[PATCH] cgroup/cpuset: Mark memory_spread_slab as obsolete

[Xiongwei Song]

We've removed the SLAB allocator, cpuset_do_slab_mem_spread() and
SLAB_MEM_SPREAD, memory_spread_slab is a no-op now. We can mark
memory_spread_slab as obsolete in case someone still wants to use it after
cpuset_do_slab_mem_spread() removed. For more details, please check [1].

[1] https://lore.kernel.org/lkml/32bc1403-49da-445a-8c00-9686a3b0d6a3@xxxxxxxxxx/T/#m8e292e21b00f95a4bb8086371fa7387fa4ea8f60

tj: Description and cosmetic updates.

Signed-off-by: Xiongwei Song <xiongwei.song@xxxxxxxxxxxxx>
Acked-by: Waiman Long <longman@xxxxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
---
 Documentation/admin-guide/cgroup-v1/cpusets.rst | 2 +-
 kernel/cgroup/cpuset.c                          | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/cgroup-v1/cpusets.rst b/Documentation/admin-guide/cgroup-v1/cpusets.rst
index ae646d621a8a..7d3415eea05d 100644
--- a/Documentation/admin-guide/cgroup-v1/cpusets.rst
+++ b/Documentation/admin-guide/cgroup-v1/cpusets.rst
@@ -179,7 +179,7 @@ containing (on top of the standard cgroup files) the following
  - cpuset.mem_hardwall flag:  is memory allocation hardwalled
  - cpuset.memory_pressure: measure of how much paging pressure in cpuset
  - cpuset.memory_spread_page flag: if set, spread page cache evenly on allowed nodes
- - cpuset.memory_spread_slab flag: if set, spread slab cache evenly on allowed nodes
+ - cpuset.memory_spread_slab flag: OBSOLETE. Doesn't have any function.
  - cpuset.sched_load_balance flag: if set, load balance within CPUs on that cpuset
  - cpuset.sched_relax_domain_level: the searching range when migrating tasks
 
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index ba36c073304a..c940cf01b148 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -3897,6 +3897,7 @@ static struct cftype legacy_files[] = {
 	},
 
 	{
+		/* obsolete, may be removed in the future */
 		.name = "memory_spread_slab",
 		.read_u64 = cpuset_read_u64,
 		.write_u64 = cpuset_write_u64,
-- 
2.43.2