mm/damon/core-test: fix memory leak in damon_new_region()

mm/damon/core-test: fix memory leak in damon_new_region()

Patch series "mm/damon/core-test: Fix memory leaks in core-test", v3.

There are a few memory leaks in core-test which are detected by kmemleak.
This patchset fixes the issues.

This patch (of 2):

When CONFIG_DAMON_KUNIT_TEST=y and making CONFIG_DEBUG_KMEMLEAK=y
and CONFIG_DEBUG_KMEMLEAK_AUTO_SCAN=y, the below memory leak is detected.

The damon_region which is allocated by kmem_cache_alloc() in
damon_new_region() in damon_test_regions() and
damon_test_update_monitoring_result() are not freed.

So for damon_test_regions(), replace damon_del_region() call with
damon_destroy_region() so that it calls both damon_del_region() and
damon_free_region(), the latter will free the damon_region. For
damon_test_update_monitoring_result(), call damon_free_region() to
free it. After applying this patch, the following memory leak is never
detected.

    unreferenced object 0xffff2b49c3edc000 (size 56):
      comm "kunit_try_catch", pid 338, jiffies 4294895280 (age 557.084s)
      hex dump (first 32 bytes):
        01 00 00 00 00 00 00 00 02 00 00 00 00 00 00 00  ................
        00 00 00 00 00 00 00 00 00 00 00 00 49 2b ff ff  ............I+..
      backtrace:
        [<0000000088e71769>] slab_post_alloc_hook+0xb8/0x368
        [<00000000b528f67c>] kmem_cache_alloc+0x168/0x284
        [<000000008603f022>] damon_new_region+0x28/0x54
        [<00000000a3b8c64e>] damon_test_regions+0x38/0x270
        [<00000000559c4801>] kunit_try_run_case+0x50/0xac
        [<000000003932ed49>] kunit_generic_run_threadfn_adapter+0x20/0x2c
        [<000000003c3e9211>] kthread+0x124/0x130
        [<0000000028f85bdd>] ret_from_fork+0x10/0x20
    unreferenced object 0xffff2b49c5b20000 (size 56):
      comm "kunit_try_catch", pid 354, jiffies 4294895304 (age 556.988s)
      hex dump (first 32 bytes):
        03 00 00 00 00 00 00 00 07 00 00 00 00 00 00 00  ................
        00 00 00 00 00 00 00 00 96 00 00 00 49 2b ff ff  ............I+..
      backtrace:
        [<0000000088e71769>] slab_post_alloc_hook+0xb8/0x368
        [<00000000b528f67c>] kmem_cache_alloc+0x168/0x284
        [<000000008603f022>] damon_new_region+0x28/0x54
        [<00000000ca019f80>] damon_test_update_monitoring_result+0x18/0x34
        [<00000000559c4801>] kunit_try_run_case+0x50/0xac
        [<000000003932ed49>] kunit_generic_run_threadfn_adapter+0x20/0x2c
        [<000000003c3e9211>] kthread+0x124/0x130
        [<0000000028f85bdd>] ret_from_fork+0x10/0x20

Link: https://lkml.kernel.org/r/20230918120951.2230468-1-ruanjinjie@huawei.com
Link: https://lkml.kernel.org/r/20230918120951.2230468-2-ruanjinjie@huawei.com
Fixes: 17ccae8bb5c9 ("mm/damon: add kunit tests")
Fixes: f4c978b6594b ("mm/damon/core-test: add a test for damon_update_monitoring_results()")
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendan.higgins@linux.dev>
Cc: Feng Tang <feng.tang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>