linux-kernel - Re: [PATCH v3 0/1] cpuset: relax the overlap check for cgroup-v2

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4366cedd-b9c7-48de-bb48-f3c4ff81e73e@huaweicloud.com>
Date: Mon, 17 Nov 2025 11:23:36 +0800
From: Chen Ridong <chenridong@...weicloud.com>
To: Sun Shaojie <sunshaojie@...inos.cn>, llong@...hat.com
Cc: mkoutny@...e.com, cgroups@...r.kernel.org, hannes@...xchg.org,
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
 shuah@...nel.org, tj@...nel.org
Subject: Re: [PATCH v3 0/1] cpuset: relax the overlap check for cgroup-v2



On 2025/11/17 9:57, Sun Shaojie wrote:
> In cgroup v2, a mutual overlap check is required when at least one of two
> cpusets is exclusive. However, this check should be relaxed and limited to
> cases where both cpusets are exclusive.
> 
> This patch ensures that for sibling cpusets A1 (exclusive) and B1
> (non-exclusive), change B1 cannot affect A1's exclusivity.
> 
> for example. Assume a machine has 4 CPUs (0-3).
> 
>    root cgroup
>       /    \
>     A1      B1
> 
> Case 1:
>  Table 1.1: Before applying the patch
>  Step                                       | A1's prstate | B1'sprstate |
>  #1> echo "0-1" > A1/cpuset.cpus            | member       | member      |
>  #2> echo "root" > A1/cpuset.cpus.partition | root         | member      |
>  #3> echo "0" > B1/cpuset.cpus              | root invalid | member      |
> 
> After step #3, A1 changes from "root" to "root invalid" because its CPUs
> (0-1) overlap with those requested by B1 (0-3). However, B1 can actually
> use CPUs 2-3(from B1's parent), so it would be more reasonable for A1 to
> remain as "root."
> 
>  Table 1.2: After applying the patch
>  Step                                       | A1's prstate | B1'sprstate |
>  #1> echo "0-1" > A1/cpuset.cpus            | member       | member      |
>  #2> echo "root" > A1/cpuset.cpus.partition | root         | member      |
>  #3> echo "0" > B1/cpuset.cpus              | root         | member      |
> 
> Case 2: (This situation remains unchanged from before)
>  Table 2.1: Before applying the patch
>  Step                                       | A1's prstate | B1'sprstate |
>  #1> echo "0-1" > A1/cpuset.cpus            | member       | member      |
>  #3> echo "1-2" > B1/cpuset.cpus            | member       | member      |
>  #2> echo "root" > A1/cpuset.cpus.partition | root invalid | member      |
> 
>  Table 2.2: After applying the patch
>  Step                                       | A1's prstate | B1'sprstate |
>  #1> echo "0-1" > A1/cpuset.cpus            | member       | member      |
>  #3> echo "1-2" > B1/cpuset.cpus            | member       | member      |
>  #2> echo "root" > A1/cpuset.cpus.partition | root invalid | member      |
> 
> All other cases remain unaffected. For example, cgroup-v1, both A1 and
> B1 are exclusive or non-exlusive.
> 
> ---
> v3 -> v4:
>   - Adjust the test_cpuset_prt.sh test file to align with the current
>     behavior.
> 
> v2 -> v3:
>   - Ensure compliance with constraints such as cpuset.cpus.exclusive.
>   - Link: https://lore.kernel.org/cgroups/20251113131434.606961-1-sunshaojie@kylinos.cn/
> 
> v1 -> v2:
>   - Keeps the current cgroup v1 behavior unchanged
>   - Link: https://lore.kernel.org/cgroups/c8e234f4-2c27-4753-8f39-8ae83197efd3@redhat.com
> 
> ---
>  kernel/cgroup/cpuset-internal.h               |  3 ++
>  kernel/cgroup/cpuset-v1.c                     | 20 +++++++++
>  kernel/cgroup/cpuset.c                        | 43 ++++++++++++++-----
>  .../selftests/cgroup/test_cpuset_prs.sh       |  5 ++-
>  4 files changed, 58 insertions(+), 13 deletions(-)
> 
Is this a cover letter?

The cover letter is labeled as v3, while the patch itself is v4.

For a single patch, I don’t think a cover letter is necessary.

-- 
Best regards,
Ridong