgroup
>> ...
>> cgroup: Disabling io control group subsystem in v1 mounts
>> cgroup: Disabled controller 'blkio'
> 
> So, making the printed names consistent makes sense but I'm not sure about
> not matching "io" anymore. That's gonna break users who already use them,
> right?

Agreed, users might pass "io" in place of "blkio", I was thinking
in terms of cgroup v1 users, for whom it is "blkio" controller but
as an argument, "cgroup_no_v1" makes the controllers passed to it,
available under cgroup v2, where the controller is named "io",
which the user may use interchangeably.

Shall I re-send the patch to print the controller legacy_name only?

-- 
Thanks,
Kamalesh

On Thu, Oct 05, 2023 at 04:51:52PM +0530, Kamalesh Babulal wrote:
> 
> 
> On 10/5/23 00:47, Tejun Heo wrote:
> > On Wed, Sep 20, 2023 at 03:55:12PM +0530, Kamalesh Babulal wrote:
> >> cgroup v1 or v2 or both controller names can be passed as arguments to
> >> the 'cgroup_no_v1' kernel parameter, though most of the controller's
> >> names are the same for both cgroup versions. This can be confusing when
> >> both versions are used interchangeably, i.e., passing cgroup_no_v1=io
> >>
> >> $ sudo dmesg |grep cgroup
> >> ...
> >> cgroup: Disabling io control group subsystem in v1 mounts
> >> cgroup: Disabled controller 'blkio'
> > 
> > So, making the printed names consistent makes sense but I'm not sure about
> > not matching "io" anymore. That's gonna break users who already use them,
> > right?
> 
> Agreed, users might pass "io" in place of "blkio", I was thinking
> in terms of cgroup v1 users, for whom it is "blkio" controller but
> as an argument, "cgroup_no_v1" makes the controllers passed to it,
> available under cgroup v2, where the controller is named "io",
> which the user may use interchangeably.
> 
> Shall I re-send the patch to print the controller legacy_name only?

Yes, let's do that.

Thanks.

-- 
tejun