[PATCH for-7.4-fixes v4 0/2] cpuset: preparatory fixes and cleanups for partition rework

[Ridong Chen <ridong.chen@linux.dev>]

From: Ridong Chen <chenridong@xiaomi.com>

This series is part of the cpuset local partition rework [1], which I
started while at Huawei and am now continuing at Xiaomi.

Patches 1 and 2 of v3 have been merged into cgroup/for-7.4-fixes. This
version only has the remaining patches 3 and 4 of v3, rebased onto
cgroup/for-7.4-fixes.

Both patches include a bug fix besides the restructuring (Waiman):

  1) settle the isolation state of CPUs given back to the parent in
     partition_xcpus_del(). This fixes the isolated CPU leak reported by
     Guopeng [2], where an isolated partition is invalidated after its
     parent root partition has become invalid and its CPUs are left in
     isolated_cpus.
  2) generalize validate_partition() so it can be used for both local
     and remote partitions. This fixes a false PERR_NOCPUS error when
     expanding a remote partition, where the no CPU left for tasks check
     is done against the cgroup parent instead of top_cpuset.

Patch 2 adds a test case to test_cpuset_prs.sh for the bug it fixes.
test_cpuset_prs.sh passes with this series applied.

[1] https://lore.kernel.org/all/20261101114206.2434398-1-ridong.chen@linux.dev/
[2] https://lore.kernel.org/all/20261105130344.664336-4-guopeng.zhang@linux.dev/

Changes in v4:
  - Drop patches 1 and 2, which have been merged.
  - Rebase onto cgroup/for-7.4-fixes, which includes commit 56681bc448a8
    ("cgroup/cpuset: Correctly set isolated_cpus when switching partition state").
  - Patch 1: describe the isolated CPU leak in the commit message, add
    Fixes, Reported-by and Closes tags (Waiman, Guopeng).
  - Patch 2: describe the remote partition expansion fix in the commit
    message, add a Fixes tag and a test case for it (Waiman).
  - Link to v3: https://lore.kernel.org/all/20261107120100.3587595-1-ridong.chen@linux.dev/

Ridong Chen (2):
  cpuset: settle isolation state when CPUs are given back to parent
  cpuset: generalize the validate_partition() interface

 kernel/cgroup/cpuset.c                        | 217 +++++++-----------
 .../selftests/cgroup/test_cpuset_prs.sh       |   5 +
 2 files changed, 83 insertions(+), 139 deletions(-)


base-commit: 56681bc448a80bb2473026b41c44c133766bc38d
-- 
2.34.1