cgroup/cpuset: Mark memory_spread_slab as obsolete

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@redhat.com/T/#m8e292e21b00f95a4bb8086371fa7387fa4ea8f60

tj: Description and cosmetic updates.

Signed-off-by: Xiongwei Song <xiongwei.song@windriver.com>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

docs: cgroup-v1/cpusets: update libcgroup project link

Update the libcgroup project link, in the cgroup v1/cpusets
documentation.

Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

mm/doc: editorial pass on page migration

Add Sphinx reference links to HMM and CPUSETS, and numerous small
editorial changes to make the page_migration.rst document more readable.

Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20200902225247.15213-1-rcampbell@nvidia.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs: cgroup-v1: Document the cpuset_v2_mode mount option

The cpuset in cgroup v1 accepts a special "cpuset_v2_mode" mount
option that make cpuset.cpus and cpuset.mems behave more like those in
cgroup v2. Document it to make other people more aware of this feature
that can be useful in some circumstances.

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

docs: cgroup-v1: add it to the admin-guide book

Those files belong to the admin guide, so add them.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>