mm/mempolicy: fix memory leaks in weighted interleave sysfs

mm/mempolicy: fix memory leaks in weighted interleave sysfs

Patch series "Enhance sysfs handling for memory hotplug in weighted
interleave", v9.

The following patch series enhances the weighted interleave policy in the
memory management subsystem by improving sysfs handling, fixing memory
leaks, and introducing dynamic sysfs updates for memory hotplug support.

This patch (of 3):

Memory leaks occurred when removing sysfs attributes for weighted
interleave.  Improper kobject deallocation led to unreleased memory when
initialization failed or when nodes were removed.

The risk of leak is low because it only appears to trigger if setup
fails.  Setup only fails due to -ENOMEM which is unlikely to happen
from a late_initcall() when memory pressure is low.

This patch resolves the issue by replacing unnecessary `kfree()` calls
with proper `kobject_del()` and `kobject_put()` sequences, ensuring
correct teardown and preventing memory leaks.

By explicitly calling `kobject_del()` before `kobject_put()`, the release
function is now invoked safely, and internal sysfs state is correctly
cleaned up.  This guarantees that the memory associated with the kobject
is fully released and avoids resource leaks, thereby improving system
stability.

Additionally, sysfs_remove_file() is no longer called from the release
function to avoid accessing invalid sysfs state after kobject_del().  All
attribute removals are now done before kobject_del(), preventing WARN_ON()
in kernfs and ensuring safe and consistent cleanup of sysfs entries.

Link: https://lkml.kernel.org/r/20250417072839.711-1-rakie.kim@sk.com
Link: https://lkml.kernel.org/r/20250417072839.711-2-rakie.kim@sk.com
Fixes: dce41f5ae253 ("mm/mempolicy: implement the sysfs-based weighted_interleave interface")
Signed-off-by: Rakie Kim <rakie.kim@sk.com>
Reviewed-by: Gregory Price <gourry@gourry.net>
Reviewed-by: Joshua Hahn <joshua.hahnjy@gmail.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Honggyu Kim <honggyu.kim@sk.com>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Yunjeong Mun <yunjeong.mun@sk.com>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>