cgroup/cpuset: Fix incorrect CPU accounting with parent's effective_xcpus expansion

Commit ec0254b9eb49 ("cgroup/cpuset: Release invalid isolated CPUs with
a shrunk root partition parent") fixes incorrect isolated_cpus accounting
when contraction of a parent's effective_xcpus can cause a child partition
to lose isolated CPUs. Expansion of parent's effective_cpus can also allow
a child partition to gain more effective_xcpus. However, the current code
doesn't handle this case correctly leading to incorrect effective_cpus
and isolated_cpus accounting. Fix that by looking for this possible
expansion of effective_xcpus and perform the proper accounting action.

New test cases are added to test this effective_xcpus expansion scenarios.

Reported-by: Guopeng Zhang <guopeng.zhang@linux.dev>
Link: https://lore.kernel.org/lkml/20261027123837.100909-1-guopeng.zhang@linux.dev
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
Tested-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
Signed-off-by: Tejun Heo <tj@kernel.org>

0 files changed, 0 insertions, 0 deletions